HK40057627B - Lead condition testing in an implanted cardiac device - Google Patents

Description

Lead condition testing in implantable cardiac devices

Related application

This application claims priority to U.S. Provisional Patent Application No. 62/957,245, filed January 5, 2020, based on 35 USC §119(e), the contents of which are incorporated herein by reference in their entirety.

Technical Field and Background Art of this Invention

In some embodiments, the present invention relates to the assessment of lead condition and/or lead integrity in implanted devices, and more specifically, but not exclusively, to impedance measurement in implanted devices including defibrillation leads and one or more non-defibrillation leads.

Charles D. Swerdlow and Paul A. Friedman’s paper, entitled “Advanced ICD Troubleshooting: Part II” (Pacing Clin Electrophysiol.; 2006; 29(1): 70–96), discloses: “High-voltage impedance. In the venous system, the impulse path impedance is typically 25 to 75 Ω. Values outside this range indicate a conductor defect (high impedance) or an insulation fault/short circuit (low impedance). Regular assessment of the impedance of the high-voltage electrode using weak test pulses may detect a loss of lead integrity before inappropriate or ineffective treatment occurs. In Medtronic and Guidant ICDs, painless pulses are automatically sent periodically to create a trend graph. In St. Jude ICDs, through The impedance of the high-voltage lead is assessed using a 12V test pulse delivered via a programmer command. The patient will feel this pulse, which may be uncomfortable. The high-voltage impedance measured by a weak pulse correlates well with that measured by a high-energy shock [43, 44]. In the Gatten ICD, the impedance recorded without pain is comparable to that recorded during a high-voltage shock. In earlier Medtronic ICDs, the pulse traveled between the lead tip and the distal coil, resulting in a nominal low-voltage impedance of 11 to 20 Ω, significantly lower than that of a high-energy shock. If a proximal coil is present, its integrity is not assessed. The Marquis (trade name; Medtronic) The ICD and newer models of ^TM report independent near-end and far-end coil impedances that are very close to the impedance of a high-voltage shock. When a conductor defect is suspected, a full-output impulse may be required to assess the conductor integrity. Low-energy pulses may not detect partial insulation defects, and these low-energy pulses will not provide sufficient current to activate the high-output protection function for short circuits (see below)... (pp. 8-9).

"Protect the ICD from high voltage and short circuits. Low impedance on the impact electrode indicates insulation failure, which diverts the impact current from the heart. It can generate a peak current so high that the ICD's output circuit fails due to electrical overstress[58]. For example, an insulation failure in the bag can cause a short circuit from the high-voltage coil to the tank with a resistance of 8. A maximum output (about 800V) impact can cause a peak current of 100A in the high-voltage output circuit, resulting in a catastrophic failure[59]. A short circuit between two active intracardiac electrodes of opposite polarity can have the same effect. To prevent components from being overstressed, If the current in the defibrillation path is too high, modern ICDs will immediately stop the impulse pulse, thus protecting the output circuit. Depending on the manufacturer, this corresponds to a series conductor impedance of 15 to 20 Ω. It is speculated that the short circuit diverts the current from the heart, thus preventing the shock from terminating the VT/VF. In addition to protecting the generator, this function also has safety features. A simultaneous insulation failure in the rate sensing of the RV conductor and the high-voltage components could lead to over-induction. Diverting the resulting inappropriate shock prevents unnecessary suffering. Furthermore, it can prevent fatal arrhythmias caused by a weak shock delivered during a vulnerable period when there is no effective way to save the patient [60] (see Figure 8) (p. 14).

Summary of the Invention

According to one aspect of some embodiments of the present invention, a method is provided for testing the condition of leads in an implantable cardiac device including a first defibrillation lead and a second non-defibrillation lead, the method comprising: measuring the impedance between the first defibrillation lead and the second non-defibrillation lead by applying a test pulse; and determining the condition of at least one of the defibrillation lead and the non-defibrillation lead based on the measured impedance value.

In some embodiments, a second non-defibrillation lead is configured to apply cardiac contractile modulation stimulation.

In some embodiments, a test pulse is applied during the application of cardiac contractile modulation stimulation.

In some embodiments, the test pulse is applied during the ventricular refractory period, either before or after the application of cardiac contractile modulation stimulation.

In some embodiments, the defibrillation lead includes a coil, and the non-defibrillation lead includes a loop electrode and a tip electrode; and the impedance measurement step includes measuring between at least one of the following: the coil and the loop electrode; and the coil and the tip electrode.

In some embodiments, the condition of at least one of the defibrillation leads and the non-defibrillation leads is determined by one or more of the following methods: comparing the impedance value with one or more of the following: a lookup table; one or more previously measured values; one or more predefined values.

In some embodiments, the method includes performing the measurement once a day.

In some embodiments, the method includes issuing an alarm regarding the condition of the conductor.

In some embodiments, determining the condition of the conductor includes determining at least one of the following: conductor breakage, conductor displacement, conductor insulation, conductor connectivity, and conductor deformation.

In some embodiments, at least a portion of the first lead and at least a portion of the second lead are implanted to contact the wall of the right ventricle of the heart.

In some embodiments, the defibrillation lead includes a coil, a loop electrode, and a terminal electrode; the non-defibrillation lead includes a loop electrode and a terminal electrode; and measuring impedance includes measuring the inter-lead impedance between one of the coil, loop electrode, and terminal electrode of the defibrillation lead and one of the loop electrode and terminal electrode of the non-defibrillation lead.

In some embodiments, the non-defibrillation lead includes a cardiac contractile modulation lead or a pacing lead.

According to one aspect of some embodiments of the present invention, an implantable cardiac device is provided, comprising: a first defibrillation lead including a coil, a loop electrode, and a terminal electrode; a second non-defibrillation lead including a loop electrode and a terminal electrode; and circuitry for controlling and activating the coil and the electrode, the circuitry including at least one grounded resistor electrically connected to the second non-defibrillation lead; wherein the circuitry is configured to measure a current across the grounded resistor in response to an applied test pulse to obtain an indication of the condition of at least the first defibrillation lead or a portion thereof.

In some embodiments, the circuitry is at least partially disposed within the housing of the cardiac device, with wires extending from the housing.

In some embodiments, the current measured across the grounding resistor in response to an applied test pulse is used to calculate the impedance between the coil and the housing of the device.

In some embodiments, the circuit is configured to use a predetermined pre-determined linearizing factor to calculate the impedance between the coil and the housing of the device.

In some embodiments, the circuit is programmed to time the test pulse during the expected total refractory period of a cardiac cycle.

In some embodiments, the non-defibrillation lead is a cardiac contractile modulation lead, and the circuit is programmed to time the measurement of current on the grounding resistor during the application of a cardiac contractile modulation signal.

According to one aspect of some embodiments of the present invention, a method is provided for evaluating the condition of a lead in an implantable cardiac device, the implantable cardiac device comprising: a defibrillation lead having a coil; and at least one non-defibrillation lead having at least one electrode, the method comprising: applying (also referred to as "first application") a test pulse to measure a reference impedance between the defibrillation coil and a device housing; and applying (also referred to as "second application") a test pulse to measure a reference impedance between the electrode of the non-defibrillation lead and the defibrillation coil; periodically applying (also referred to as "third application") a test pulse to measure the impedance between the electrode of the non-defibrillation lead and the defibrillation coil; and estimating a current impedance between the coil and the device housing based on the difference between one or both of the currently measured impedance levels measured at the third application and the reference measurements, to evaluate the condition of the defibrillation lead.

In some embodiments, the third application is performed more frequently than the first and second applications.

In some embodiments, the periodic application includes applying it once every 24 hours.

According to one aspect of some embodiments of the present invention, a method is provided for testing the integrity of a lead in an implantable cardiac device comprising at least two electrodes, the method comprising: applying a test pulse having a selected duration and voltage during the total ventricular refractory period of a cardiac cycle; measuring the impedance between the at least two electrodes and/or between the electrodes and the device housing; and determining the condition of the lead based on the measured impedance value.

In some embodiments, one of the at least two electrodes includes a defibrillation coil.

In some embodiments, one of the at least two electrodes includes a ring electrode or an end electrode.

According to one aspect of some embodiments of the present invention, a method is provided for evaluating the condition of leads in an implantable cardiac device comprising a defibrillation lead and at least one non-defibrillation lead, the method comprising: measuring the impedance between the defibrillation lead and the non-defibrillation lead by conducting current via a first electrical path of the device circuitry; checking whether the patient feels or experiences pain during the measurement; and if the patient feels or experiences pain during the initial measurement, measuring the impedance between the defibrillation lead and the non-defibrillation lead by conducting current via a second electrical path of the device circuitry.

According to one aspect of some embodiments of the present invention, a method is provided for evaluating the condition of a lead in an implantable cardiac device including a defibrillation coil and at least two electrodes, the method comprising: measuring the impedance between the coil and a first electrode; measuring the impedance between the coil and a second electrode or between the first and second electrodes; and evaluating the integrity of the coil, the first and second electrodes based on the measured impedance values.

In some embodiments, the first and second electrodes are implanted in or in contact with the heart tissue.

According to one aspect of some embodiments of the present invention, an implantable cardiac device is provided, the device comprising: a first defibrillation lead; a second non-defibrillation lead; and circuitry for controlling the lead and for measuring impedance, the circuitry being configured to: apply a test pulse to measure the impedance between the first defibrillation lead and the second non-defibrillation lead; and determine the condition of at least one of the defibrillation lead and the non-defibrillation lead based on the measured impedance value.

In some embodiments, the second non-defibrillation lead is configured to apply cardiac contractility modulation stimulation.

In some embodiments, the circuit is configured to time the test pulse during the application of cardiac contractile modulation stimulation via the second non-defibrillation lead.

In some embodiments, the circuit is configured to time the test pulse during the ventricular refractory period.

In some embodiments, the defibrillation lead includes a coil, and the non-defibrillation lead includes a loop electrode and a terminal electrode, wherein the impedance is measured between at least one of the following: the coil and the loop electrode; and the coil and the terminal electrode.

In some embodiments, the circuit is configured to determine the condition of at least one of the defibrillation leads and the non-defibrillation leads by comparing the measured impedance with one or more of the following: a lookup table; one or more previously measured impedance values; or one or more predefined impedance values.

In some embodiments, the circuit is configured to time the test pulses and perform a measurement every 24 hours.

In some embodiments, the circuit is configured to generate and issue an alarm regarding a determined wire condition.

In some embodiments, the determined conductor condition includes at least one of the following: conductor breakage, conductor detachment, conductor insulation failure, conductor connectivity issues, and conductor deformation.

In some embodiments, the defibrillation lead includes a coil, a loop electrode, and a terminal electrode, and the non-defibrillation lead includes a loop electrode and a terminal electrode; and the impedance is measured between one of the coil, loop electrode, and terminal electrode of the defibrillation lead and one of the loop electrode and terminal electrode of the non-defibrillation lead.

In some embodiments, the non-defibrillation lead includes a cardiac systolic modulation (CCM) lead or a pacing lead.

According to one aspect of some embodiments of the present invention, an implantable cardiac device is provided, the device comprising:

case;

A defibrillation lead having a coil, the defibrillation lead extending from the housing;

A non-defibrillation lead having at least one electrode, the non-defibrillation lead extending from the housing; and circuitry for controlling and activating the defibrillation lead and the non-defibrillation lead, and for measuring impedance, wherein the circuitry is configured to:

A test pulse is applied between the coil and the housing of the defibrillation lead to measure the baseline impedance;

A test pulse is applied between at least one electrode of the non-defibrillator lead and the coil of the defibrillator lead to measure a reference impedance;

Test pulses are periodically applied to measure the impedance between at least one electrode of the non-defibrillator lead and the coil of the defibrillator lead;

The current impedance between the coil of the defibrillation lead and the housing is estimated based on the difference between a currently measured impedance level measured between the at least one electrode of the non-defibrillation lead and the coil of the defibrillation lead, and one or both of the measured values of the reference impedance; and

The condition of the defibrillation leads is assessed based on the estimated current impedance.

In some embodiments, the circuit is configured to apply the test pulse at least every 24 hours to measure the impedance between at least one electrode of the non-defibrillator lead and the coil of the defibrillator lead.

Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. While similar or equivalent methods and materials to those described herein may be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including its definitions, shall prevail. Furthermore, materials, methods, and embodiments are illustrative only and are not intended to impose necessary limitations.

Implementation of the methods and/or systems of embodiments of the present invention may involve manual, automatic, or a combination thereof to perform or complete selected tasks. Furthermore, the actual instruments and equipment of embodiments of the methods and/or systems according to the present invention may use operating systems, hardware, software, or firmware, or combinations thereof, to implement several selected tasks.

For example, hardware for performing a selected task according to some embodiments of the present invention can be implemented as a chip or circuit. As software, the selected task according to some embodiments of the present invention can be implemented as a plurality of software instructions executed by a computer using any suitable operating system. In exemplary embodiments of the present invention, one or more tasks according to exemplary embodiments of the methods and/or systems described herein are performed by a data processor, such as a computing platform for executing a plurality of instructions. Optionally, the data processor includes volatile memory for storing instructions and/or data and/or non-volatile memory for storing instructions and/or data, such as a magnetic hard disk and/or removable media.

Brief description of several views in the attached diagram

Some embodiments of the invention are described herein by way of example only, with reference to the accompanying drawings. Referring now specifically to the drawings, it is emphasized that the details shown are by way of example and for the purpose of illustrative discussion of embodiments of the invention. In this regard, the description taken in conjunction with the drawings will be apparent to those skilled in the art to how embodiments of the invention can be practiced.

In the attached diagram:

Figure 1A is a schematic diagram of an implantable device including a defibrillation lead and at least one cardiac contractility modulation lead according to some embodiments;

Figure 1B schematically illustrates a cross-measurement of impedance between components of two leads of an implantable device according to some embodiments;

Figure 1C is a schematic diagram of impedance measurement in a cardiac device including two leads according to some embodiments;

Figures 2A to 2D are flowcharts of a general method for assessing lead condition by measuring impedance in a cardiac device, according to some embodiments.

Figure 3 is a schematic diagram of the circuitry used for impedance measurement in an implantable pulse generator device (IPG).

Figure 4 is a schematic diagram of a circuit suitable for performing impedance measurement in a device including a defibrillation lead and at least one cardiac contractile modulation lead, according to some embodiments.

Figure 5 is a schematic diagram of a circuit adapted to perform impedance measurement in a device including a defibrillation lead and at least one pacing lead, according to some embodiments.

Figure 6 is a schematic diagram illustrating the components of an implantable ICD/cardiac contractility modulation device according to some embodiments;

Figure 7 is an example of an impedance lookup table for evaluating conductor condition according to some embodiments;

Figure 8 is a flowchart of a method for estimating the connection status in a device including a defibrillation coil and two electrodes, according to some embodiments; and

Figure 9 is a graphical representation of the cardiac cycle relative to the timing of the application of cardiac contractile modulation stimulation and the test pulse for impedance measurement, according to some embodiments.

Detailed Implementation

In some embodiments, the present invention relates to the assessment of lead integrity in implanted devices, and more specifically, but not exclusively, to impedance measurement in implanted cardiac devices comprising defibrillation leads and one or more non-defibrillation leads. In some embodiments, the device includes a defibrillation coil and one or more electrodes.

Some embodiments involve broadly assessing the integrity of at least a portion of the circuitry of an implanted cardiac device while substantially avoiding or reducing pain and/or sensation in the patient. In some embodiments, the condition of one or more leads of the device (at least partially located inside the heart) is assessed by measuring impedance, for example, measuring the impedance between components of a single lead and/or between components of two different leads.

One aspect of some embodiments involves reducing or avoiding sensation and/or pain to the patient during impedance measurements by avoiding measurement pathways that significantly stimulate nerves. Optionally, direct and/or indirect stimulation of nerves is avoided or reduced. In some embodiments, the measurement pathway and/or signal amplitude are selected to reduce or prevent nerve stimulation. Reducing or avoiding nerve stimulation may include reducing or avoiding stimulation of the sympathetic and/or parasympathetic nervous systems.

In some embodiments, such as in devices comprising two or more leads, various measurement paths are available (e.g., various cross-measurement paths between assemblies of two different leads). Optionally, if measurement via a certain path causes pain or sensation in the patient, an alternative path can be selected.

One aspect of some embodiments relates to assessing the condition of at least one implanted lead by measuring the impedance between a defibrillation lead and a non-defibrillation lead. In some embodiments, the non-defibrillation lead includes a pacing lead. In some embodiments, the non-defibrillation lead includes a cardiac contractility modulation lead. In some embodiments, the non-defibrillation lead includes a sensing lead.

In some embodiments, at least a portion of each lead is implanted inside the heart, such as in the right ventricle. Alternatively, the lead is implanted within the muscular tissue of the heart. Alternatively, each lead extends from inside the heart to an external device that generates the applied signal and is optionally implanted in the subclavian region.

In some embodiments, each lead includes one or more of the following: a coil, a loop electrode, and an end electrode. In some embodiments, cross-impedance measurements are performed between pairs of components, whereby a first component of the pair is configured on a defibrillation lead, while a second component of the pair is configured on a non-defibrillation lead.

In some embodiments, the cardiac device includes more than two leads, such as defibrillation leads and two non-defibrillation leads (e.g., cardiac systolic modulation leads, pacing leads), and various combinations for performing impedance measurements, such as between the first and second leads, between the first and third leads, and between the second and third leads. Optionally, if the initially selected measurement path causes pain or is felt by the patient, sequential cross-measurements are performed. Optionally, sequential cross-measurements are performed so that one or more measurement results are used as a reference value for another measurement. Optionally, sequential measurements are performed to assess which of the three components (e.g., coils and two electrodes) has a defect or connectivity problem.

Potential advantages of cross-measurement (e.g., performing cross-measurement between at least two leads) may include avoiding measuring impedance in the defibrillation leads (e.g., the lead coil) and the device itself (coil-to-can configuration). Avoiding such measurements, at least during impedance measurement, may help reduce pain or sensation in the patient, especially when the coil-to-can path passes through sensory nerves.

In some embodiments, impedance is measured by applying a test pulse. Based on the obtained impedance value, the condition of the conductor can be assessed. Some examples of conductor conditions that can be detected based on the measured impedance value include conductor breakage, conductor detachment, insulation defects, continuity defects, conductor severance, and/or other conditions related to conductor integrity, conductivity, deformation, changes in conductor material properties, etc.

In some examples, the assessment of conductor condition via impedance measurement is performed periodically and/or at preset times and/or at preset intervals, such as every 5 minutes, every 50 minutes, every 30 minutes, every hour, every 4 hours, every 12 hours, every 24 hours, every 2 days, every week, or at longer or shorter intervals.

One aspect of some embodiments relates to an implantable ICD/cardiac contractile modulation device (the device includes: a defibrillation lead; a cardiac contractile modulation lead; and circuitry configured to apply a test pulse during the application of a cardiac contractile modulation signal to measure the impedance between the two leads). In some embodiments, because the cardiac contractile modulation lead is suitable for applying a high-voltage signal, the test pulse for impedance measurement can be applied at a relatively high voltage, such as between 8-16V, 5-10V, 6-12V, 4-8V, or intermediate, higher or lower values. In some embodiments, the duration of the applied test pulse is as short as 6 microseconds, 10 microseconds, 8 microseconds, 5 microseconds, or intermediate, longer or shorter time periods. A potential advantage of short test pulses may include reduced pain, or even no sensation from the patient.

One aspect of some embodiments involves applying a test pulse to measure impedance during the ventricular refractory period. Alternatively, the test pulse may be applied during the absolute refractory period. Potential advantages of applying the test pulse during the ventricular refractory period may include improved safety of the implanted device, as no new action potential is induced, and therefore the applied pulse is less likely to stimulate unwanted contractions.

In some embodiments, a test pulse for measuring impedance is applied during the ventricular refractory period, but not during the application of a cardiac contractile modulation signal.

In some embodiments, the test pulse does not induce a therapeutic effect. In some embodiments, parameters of the test pulse (e.g., voltage, duration, and time of application) are selected to avoid stimulating cardiac contraction. In some embodiments, the test pulse does not affect cardiac function. In some embodiments, test pulse parameters are selected so as not to interfere with therapeutic signals applied by an implanted cardiac device, such as pacing or cardiac contractile modulation signals. In some embodiments, the test pulse is applied only for the purpose of assessing lead condition (e.g., lead integrity).

One aspect of some embodiments relates to a device circuit in which impedance is measured by measuring the current across a grounding resistor. Typically, non-defibrillation leads are grounded through the same resistor. Therefore, no additional circuitry is required for impedance measurement. A potential advantage of using existing device circuitry to measure impedance can include keeping the device size minimal, as no additional components are needed for the measurement. Another potential advantage of measuring impedance by measuring the current across a resistor, rather than, for example, measuring the discharge of a defibrillation capacitor (see Figure 3), can include the ability to detect impedance even when a relatively low voltage test pulse is applied. When measuring impedance through a capacitor, the applied test pulse voltage must be high enough to detect minute changes in capacitor discharge. Therefore, according to some embodiments, measuring the current across a resistor can provide higher measurement sensitivity.

One aspect of some embodiments involves estimating the coil-to-can impedance (between the coil of the defibrillator electrode and the housing of the cardiac device) without directly performing measurements between the two components. In some embodiments, a method for estimating the coil-to-can impedance includes applying a test pulse to measure a reference coil-to-can impedance (optionally once or a limited number of times); then measuring a reference loop electrode-to-coil impedance; and then (optionally) repeating the loop electrode-to-coil measurement. In some embodiments, the current coil-to-can impedance is estimated or calculated based on the difference between the currently measured loop electrode-to-coil impedance and the reference loop electrode-to-coil impedance, taking into account the reference coil-to-can impedance. A potential advantage of this approach may include avoiding multiple periodic measurements of the coil-to-can impedance, thereby reducing the number of times current is conducted along the sensory nerve pathway, potentially alleviating patient discomfort.

As indicated in this article, the assessment or estimation of lead integrity may refer to the assessment of the following: defibrillation leads or portions thereof, such as defibrillation coils; non-defibrillation leads (e.g., pacing leads, cardiac systolic modulation leads) or portions thereof; and/or other circuitry or electrical connections of cardiac devices.

As referred to herein, a non-defibrillation lead can mean: a lead that is not suitable for applying current exceeding a certain threshold, such as the current required for defibrillation; a lead that does not contain a defibrillation coil or other defibrillation element; a lead suitable for applying pacing signals and/or applying cardiac contractile modulation signals; or a lead that includes one or more electrodes for applying and/or sensing electrical signals (in one example, an electrocardiogram).

To better understand some embodiments of the present invention, first refer to FIG3, which illustrates a circuit for impedance measurement that can be used in an implantable pulse generator device (IPG).

This figure illustrates an example of an ICD (Implantable Cardiac Defibrillator) device including a defibrillation coil 301. To assess the integrity of the wire 303 on which the coil is configured, the impedance (“can”) of the coil 301 can be measured by transmitting a pulse from the defibrillation capacitor 305 between the coil 301 and the device housing 307. For a measurable capacitance change to occur, the transmitted pulse must have a sufficiently high amplitude and sufficient width, for example, delivering at least 12V over a time period between 5 and 10 milliseconds. These requirements are determined by the capacitance of the capacitor 305 (150 μF in some examples) and the characteristics and configuration of the switching circuitry (indicated by switches S1-S4).

In some cases, applying a pulse with the aforementioned characteristics may cause pain and/or be strongly felt by the patient. Therefore, impedance measurements are sometimes performed in a clinical setting and require monitoring by a clinician. This may prevent routine and periodic measurements from being performed at short intervals (e.g., daily or even hourly), which could help identify defects in a timely manner, reduce risks, and mitigate potential harm to the equipment and/or the patient.

In some cases, additional dedicated circuitry is added to the device for impedance measurements. This may take up space in the existing equipment or enlarge it. The added circuitry typically requires extra isolation, which can increase the weight and/or size of the device.

In some pacemaker devices, impedance is measured by the discharge of a capacitor throughout the entire duration of the pacing pulse.

Before explaining at least one embodiment of the present invention in detail, it should be understood that the application of the present invention is not necessarily limited to the details of the construction and arrangement of the components and/or methods set forth in the following description and/or illustrated in the drawings and/or embodiments. The present invention can have other embodiments, or can be practiced or performed in various ways.

Before explaining at least one embodiment of the present invention in detail, it should be understood that the application of the present invention is not necessarily limited to the details set forth in the following description or illustrated by examples. The present invention can have other embodiments, or can be practiced or implemented in various ways.

Referring now to the accompanying drawings, FIG1A is a schematic diagram of an implantable device including a defibrillation lead and at least one cardiac contractile modulation lead according to some embodiments.

In some embodiments, the implantable device 101 includes a pulse generator 103. In some embodiments, the pulse generator 103 includes a housing 109, which includes, for example: a power supply (e.g., a battery); control circuitry configured for timing and generating electrical pulses; sensing circuitry; communication circuitry; storage device and/or others.

In some embodiments, one or more stimulation leads, such as leads 105, 107, are connected to and extend outward from the housing. In some embodiments, the leads comprise one or more wires surrounded by an external insulation layer. In some embodiments, the leads comprise two wires with different polarities. In some embodiments, the wires of the leads are coiled.

In some embodiments, the pulse generator 103 is implanted outside the heart, such as in the subclavian region. Optionally, implantation is performed via minimally invasive surgery.

In some embodiments, the housing (also referred to as the “canister”) of the pulse generator 103 is subcutaneously implanted near the left chest.

In some embodiments, leads 105 and 107 extend from the pulse generator 103, and at least the distal segment of the lead is implanted within the heart 111. In some embodiments, as shown, both leads pass through the right atrium 113 and contact the ventricular septum 115 at their distal ends. In some embodiments, each lead contacts the septum at a different location.

It should be mentioned that, alternatively, a single lead comprising two spaced-apart stimulating electrodes is used. It should also be noted that, in Figure 1A, two leads are also shown in the right ventricle 131 against the interventricular septum 115; however, one or more stimulating leads may be located in other positions, thus having different loops of action and/or targeting different tissues. In some embodiments, the lead is located inside the heart, on its right side, to take advantage of two potential benefits: (a) less extracardiac tissue is stimulated; and (b) less invasive access and/or presence compared to the left heart.

In some embodiments, one lead is implanted outside the heart, while the other lead is implanted inside the heart.

In some embodiments, each wire terminates at a terminal electrode (see terminal electrode 117 of wire 107, terminal electrode 119 of wire 105). The terminal electrodes may be configured as contact electrodes, screw-in electrodes, sutured electrodes, free-floating electrodes, and/or other types.

In some embodiments, one or both of the wires include a ring electrode (see ring electrode 121 of wire 107, ring electrode 123 of wire 105), which is located near the end electrode along the wire.

In some embodiments, loop and/or terminal electrodes of a non-defibrillation lead (e.g., a pacing lead, a cardiac contractile modulation lead) are implanted in the right ventricle or right atrium of the heart.

In some embodiments, the end electrode is threaded to be threaded into tissue. Alternatively, the end electrode may simply be positioned to contact the tissue.

In some embodiments, one or both of the leads include a defibrillation coil (see coil 125 of lead 105). Optionally, coil 125 is located along the lead near the proximal end of the end electrode and/or the proximal end of the loop electrode.

In some embodiments, the coil is implanted in the right ventricle, right atrium, or vena cava.

In some embodiments, lead 105 transmits a defibrillation signal. In some embodiments, lead 107 transmits a non-defibrillation signal, such as a pacing signal, and/or a non-excitatory signal, such as a cardiac contractile modulation signal.

In some embodiments, a cardiac contractile modulation signal is applied to contact or within the ventricular tissue.

In some embodiments, a cardiac contractility modulation signal is applied to the heart during the relative and/or absolute refractory period of the heart. In some embodiments, the signal is selected to increase ventricular contractility when the electric field of the signal stimulates such ventricular tissues (e.g., the left ventricle, right ventricle, and/or ventricular septum). In some embodiments of the invention, contractility modulation is provided by phosphorylation of a phospholamban induced by the signal. In some embodiments of the invention, contractility modulation is caused by changes in protein transcription and/or mRNA production induced by the signal, optionally in the form of a reversal of a fetal gene program. Unless otherwise stated, the term “cardiac contractility modulation” is used herein as a general placeholder for all such signals. It should be noted that in some embodiments, the cardiac contractility modulation signal may be excitatory to tissues other than the tissue to which it is applied.

While not limited to a single pulse sequence, the term "cardiac contractile modulation" is used to describe any family of signals that: include significant components applied during the absolute refractory period; have clinically significant effects on acute and/or chronic cardiac contractility; and/or cause reversal of fetal genetic programs and/or increase phosphorylation of phospholamban. In some embodiments, the signal may be excitatory to one part of the heart and non-excitatory to others. For example, the signal may be excitatory in the atria but applied in the ventricles at a non-excitatory time (relative to ventricular activation).

In some embodiments of the invention, the signal that is potentially stimulated during the receptive period of the cardiac cycle is non-stimulatory due to its timing. In particular, the signal is applied during the refractory period of the affected tissue and optionally during the absolute refractory period.

Figure 1B schematically illustrates a cross-measurement of impedance between components of two leads in an implantable device according to some embodiments.

In some embodiments, as mentioned herein, impedance measurement (in ohms) may include the resistance of a component or circuit to the current of a test pulse. In some embodiments, the test pulse is generated by a pulse generator.

In some embodiments, impedance is measured between a component (or portion) of two different conductors (e.g., conductor 105 and conductor 107). Examples of these cross-impedance measurements (also referred to as inter-conductor measurements) may include:

Coil 125 and end electrode 117; coil 125 and ring electrode 121; ring electrode 123 and end electrode 117; ring electrode 123 and ring electrode 121; end electrode 119 and end electrode 117; end electrode 119 and ring electrode 121.

Additionally or alternatively, impedance is measured between components of a single conductor. For example, in conductor 105: coil 125 and loop electrode 123; coil 125 and end electrode 119; loop electrode 123 and end electrode 119. For example, in conductor 105: end electrode 117 and loop electrode 121.

In some embodiments, the condition of a conductor assembly (e.g., electrodes, coils, and/or other electrical contacts) is estimated using a two-step method, wherein impedance is measured between the component under test and a first other component, and then impedance is measured between the component under test and a second other component. This method can be advantageous in determining which component is causing a deviation from the normal and/or expected impedance range.

Figure 1C is a schematic diagram of impedance measurement in a cardiac device comprising two leads according to some embodiments.

In some embodiments, the device includes two stimulation leads 151, 153 implanted in the heart 155. In some embodiments, stimulation lead 151 is configured to apply a defibrillation signal and is connected to an ICD module 157. In some embodiments, stimulation lead 153 is configured to apply a non-defibrillation signal, such as cardiac contractile modulation and/or pacing signal, and is connected to a pacing/cardiac contractile modulation module 159.

In some embodiments, impedance is measured for a single lead (e.g., a single conductor), such as between components of a single lead (coil, end electrode, loop electrode). Additionally or alternatively, cross impedance is measured between two leads. In some embodiments, impedance is estimated by calculating the resistance of the associated circuitry. For example, to estimate the impedance of only the ICD lead, the impedance of the pacing/cardiac contractile modulation lead can be measured; then the cross impedance between the two leads can be measured; and then the associated resistance of the circuitry, such as that measured only for the pacing/cardiac contractile modulation lead, can be subtracted to estimate the ICD lead impedance.

In some embodiments, impedance is measured between the coil and the first electrode, then between the coil and the second electrode, and/or between the first and second electrodes. In some embodiments, the impedance between the two electrodes is subtracted from the sum of the impedances between the coil and the two electrodes. The coil impedance can be evaluated by dividing the result by two.

Figures 2A-2D are flowcharts of a general method for assessing lead condition by measuring impedance in a cardiac device, according to some embodiments. In some embodiments, the cardiac device includes at least one defibrillation lead and at least one non-defibrillation lead, such as a pacing lead, a cardiac contractility modulation lead, and/or others.

The flowchart in Figure 2A illustrates a method for evaluating wire integrity using existing device circuitry according to some embodiments.

In certain situations, such as when the device is not in contact with other components, the leads in an active implantable cardiac device are most prone to failure. Lead failures or defects, such as cuts in the lead or holes in the lead insulation, can occur due to tension on the lead, body movement, blood flow in contact with the lead, and/or other factors. In some cases, when two or more leads are placed in a blood vessel or body cavity, contact between the two leads can increase the likelihood of lead failure. Therefore, in certain situations, to maintain a safe and properly functioning system, it is desirable to provide rapid and effective detection of lead conditions (e.g., breakage, displacement, connectivity problems, insulation problems, deformation, etc.).

In some embodiments, impedance measurement can allow the detection of conductor condition because the measured impedance value is affected by defects (such as those described above) and deviates from the expected or normal value or range. The presence of a defect can be identified based on such changes in impedance value and/or based on the absolute impedance value. In one example, insulation failure may expose a conductor wire to fluids and/or blood, resulting in a decrease in the measured value compared to, for example, the expected (and/or previously measured) value. In another example, a cut and/or narrowing of the conductor can result in a higher impedance value. In yet another example, fluctuations in the measured impedance value can indicate a dynamic and ongoing situation where the conductor sometimes functions normally and at other times does not. In some cases, impedance fluctuations are caused by changes in body posture, movement, breathing, and/or heartbeat, which may cause movement of the conductor and/or associated circuitry.

In an exemplary configuration, the device includes defibrillation leads and non-defibrillation leads.

In step 201, in some embodiments, the impedance between the two conductors is measured by applying a test pulse. In some embodiments, the impedance is measured using existing equipment circuitry without the use of additional circuitry or components. In one example, as further detailed below, the current across the grounding resistance connecting the non-defibrillator conductor is measured to determine the impedance between the two conductors.

In step 203, the measured impedance value is compared with one or more of the following: a lookup table, one or more previously measured values, one or more predefined values (e.g., values set by the manufacturer, values set by the operator (e.g., physician, technician), known values from literature, baseline values, and/or others).

In some embodiments, a baseline measurement of the impedance between one or more sets of components of the device leads is performed immediately after implantation. Alternatively or additionally, baseline measurements are performed during follow-up to optionally update previously measured baseline values. In some embodiments, baseline measurements are performed at any time when the condition of the device and its components is known to be normal and operational.

In some embodiments, a defect is indicated if the measured impedance change is greater than or equal to 20%, 30%, 40%, 50%, or a smaller percentage (i.e., lower or higher) of a reference value. In some embodiments, a measured impedance change that differs from a reference value by less than (i.e., less than or greater than) 20% indicates a normal condition. In some embodiments, a decrease in impedance indicates a short circuit. In some embodiments, an increase in impedance indicates an open circuit.

In one example, the impedance from the reference loop electrode to the coil is 250 ohms. If the impedance from the loop electrode to the coil is later measured to increase to, for example, 500 ohms, it may indicate a short circuit in the coil leads (defibrillation leads) or the electrode leads (non-defibrillation leads).

In some embodiments, the device's controller is programmed to perform a comparison between a measured impedance value and a desired impedance value. Additionally or alternatively, a remote server, computer program, and/or cellular phone application communicating with the device is configured to perform the comparison.

In step 204, according to some embodiments, the condition of the lead is determined based on the results of a comparison. In some embodiments, the measured impedance value indicates a defect if it is above a set threshold, below a set threshold, or outside the expected or predetermined range. Optionally, an alarm is issued if a defect is detected. In some embodiments, an alarm is issued from the device controller to a physician and/or other supervisory authority (e.g., via wireless communication). In some embodiments, if an impedance test is performed during routine device inspection (e.g., in a technical laboratory and/or physician's office), the defective lead may be replaced. In some embodiments, if a defect is detected in the defibrillator coil and/or its connection, the defibrillator coil (and/or the defective connection) is replaced immediately.

In step 205, optionally, the impedance measurement is repeated. In some embodiments, assuming no defect is detected, the measurement is performed periodically, such as every 30 seconds, 1 minute, 5 minutes, 15 minutes, 1 hour, 2 hours, 4 hours, 12 hours, 24 hours, 2 days, 5 days, 1 week, or at intervals longer or shorter.

In some embodiments, if the impedance of a continuously measured impedance differs from that of a previous measurement by, for example, greater than 5%, greater than 10%, greater than 20%, or a middle, larger, or smaller percentage, this may indicate a problem, possibly a wire insulation issue. In some embodiments, an alarm is provided when a change above a threshold is detected.

In some embodiments, assessing which wire (or wire assembly, such as an electrode) is defective may involve performing one or more additional measurements, optionally using an additional (e.g., a second) wire as a reference.

Additional or alternative, measurements may be taken during follow-up visits to the clinic, for example, monthly, every two months, every six months, annually, or at longer or shorter intervals.

Figure 2B is a flowchart of a method for measuring impedance during the application of cardiac contractile modulation stimulation according to some embodiments.

In an exemplary configuration, the device includes a defibrillation lead and a second lead for applying cardiac contractile modulation stimulation. In step 209, in some embodiments, such as as described herein, impedance is measured between the two leads. Optionally, impedance is measured between the coil of the defibrillation lead and one of the electrodes of the cardiac contractile modulation lead (e.g., a distal electrode, a loop electrode). A potential advantage of performing measurements between these components may include avoiding current conduction through different paths, such as between the coil of the defibrillation lead and the pulse generator itself (from the coil to the canister), thereby avoiding current conduction at the location of sensory nerves.

In some embodiments, impedance measurements are performed during the application of a cardiac contractile modulation signal. Optionally, the measurement is performed during the initial phase of the cardiac contractile modulation signal. For example, if the duration of the cardiac contractile modulation signal is 20 ms to 30 ms, the measurement is performed, for example, at 10 μsec, 30 μsec, 120 μsec, 2 msec, 5 msec, 7 msec, or in the middle of the cardiac contractile modulation signal, either later or earlier. Additionally or alternatively, impedance measurements are performed at a later phase of the cardiac contractile modulation signal, for example, at 10 ms, 15 ms, 20 ms, or in the middle of the cardiac contractile modulation signal, either later or earlier.

In some embodiments, the duration of the test pulse used to measure impedance is as short as possible, but still long enough to provide a reasonable estimate of the measured impedance. Optionally, the duration of the test pulse is set according to the specific circuit involved.

In some implementations, the cardiac contractile modulation lead is "split" into two spaced-apart stimulating electrodes, allowing measurements to be performed between the defibrillation coil and each electrode. Optionally, a second path (e.g., between the coil and the first electrode) can be selected if a measurement path (e.g., between the coil and the second electrode) causes pain in the patient and/or is otherwise sensed.

In some embodiments where non-defibrillation leads are used as pacing leads, impedance measurements can be performed during the pacing signal. In some embodiments, the duration of the pacing signal is between 0.1 ms and 1.5 ms, 0.2 ms and 1 ms, 0.5 ms and 1.2 ms, or an intermediate, longer, or shorter duration.

According to some embodiments, in step 211, the measured impedance value is compared with one or more of the following: a lookup table, one or more previously measured values, one or more predefined values (e.g., values set by the manufacturer, values set by the operator (e.g., physician, technician), values obtained from literature, benchmark values, and/or others), such as as described above. In step 213, according to some embodiments, such as as described above, the condition of the conductor is evaluated. In step 215, optionally, the measurement is repeated.

Figure 2C is a flowchart of a method for performing a measurement during the ventricular refractory period according to some embodiments. In some embodiments, in step 231, a test pulse for measuring impedance is applied during the ventricular refractory period. Optionally, the test pulse is applied during the absolute ventricular refractory period. Potential advantages of measuring impedance during the ventricular refractory period may include that, during this period, cardiomyocytes are unable to initiate another action potential, thus reducing or preventing the risk of unwanted cardiac contractions caused by the test pulse.

According to some embodiments, in step 233, for example as described above, conductor integrity is determined based on the measured impedance value. According to some embodiments, at step 235, the impedance measurement is repeated. Optionally, the measurement is repeated during one or more consecutive ventricular refractory periods of the cardiac cycle.

Figure 2D is a flowchart of a method for assessing wire integrity by indirect impedance measurement according to some embodiments. In some embodiments, the method is performed to estimate ICD wire integrity by calculating or estimating the coil-to-can impedance. In some embodiments, the method is applied to attempt to reduce the number of impedance measurements taken along pathways that may cross nerve-innervated tissues (e.g., coil-to-can pathways).

At step 239, according to some embodiments, the impedance from the reference coil to the tank (such as between the coil and the pulse generator housing) is measured.

At step 241, according to some embodiments, the impedance from the reference loop electrode to the coil is measured (e.g., between the loop electrode (of the non-defibrillator lead) and the coil of the defibrillator lead).

In some embodiments, the baseline measurements of steps 239 and/or 241 are performed only once, or several times at relatively long intervals. For example, once every 2-6 months, once every 6-24 weeks, once every 6-12 months, or at longer or shorter intervals. Optionally, these measurements are performed during a clinic visit.

According to some embodiments, at step 243, the impedance from the toroidal electrode to the coil is measured again. Optionally, this measurement is performed periodically. In some embodiments, this measurement is repeated at shorter time intervals, such as every 30 minutes, every hour, every 4 hours, every day, every week, or in the middle, at longer or shorter time intervals.

At step 245, according to some embodiments, a reference coil-to-coil measurement is used, and the current coil-to-impedance can be estimated using the difference between the currently measured impedance of the toroidal electrode to the coil and the reference measured impedance of the toroidal electrode to the coil.

In some embodiments, the following function is used to calculate or estimate the current coil-can impedance:

The impedance (t) of the coil to the tank = impedance (reference) of the coil to the tank * impedance (t) of the electrode to the coil / impedance (reference) of the electrode to the coil. It should be noted that other functions, formulas, factors (e.g., linearization factor), and/or others can be applied. Optionally, specific parameters (e.g., coil-to-tank impedance) used to calculate or estimate the current impedance may be selected based on the specific device circuitry.

In some embodiments, the condition of the wires is assessed based on the estimated impedance. Optionally, the integrity of the defibrillation wires and/or their components (e.g., coils) is assessed.

A potential advantage of the method in Figure 2D is that, during normal operation, the defibrillation lead is stimulated less frequently than a non-defibrillation lead, making it potentially difficult to detect any defects that may develop in the defibrillation lead over time. Using the method described above, the condition of the defibrillation lead can be assessed more frequently. Another potential advantage may include: essentially avoiding the need to apply test pulses directly to the coil-to-canister path, thus avoiding a path that could be painful for the patient due to the nerve-innervated tissue along the way.

In some embodiments, the test pulse for measuring the impedance from the coil to the can is shorter in duration and applied at a higher voltage compared to the test pulse for measuring the electrode-to-coil impedance (which may have a lower voltage and optionally a longer duration).

Figure 4 is a schematic diagram of a circuit suitable for performing impedance measurement in a device including a defibrillation lead and at least one cardiac contractile modulation lead, according to some embodiments.

In some embodiments, impedance is assessed by measuring, for example, the current (“Iccm”) flowing through the cardiac contractile modulation return path via a grounding resistor (“R_I_sense”) 401.

In some embodiments, a lower test pulse voltage (such as 0-8V, 0-5V, 0.1-3V, 0.1-8V, or intermediate, higher or lower voltages) can be applied by measuring current rather than, for example, measuring the change in capacitance of the capacitor, compared to higher voltage levels (such as 8-16V, 10-16V, 12-16V, 14-16V, or voltages between intermediate, higher or lower) required to produce a noticeable and measurable change in the capacitor.

In some embodiments, as illustrated in FIG4, the device includes two modules: a defibrillation module, including, for example, an H-bridge configuration of switches for controlling current conduction to the defibrillation leads, and a capacitor bank for setting voltage to the defibrillation coil; and a cardiac contractility modulation module, including, for example, an H-bridge configuration of switches for controlling current conduction to the cardiac contractility modulation leads, and a DC power supply.

The following describes an example of impedance estimation using the illustrated circuit: In some embodiments, the defibrillation capacitor bank 403 is charged to a voltage, for example, between 8 and 16 V, to apply a pulse. In some embodiments, the switch S3 (see 405) of the defibrillation H-bridge and the switch S4 (see 407) of the cardiac contractility modulation H-bridge close simultaneously for a short period of time to apply a pulse, for example, 5 μs, 10 μs, 15 μs, 20 μs, or an intermediate, shorter, or longer time period. Optionally, the closing operation of the switches is performed shortly after the R-wave of the cardiac cycle, optionally during the total ventricular refractory period, for example, less than 50 ms, less than 20 ms, less than 10 ms, less than 5 ms, 4 ms, less than 3 ms, less than 2 ms, or an intermediate, longer, or shorter time period after the R-wave.

In some embodiments, the duration of the pulse is selected to be long enough that the analog-to-digital converter (not shown) of the device can correctly sample the current flowing through the cardiac contractility modulation return path “Iccm”. Optionally, the Iccm current is measured as the current flowing through the grounding resistor 401. Potential advantages of measuring impedance by measuring Iccm on the grounding resistor may include the fact that, due to the relatively high sensitivity of the measurement, such as compared to measuring capacitance changes, the pulse can be applied at a relatively low voltage (e.g., 0-8V, 0.1-7V, 0.5-8.5V, or between medium, higher, or lower voltages). Using a relatively low voltage pulse may reduce patient pain and/or sensation.

Additionally or alternatively, in some embodiments, the voltage (“Vdefib”) on the defibrillator capacitor bank 403 is sampled.

In some examples, an estimate of the impedance between the defibrillator coil 409 and the device housing 411 (coil to canister CAN) cannot be directly derived from the above measurements (i.e., Iccm). This may be due to the fact that in many cases, the connection 414 (e.g., wire) extending between the coil 409 and the ring electrode 413 is coiled and imposes its own impedance (typically in the range of tens of ohms). In some cases, the impedance of the coil itself varies with the current (optionally in a non-linear manner), resulting in different impedance measurements for different voltage values.

Another factor that could directly affect the coil-to-can impedance estimation from the Iccm measurement results might include: the S3 of the defibrillator bridge can exhibit an impedance that varies non-linearly with current. This could interfere with the assessment of direct current.

In view of the above, in some embodiments, the coil-to-can impedance is estimated, for example, as described in Figure 2D. Optionally, a reference measurement of the coil-to-can impedance is performed (e.g., using a method described, for example, for the circuit of Figure 3). A linearization factor is then calculated using equations or functions, lookup tables, device specifications, and/or other references. In some embodiments, the linearization factor is associated with a one-time measurement of the coil-to-can impedance. In some embodiments, the linearization factor can be applied to achieve the estimated coil-to-can impedance, for example, in a future measurement where the coil-to-can measurement itself is not performed, but rather measured to Iccm. In one example, the estimated coil-to-can impedance is calculated as follows:

Estimated coil-to-can impedance = f(Iccm, reference coil-to-can Ω)

In some embodiments, one or more thresholds are set to determine when the resulting estimated coil-to-can impedance indicates that the defibrillator lead is in a normal and undamaged condition; and when the estimated coil-to-can impedance may indicate a defect in the integrity of the defibrillator lead.

In one example, the threshold is set as follows:

If the estimated impedance is less than 25Ω, then the impedance is too low.

If 25Ω ≤ estimated impedance ≤ 100Ω, then the impedance is normal.

If the estimated impedance is >100Ω, then the impedance is inappropriately high.

In some embodiments, an alarm and/or other notification is generated when the impedance is found to be outside the expected range.

Figure 5 is a schematic diagram of a circuit suitable for performing impedance measurement in a device including a defibrillation lead and at least one pacing lead, according to some embodiments.

In this figure, the device includes: a defibrillation module, such as the defibrillation module shown in Figure 4; and a pacing module for controlling the activation of the pacing lead.

Impedance can be assessed by measuring “Ipace”, the current across grounding resistor 501, and/or by measuring Vdefib, for example, as shown in Figure 4.

In some embodiments, one of the differences between the circuits described in FIG4 and FIG5 is that the pulses applied by the non-defibrillation leads (e.g., the cardiac contractile modulation lead in FIG4; the pacing lead in FIG5) have different characteristics, such as the amplitude, duration, and timing of the pulses.

Figure 6 is a schematic diagram illustrating the components of an implantable ICD/cardiac contractility modulation device 600 according to some embodiments.

In some embodiments, the device includes an ICD lead 601 and a cardiac contractility modulation lead 603.

In some embodiments, activation of the ICD leads is performed via an ICD module including or connected to: an ICD controller 605; a defibrillation pulse generator 607 (via one or more capacitors 609); a power supply (e.g., a battery 613) and power management circuitry 615; and an ICD sense 611 that senses the applied pulse to verify whether the pulse is within a selected (e.g., programmed) amplitude and/or duration. In some embodiments, activation of one or more cardiac contractile modulation leads 621, 623 optionally located in the right ventricle is performed via a cardiac contractile modulation module including or connected to: a cardiac contractile modulation control 617 and a cardiac contractile modulation generator 619.

Note that in some embodiments, the ICD coil and one or more electrodes for pacing and/or cardiac contractility modulation are configured on the same lead. In some embodiments, the lead is connected to isolation 625. In some embodiments, the device includes a housekeeping module 627, which includes or is connected to one or more sensors, such as a temperature sensor 629, a magnetic sensor 631, and a communication device 633, such as an antenna, a receiver, etc. Other sensors may include flow sensors, pressure sensors, acceleration sensors, and/or other sensors.

In some embodiments, data received from one or more sensors is received as input. Optionally, the input is processed by device control (e.g., by ICD control, cardiac contractility modulation control, and/or a general controller, not shown) and may optionally be used as input to a decision-making process in device 600.

In some embodiments, device control (e.g., ICD control, cardiac contractility modulation control, and/or a general controller, not shown) performs one or more pieces of logic to, for example, determine: the timing of a signal and/or other parameters and/or whether a signal should be applied.

Optionally, a memory (not shown) may be provided, for example, to store logic, past actions, treatment plans, adverse events, and/or pulse parameters.

Optionally, a recorder (not shown) may be provided to store the activities of device 600 and/or the patient. Such logging and/or programming may be performed using communication module 633 to send and/or receive data from device 600 to, for example, a programmer (not shown), such as programming pulse parameters.

Figure 7 is an example of an impedance lookup table for evaluating conductor conditions according to some embodiments.

In some embodiments, the presence and, optionally, type of conductor condition are determined based on the measured impedance value. Optionally, a device (e.g., a device controller) is programmed with ranges and/or thresholds to generate an alarm based on said ranges and/or thresholds if a conductor condition is detected. Figure 7 illustrates several examples of thresholds and ranges, each associated with a different type of conductor condition. Note that this table is merely an example and different values, thresholds, ranges, and/or conductor conditions may be used.

Impedance range state <50 ohms Short circuit 50-150 ohms Wire isolation problem 150-1000 ohms Normal range >1000 ohms Conductor fault

Figure 8 is a flowchart of a method for estimating the connection status in a device including a defibrillation lead and two pacing leads, according to some embodiments.

In some embodiments, in a device configuration that includes three leads or three different components (e.g., an ICD lead and two electrodes, such as two pacing electrodes; an ICD lead and two cardiac contractile modulation electrodes; and an ICD lead and a cardiac contractile modulation or pacing lead with “split” ends of separate electrodes), cross-impedance measurement can provide information for identifying lead conditions and/or connectivity problems.

The example in Figure 8 illustrates cross-impedance measurement in an ICD/pacing device. It should be noted that a similar method can be applied to ICD/cardiac contractility modulation devices.

At step 801, in some embodiments, an ICD coil and two electrodes, such as two pacing electrodes, are implanted.

In step 803, according to some embodiments, an impedance measurement is performed between the ICD coil and the first electrode. At step 805, according to some embodiments, the measurement result is evaluated to determine whether the received impedance value indicates a normal condition of the conductor or whether the received impedance value indicates a continuity/integrity problem. According to some embodiments, if the impedance value is within the expected (normal) range, then in step 807, after waiting for a set time (e.g., 3 seconds, 5 seconds, 10 seconds, 30 seconds, 60 seconds, 120 seconds, 360 seconds, or an intermediate, longer, or shorter time period), a repeat measurement can be performed.

Alternatively, according to some embodiments, if the received impedance value indicates a problem, an impedance measurement is performed between the first and second electrodes at step 809. Additionally or alternatively, an impedance measurement is performed between the ICD coil and the second electrode at step 811.

At steps 813 and 815, check whether the measured values fall within the expected range.

If the impedance value measured between the first and second electrodes is within the expected range, this indicates a defect in the ICD coil, and therefore an alarm regarding the ICD coil status is issued at step 817. If the impedance value measured between the first and second electrodes is not within the expected range, this indicates a defect in the first electrode, and therefore an alarm regarding the first electrode status is issued at step 819.

If the impedance measured between the ICD coil and the second electrode is within the expected range, it indicates a defect in the first electrode, and therefore an alarm regarding the status of the first electrode is issued at step 819. If the impedance measured between the ICD coil and the second electrode is not within the expected range, it indicates a defect in the ICD coil, and therefore an alarm regarding the status of the ICD coil is issued at step 817.

Figure 9 is a graphical representation of the cardiac cycle relative to the timing of the application of cardiac contractile modulation stimulation and the test pulse used for impedance measurement, according to some embodiments.

In some embodiments, a test pulse for measuring impedance is applied during the total ventricular refractory period, which typically occurs between the timing of the R wave and T wave in the cardiac cycle. Typically, the total refractory period is between 200 and 400 milliseconds.

In some embodiments, the duration of the applied test pulse (indicated as “I” in the figure) is between 1 and 100 microseconds, for example, 10 microseconds, 15 microseconds, 30 microseconds, 50 microseconds, 70 microseconds, or intermediate, longer or shorter durations.

Optionally, in some embodiments, the cardiac contractile modulation signal itself is used as the test pulse, and impedance measurement is performed during the application of the cardiac contractile modulation signal. In this case, the applied pulse can have a duration between 1 millisecond and 50 milliseconds, such as 5 milliseconds, 10 milliseconds, 30 milliseconds, 40 milliseconds, or intermediate, longer or shorter. Alternatively, the impedance measurement is performed during the ventricular refractory period, rather than during the application of the cardiac contractile modulation signal, such as before or after the application of the cardiac contractile modulation signal. When the cardiac contractile modulation signal is not used as the test pulse, a lower voltage (i.e., relative to the voltage applied to the cardiac contractile modulation) can be used. Optionally, a sufficiently high threshold is selected for the test pulse voltage, which is sufficient to be generated by the device and result in a measurable (detectable) current. In the example, the test pulse voltage is higher than 0.01V, higher than 0.05V, higher than 0.1V, or intermediate, higher or lower voltages. In some embodiments, alternatively, in addition to a lower threshold, a higher voltage threshold, such as 0.1V, 0.5V, 1V, or intermediate, higher or lower voltages, is also selected.

It should be noted that these times can vary between heart rates and under different conditions, such as during pharmacological intake, anatomical excitation levels, heart rate, recent arrhythmia, and/or exercise. In some embodiments, the pulse generator is pre-programmed with parameters that take into account such refractory periods. Optionally, different numbers (e.g., stored in device memory) are used for different conditions (e.g., different heart rates).

The terms “comprises,” “comprising,” “includes,” “including,” “having,” and their conjugates mean “including but not limited to.”

The term "consisting of" means "including and limited to".

The term "consisting essentially of" means that the composition, method, or structure may include additional components, steps, and/or portions, provided that such additional components, steps, and/or portions do not substantially alter the fundamental and novel characteristics of the claimed composition, method, or structure.

As used herein, the singular forms “a,” “an,” and “the” include plural references unless the context clearly indicates otherwise. For example, the terms “a compound” or “at least one compound” can include a variety of compounds, including mixtures thereof.

Throughout this application, various embodiments of the invention may be presented in a range format. It should be understood that the range format is for convenience and brevity only and should not be construed as an inflexible limitation on the scope of the invention. Therefore, the description of the range should be considered as specifically disclosing all possible subranges and individual numerical values within said ranges. For example, a description of the range from 1 to 6 should be considered as explicitly disclosing subranges from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, and individual numbers within said ranges, such as 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

Whenever a range of numbers is indicated herein, it is intended to include any referenced numbers (fractions or integers) within the indicated range. The phrases “range/scope between the first indicated number and the second indicated number” and “range/scope from the first indicated number to the second indicated number” are used interchangeably herein and are intended to include the first and second indicated numbers as well as all decimals and integers between them.

Whenever a range of numbers is indicated herein, it is intended to include any referenced numbers (fractions or integers) within the indicated range. The phrases “range/scope between the first indicated number and the second indicated number” and “range/scope from the first indicated number to the second indicated number” are used interchangeably herein and are intended to include the first and second indicated numbers as well as all decimals and integers between them.

As used herein, the term "method" refers to the manner, means, technique, and process used to accomplish a given task, including, but not limited to, those manner, means, techniques, and processes known to or readily developed from known manner, means, techniques, and procedures by practitioners in the fields of chemistry, pharmacology, biology, biochemistry, and medicine.

As used herein, the term “treating” includes eliminating, substantially inhibiting, slowing or reversing the progression of a condition, substantially improving the clinical or aesthetic symptoms of the condition, or substantially preventing the occurrence of the clinical or aesthetic symptoms of the condition.

It should be understood that certain features of the invention described in the context of a single embodiment for clarity may also be provided in combination in a single embodiment. Conversely, for brevity, various features of the invention described in the context of a single embodiment may also be provided individually or in any suitable sub-combination or suitably in any other described embodiment of the invention. Certain features described in the context of various embodiments should not be considered essential features of those embodiments unless the embodiments would not function without those elements.

Although the invention has been described in conjunction with specific embodiments thereof, it will be apparent to those skilled in the art that many alternatives, modifications, and variations will be readily apparent. Therefore, it is intended to cover all such alternatives, modifications, and variations that fall within the spirit and broad scope of the appended claims.

All publications, patents, and patent applications mentioned in this specification are incorporated herein by reference in their entirety to the same extent as if each individual publication, patent, or patent application were specifically and individually indicated to be incorporated herein by reference. Furthermore, any reference or designation of any reference in this application should not be construed as an admission that such reference is available as prior art to this invention. The use of section headings should not be construed as an inherent limitation. Additionally, any priority documents of this application are incorporated herein by reference in their entirety.

Claims (36)

1. A method for testing lead status in an implantable cardiac device including a first defibrillation lead and a second non-defibrillation lead, characterized in that: the method comprises: The impedance between the first defibrillation lead and the second non-defibrillation lead is measured by applying a test pulse from the defibrillation capacitor bank through the first defibrillation lead and using the second non-defibrillation lead for current return to ground, wherein the test pulse is applied during a ventricular refractory period and has a sufficiently low voltage to avoid or reduce sensation to the patient with the implanted cardiac device when applied during the ventricular refractory period; and The condition of at least one of the defibrillation leads and non-defibrillation leads is determined based on the measured impedance value. The parameters of the test pulse are selected such that the duration of application of the test pulse does not affect cardiac function. Measuring the impedance between the first defibrillation lead and the second non-defibrillation lead includes sampling the voltage across the defibrillation capacitor bank. 2. The method as claimed in claim 1, characterized in that: the time of applying the test pulse and the duration of the test pulse are selected so as not to stimulate contraction. 3. The method as described in any one of the preceding claims, characterized in that: the duration of the test pulse is less than 50 microseconds. 4. The method of claim 1, wherein the second non-defibrillation lead is configured to apply cardiac contractile modulation stimulation. 5. The method of claim 4, wherein the test pulse is applied during the application of the cardiac contractile modulation stimulation, during the ventricular refractory period. 6. The method as claimed in claim 5, wherein a signal applied as the cardiac contractile modulation stimulus is also the test pulse. 7. The method of claim 4, wherein the test pulse is applied before or after the cardiac contractile modulation stimulation is applied during the ventricular refractory period. 8. The method of claim 1, wherein the defibrillation lead comprises a coil, and the non-defibrillation lead comprises a loop electrode and a terminal electrode; and the step of measuring impedance comprises measuring at least one of the following: between the coil and the loop electrode; and between the coil and the terminal electrode. 9. The method of claim 1, wherein the condition of at least one of the defibrillation lead and the non-defibrillation lead is determined by one or more of the following methods: comparing the impedance value with one or more of the following: a lookup table; one or more previously measured values; one or more predefined values. 10. The method as claimed in claim 1, wherein the method comprises: repeating the measurement once a day. 11. The method of claim 1, wherein the method comprises: issuing an alarm regarding the condition of the conductor. 12. The method of claim 1, wherein determining the condition of the conductor comprises determining at least one of the following: conductor breakage, conductor displacement, conductor insulation, conductor connectivity, and conductor deformation. 13. The method as claimed in claim 1, characterized in that: at least a portion of the first lead and at least a portion of the second lead are implanted, so that they contact the wall of the right ventricle of the heart. 14. The method of claim 1, wherein: the defibrillation lead comprises a coil, a loop electrode, and a terminal electrode; the non-defibrillation lead comprises a loop electrode and a terminal electrode; and the impedance measurement comprises: measuring the inter-lead impedance between one of the coil, loop electrode, and terminal electrode of the defibrillation lead and one of the loop electrode and terminal electrode of the non-defibrillation lead. 15. The method as claimed in claim 1, wherein the non-defibrillation lead comprises a cardiac contractile modulation (CCM) lead or a pacing lead. 16. The method of claim 1, wherein the test pulse is applied at a voltage between 4 volts and 8 volts. 17. An implantable cardiac device, characterized in that: the device comprises: The first defibrillation lead includes a coil, a loop electrode, and a terminal electrode; A second non-defibrillation lead, comprising a loop electrode and a distal electrode, wherein multiple cardiac systolic modulation signals are transmitted through the second non-defibrillation lead; and A circuit for controlling and activating the coil and electrodes, the circuit including at least one grounding resistor electrically connected to the second non-defibrillation lead; wherein the circuit is configured to measure the current across the grounding resistor in response to an applied test pulse to obtain an indication of the condition of at least the first defibrillation lead or a portion thereof; wherein the circuit is configured to apply a plurality of cardiac contractile modulation signals, and the circuit is programmed to time the measurement of the current across the grounding resistor to be performed during the application of the cardiac contractile modulation signals. 18. The device of claim 17, wherein the circuitry is at least partially disposed within the housing of the cardiac device, and wires extend from the housing. 19. The device of claim 17, wherein the current measured across the grounding resistor in response to an applied test pulse is used to calculate the impedance between the coil and the housing of the device. 20. The device of claim 19, wherein the circuit is configured to use a predetermined linearizing factor to calculate the impedance between the coil and the housing of the device. 21. The device of claim 17, wherein the circuit is programmed to time the test pulse during the expected total non-responsive period of the cardiac cycle. 22. A method for evaluating the condition of leads in an implantable cardiac device, the implantable cardiac device comprising: a defibrillation lead having a coil; and at least one non-defibrillation lead having at least one electrode, the defibrillation lead and the non-defibrillation lead being positioned to contact two different tissue locations on the ventricular septum, characterized in that: the method comprises: (a) Apply a reference test pulse to measure the reference impedance between the defibrillation coil and the device housing; (b) Apply a reference test pulse to measure the reference impedance between the electrodes of the non-defibrillation lead and the defibrillation coil; (c) Periodically apply test pulses at shorter time intervals than in steps (a) and (b) to measure the impedance between the electrodes of the non-defibrillation lead and the defibrillation coil; and (d) Estimate the current impedance between the coil and the device housing based on the difference between the current measured impedance level measured at the third application and one or both of the reference measurements to assess the condition of the defibrillation lead. 23. The method of claim 22, wherein the third application is performed more frequently than the first and second applications. 24. The method according to any one of claims 22 to 23, wherein the periodic application comprises applying once every 24 hours. 25. The method of claim 22, wherein the third application is performed during the ventricular refractory period of the heart. 26. An implantable cardiac device, characterized in that: the device comprises: First defibrillation lead; Second non-defibrillation lead; and A circuit for controlling wires and for measuring impedance, said circuit being configured to: The cardiac contractile modulation signal is delivered through the second non-defibrillation lead; A test pulse is applied to measure the impedance between the first defibrillation lead and the second non-defibrillation lead to determine the condition of at least one of the defibrillation lead and the non-defibrillation lead based on the measured impedance value, wherein the circuit is configured to time the test pulse applied during the ventricular refractory period of the heart during the delivery of the cardiac contractile modulation signal. 27. The device of claim 26, wherein the defibrillation lead comprises a coil, and the non-defibrillation lead comprises a loop electrode and a terminal electrode, wherein the impedance is measured in at least one of the following: between the coil and the loop electrode; and between the coil and the terminal electrode. 28. The device of claim 26, wherein the circuit is configured to determine the condition of at least one of the defibrillation leads and the non-defibrillation leads by one or more of the following: comparing the measured impedance with one or more of the following: a lookup table; one or more previously measured impedance values; and one or more predefined impedance values. 29. The device of claim 26, wherein the circuit is configured to time the test pulse and perform a measurement every 24 hours. 30. The device of claim 26, wherein the circuit is configured to generate and issue an alarm regarding a determined wire condition. 31. The device as claimed in claim 26, wherein the determined conductor condition includes at least one of the following: conductor breakage, conductor detachment, conductor insulation failure, conductor connectivity failure, and conductor deformation. 32. The device of claim 26, wherein: the defibrillation lead comprises a coil, a loop electrode, and a terminal electrode, and the non-defibrillation lead comprises a loop electrode and a terminal electrode; and the impedance is measured between one of the coil, loop electrode, and terminal electrode of the defibrillation lead and one of the loop electrode and terminal electrode of the non-defibrillation lead. 33. The device of claim 26, wherein the non-defibrillation lead is configured to deliver pacing pulses to the heart. 34. An implantable cardiac device, characterized in that: the device comprises: case; A defibrillation lead having a coil, the defibrillation lead extending from the housing and configured to contact a first tissue location on the ventricular septum; A non-defibrillation lead having at least one electrode, the non-defibrillation lead extending from the housing and configured to contact a second tissue location on the interventricular septum; and Circuitry for controlling and activating the defibrillator leads and the non-defibrillator leads, and for measuring impedance. The circuit is configured as follows: (a) Apply a reference test pulse to measure the reference impedance between the coil of the defibrillation lead and the housing; (b) Apply a reference test pulse to measure the reference impedance between at least one electrode of the non-defibrillator lead and the coil of the defibrillator lead; (c) Apply test pulses periodically at shorter time intervals than in steps (a) and (b) to measure the impedance between at least one electrode of the non-defibrillator lead and the coil of the defibrillator lead; (d) Estimate the current impedance between the defibrillator coil and the housing based on the difference between one or both of the current measured impedance level measured between the at least one electrode of the non-defibrillator lead and the coil of the defibrillator lead, and a reference impedance measurement; and (e) Assess the condition of the defibrillation leads based on the estimated current impedance. 35. The device of claim 34, wherein the circuit is configured to apply the test pulse at least every 24 hours to measure the impedance between at least one electrode of the non-defibrillator lead and the coil of the defibrillator lead. 36. The device of claim 34, wherein the circuit is configured to apply the test pulse during the ventricular refractory period of the heart to measure the impedance between the at least one electrode of the non-defibrillation lead and the coil of the defibrillation lead.