WO2026009091A1 - Tachycardia remodeling therapy configuration based on an intrinsic timing interval - Google Patents

Abstract

An implantable medical device (IMD) includes a plurality of electrodes; sensing circuitry configured to sense a cardiac electrogram (EGM) of a patient via at least some of the electrodes; electrical stimulation circuitry configured to deliver pacing stimulation via at least some of the electrodes; an accelerometer; and processing circuitry configured to: determine an intrinsic timing interval based on the EGM and an accelerometer signal from the accelerometer, wherein the intrinsic timing interval is indicative of a passive ventricular filling interval of the patient during a first period of time; and control electrical stimulation circuitry configured to deliver pacing stimulation via at least some of the electrodes to deliver tachycardia remodeling therapy (TRT) for a second period of time by at least configuring an interval of the pacing stimulation based on the intrinsic timing interval.

Description

TACHYCARDIA REMODELING THERAPY CONFIGURATION BASED ON AN INTRINSIC TIMING INTERVAL

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63/666,469, filed July 1, 2024, the entire content of which is incorporated herein by reference.

FIELD

[0002] This disclosure generally relates to medical devices and, more particularly, to medical devices that deliver cardiac pacing.

BACKGROUND

[0003] Various types of implantable medical devices (IMDs) have been implanted for treating or monitoring one or more conditions of a patient. Such IMDs may be adapted to monitor or treat conditions relating to heart, muscle, nerve, brain, stomach, endocrine organs, or other organs and their related functions. Such IMDs may be associated with leads that position electrodes at a desired location or may be leadless with electrodes integrated with and/or attached to the device housing. These IMDs may have the ability to wirelessly transmit data either to another device implanted in the patient or to another instrument located externally of the patient, or both.

[0004] A cardiac pacemaker is a medical device, e.g., an HMD, configured to deliver cardiac pacing therapy to restore a more normal heart rhythm. Cardiac pacemakers sense the electrical activity of the heart, and deliver cardiac pacing based on the sensed electrical activity, via electrodes. Some cardiac pacemakers are implanted a distance from the heart, and couple to one or more leads that intravascularly extend into the heart to position electrodes with respect to cardiac tissue. Some cardiac pacemakers are sized to be completely implanted within one of the chambers of the heart and may include electrodes integrated with or attached to the device housing rather than leads. Some cardiac pacemakers provide dual chamber functionality, by sensing and/or stimulating the activity of both atria and ventricles, or other multi-chamber functionality. A cardiac pacemaker may provide multi-chamber functionality via leads that extend to respective heart chambers, multiple cardiac pacemakers may provide multi-chamber functionality by being implanted in respective chambers, or a cardiac pacemaker implanted in one chamber may sense and pace multiple chambers. SUMMARY

[0005] Heart failure with preserved ejection fraction (HFpEF) is a clinical syndrome in which patients exhibit signs and symptoms of heart failure (HF) as a result of relatively high left ventricular (LV) filling pressure, despite normal or near normal LV ejection fraction (LVEF). Over time, HFpEF can cause structural and functional changes to the heart. These structural and functional changes can cause further declines in patient health. Tachycardia remodeling therapy (TRT) aims to reverse the structural and functional changes in the heart caused by HFpEF. However, current methods of TRT may not be patient-specific, which can limit the effectiveness of the therapy and/or lead to patient discomfort during TRT administration.

[0006] In general, the techniques of this disclosure include facilitating patient-specific TRT administration. More specifically, this disclosure describes monitoring an intrinsic timing interval, e.g., a patient’s passive ventricular filling interval, over a first period of time and providing TRT by configuring an interval for pacing, e.g., atrial pacing or ventricular pacing, based on the patient’s passive ventricular filling interval. This disclosure describes techniques that may advantageously increase TRT efficacy and/or decrease patient symptoms and/or other complications associated with TRT. The techniques may be implemented in an implantable medical device (IMD), such as a pacemaker, e.g., a leadless pacemaker, and/or in a medical device system, e.g., a medical device system including a pacemaker.

[0007] As an example, an IMD may sense a cardiac electrogram (EGM) signal via at least some electrodes of a plurality of electrodes and, in some examples, an additional physiological signal, e.g., an accelerometer signal from an accelerometer. Based on the cardiac EGM signal and the accelerometer signal, the IMD determines a passive ventricular filling interval for a patient during a first period of time, e.g., during one or more of atrial -only pacing or native sinus rhythm during the first period of time. Based on the passive ventricular filling rate, the IMD configures an interval of pacing, e.g., atrial pacing or ventricular pacing, to facilitate patient-specific TRT administration during a second period of time, e.g., at night for 2 hours or another duration. In some examples, the interval of atrial pacing is a portion, e.g., a percentage, of the passive ventricular filling interval.

[0008] In some examples, the IMD may additionally determine patient state. Based on the patient state, the IMD determines the interval of pacing. As an example, the IMD may determine to provide a relatively short interval of stimulation pacing to facilitate relatively aggressive TRT administration for patients with more severe HFpEF and/or comorbid conditions than for patients with less severe HFpEF and/or no comorbid conditions.

[0009] In one example, an IMD comprises: a plurality of electrodes; sensing circuitry configured to sense a cardiac EGM of a patient via at least some of the electrodes; electrical stimulation circuitry configured to deliver pacing stimulation via at least some of the electrodes; an accelerometer; and processing circuitry configured to: determine an intrinsic timing interval based on the EGM and an accelerometer signal from the accelerometer, wherein the intrinsic timing interval is indicative of a passive ventricular filling interval of the patient during a first period of time; and control electrical stimulation circuitry configured to deliver pacing stimulation via at least some of the electrodes to deliver TRT for a second period of time by at least configuring an interval of the pacing stimulation based on the intrinsic timing interval.

[0010] In another example, a method comprises: sensing, by at least some electrodes of a plurality of electrodes of an IMD, a cardiac EGM of a patient; sensing, by an accelerometer, an accelerometer signal of the patient; determining, by processing circuitry of the IMD, an intrinsic timing interval based on the EGM and the accelerometer signal, wherein the intrinsic timing interval is indicative of a passive ventricular filling interval of the patient during a first period of time; and delivering, by electrical stimulation circuitry configured to deliver pacing stimulation via at least some of the electrodes, TRT for a second period of time by at least configuring an interval of the pacing stimulation based on the intrinsic timing interval.

[0011] In another example, a non-transitory computer-readable medium stores instructions that when executed cause processing circuitry to: determine an intrinsic timing interval based on a cardiac EGM sensed via at least some electrodes of a plurality of electrodes and an accelerometer signal from an accelerometer of an implantable medical device configured to deliver pacing stimulation via at least some of the electrodes, wherein the intrinsic timing interval is indicative of a passive ventricular filling interval of a patient during a first period of time; and control electrical stimulation circuitry configured to deliver pacing stimulation via at least some of the electrodes to deliver TRT for a second period of time by at least configuring an interval of the pacing stimulation based on the intrinsic timing interval. [0012] This summary is intended to provide an overview of the subject matter described in this disclosure. It is not intended to provide an exclusive or exhaustive explanation of the apparatus and methods described in detail within the accompanying drawings and description below. Further details of one or more examples are set forth in the accompanying drawings and the description below.

BRIEF DESCRIPTION OF DRAWINGS

[0013] FIG. 1 illustrates the environment of an example medical device system in conjunction with a patient, in accordance with one or more techniques of this disclosure. [0014] FIG. 2A is a conceptual diagram illustrating an example device implanted in the heart of a patient, in accordance with one or more techniques of this disclosure.

[0015] FIG. 2B is a perspective diagram illustrating an example of the implantable medical device (IMD) of FIG. 1, in accordance with one or more techniques of this disclosure.

[0016] FIG. 2C is a perspective diagram illustrating another example of the device of FIG. 1.

[0017] FIG. 3 is a functional block diagram illustrating an example configuration of the device of FIGS. 2A-2C, in accordance with one or more techniques of this disclosure. [0018] FIG. 4 is a conceptual diagram of the pacing device of FIGS. 1-3 implanted at a target implant site, in accordance with one or more techniques of this disclosure.

[0019] FIG. 5 is an example of a motion sensor signal that may be acquired by a motion sensor of the device of FIGS. 2A-2C over a cardiac cycle in accordance with one or more techniques of this disclosure.

[0020] FIG. 6 is an example of a cardiac electrogram (EGM) signal and a motion sensor signal that may be acquired by electrodes of the device of FIGS. 1 and 2A-2C and a motion sensor of the device of FIGS. 1 and 2A-2C, respectively, in accordance with one or more techniques of this disclosure.

[0021] FIG. 7 is a flow diagram illustrating an example operation for delivering tachycardia remodeling therapy (TRT) by configuring an interval of atrial pacing stimulation based on an intrinsic timing interval, in accordance with one or more techniques of this disclosure. [0022] FIG. 8 is a flow diagram illustrating an example operation for delivering TRT by configuring an interval of atrial pacing stimulation based on a patient state, in accordance with one or more techniques of this disclosure.

[0023] Throughout the disclosure, like reference characters refer to like elements throughout the figures and description.

DETAILED DESCRIPTION

[0024] A variety of types of implantable and external devices are configured to monitor health based on sensed electrocardiograms (ECGs) and, in some cases, other physiological signals, such as an accelerometer signal, a pressure sensor signal, e.g., a blood pressure signal, an impedance signal, and/or a temperature signal. External devices that may be used to non-invasively sense and monitor ECGs and other physiological signals include wearable devices with electrodes configured to contact the skin of a patient, such as patches, watches, rings, necklaces, hearing aids, a wearable cardiac monitor or automated external defibrillator (AED), clothing, car seats, or bed linens. Such external devices may facilitate relatively longer-term monitoring of patient health during normal daily activities.

[0025] Implantable medical devices (IMDs) also sense and monitor ECGs and other physiological signals and detect health events such as episodes of arrhythmia, cardiac arrest, myocardial infarction, stroke, and seizure. Example IMDs include pacemakers and implantable cardioverter-defibrillators, which may be coupled to intravascular or extravascular leads, as well as pacemakers with housings configured for implantation within the heart, which may be leadless, such as the Micra™ AV Leadless Pacemaker and the Micra™ VR Leadless Pacemaker, available from Medtronic, Inc.

[0026] Some HMDs do not provide therapy, such as implantable patient monitors. One example of such an IMD is the Reveal LINQ™ or LINQ II™ insertable cardiac monitors (ICMs), available from Medtronic, Inc., which may be inserted subcutaneously. Such HMDs may facilitate relatively longer-term continuous monitoring of patients during normal daily activities, and may periodically or on demand transmit collected data, e.g., episode data for detected arrhythmia episodes, to a remote patient monitoring system, such as the Medtronic CareLink™ Network via a home monitoring system or a smart phone application. [0027] In some examples, a medical device system including an IMD, e.g., a leadless pacemaker, may provide cardiac pacing therapy to a patient, such as a patient with heart failure with preserved ejection fraction (HFpEF). The system may sense ECGs and, optionally, another physiological signal, such as an accelerometer signal, a pressure sensor signal, an impedance signal, and/or a temperature signal, to determine the patient’s passive ventricular filling interval, e.g., during atrial-only pacing and/or native sinus rhythm, over a first period of time. The system may configure an interval of stimulation pacing, e.g., atrial stimulation pacing or ventricular stimulation pacing, based on the passive ventricular filling interval to facilitate tachycardia remodeling therapy (TRT).

[0028] The techniques of this disclosure may provide one or more technical and clinical advantages. For example, the techniques of this disclosure may be implemented by an IMD that can provide cardiac pacing therapy, e.g., atrial pacing, to the patient. The IMD may configure an interval of the atrial pacing based on a passive ventricular filling interval of the patient during TRT. By configuring the interval of the atrial stimulation pacing based on the passive ventricular filling interval, the techniques of this disclosure may advantageously facilitate patient-specific TRT administration, which may increase TRT efficacy and decrease symptoms and/or complications associated with TRT. In some examples, the IMD that can provide pacing therapy can part of a medical device system including one or more additional IMDs and/or external devices. As an example, the medical device system may include an additional IMD such as an ICM. The ICM may sense the cardiac EGM and/or configure the interval of the atrial pacing based on the passive ventricular filling interval of the patient during TRT. The ICM may be in wireless communication with the IMD providing the pacing therapy and may transmit the sensed data and/or the interval of the atrial pacing to the IMD.

[0029] As another example, the techniques of this disclosure may additionally include monitoring a patient state and configuring the interval of the stimulation pacing based on both the passive ventricular filling interval and the patient state. In some examples, relatively aggressive TRT administration can cause patient sensation and/or patient discomfort. By configuring the interval of atrial pacing based on the patient state, the techniques of this disclosure may advantageously prevent patient sensation associated with relatively aggressive TRT administration in examples in which the patient state is less severe. Additionally, the techniques of this disclosure may facilitate relatively aggressive TRT administration in patients with severe HFpEF. Monitoring the patient state and configuring the interval of the stimulation pacing, e.g., atrial stimulation pacing, based on the patient state may therefore increase TRT efficacy and decrease symptoms and/or complications associated with TRT.

[0030] FIG. 1 illustrates the environment of an example medical device system 2 in conjunction with a patient 4, in accordance with one or more techniques of this disclosure. The example techniques may be used with one or more patient sensing devices, e.g., including a device 104, and, optionally, one or more of an ICM 118 or one or more computing devices, e.g., external programmer 120. Device 104 may be in wireless communication with ICM 118 and/or external programmer 120. Device 104 may be a leadless pacemaker.

[0031] In some examples, device 104 may configure an interval of stimulation pacing for patient 4 and may provide deliver TRT based on the configured interval of stimulation pacing to a heart of patient 4. In some examples, ICM 118 may sense a cardiac EGM and/or one or more physiological signals, e.g., an accelerometer signal, determine the intrinsic timing interval, and/or configure the interval of stimulation pacing. In examples in which ICM 118 senses the cardiac EGM and/or the accelerometer signal, determines the intrinsic timing interval, and/or configures the interval of stimulation pacing, ICM 118 may transmit data corresponding to the sensed signals, the intrinsic timing interval, and/or the interval of stimulation pacing to device 104. Based on the transmitted data, device 104 may administer TRT to the heart of the patient.

[0032] Device 104 and ICM 118 includes electrodes and/or other sensors, e.g., an accelerometer, a gyroscope, a temperature sensor, or a pressure sensor, to sense physiological signals of patient 4 and may configure an interval of stimulation pacing for a heart of patient 4 to facilitate TRT administration.

[0033] ICM 118 may be implanted outside of a thoracic cavity of patient 4 (e.g., subcutaneously in the pectoral location illustrated in FIG. 1). ICM 118 may be positioned near the sternum near or just below the level of the heart of patient 4, e.g., at least partially within the cardiac silhouette, and be configured to sense a cardiac EGM and/or other physiological signals from that position. In some examples, ICM 118 takes the form of the Reveal LINQ™ or LINQ II™ ICM. In some examples, ICM 118 includes additional sensors, such as one or more sensors configured to sense patient activity and/or posture, e.g., one or more accelerometers, heart sounds, respiration, blood pressure (BP), or oxygen saturation. [0034] Although described primarily in the context of examples in which ICM 118 takes the form of an ICM, the techniques of this disclosure may be implemented in systems including any one or more implantable or external medical devices, including monitors, pacemakers, defibrillators (e.g., subcutaneous or substemal), wearable external defibrillators (WAEDs), neurostimulators, drug pumps, patch monitors, or wearable physiological monitors, e.g., wrist or head wearable devices. Examples with multiple HMDs or other sensing devices may be able to collect different data useable by system 2 to facilitate TRT administration.

[0035] In some examples, system 2 includes external programmer 120, which may be a computing device with a display viewable by the user and an interface for providing input to external programmer 120 (i.e., a user input mechanism). External programmer 120 is configured for wireless communication with device 104, and, optionally, ICM 118. External programmer 120 retrieves sensed physiological data from device 104 and/or ICM 118 that was collected and stored by device 104 and/or ICM 118. In some examples, external programmer 120 takes the form of a personal computing device of patient 4. For example, external programmer 120 may take the form of a smartphone of patient 4. In some examples, external programmer 120 may be any computing device configured for wireless communication with device 104 and/or ICM 118, such as a desktop, laptop, or tablet computer. External programmer 120 may communicate with device 104 and/or ICM 118 via near-field communication technologies e.g., inductive coupling, NFC or other communication technologies operable at ranges less than 10-20 cm, and far-field communication technologies, e.g., radiofrequency telemetry according to the Bluetooth® or Bluetooth® Low Energy (BLE) protocols, or other communication technologies operable at ranges greater than near-field communication technologies. When external programmer 120 is configured for use by the clinician, external programmer 120 may be used to transmit instructions to ICM 118 and/or device 104. The clinician may also configure and store operational parameters for device 104 and/or ICM 118 with the aid of external programmer 120. In some examples, external programmer 120 assists the clinician in the configuration of device 104 and/or ICM 118 by providing a system for identifying potentially beneficial operational parameter values.

[0036] Processing circuitry of system 2, e.g., of device 104, ICM 118, external programmer 120, and/or one or more other computing devices (not illustrated in FIG. 1) may be configured to perform the example techniques described herein for configuring TRT based on an intrinsic timing interval based on data collected by device 104 and/or

ICM 118.

[0037] FIG. 2A is a conceptual diagram illustrating an example of device 104 of system 2 implanted in the heart 102 of patient 4, in accordance with one or more aspects of this disclosure. In some examples, system 2 includes only device 104. In other words, in some examples, device 104 senses the cardiac EGM and/or one or more physiological signals, determines the intrinsic timing interval, configures the stimulation pacing interval, and delivers the TRT. In other examples, system 2 includes one or more of ICM 118 or external programmer 120.

[0038] Device 104 is shown implanted in the right atrium (RA) of the patient’s heart 102 in a target implant region 106, such as the triangle of Koch, in heart 102 of the patient with a distal end of device 104 directed toward the left ventricle (LV) of the patient’s heart 102. Although in the example of FIG. 2A the distal end of device 104 is directed toward the LV, the distal end may be directed to other targets, such as interventricular septum of heart 102. Target implant region 106 may lie between the bundle of His and the coronary sinus and may be adjacent the tricuspid valve or at another location in the patient’s heart 102.

[0039] Device 104 includes a distal end 110 and a proximal end 116. Distal end 110 includes a first electrode 112, and a second electrode 114. First electrode 112 may define a helical shape, e.g., as illustrated in FIG. 2A. First electrode 112 extends from distal end 110 and may penetrate through the wall tissue of a first chamber (e.g., the RA in the illustrated example) into wall tissue of a second chamber (e.g., ventricular myocardium 108 of the LV in the illustrated example). Second electrode 114 may be disposed on a ramp extending distally from distal end 110 and is configured to be placed in contact with the wall tissue of the first chamber without penetration of the wall tissue of the first chamber by second electrode 114. Second electrode 114 may contact the wall tissue of the first chamber as first electrode 112 penetrates the wall tissue of the first chamber.

[0040] The configuration of electrodes 112 and 114 illustrated in FIG. 2 A allows device 104 to sense cardiac signals and/or deliver cardiac pacing to multiple chambers of heart 102, e.g., the RA and ventricle(s) in the illustrated example. In this manner, the configuration of electrodes 112 and 114 may facilitate the delivery of A-V synchronous pacing by single device 104 implanted within the single chamber, e.g., the RA. While device 104 is implanted at target implant region 106 to sense in and/or pace the RA and ventricle(s) in the example shown in FIG. 2A, a device having an electrode configuration in accordance with the examples of this disclosure may be implanted at any of a variety of locations to sense in and/or pace any one, two or more chambers of heart 102. For example, device 104 may be implanted at region 106 and/or another region, e.g., near a Bachmann’s bundle of heart 102 or another region in the RA of heart 102, and first electrode 112 may extend into tissue, e.g., myocardial tissue, of the LV or interventricular septum to, for example, facilitate the delivery of A-V synchronous pacing. In examples in which device 104 is implanted near the Bachmann’s bundle of heart 102, device 104 may be an atrial -only leadless pacemaker. Furthermore, a device having an electrode configuration in accordance with the examples of this disclosure may be implanted at any of a variety of locations within the patient for sensing and/or delivery of therapy to other patient tissue. In some examples first electrode 112 may extend into the tissue of heart 102 at region 106 and affix device 104 to the tissue of heart 102.

[0041] First electrode 112 may be disposed on an electrode assembly (e.g., attached to an assembly body of an electrode assembly). The electrode assembly may be removably attached to an elongated housing of device 104 to secure first electrode 112 to device 104. For example, the elongated housing of device 104 may define a recess configured to receive at least a portion (e.g., a proximal portion) of the electrode assembly. Once the electrode assembly is disposed within the recess, the electrode assembly may interface with the elongated housing (e.g., via rotation of the electrode assembly within the recess) to inhibit unintended movement of the electrode assembly, and by extension first electrode 112, relative to the elongated housing of device 104.

[0042] The interface between the electrode assembly and the elongated housing may constrain movement of first electrode 112 relative to the elongated housing in all six degrees of movement and inhibit unintended separation of first electrode 112 from the elongated housing when device 104 is affixed to the tissue of heart 102 at region 106. The six degrees of movement includes movement of first electrode 112 along an x-axis of device 104, movement of first electrode 112 along a y-axis of device 104, movement of first electrode 112 along a z-axis of device 104, rotation of first electrode 112 about the x- axis of device 104, rotation of first electrode 112 about the y-axis of device 104, and rotation of first electrode 112 about the z-axis of device 104.

[0043] Housing of device 104 may house one or more sensors, such as an accelerometer, a pressure sensor, an impedance sensor, a gyroscope, or a temperature sensor. First electrode 112 and second electrode 114 may sense a cardiac EGM of heart 102, and the one or more sensors may sense one or more additional signals, e.g., an accelerometer signal, a pressure sensor signal, an impedance signal, and/or a temperature signal. Based on the cardiac EGM and, in some examples, one or more additional signals, device 104 may determine an intrinsic timing interval, e.g., a passive ventricular filling interval, of the patient. Based on the passive ventricular filling interval, device 104 may control first electrode 112 and second electrode 114 to provide pacing according to a TRT program specific to the patient.

[0044] While the examples of device 104 described herein are described primarily with reference to an electrode assembly including first electrode 112, other example devices may include a fixation assembly instead of and or in addition to an electrode assembly. In such examples, the fixation assembly may include one or more fixation members including one or more tines, a fixation helix, first electrode 112, and/or one or more other fixation mechanisms. In such examples, the fixation assembly may be inserted into and/or secured to device 104 via any of the example techniques described below. For example, the fixation assembly may include a fixation member, wherein a proximal end of the fixation assembly is configured to be retained within a recess of an elongated housing of device 104 to secure the fixation member to the elongated housing, and wherein when the fixation member is secured to the elongated housing, the fixation member extends distally past the distal end of the elongated housing.

[0045] Additionally, although described primarily in the context of examples in which the medical device that provides cardiac pacing and monitors the cardiac electrogram (EGM) and/or other physiological signals takes the form of a leadless pacemaker, the techniques of this disclosure may be implemented in any one or more medical devices and/or medical device systems, including leaded pacemakers. As an example, in addition to device 104, e.g., a leadless pacemaker, a medical device system may include an ICM, e.g., ICM 118 of FIG. 1, configured to monitor the cardiac EGM and/or the other physiological signals, e.g., the accelerometer signal, determine an intrinsic timing interval, and/or configure an interval for the atrial stimulation pacing. ICM 118 and device 104 may be in wireless communication with one another.

[0046] FIG. 2B is a perspective diagram illustrating device 104. Device 104 includes a housing 202 that defines a hermetically sealed internal cavity. Housing 202 may be formed from a conductive material including titanium or titanium alloy, stainless steel, MP35N (a non-magnetic nickel-cobalt-chromium-molybdenum alloy), platinum alloy or other bio-compatible metal or metal alloy, or other suitable conductive material. In some examples, housing 202 is formed from a non-conductive material including ceramic, glass, sapphire, silicone, polyurethane, epoxy, acetyl co-polymer plastics, polyether ether ketone (PEEK), a liquid crystal polymer, other biocompatible polymer, or other suitable non- conductive material.

[0047] Housing 202 extends between distal end 204 and proximal end 206 along longitudinal axis 210. In some examples, housing can be cylindrical or substantially cylindrical but may be other shapes, e.g., prismatic, or other geometric shapes. Housing 202 may include a delivery tool interface member 208 at, for example, proximal end 206, for engaging with a delivery tool during implantation of device 104. At distal end 204, housing 202 may define a face 205 of housing 202. Face 205 may define a distal end major surface. Face 205 may be orthogonal to longitudinal axis 210. In some examples, face 205 may be slanted, e.g., face 205 may define a reference plane that is not orthogonal to longitudinal axis 210.

[0048] Device 104 may include a ramp 212. Ramp 212 extends from a first end 214A that is fixedly attached to housing 202 at or near distal end 204 (e.g., attached to face 205), to a second end 214B that is more distal to first end 214A. Ramp 212 may be disposed radially outwards of first electrode 112 relative to longitudinal axis 210. Ramp 212 may extend around at least a portion of a perimeter of housing 202. Ramp 212 may extend up to 180 degrees around longitudinal axis 210 and along the perimeter of housing 202. Ramp 212 may be integrally formed as a part of the manufacturing of at least a portion of housing 202 (e.g., as a part of the manufacturing of a header defining distal end 204 and face 205 of housing 202). Ramp 212 may be formed via a molding process, via additive manufacturing, or the like. In some examples ramp 212 is formed separately and affixed to face 205 of housing 202 afterwards. Ramp 212 may define a partial helix wound in a same direction and/or in different directions as a helix and/or coil defined by first electrode 112. [0049] Ramp 212 may be an anti -rotation feature. Ramp 212 may increase compression of the tissue and/or increase the friction or other fixation force between the tissue and device 104 and/or first electrode 112. The increase in fixation force(s) may be sufficient to resist rotation of first electrode 112 by movement of the tissue of heart 102 but may not be sufficient to resist rotation of first electrode 112 by the clinician to remove device 104 from heart 102. The amount of force the tissue exerts on first electrode 112 and/or the amount of force ramp 212 exerts on the tissue may vary based on movement of heart 102, movement of device 104, movement of fluid within heart 102, size of heart 102, a number of ramp(s) 212 on face 205, presence of additional anti-rotation feature(s), or the like.

[0050] Second end 214B may define a distal surface orthogonal to longitudinal axis 210. Second electrode 114 may be disposed on the distal surface of second end 214B. In some examples, second electrode 114 may be disposed partially along ramp 212, e.g., between first end 214A and second end 214B.

[0051] First electrode 112 may include one or more coatings (e.g., electrically insulative coating(s)) configured to define a first electrically active region 216, or first electrode 112 may otherwise define first electrically active region 216. In some examples, first electrically active region 216 may be more proximate to the second, e.g., distal, end of first electrode 112. In the example of FIG. 2B, first electrically active region 216 includes the distal end of electrode 112. Second electrode 114 may include one or more coatings configured to define a second electrically active region 217 on an outer surface of electrode 114. In some examples, as illustrated in FIG. 2B, second electrical active region 217 forms a ring around a therapeutic substance dispensing device 215. Second electrode 114 may include, but is not limited to, a button electrode, a spring electrode, or any other suitable type or shape of electrode.

[0052] First and second electrodes 112 and 114 may be formed of an electrically conductive material, such as titanium, platinum, iridium, tantalum, stainless steel, or alloys thereof. First and second electrodes 112 and 114 may be coated with an electrically insulating coating, e.g., a parylene, polyurethane, silicone, epoxy, or other insulating coating, to reduce the electrically conductive active surface area of first and second electrodes 112 and 114, and thereby define first and second electrically active regions 216 and 217. Defining first and second electrically active regions 216 and 217 by covering portions with an insulating coating may increase the electrical impedance of first and second electrodes 112 and 114 and thereby reduce the current delivered during a pacing pulse that captures the cardiac tissue. A lower current drain conserves the power source, e.g., one or more rechargeable or non-rechargeable batteries, of device 104.

[0053] In some examples, first and second electrodes 112 and 114 may have an electrically conducting material coating on first and second electrically active regions 216 and 217 to define the active regions. For example, first and second electrically active regions 216 and 217 may be coated with titanium nitride (TiN). First and second electrodes 112 and 114 may be made of substantially similar material or may be made of different material from one another.

[0054] In the example of FIG. 2B, first electrode 112 takes the form of a helix or a coil. First electrode 112 may be an elongated body defining a helix. In some examples, a helix is an object having a three-dimensional shape like that of a wire wound uniformly in a single layer around a cylindrical or conical surface or mandrel such that the wire would be in a straight line if the surface were unrolled into a plane. First electrode 112 may extend from face 205 from proximal end 220 to a distal end, e.g., defining first electrically active region 216. Proximal end 220 may be a location along first electrode 112 where first electrode 112 extends distally past distal end 204 of device 104.

[0055] Device 104 may include an electrode assembly including first electrode 112. In some examples, first electrode 112 (e.g., a proximal portion of first electrode 112) may be affixed to an assembly body of the electrode assembly. The electrode assembly may interface with a recess within housing 202 to secure first electrode 112 to housing 202 such that at least a portion of first electrode 112 extends distally away from face 205 of housing 202.

[0056] A manufacturing assembly and/or manufacturer may affix and/or detach first electrode 112 from housing 202 via manipulation of the electrode assembly within the recess of housing 202, as an example. In some examples, the manufacturing assembly affixes first electrode 112 to housing 202 by inserting the electrode assembly into the recess of housing 202 and subsequently rotating first electrode 112 about longitudinal axis 210 within the recess to secure first electrode 112 to housing 202. In some examples, the manufacturing assembly performs the reverse procedure to separate and remove first electrode 112 from housing 202. When the electrode assembly is retained within the recess of housing 202, sidewalls of housing 202 defining the recess may interface with the electrode assembly, e.g., interface with tabs extending radially away from an assembly body of the electrode assembly to inhibit movement of the electrode assembly within the recess in multiple degrees of movement, e.g., in up to six degrees of movement.

[0057] Housing 202 may include a compressible element disposed within the recess. When the manufacturing assembly inserts the electrode assembly into the recess, the electrode assembly may at least partially compress the compressible element, which may allow for rotation of fist electrode 112 about longitudinal axis 210 within the recess. Once first electrode 112 is disposed within the recess (e.g., after rotation of first electrode 112), the compressible element may at least partially expand towards an uncompressed configuration and apply forces on the electrode assembly to inhibit unintended movement and/or rotation of first electrode 112 within housing 202.

[0058] Second electrode 114 is disposed on distal end 204 and may include a button electrode, e.g., as illustrated in FIG. 2B, or any other suitable type or shape of electrode. In some examples, device 104 may have a plurality of second electrodes 114 (e.g., two or more second electrodes 114) disposed on distal end 204 of housing 202. The plurality of second electrodes 114 may be equally spaced around a circumference of distal end 204. At least one of the plurality of second electrodes 114 may be disposed on ramps (e.g., on two or more ramps 212). In some examples, each of the plurality of second electrodes 114 may be disposed on ramps. Each ramp 212 may include a single second electrode 114 or two or more second electrodes 114. In some examples, second electrode 114 may be disposed at a predetermined angle away from first end of first electrode 112.

[0059] In some examples, first electrode 112 may include one or more additional antirotation features. The additional anti-rotation features may include a shape of first electrode 112, dimensions (e.g., outer diameter, pitch, or the like) of first electrode 112, one or more features disposed on an outer surface of first electrode 112, or the like. The shape and/or dimensions of first electrode 112 may include a geometric shape of first electrode 112, a varying diameter configuration of first electrode 112, a varying pitch configuration of first electrode 112, a waveform configuration of first electrode 112, or any combination herein. The one or more anti-rotation features disposed on first electrode 112 may include, but are not limited to, elongate darts, barbs, or tines. In some examples, the anti-rotation features include bumps, ridges, and/or other texturing disposed on one or more surfaces of ramp 212 and/or of face 205. The one or more anti-rotation features may resist rotation of first electrode 112 (e.g., by penetrating the tissue, by increasing the friction between first electrode 112 and the tissue, or the like) alone or in conjunction with other anti-rotation features (e.g., ramp 212).

[0060] As illustrated in FIG. 2B, first electrode 112 may be a helix extending distally from face 205 and revolving around longitudinal axis 210 in a counter-clockwise direction (i.e., “wound” in a counter-clockwise direction, and ramp 212 may define partial helix extending distally from face 205 and revolving around longitudinal axis 210 in a clockwise direction, although in other examples the first electrode 112 and ramp 212 may revolve around longitudinal axis 210 in different directions (e.g., first electrode 112 revolves around longitudinal axis 210 in a clockwise direction and ramp 212 revolves around longitudinal axis 210 in a counter-clockwise direction) or first electrode 112 and ramp 212 may revolve around longitudinal axis 210 in a same direction. The helix may extend from a proximal end along and around longitudinal axis 210 towards a distal end. The distal end of the helix may define first electrically active region of first electrode 112. The proximal end of the helix may be retained or otherwise affixed to an assembly body of the electrode assembly, e.g., around a protrusion of the assembly body to affix first electrode 112 to the assembly body. The helix may define an inner diameter sized to facilitate insertion of an installation tool into an inner channel defined by the helix. The inner diameter may at least about 2.946 millimeters (mm), or about 0.116 inches (in). [0061] First and second electrodes 112 and 114 may vary in size and shape in order to enhance tissue contact of first and second electrically active regions 216 and 217. For example, first electrodes 112 may have a round cross-section or could be made with a flatter cross-section (e.g., oval or rectangular) based on tissue contact specifications. In some examples, second electrode 114 may have an outer surface that varies in size and shape (e.g., an oval outer surface, an outer surface with a larger diameter, or the like) in order to enhance tissue contact of second electrically active region 217.

[0062] The size and shape of first electrode 112 may be determined at least in part by stiffness requirements. For example, stiffness requirements may vary based on the expected implantation requirements, including the tissue into which the electrodes are implanted or contact, as well as how long device 104 is intended to be implanted.

[0063] The distal end of first electrode 112 can have a conical, hemi-spherical, or slanted edge distal tip with a narrow tip diameter, e.g., less than 1 millimeter (mm), for penetrating into and through tissue layers. In some examples, the distal end of first electrode can be a sharpened or angular tip or sharpened or beveled edges, but the degree of sharpness may be constrained to avoid a cutting action that could lead to lateral displacement of the distal end of first electrode 112 and undesired tissue trauma. In some examples, first electrode 112 may have a maximum diameter at its base that interfaces with housing distal end 204. In such examples, the outer diameter of the helix defined by first electrode 112 may decrease from housing distal end 204 to the distal end of first electrode 112. In such examples, the distal end of first electrode 112 may define an inner diameter of at least about 2.946 mm. In some examples, the diameter of first electrode 112 may vary from housing distal end 204 to the distal end of first electrode 112. The varying diameter may cause first electrode 112 to resist rotation within the tissue of heart 102. [0064] The outer dimensions of first electrode 112 can be substantially straight and cylindrical, with first electrode 112 being rigid in some examples. In some examples, first electrode 112 may have flexibility in lateral directions, being non-rigid to allow some flexing with heart motion. In a relaxed state, when not subjected to any external forces, first electrode 112 can be configured to maintain a distance between first electrically active region 216 and housing distal end 204.

[0065] Distal end of first electrode 112 can pierce through one or more tissue layers to position first electrically active region 216 within a desired tissue layer, e.g., the ventricular myocardium 108 or interventricular septum. Accordingly, first electrode 112 extends a distance from housing distal end 204 corresponding to the expected pacing site depth and may have a relatively high compressive strength along its longitudinal axis, which may be substantially similar to or coincident with longitudinal axis 210, to resist bending in a lateral or radial direction when a longitudinal, axial, and/or rotational force is applied, for example, to the proximal end 206 of housing 202 to advance device 104 into the tissue at target implant region 106. By resisting bending in a lateral or radial direction, first electrode 112 can maintain a spacing between a plurality of windings of first electrode 112 when first electrode 112 is a helix electrode. The spacing may be a predetermined pitch of first electrode 112 and may vary from distal end 204 to the distal end of first electrode 112. First electrode 112 may be longitudinally non-compressible. First electrode 112 may also be elastically deformable in lateral or radial directions when subjected to lateral or radial forces, however, to allow temporary flexing, e.g., temporary flexing with tissue motion, but returns to its normally straight position when lateral forces diminish. In some examples, when first electrode 112 is not exposed to any external force, or to only a force along its longitudinal axis (substantially similar to or coincident with longitudinal axis 210), first electrode 112 retains a straight, linear configuration as shown. [0066] All, substantially all, or a portion of housing 202 may function as an electrode 218, e.g., an anode, during pacing and/or sensing. In some examples, electrode 218 can circumscribe a portion of housing 202 at or near proximal end 206. Electrode 218 can fully or partially circumscribe housing 202. FIG. 2B shows electrode 218 extending as a singular band. Electrode 218 can also include multiple segments spaced a distance apart along a longitudinal axis 210 of housing 202 and/or around a perimeter of housing 202. In some examples, electrode 218 may be disposed on face 205 or on another ramp 212 disposed on face 205. For example, electrode 114 may be disposed on a first ramp 212 and electrode 218 may be disposed on a second ramp (not shown).

[0067] When housing 202 is formed from a conductive material, such as a titanium alloy, portions of housing 202 may be electrically insulated by a non-conductive material, such as a coating of parylene, polyurethane, silicone, epoxy or other biocompatible polymer, or other suitable material. For the portions of housing 202 without the non- conductive material, one or more discrete areas of housing 202 with conductive material can be exposed to define electrode 218.

[0068] When housing 202 is formed from a non-conductive material, such as a ceramic, glass or polymer material, an electrically-conductive coating or layer, such as a titanium, platinum, stainless steel, alloys thereof, a conductive material may be applied to one or more discrete areas of housing 202 to form electrode 218.

[0069] In some examples, electrode 218 may be a component, such as a ring electrode, that is mounted or assembled onto housing 202. Electrode 218 may be electrically coupled to internal circuitry of device 104 via electrically-conductive housing 202 or an electrical conductor when housing 202 is a non-conductive material. In some examples, electrode 218 is located proximate to proximal end 206 of housing 202 and can be referred to as a proximal housing-based electrode. Electrode 218 can also be located at other positions along housing 202, e.g., located proximately to distal end 204 or at other positions along longitudinal axis 210.

[0070] In some examples, second electrode 114 or electrode 218 may be paired with first electrode 112 for sensing ventricular signals and delivering ventricular pacing pulses. In some examples, second electrode 114 may be paired with electrode 218 or first electrode 112 for sensing atrial signals and delivering pacing pulses to atrial tissue (e.g., to the atrial myocardium) in target implant region 106. In other words, electrode 218 may be paired, at different times, with first electrode 112 and/or second electrode 114 for either ventricular or atrial functionality, respectively, in some examples. In some examples, first and second electrodes 112 and 114 may be paired with each other, with different polarities, for atrial and ventricular functionality.

[0071] In some examples, second electrode 114 may be configured as an atrial cathode electrode for delivering pacing pulses to the atrial tissue, e.g., at target implant region 106 in combination with electrode 218. Second electrode 114 and electrode 218 may also be used to sense atrial P-waves for use in controlling atrial pacing pulses (delivered in the absence of a sensed P-wave) and for controlling atrial-synchronized ventricular pacing pulses delivered using first electrode 112 as a cathode and electrode 218 as the return anode.

[0072] A distal end of first electrode 112 can be configured to rest within a ventricular myocardium of the patient, and second electrode 114 and ramp 212 can be configured to contact an atrial endocardium of the patient. Device 104 may include more or fewer electrodes than two electrodes. In some examples, device 104 may include one or more second electrodes 114 along housing distal end 204. For example, device 104 may include two or three electrodes configured for atrial functionality like second electrode 114, and the three electrodes may be substantially similar or different from one another. Spacing between a plurality of second electrodes 114 may be at an equal or unequal distance. Second electrode(s) 114 may be individually selectively coupled to sensing and/or pacing circuitry enclosed by housing 202 for use as an anode with first electrode 112 or as an atrial cathode electrode or may be electrically common and not individually selectable. In some examples, in place of first electrode 112, device 104 may include a fixation element (not shown) of similar shape and mechanical properties, but without an electrically active region or electrode formed thereon or borne thereby; in such examples, electrically active region 216 can be positioned on a separate member and/or on the housing 202.

[0073] Inflammation of patient tissue may result from interaction with device 104. For example, penetration of tissue by first electrode 112 and/or contact between tissue and second electrode 114 may result in inflammation of the tissue. Inflammation of patient tissue proximate to first and second electrodes 112 and 114 may result in higher thresholds for stimulation delivered to the tissue to activate, or capture, the tissue. Higher capture thresholds may, in turn, increase the consumption of a power source of device 104 associated with delivery of the stimulation.

[0074] In some examples device 104 includes one or more therapeutic substance dispensing devices 215 on face 205, such as within a recess defined by second electrode 114 and/or on ramp 212. The steroid may mitigate inflammation of patient tissue resulting from interaction with device 104. Therapeutic substance dispensing devices 215 may be configured to elute one or more steroids to tissue in proximity to therapeutic substance dispensing devices 215 over time. In some examples, steroid eluting elements 215 comprise one or more monolithic controlled release devices (MCRDs). [0075] In some examples, device 104 includes one or more therapeutic substance dispensing devices 215 configured to elute one or more steroids to tissue proximate to first electrode 112. Therapeutic substance dispensing devices 215 may be disposed within a recess defined by second electrode 114. In some examples, therapeutic substance dispensing devices 215 may be disposed at a center of face 205, e.g., within recess defined by housing 202, and/or on ramp 212, e.g., between first end 214A and second end 214B. [0076] Ramp 212 may cause second electrode 114 to maintain consistent contact with the wall tissue by, for example, raising second electrode 114 from face 205 by a fixed distance. Consistent contact between second electrode 114 and the wall tissue may improve electrical conductivity and the delivery of electrical signals from second electrode 114 to the wall tissue. In some examples, where device 104 is an implantable pacing device, the consistent contact between second electrode 114 and the wall tissue may reduce and/or maintain a pacing threshold for a chamber (e.g., the right atrium) of heart 102.

[0077] In some examples, device 104 includes a sensor 222, e.g., an accelerometer, a pressure sensor, an impedance sensor, a gyroscope, and/or a temperature sensor, housed within housing 202. Sensor 222 may be configured to sense mechanical activity of heart 102. In examples in which sensor 222 is an accelerometer, the accelerometer may sense an accelerometer signal indicative of mechanical activity of heart 102. In some examples, the signal may provide information indicative of an intrinsic timing interval, e.g., a passive ventricular filling interval of heart 102.

[0078] FIG. 2C is a perspective diagram illustrating another example of device 104 of FIG. 2A. In the example illustrated in FIG. 2C, second electrode 114 is disposed directly on face 205 and separate from ramp 212. In such examples, second electrode 114 may be a button electrode, a wire electrode, or any other type of electrode. Second electrode 114 may extend distally away from face 205 or may be flush with face 205. In the example illustrated in FIG. 2C, ramp 212 may interface with tissue at target implant region 106 to inhibit unintended rotation of device 104 relative to the tissue. Examples of second electrode 114 are described in commonly-owned U.S. provisional application no. 63/625,461 filed January 26, 2024 and entitled “DISTAL END FIXATION FOR IMPLANTABLE MEDICAL DEVICE”, the entirety of each of which is incorporated herein by reference. [0079] FIG. 3 is a functional block diagram illustrating an example configuration of device 104. As illustrated in FIG. 3, device 104 include electrodes 112, 114, and 218, which may be configured as described with respect to FIGS. 1 and 2A-2C. For example, as described with respect to FIGS. 1 and 2, first electrode 112 may be configured to extend from distal end 204 of housing 202 and may penetrate through the wall tissue of a first chamber (e.g., the RA) into wall tissue of a second chamber (e.g., the LV). Second electrode 114 extends from distal end 204 of housing 202 and may be configured to maintain contact with the wall tissue of the first chamber without penetration of the wall tissue of the first chamber by second electrode 114. Second electrode 114 may maintain contact in this manner by virtue of being disposed in and/or on ramp 212 or another ramp as described herein. Ramp 212 may position second electrode 114 at a distance (e.g., distance 226) away from face 205, thereby causing second electrode 114 to maintain consistent contact with the wall tissue when first electrode 112 is secured within the wall tissue.

[0080] In the example shown in FIG. 3, device 104 includes switch circuitry 302, sensing circuitry 304, electrical stimulation circuitry 306, sensor(s) 308, processing circuitry 310, telemetry circuitry 312, memory 314, and power source 316. The various circuitry may be, or include, programmable or fixed function circuitry configured to perform the functions attributed to respective circuitry. Memory 314 may store computer- readable instructions that, when executed by processing circuitry 310, cause device 104 to perform various functions. Memory 314 may be a storage device or other non-transitory medium. The components of device 104 illustrated in FIG. 3 may be housed within housing 202.

[0081] Electrical stimulation circuitry 306 generates electrical stimulation signals, e.g., cardiac pacing pulses. Switch circuitry 302 is coupled to electrodes 112, 114, and 218, may include one or more switch arrays, one or more multiplexers, one or more switches (e.g., a switch matrix or other collection of switches), one or more transistors, or other electrical circuitry. Switch circuitry 302 is configured to direct stimulation signals from electrical stimulation circuitry 306 to a selected combination of electrodes 112, 114, and 218, having selected polarities to selectively deliver pacing pulses to the RA, ventricles, or interventricular septum of heart 102. For example, in order to pace one or both of the ventricles, switch circuitry 302 may couple first electrode 112, which has penetrated to wall tissue of a ventricle or the intraventricular septum, to electrical stimulation circuitry 306 as a cathode, and one or both of second electrode 114 or electrode 218 to electrical stimulation circuitry 306 as an anode. As another example, in order to pace the RA, switch circuitry 302 may couple second electrode 114, which maintains contact with the RA endocardium, to electrical stimulation circuitry 306 as a cathode, and one or both of first electrode 112 or electrode 218 to electrical stimulation circuitry 306 as an anode.

[0082] Each of electrodes 112, 114, and 218 may be coupled to switch circuitry 302 via a corresponding feedthrough assembly. In some examples, each feedthrough assembly may be substantially straight (e.g., along longitudinal axis 210). In some examples, such as when distal end 204 of housing 202 is removable from housing 202 (e.g., when distal end 204 is a removable header), the feedthrough assemblies may be offset to allow for removal of distal end 204. For example, when a header defining distal end 204 is configured to be removably secured to housing 202, such as via a turn-lock mechanism, the feedthrough assemblies may be offset from longitudinal axis 210 to allow the header to turn relative to housing 202.

[0083] Switch circuitry 302 may also selectively couple sensing circuitry 304 to selected combinations of electrodes 112, 114, and 218 to selectively sense the electrical activity of either the RA or ventricles of heart 102, e.g., sense an ECG signal. Sensing circuitry 304 may include filters, amplifiers, analog-to-digital converters, or other circuitry configured to sense cardiac electrical signals via electrodes 112, 114, and/or 218. For example, switch circuitry 302 may couple each of first electrode 112 and second electrode 114 (in combination with electrode 218) to respective sensing channels provided by sensing circuitry 304 to respectively sense either ventricular or atrial cardiac electrical signals. In some examples, sensing circuitry 304 is configured to detect events, e.g., depolarizations, within the cardiac electrical signals, and provide indications thereof to processing circuitry 310. In this manner, processing circuitry 310 may determine the timing of atrial and ventricular depolarizations, and control the delivery of cardiac pacing, e.g., AV synchronized cardiac pacing, based thereon. Processing circuitry 310 may include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), discrete logic circuitry, or any other processing circuitry configured to provide the functions attributed to processing circuitry 310 herein may be embodied as firmware, hardware, software, or any combination thereof. [0084] Sensor(s) 308 may include one or more sensing elements that transduce patient physiological activity to an electrical signal to sense values of a respective patient parameter. Sensor(s) 308 may include one or more accelerometers, pressure sensors, impedance sensors, optical sensors, chemical sensors, gyroscopes, temperature sensors, or any other types of sensors. Sensor(s) 308 may output patient parameter values that may be used as feedback to control sensing and delivery of therapy by device 104.

[0085] In examples in which sensor(s) 308 includes an accelerometer, the accelerometer may sense a signal indicative of mechanical activity of heart 102, which, in combination with an ECG signal sensed via at least some of electrodes 112, 114, and 218, may provide information indicative of an intrinsic timing interval, e.g., a passive ventricular filling interval, of heart 102 of the patient. In some examples, switch circuitry 302 selectively couples sensing circuitry 304 to selected combinations of electrodes 112, 114, and 218 during a first period of time including atrial-only pacing or during normal patient sinus rhythm, and the accelerometer senses the signal indicative of mechanical activity of heart 102. Based on the signals, processing circuitry 310 may determines the passive ventricular filling interval of heart 102 of the patient. Processing circuitry 310 configures an interval of atrial pacing stimulation based on the passive ventricular filling interval to provide TRT to the patient and controls electrical stimulation circuitry 306 to generate electrical stimulation signals, and switch circuitry 302 directs stimulation signals from electrical stimulation circuitry 306 to a selected combination of electrodes 112, 114, and 218 during a second time period.

[0086] Telemetry circuitry 312 supports wireless communication between device 104 and an external programmer 120 (of FIG. 1) or another computing device under the control of processing circuitry 310. Processing circuitry 310 of device 104 may receive, as updates to operational parameters from the computing device, and provide collected data, e.g., sensed heart activity or other patient parameters, via telemetry circuitry 312. Telemetry circuitry 312 may additionally or alternatively communicate with an ICM, e.g., ICM 118, or another IMD configured to monitor the cardiac EGM and the accelerometer signal, determine the intrinsic timing interval, and/or configure the interval for atrial pacing stimulation. Telemetry circuitry 312 may accomplish communication by radiofrequency (RF) communication techniques via an antenna (not shown).

[0087] Power source 316 delivers operating power to various components of device 104. Power source 316 may include a rechargeable or non-rechargeable battery and a power generation circuit to produce the operating power. Recharging may be accomplished through proximal inductive interaction between an external charger and an inductive charging coil within device 104.

[0088] In examples in which system 2 includes optional ICM 118, ICM 118 may be configured similarly to the example configuration of device 104 provided in FIG. 3. In some examples, ICM 118 may include electrodes 112, 114, and 218, as well as sensing circuitry 304, electrical sensor(s) 308, processing circuitry 310, telemetry circuitry 312, memory 314, and power source 316, and may not include switch circuitry 302 or electrical stimulation circuitry 306.

[0089] FIG. 4 is a conceptual diagram of device 104 implanted at target implant region 106. First electrode 112 may be inserted in a manner, e.g., a manner similar to rotating and advancing a threaded screw, such that tissue becomes engaged with the helix of first electrode 112. As first electrode 112 becomes engaged with tissue, first electrode 112 pierces into the tissue at target implant region 106 and advances through atrial myocardium 406 and central fibrous body 402 to position first electrically active region 216 in ventricular myocardium 108 as shown in FIG. 4. In some examples, first electrode 112 penetrates the interventricular septum. In some examples, first electrode 112 does not perforate either of the ventricular endocardial or epicardial surface.

[0090] In some examples, manual pressure applied to the housing proximal end 206 via, for example, an advancement tool, provides the longitudinal force to pierce the cardiac tissue at target implant region 106. In some examples, actuation of an advancement tool rotates device 104 and first electrode 112 configured as a helix about longitudinal axis 210. The rotation of the helix about the longitudinal axis 210 advances first electrode 112 through atrial myocardium 406 and central fibrous body 402 to position first electrically active region 216 in ventricular myocardium 108 as shown in FIG. 4.

[0091] As first electrode 112 advances into the tissue, the distance between second electrode 114 on ramp 212 and atrial endocardium 404 decreases until second electrode 114 and ramp 212 contact, and, in some examples, press against, the surface of atrial endocardium 404. Second electrode 114 and ramp 212 may press against the surface of atrial endocardium 404 and compress the wall tissue. The compression of the wall tissue may increase friction between ramp 212 and the wall tissue and prevent or inhibit rotation of device 104 due to movement of tissue of heart 102 (e.g., movement of ventricular myocardium 108, atrial myocardium 406, central fibrous body 402, or the like) or blood flow during cardiac function. Ramp 212 pressing against heart tissue may cause heart tissue to become engaged with second electrically active region 217 of second electrode 114 disposed on ramp 212. Second electrode 114 is held in contact with atrial endocardium 404 by first electrode 112 and ramp 212. Retraction of second electrode 114 from the surface of atrial endocardium 404 may be prevented or inhibited by first electrode 112 and ramp 212.

[0092] Ramp 212 can be the sole anti-rotation feature of device 104 in some examples. In some examples, device 104 may have one or more additional anti-rotation features defined and/or disposed on first electrode 112, on face 205, and/or on ramp 212. The distance by which first electrode 112 extends from housing 202 can be selected so first electrically active region 216 reaches an appropriate depth in the tissue layers to reach the targeted pacing and sensing site, in this case in ventricular myocardium 108, without puncturing all the way through into an adjacent cardiac chamber.

[0093] Target implant region 106 in some pacing applications is along atrial endocardium 404, substantially inferior to the AV node and bundle of His. First electrode 112 can have a length that penetrates through atrial endocardium 404 in target implant region 106, through the central fibrous body 402 and into ventricular myocardium 108 without perforating through the ventricular endocardial surface. In some examples, when the full length of first electrode 112 is fully advanced into target implant region 106, first electrically active region 216 rests within ventricular myocardium 108 and second electrode 114 is positioned in intimate contact with atrial endocardium 404. First electrode 112 may extend from housing distal end 204 approximately 3 mm to 12 mm in various examples. In some examples, first electrode 112 may extend a distance from distal end 204 by at least 3 mm, at least 3 mm but less than 20 mm, less than 15 mm, less than 10 mm, or less than 8 mm in various examples. The diameter of an elongated body defining first electrode 112 may be 2 mm or less, e.g., may be 1 mm or less or may be 0.6 mm or less. An outer diameter of the helix or coil defined by first electrode 112 may be 4 mm or less.

[0094] FIG. 5 is an example of a motion signal 550, e.g., an accelerometer signal, that may be acquired by sensors(s) 308 of device 104 of FIGS. 1 and 2 over a cardiac cycle in accordance with the techniques of the disclosure. Vertical dashed lines 552 and 562 denote the timing of two consecutive ventricular events (a passive ventricular depolarization or a ventricular pace), marking the respective beginning and end of the ventricular cycle 551. The motion signal includes an Al event 554, an A2 event 556, an A3 event 558 and an A4 event 560. Al event 554 is an accelerometer signal (in this example in which motion sensor(s) 308 includes an accelerometer) that occurs during ventricular contraction and marks the approximate onset of ventricular mechanical systole. The Al event is also referred to herein as a “ventricular contraction event.” The A2 event 556 is an acceleration signal that occurs during ventricular relaxation and marks the approximate offset or end of ventricular mechanical systole. A2 event 556 is also referred to herein as the “ventricular relaxation event.” A3 event 558 is an acceleration signal that occurs during passive ventricular filling and marks ventricular mechanical diastole. A3 event 558 is also referred to herein as the “ventricular passive filling event.” Since A2 event 556 occurs with the end of ventricular systole, it is an indicator of the onset of ventricular diastole. A3 event 558 occurs during ventricular diastole. As such, A2 event 556 and A3 event 558 may be collectively referred to as ventricular mechanical diastolic events because both are indicators of the ventricular diastolic period. A4 event 560 is an accelerometer signal that occurs during atrial contraction and active ventricular filling and marks atrial mechanical systole. A4 event 560 may also referred to herein as the “atrial systolic event” or merely the “atrial event.”

[0095] Processing circuitry 310 may be configured to determine one or more of the Al, A2, A3, and A4 events from motion signal 550, for at least some ventricular cardiac cycles, e.g., for atrial-only paced cardiac cycles or normal sinus rhythm cycles of heart 102 of the patient during a first period of time, for use in detecting an event, e.g., A3 event 560, and configuring an interval for atrial pacing stimulation for delivery during a second period of time, e.g., during TRT administration. In examples in which processing circuitry 310 detects A3 event 560 to configure the interval for atrial pacing stimulation, processing circuitry may additionally determine Al event 554, A2 event 556, and/or A4 event 560 to avoid false detection of A3 event 558 and promote reliable A3 event 558 detection for proper timing of pacing stimulation, e.g., atrial or ventricular pacing stimulation, pulses. [0096] FIG. 6 is an example of a cardiac EGM signal, e.g., an atrial cardiac EGM signal, that may be acquired by electrodes of the device of FIGS. 1 and 2 and a physiological sensor signal, e.g., a motion sensor signal, that may be acquired by a motion sensor, e.g., an accelerometer, of the device of FIGS. 1 and 2, respectively, in accordance with one or more techniques of this disclosure. In examples in which device 104 senses a cardiac EGM, e.g., an atrial cardiac EGM, and an accelerometer signal, processing circuitry 310 may determine an intrinsic timing interval, e.g., a passive ventricular filling interval, based on the cardiac EGM and the accelerometer signal. Cardiac EGM signal 622 and accelerometer signal 612 may correspond to a same point in time of the first period of time. Cardiac EGM signal 622 includes an R-wave 602. Accelerometer signal 612 includes an Al event 604, an A2 event 606, an A3 event 608, and an A4 event 610. Each of Al event 604, A2 event 606, A3 event 608, and A4 event 610 may be substantially similar to Al event 554, A2 event 556, A3 event 558, and A4 event 560, respectively. To determine the intrinsic timing interval, processing circuitry may determine a time interval between R-wave 602 and A3 event 608. In some examples, the intrinsic timing interval 614 is the time between the peak of R-wave 602 and the end of A3 event 608. Processing circuitry 310 additionally determines an A3 duration window 624 of A3 event 608. In some examples, processing circuitry 310 may additionally or alternatively determine peakpeak timing interval 618, i.e., the time between the peak of R-wave 602 and the peak of A3 event 608. In some examples, processing circuitry determines an area under the curve (AUC) 620 of A3 event 608.

[0097] Based on the intrinsic timing interval 614, e.g., the passive ventricular filling interval, processing circuitry 310 configures an interval of atrial pacing stimulation for TRT administration during the second period of time. In some examples, to configure the interval of pacing stimulation, e.g., atrial pacing stimulation, processing circuitry 310 determines to adjust atrial pacing, e.g., increase the atrial pacing rate, to truncate A3 duration window 624 and therefore intrinsic timing interval 614.

[0098] In some examples, processing circuitry 310 sets the interval of atrial pacing stimulation based on AUC 620. In some examples, to set the interval of atrial pacing stimulation, processing circuitry 310 increases the atrial pacing stimulation rate until an adjusted AUC is a certain percentage less than AUC 620. In some examples, processing circuitry 310 sets the interval of atrial pacing stimulation based on a percentage of intrinsic timing interval 614, such as 70% of intrinsic timing interval 614. In some examples, to set the interval of atrial pacing stimulation, processing circuitry 310 increases the atrial pacing stimulation rate, i.e., decreases the atrial pacing stimulation interval, until an adjusted A3 duration window during the second period decreases to a certain percentage of A3 duration window 624, e.g., 70% of the A3 duration window 624. In some examples, to set the interval of atrial pacing stimulation, processing circuitry 310 increases the atrial pacing stimulation rate, i.e., shortens the atrial pacing stimulation interval, until an A3 duration window during the second period decreases to a portion 616 of A3 duration window 624. Portion 616 may correspond to an interval between a percentage, e.g., 30%, of a rise time and a percentage e.g., 70%, of a fall time of A3 event 608. In some examples, processing circuitry 310 sets the atrial pacing stimulation interval by selecting an atrial pacing stimulation interval that is shorter than intrinsic timing interval 614 by a predetermined amount, e.g., 30 milliseconds, for the TRT delivery. In some examples, processing circuitry 310 determines to switch between one or more methods of setting the interval of atrial pacing stimulation, e.g., based on a patient status, such as an HFpEF severity level, based on clinician preferences, and/or based on an amount of time device 104 has been implanted. For example, processing circuitry 310 may initially set the atrial pacing stimulation interval as 30 milliseconds shorter than intrinsic timing interval 614 during the second period and may subsequently switch to decreasing the atrial pacing stimulation interval until the adjusted A3 duration window decreases to 70% of A3 duration window 624 during a subsequent second period. In some examples, the extent to which processing circuitry 310 decreases the atrial pacing stimulation interval may be patient-specific. In some examples, processing circuitry 310 additionally determines the atrial pacing stimulation interval based on a patient state. The patient state may be indicative of a severity of the patient’s HFpEF, the patient’s comorbid conditions, the patient’s age, etc. In some examples, processing circuitry 310 may determine to deliver relatively aggressive TRT to patients with relatively severe HFpEF. For example, processing circuitry 310 may decrease the atrial pacing stimulation interval to a greater extent, e.g., until the adjusted A3 duration window is decreased to 50% of A3 duration window 624, for patients with relatively severe HFpEF relative to patients with less severe HFpEF. As an example, processing circuitry 310 may decrease the atrial pacing stimulation interval until the adjusted A3 duration window decreases to 50% of A3 duration window 624 for patients with relatively severe HFpEF and to 70% of A3 duration window 624 for patients with less severe HFpEF. In some examples, more aggressive TRT may cause increased patient sensation and/or discomfort. Processing circuitry 310 may determine to provide less aggressive TRT to patients with less severe HFpEF to prevent patient sensation of the TRT. Processing circuitry 310 may determine to provide more aggressive TRT to patients with more severe HFpEF due to the relatively high importance of remodeling the heart. [0099] FIG. 7 is a flow diagram illustrating an example operation for delivering tachycardia remodeling therapy (TRT) by configuring an interval of pacing stimulation, e.g., atrial pacing stimulation, based on an intrinsic timing interval, in accordance with one or more techniques of this disclosure. The example of FIG. 7 will be described with respect to processing circuitry 310, but other processing circuitry of a medical device system, such as processing circuitry of ICM 118 or an external device, such as external programmer 120, may be used in addition to processing circuitry 310 in other examples. In some examples, processing circuitry of different devices may be used to collectively perform this technique in a distributed computing model.

[00100] Processing circuitry 310 determines an intrinsic timing interval based on a cardiac EGM signal, and, in some examples, an additional signal, such as an accelerometer signal, over a first period of time (702). In examples in which processing circuitry 310 determines the intrinsic timing interval based on a cardiac EGM signal and an accelerometer signal, processing circuitry 310 may determine the intrinsic timing interval using the techniques described in FIG. 7. Processing circuitry 310 may determine an average intrinsic timing interval, e.g., an average passive ventricular filling interval, over a first period of time. During the first period of time, processing circuitry 310 may determine the intrinsic timing interval during atrial-only pacing and/or during period of normal sinus rhythm within the first period of time. The first period of time may include the majority of an overall period of time, such as 20 hours to 22 hours of a day. Processing circuitry 310 controls a selected combination of electrodes 112, 114, and 218, i.e., at least some of the electrodes, to deliver TRT for a second period of time, e.g., 2 hours to 4 hours, by configuring an interval of the atrial pacing stimulation based on the intrinsic timing interval (704). To control the selected combination of electrodes 112, 114, and 218, processing circuitry 310 may control electrical stimulation circuitry 306 to generate atrial pacing pulses according to an interval of atrial stimulation pacing based on the intrinsic timing interval. Switch circuitry 302 directs the atrial pacing pulses from signal generation circuitry 306 to the selected combination of electrodes 112, 114, and 218. In some examples, the second period of time corresponds to a period of time in which the patient is resting, e.g., sleeping. In some examples, processing circuitry 310 may determine a patient activity level to confirm the patient is resting, before delivering TRT during the second period of time based on a physiological signal, e.g., an accelerometer signal. In some examples, the second period of time is at night. By delivering TRT at while the patient is sleeping and/or at night, the techniques of this disclosure may advantageously prevent patient sensation of TRT and/or prevent TRT from impacting patient activity. [0100] In some examples, processing circuitry 310 may configure the atrial stimulation pacing interval based on the cardiac EGM signal and may not use an additional signal. Processing circuitry 310 may estimate an intrinsic ventricular filling interval based on one or more features of the cardiac EGM signal and the additional one or more physiological signals. Processing circuitry 310 may configure the atrial stimulation pacing interval based on the cardiac EGM signal and a pressure signal, e.g., a blood pressure signal, an impedance signal, and/or a temperature signal, in addition to or alternatively to the accelerometer signal. In examples in which processing circuitry 310 configures the atrial stimulation pacing interval based on the pressure signal and/or the impedance signal, processing circuitry 310 may determine one or more timing intervals, amplitudes, AUCs, or rises and falls in the pressure signal and/or the impedance signal. [0101] In examples in which processing circuitry of ICM 118 is used, processing circuitry of ICM 118 may be configured to perform one or more of the steps of FIG. 7. As an example, processing circuitry of ICM 118 may perform steps 702 and 704 and may additionally transmit the configured the atrial stimulation pacing interval to processing circuitry 310. As another example, processing circuitry of ICM 118 may perform step 702 and may transmit the sensed signals to processing circuitry 310 to configure the atrial stimulation pacing interval based on the cardiac EGM and the additional signal, e.g., the accelerometer signal.

[0102] FIG. 8 is a flow diagram illustrating an example operation for delivering TRT by configuring an interval of pacing stimulation, e.g., atrial pacing stimulation, based on a patient state, in accordance with one or more techniques of this disclosure. The example of FIG. 7 will be described with respect to processing circuitry 310, but other processing circuitry of a medical device system, such as processing circuitry of ICM 118 or an external device, such as external programmer 120, may be used in other examples. In some examples, processing circuitry of different devices may be used to collectively perform this technique in a distributed computing model.

[0103] Processing circuitry 310 determines a patient state of the patient (802). In some examples, the patient state may be based on a severity level of HFpEF associated with the patient. In some examples, the patient state may be based on whether the patient has one or more comorbid conditions. In some examples, the patient state may be based on patient age and/or body mass index (BMI). In some examples, the patient state may be based on how long the patient has been periodically undergoing TRT, e.g., based on how long device 104 has been implanted in the patient.

[0104] Processing circuitry 310 controls the selected combination of electrodes 112, 114, and 218 to deliver TRT for a second period of time by configuring the interval of the atrial pacing stimulation based on the patient state in addition to configuring the interval of the atrial pacing stimulation based on the intrinsic timing interval (804). To control the selected combination of electrodes 112, 114, and 218, processing circuitry 310 may control electrical stimulation circuitry 306 to generate atrial pacing pulses according to an interval of atrial stimulation pacing based on the patient state and the intrinsic timing interval. Switch circuitry 302 directs the atrial pacing pulses from signal generation circuitry 306 to the selected combination of electrodes 112, 114, and 218. In some examples, processing circuitry 310 may determine to deliver relatively aggressive TRT to patients with relatively severe HFpEF. For example, processing circuitry 310 may decrease the atrial pacing stimulation interval to a greater extent for patients with relatively severe HFpEF relative to patients with less severe HFpEF. As an example, processing circuitry 310 may decrease the atrial pacing stimulation interval until the adjusted A3 duration window decreases to 50% of A3 duration window 624 of FIG. 6 for patients with relatively severe HFpEF and to 70% of A3 duration window 624 for patients with less severe HFpEF. In some examples, more aggressive TRT may cause increased patient sensation and/or discomfort. Processing circuitry 310 may determine to provide less aggressive TRT to patients with less severe HFpEF to prevent patient sensation of the TRT. Processing circuitry 310 may determine to provide more aggressive TRT to patients with more severe HFpEF due to the relatively high importance of remodeling the heart at a faster rate to prevent further increases in severity of HFpEF.

[0105] Example 1. An implantable medical device (IMD) comprising: a plurality of electrodes; sensing circuitry configured to sense a cardiac electrogram (EGM) of a patient via at least some of the electrodes; electrical stimulation circuitry configured to deliver pacing stimulation via at least some of the electrodes; an accelerometer; and processing circuitry configured to: determine an intrinsic timing interval based on the EGM and an accelerometer signal from the accelerometer, wherein the intrinsic timing interval is indicative of a passive ventricular filling interval of the patient during a first period of time; and control electrical stimulation circuitry configured to deliver pacing stimulation via at least some of the electrodes to deliver tachycardia remodeling therapy (TRT) for a second period of time by at least configuring an interval of the pacing stimulation based on the intrinsic timing interval.

[0106] Example 2. The IMD of example 1, wherein the pacing stimulation comprises atrial pacing stimulation, and wherein to configure the interval of the atrial pacing stimulation based on the intrinsic timing interval, the processing circuitry is configured to determine the interval of the atrial pacing stimulation based on the intrinsic timing interval, wherein the interval of the atrial pacing stimulation is shorter than the intrinsic timing interval.

[0107] Example 3. The IMD of any of examples 1 or 2, wherein the intrinsic timing interval comprises a timing interval between an R-wave of the EGM and an A3 event of the accelerometer signal.

[0108] Example 4. The IMD of any of examples 1-3, wherein the interval of the pacing stimulation comprises a portion of the intrinsic timing interval.

[0109] Example s. The IMD of example 4, wherein the portion of the intrinsic timing interval comprises a percentage of the intrinsic timing interval.

[0110] Example 6. The IMD of example 4, wherein the portion of the intrinsic timing interval comprises a static time reduction of the intrinsic timing interval.

[0111] Example 7. The IMD of example 4, wherein the portion of the intrinsic timing interval is based on a portion of an area under the curve (AUC) of an A3 event of the accelerometer signal.

[0112] Example 8. The IMD of any of examples 1-7, wherein the processing circuitry is configured to determine the intrinsic timing interval of the patient during one or more of atrial-only pacing or native sinus rhythm during the first period of time.

[0113] Example 9. The IMD of any of examples 1-8, wherein the processing circuitry is further configured to: determine a patient state; and control at least some electrodes of the plurality of electrodes to deliver the TRT for the second period of time by configuring the interval of the pacing stimulation based on the patient state.

[0114] Example 10. The IMD of any of examples 1-9, wherein the IMD comprises a leadless pacemaker.

[0115] Example 11. The IMD of any of examples 1-10, wherein the second period of time comprises a period of time in which the patient is resting.

[0116] Example 12. A method comprising: sensing, by at least some electrodes of a plurality of electrodes of an implantable medical device (IMD), a cardiac electrogram (EGM) of a patient; sensing, by an accelerometer, an accelerometer signal of the patient; determining, by processing circuitry of the IMD, an intrinsic timing interval based on the EGM and the accelerometer signal, wherein the intrinsic timing interval is indicative of a passive ventricular filling interval of the patient during a first period of time; and control at least some of the electrodes, by electrical stimulation circuitry configured to deliver pacing stimulation via the at least some electrodes, to deliver tachycardia remodeling therapy (TRT) for a second period of time by at least configuring an interval of the pacing stimulation based on the intrinsic timing interval.

[0117] Example 13. The method of example 12, wherein the pacing stimulation comprises atrial pacing stimulation, and wherein configuring the interval of the atrial pacing stimulation based on the intrinsic timing interval comprises: determining, by the processing circuitry, the interval of the atrial pacing stimulation based on the intrinsic timing interval, wherein the interval of the atrial pacing stimulation is shorter than the intrinsic timing interval.

[0118] Example 14. The method of any of examples 12 or 13, wherein the intrinsic timing interval comprises a timing interval between an R-wave of the EGM and an A3 event of the accelerometer signal.

[0119] Example 15. The method of any of examples 12-14, wherein the interval of the pacing stimulation comprises a portion of the intrinsic timing interval.

[0120] Example 16. The method of example 15, wherein the portion of the intrinsic timing interval comprises a percentage of the intrinsic timing interval.

[0121] Example 17. The method of example 15, wherein the portion of the intrinsic timing interval comprises a static time reduction of the intrinsic timing interval. [0122] Example 18. The method of example 15, wherein the portion of the intrinsic timing interval is based on a portion of an area under the curve (AUC) of the A3 event of the accelerometer signal.

[0123] Example 19. The method of any of examples 12-18, wherein determining the intrinsic timing interval of the patient comprises determining the intrinsic timing interval of the patient during one or more of atrial-only pacing or native sinus rhythm during the first period of time.

[0124] Example 20. The method of any of examples 12-19, further comprising: determining, by the processing circuitry, a patient state; and controlling at least some electrodes of the plurality of electrodes, by the processing circuitry, to deliver the TRT for the second period of time by configuring the interval of the pacing stimulation based on the patient state.

[0125] Example 21. The method of any of examples 12-20, wherein the IMD comprises a leadless pacemaker.

[0126] Example 22. The method of any of examples 12-21, wherein the second period of time comprises a period of time in which the patient is resting.

[0127] Example 23. A non-transitory computer-readable medium storing instructions that when executed cause processing circuitry to: determine an intrinsic timing interval based on a cardiac electrogram (EGM) sensed via at least some electrodes of a plurality of electrodes and an accelerometer signal from an accelerometer of an implantable medical device configured to deliver pacing stimulation via at least some of the electrodes, wherein the intrinsic timing interval is indicative of a passive ventricular filling interval of a patient during a first period of time; and control electrical stimulation circuitry configured to deliver pacing stimulation via at least some of the electrodes to deliver tachycardia remodeling therapy (TRT) for a second period of time by at least configuring an interval of the pacing stimulation based on the intrinsic timing interval.

[0128] Example 24. A medical device system comprising: one or more implantable medical devices (HMDs), one or more of the one or more HMDs comprising: a plurality of electrodes; sensing circuitry configured to sense a cardiac electrogram (EGM) of a patient via at least some of the electrodes; electrical stimulation circuitry configured to deliver pacing stimulation via at least some of the electrodes; an accelerometer; and processing circuitry configured to: determine an intrinsic timing interval based on the EGM and an accelerometer signal from the accelerometer, wherein the intrinsic timing interval is indicative of a passive ventricular filling interval of the patient during a first period of time; and control electrical stimulation circuitry configured to deliver pacing stimulation via at least some of the electrodes to deliver tachycardia remodeling therapy (TRT) for a second period of time by at least configuring an interval of the pacing stimulation based on the intrinsic timing interval.

[0129] Example 25. The medical device system of example 24, wherein a medical device system comprises a first IMD, and wherein processing circuitry of the medical device system is configured to: determine a patient state; configure the interval of the pacing stimulation based on the patient state; and control communication circuitry of the system to transmit information indicative of the interval of the pacing stimulation to the first IMD.

[0130] Example 26. The IMD of example 25, wherein the processing circuitry of the medical device system comprises one or more of: processing circuitry of the first IMD of the medical device system; processing circuitry of a second IMD of the medical device system; or processing circuitry of a programming device of the medical device system.

[0131] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

WHAT IS CLAIMED IS:

1. An implantable medical device (IMD) comprising: a plurality of electrodes; sensing circuitry configured to sense a cardiac electrogram (EGM) of a patient via at least some of the electrodes; electrical stimulation circuitry configured to deliver pacing stimulation via at least some of the electrodes; an accelerometer; and processing circuitry configured to: determine an intrinsic timing interval based on the EGM and an accelerometer signal from the accelerometer, wherein the intrinsic timing interval is indicative of a passive ventricular filling interval of the patient during a first period of time; and control electrical stimulation circuitry configured to deliver pacing stimulation via at least some of the electrodes to deliver tachycardia remodeling therapy (TRT) for a second period of time by at least configuring an interval of the pacing stimulation based on the intrinsic timing interval.

2. The IMD of claim 1, wherein the pacing stimulation comprises atrial pacing stimulation, and wherein to configure the interval of the atrial pacing stimulation based on the intrinsic timing interval, the processing circuitry is configured to determine the interval of the atrial pacing stimulation based on the intrinsic timing interval, wherein the interval of the atrial pacing stimulation is shorter than the intrinsic timing interval.

3. The IMD of any of claims 1 or 2, wherein the intrinsic timing interval comprises a timing interval between an R-wave of the EGM and an A3 event of the accelerometer signal.

4. The IMD of any of claims 1-3, wherein the interval of the pacing stimulation comprises a portion of the intrinsic timing interval.

5. The IMD of claim 4, wherein the portion of the intrinsic timing interval comprises a percentage of the intrinsic timing interval.

6. The IMD of claim 4, wherein the portion of the intrinsic timing interval comprises a static time reduction of the intrinsic timing interval.

7. The IMD of claim 3, wherein the portion of the intrinsic timing interval is based on a portion of an area under the curve (AUC) of an A3 event of the accelerometer signal.

8. The IMD of any of claims 1-7, wherein the processing circuitry is configured to determine the intrinsic timing interval of the patient during one or more of atrial-only pacing or native sinus rhythm during the first period of time.

9. The IMD of any of claims 1-8, wherein the processing circuitry is further configured to: determine a patient state; and control at least some electrodes of the plurality of electrodes to deliver the TRT for the second period of time by configuring the interval of the pacing stimulation based on the patient state.

10. The IMD of any of claims 1-9, wherein the IMD comprises a leadless pacemaker.

11. The IMD of any of claims 1-10, wherein the second period of time comprises a period of time in which the patient is resting.

12. A medical device system comprising: one or more implantable medical devices (HMDs), one or more of the one or more HMDs comprising: a plurality of electrodes; sensing circuitry configured to sense a cardiac electrogram (EGM) of a patient via at least some of the electrodes; electrical stimulation circuitry configured to deliver pacing stimulation via at least some of the electrodes; an accelerometer; and processing circuitry configured to: determine an intrinsic timing interval based on the EGM and an accelerometer signal from the accelerometer, wherein the intrinsic timing interval is indicative of a passive ventricular filling interval of the patient during a first period of time; and control electrical stimulation circuitry configured to deliver pacing stimulation via at least some of the electrodes to deliver tachycardia remodeling therapy (TRT) for a second period of time by at least configuring an interval of the pacing stimulation based on the intrinsic timing interval.

13. The medical device system of claim 12, wherein the one or more IMDs comprises a first IMD, and wherein processing circuitry of the medical device system is configured to: determine a patient state; configure the interval of the pacing stimulation based on the patient state; and control communication circuitry of the system to transmit information indicative of the interval of the pacing stimulation to the first IMD.

14. The IMD of claim 13, wherein the processing circuitry of the medical device system comprises one or more of: processing circuitry of the first IMD of the medical device system; processing circuitry of a second IMD of the medical device system; or processing circuitry of a programming device of the medical device system.

15. A non-transitory computer-readable medium storing instructions that when executed cause processing circuitry to: determine an intrinsic timing interval based on a cardiac electrogram (EGM) sensed via at least some electrodes of a plurality of electrodes and an accelerometer signal from an accelerometer of an implantable medical device configured to deliver pacing stimulation via at least some of the electrodes, wherein the intrinsic timing interval is indicative of a passive ventricular filling interval of a patient during a first period of time; and control electrical stimulation circuitry configured to deliver pacing stimulation via at least some of the electrodes to deliver tachycardia remodeling therapy (TRT) for a second period of time by at least configuring an interval of the pacing stimulation based on the intrinsic timing interval.