WO2026003706A1

WO2026003706A1 - Computations for left ventricular assist devices

Info

Publication number: WO2026003706A1
Application number: PCT/IB2025/056384
Authority: WO
Inventors: Avi ROZENFELD; Assaf ZADKA; Gad LUBINSKY
Original assignee: Magenta Medical Ltd
Current assignee: Magenta Medical Ltd
Priority date: 2024-06-24
Filing date: 2025-06-24
Publication date: 2026-01-02
Anticipated expiration: 2026-12-24
Also published as: WO2026003707A2

Abstract

Apparatus and methods are described for use with a left-ventricular assist device (20). A processor (25) is configured to compute respective estimated left ventricular end diastolic pressures for one or more cycles of the heart, by, for each of the cycles: identifying a time t0 at which a speed of a motor (31) was a maximum, and identifying the estimated left ventricular end diastolic pressure for the cycle based on a value of a left ventricular pressure of the subject during an interval [t0-c*D t0], c being a predefined constant and D being a duration of the cycle. The processor (25) displays the estimated left ventricular end diastolic pressures or a statistic thereof, on a display (228). Other applications are also described.

Description

COMPUTATIONS FOR LEFT VENTRICULAR ASSIST DEVICES

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application claims priority from US Provisional Patent Application 63/663,213 to Rozenfeld et al., entitled "Computations for left ventricular assist devices," filed June 24, 2024, which is incorporated herein by reference.

TECHNICAL FIELD

Embodiments of the present disclosure relate generally to the field of medical apparatus, and specifically to computations for facilitating the use of a ventricular assist device.

BACKGROUND

Ventricular assist devices are mechanical circulatory support devices designed to assist and unload cardiac chambers in order to maintain or augment cardiac output. They are used in patients suffering from a failing heart and in patients at risk for deterioration of cardiac function during percutaneous coronary interventions. Most commonly, a left-ventricular assist device is applied to a defective heart in order to assist left-ventricular functioning. In some cases, a right-ventricular assist device is used in order to assist right-ventricular functioning. Such ventricular assist devices are either designed to be permanently implanted or mounted on a catheter for temporary placement.

SUMMARY

In some embodiments of the present disclosure, a left-ventricular assist device is percutaneously inserted into the heart of a subject. The device includes a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through the aorta of the subject, into the left ventricle of the heart such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The device further includes an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pumpoutlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings. The device further includes a delivery tube configured to extend, from outside the body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable. Following the insertion of the device, the motor rotates the impeller so as to pump blood from the left ventricle into the aorta. Typically, the rotation speed of the motor (and of the impeller) varies with the pressure gradient between the left ventricle and the aorta.

Embodiments of the present disclosure further comprise apparatus comprising a processor configured to estimate the pressure gradient between the aorta and the left ventricle, over an interval, while the device is in use. Typically, the estimate is based on a variation, over the interval, in a parameter related to the motor, such as the speed of the motor or the current drawn by the motor, as the motor rotates the impeller. In some embodiments, to facilitate this estimation, the maximal diameter of the impeller is at least 8 mm, such that the variation in the parameter is greater than if the maximal diameter of the impeller were less than 8 mm. Alternatively or additionally, the moment of inertia of the motor is less than 5 kg-m , such that

2 the variation in the parameter is greater than if the moment of inertia were at least 5 kg-m .

In some embodiments, the processor is configured to improve the accuracy of the estimate by performing the estimate differently, depending on whether the aortic valve of the subject is opening during systole. For example, in some embodiments, the processor is configured to compute a preliminary estimated pressure gradient between the aorta and the left ventricle, based on the current consumed by the motor while rotating the impeller. Based on the preliminary estimated pressure gradient, which is indicative of whether the aortic valve is opening, the processor selects either a first adjustment type, which is suitable for cases in which the aortic valve is opening, or a second adjustment type, which is suitable for cases in which the aortic valve is not opening. The processor is further configured to compute a final estimated pressure gradient by adjusting the preliminary estimated pressure gradient per the selected adjustment type, and to display the final estimated pressure gradient or another physiological parameter derived therefrom, such as the left ventricular pressure of the subject.

As noted above, the pump-outlet tube is configured to span the aortic valve of the heart of the subject. In some embodiments, the processor is configured to compute a positional bias of the pump-outlet tube relative to the valve, i.e., the processor is configured to determine whether the pump-outlet tube is properly positioned, positionally biased toward the aorta, or positionally biased toward the left ventricle. In some such embodiments, the processor is further configured to display an indicator having a property indicative of the direction of the bias and a color indicative of the magnitude of the bias.

For example, in some embodiments, the apparatus further comprises a pressure sensor configured to output a signal indicative of the aortic pressure within the aorta over an interval. In addition to computing the estimated pressure gradient between the aorta and the left ventricle over the interval, the processor is configured to identify a minimum of the aortic pressure over the interval, based on the signal. The processor is further configured to compare an indication of the minimum of the aortic pressure to an indication of the peak-to-peak amplitude of the estimated pressure gradient. In response to comparing the indication of the minimum of the aortic pressure to the indication of the peak-to-peak amplitude of the estimated pressure gradient, the processor can output an indication that the pump-outlet tube is positionally biased toward the aorta.

As another example, in some embodiments, the processor is configured to compute an estimated average current consumed by the motor, over an interval, while rotating the impeller, based on the speed of the motor during the interval. The processor is further configured to compare the estimated average current to the actual average current consumed by the motor over the interval. In response to comparing the estimated average current to the actual average current, the processor can display an indication that the pump-outlet tube is positionally biased toward the left ventricle.

As noted above, in some embodiments, the processor is configured to compute, for a first interval, an estimated pressure in the left ventricle based on a parameter related to the motor as the motor rotates the impeller during the first interval. However, for some motors, once the pressure gradient between the aorta and the left ventricle exceeds a particular cutoff, the motor cannot keep the pump-outlet tube open, and the pump-outlet tube at least partly collapses. Due to the collapse of the pump-outlet tube, which impedes the flow of blood through the pump-outlet tube, this estimate is inaccurate.

To address this challenge, in some embodiments, the processor is configured to determine that the pump-outlet tube was at least partly collapsed following the first interval. In response to determining that the pump-outlet tube was at least partly collapsed, the processor computes an adjusted estimate of the pressure for a second interval following the first interval, and displays the estimated pressure and the adjusted estimate of the pressure. Advantageously, the adjusted estimate is continuous with the estimated pressure, such that any user who views the display typically cannot discern that any adjustment has been made. In some applications, in the event that the processor identifies an interval, during at least part of which the pump-outlet tube was at least partly collapsed, the processor drives the display not to display the left ventricular pressure during the interval. In other words, the display is driven to display the left ventricular pressure whenever it can be accurately estimated based on the motor current (e.g., during a first interval, in which the left ventricular pressure whenever it can be accurately estimated based on the motor current). However, during intervals in which at least part of which the pump-outlet tube is at least partly collapsed such that the regular relationship between the motor current and the left ventricular pressure is not applicable (e.g., during a second interval following the first interval), the left ventricular pressure is not displayed. As noted above, in some embodiments, the apparatus comprises a pressure sensor configured to output a signal indicative of the aortic pressure within the aorta. For example, in some embodiments, the left-ventricular assist device further includes a catheter configured to surround the delivery tube within the aorta so as to define a pressuresensing channel between the catheter and the delivery tube. The pressure sensor is configured to output a first signal indicative of the pressure within the pressure-sensing channel, which is typically the same as the pressure within the aorta, provided that the pressure-sensing channel is not obstructed. In some such embodiments, the processor is configured to check for any obstructions in the pressure-sensing channel. To do this, the processor calculates the magnitude of the phase difference between the first signal and a second signal indicative of the current consumed by the motor while rotating the impeller. In response to the magnitude of the phase difference, the processor can output an indication that the pressure within the pressure-sensing channel is different from the aortic pressure.

In some embodiments, the processor is further configured to compute respective estimated left ventricular end diastolic pressures for one or more cycles of the subject’s heart. In particular, for each of the cycles, the processor identifies a time tO at which the speed of the motor was a maximum, and identifies the estimated left ventricular end diastolic pressure for the cycle based on the value (e.g., the estimated value) of the left ventricular pressure of the subject during an interval [tO-c*D tO], c being a predefined constant and D being the duration of the cycle. The processor is further configured to display the estimated left ventricular end diastolic pressures or a statistic thereof.

There is therefore provided, in accordance with some embodiments of the present disclosure, apparatus for use with a left-ventricular assist device. The left-ventricular assist device includes a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The left-ventricular assist device further includes an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings. The left-ventricular assist device further includes a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section. The left -ventricular assist device further includes a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable. The apparatus includes a display and a processor. The processor is configured to compute respective estimated left ventricular end diastolic pressures for one or more cycles of the heart, by, for each of the cycles, identifying a time tO at which a speed of the motor was a maximum, and identifying the estimated left ventricular end diastolic pressure for the cycle based on a value of a left ventricular pressure of the subject during an interval [tO-c*D tO], c being a predefined constant and D being a duration of the cycle. The processor is further configured to display, on the display, the estimated left ventricular end diastolic pressures or a statistic thereof.

In some embodiments, c is between 0.2 and 0.4.

In some embodiments, identifying the estimated left ventricular end diastolic pressure for the cycle includes identifying the estimated left ventricular end diastolic pressure for the cycle as a minimum of the left ventricular pressure during the interval.

In some embodiments, the processor is further configured to compute a derivative of the speed, and identifying the estimated left ventricular end diastolic pressure for the cycle includes: identifying, in the interval, another time tm of a local minimum of the derivative, and identifying the estimated left ventricular end diastolic pressure for the cycle based on tm.

In some embodiments, identifying the estimated left ventricular end diastolic pressure for the cycle based on tm includes: determining that the left ventricular pressure is not decreasing at tm, and in response to the determining, identifying the estimated left ventricular end diastolic pressure for the cycle as the left ventricular pressure at tm. In some embodiments, identifying the estimated left ventricular end diastolic pressure for the cycle based on tm includes: determining that the left ventricular pressure is decreasing at tm, and in response to the determining, identifying the estimated left ventricular end diastolic pressure for the cycle as a minimum of the left ventricular pressure between tm and tO.

In some embodiments, the processor is further configured to compute the left ventricular pressure by: computing an estimated pressure gradient between the aorta and the left ventricle, based on a current consumed by the motor while rotating the impeller, and deriving the left ventricular pressure from the estimated pressure gradient.

In some embodiments, computing the estimated pressure gradient includes: computing a preliminary estimated pressure gradient between the aorta and the left ventricle, based on the current, based on the preliminary estimated pressure gradient, selecting an adjustment type from a group consisting of: a first adjustment type and a second adjustment type, and computing the estimated pressure gradient by adjusting the preliminary estimated pressure gradient per the selected adjustment type.

In some embodiments, selecting the adjustment type includes: comparing a peak-to-peak amplitude of the preliminary estimated pressure gradient to a peak-to-peak amplitude of an aortic pressure of the subject, and selecting the adjustment type in response to the comparison.

In some embodiments, the processor is configured to adjust the preliminary estimated pressure gradient per the first adjustment type by: identifying a minimum of the preliminary estimated pressure gradient during a previous cycle of the heart, and subtracting the minimum of the preliminary estimated pressure gradient from the preliminary estimated pressure gradient.

In some embodiments, the processor is configured to adjust the preliminary estimated pressure gradient per the second adjustment type by adding, to the preliminary estimated pressure gradient, at * P, where P is a mean aortic pressure of the subject over a previous interval and at is a predefined constant. In some embodiments, the processor is configured to compute the preliminary estimated pressure gradient by multiplying the current by a predefined constant.

In some embodiments, the processor is further configured to: determine a peak-to-peak amplitude of the current, and scale up or scale down the peak-to-peak amplitude of the current, prior to computing the preliminary estimated pressure gradient, in response to the peak-to-peak amplitude of the current being less than a first predefined threshold or greater than a second predefined threshold, respectively.

There is further provided, in accordance with some embodiments of the present disclosure, a method for use with a left-ventricular assist device. The left-ventricular assist device includes a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The left-ventricular assist device further includes an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings. The left-ventricular assist device further includes a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section. The left -ventricular assist device further includes a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable. The method includes computing, by a processor, respective estimated left ventricular end diastolic pressures for one or more cycles of the heart, by, for each of the cycles, identifying a time tO at which a speed of the motor was a maximum, and identifying the estimated left ventricular end diastolic pressure for the cycle based on a value of a left ventricular pressure of the subject during an interval [tO-c*D tO], c being a predefined constant and D being a duration of the cycle. The method further includes displaying on a display, by the processor, the estimated left ventricular end diastolic pressures or a statistic thereof.

There is further provided, in accordance with some embodiments of the present disclosure, a computer software product for use with a left-ventricular assist device. The left- ventricular assist device includes a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The left-ventricular assist device further includes an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings. The left- ventricular assist device further includes a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section. The left-ventricular assist device further includes a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable. The computer software product includes a tangible non-transitory computer-readable medium in which program instructions are stored. The instructions, when read by a processor, cause the processor to compute respective estimated left ventricular end diastolic pressures for one or more cycles of the heart, by, for each of the cycles, identifying a time tO at which a speed of the motor was a maximum, and identifying the estimated left ventricular end diastolic pressure for the cycle based on a value of a left ventricular pressure of the subject during an interval [tO-c*D tO], c being a predefined constant and D being a duration of the cycle. The instructions further cause the processor to display, on a display, the estimated left ventricular end diastolic pressures or a statistic thereof.

There is further provided, in accordance with some embodiments of the present disclosure, apparatus including a left-ventricular assist device and a processor. The left- ventricular assist device includes a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The left-ventricular assist device further includes an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube such that the blood exits the pump-outlet tube via the blood-outlet openings. The left- ventricular assist device further includes a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section. The left-ventricular assist device further includes a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable. The processor is configured to compute an estimated pressure gradient between the aorta and the left ventricle over an interval, based on a variation, over the interval, in a parameter related to the motor as the motor rotates the impeller. A maximal diameter of the impeller is at least 8 mm, such that the variation in the parameter is greater than if the maximal diameter of the impeller were less than 8 mm.

In some embodiments, the maximal diameter is at least 9 mm.

In some embodiments, the parameter includes a speed of the motor.

2

In some embodiments, a moment of inertia of the motor is less than 5 g-cm , such that

2

In some embodiments, the moment of inertia is less than 2 kg-m .

In some embodiments, the parameter includes a current consumed by the motor.

In some embodiments, at least partly because the maximal diameter of the impeller is at least 8 mm, the current increases by at least 0.5 mA for an increase of 1 mmHg in the pressure gradient between the aorta and the left ventricle.

In some embodiments, the current increases by at least 1 mA for the increase of 1 mmHg in the pressure gradient between the aorta and the left ventricle.

In some embodiments, the processor is configured to compute the estimated pressure gradient by: computing a preliminary estimated pressure gradient between the aorta and the left ventricle, based on the current, based on the preliminary estimated pressure gradient, selecting an adjustment type from a group consisting of: a first adjustment type and a second adjustment type, and computing the estimated pressure gradient by adjusting the preliminary estimated pressure gradient per the selected adjustment type.

In some embodiments, the processor is configured to adjust the preliminary estimated pressure gradient per the second adjustment type by adding, to the preliminary estimated pressure gradient, at * P, where P is a mean aortic pressure of the subject over a previous interval and at is a predefined constant.

In some embodiments, the processor is configured to compute the preliminary estimated pressure gradient by multiplying the current by a predefined constant.

There is further provided, in accordance with some embodiments of the present disclosure, apparatus including a left-ventricular assist device and a processor. The left- ventricular assist device includes a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The left-ventricular assist device further includes an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings. The left- ventricular assist device further includes a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section. The left-ventricular assist device further includes a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable. The processor is configured to compute an estimated pressure gradient between the aorta and the left ventricle over an interval, based on a variation, over the interval, in a parameter related to the motor as the motor rotates the impeller. The moment of inertia of the motor is less than 5 2 kg-m , such that the variation in the parameter is greater than if the moment of inertia were at

2 least 5 kg-m .

2

In some embodiments, the moment of inertia is less than 2 kg-m .

In some embodiments, the parameter includes a speed of the motor.

In some embodiments, a maximal diameter of the impeller is at least 8 mm, such that the variation in the parameter is greater than if the maximal diameter of the impeller were less than 8 mm.

In some embodiments, the maximal diameter of the impeller is at least 9 mm.

In some embodiments, the parameter includes a current consumed by the motor.

In some embodiments, at least partly because the moment of inertia is less than 5 2 kg-m , the current increases by at least 0.5 mA for an increase of 1 mmHg in the pressure gradient between the aorta and the left ventricle.

There is further provided, in accordance with some embodiments of the present disclosure, apparatus for use with a left-ventricular assist device. The left-ventricular assist device includes a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The left-ventricular assist device further includes an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings. The left-ventricular assist device further includes a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable. The apparatus includes a display and a processor. The processor is configured to compute, for a first interval, an estimated pressure in the left ventricle based on a parameter related to the motor as the motor rotates the impeller during the first interval, and to display the estimated pressure in the left ventricle on the display. The processor is further configured to determine that the pump-outlet tube was at least partly collapsed during a second interval following the first interval. The processor drives the display not to display the estimated pressure in the left ventricle, during the second interval.

In some embodiments, the processor is configured to determine that the pump-outlet tube was at least partly collapsed in response to the parameter changing more slowly following the first interval, relative to during the first interval.

In some embodiments, the parameter includes a current consumed by the motor.

In some embodiments, the processor is configured to compute the estimated pressure in the left ventricle by: computing an estimated pressure gradient between the aorta and the left ventricle, based on the current, and deriving the estimated pressure in the left ventricle from the estimated pressure gradient.

In some embodiments, the processor is configured to select the adjustment type by: comparing a peak-to-peak amplitude of the preliminary estimated pressure gradient to a peak-to-peak amplitude of an aortic pressure of the subject, and selecting the adjustment type in response to the comparison.

In some embodiments, the processor is further configured to: determine whether a minimum of the adjusted estimate is less than a third predefined threshold, and in response to determining that the minimum of the adjusted estimate is less than the third predefined threshold, for a subsequent first interval, compute the preliminary estimated pressure gradient by multiplying the adjusted current by the predefined constant and by another predefined constant that is less than one.

There is further provided, in accordance with some embodiments of the present disclosure, a method for use with a left-ventricular assist device. The left-ventricular assist device includes a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The left-ventricular assist device further includes an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings. The left-ventricular assist device further includes a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable. The method includes, for a first interval, computing, by a processor, an estimated pressure in the left ventricle based on a parameter related to the motor as the motor rotates the impeller during the first interval. The method further includes determining, by the processor, that the pump-outlet tube was at least partly collapsed during a second interval following the first interval. The method further includes, using the processor, driving the display to display the estimated pressure during the first interval, and not to display estimated pressure in the left ventricle during the second interval.

There is further provided, in accordance with some embodiments of the present disclosure, a computer software product for use with a left-ventricular assist device. The left- ventricular assist device includes a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The left-ventricular assist device further includes an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings. The left- ventricular assist device further includes a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable. The computer software product includes a tangible non- transitory computer-readable medium in which program instructions are stored. The instructions, when read by a processor, cause the processor to compute, for a first interval, an estimated pressure in the left ventricle based on a parameter related to the motor as the motor rotates the impeller during the first interval, to determine that the pump-outlet tube was at least partly collapsed during a second interval following the first interval, and to drive the display to display the estimated pressure during the first interval, and not to display an estimate of pressure in the left ventricle during the second interval.

There is further provided, in accordance with some embodiments of the present disclosure, apparatus for use with a left-ventricular assist device. The left-ventricular assist device includes a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The left-ventricular assist device further includes an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings. The left-ventricular assist device further includes a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable. The apparatus includes a display and a processor. The processor is configured to compute, for a first interval, an estimated pressure in the left ventricle based on a parameter related to the motor as the motor rotates the impeller during the first interval. The processor is further configured to determine that the pump-outlet tube was at least partly collapsed following the first interval. The processor is further configured to compute an adjusted estimate of the pressure, which is continuous with the estimated pressure, for a second interval following the first interval, in response to determining that the pump-outlet tube was at least partly collapsed, and to display the estimated pressure and the adjusted estimate of the pressure on the display.

In some embodiments, the processor is configured to compute the estimated pressure in the left ventricle by: computing an estimated pressure gradient between the aorta and the left ventricle, and deriving the estimated pressure in the left ventricle from the estimated pressure gradient, and the processor is configured to determine that the pump-outlet tube was at least partly collapsed in response to the estimated pressure gradient exceeding a predefined threshold value for a predefined threshold duration.

In some embodiments, the processor is configured to compute the adjusted estimate of the pressure based on a predefined set of adjustment parameters describing an expected change in the pressure over time.

In some embodiments, the parameter includes a current consumed by the motor.

In some embodiments, the processor is configured to compute the estimated pressure gradient includes: computing a preliminary estimated pressure gradient between the aorta and the left ventricle, based on the current, based on the preliminary estimated pressure gradient, selecting an adjustment type from a group consisting of: a first adjustment type and a second adjustment type, and computing the estimated pressure gradient by adjusting the preliminary estimated pressure gradient per the selected adjustment type.

In some embodiments, the processor is configured to select the adjustment type includes: comparing a peak-to-peak amplitude of the preliminary estimated pressure gradient to a peak-to-peak amplitude of an aortic pressure of the subject, and selecting the adjustment type in response to the comparison.

There is further provided, in accordance with some embodiments of the present disclosure, a method for use with a left-ventricular assist device. The left-ventricular assist device includes a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The left-ventricular assist device further includes an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings. The left-ventricular assist device further includes a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable. The method includes, for a first interval, computing, by a processor, an estimated pressure in the left ventricle based on a parameter related to the motor as the motor rotates the impeller during the first interval. The method further includes determining, by the processor, that the pump-outlet tube was at least partly collapsed following the first interval. The method further includes, in response to determining that the pump-outlet tube was at least partly collapsed, computing, by the processor, an adjusted estimate of the pressure, which is continuous with the estimated pressure, for a second interval following the first interval, and displaying on a display, by the processor, the estimated pressure and the adjusted estimate of the pressure.

There is further provided, in accordance with some embodiments of the present disclosure, a computer software product for use with a left-ventricular assist device. The left- ventricular assist device includes a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The left-ventricular assist device further includes an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings. The left- ventricular assist device further includes a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable. The computer software product includes a tangible non- transitory computer-readable medium in which program instructions are stored. The instructions, when read by a processor, cause the processor to compute, for a first interval, an estimated pressure in the left ventricle based on a parameter related to the motor as the motor rotates the impeller during the first interval, to determine that the pump-outlet tube was at least partly collapsed following the first interval, to compute an adjusted estimate of the pressure, which is continuous with the estimated pressure, for a second interval following the first interval, in response to determining that the pump-outlet tube was at least partly collapsed, and to display the estimated pressure and the adjusted estimate of the pressure on a display.

There is further provided, in accordance with some embodiments of the present disclosure, apparatus for use with a left-ventricular assist device including a pump-outlet tube configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that a proximal section of the pump-outlet tube is disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The apparatus includes a pressure sensor, configured to output a signal indicative of an aortic pressure within the aorta over an interval, and a processor. The processor is configured to compute an estimated pressure gradient between the aorta and the left ventricle over the interval. The processor is further configured to determine an indication of a peak-to-peak amplitude of the estimated pressure gradient between the aorta and the left ventricle over the interval. The processor is further configured to identify an indication of a minimum of the aortic pressure over the interval, based on the signal. The processor is further configured to compare the indication of the minimum of the aortic pressure to the indication of the peak-to-peak amplitude of the estimated pressure gradient between the aorta and the left ventricle over the interval. The processor is further configured to output an indication that the pump-outlet tube is positionally biased toward the aorta, in response to the comparing the indication of the minimum of the aortic pressure to the indication of the peak-to-peak amplitude of the estimated pressure gradient between the aorta and the left ventricle over the interval.

In some embodiments, the processor is configured to: determine the indication of the peak-to-peak amplitude of the estimated pressure gradient between the aorta and the left ventricle over the interval by determining the peak-to- peak amplitude of the estimated pressure gradient between the aorta and the left ventricle over the interval, identify the indication of the minimum of the aortic pressure over the interval by identifying the minimum of the aortic pressure over the interval, and compare the indication of the minimum of the aortic pressure to the indication of the peak-to-peak amplitude of the estimated pressure gradient between the aorta and the left ventricle over the interval by comparing the minimum of the aortic pressure to the peak-to- peak amplitude of the estimated pressure gradient between the aorta and the left ventricle over the interval.

In some embodiments, the processor is configured to: determine the indication of a peak-to-peak amplitude of the estimated pressure gradient between the aorta and the left ventricle over the interval by determining a y^th percentile of the peak-to-peak amplitude of the estimated pressure gradient between the aorta and the left ventricle over the interval, identify the indication of the minimum of the aortic pressure over the interval by identifying an x^th percentile of the aortic pressure over the interval, compare the indication of the minimum of the aortic pressure to the indication of the peak-to-peak amplitude of the estimated pressure gradient between the aorta and the left ventricle over the interval by comparing the x^th percentile of the aortic pressure over the interval to y^th percentile of the peak-to-peak amplitude of the estimated pressure gradient between the aorta and the left ventricle over the interval.

In some embodiments, the y^th percentile is equal to 100 percent minus the x^th percentile.

In some embodiments, the processor is configured to: determine the y^th percentile of the peak-to-peak amplitude of the estimated pressure gradient between the aorta and the left ventricle over the interval, by determining a percentile that is between 95^th and the 80^th percentiles of the peak-to-peak amplitude of the estimated pressure gradient between the aorta and the left ventricle over the interval; identify the x^th percentile of the aortic pressure over the interval, by determining a percentile that is between 5^th and the 20^th percentiles of the aortic pressure over the interval.

In some embodiments, the left-ventricular assist device further includes: an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the proximal section of the pump-outlet tube, a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable, and the processor is configured to compute the estimated pressure gradient by: computing a preliminary estimated pressure gradient between the aorta and the left ventricle, based on a current consumed by the motor while rotating the impeller, based on the preliminary estimated pressure gradient, selecting an adjustment type from a group consisting of: a first adjustment type and a second adjustment type, and computing the estimated pressure gradient by adjusting the preliminary estimated pressure gradient per the selected adjustment type.

There is further provided, in accordance with some embodiments of the present disclosure, a method for use with a left-ventricular assist device including a pump-outlet tube configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that a proximal section of the pump-outlet tube is disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The method includes computing, by a processor, an estimated pressure gradient between the aorta and the left ventricle over an interval. The method further includes determining, by the processor, an indication of a peak-to-peak amplitude of the estimated pressure gradient between the aorta and the left ventricle over the interval. The method further includes identifying, by the processor, an indication of a minimum of the aortic pressure over the interval, based on a signal, from a pressure sensor, indicative of an aortic pressure within the aorta over the interval. The method further includes comparing, by the processor, the indication of the minimum of the aortic pressure to the indication of the peak-to-peak amplitude of the estimated pressure gradient between the aorta and the left ventricle over the interval. The method further includes outputting, by the processor, an indication that the pump-outlet tube is positionally biased toward the aorta, in response to comparing the indication of the minimum of the aortic pressure to the indication of the peak-to-peak amplitude of the estimated pressure gradient between the aorta and the left ventricle over the interval. There is further provided, in accordance with some embodiments of the present disclosure, a computer software product for use with a left-ventricular assist device including a pump-outlet tube configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that a proximal section of the pump-outlet tube is disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle, the computer software product including a tangible non-transitory computer-readable medium in which program instructions are stored. The instructions, when read by a processor, cause the processor to compute an estimated pressure gradient between the aorta and the left ventricle over an interval. The instructions further cause the processor to determine an indication of a peak-to-peak amplitude of the estimated pressure gradient between the aorta and the left ventricle over the interval. The instructions further cause the processor to identify an indication of a minimum of the aortic pressure over the interval, based on a signal, from a pressure sensor, indicative of an aortic pressure within the aorta over the interval. The instructions further cause the processor to compare the indication of the minimum of the aortic pressure to the indication of the peak-to-peak amplitude of the estimated pressure gradient between the aorta and the left ventricle over the interval. The instructions further cause the processor to output an indication that the pump-outlet tube is positionally biased toward the aorta, in response to comparing the indication of the minimum of the aortic pressure to the indication of the peak-to-peak amplitude of the estimated pressure gradient between the aorta and the left ventricle over the interval.

There is further provided, in accordance with some embodiments of the present disclosure, apparatus for use with a left-ventricular assist device. The left-ventricular assist device includes a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The left-ventricular assist device further includes an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings. The left-ventricular assist device further includes a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable. The apparatus includes a display and a processor. The processor is configured to compute an estimated average current consumed by the motor, over an interval, while rotating the impeller, based on a speed of the motor during the interval, to compare the estimated average current to an actual average current consumed by the motor over the interval, and to display, on the display, an indication that the pump-outlet tube is positionally biased toward the left ventricle, in response to comparing the estimated average current to the actual average current.

In some embodiments, the processor is configured to compute the estimated average current as bi * s² + b2 * edP * s, where s is an average speed of the motor over the interval, s² is an average of a square of the speed of the motor over the interval, edP is an average of an estimated pressure gradient between the aorta and the left ventricle over the interval, and bi and b2 are predetermined constants.

There is further provided, in accordance with some embodiments of the present disclosure, a method for use with a left-ventricular assist device. The left-ventricular assist device includes a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The left-ventricular assist device further includes an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings. The left-ventricular assist device further includes a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable. The method includes computing, by a processor, an estimated average current consumed by the motor, over an interval, while rotating the impeller, based on a speed of the motor during the interval, comparing, by the processor, the estimated average current to an actual average current consumed by the motor over the interval, and in response to comparing the estimated average current to the actual average current, displaying on a display, by the processor, an indication that the pump-outlet tube is positionally biased toward the left ventricle.

There is further provided, in accordance with some embodiments of the present disclosure, a computer software product for use with a left-ventricular assist device. The left- ventricular assist device includes a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The left-ventricular assist device further includes an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings. The left- ventricular assist device further includes a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable. The computer software product includes a tangible non- transitory computer-readable medium in which program instructions are stored. The instructions, when read by a processor, cause the processor to compute an estimated average current consumed by the motor, over an interval, while rotating the impeller, based on a speed of the motor during the interval, to compare the estimated average current to an actual average current consumed by the motor over the interval, and to display, on a display, an indication that the pump-outlet tube is positionally biased toward the left ventricle, in response to comparing the estimated average current to the actual average current.

There is further provided, in accordance with some embodiments of the present disclosure, apparatus for use with a left-ventricular assist device including a pump-outlet tube configured to span an aortic valve of a heart of a subject. The apparatus includes a display and a processor. The processor is configured to compute a positional bias of the pump-outlet tube relative to the valve, and to display, on the display, an indicator having a property indicative of a direction of the bias and a color indicative of a magnitude of the bias.

In some embodiments, the color varies between green, yellow, and red, depending on the magnitude of the bias.

In some embodiments, the processor is configured to display the indicator on a graph having a horizontal axis representing time and a vertical axis representing the direction and magnitude of the bias, and the property includes a vertical position of the indicator.

In some embodiments, the pump-outlet tube is configured for insertion, through an aorta of the subject, into a left ventricle of the heart such that a proximal section of the pump-outlet tube is disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle, the positional bias is toward the aorta, and the processor is configured to compute the positional bias by: computing an estimated pressure gradient between the aorta and the left ventricle over an interval, based on a signal, from a pressure sensor, indicative of an aortic pressure within the aorta over the interval, identifying a minimum of the aortic pressure over the interval, comparing the minimum of the aortic pressure to a peak-to-peak amplitude of the estimated pressure gradient, and computing the positional bias in response to comparing the minimum of the aortic pressure to the peak-to-peak amplitude of the estimated pressure gradient.

In some embodiments, the pump-outlet tube is shaped to define one or more blood-outlet openings and is configured for insertion, through an aorta of the subject, into a left ventricle of the heart such that the blood-outlet openings are disposed within the aorta and a distal section of the pumpoutlet tube is disposed within the left ventricle, the left-ventricular assist device further includes: an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings, a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable, the positional bias is toward the left ventricle, and the processor is configured to compute the positional bias by: computing an estimated average current consumed by the motor, over an interval, while rotating the impeller, based on a speed of the motor during the interval, comparing the estimated average current to an actual average current consumed by the motor over the interval, and computing the positional bias in response to comparing the estimated average current to the actual average current.

There is further provided, in accordance with some embodiments of the present disclosure, a method for use with a left-ventricular assist device including a pump-outlet tube configured to span an aortic valve of a heart of a subject. The method includes computing, by a processor, a positional bias of the pump-outlet tube relative to the valve, and displaying on a display, by the processor, an indicator having a property indicative of a direction of the bias and a color indicative of a magnitude of the bias.

There is further provided, in accordance with some embodiments of the present disclosure, a computer software product for use with a left-ventricular assist device including a pump-outlet tube configured to span an aortic valve of a heart of a subject, the computer software product including a tangible non-transitory computer-readable medium in which program instructions are stored. The instructions, when read by a processor, cause the processor to compute a positional bias of the pump-outlet tube relative to the valve, and to display, on a display, an indicator having a property indicative of a direction of the bias and a color indicative of a magnitude of the bias.

There is further provided, in accordance with some embodiments of the present disclosure, apparatus for use with a left-ventricular assist device. The left-ventricular assist device includes a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The left-ventricular assist device further includes an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings. The left-ventricular assist device further includes a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable. The apparatus includes a display and a processor. The processor is configured to compute a preliminary estimated pressure gradient between the aorta and the left ventricle, based on a current consumed by the motor while rotating the impeller. The processor is further configured to select an adjustment type from a group consisting of: a first adjustment type and a second adjustment type, based on the preliminary estimated pressure gradient. The processor is further configured to compute a final estimated pressure gradient by adjusting the preliminary estimated pressure gradient per the selected adjustment type, and to display, on the display, the final estimated pressure gradient or another physiological parameter derived therefrom.

In some embodiments, the processor is further configured to derive a left ventricular pressure of the subject from the final estimated pressure gradient, and the processor is configured to display the left ventricular pressure.

In some embodiments, the processor is further configured to: determine a peak-to-peak amplitude of the current, and scale up or scale down the peak-to-peak amplitude of the current, prior to computing the preliminary estimated pressure gradient, in response to the peak-to-peak amplitude of the current being less than a first predefined threshold or greater than a second predefined threshold, respectively. There is further provided, in accordance with some embodiments of the present disclosure, a method for use with a left-ventricular assist device. The left-ventricular assist device includes a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The left-ventricular assist device further includes an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings. The left-ventricular assist device further includes a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable. The method includes computing, by a processor, a preliminary estimated pressure gradient between the aorta and the left ventricle, based on a current consumed by the motor while rotating the impeller. The method further includes, based on the preliminary estimated pressure gradient, selecting, by the processor, an adjustment type from a group consisting of: a first adjustment type and a second adjustment type. The method further includes computing, by the processor, a final estimated pressure gradient by adjusting the preliminary estimated pressure gradient per the selected adjustment type, and displaying on a display, by the processor, the final estimated pressure gradient or another physiological parameter derived therefrom.

There is further provided, in accordance with some embodiments of the present disclosure, a computer software product for use with a left-ventricular assist device. The left- ventricular assist device includes a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The left-ventricular assist device further includes an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings. The left- ventricular assist device further includes a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable. The computer software product includes a tangible non- transitory computer-readable medium in which program instructions are stored. The instructions, when read by a processor, cause the processor to compute a preliminary estimated pressure gradient between the aorta and the left ventricle, based on a current consumed by the motor while rotating the impeller, to select an adjustment type from a group consisting of: a first adjustment type and a second adjustment type, based on the preliminary estimated pressure gradient, to compute a final estimated pressure gradient by adjusting the preliminary estimated pressure gradient per the selected adjustment type, and to display, on a display, the final estimated pressure gradient or another physiological parameter derived therefrom.

There is further provided, in accordance with some embodiments of the present disclosure, apparatus for use with a left-ventricular assist device. The left-ventricular assist device includes a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The left-ventricular assist device further includes an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings. The left-ventricular assist device further includes a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section. The left-ventricular assist device further includes a catheter configured to surround the delivery tube within the aorta so as to define a pressure-sensing channel between the catheter and the delivery tube. The left- ventricular assist device further includes a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable. The apparatus includes a pressure sensor, configured to output a first signal indicative of a pressure within the pressure-sensing channel. The apparatus further includes a processor configured to calculate a magnitude of a phase difference between the first signal and a second signal indicative of a current consumed by the motor while rotating the impeller, and to output an indication that the pressure within the pressure-sensing channel is different from an aortic pressure within the aorta, in response to the magnitude of the phase difference.

There is further provided, in accordance with some embodiments of the present disclosure, a method for use with a left-ventricular assist device. The left-ventricular assist device includes a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The left-ventricular assist device further includes an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings. The left-ventricular assist device further includes a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section. The left -ventricular assist device further includes a catheter configured to surround the delivery tube within the aorta so as to define a pressure-sensing channel between the catheter and the delivery tube. The left- ventricular assist device further includes a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable. The method includes calculating, by a processor, a magnitude of a phase difference between a first signal, from a pressure sensor, indicative of a pressure within the pressuresensing channel, and a second signal indicative of a current consumed by the motor while rotating the impeller. The method further includes, in response to the magnitude of the phase difference, outputting, by the processor, an indication that the pressure within the pressuresensing channel is different from an aortic pressure within the aorta.

There is further provided, in accordance with some embodiments of the present disclosure, a computer software product for use with a left-ventricular assist device. The left- ventricular assist device includes a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle. The left-ventricular assist device further includes an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings. The left- ventricular assist device further includes a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section. The left-ventricular assist device further includes a catheter configured to surround the delivery tube within the aorta so as to define a pressure-sensing channel between the catheter and the delivery tube. The left-ventricular assist device further includes a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable. The computer software product includes a tangible non-transitory computer- readable medium in which program instructions are stored. The instructions, when read by a processor, cause the processor to calculate a magnitude of a phase difference between a first signal, from a pressure sensor, indicative of a pressure within the pressure-sensing channel, and a second signal indicative of a current consumed by the motor while rotating the impeller. The instructions further cause the processor to output an indication that the pressure within the pressure-sensing channel is different from an aortic pressure within the aorta, in response to the magnitude of the phase difference.

The present disclosure will be more fully understood from the following detailed description of embodiments thereof, taken together with the drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

Figs. 1A, IB, and 1C are schematic illustrations of a ventricular assist device, in accordance with some embodiments of the present disclosure;

Figs. ID and IE are schematic illustrations of a pump-head portion of a ventricular assist device, in accordance with some embodiments of the present disclosure;

Fig. IF is a schematic illustration of a ventricular assist device, in accordance with some embodiments of the present disclosure;

Fig. 2A plots the aortic pressure and left ventricular pressure of a subject, over several cardiac cycles, when using a left ventricular assist device in accordance with some embodiments of the present disclosure;

Fig. 2B plots, over the same cardiac cycles, the current consumed by the motor of the left ventricular assist device, in accordance with some embodiments of the present disclosure;

Fig. 2C plots, over the same cardiac cycles, the speed of the motor, in accordance with some embodiments of the present disclosure;

Fig. 2D plots the current consumed by the motor and a pressure gradient over several other cardiac cycles, in accordance with some embodiments of the present disclosure;

Fig. 3A shows a flow diagram for a method for estimating a pressure gradient, in accordance with some embodiments of the present disclosure;

Fig. 3B shows an example function for scaling the peak-to-peak amplitude of a current signal, in accordance with some embodiments of the present disclosure; Fig. 3C illustrates an example scaling of the peak-to-peak amplitude of a current signal, in accordance with some embodiments of the present disclosure;

Figs. 4A and 4B each plot an aortic pressure and a current over an interval, in accordance with some embodiments of the present disclosure;

Fig. 4C plots aortic pressure together with an estimate of left ventricular pressure, which is computed in accordance with some embodiments of the present disclosure;

Figs. 5A and 5B show flow diagrams for methods for checking the positioning of a pump-outlet tube, in accordance with some embodiments of the present disclosure;

Fig. 6 is a schematic illustration of a graph including a positional-bias indicator, in accordance with some embodiments of the present disclosure;

Fig. 7 shows a flow diagram for a method for detecting an obstruction in a pressuresensing channel, in accordance with some embodiments of the present disclosure;

Fig. 8 A plots the aortic pressure and left ventricular pressure of a subject, over several cardiac cycles, when using a left ventricular assist device in accordance with some embodiments of the present disclosure;

Fig. 8B plots, over the same cardiac cycles, the speed of the motor of the left ventricular assist device, in accordance with some embodiments of the present disclosure;

Fig. 8C plots, over the same cardiac cycles, the acceleration of the motor, in accordance with some embodiments of the present disclosure; and

Fig. 9 shows a flow diagram for a method for estimating the left ventricular end diastolic pressure for a cardiac cycle, in accordance with some embodiments of the present disclosure.

DETAILED DESCRIPTION

SYSTEM DESCRIPTION

Reference is initially made to Figs. 1 A, IB, and 1C, which are schematic illustrations of a ventricular assist device 20, a distal end of which is configured to be disposed in the left ventricle 22 of a subject 43, in accordance with some applications of the present disclosure.

Fig. 1 A shows an overview of a ventricular assist device system including, in addition to device 20, a control console 21 and a motor unit 23, which comprises a motor 31. Fig. IB shows the ventricular assist device being inserted into the subject's left ventricle, and Fig. 1C shows a pump-head portion 27 of the ventricular assist device in greater detail. Given that the scope of the present disclosure includes using the apparatus and methods described herein in anatomical locations other than the left ventricle and the aorta, the ventricular assist device and/or portions thereof are sometimes referred to herein (in the specification and the claims) as a blood pump.

Ventricular assist device 20 comprises a pump-outlet tube 24, which is shaped to define one or more blood-outlet openings 109. Typically, a proximal section 106 of the pump-outlet tube defines blood-outlet openings 109 such that the blood-outlet openings are near the proximal end 28 of pump-outlet tube 24. The pump-outlet tube is configured for insertion, through the aorta 30 of subject 43, into left ventricle 22 such that, by virtue of the pump-outlet tube traversing the aortic valve 26 of the subject, blood-outlet openings 109 are disposed within the aorta and a distal section 102 of the pump-outlet tube, which includes the distal end 32 of the pump-outlet tube, is disposed within the left ventricle. Pump-outlet tube 24 (which may also be referred to as a "blood-pump tube") is typically an elongate tube, an axial length of the pump-outlet tube typically being substantially larger than its diameter.

The ventricular assist device further comprises an impeller 50, which is disposed within distal section 102 and is configured to pump blood of the subject proximally through the pump-outlet tube such that the blood exits the pump-outlet tube via blood-outlet openings 109. Thus, during operation of impeller 50, blood flows from the pump-outlet tube into the ascending aorta.

The ventricular assist device further comprises a delivery tube 142 configured to extend, from outside the body of the subject, through the pump-outlet tube to the distal section of the pump-outlet tube. The device further comprises a drive cable 130 passing through the delivery tube and operatively coupled to impeller 50. Motor 31 is configured to rotate the impeller via drive cable 130.

The pump-outlet tube typically defines one or more blood-inlet openings 108 at the distal end of the pump-outlet tube, via which blood flows into the pump-outlet tube, from the left ventricle, during operation of the impeller. As shown in Fig. 1C, for some applications, the pump-outlet tube defines a single axially-facing blood-inlet opening. Alternatively, the pump-outlet tube defines a plurality of lateral blood-inlet openings (e.g., as shown in Fig. IB). For some applications, the ventricular assist device is used to assist the functioning of a subject's left ventricle during a percutaneous coronary intervention. In such cases, the ventricular assist device is typically used for a period of up to six hours (e.g., up to ten hours), during a period in which there is risk of developing hemodynamic instability (e.g., during or immediately following the percutaneous coronary intervention). Alternatively or additionally, the ventricular assist device is used to assist the functioning of a subject's left ventricle for a longer period (e.g., 2-20 days, e.g., 4-14 days) upon a patient suffering from cardiogenic shock, which can include any low-cardiac-output state (e.g., acute myocardial infarction, myocarditis, cardiomyopathy, post-partum, etc.). For some applications, the ventricular assist device is used to assist the functioning of a subject's left ventricle for yet a longer period (e.g., several weeks or months), e.g., in a "bridge to recovery" treatment. For some such applications, the ventricular assist device is permanently or semi-permanently implanted, and the impeller of the ventricular assist device is powered transcutaneously, e.g., using an external antenna that is magnetically coupled to the impeller.

As shown in Fig. IB, which shows steps in the deployment of the ventricular assist device in the left ventricle, typically the distal end of the ventricular assist device, which comprises pump-outlet tube 24 and a distal -tip element 107, is guided to the left ventricle, and inserted into the left ventricle, over a guidewire 10 (e.g., a standard 0.018 inch guidewire), which passes through distal -tip element 107. Typically, guidewire 10 comprises a soft atraumatic distal end.

During the insertion of the distal end of the device into the left ventricle, a delivery catheter 143 is disposed over the distal end of the device, such that delivery catheter 143 holds pump-outlet tube 24 in a radially-constrained configuration. In some embodiments, the delivery catheter is disposed within a standard sheath, such as a 10 Fr sheath. Once the distal end of the device is disposed in the left ventricle (and the sheath, if used, is withdrawn), the pump-outlet tube, along with other components of the device, are removed from the delivery catheter within the left ventricle, by retracting the delivery catheter from over the device. (In this context, advancing the device without advancing the delivery catheter is also referred to as a retraction of the delivery catheter.) The retraction of the delivery catheter typically causes self-expandable components of the distal end of the device, such as the pump-outlet tube, to assume non-radially-constrained configurations. Subsequently, the delivery catheter is typically retracted to the descending aorta, and guidewire 10 is withdrawn from the subject's body. For some applications, distal-tip element 107 is positioned at the apex of the left ventricle. Following the removal of the guidewire from the device, drive cable 130 is operatively coupled to motor 31, and the device is activated.

For some applications, in order to withdraw the left ventricular device from the subject's body at the end of the treatment, the delivery catheter is advanced over the distal end of the device, which causes the self-expandable components of the distal end of the device (e.g., the pump-outlet tube) to assume radially-constrained configurations. Alternatively or additionally, the distal end of the device is retracted into the delivery catheter which causes the self-expandable components of the distal end of the device to assume radially-constrained configurations.

For some applications (not shown), the ventricular assist device and/or delivery catheter 143 includes an ultrasound transducer at its distal end and the ventricular assist device is advanced toward the subject's ventricle under ultrasound guidance.

For some applications, control console 21 (shown in Fig. 1 A), which typically includes a computer processor 25 (also referred to as a “processor”), drives the impeller to rotate. For example, via a cable 224, the computer processor can control motor 31, which, as described above, drives the impeller to rotate via drive cable 130. For some applications, the computer processor is configured to detect or estimate a physiological parameter of the subject (such as left-ventricular pressure, cardiac afterload, rate of change of left- ventricular pressure, etc.) and to control rotation of the impeller in response thereto.

As further described below with reference to Fig. 3, processor 25 is configured to compute an estimated pressure gradient between the aorta and the left ventricle over an interval, based on a variation, over the interval, in a parameter related to motor 31 as the motor rotates the impeller. For example, in some embodiments, the processor is configured to compute the estimated pressure gradient based on a variation in the speed of the motor and/or in the current consumed by the motor. Typically, the processor is further configured to compute an estimated left ventricular pressure based on the estimated pressure gradient.

In some embodiments, the maximal diameter DO of the impeller - i.e., the diameter of the impeller when the impeller is maximally expanded - is at least 8 mm, e.g., at least 9 mm. By virtue of this relatively large maximal diameter, the variation in the motor-related parameter is greater than if the maximal diameter of the impeller were less than 8 mm; hence, the relatively large maximal diameter facilitates computing the estimated pressure gradient between the aorta and the left ventricle. For example, in some embodiments, at least partly because the maximal diameter of the impeller is at least 8 mm, the current consumed by the motor increases by at least 0.5 mA, e.g., at least 0.65 mA or 1 mA, for an increase of 1 mmHg in the pressure gradient between the aorta and the left ventricle.

2 Alternatively or additionally, the moment of inertia of motor 31 is less than 5 g-cm ,

2 e.g., less than 2 g-cm , such that the variation in the parameter is greater than if the moment

2 of inertia were at least 5 g-cm .

Typically, a fluid (e.g., a glucose solution) is pumped through portions of ventricular assist device 20. The fluid cools portions of the device, purges and/or lubricates interfaces between rotating parts and stationary bearings, and/or washes away debris. In some embodiments, the fluid flows into the device, from a purging-fluid bag 198, via an inlet port 86, and from the device, into a waste bag 200, via an outlet port 88. Details regarding the pumping of the fluid are provided, for example, in the description of Figs. 14 and 15A-B of co-assigned PCT Application No. PCT/IB2024/063109 to Tuval et al., whose disclosure is incorporated herein by reference.

Typically, console 21 further comprises a display 228. Processor 25 is configured to display, on display 228, the various outputs described herein.

Typically, along distal section 102 of pump-outlet tube 24, a frame 34 is disposed within the pump-outlet tube around impeller 50, distal -tip element 107 being disposed distally with respect to frame 34. The frame is typically made of a shape-memory alloy, such as nitinol. For some applications, the shape-memory alloy of the frame is shape set such that at least a portion of the frame (and thereby distal section 102 of tube 24) assumes a generally circular, elliptical, or polygonal cross-sectional shape in the absence of any forces being applied to distal section 102 of tube 24. By assuming its generally circular, elliptical, or polygonal cross- sectional shape, the frame is configured to hold the distal section of the pump-outlet tube in an open state. Typically, during operation of the ventricular assist device, the distal section of the pump-outlet tube is configured to be placed within the subject's body such that the distal section of the pump-outlet tube is disposed at least partially within the left ventricle.

For some applications, along proximal section 106 of pump-outlet tube 24, the frame is not disposed within the pump-outlet tube, and the pump-outlet tube is therefore not supported in an open state by frame 34. Pump-outlet tube 24 is typically made of a blood- impermeable collapsible material, such that the pump-outlet tube is collapsible. For example, pump-outlet tube 24 can include polyurethane, polyester, and/or silicone. Alternatively or additionally, the pump-outlet tube is made of polyethylene terephthalate (PET) and/or polyether block amide (e.g., PEBAX®). For some applications (not shown), the pump-outlet tube is reinforced with a reinforcement structure, e.g., a braided reinforcement structure, such as a braided nitinol tube. Typically, the proximal section of the pump-outlet tube is configured to be placed such that it is at least partially disposed within the subject's ascending aorta. For some applications, the proximal section of the pump-outlet tube traverses the subject's aortic valve, passing from the subject's left ventricle into the subject's ascending aorta, as shown in Fig. IB.

As described hereinabove, the pump-outlet tube typically defines one or more bloodinlet openings 108 at the distal end of the pump-outlet tube, via which blood flows into the pump-outlet tube from the left ventricle, during operation of the impeller. For some applications, the proximal section of the pump-outlet tube defines one or more blood-outlet openings 109, via which blood flows from the pump-outlet tube into the ascending aorta during operation of the impeller. Typically, the pump-outlet tube defines a plurality of blood-outlet openings 109, for example, between two and eight blood-outlet openings (e.g., between two and four blood-outlet openings). During operation of the impeller, the pressure of the blood flow through the pump-outlet tube typically maintains the proximal section of the tube in an open state. For some applications, in the event that, for example, the impeller malfunctions, the proximal section of the pump-outlet tube is configured to collapse inwardly, in response to pressure outside of the proximal section of the pump-outlet tube exceeding pressure inside the proximal section of the pump-outlet tube. In this manner, the proximal section of the pumpoutlet tube acts as a safety valve, preventing retrograde blood flow into the left ventricle from the aorta.

Referring again to Fig. 1C, for some applications, frame 34 is shaped such that the frame defines a proximal conical (or “frustoconical”) portion 36, a central cylindrical portion 38, and a distal conical portion 40. Typically, the proximal conical portion is proximally- facing, i.e., facing such that the narrow end of the cone is proximal with respect to the wide end of the cone. Further typically, the distal conical portion is distally-facing, i.e., facing such that the narrow end of the cone is distal with respect to the wide end of the cone.

For some applications, within at least a portion of frame 34 (e.g., along all of, or a portion of, the central cylindrical portion of the frame), an inner lining 39 (shown in Fig. ID) lines the frame. In accordance with respective applications, inner lining 39 partially overlaps or fully overlaps pump-outlet tube 24 over the portion of the frame that the inner lining lines. For other applications, as shown in Fig. 1C, the pump-head portion does not comprise an inner lining.

In some embodiments, pump-outlet tube 24 includes a conical proximal portion 42 and a cylindrical central portion 44, which typically spans proximal section 106 and distal section 102. The proximal conical portion is typically proximally-facing, i.e., facing such that the narrow end of the cone is proximal with respect to the wide end of the cone. Typically, bloodoutlet openings 109 are defined by pump-outlet tube 24 such that the openings extend at least partially along the proximal conical portion of tube 24. For some such applications, the bloodoutlet openings are teardrop-shaped, as shown in Fig. 1C. Typically, the teardrop-shaped nature of the blood-outlet openings in combination with the openings extending at least partially along the proximal conical portion of tube 24 causes blood to flow out of the bloodoutlet openings along flow lines that are substantially parallel with the longitudinal axis of tube 24 at the location of the blood-outlet openings.

For some applications (not shown), the diameter of pump-outlet tube 24 changes along the length of the central portion of the pump-outlet tube, such that the central portion of the pump-outlet tube has a frustoconical shape. For example, the central portion of the pumpoutlet tube can widen from its proximal end to its distal end, or can narrow from its proximal end to its distal end. For some applications, at its proximal end, the central portion of the pumpoutlet tube has a diameter of between 5 and 7 mm, and at its distal end, the central portion of the pump-outlet tube has a diameter of between 8 and 12 mm.

In some embodiments, drive cable 130 is coupled to an axial shaft 92, which passes through impeller 50 and is configured to rotate the impeller. In some such embodiments, distal- tip element 107 comprises an axial-shaft-receiving tube 126 and a distal-tip portion 120. Axial- shaft-receiving tube 126 is configured to receive a distal portion of axial shaft 92 during axial back-and-forth motion of the axial shaft, and/or during delivery of the ventricular assist device. (Typically, during delivery of the ventricular assist device, the frame is maintained in a radially-constrained configuration, which typically causes the axial shaft to be disposed in a different position with respect to the frame relative to its disposition with respect to the frame during operation of the ventricular assist device.) Typically, distal-tip portion 120 is configured to assume a curved shape upon being deployed within the subject's left ventricle, e.g., as shown in Fig. 1C. For some applications, the curvature of the distal-tip portion is configured to provide an atraumatic tip to ventricular assist device 20. Alternatively or additionally, the distal -tip portion is configured to space blood-inlet openings 108 of the ventricular assist device from walls of the left ventricle.

As shown in the enlarged portion of Fig. IB, for some applications, pump-outlet tube 24 extends to the end of distal conical portion 40 of the frame, and the pump-outlet tube defines a plurality of lateral blood-inlet openings 108. For some such applications, the pump-outlet tube defines a distal conical (or “frustoconical”) portion 47 that is distally facing, i.e., facing such that the narrow end of the cone is distal with respect to the wide end of the cone. For some such applications (not shown), the pump-outlet tube defines two to four lateral bloodinlet openings (e.g., four lateral blood-inlet openings). Typically, for such applications, each of the blood-inlet openings defines an area of more than 20 square mm (e.g., more than 30 square mm), and/or less than 60 square mm (e.g., less than 50 square mm), e.g., 20-60 square mm, or 30-50 square mm. Alternatively or additionally, the outlet tube defines a greater number of smaller lateral blood-inlet openings, e.g., more than 10 blood-inlet openings, more than 100 blood-inlet openings, more than 200 blood-inlet openings, or more than 300 bloodinlet openings, e.g., 50-100 blood-inlet openings, 100-300 blood-inlet openings, or 300-500 blood-inlet openings. For some such applications, each of the blood-inlet openings defines an area of more than 0.05 square mm (e.g., more than 0.1 square mm), and/or less than 3 square mm (e.g., less than 1 square mm), e.g., 0.05-3 square mm, or 0.1-1 square mm. Alternatively, each of the blood-inlet openings defines an area of more than 0.1 square mm (e.g., more than 0.3 square mm), and/or less than 5 square mm (e.g., less than 1 square mm), e.g., 0.1-5 square mm, or 0.3-1 square mm.

As described above, blood-inlet openings 108 are, in some embodiments, defined by distal conical portion 47 of the pump-outlet tube. As such, even the blood-inlet openings that are described as “lateral blood-inlet openings” are not necessarily oriented entirely laterally with respect to the longitudinal axis of the pump-outlet tube. Rather, they are, in some embodiments, obliquely disposed with respect to the longitudinal axis of the pump-outlet tube. By contrast, in some embodiments, the blood-outlet openings are described as “laterally-facing blood-outlet openings” because in such embodiments the blood-outlet openings are disposed laterally with respect to the longitudinal axis of the pump-outlet tube, by virtue of being defined by the central cylindrical portion of the pump-outlet tube. (In other embodiments, the blood-outlet openings are disposed obliquely with respect to the longitudinal axis of the pump- outlet tube, by virtue of being defined at least partially by the proximal conical portion of the pump-outlet tube.)

In some embodiments, proximally to proximal conical portion 42, the pump-outlet tube defines a tubular coupling portion 45, via which the pump-outlet tube is coupled (e.g., via an adhesive) to delivery tube 142. For some such embodiments, the pump-outlet tube is manufactured from a single continuous tube, with respective portions of the tube being molded to define tubular coupling portion 45, proximal conical portion 42, distal conical portion 47, and cylindrical central portion 44. Typically, in such cases, the blood-inlet openings and the blood-outlet openings are cut (e.g., laser cut) from the tube.

In some embodiments, (a) blood-outlet openings 109 are defined by portions of the wall of the blood outlet tube that at least partially extends into the proximal conical portion of the pump-outlet tube, and/or (b) blood-outlet openings 109 are laterally facing, by virtue of being defined by the central cylindrical portion of pump-outlet tube 24. (As noted hereinabove, “laterally-facing blood-outlet openings” should be interpreted to mean that the blood-outlet openings are disposed laterally with respect to the longitudinal axis of the pump-outlet tube, by virtue of being defined by the central cylindrical portion of the pump-outlet tube. This is in contrast to blood-inlet openings that are described as “lateral blood-inlet openings,” which are typically not oriented entirely laterally with respect to the longitudinal axis of the pump-outlet tube, but rather, are oblique with respect to the longitudinal axis of the pump-outlet tube.) The scope of the present disclosure includes combining other features of the pump-outlet tube and/or other portions of the ventricular assist device with any configuration of blood-outlet openings that are described and/or shown in the present application.

In some embodiments, a pressure sensor 206 is connected, via a pressure-sensing tube 179 of device 20, to an aortic pressure-sensing channel 147 passing between delivery catheter 143 and delivery tube 142, e.g., as described with reference to Fig. 14 of co-assigned US Provisional Application 63/566,681, whose disclosure is incorporated herein by reference. While the pressure-sensing channel is located within the aorta, pressure sensor 206 outputs, to processor 25, a signal indicative of the pressure within the aorta. Typically, a flushing-fluid bag 202 contains a flushing fluid (e.g., saline) for flushing aortic pressure-sensing channel 147 via pressure-sensing tube 179.

As further described below with reference to Fig. 3, in some embodiments, processor 25 is configured to estimate the left ventricular pressure of the subject based on aortic pressure measurements acquired by pressure sensor 206. Alternatively or additionally, a pressure sensor directly measures the left ventricular pressure, e.g., as described in co-assigned International Application PCT/IB2023/059136, published as International Application Publication WO/2024/057252 to Tuval et al., whose disclosure is incorporated herein by reference.

Reference is now made to Fig. ID, which is a schematic illustration of a pump-head portion of a ventricular assist device, in accordance with some embodiments of the present disclosure.

In some embodiments, pump-outlet tube 24 does not define a tubular coupling portion. Rather, initially, the proximal portion of the tube that will form the proximal conical section is shaped as a cylinder (which is typically continuous with the cylinder shape of the central portion). From this proximal portion of the tube, strips are cut (e.g., laser cut), leaving other strips 29 still attached to, and extending proximally from, the central cylindrical portion of the tube. The proximal ends of strips 29 are then adhered to delivery tube 142 of the ventricular assist device, in such a manner that they define a proximal conical portion of the pump-outlet tube that defines blood-outlet openings 109. In other words, blood-outlet openings 109 are formed between strips 29, by adhering the strips to delivery tube 142 of the ventricular assist device.

For some applications, by forming the proximal conical portion of the pump-outlet tube and the blood-outlet openings using the latter method, the thickness of the layer of the pumpoutlet tube that is coupled to delivery tube 142 is less than the thickness of the tubular coupling portion as formed by the former method. For some applications, this reduces the sharpness of the diameter change at the interface between delivery tube 142 and the region at which the proximal end of the pump-outlet tube is coupled to the delivery tube.

Reference is now made to Figs. IE and IF, which is a schematic illustration of pumphead portion 27, in accordance with some embodiments of the present disclosure. Reference is also made to Fig. IF, which is a schematic illustration of ventricular assist device 20, in accordance with some applications of the present disclosure.

In some embodiments, an expandable element 314 surrounds delivery tube 142. In some such embodiments, expandable element 314 comprises an expandable stent or expandable braided element. Alternatively, expandable element 314 comprises an inflatable element 316 (e.g., a balloon). For some applications, inflatable element 316 is inflated using a fluid (e.g., air or saline) that is pumped through the ventricular-assist device. For example, in some embodiments, as shown in Fig. IE, the wall of the delivery tube is shaped to define one or more openings 320, and inflatable element 316 surrounds openings 320 such that a fluid flowing, via the openings, from the delivery tube into the inflatable element inflates the inflatable element. Typically, the inflating fluid includes purging fluid, which, distally to openings 320, purges the interface between the axial shaft and any stationary bearings (including radial and/or thrust bearings) that don't rotate with the axial shaft. Alternatively or additionally, the inflating fluid comes from a separate, dedicated supply.

In some embodiments, expandable element 314 is entirely proximal to the pump-outlet tube, e.g., as shown in Fig. IF. In other embodiments, as shown in Fig. IE, expandable element 314, at least when expanded, is disposed at least partly within, e.g., entirely within, pumpoutlet tube 24. In some such embodiments, the pump-outlet tube does not comprise a conical proximal portion, and is not coupled directly to delivery tube 142. In any case, typically, for embodiments in which the pump-outlet tube is shaped to define blood-outlet openings 109, expandable element 314 is proximal to blood-outlet openings 109, with the length of the delivery tube between expandable element 314 and the blood-outlet openings being less than 30 mm.

Expandable element 314 is configured to protect the aortic wall from injury, e.g., by inhibiting the edges of blood-outlet openings 109, which are sometimes sharp, from contacting the wall of the aorta. Alternatively or additionally, expandable element 314 is configured to center a portion of the ventricular assist device (e.g., the portion of delivery tube 142 near the pump-outlet tube) within the aorta. Expandable element 314 is configured to perform these functions by abutting the aortic wall.

Alternatively or additionally, expandable element 314 is shaped to direct the blood through blood-outlet openings 109, as indicated in Fig. IE by blood-flow arrows 318. For example, in some embodiments, the distal end of the expandable element has a width that decreases moving distally, e.g., the distal end is frustoconical, such that the blood is directed by the distal end of the expandable element, at an angle, through the blood-outlet openings. Alternatively or additionally, the expandable element has an angled and/or a curved surface that is configured to direct the blood flow in this manner. For some applications, by directing blood flow in this manner, the overall pumping efficiency of the device is increased, relative to if the device would not include an expandable element.

It is noted that expandable element 314 can be combined with any of the embodiments of pump-outlet tube 24 described with reference to Figs. 33A-C of co-assigned International Application PCT/IB2023/059136, published as International Application Publication WO/2024/057252 to Tuval et al., whose disclosure is incorporated herein by reference.

In general, processor 25 can be embodied as a single processor, or as a cooperatively networked or clustered set of processors. The functionality of processor 25 can be implemented solely in hardware, e.g., using one or more fixed -function or general-purpose integrated circuits, Application-Specific Integrated Circuits (ASICs), and/or Field- Programmable Gate Arrays (FPGAs). Alternatively, this functionality can be implemented at least partly in software. For example, processor 25 can be embodied as a programmed processor comprising, for example, a central processing unit (CPU) and/or a Graphics Processing Unit (GPU). Program code, including software programs, and/or data can be loaded for execution and processing by the CPU and/or GPU. The program code and/or data can be downloaded to the processor in electronic form, over a network, for example. Alternatively or additionally, the program code and/or data can be provided and/or stored on non-transitory tangible media, such as magnetic, optical, or electronic memory. Such program code and/or data, when provided to the processor, produce a machine or special -purpose computer, configured to perform the tasks described herein.

Typically, the operations described herein that are performed by computer processor 25, transform the physical state of a memory, which is a real physical article that is in communication with the computer processor, to have a different magnetic polarity, electrical charge, or the like, depending on the technology of the memory that is used. Computer processor 25 is typically a hardware device programmed with computer program instructions to produce a special-purpose computer. For example, when programmed to perform the techniques described herein, computer processor 25 typically acts as a special-purpose, ventricular-assist computer processor and/or a special-purpose, blood-pump computer processor.

ESTIMATING LEFT VENTRICULAR PRESSURE

Reference is now made to Fig. 2A, which plots the aortic pressure 52 and left ventricular pressure 54 of a subject, over several cardiac cycles, when using a left ventricular assist device in accordance with some embodiments of the present disclosure. Reference is also made to Fig. 2B, which plots, over the same cardiac cycles, the current 56 consumed by the motor of the left ventricular assist device, in accordance with some embodiments of the present disclosure. Reference is additionally made to Fig. 2C, which plots, over the same cardiac cycles, the rotation speed 58 of the motor, in accordance with some embodiments of the present disclosure. For one of the cardiac cycles, the starting time tl of the cycle, the time t2 at which the systolic phase of the cycle ends and the diastolic phase begins, and the ending time t3 of the cycle are marked in each of Figs. 2A-C.

Reference is also made to Fig. 2D, which plots current 56 and a pressure gradient 60 over several other cardiac cycles, in accordance with some embodiments of the present disclosure. Pressure gradient 60, designated herein as “dP,” is the difference between aortic pressure 52 and left ventricular pressure 54. This pressure gradient is the resistance faced by the motor in rotating the impeller of the left ventricular assist device.

Typically, the motor is configured to draw a varying amount of current such that rotation speed 58 remains close to a predefined target speed. For example, as dP decreases during systole (e.g., between tl and t2), such that the rotation speed increases, the motor decreases the current drawn. Conversely, as dP increases during the initial portion of diastole (e.g., shortly after t2), such that the rotation speed decreases, the motor increases the current drawn.

In some embodiments, the processor capitalizes on the variation in the rotation speed, and/or the variation in the current, to estimate dP. (As described above with reference to Figs. 1A-C, in some embodiments, the maximal diameter of the impeller, and/or the moment of inertia of the motor, are selected so as to facilitate this estimation.) Typically, to facilitate the estimation of dP, current 56 and/or speed 58 are sampled, by the processor, at a rate of at least 50 Hz, such as at least 100 Hz.

Figs. 2A-D correspond to a case in which the aortic valve opens during systole. In such a case, the estimation of dP can rely on the assumption that the minimum value of dP, reached during systole, is zero. In other cases, however, the aortic valve does not open, and a different methodology for the estimation of dP is required.

To address this challenge, in some embodiments, the processor first computes a preliminary estimated pressure gradient edPprelim between the aorta and the left ventricle, based on the current consumed by the motor. For example, in some embodiments, the processor computes edPprelim by multiplying the current by a predefined constant ao. Typically, the oscillation in edPprelim accurately reflects the oscillation in dP, but edPprelim is shifted higher or lower relative to dP, such that an adjustment to edPprelim is required. Following the computation of edPprelim, the processor selects between two adjustment types: a first adjustment type, which is for cases in which the aortic valve is opening, and a second adjustment type, which is for cases in which the aortic valve is not opening. The processor then computes the estimated pressure gradient by adjusting edPp_relim per the selected adjustment type.

For further details regarding the estimation of dP, reference is now made to Fig. 3A, which shows a flow diagram for a method 62 for estimating dP, in accordance with some embodiments of the present disclosure. Reference is also made to Fig. 3B, which shows an example function for scaling the peak-to-peak amplitude of a current signal, in accordance with some embodiments of the present disclosure.

The inventors have observed that the current drawn by the motor is not fully indicative of the pressure gradient when the peak-to-peak amplitude of the current is below a first threshold or above a second threshold. Hence, in some embodiments, prior to computing the preliminary estimated pressure gradient, the processor determines the peak-to-peak amplitude of the current at a determining step 53. Next, at a first comparing step 55, the processor checks whether the peak-to-peak amplitude of the current is less than a first predefined threshold, identified as “thl” in Fig. 3B. If yes, the processor scales up the peak-to-peak amplitude of the current, at a scaling-up step 61. Otherwise, at a second comparing step 63, the processor checks whether the peak-to-peak amplitude of the current is greater than a second predefined threshold, identified as “th2” in Fig. 3B. If yes, the processor scales down the peak-to-peak amplitude of the current, at a scaling-down step 64. (Alternatively, second comparing step 63 is performed prior to first comparing step 55.) Subsequently to scaling the peak-to-peak amplitude, or if no scaling is required, the processor computes edPprelim from the current at a preliminary estimating step 66.

In some embodiments, the scaling factor is a constant. In other embodiments, the scaling factor is not constant, i.e., the scaling factor varies with the peak-to-peak amplitude of the current, such that the scaled peak-to-peak amplitude is a non-linear function.

Typically, one or more characteristics of edPprelim indicate whether the aortic valve is opening. Hence, typically, the processor selects the adjustment type based on edPprelim.

For example, in some embodiments, the processor compares the peak-to-peak amplitude of edPprelim to the peak-to-peak amplitude of the aortic pressure of the subject, e.g., by comparing a ratio of the amplitudes to a predefined threshold. In response to the comparison, the processor selects the adjustment type. More specifically, in response to a small peak-to-peak amplitude of edPp_relim relative to the peak-to-peak amplitude of the aortic pressure, the processor selects the first adjustment type. Conversely, in response to a large peak-to-peak amplitude of edPprelim relative to the peak-to-peak amplitude of the aortic pressure, the processor selects the second adjustment type. In other words, the processor checks, at a checking step 68, whether the peak-to-peak amplitude of edPprelim, relative to the peak-to-peak amplitude of the aortic pressure, indicates that the aortic valve is opening. If yes, the processor performs an adjustment of the first type; otherwise, the processor performs an adjustment of the second type.

In some embodiments, when adjusting edPprelim per the first adjustment type, the processor first identifies the minimum of edPprelim during a previous cycle of the heart, at a minimum-identifying step 70. Typically, this previous cycle is the most recent cycle prior to the time for which dP is to be estimated. In some embodiments, to facilitate searching for the minimum in this cycle, the processor computes the approximate duration of each cardiac cycle, e.g., based on a Fourier transform of the aortic pressure signal.

Next, at a minimum-subtracting step 72, the processor subtracts the minimum of edPprelim from edPprelim- The resulting estimate of the pressure gradient, designated herein as edP, thus has a minimum of zero, as expected for cases in which the aortic valve opens.

On the other hand, in some embodiments, per the second adjustment type, at an adjusting step 74, the processor adjusts edPprelim based on the aortic pressure. For example, in some embodiments, the processor adds, to edPprelim, at * P, where P is the mean aortic pressure of the subject over a previous interval (having a length of around 10 seconds, for example), and at is a predefined constant. The effect of this adjustment is to shift edPprelim in accordance with P, with which dP is correlated.

Following the computation of edP, the processor displays, on display 228 (Fig. 1), edP and/or another physiological parameter derived therefrom. Typically, the processor displays edP and/or the derived physiological parameter by plotting edP and/or the derived physiological parameter against a time axis, e.g., for the previous 10 seconds.

For example, in some embodiments, the processor, at a left-ventricular-pressure- estimating step 75, computes an estimated left ventricular pressure by subtracting edP from the aortic pressure. The estimated left ventricular pressure is then displayed.

Reference is now made to Fig. 3C, which illustrates an example scaling of the peak- to-peak amplitude of a current signal, in accordance with some embodiments of the present disclosure.

As described above with reference to Figs. 3 A-B, in some embodiments, the processor scales down the peak-to-peak amplitude of the current if the peak-to-peak amplitude is greater than a threshold. By way of illustration, Fig. 3C shows an original current signal 56o together with a modified current signal 56m in which the peak-to-peak amplitude is scaled down. Typically, for both an upscaling and a downscaling, the scaling preserves the average value of the current, as shown in Fig. 3C.

Reference is now made to Figs. 4A-B, each of which plots both aortic pressure 52 and current 56 over an interval, in accordance with some embodiments of the present disclosure.

For some motors, once the pressure gradient between the aorta and the left ventricle exceeds a particular cutoff, the motor cannot keep the pump-outlet tube open, and the pumpoutlet tube at least partly collapses. A challenge, in such cases, is that due to the collapse of the pump-outlet tube, which impedes the flow of blood through the pump-outlet tube, the motor responds less (e.g., the motor does not respond at all) to changes in the pressure gradient. As a result, the regular estimate of dP, which is based on a motor-related parameter (e.g., the speed of the motor or the current consumed by the motor, e.g., as described above with reference to Fig. 3), is inaccurate.

In some embodiments, to address this challenge, the processor is configured to identify an interval, which has a start time ts and an end time te, during at least part of which the pumpoutlet tube was at least partly collapsed. The processor then computes an adjusted estimate of the left ventricular pressure for the interval. Both the regular estimate, which is in effect for intervals prior to ts and following te, and the adjusted estimate are displayed on display 228 (Fig. 1 A). Advantageously, the adjusted estimate is continuous with the regular estimate, such that the viewer of the display is not aware of the adjustment.

In other words, for a first interval, the processor computes an estimated pressure in the left ventricle based on the motor-related parameter, e.g., as described above with reference to Fig. 3. If the processor determines that the pump-outlet tube was at least partly collapsed following the first interval, the processor computes an adjusted estimate of the left ventricular pressure, which is continuous with the estimate for the first interval, for a second interval following the first interval. The processor then displays the estimated pressure for the first interval, and the adjusted estimate of the pressure for the second interval, on the display.

In some embodiments, the processor is configured to determine that the pump-outlet tube was at least partly collapsed in response to the motor-related parameter changing more slowly following the first interval, relative to during the first interval. For example, a slow change in current 56 is seen in Fig. 4A between ts and te, repeating for each cardiac cycle. In some embodiments, the processor identifies the slow change by computing the difference between the time at which aortic pressure 52 reaches a minimum value 59 and the time at which current 56 reaches a maximum value 57, and comparing this difference to a predefined threshold.

In other embodiments, the processor is configured to determine that the pump-outlet tube was at least partly collapsed in response to the estimated dP exceeding a predefined threshold value, which is typically close to the aforementioned cutoff gradient, for a predefined threshold duration. For example, the processor can use this technique for cases in which the motor-related parameter flattens (approximately). A flattening of current 56 is shown, by way of example, in Fig. 4B between ts and te, repeating for each cardiac cycle.

The present inventors realized that a slow change in the current, as in Fig. 4A, indicates a partial collapse of the pump-outlet tube, whereas a flattening of the current, as shown in Fig. 4B, indicates a full collapse of the pump-outlet tube. It is generally preferred that the pumpoutlet tube be fully collapsed - rather than only partly collapsed - above the cutoff pressure gradient, at least because the behavior of the device is more predictable in such a case.

The inventors further discovered that a partial collapse is typically due to the pumpoutlet tube being relatively thick, which is typically the case for embodiments in which the pump-outlet tube comprises tubular coupling portion 45, e.g., as shown in Fig. 1C, by virtue of manufacturing constraints. In contrast, for embodiments in which the pump-outlet tube does not comprise the tubular coupling portion, e.g., as shown in Fig. ID, the pump-outlet tube can be thinner. As a result of the reduced thickness of the pump-outlet tube, the pump-outlet tube fully collapses.

In some embodiments, the processor sets ts to the time at which the current, prior to attaining maximum value 57, attains a predefined percentile value or percentage of maximum value 57. The processor then sets te to ts + p*L, where p is a predefined percentage (e.g., around 40%) and L is the approximate length of each cardiac cycle.

In other embodiments, the processor determines that the pump-outlet tube was at least partly collapsed, and/or sets ts and te, based on the derivative of the motor-related parameter. For example, in some embodiments, the processor sets ts to the time at which the derivative of current 56 drops below a predefined threshold, prior to the current attaining maximum value 57. Alternatively or additionally, the processor sets te to the time at which the absolute value of the derivative of the current rises above a predefined threshold, subsequently to the current attaining maximum value 57.

Typically, the processor computes the adjusted estimate of the left ventricular pressure based on a predefined set of adjustment parameters describing the expected change in the pressure over time.

In some embodiments, if the minimum of the adjusted estimate is less than a predefined threshold (e.g., -5 mmHg), the processor decreases the peak-to-peak amplitude of edPprelim, thereby increasing the minimum of the adjusted estimate in the next interval for which the adjusted estimate is computed. For example, in some embodiments, the processor computes edPprelim by multiplying ladj by ao and by another predefined constant a3 that is less than one, such as 0.95. If, again, the minimum of the adjusted estimate is less than the predefined threshold, the equation is adjusted to edPprelim = ladj * ao * (as) . In this manner, the processor continues to increase the exponent to which as is raised, until the minimum of the adjusted estimate is not less than the predefined threshold.

By way of illustration, reference is now made to Fig. 4C, which plots aortic pressure 52 together with an estimate 54e of left ventricular pressure, which is computed in accordance with some embodiments of the present disclosure.

Fig. 4C illustrates a case in which the processor determines that the pump-outlet tube was at least partly collapsed starting at the first cardiac cycle shown in the figure. In response thereto, the processor computes, instead of the regular estimate 54e, an adjusted estimate 54e’ for the period between ts and te. The processor then determines that the minimum of adjusted estimate 54e’ is less than the predefined threshold. In response thereto, for the second cardiac cycle shown in the figure, the processor decreases the peak-to-peak amplitude of edPprelim, thereby arriving at another adjusted estimate 54e” for the period between ts and te. (To avoid any confusion, it is noted that although estimate 54e is shown in Fig. 4C for both cardiac cycles, and adjusted estimate 54e’ is shown for the second cardiac cycle, in practice, for the period between ts and te, the processor displays only adjusted estimate 54e’ for the first cardiac cycle, and only adjusted estimate 54e” for the second cardiac cycle.)

Typically, the processor does not decrease the peak-to-peak amplitude of edPprelim while the subject’s left ventricle is beating arrhythmically. In some embodiments, the processor detects an arrhythmia based on a frequency-domain analysis of the aortic pressure signal.

In some applications, in the event that the processor identifies an interval (which has a start time ts and an end time te), during at least part of which the pump-outlet tube was at least partly collapsed, the processor drives the display not to display the left ventricular pressure during the interval. In other words, the display is driven to display the left ventricular pressure whenever it can be accurately estimated based on the motor current (e.g., during a first interval, in which the left ventricular pressure whenever it can be accurately estimated based on the motor current). However, during intervals in which at least part of which the pump-outlet tube is at least partly collapsed such that the regular relationship between the motor current and the left ventricular pressure is not applicable (e.g., during a second interval following the first interval), the left ventricular pressure is not displayed.

DETECTING POSITIONAL BIAS AND OBSTRUCTIONS

Typically, while device 20 (Fig. 1) is in use, the processor continually checks whether pump-outlet tube 24 (Fig. IB) is positioned correctly. For example, in some embodiments, the processor checks whether the pump-outlet tube is positionally biased toward the aorta (i.e., whether the position of the pump-outlet tube is overly proximal, such that too much of the pump-outlet tube is within the aorta). Alternatively or additionally, the processor checks whether the pump-outlet tube is positionally biased toward the left ventricle (i.e., whether the position of the pump-outlet tube is overly distal, such that too much of the pump-outlet tube is within the left ventricle).

In this regard, reference is now made to Figs. 5A and 5B, which shows flow diagrams for a method 76 for checking the positioning of the pump-outlet tube, in accordance with some embodiments of the present disclosure.

Referring first to Fig. 5A, in accordance with method 76, the processor computes, at a gradient-estimating step 77, the estimated pressure gradient edP over an interval (having a length of around 10 seconds, for example). In some embodiments, the processor performs this estimation by executing method 62 (Fig. 3). Based upon the estimated pressure gradient edP over an interval, the processor determines the amplitude of the estimated pressure gradient edP over the interval (step 78). Additionally, based on the aortic-pressure-indicating signal received from pressure sensor 206 (Fig. 1 A), the processor, at a minimum-identifying step 80, identifies the minimum of the aortic pressure over the interval.

Typically, the method used for gradient-estimating step 77 is calibrated such that, if the pump-outlet tube is not positionally biased toward the aorta, the peak-to-peak amplitude of edP is approximately equal to the minimum of the aortic pressure. On the other hand, if the pump-outlet tube is positionally biased toward the aorta, the peak-to-peak amplitude of edP is less than the minimum of the aortic pressure. Therefore, at a comparing step 82, the processor compares the minimum aortic pressure to the peak-to-peak amplitude of edP, e.g., by comparing a ratio of these two quantities to a predetermined threshold. If the two quantities are not sufficiently close to one another, the processor, at an outputting step 84, outputs an indication that the pump-outlet tube is positionally biased toward the aorta, e.g., as described below with reference to Fig. 6.

In some embodiments, the processor identifies a magnitude of the bias and outputs an indication of the magnitude, e.g., as described below with reference to Fig. 6. For example, in some embodiments, if the ratio of the minimum aortic pressure to the peak-to-peak amplitude of edP exceeds a first threshold but does not exceed a second threshold, the processor identifies a lesser magnitude. On the other hand, if the ratio also exceeds the second threshold, the processor identifies a greater magnitude.

On the other hand, if the minimum aortic pressure to the peak-to-peak amplitude of edP are sufficiently close to one another, the processor proceeds to check whether the pumpoutlet tube is positionally biased toward the left ventricle. (In other embodiments, the latter check is performed before checking whether the pump-outlet tube is positionally biased toward the aorta.)

As the present inventors have observed, a positional bias toward the left ventricle typically causes greater stress on the motor, such that the motor needs to consume more current to maintain its speed of rotation. Hence, in some embodiments, to check whether the pumpoutlet tube is positionally biased toward the left ventricle, the processor first computes an estimated average current consumed by the motor, over an interval (having a length of around 10 seconds, for example), while rotating the impeller, based on the speed of the motor during the interval, at an average-current-estimating step 87. (In other words, the processor first computes an expected average current consumed by the motor, assuming the pump-outlet tube is correctly positioned.) For example, in some embodiments, the processor computes the estimated average current as bi * s² + b2 * edP * s, where s is the average speed of the motor over the interval, s² is the average of the square of the speed over the interval, edP is the average of the estimated pressure gradient between the aorta and the left ventricle over the interval, and bi and b2 are predetermined constants.

Next, at another comparing step 89, the processor compares the estimated average current to the actual average current consumed by the motor over the interval, e.g., by comparing a ratio of these two quantities to a predetermined threshold. If the two quantities are not sufficiently close to one another, the processor, at an outputting step 90, outputs an indication that the pump-outlet tube is positionally biased toward the left ventricle, e.g., as described below with reference to Fig. 6. Otherwise, method 76 ends.

In some embodiments, the processor identifies a magnitude of the bias and outputs an indication of the magnitude, e.g., as described below with reference to Fig. 6. For example, in some embodiments, if the ratio of the estimated average current to the actual average current exceeds a first threshold but does not exceed a second threshold, the processor identifies a lesser magnitude. On the other hand, if the ratio also exceeds the second threshold, the processor identifies a greater magnitude.

Alternatively or additionally to a ratio, the processor can compute a difference between the estimated average current and the actual average current, and compare this difference to one or more thresholds. Similarly, it is noted that for any other comparison between two quantities mentioned in the present specification, the processor can perform the comparison using a ratio and/or a difference between the quantities.

Reference is now made to Fig. 5B, which is a flow diagram showing method 76 being implemented with some variations, in accordance with some applications of the present disclosure. Most of the steps of the flow diagram shown in Fig. 5B are generally as described with reference to Fig. 5 A, except where described otherwise.

In the method described with reference to Fig. 5 A, at step 78, based upon the estimated pressure gradient edP over an interval, the processor determines the amplitude of the estimated pressure gradient edP over the interval. As an alternative or additional step (step 79 of Fig. 5B), based upon the estimated pressure gradient edP over an interval, the processor determines the y^th percentile of the amplitude of edP over the interval (with the y^th percentile typically being as described hereinbelow).

In the method described with reference to Fig. 5A, at minimum-identifying step 80, the processor identifies the minimum of the aortic pressure over the interval, based on the aortic-pressure-indicating signal received from pressure sensor 206 (Fig. 1A). As an alternative or additional step, the processor identifies the X^th percentile of the aortic pressure over this interval (step 81 of Fig. 5B). Typically, the percentile is chosen such that it is close to the minimum arterial pressure but such that in the event that there are any outlying arterial pressure measurements, they are not included. For example, a percentile between the 5^th and the 20^th percentile (e.g., between the 8^th and the 15^th percentile, or approximately the 10^th percentile) can be chosen.

In the method described with reference to Fig. 5A, at comparing step 82, the processor compares the minimum aortic pressure to the peak-to-peak amplitude of edP, e.g., by comparing a ratio of these two quantities to a predetermined threshold. As an alternative or additional step, the y^th percentile of the amplitude of edP is compared to the x^th percentile of the aortic pressure over the interval (step 83 of Fig. 5B). For some applications, a ratio between these two quantities is compared to a threshold.

Typically, the y^th percentile of the amplitude of edP is chosen such that it is close to the full amplitude of edP, but such that in the event that there are any outlying pressure gradient measurements, they are not included. Further typically, the y^th percentile is chosen to correspond to the inverse of X^th percentile of the aortic pressure (and typically such that the y^th percentile is equal to 100 percent minus the x^th percentile), so that if a percentile between the 5^th and the 20^th percentile (e.g., between the 8^th and the 15^th percentile, or approximately the 10^th percentile) is chosen for the x^ percentile, a percentile between the 95^th and the 80^th percentile (e.g., between the 92^nc^ and the 85^th percentile, or approximately the 90^th percentile) is chosen as the y^th percentile of the amplitude of edP.

In general whether method 76 proceeds according to Fig. 5A or 5B, a parameter that is indicative of the amplitude of edP is compared to a parameter that is indicative of the minimum arterial pressure of the interval. In accordance with Fig. 5 A, the actual amplitude of edP and the actual measured minimal arterial pressure are used for the comparison step (step 82). In accordance with Fig. 5B, the yth percentile of edP amplitude is compared to the xth percentile of arterial pressure, in order to reduce the effect of any outliers. Regardless of whether these initial steps are performed according to Fig. 5 A or Fig. 5B, all of the remaining steps typically proceed as described hereinabove with reference to Fig. 5 A.

Typically, a ratio between the parameter that is indicative of the amplitude of edP and the parameter that is indicative of the minimum arterial pressure over the interval is compared to a threshold. As described hereinabove, if the two quantities are not sufficiently close to one another, the processor, at an outputting step 84, outputs an indication that the pump-outlet tube is positionally biased toward the aorta, e.g., as described below with reference to Fig. 6.

On the other hand, if the minimum aortic pressure to the peak-to-peak amplitude of edP are sufficiently close to one another, the processor proceeds to check whether the pumpoutlet tube is positionally biased toward the left ventricle. In some embodiments, to check whether the pump-outlet tube is positionally biased toward the left ventricle, the processor first computes an estimated average current consumed by the motor, over an interval (having a length of around 10 seconds, for example), while rotating the impeller, based on the speed of the motor during the interval, at an average-current-estimating step 87. Next, at another comparing step 89, the processor compares the estimated average current to the actual average current consumed by the motor over the interval, e.g., by comparing a ratio of these two quantities to a predetermined threshold. If the two quantities are not sufficiently close to one another, the processor, at an outputting step 90, outputs an indication that the pump-outlet tube is positionally biased toward the left ventricle, e.g., as described below with reference to Fig. 6. Otherwise, method 76 ends.

In some embodiments, in response to determining that the pump-outlet tube is correctly positioned, the processor outputs an indication of the correct positioning, e.g., as described below with reference to Fig. 6.

Typically, method 76 cannot be accurately executed while the subject’s left ventricle is beating arrhythmically. Hence, typically, the processor is configured to refrain from executing the method in this case. As noted above, in some embodiments, the processor detects an arrhythmia based on a frequency-domain analysis of the aortic pressure signal.

Reference is now made to Fig. 6, which is a schematic illustration of a graph 94 including a positional -bias indicator 93, in accordance with some embodiments of the present disclosure. In some embodiments, the processor computes the positional bias of the pump-outlet tube relative to the aortic valve, e.g., as described above with reference to Fig. 5. Subsequently, the processor displays indicator 93 on display 228 (Fig. 1A). Typically, indicator 93 is displayed for a rolling time period, such as the previous 10 seconds. Typically, in addition to indicator 93, the processor displays (e.g., for the same rolling time period) one or more other indicators such as an indicator of aortic and/or estimated left-ventricular pressure, an indicator of motor current, and/or an indicator of motor speed.

Indicator 93 has a color indicative of the magnitude of the bias. For example, in some embodiments, indicator 93 is intuitively colored in accordance with a traffic light, in that the color varies, depending on the magnitude of the bias, between green (for no significant bias), yellow (for a slight bias), and red (for a large bias). Indicator 93 further has a property indicative of the direction of the bias, i.e., indicative of whether the bias is toward the aorta, is toward the left ventricle, or has no direction (i.e., is insignificant).

For example, in some embodiments, graph 94 has a rolling horizontal axis representing time and a vertical axis representing the direction and magnitude of the bias, and the property of the indicator indicating the direction of the bias includes the vertical position of the indicator. For example, in Fig. 6, for any given moment in time, indicator 93 is displayed at one of five vertical positions: position 0 for no significant bias, position 1 for a slight bias toward the aorta, position 2 for a large bias toward the aorta, position -1 for a slight bias toward the left ventricle, and position -2 for a large bias toward the left ventricle. The indicator is green at position 0, yellow at positions 1 and -1, and red at positions 2 and -2.

Reference is now made to Fig. 7, which shows a flow diagram for a method 96 for detecting an obstruction in pressure-sensing channel 147 (Fig. 1C), in accordance with some embodiments of the present disclosure.

As described above with reference to Fig. 1C, catheter 143 is configured to surround delivery tube 142 within the aorta so as to define pressure-sensing channel 147 between the catheter and delivery tube. Pressure sensor 206 (Fig. 1A) is configured to output a signal indicative of the pressure within the pressure-sensing channel. This pressure is assumed to be the same as the aortic pressure, e.g., for purposes of estimating the pressure within the left ventricle of the subject, as described above with reference to Fig. 3. However, if the pressuresensing channel is obstructed, the pressure in the pressure-sensing channel will differ from the aortic pressure. To address this challenge, the processor is configured to check whether the pressuresensing channel is obstructed. As the present inventors have observed, in the absence of an obstruction, the pressure signal lags the current signal (i.e., the signal representing the current consumed by the motor, shown in Figs. 2B and 2D for example) by around 180 degrees. Hence, the processor checks whether the pressure-sensing channel is obstructed based on the phase difference between the two signals during an interval (having a length of around 10 seconds, for example). In some embodiments, this check is performed continually, e.g., every 1-10 seconds, such as every five seconds.

In particular, the processor first calculates the magnitude of the phase difference at a magnitude-calculating step 98. For example, in some embodiments, the processor computes the Fourier transform of each of the signals. Based on the transforms, the processor identifies the dominant frequency of the signals, and then calculates the phase difference at the dominant frequency.

Next, the processor checks, at a checking step 100, whether the phase difference is close to 180 degrees. (The maximum tolerable deviation from 180 degrees varies between catheters.) If yes, method 96 ends. Otherwise, the processor, at an outputting step 103, outputs an indication that the pressure within the pressure-sensing channel is different from the aortic pressure. For example, in some embodiments, the processor displays a warning regarding a possible obstruction in the pressure-sensing channel and, optionally, ceases to compute and display the estimate of the left ventricular pressure.

Typically, method 96 cannot be accurately executed while the subject’s left ventricle is beating arrhythmically, while the pump-outlet tube is incorrectly positioned, or shortly after a change in the target speed of the motor. Hence, typically, the processor is configured to refrain from executing the method in these cases. As noted above, in some embodiments, the processor detects an arrhythmia based on a frequency-domain analysis of the aortic pressure signal.

ESTIMATING LEFT VENTRICULAR END DIASTOLIC PRESSURE

Reference is now made to Fig. 8A, which plots aortic pressure 52 and left ventricular pressure 54, over several cardiac cycles, when using a left ventricular assist device in accordance with some embodiments of the present disclosure. Reference is also made to Fig. 8B, which plots, over the same cardiac cycles, speed 58 of the motor, in accordance with some embodiments of the present disclosure. Reference is additionally made to Fig. 8C, which plots, over the same cardiac cycles, the acceleration 104 of the motor, in accordance with some embodiments of the present disclosure. (Acceleration 104 is the derivative of speed 58.)

In some embodiments, the processor computes respective estimated left ventricular end diastolic pressures 105 for one or more cycles of the subject’s heart. For each of the cycles, the processor identifies the time tO at which speed 58 was a maximum. The processor then identifies the estimated left ventricular end diastolic pressure 105 for the cycle based on a value of left ventricular pressure 54 (which, in some embodiments, is estimated as described above with reference to Fig. 3) during the interval [tO-c*D tO], c being a predefined constant, which in some embodiments is between 0.2 and 0.4, and D being the approximate duration of the cycle. (As described above, this duration can be estimated based on a Fourier transform of the aortic pressure signal.) Subsequently, the processor displays, on display 228 (Fig. 1 A), the estimated left ventricular end diastolic pressures or a statistic thereof, such as a running average of the estimated left ventricular end diastolic pressure over the most recent N cardiac cycles, where N is any suitable positive integer.

For further details, reference is now additionally made to Fig. 9, which shows a flow diagram for a method 110 for estimating the left ventricular end diastolic pressure for a cardiac cycle, in accordance with some embodiments of the present disclosure.

Typically, given left ventricular pressure 54 and speed 58, the processor first computes acceleration 104 at an acceleration-computing step 111. The processor then checks, at a checking step 112, whether there is a local minimum of acceleration 104 in the interval [tO- c*D tO] . If yes, the processor identifies the estimated left ventricular end diastolic pressure for the cycle based on the time tm of the local minimum. (Typically, if there are multiple local minima, the latest local minimum is selected.) For example, in some embodiments, the processor checks, at another checking step 114, whether the left ventricular pressure is decreasing at tm. If not, the processor, at an estimate-identifying step 116, identifies the estimated left ventricular end diastolic pressure for the cycle as the left ventricular pressure at tm, as depicted in Fig. 8A. Otherwise, the processor, at an alternate estimate-identifying step 118, identifies the estimated left ventricular end diastolic pressure for the cycle as the minimum of the left ventricular pressure between tm and tO.

On the other hand, if there is no local minimum of acceleration 104 between t0-c*D and tO, the processor, at an alternate estimate-identifying step 121, identifies the estimated left ventricular end diastolic pressure for the cycle as the minimum of the left ventricular pressure during the interval. By way of explanation, it is noted that typically, toward the end of diastole, left ventricular pressure slowly increases, and the load on the motor is relatively constant. Subsequently, as the ventricular pressure increases, the load on the motor sharply decreases, and hence, the speed of the motor sharply increases, until the speed reaches its maximum value at tO, which is typically no more than c*D from the end of diastole. Hence, it is expected that the left ventricular end diastolic pressure will be attained during the interval [tO-c*D tO], at the time tm at which the acceleration is at a local minimum (reflecting the relatively constant load on the motor), provided the left ventricular pressure is increasing at tm. If the left ventricular pressure is decreasing at tm, tm is assumed to be prior to the end of diastole; hence, the minimum left ventricular pressure between tm and tO is selected as an estimate for the end diastolic pressure. If no local minimum of the acceleration is identified, the minimum of the left ventricular pressure during [tO-c*D tO] is selected as a reasonable estimate.

It will be appreciated by persons skilled in the art that the present disclosure is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present disclosure includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof that are not in the prior art, which would occur to persons skilled in the art upon reading the foregoing description.

Claims

1. An apparatus for use with a left-ventricular assist device including: a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pumpoutlet tube is disposed within the left ventricle, an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings, a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable, the apparatus comprising: a display; and a processor, configured to: compute respective estimated left ventricular end diastolic pressures for one or more cycles of the heart, by, for each of the cycles: identifying a time tO at which a speed of the motor was a maximum, and identifying the estimated left ventricular end diastolic pressure for the cycle based on a value of a left ventricular pressure of the subj ect during an interval [tO-c*D tO], c being a predefined constant and D being a duration of the cycle, and display, on the display, the estimated left ventricular end diastolic pressures or a statistic thereof.

2. The apparatus according to claim 1, wherein c is between 0.2 and 0.4.

3. The apparatus according to claim 1, wherein identifying the estimated left ventricular end diastolic pressure for the cycle includes identifying the estimated left ventricular end diastolic pressure for the cycle as a minimum of the left ventricular pressure during the interval.

4. The apparatus according to claim 1, wherein the processor is further configured to compute a derivative of the speed, and wherein identifying the estimated left ventricular end diastolic pressure for the cycle includes: identifying, in the interval, another time tm of a local minimum of the derivative, and identifying the estimated left ventricular end diastolic pressure for the cycle based on tm.

5. The apparatus according to claim 4, wherein identifying the estimated left ventricular end diastolic pressure for the cycle based on tm includes: determining that the left ventricular pressure is not decreasing at tm, and in response to the determining, identifying the estimated left ventricular end diastolic pressure for the cycle as the left ventricular pressure at tm.

6. The apparatus according to claim 4, wherein identifying the estimated left ventricular end diastolic pressure for the cycle based on tm includes: determining that the left ventricular pressure is decreasing at tm, and in response to the determining, identifying the estimated left ventricular end diastolic pressure for the cycle as a minimum of the left ventricular pressure between tm and tO.

7. The apparatus according to any one of claims 1-6, wherein the processor is further configured to compute the left ventricular pressure by: computing an estimated pressure gradient between the aorta and the left ventricle, based on a current consumed by the motor while rotating the impeller, and deriving the left ventricular pressure from the estimated pressure gradient.

8. The apparatus according to claim 7, wherein computing the estimated pressure gradient includes: computing a preliminary estimated pressure gradient between the aorta and the left ventricle, based on the current, based on the preliminary estimated pressure gradient, selecting an adjustment type from a group consisting of: a first adjustment type and a second adjustment type, and computing the estimated pressure gradient by adjusting the preliminary estimated pressure gradient per the selected adjustment type.

9. The apparatus according to claim 8, wherein selecting the adjustment type includes: comparing a peak-to-peak amplitude of the preliminary estimated pressure gradient to a peak-to-peak amplitude of an aortic pressure of the subject, and selecting the adjustment type in response to the comparison.

10. The apparatus according to claim 8, wherein the processor is configured to adjust the preliminary estimated pressure gradient per the first adjustment type by: identifying a minimum of the preliminary estimated pressure gradient during a previous cycle of the heart, and subtracting the minimum of the preliminary estimated pressure gradient from the preliminary estimated pressure gradient.

11. The apparatus according to claim 8, wherein the processor is configured to adjust the preliminary estimated pressure gradient per the second adjustment type by adding, to the preliminary estimated pressure gradient, at * P, where P is a mean aortic pressure of the subject over a previous interval and at is a predefined constant.

12. The apparatus according to claim 8, wherein the processor is configured to compute the preliminary estimated pressure gradient by multiplying the current by a predefined constant.

13. The apparatus according to claim 8, wherein the processor is further configured to: determine a peak-to-peak amplitude of the current, and scale up or scale down the peak-to-peak amplitude of the current, prior to computing the preliminary estimated pressure gradient, in response to the peak-to-peak amplitude of the current being less than a first predefined threshold or greater than a second predefined threshold, respectively.

14. A method for use with a left-ventricular assist device including: a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pumpoutlet tube is disposed within the left ventricle, an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings, a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable, the method comprising: computing, by a processor, respective estimated left ventricular end diastolic pressures for one or more cycles of the heart, by, for each of the cycles: identifying a time tO at which a speed of the motor was a maximum, and identifying the estimated left ventricular end diastolic pressure for the cycle based on a value of a left ventricular pressure of the subject during an interval [tO-c*D tO], c being a predefined constant and D being a duration of the cycle; and displaying on a display, by the processor, the estimated left ventricular end diastolic pressures or a statistic thereof.

15. The method according to claim 14, wherein c is between 0.2 and 0.4.

16. The method according to claim 14, wherein identifying the estimated left ventricular end diastolic pressure for the cycle comprises identifying the estimated left ventricular end diastolic pressure for the cycle as a minimum of the left ventricular pressure during the interval.

17. The method according to claim 14, further comprising computing a derivative of the speed, wherein identifying the estimated left ventricular end diastolic pressure for the cycle comprises: identifying, in the interval, another time tm of a local minimum of the derivative; and identifying the estimated left ventricular end diastolic pressure for the cycle based on tm.

18. The method according to claim 17, wherein identifying the estimated left ventricular end diastolic pressure for the cycle based on tm comprises: determining that the left ventricular pressure is not decreasing at tm; and in response to the determining, identifying the estimated left ventricular end diastolic pressure for the cycle as the left ventricular pressure at tm.

19. The method according to claim 17, wherein identifying the estimated left ventricular end diastolic pressure for the cycle based on tm comprises: determining that the left ventricular pressure is decreasing at tm; and in response to the determining, identifying the estimated left ventricular end diastolic pressure for the cycle as a minimum of the left ventricular pressure between tm and tO.

20. The method according to any one of claims 14-19, further comprising computing the left ventricular pressure by: computing an estimated pressure gradient between the aorta and the left ventricle, based on a current consumed by the motor while rotating the impeller, and deriving the left ventricular pressure from the estimated pressure gradient.

21. The method according to claim 20, wherein computing the estimated pressure gradient comprises: computing a preliminary estimated pressure gradient between the aorta and the left ventricle, based on the current; based on the preliminary estimated pressure gradient, selecting an adjustment type from a group consisting of: a first adjustment type and a second adjustment type; and computing the estimated pressure gradient by adjusting the preliminary estimated pressure gradient per the selected adjustment type.

22. The method according to claim 21, wherein selecting the adjustment type comprises: comparing a peak-to-peak amplitude of the preliminary estimated pressure gradient to a peak-to-peak amplitude of an aortic pressure of the subject; and selecting the adjustment type in response to the comparison.

23. The method according to claim 21, wherein, provided the selected adjustment type is the first adjustment type, adjusting the preliminary estimated pressure gradient comprises: identifying a minimum of the preliminary estimated pressure gradient during a previous cycle of the heart; and subtracting the minimum of the preliminary estimated pressure gradient from the preliminary estimated pressure gradient.

24. The method according to claim 21, wherein, provided the selected adjustment type is the second adjustment type, adjusting the preliminary estimated pressure gradient comprises adding, to the preliminary estimated pressure gradient, at * P, where P is a mean aortic pressure of the subject over a previous interval and at is a predefined constant.

25. The method according to claim 21, wherein computing the preliminary estimated pressure gradient comprises computing the preliminary estimated pressure gradient by multiplying the current by a predefined constant.

26. The method according to claim 21, further comprising: determining a peak-to-peak amplitude of the current; and scaling up or scaling down the peak-to-peak amplitude of the current, prior to computing the preliminary estimated pressure gradient, in response to the peak-to-peak amplitude of the current being less than a first predefined threshold or greater than a second predefined threshold, respectively.

27. A computer software product for use with a left-ventricular assist device including: a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pumpoutlet tube is disposed within the left ventricle, an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings, a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable, the computer software product comprising a tangible non-transitory computer-readable medium in which program instructions are stored, which instructions, when read by a processor, cause the processor to: compute respective estimated left ventricular end diastolic pressures for one or more cycles of the heart, by, for each of the cycles: identifying a time tO at which a speed of the motor was a maximum, and identifying the estimated left ventricular end diastolic pressure for the cycle based on a value of a left ventricular pressure of the subject during an interval [tO-c*D tO], c being a predefined constant and D being a duration of the cycle, and display, on a display, the estimated left ventricular end diastolic pressures or a statistic thereof.

28. An apparatus, comprising: a left-ventricular assist device, comprising: a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle; an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube such that the blood exits the pump-outlet tube via the blood-outlet openings; a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section; a drive cable passing through the delivery tube and operatively coupled to the impeller; and a motor configured to rotate the impeller via the drive cable; and a processor, configured to compute an estimated pressure gradient between the aorta and the left ventricle over an interval, based on a variation, over the interval, in a parameter related to the motor as the motor rotates the impeller, wherein a maximal diameter of the impeller is at least 8 mm, such that the variation in the parameter is greater than if the maximal diameter of the impeller were less than 8 mm.

29. The apparatus according to claim 28, wherein the maximal diameter is at least 9 mm.

30. The apparatus according to claim 28, wherein the parameter includes a speed of the motor.

31. The apparatus according to claim 28, wherein a moment of inertia of the motor is less

2 than 5 g-cm , such that the variation in the parameter is greater than if the moment of inertia were at least 5 kg-m .

32. The apparatus according to claim 31, wherein the moment of inertia is less than 2 kg-m².

33. The apparatus according to any one of claims 28-32, wherein the parameter includes a current consumed by the motor.

34. The apparatus according to claim 33, wherein, at least partly because the maximal diameter of the impeller is at least 8 mm, the current increases by at least 0.5 mA for an increase of 1 mmHg in the pressure gradient between the aorta and the left ventricle.

35. The apparatus according to claim 34, wherein the current increases by at least 1 mA for the increase of 1 mmHg in the pressure gradient between the aorta and the left ventricle.

36. The apparatus according to claim 33, wherein the processor is configured to compute the estimated pressure gradient by: computing a preliminary estimated pressure gradient between the aorta and the left ventricle, based on the current, based on the preliminary estimated pressure gradient, selecting an adjustment type from a group consisting of: a first adjustment type and a second adjustment type, and computing the estimated pressure gradient by adjusting the preliminary estimated pressure gradient per the selected adjustment type.

37. The apparatus according to claim 36, wherein selecting the adjustment type includes: comparing a peak-to-peak amplitude of the preliminary estimated pressure gradient to a peak-to-peak amplitude of an aortic pressure of the subject, and selecting the adjustment type in response to the comparison.

38. The apparatus according to claim 36, wherein the processor is configured to adjust the preliminary estimated pressure gradient per the first adjustment type by: identifying a minimum of the preliminary estimated pressure gradient during a previous cycle of the heart, and subtracting the minimum of the preliminary estimated pressure gradient from the preliminary estimated pressure gradient.

39. The apparatus according to claim 36, wherein the processor is configured to adjust the preliminary estimated pressure gradient per the second adjustment type by adding, to the preliminary estimated pressure gradient, at * P, where P is a mean aortic pressure of the subject over a previous interval and at is a predefined constant.

40. The apparatus according to claim 36, wherein the processor is configured to compute the preliminary estimated pressure gradient by multiplying the current by a predefined constant.

41. The apparatus according to claim 36, wherein the processor is further configured to: determine a peak-to-peak amplitude of the current, and scale up or scale down the peak-to-peak amplitude of the current, prior to computing the preliminary estimated pressure gradient, in response to the peak-to-peak amplitude of the current being less than a first predefined threshold or greater than a second predefined threshold, respectively.

42. An apparatus, comprising: a left-ventricular assist device, comprising: a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pump-outlet tube is disposed within the left ventricle; an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings; a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section; a drive cable passing through the delivery tube and operatively coupled to the impeller; and a motor configured to rotate the impeller via the drive cable; and a processor, configured to compute an estimated pressure gradient between the aorta and the left ventricle over an interval, based on a variation, over the interval, in a parameter related to the motor as the motor rotates the impeller, wherein a moment of inertia of the motor is less than 5 kg-m , such that the

2 variation in the parameter is greater than if the moment of inertia were at least 5 kg-m .

43. The apparatus according to claim 42, wherein the moment of inertia is less than 2 kg-m².

44. The apparatus according to claim 42, wherein the parameter includes a speed of the motor.

45. The apparatus according to claim 42, wherein a maximal diameter of the impeller is at least 8 mm, such that the variation in the parameter is greater than if the maximal diameter of the impeller were less than 8 mm.

46. The apparatus according to claim 45, wherein the maximal diameter of the impeller is at least 9 mm.

47. The apparatus according to any one of claims 42-46, wherein the parameter includes a current consumed by the motor.

48. The apparatus according to claim 47, wherein, at least partly because the moment of

2 inertia is less than 5 kg-m , the current increases by at least 0.5 mA for an increase of 1 mmHg in the pressure gradient between the aorta and the left ventricle.

49. The apparatus according to claim 48, wherein the current increases by at least 1 mA for the increase of 1 mmHg in the pressure gradient between the aorta and the left ventricle.

50. The apparatus according to claim 47, wherein the processor is configured to compute the estimated pressure gradient by: computing a preliminary estimated pressure gradient between the aorta and the left ventricle, based on the current, based on the preliminary estimated pressure gradient, selecting an adjustment type from a group consisting of: a first adjustment type and a second adjustment type, and computing the estimated pressure gradient by adjusting the preliminary estimated pressure gradient per the selected adjustment type.

51. The apparatus according to claim 50, wherein selecting the adjustment type includes: comparing a peak-to-peak amplitude of the preliminary estimated pressure gradient to a peak-to-peak amplitude of an aortic pressure of the subject, and selecting the adjustment type in response to the comparison.

52. The apparatus according to claim 50, wherein the processor is configured to adjust the preliminary estimated pressure gradient per the first adjustment type by: identifying a minimum of the preliminary estimated pressure gradient during a previous cycle of the heart, and subtracting the minimum of the preliminary estimated pressure gradient from the preliminary estimated pressure gradient.

53. The apparatus according to claim 50, wherein the processor is configured to adjust the preliminary estimated pressure gradient per the second adjustment type by adding, to the preliminary estimated pressure gradient, at * P, where P is a mean aortic pressure of the subject over a previous interval and at is a predefined constant.

54. The apparatus according to claim 50, wherein the processor is configured to compute the preliminary estimated pressure gradient by multiplying the current by a predefined constant.

55. The apparatus according to claim 50, wherein the processor is further configured to: determine a peak-to-peak amplitude of the current, and scale up or scale down the peak-to-peak amplitude of the current, prior to computing the preliminary estimated pressure gradient, in response to the peak-to-peak amplitude of the current being less than a first predefined threshold or greater than a second predefined threshold, respectively.

56. An apparatus for use with a left-ventricular assist device including: a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pumpoutlet tube is disposed within the left ventricle, an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings, a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable, the apparatus comprising: a display; and a processor, configured to: for a first interval, compute an estimated pressure in the left ventricle based on a parameter related to the motor as the motor rotates the impeller during the first interval, and displaying the estimated pressure in the left ventricle on the display, determine that the pump-outlet tube was at least partly collapsed during a second interval following the first interval, and drive the display not to display the estimated pressure in the left ventricle, during the second interval.

57. The apparatus according to claim 56, wherein the processor is configured to determine that the pump-outlet tube was at least partly collapsed in response to the parameter changing more slowly following the first interval, relative to during the first interval.

58. The apparatus according to claim 56, wherein the parameter includes a current consumed by the motor.

59. The apparatus according to claim 58, wherein the processor is configured to compute the estimated pressure in the left ventricle by: computing an estimated pressure gradient between the aorta and the left ventricle, based on the current, and deriving the estimated pressure in the left ventricle from the estimated pressure gradient.

60. The apparatus according to claim 59, wherein the processor is configured to compute the estimated pressure gradient by: computing a preliminary estimated pressure gradient between the aorta and the left ventricle, based on the current, based on the preliminary estimated pressure gradient, selecting an adjustment type from a group consisting of: a first adjustment type and a second adjustment type, and computing the estimated pressure gradient by adjusting the preliminary estimated pressure gradient per the selected adjustment type.

61. The apparatus according to claim 60, wherein the processor is configured to select the adjustment type by: comparing a peak-to-peak amplitude of the preliminary estimated pressure gradient to a peak-to-peak amplitude of an aortic pressure of the subject, and selecting the adjustment type in response to the comparison.

62. The apparatus according to claim 60, wherein the processor is configured to adjust the preliminary estimated pressure gradient per the first adjustment type by: identifying a minimum of the preliminary estimated pressure gradient during a previous cycle of the heart, and subtracting the minimum of the preliminary estimated pressure gradient from the preliminary estimated pressure gradient.

63. The apparatus according to claim 60, wherein the processor is configured to adjust the preliminary estimated pressure gradient per the second adjustment type by adding, to the preliminary estimated pressure gradient, at * P, where P is a mean aortic pressure of the subject over a previous interval and at is a predefined constant.

64. The apparatus according to claim 60, wherein the processor is configured to compute the preliminary estimated pressure gradient by multiplying the current by a predefined constant.

65. The apparatus according to claim 64, wherein the processor is further configured to: determine whether a minimum of the adjusted estimate is less than a third predefined threshold, and in response to determining that the minimum of the adjusted estimate is less than the third predefined threshold, for a subsequent first interval, compute the preliminary estimated pressure gradient by multiplying the adjusted current by the predefined constant and by another predefined constant that is less than one.

66. The apparatus according to claim 60, wherein the processor is further configured to: determine a peak-to-peak amplitude of the current, and scale up or scale down the peak-to-peak amplitude of the current, prior to computing the preliminary estimated pressure gradient, in response to the peak-to-peak amplitude of the current being less than a first predefined threshold or greater than a second predefined threshold, respectively.

67. A method for use with a left-ventricular assist device including: a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pumpoutlet tube is disposed within the left ventricle, an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings, a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable, the method comprising: for a first interval, computing, by a processor, an estimated pressure in the left ventricle based on a parameter related to the motor as the motor rotates the impeller during the first interval; determining, by the processor, that the pump-outlet tube was at least partly collapsed during a second interval following the first interval; and using the processor, driving the display to display the estimated pressure during the first interval, and not to display estimated pressure in the left ventricle during the second interval.

68. The method according to claim 67, wherein determining that the pump-outlet tube was at least partly collapsed comprises determining that the pump-outlet tube was at least partly collapsed in response to the parameter changing more slowly following the first interval, relative to during the first interval.

69. The method according to claim 67, wherein the parameter includes a current consumed by the motor.

70. The method according to claim 69, wherein computing the estimated pressure in the left ventricle comprises: computing an estimated pressure gradient between the aorta and the left ventricle, based on the current; and deriving the estimated pressure in the left ventricle from the estimated pressure gradient.

71. The method according to claim 70, wherein computing the estimated pressure gradient comprises: computing a preliminary estimated pressure gradient between the aorta and the left ventricle, based on the current; based on the preliminary estimated pressure gradient, selecting an adjustment type from a group consisting of: a first adjustment type and a second adjustment type; and computing the estimated pressure gradient by adjusting the preliminary estimated pressure gradient per the selected adjustment type.

72. The method according to claim 71, wherein selecting the adjustment type comprises: comparing a peak-to-peak amplitude of the preliminary estimated pressure gradient to a peak-to-peak amplitude of an aortic pressure of the subject; and selecting the adjustment type in response to the comparison.

73. The method according to claim 71, wherein, provided the selected adjustment type is the first adjustment type, adjusting the preliminary estimated pressure gradient comprises: identifying a minimum of the preliminary estimated pressure gradient during a previous cycle of the heart; and subtracting the minimum of the preliminary estimated pressure gradient from the preliminary estimated pressure gradient.

74. The method according to claim 71, wherein, provided the selected adjustment type is the second adjustment type, adjusting the preliminary estimated pressure gradient comprises adding, to the preliminary estimated pressure gradient, at * P, where P is a mean aortic pressure of the subject over a previous interval and at is a predefined constant.

75. The method according to claim 71, wherein computing the preliminary estimated pressure gradient comprises computing the preliminary estimated pressure gradient by multiplying the current by a predefined constant.

76. The method according to claim 75, further comprising: determining whether a minimum of the adjusted estimate is less than a third predefined threshold; and in response to determining that the minimum of the adjusted estimate is less than the third predefined threshold, for a subsequent first interval, computing the preliminary estimated pressure gradient by multiplying the adjusted current by the predefined constant and by another predefined constant that is less than one.

77. The method according to claim 71, further comprising: determining a peak-to-peak amplitude of the current; and scaling up or scaling down the peak-to-peak amplitude of the current, prior to computing the preliminary estimated pressure gradient, in response to the peak-to-peak amplitude of the current being less than a first predefined threshold or greater than a second predefined threshold, respectively.

78. A computer software product for use with a left-ventricular assist device including: a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pumpoutlet tube is disposed within the left ventricle, an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings, a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable, the computer software product comprising a tangible non-transitory computer-readable medium in which program instructions are stored, which instructions, when read by a processor, cause the processor to: for a first interval, compute an estimated pressure in the left ventricle based on a parameter related to the motor as the motor rotates the impeller during the first interval, determine that the pump-outlet tube was at least partly collapsed during a second interval following the first interval, driving the display to display the estimated pressure during the first interval, and not to display an estimate of pressure in the left ventricle during the second interval.

79. An apparatus for use with a left-ventricular assist device including: a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pumpoutlet tube is disposed within the left ventricle, an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings, a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable, the apparatus comprising: a display; and a processor, configured to: for a first interval, compute an estimated pressure in the left ventricle based on a parameter related to the motor as the motor rotates the impeller during the first interval, determine that the pump-outlet tube was at least partly collapsed following the first interval, in response to determining that the pump-outlet tube was at least partly collapsed, compute an adjusted estimate of the pressure, which is continuous with the estimated pressure, for a second interval following the first interval, and display the estimated pressure and the adjusted estimate of the pressure on the display.

80. The apparatus according to claim 79, wherein the processor is configured to determine that the pump-outlet tube was at least partly collapsed in response to the parameter changing more slowly following the first interval, relative to during the first interval.

81. The apparatus according to claim 79, wherein the processor is configured to compute the estimated pressure in the left ventricle by: computing an estimated pressure gradient between the aorta and the left ventricle, and deriving the estimated pressure in the left ventricle from the estimated pressure gradient, and wherein the processor is configured to determine that the pump-outlet tube was at least partly collapsed in response to the estimated pressure gradient exceeding a predefined threshold value for a predefined threshold duration.

82. The apparatus according to claim 79, wherein the processor is configured to compute the adjusted estimate of the pressure based on a predefined set of adjustment parameters describing an expected change in the pressure over time.

83. The apparatus according to any one of claims 79-82, wherein the parameter includes a current consumed by the motor.

84. The apparatus according to claim 83, wherein the processor is configured to compute the estimated pressure in the left ventricle by: computing an estimated pressure gradient between the aorta and the left ventricle, based on the current, and deriving the estimated pressure in the left ventricle from the estimated pressure gradient.

85. The apparatus according to claim 84, wherein the processor is configured to compute the estimated pressure gradient by: computing a preliminary estimated pressure gradient between the aorta and the left ventricle, based on the current, based on the preliminary estimated pressure gradient, selecting an adjustment type from a group consisting of: a first adjustment type and a second adjustment type, and computing the estimated pressure gradient by adjusting the preliminary estimated pressure gradient per the selected adjustment type.

86. The apparatus according to claim 85, wherein the processor is configured to select the adjustment type by: comparing a peak-to-peak amplitude of the preliminary estimated pressure gradient to a peak-to-peak amplitude of an aortic pressure of the subject, and selecting the adjustment type in response to the comparison.

87. The apparatus according to claim 85, wherein the processor is configured to adjust the preliminary estimated pressure gradient per the first adjustment type by: identifying a minimum of the preliminary estimated pressure gradient during a previous cycle of the heart, and subtracting the minimum of the preliminary estimated pressure gradient from the preliminary estimated pressure gradient.

88. The apparatus according to claim 85, wherein the processor is configured to adjust the preliminary estimated pressure gradient per the second adjustment type by adding, to the preliminary estimated pressure gradient, at * P, where P is a mean aortic pressure of the subject over a previous interval and at is a predefined constant.

89. The apparatus according to claim 85, wherein the processor is configured to compute the preliminary estimated pressure gradient by multiplying the current by a predefined constant.

90. The apparatus according to claim 89, wherein the processor is further configured to: determine whether a minimum of the adjusted estimate is less than a third predefined threshold, and in response to determining that the minimum of the adjusted estimate is less than the third predefined threshold, for a subsequent first interval, compute the preliminary estimated pressure gradient by multiplying the adjusted current by the predefined constant and by another predefined constant that is less than one.

91. The apparatus according to claim 85, wherein the processor is further configured to: determine a peak-to-peak amplitude of the current, and scale up or scale down the peak-to-peak amplitude of the current, prior to computing the preliminary estimated pressure gradient, in response to the peak-to-peak amplitude of the current being less than a first predefined threshold or greater than a second predefined threshold, respectively.

92. A method for use with a left-ventricular assist device including: a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pumpoutlet tube is disposed within the left ventricle, an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings, a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable, the method comprising: for a first interval, computing, by a processor, an estimated pressure in the left ventricle based on a parameter related to the motor as the motor rotates the impeller during the first interval; determining, by the processor, that the pump-outlet tube was at least partly collapsed following the first interval; in response to determining that the pump-outlet tube was at least partly collapsed, computing, by the processor, an adjusted estimate of the pressure, which is continuous with the estimated pressure, for a second interval following the first interval; and displaying on a display, by the processor, the estimated pressure and the adjusted estimate of the pressure.

93. The method according to claim 92, wherein determining that the pump-outlet tube was at least partly collapsed comprises determining that the pump-outlet tube was at least partly collapsed in response to the parameter changing more slowly following the first interval, relative to during the first interval.

94. The method according to claim 92, wherein computing the estimated pressure in the left ventricle comprises: computing an estimated pressure gradient between the aorta and the left ventricle; and deriving the estimated pressure in the left ventricle from the estimated pressure gradient, and wherein determining that the pump-outlet tube was at least partly collapsed comprises determining that the pump-outlet tube was at least partly collapsed in response to the estimated pressure gradient exceeding a predefined threshold value for a predefined threshold duration.

95. The method according to claim 92, wherein computing the adjusted estimate of the pressure comprises computing the adjusted estimate of the pressure based on a predefined set of adjustment parameters describing an expected change in the pressure over time.

96. The method according to any one of claims 92-95, wherein the parameter includes a current consumed by the motor.

97. The method according to claim 96, wherein computing the estimated pressure in the left ventricle comprises: computing an estimated pressure gradient between the aorta and the left ventricle, based on the current; and deriving the estimated pressure in the left ventricle from the estimated pressure gradient.

98. The method according to claim 97, wherein computing the estimated pressure gradient comprises: computing a preliminary estimated pressure gradient between the aorta and the left ventricle, based on the current; based on the preliminary estimated pressure gradient, selecting an adjustment type from a group consisting of: a first adjustment type and a second adjustment type; and computing the estimated pressure gradient by adjusting the preliminary estimated pressure gradient per the selected adjustment type.

99. The method according to claim 98, wherein selecting the adjustment type comprises: comparing a peak-to-peak amplitude of the preliminary estimated pressure gradient to a peak-to-peak amplitude of an aortic pressure of the subject; and selecting the adjustment type in response to the comparison.

100. The method according to claim 98, wherein, provided the selected adjustment type is the first adjustment type, adjusting the preliminary estimated pressure gradient comprises: identifying a minimum of the preliminary estimated pressure gradient during a previous cycle of the heart; and subtracting the minimum of the preliminary estimated pressure gradient from the preliminary estimated pressure gradient.

101. The method according to claim 98, wherein, provided the selected adjustment type is the second adjustment type, adjusting the preliminary estimated pressure gradient comprises adding, to the preliminary estimated pressure gradient, at * P, where P is a mean aortic pressure of the subject over a previous interval and at is a predefined constant.

102. The method according to claim 98, wherein computing the preliminary estimated pressure gradient comprises computing the preliminary estimated pressure gradient by multiplying the current by a predefined constant.

103. The method according to claim 102, further comprising: determining whether a minimum of the adjusted estimate is less than a third predefined threshold; and in response to determining that the minimum of the adjusted estimate is less than the third predefined threshold, for a subsequent first interval, computing the preliminary estimated pressure gradient by multiplying the adjusted current by the predefined constant and by another predefined constant that is less than one.

104. The method according to claim 98, further comprising: determining a peak-to-peak amplitude of the current; and scaling up or scaling down the peak-to-peak amplitude of the current, prior to computing the preliminary estimated pressure gradient, in response to the peak-to-peak amplitude of the current being less than a first predefined threshold or greater than a second predefined threshold, respectively.

105. A computer software product for use with a left-ventricular assist device including: a pump-outlet tube shaped to define one or more blood-outlet openings and configured for insertion, through an aorta of a subject, into a left ventricle of a heart of the subject such that the blood-outlet openings are disposed within the aorta and a distal section of the pumpoutlet tube is disposed within the left ventricle, an impeller disposed within the distal section of the pump-outlet tube and configured to pump blood of the subject proximally through the pump-outlet tube, such that the blood exits the pump-outlet tube via the blood-outlet openings, a delivery tube configured to extend, from outside a body of the subject, through the pump-outlet tube to the distal section, a drive cable passing through the delivery tube and operatively coupled to the impeller, and a motor configured to rotate the impeller via the drive cable, the computer software product comprising a tangible non-transitory computer-readable medium in which program instructions are stored, which instructions, when read by a processor, cause the processor to: for a first interval, compute an estimated pressure in the left ventricle based on a parameter related to the motor as the motor rotates the impeller during the first interval, determine that the pump-outlet tube was at least partly collapsed following the first interval, in response to determining that the pump-outlet tube was at least partly collapsed, compute an adjusted estimate of the pressure, which is continuous with the estimated pressure, for a second interval following the first interval, and display the estimated pressure and the adjusted estimate of the pressure on a display.