Medical devices and methods for controlling pacing intervals to promote mechanical cardiac chamber synchrony

Abstract

A medical device includes a motion sensor to generate a motion signal including a cardiac event signal. The medical device generates a ventricular pacing pulse upon expiration of a pacing interval. The medical device determines a measure of synchrony from the motion signal following delivery of the ventricular pacing pulse, and adjusts the pacing interval based on the measure of synchrony.

Description

[0001] This disclosure generally relates to implantable medical devices, and more specifically, to an intracardiac pacemaker and method for controlling the pacing interval based on intracardiac motion signals to promote mechanical synchrony of the cardiac chambers. Background Technology

[0002] The cardiac conduction system comprises the sinoatrial (SA) node, atrioventricular (AV) node, bundle of His, bundle branches, and Purkinje fibers. The heartbeat is initiated in the SA node, which acts as the heart's natural "pacemaker." Electrical impulses induced by the SA node cause the atrial myocardium to contract. The signal is conducted to the ventricles through the AV node, which inherently delays this conduction to allow the atria to stop contracting before the ventricles begin to contract, thus providing proper AV synchronicity. Electrical impulses are conducted from the AV node to the ventricular myocardium via the bundle of His, bundle branches, and Purkinje fibers.

[0003] Patients with conduction system abnormalities, such as poor AV junction conduction or SA junction dysfunction, may receive pacemakers to restore a more normal heart rhythm and atrioventricular synchrony. Dual-chamber pacemakers are available, comprising a transvenous atrial lead carrying an electrode placed in the right atrium and a transvenous ventricular lead carrying an electrode placed in the right ventricle via the right atrium. The pacemaker itself is typically implanted in a subcutaneous pouch, with the transvenous lead tunneling into the pouch. Dual-chamber pacemakers sense atrial and ventricular electrical signals and can provide atrial and ventricular pacing as needed to promote synchronization of normal heart rate and electrical depolarization of the right atrial and right ventricular chambers.

[0004] Patients with heart failure may experience ventricular asynchrony. Multi-chamber pacemakers deliver cardiac resynchronization therapy (CRT) by pacing the atria and / or one or two ventricles to improve ventricular synchrony in patients with heart failure or other abnormalities that cause poor ventricular chamber coordination. Transvenous leads can be positioned in the cardiac veins of the right atrium, right ventricle, and left ventricle to provide sensing and pacing in up to all three chambers.

[0005] Intracardiac pacemakers have been introduced or proposed for complete implantation within a patient's heart, eliminating the need for transvenous leads that could become a source of infection or other complications. Intracardiac pacemakers provide sensing and pacing within a single chamber of the patient's heart. In some patients, single-chamber pacing and sensing may be sufficient. However, single-chamber pacing and sensing may not fully address cardiac conduction disorders or abnormalities in all patients. Dual-chamber sensing and / or pacing functionality may be required to restore a more normal heart rhythm. Summary of the Invention

[0006] In general, this disclosure relates to a medical device and method for determining a synchronicity metric from a motion signal sensed by a motion sensor. The motion signal includes a cardiac event signal. The medical device may be a pacemaker that adjusts the pacing interval based on the synchronicity metric to improve the mechanical synchronicity of the heart chambers. The pacing interval may be the AV pacing interval between an atrial event and a ventricular pacing pulse, also referred to herein as the "AV interval," to promote optimal mechanical synchronicity of the heart chambers. In other instances, the pacing interval may be the ventricular interval used to improve ventricular synchronicity, also referred to herein as the "V1-V2 interval." The pacemaker may be a leadless pacemaker, and in some instances, the leadless pacemaker may be fully implanted in the right atrium, capable of sensing atrial events from cardiac electrical signals or from the motion signal and / or capable of delivering atrial pacing pulses. The pacemaker may be configured to deliver ventricular pacing pulses to ventricular tissue with the AV interval, the ventricular tissue being synchronized with the atrial event. In other instances, the pacemaker may be fully implanted in the first ventricle and may be configured to deliver pacing pulses to an opposing second ventricle with an interventricular pacing interval synchronized with the first ventricle. The pacemaker operating according to the techniques disclosed herein senses motion signals comprising atrial and ventricular mechanical event signals, determines a synchronicity metric from the motion signals, and adjusts the AV pacing interval and / or the interventricular pacing interval based on the synchronicity metric to promote optimized chamber synchronicity. For example, the adjusted pacing interval can be used to deliver atrial-synchronized ventricular pacing or CRT via the medical device.

[0007] In one example, this disclosure provides a medical device including a motion sensor configured to generate motion signals comprising an atrial contraction event signal, a first ventricular contraction event signal corresponding to the start of ventricular contraction, and a second ventricular contraction event signal corresponding to the end of ventricular contraction. The medical device includes a therapy delivery circuit configured to generate ventricular pacing pulses. Each ventricular pacing pulse is generated upon expiration of the pacing interval. The medical device includes control circuitry configured to determine a synchronicity measure from the motion signals based on at least one of the first ventricular contraction event signal and / or the second ventricular contraction event signal following at least one generated ventricular pacing pulse. The control circuitry can adjust the pacing interval based on the synchronicity measure.

[0008] In another example, this disclosure provides a method for generating a motion signal, the motion signal comprising an atrial contraction event signal, a first ventricular contraction event signal corresponding to the start of ventricular contraction, and a second ventricular contraction event signal corresponding to the end of ventricular contraction. The method comprises: generating a ventricular pacing pulse upon the expiration of a pacing interval; determining a synchronicity measure from the motion signal based on at least one of the first ventricular contraction event signal and / or the second ventricular contraction event signal following at least one ventricular pacing pulse; and adjusting the pacing interval based on the synchronicity measure.

[0009] In another example, this disclosure provides a non-transitory computer-readable storage medium storing a set of instructions that, when executed by a medical device, cause the medical device to generate motion signals, the motion signals including an atrial contraction event signal, a first ventricular contraction event signal corresponding to the start of ventricular contraction, and a second ventricular contraction event signal corresponding to the end of ventricular contraction. The instructions cause the medical device to generate a ventricular pacing pulse when the pacing interval expires. The instructions further cause the medical device to determine a synchronicity measure from the motion signals based on at least one of the first ventricular contraction event signal and / or the second ventricular contraction event signal following at least one generated ventricular pacing pulse, and to adjust the pacing interval based on the synchronicity measure.

[0010] This summary is intended to provide an overview of the subject matter described herein. It is not intended to provide an exclusive or exhaustive explanation of the devices and methods described in detail in the following drawings and description. Further details of one or more examples are set forth in the following drawings and description. Attached Figure Description

[0011] Figure 1 This is a conceptual diagram of a pacemaker implanted in the right atrium of a patient's heart.

[0012] Figure 2 yes Figure 1 An enlarged conceptual diagram of an intracardiac pacemaker.

[0013] Figure 3 This is a conceptual diagram of an intracardiac pacemaker implanted in the right ventricle of a patient's heart.

[0014] Figure 4 This is a block diagram of a circuit system that can be encapsulated within a pacemaker housing to provide cardiac pacing and sensing functions, accompanied by pacing interval control based on a synchronicity metric derived from motion signals.

[0015] Figure 5 It can be made by Figure 1 A diagram of the heart signals generated by a pacemaker, including electrical and mechanical events in the atria and ventricles.

[0016] Figure 6 yes Figure 5 A diagram of cardiac signals, depicting various instances of synchronicity measures for controlling AV intervals that can be determined by a pacemaker.

[0017] Figure 7 This is a flowchart of a method for controlling the AV interval via an intracardiac pacemaker during ventricular pacing synchronized with atrial pacing, based on an example.

[0018] Figure 8 This is a flowchart of a method for controlling AV intervals based on another example.

[0019] Figure 9 This is a flowchart of a method for controlling the interventricular pacing interval during biventricular pacing, based on an example.

[0020] Figure 10 This is a flowchart of a method for performing pacing interval optimization on a trigger-based basis, based on some examples. Detailed Implementation

[0021] This document discloses a cardiac pacemaker and pacing technology for controlling the pacing interval based on motion sensor signals to optimize the mechanical synchronicity of the heart chambers. In some instances, the cardiac pacemaker may be a leadless pacemaker fully implanted within the heart chambers and configured to sense cardiac events in at least two different heart chambers and deliver pacing pulses to one or both different heart chambers. For example, the pacemaker may be configured to deliver bi-chamber atrial and ventricular pacing, atrial-synchronized single-chamber ventricular pacing, or atrial-synchronized bi-ventricular pacing. The pacemaker determines a synchronicity metric from motion signals generated by motion sensors included in the pacemaker. The pacemaker adjusts the pacing interval based on the synchronicity metric, for example, the AV pacing interval and / or the interventricular pacing interval (e.g., right ventricle to left ventricle pacing interval or left ventricle to right ventricle pacing interval). The AV and / or interventricular pacing interval is adjusted to promote mechanical synchrony of the cardiac chambers when a ventricular pacing pulse is delivered with the adjusted AV pacing interval after a sensed or paced atrial event and / or when a ventricular pacing pulse is delivered with the adjusted interventricular pacing interval in the relative ventricular chamber after a ventricular pacing pulse or a sensed R wave.

[0022] Figure 1This is a conceptual diagram of a dual-chamber intracardiac pacemaker 10 implanted in a patient's heart 8. The pacemaker 10 is shown implanted in a target implantation region 4 in the right atrium (RA) of the patient's heart 8. The pacemaker 10 may include a fixation member 20 anchoring the distal end of the pacemaker 10 against the atrial endocardium in the target implantation region 4. The target implantation region 4 may be located between the His bundle 5 and the coronary sinus 6, and may be adjacent to the tricuspid valve 3. In some instances, the target implantation region 4 may correspond to or be located within the Koch triangle. The pacemaker 10 may be a leadless pacemaker including a distal ventricular electrode 42 extending distally from the pacemaker 10. When implanted in the target region 4, the distal ventricular electrode 42 may extend through the atrial myocardium and central fibrous body and into the ventricular myocardium 14 or along the interventricular septum without completely penetrating the ventricular endocardium or epicardial surface. The distal ventricular electrode 42 may be carried at the distal end of an axis extending from the distal end of the pacemaker for positioning the electrode 42 within the ventricular tissue to sense ventricular signals (e.g., R waves accompanying ventricular myocardial depolarization) and deliver ventricular pacing pulses. In some instances, the distal ventricular electrode 42 is provided as a cathode electrode in conjunction with a housing-based anode electrode 24 for use in a bipolar pacing and sensing electrode pair, the housing-based anode electrode being positioned proximally along the pacemaker housing. (See the following in conjunction...) Figure 2 As described, pacemaker 10 can be a leadless dual-chamber pacemaker comprising a distal housing-based electrode that can act as an atrial cathode pacing and sensing electrode, paired with a housing-based proximal anode electrode 24. In this way, pacemaker 10 is capable of DDD pacing and sensing or CRT delivery.

[0023] Although Figure 1 The illustration shows a specific implantation region 4 within the ventricular myocardium that enables electrode positioning; however, it should be understood that pacemakers configured to perform atrial-synchronized ventricular pacing according to the techniques disclosed herein can be implanted at other locations for dual-chamber pacing and sensing or for single-chamber ventricular pacing with dual-chamber sensing, for example, as combined below. Figure 3 As described.

[0024] The pacemaker 10 includes a motion sensor that generates motion signals, such as an accelerometer that generates acceleration signals, which are correlated with motion applied directly to the pacemaker 10 by the movement of the heart 8 and blood when the pacemaker 10 is fully implanted within the heart chambers. In other instances, the pacemaker 10 may be implanted on the epicardium of the heart 8, and the motion sensor generates motion signals attributable to the movement of the heart, thereby applying motion directly to the pacemaker 10. A synchronicity metric can be determined from the motion signals corresponding to ventricular contraction as an indicator of synchronization between the left and right ventricular chambers and / or between the atrial and ventricular chambers. Based on the synchronicity metric, the AV pacing interval can be adjusted to alter the time delay from an atrially paced or sensed event to the ventricular pacing pulse in a manner that promotes optimized AV synchronization and / or ventricular synchronicity.

[0025] Figure 2 This is an enlarged conceptual diagram of the anatomy of the intracardiac pacemaker 10 and the patient's heart 8. The intracardiac pacemaker 10 includes a housing 30 that defines the internal components of the pacemaker 10 (as described below). Figure 4 The housing 30 is generally described as residing in a hermetically sealed internal cavity housing the sensing circuitry, therapy delivery circuitry, control circuitry, memory, telemetry circuitry, motion sensor, and power supply. The housing 30 may be formed of a conductive material comprising titanium or titanium alloys, stainless steel, MP35N (a non-magnetic nickel-cobalt-chromium-molybdenum alloy), platinum alloys, or other biocompatible metals or metal alloys. In other examples, the housing 30 may be formed of a non-conductive material comprising ceramics, glass, sapphire, silicone, polyurethane, epoxy resin, acetyl copolymer plastics, polyetheretherketone (PEEK), liquid crystal polymers, or other biocompatible polymers.

[0026] The housing 30 includes longitudinal sidewalls 38 extending from the distal end 32 of the pacemaker housing to the proximal end 34 of the pacemaker housing and may be generally cylindrical, having a longitudinal axis 39 to aid in catheter delivery to the target region 4. However, in other instances, the housing 30 may be prismatic or other shapes and is not limited to the generally cylindrical examples shown herein. The housing 30 may include, for example, a delivery tool interface member 26 located at the proximal end 34 for engagement with a delivery tool during implantation of the pacemaker 10.

[0027] A portion of the housing 30 can act as an anode electrode during pacing and / or sensing. In the illustrated example, the housing-based electrode 24 is shown as a proximal portion of the external longitudinal sidewall 38. When the housing 30 is formed of a conductive material such as titanium alloy or other examples listed above, portions of the housing 30 can be electrically insulated by a non-conductive material such as a coating of parylene, polyurethane, silicone, epoxy resin, or other biocompatible polymers, thereby exposing one or more discrete regions of the conductive material to define an electrode, such as the proximal housing-based electrode 24. When the housing 30 is formed of a non-conductive material such as ceramic, glass, or polymeric materials, a conductive coating or layer such as titanium, platinum, stainless steel, or alloys thereof can be applied to one or more discrete regions of the housing 30 to form a housing-based electrode, such as the proximal housing-based electrode 24. In other examples, the proximal housing-based electrode 24 can be a component mounted or assembled onto the housing 30, such as a ring electrode. The proximal housing-based electrode 24 can be electrically coupled to the internal circuitry of the pacemaker 10, for example, via a conductive housing 30 or, when the housing 30 is made of a non-conductive material. In the illustrated example, the proximal housing-based electrode 24 is positioned closer to the proximal end 34 of the housing than to the distal end 32, and is therefore referred to as the "proximal housing-based electrode" 24. However, in other examples, the housing-based electrode 24 may be positioned at other locations along the housing 30, for example, relatively farther than the illustrated location or the location along the proximal end 34.

[0028] At the distal end 32, the pacemaker housing 30 may include a distal fixation and electrode assembly 36, which includes a fixation member 20 and a distal ventricular electrode 42 carried by an axis 40 extending distally away from the distal end 32 of the housing. The distal ventricular electrode 42 may be located at or near the free distal end of the axis 40. The distal ventricular electrode 42 may have a conical or hemispherical distal tip with a relatively narrow tip diameter, for example less than 1 mm, for penetration into and through tissue layers, without requiring a sharp tip or a needle-like tip with a sharp or beveled edge that could otherwise produce a cutting action that could result in lateral displacement of the distal ventricular electrode 42 and undesirable tissue trauma.

[0029] In some instances, shaft 40 can be a normal, straight, rigid component capable of being advanced through tissue to position the distal ventricular electrode 42 for pacing ventricular tissue. In other instances, shaft 40 is relatively stiff with limited flexibility in the lateral direction. Shaft 40 can be non-rigid to allow some lateral deflection with cardiac motion. However, in a relaxed state, when not subjected to any external force, shaft 40 maintains a straight position as shown to keep the distal ventricular electrode 42 spaced apart from the distal end 32 of the housing. The distal ventricle 42 and shaft 40 are configured to pierce one or more tissue layers to position the distal ventricular electrode 42 within the desired tissue layer (e.g., ventricular myocardium). Therefore, shaft 40 may have a height 47 corresponding to the intended depth of the ventricular pacing site and may have relatively high compressive strength along its longitudinal axis to resist bending in the lateral or radial direction when a longitudinal force is applied to the distal ventricular electrode 42 during pressure against the implantation site, for example, by applying a longitudinal thrust to the proximal end 34 of housing 30 to advance the electrode 42 into the tissue within the target implantation area 4. Shaft 40 may be longitudinally non-compressible. Shaft 40 may be elastically deformable in the lateral or radial direction when subjected to lateral or radial forces to allow temporary deflection, for example, with tissue movement, but the shaft returns to its normal straight position when the lateral force decreases.

[0030] The fixation member 20 may include one or more cusps having a normal curved position. During implantation of the pacemaker 10, the cusps of the fixation member 20 may be held in a distally extended position within the delivery tool. The distal tips of the cusps of the fixation member penetrate cardiac tissue to a limited depth, and then, upon release from the delivery tool, elastically bend proximally back to a normal curved position (as shown). An aspect of the fixation member 20 may correspond to the fixation member substantially disclosed in U.S. Patent No. 9,675,798 (Grubac et al.) or U.S. Patent No. 9,119,959 (Rys et al.).

[0031] In some instances, to provide dual-chamber pacing and sensing, the distal fixation and electrode assembly 36 includes a distal housing-based electrode 22, which can act as a cathode electrode paired with a proximal housing-based electrode 24. When using the pacemaker 10 for dual-chamber pacing and sensing or for CRT applications, the distal ventricular electrode 42 can be used as a cathode electrode paired with the proximal housing-based electrode 24, which acts as a return anode electrode. Alternatively, the distal housing-based electrode 22 can act as a return anode electrode paired with the distal ventricular electrode 42 for sensing ventricular signals and delivering ventricular pacing pulses. In other instances, the distal housing-based electrode 22 can be a cathode electrode for sensing atrial signals and delivering pacing pulses to the atrial myocardium in the target implantation region 4. When the distal housing-based electrode 22 acts as the atrial cathode electrode, the proximal housing-based electrode 24 can act as a return anode paired with the distal ventricular electrode 42 for ventricular pacing and sensing, and also as a return anode paired with the distal housing-based electrode 22 for atrial pacing and sensing. The distal housing-based electrode 22 is shown located at the distal end 32 of the pacemaker housing 30 and coupled to a lead included in the distal fixation and electrode assembly 36 for electrically coupling the electrode 22 to the pacing and sensing circuitry within the housing 30. In other embodiments, the distal housing-based electrode 22 may be positioned along the circumferential surface of the longitudinal sidewall 38.

[0032] As used herein, the term "housing-based" for electrodes refers to electrodes that are directly carried on or coupled to the surface of the housing 30 without the use of flexible, elongated medical leads. This surface includes the outer surface surrounding the longitudinal sidewalls 38 of the pacemaker 10 and the exterior of the distal end 32 and proximal end 34. In contrast, "lead-based" electrodes are carried by a flexible lead body surrounding an electrical conductor (e.g., wire or cable) that electrically couples the electrode to a proximal connector pin received by the connector assembly. This proximal connector pin is sometimes referred to as a "connector" for electrical connection to the internal pacemaker circuitry. Housing-based electrodes are not carried by elongated, flexible lead bodies. Each of electrodes 22, 24, and 42 is a "housing-based electrode" because the pacemaker 10 is a leadless pacemaker, where each electrode is located directly on or coupled to the pacemaker housing without the use of elongated, flexible lead bodies carrying wire conductors manually connected to the pacemaker connector assembly.

[0033] In other instances, pacemaker 10 may be provided with four electrodes, an atrial sensing and pacing pair, and a ventricular sensing and pacing pair. As an example, one or more ring, button, or ball electrodes may be carried on distal end 32 to act as atrial cathode electrodes paired with a relatively closer anode electrode. Various examples of electrode configurations that can be used to deliver atrial-synchronized ventricular pacing from an intracardiac implantation site employing the techniques disclosed herein are generally disclosed in Pre-Purpose U.S. Patent Publication No. 2019 / 0083779 (Yang et al.) and Pre-Purpose U.S. Patent Publication No. 2019 / 0083800 (Yang et al.). In other instances, the target pacing site may include a His bundle. Example intracardiac pacemakers configured for pacing the ventricle from the atrial cavity implantation site of said pacemaker via the His bundle are generally disclosed in Pre-Purpose U.S. Patent Publication No. 2019 / 0134404 (Sheldon et al.).

[0034] like Figure 2 As shown, in some pacing applications, the target implantation region 4 is along the atrial endocardium 18, typically below the AV node 15 and His bundle 5. The shaft 40 and electrode 42 may be provided with a height 47 that penetrates the atrial endocardium 18 in the target implantation region 4, passes through the central fibrous body 16, and enters the ventricular myocardium 14 without penetrating the ventricular endocardial surface 17. When the entire height 47 of the shaft 40 is fully advanced into the target implantation region 4, the distal ventricular electrode 42 rests within the ventricular myocardium 14, and the distal housing-based electrode 22 is positioned in close contact or very close proximity to the atrial endocardium 18. In various examples, the total height 47 of the shaft 40 may be approximately 3 mm to 8 mm. The diameter of the shaft 40 may be less than 2 mm and may be 1 mm or less, or even 0.6 mm or less. In some examples, the shaft 40 and electrode 42 may be provided with tissue fixation features such as hooks, spirals, barbs, or other features that tend to prevent the electrode 42 from retracting from the pacing site. For example, instead of the linear axis 40 shown, the distal ventricular electrode 42 may be an exposed conductive tip of an insulated helical shaft that advances from the atrial endocardium through cardiac tissue into the ventricular myocardial tissue and / or approaches the His bundle to pace the ventricle.

[0035] Figure 3 This is a conceptual diagram of a pacemaker 10 implanted in an alternative location to deliver atrial-synchronized ventricular pacing, based on another example. In some cases, the pacemaker 10 may be implanted within the ventricular cavity and may be provided with a distal ventricular electrode 42 positioned distal to the pacemaker 10 and extending along an axis penetrating the interventricular septum 7. Figure 3In the example shown, pacemaker 10 is implanted in the right ventricle (RV), with fixation member 20 anchored in the superior septal wall. A distal ventricular electrode 42 on shaft 40 is advanced through septal wall 7 without piercing the endocardial or epicardial surface of the left ventricle to position the distal ventricular electrode 42 at a target ventricular pacing site in the left ventricle. The target ventricular pacing site can be in the ventricular myocardium or along the ventricular conduction system, e.g., along the bundle branch. In some cases, the distal ventricular electrode 42 can be advanced into septal wall 7 to place the distal ventricular electrode 42 at the target pacing site to pace the left ventricle (LV) from a shell implantation location within the RV, e.g., along the left bundle branch. The distal shell-based electrode 22 can act as a cathode electrode operatively accessible to the right ventricular myocardium to pace the RV. By using the distal ventricular electrode 42 as a cathode electrode paired with the shell-based proximal anode electrode 24 (see [link to documentation]), the pacing can be achieved. Figure 2 ) to pace LV and use a distal housing-based electrode 22 paired with a housing-based proximal anode electrode 24 (see Figure 2 When the pacemaker 10 is used for biventricular pacing, a synchrony metric can be determined from the motion sensor signal to optimize the interventricular pacing interval between the RV and LV pacing pulses and / or to optimize the AV pacing interval between the atrial contraction mechanical event detected from the intraventricular motion signal and the ventricular pacing pulse.

[0036] As described herein, pacemaker 10 includes a motion sensor that generates cardiac mechanical signals, including atrial contraction event signals and ventricular mechanical event signals. When placed in the RV, pacemaker 10 may or may not be able to sense the atrial P wave (accompanied by atrial depolarization) from the cardiac electrical signals sensed by pacemaker 10 within the RV, because the P wave is a relatively low-amplitude signal compared to the ventricular R wave. Therefore, pacemaker 10 can sense atrial contraction events by sensing the atrial contraction mechanical event signals from the motion signals to initiate AV intervals for delivering atrially synchronized ventricular pacing. AV interval pacing can be used for either the RV or LV. As disclosed herein, pacemaker 10 can determine a synchronicity metric from the cardiac mechanical signals to optimize the AV interval based on the synchronicity metric, which may be correlated with ventricular mechanical synchronicity. In some patients, ventricular mechanical synchronicity may be impaired, for example due to cardiomyopathy, heart failure, or conduction abnormalities. By controlling the AV interval used to deliver LV pacing pulses synchronized with atrial events, the timing of RV contractions and LV contractions can be resynchronized, or at least ventricular asynchrony can be reduced.

[0037] Figure 4This is a block diagram of a circuit system that can be encapsulated within a housing 30 of a pacemaker 10 to provide cardiac pacing functionality, accompanied by pacing interval control based on a synchronicity metric determined from intracardiac motion signals. The pacemaker 10 can be configured for, for example, in… Figure 1 Dual-chamber pacing and sensing are performed at the implantation site shown, or for example at... Figure 1 or Figure 3 Single-chamber ventricular pacing with dual-chamber sensing can be performed at any of the implantation sites, or for example, as... Figure 3 The illustration shows biventricular pacing with dual-chamber sensing. An electronic circuitry system encapsulated within a housing 30 includes software, firmware, and hardware that collaboratively monitor cardiac signals in the atria and ventricles, determine when pacing therapy is needed, and deliver pacing electrical pulses to the patient's heart as needed, based on programmed pacing modes and pacing pulse control parameters. As disclosed herein, the circuitry further includes motion sensing capabilities used in the pacing control feedback loop for adjusting the AV interval and / or the interventricular interval between right ventricular electrical events and left ventricular electrical events, scheduled between atrial and ventricular pacing pulses, to promote optimal mechanical synchronicity between chamber contractions. Synchronicity between the atria and ventricles, and between the RV and LV, as well as coordinated contraction of each ventricular chamber region, can be improved by adjusting the AV interval and / or interventricular interval based on one or more synchronicity measures disclosed herein. The electronic circuit system includes a control circuit 80, a memory 82, a therapy delivery circuit 84, a sensing circuit 86, a telemetry circuit 88, and a motion sensor 90, for generating signals that include signals of cardiac mechanical events related to cardiac motion.

[0038] Power source 98 provides power as needed to the circuitry of pacemaker 10, which includes components 80, 82, 84, 86, 88, and 90. Power source 98 may include one or more energy storage devices, such as one or more rechargeable or non-rechargeable batteries. Figure 4 The overall block diagram provides an understanding of the connections between power supply 98 and each of the other components 80, 82, 84, 86, 88, and 90, but these connections are not shown for clarity. For example, power supply 98 is coupled to one or more charging circuits included in therapy delivery circuitry 84 to provide the power required to charge a holding capacitor included in therapy delivery circuitry 84, which is discharged at appropriate times under the control of control circuitry 80 to deliver pacing pulses, for example, according to a dual-chamber pacing mode. Power supply 98 is also coupled to components of sensing circuitry 86, such as sensing amplifiers, analog-to-digital converters, switching circuitry systems, motion sensor 90, telemetry circuitry 88, and memory 82, to provide power to various circuits as needed.

[0039] Figure 4The functional blocks shown represent the functions included in pacemaker 10 and may include any discrete and / or integrated electronic circuitry components implementing analog and / or digital circuitry capable of producing the functions possessed by pacemaker 10 herein. Individual components may include application-specific integrated circuits (ASICs), electronic circuitry, processors (shared, dedicated, or grouped) and memories, combinational logic circuitry, state machines, or other suitable components or combinations thereof providing the described functions, executing one or more software or firmware programs. The specific form of the software, hardware, and / or firmware used to implement the functions disclosed herein will be determined primarily by the specific system architecture employed in the pacemaker and the specific detection and therapy delivery methods employed by the pacemaker. Given the disclosure herein, providing software, hardware, and / or firmware to implement the described functions in the context of any modern cardiac medical device is within the capabilities of those skilled in the art.

[0040] Memory 82 may comprise any volatile, non-volatile, magnetic, or electrically non-transitory computer-readable storage medium, such as random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, or any other memory device. Furthermore, memory 82 may comprise a non-transitory computer-readable medium storing instructions that, when executed by one or more processing circuits, cause control circuitry 80 and / or other circuitry to perform the atrial-synchronized ventricular pacing function or other dual-chamber sensing and pacing therapy delivery functions possessed by pacemaker 10 herein. The non-transitory computer-readable medium storing instructions may comprise any of the media listed above.

[0041] Control circuitry 80 communicates, for example, via a data bus with therapy delivery circuitry 84 and sensing circuitry 86 to sense cardiac electrical signals and control the delivery of cardiac electrical stimulation therapy in response to sensed cardiac events (e.g., P and R waves, or their absence). Distal ventricular electrode 42, distal housing-based electrode 22, and proximal housing-based electrode 24 are electrically coupled to therapy delivery circuitry 84 to deliver electrical stimulation pulses to the patient's heart and are electrically coupled to sensing circuitry 86 to sense cardiac electrical signals.

[0042] The sensing circuit 86 receives cardiac electrical signals via electrodes 22, 24, and / or 42 and may include multiple sensing channels, such as an atrial (A) sensing channel 87 and a ventricular (V) sensing channel 89. The distal housing-based electrode 22 and the proximal housing-based electrode 24 may be coupled to the atrial sensing channel 87 to sense atrial electrical event signals, such as P waves associated with atrial myocardial depolarization. The distal ventricular electrode 42 and the proximal housing-based electrode 24 (or the distal housing-based electrode 22) may be coupled as ventricular sensing electrode pairs to the ventricular sensing channel 89 to sense ventricular electrical event signals, such as R waves associated with ventricular myocardial depolarization. In examples including additional electrodes carried by the pacemaker housing 30 and / or shaft 40, the sensing circuit 86 may include a switching circuit system for selectively coupling the atrial sensing electrode pairs to the atrial sensing channel 87 and the ventricular sensing electrode pairs to the ventricular sensing channel 89. The switching circuit system may include a switch array, a switch matrix, a multiplexer, or any other type of switching device suitable for selectively coupling components of the sensing circuit 86 to selected electrodes.

[0043] Each of the atrial sensing channel 87 and the ventricular sensing channel 89 may include a cardiac electrical event detection circuitry system for detecting P waves and R waves, respectively, from cardiac electrical signals received by the respective sensing channel. The cardiac electrical event detection circuitry system included in each atrial channel 87 and ventricular channel 89 may be configured to amplify, filter, digitize, and rectify the cardiac electrical signals received from selected electrodes to improve signal quality for detecting cardiac electrical events. The cardiac event detection circuitry system within each channel 87 and 89 may include one or more sensing amplifiers, filters, rectifiers, threshold detectors, comparators, analog-to-digital converters (ADCs), timers, or other analog or digital components. The cardiac event sensing thresholds, such as P wave sensing thresholds and R wave sensing thresholds, may be automatically adjusted by each respective sensing channel 87 and 89 under the control of the control circuitry 80, for example, based on a timing period and sensing thresholds stored in memory 82 and / or controlled by the hardware, firmware, and / or software of the control circuitry 80 and / or the sensing circuitry 86, determined by the control circuitry 80. The sensing circuit 86 can apply various blanking periods and refractory periods to the received cardiac electrical signals to control the sensing of atrial and ventricular events in a manner that avoids false or over-sensing of atrial and ventricular electrical events.

[0044] Each channel 87 and 89 can be configured to generate a sensed event signal transmitted to control circuit 80 in response to a received cardiac electrical signal exceeding a corresponding atrial P-wave sensing threshold or ventricular R-wave sensing threshold. For example, atrial sensing channel 87 can generate a P-wave sensed event signal in response to a P-wave sensing threshold crossing. Ventricular sensing channel 89 can generate an R-wave sensed event signal in response to an R-wave sensing threshold crossing. Control circuit 80 uses the sensed event signals to set a pacing escape interval timer that controls the basic time interval used to schedule cardiac pacing pulses. Depending on the specific programmed pacing mode, the sensed event signals can trigger or suppress pacing pulses. For example, a P-wave sensed event signal received from atrial sensing channel 87 can cause control circuit 80 to suppress scheduled atrial pacing pulses (when pacemaker 10 is implanted in RA) and schedule ventricular pacing pulses with a programmed AV pacing interval. As described herein, the AV pacing interval between the sensed atrial P wave and the ventricular pacing pulse can be adjusted based on the analysis of signals from the motion sensor 90. If an R wave is sensed before the AV pacing interval expires, the ventricular pacing pulse is suppressed. If the AV pacing interval expires before the control circuit 80 receives an event signal indicating R wave sensing from the ventricular sensing channel 89, the control circuit 80 controls the therapy delivery circuit 84 to deliver a scheduled ventricular pacing pulse synchronized with the sensed P wave.

[0045] For example, such as Figure 1 As shown, when positioned in an RA for dual-chamber pacing and sensing, control circuit 80 can set a lower pacing rate interval for controlling the delivery of atrial pacing pulses, for example, by setting an AA pacing interval. When control circuit 80 does not receive a P-wave sensed event signal from atrial sensing channel 87 before the AA pacing interval expires, control circuit 80 controls therapy delivery circuit 84 to deliver atrial pacing pulses and initiate AV pacing interval. Control circuit 80 can set VV pacing interval to control ventricular pacing at a minimum lower rate in the absence of a sensed atrial event triggering a ventricular pacing pulse.

[0046] When configured for dual-chamber pacing, the therapy delivery circuit 84 may include an atrial pacing circuit 83 and a ventricular pacing circuit 85. Each pacing circuit 83 and 85 includes a charging circuit system, one or more charge storage devices such as one or more low-voltage holding capacitors, an output capacitor, and a switching circuit system that controls when the one or more holding capacitors are charged and discharged across the output capacitor to deliver pacing pulses to the pacing electrode vector coupled to the respective pacing circuit 83 or 85. The distal ventricular electrode 42 and the proximal housing-based electrode 24 may be coupled as a bipolar cathode and anode pair to the ventricular pacing circuit 85 to deliver ventricular pacing pulses, for example, upon the expiration of the AV or VV pacing interval set by the control circuit 80 for providing atrial synchronizing ventricular pacing and a basic lower ventricular pacing rate.

[0047] Atrial pacing circuit 83 can be coupled to distal housing-based electrode 22 and proximal housing-based electrode 24 to deliver atrial pacing pulses. Control circuit 80 can set the atrial pacing interval according to a programmed lower pacing rate or a temporarily lower rate set according to a pacing rate indicated by a rate-responsive sensor. In some instances, atrial pacing circuit 83 is optional. For example, some patients may have normal SA junction and atrial electrical function but exhibit AV block or other ventricular conduction abnormalities or asynchrony, which provides an indication for ventricular pacing but does not require atrial pacing. Therefore, pacemaker 10 can be configured for single-chamber ventricular pacing and dual-chamber sensing of atrial and ventricular events. When atrial pacing circuit 83 is included, an atrial pacing pulse can be delivered when no P-wave sensed event signal is received from atrial sensing channel 87 before the AA pacing interval expires. Control circuit 80 initiates the AV pacing interval in response to the delivered atrial pacing pulse to provide synchronized ventricular pacing. As described in this article, the AV pacing interval between atrial pacing pulses and ventricular pacing pulses can be adjusted based on the analysis of signals from motion sensor 90.

[0048] In some instances, the pacemaker 10 can be configured, for example, in Figure 3Biventricular pacing can be delivered at the implantation site, in which case an atrial pacing channel 83 is not required. However, a right ventricular pacing channel and a left ventricular pacing channel can be provided. For example, the distal ventricular electrode 42 and the proximal shell electrode 24 can be coupled to the ventricular channel 85 to deliver left ventricular pacing pulses. Instead of the “atrial” pacing channel 83, the second pacing channel 83 can be a right ventricular pacing channel coupled to the distal shell-based electrode 22 and the proximal shell-based electrode 24 to deliver right ventricular pacing pulses. In this way, biventricular pacing can be delivered to provide CRT, thereby improving or restoring ventricular synchrony. Right ventricular pacing pulses and left ventricular pacing pulses can be delivered with an interventricular (V1-V2) pacing interval, which controls the relative timing of the electrical activation of the right and left ventricles. The ventricular interval can be adjusted based on a synchronicity measure determined from the intraventricular motion signal received from the motion sensor 90 by the control circuit 80.

[0049] It should be understood that the interventricular pacing interval can be a pacing interval used to control the time interval between the R wave sensed by the right ventricle and the pacing pulse of the left ventricle, the R wave sensed by the left ventricle and the pacing pulse of the right ventricle, or the time interval between the pacing pulse of the right ventricle and the pacing pulse of the left ventricle. Each of these interventricular pacing intervals can be individually set to different programmable settings and can be adjusted by the control circuit 80 based on a synchronicity measure determined from the intraventricular motion signal. Depending on the individual patient's needs, a right ventricular electrical event can cause a left ventricular electrical event, and vice versa. In the case of biventricular sensing and pacing, the ventricular sensing channel 89 can include two ventricular sensing channels, one for sensing, for example, the right ventricular R wave from electrodes 22 and 24, and one for sensing, for example, the left ventricular R wave from electrodes 42 and 24.

[0050] The therapy delivery circuit 84 delivers pacing pulses by charging the holding capacitors of the corresponding atrial pacing circuit 83 and ventricular pacing circuit 85 to corresponding programmed pacing voltage amplitudes, and discharges the holding capacitors for corresponding pacing pulse widths according to control signals received from the timing circuit 94 of the control circuit 80. For example, the timing circuit 94 may include a programmable digital counter set by the processor 92 of the control circuit 80 for controlling the basic pacing intervals associated with various pacing modes. The control circuit 80 may also set the amplitude, pulse width, polarity, or other characteristics of the cardiac pacing pulses generated by the therapy delivery circuit 84, based on programmed values ​​stored in the memory 82.

[0051] The pacemaker 10 includes a motion sensor 90 that generates a signal incorporating cardiac mechanical events, which can be analyzed to control ventricular pacing delivered by the therapy delivery circuitry 84. In some instances, the motion sensor 90 may be implemented as an accelerometer encapsulated within a housing 30. However, in other instances, the motion sensor may be another type of mechanical sensor, such as a pressure sensor, configured to generate an electrical signal associated with mechanical motion exerted directly on the pacemaker housing 30 by the heart and blood when the pacemaker 10 is implanted within or on a heart chamber. The motion sensor 90 provides a signal to a control circuitry 80 (e.g., to a processor 92) for analyzing detected cardiac mechanical events and determining a synchronicity metric based on one or more aspects of one or more detected cardiac mechanical events. Based on the synchronicity metric, the control circuitry 80 may set or adjust the pacing interval, for example, the AV interval for controlling the timing of ventricular pacing pulses relative to atrial events, the ventricular interventricular interval for controlling the timing between right ventricular electrical events and left ventricular electrical events, or both. The atrial event that initiates the AV interval can be an electrical event, such as a sensed P wave or a delivered atrial pacing pulse, or a mechanical event sensed as an atrial contraction event from a motion signal generated by motion sensor 90. For example, in Figure 3 In one example, the control circuit 80 may be configured to sense a mechanical atrial contraction event from a motion signal received from the self-motion sensor 90 and to initiate an AV interval in response to sensing the mechanical atrial contraction event.

[0052] The accelerometer of motion sensor 90 can be a one-dimensional, two-dimensional, or three-dimensional accelerometer. For example, the accelerometer may comprise three single-axis accelerometer elements orthogonally positioned to form three axes. Each axis of the single-dimensional or multi-dimensional accelerometer included in motion sensor 90 may be defined by a piezoelectric element, microelectromechanical system (MEMS) device, or other sensor element capable of generating an electrical signal in response to changes in acceleration applied to pacemaker 10 and subsequently applied to the sensor element (e.g., by converting the acceleration into a force or displacement of the motion sensor element, which is then converted into an electrical signal by the motion sensor element).

[0053] Each motion sensor element generates an acceleration signal corresponding to a vector aligned with the axis of the sensor element. Each motion sensor element generates a DC component corresponding to the gravity vector component along the respective motion sensor axis. Each motion sensor element generates an AC component along the respective axis related to acceleration attributable to patient movement. The AC acceleration signal generated by each axis of the motion sensor may include acceleration directly applied to the pacemaker housing 30, causing acceleration of the pacemaker housing 30 attributable to blood movement within the RA (when implanted in the RA) or RV (when implanted in the RV), and acceleration attributable to cardiac chamber movement (e.g., atrial systole and diastole, and ventricular systole and diastole). The acceleration signal may further include a signal attributable to acceleration of the pacemaker housing 30 caused by patient body movement, for example, attributable to patient body activity during daily activities, exercise, etc.

[0054] In some instances, the accelerometer may have an axis 39 aligned with the longitudinal axis 39 of the pacemaker 10 (see [link]). Figure 2 A parallel or aligned "longitudinal" axis and two orthogonal axes extending radially relative to the longitudinal axis 39, for example, radially outward toward the longitudinal sidewall 38. While one or more axes may provide a greater signal intensity for the cardiac mechanical event of interest, the optimal axis (or axes) for sensing the cardiac mechanical event signal can vary between motion sensor orientation, post-implantation pacemaker orientation, and other factors. Therefore, the practice of the techniques disclosed herein is not limited to a specific orientation of the motion sensor within or along the housing 30 or relative to the heart 8. Generally, the motion sensor 90 generates intracardiac motion signals from at least one motion sensor signal axis, and the control circuitry 80 is configured to detect and analyze cardiac mechanical event signals from said at least one motion sensor signal axis for controlling the pacing interval used by the therapy delivery circuitry 84 during ventricular pacing. Figure 1 In this example, the intracardiac motion signal is an intracardiac motion signal that includes both mechanical atrial contraction event signals and mechanical ventricular contraction event signals. Figure 3 In this example, the intracardiac motion signal is an intracardiac signal that also includes mechanical atrial contraction event signals and mechanical ventricular contraction event signals. Control circuit 80 analyzes the intracardiac motion signal to detect cardiac mechanical events, determines a synchronicity measure related to cardiac chamber synchronicity, and adjusts the AV interval and / or ventricular interval based on the synchronicity measure as needed to improve cardiac chamber synchronicity.

[0055] As used herein, “chamber synchronicity” can refer to the synchronicity between atrial contraction and subsequent ventricular contraction, and / or the synchronicity between simultaneous right ventricular and left ventricular contractions. Chamber synchronicity can further include the synchronicity between different segments of the heart chambers, such as the synchronicity or coordination between the apical, mid, and basal segments of the left ventricle in the anterior, septal, and inferior walls. For example, the mechanical synchronicity between atrial and ventricular contractions can be considered “optimized” when the AV interval allows ventricular contraction to begin no earlier than the end of atrial contraction and / or when a synchronicity measure related to ventricular contractile force is maximized relative to other AV intervals. Mechanical synchronicity between left and right ventricular contractions or their segments can be considered “optimized” when a synchronicity measure indicates that the simultaneity of left and right ventricular contraction and relaxation is maximized. The following is combined with… Figure 5 An example of a synchronicity measure that can be determined by control circuit 80 is described.

[0056] In some instances, control circuitry 80 may further analyze the motion signal received from motion sensor 90 to determine a measure of the patient's physical activity, thereby providing rate-responsive pacing. The measure of the patient's physical activity determined from the motion sensor signal may be correlated with the need for increased cardiac output or increased metabolic demand, which can be used by control circuitry 80 to determine the pacing rate indicated by the sensor. Control circuitry 80 may adjust a programmed basic lower pacing rate to a temporary, higher pacing rate based on the pacing rate indicated by the sensor. For example, the programmed basic lower pacing rate may be 40 to 60 pulses per minute. Control circuitry 80 may increase the pacing rate based on the pacing rate indicated by the sensor, the rate of which can be determined using a transfer function that correlates the measure of patient activity with a target heart rate required to support the indicated level of patient activity.

[0057] The pacemaker 10 may include telemetry circuitry 88 for wireless communication with external devices such as programmers or home monitors. The telemetry circuitry 88 can be configured to use, for example... Radio frequency (RF) links, such as Wi-Fi, Medical Implantable Communication Services (MICS), or other communication bandwidths, are used to establish communication links with external devices. For example, telemetry circuit 88 can be configured to communicate with devices such as... Programmer or The patient monitor (both are available from Medtronic, Inc., Minneapolis, MN, USA) communicates with an external programmer or monitor. Control parameters used by control circuitry 80 for sensing cardiac events and controlling the delivery of pacing therapy can be programmed into memory 82 via telemetry circuitry 88. Telemetry circuitry 88 includes a transceiver and antenna for communicating with external devices according to an implemented communication protocol. Under the control of control circuitry 80, telemetry circuitry 88 can receive downlink telemetry from external devices and transmit uplink telemetry to said external devices. In some cases, telemetry circuitry 88 can be used to transmit and receive communication signals from another medical device implanted in the patient.

[0058] Figure 5 This is a diagram 100 of cardiac signals that can be generated by pacemaker 10, including atrial and ventricular electrical and mechanical event signals that can be detected by control circuitry 80 to determine a synchronicity measure. The synchronicity measure may be related to the mechanical synchronicity or contractility of the heart chambers. Control circuitry 80 may adjust the AV pacing interval and / or interventricular pacing interval based on one or more determined synchronicity measures to promote heart chamber synchronization and / or improve contractility. The synchronicity measure is determined by detecting one or more mechanical events from motion sensor signals received from motion sensor 90 and determining a measure or characteristic based on the detected mechanical events.

[0059] Figure 5 An electrocardiogram (EGM) signal 102 and a motion signal 110, which can be generated separately by sensing circuitry 86 and motion sensor 90, are shown. EGM signal 102 can be generated from cardiac electrical signals received by pacemaker 10, for example, via electrodes 42 and 24. In this example, motion signal 110 is an acceleration signal generated by motion sensor 90 when pacemaker 10 is fully implanted into the right atrial cavity. Motion signal 110 can be referred to as intraatrial motion signal.

[0060] EGM signal 102 includes a P wave 104 accompanied by atrial myocardial depolarization. Atrial sensing channel 87 of sensing circuit 86 can be configured to generate an atrial sensing event signal 120, which is transmitted to control circuit 80 to indicate that a P wave 104 has been sensed. An atrial contraction event, labeled A4 signal 116 in motion signal 110, follows each P wave 104 and represents mechanical contraction of the atrium. A4 signal 116 is also referred to herein as a "mechanical atrial contraction event".

[0061] EGM signal 102 comprises a paced R-wave signal 106 and an intrinsic R-wave signal 108, each accompanied by depolarization of the ventricular myocardium. Each R-wave 106 and 108 is followed by a corresponding A1 signal 112 and 118 of the motion signal 110. A1 signals 112 and 118 occur with ventricular contraction following electrical depolarization and may correspond to the onset of ventricular mechanical contraction. Each A1 signal 112 and 118 is followed by a corresponding A2 signal 114 and 119, which may occur with the closure of the aortic and pulmonary valves, thus marking the approximate shift or end of ventricular mechanical contraction (and the onset of ventricular mechanical diastole). Both A1 signals (112 and 118) and A2 signals (114 and 119) are referred to herein as “ventricular systolic event signals” because the A1 signal marks the onset of mechanical contraction, while the A2 signal marks the end of ventricular mechanical contraction.

[0062] In some instances, the time relationship between the electrical event of the EGM signal 102 and the mechanical event of the motion signal 110, and / or the time relationship between two mechanical events of the motion signal 110, can be determined as a synchronicity measure. This synchronicity measure is used to set and adjust the pacing interval, which controls the timing of ventricular pacing pulses delivered by the pacemaker 10. Examples of various synchronicity measures that can be determined and used by the control circuitry 80 are described below. To determine such a synchronicity measure, the control circuitry 80 detects motion signal events, such as signals A1, A2, and / or A4. To detect desired mechanical events from the motion signal 110, the control circuitry 80 can set various time windows and / or thresholds or other detection criteria for detecting signals A1, A2, and A4.

[0063] For example, the A4 signal 116 can be detected by setting an A4 window 150 after an atrial sensing event signal 120 received from sensing circuit 86. The A4 signal 116 can be detected in response to an A4 amplitude sensing threshold crossover during the A4 window 150. The A4 window 150 can expire after a predetermined time interval or upon receiving a ventricular sensing event signal 124 (or delivery of a ventricular pacing pulse 122). After detecting the A4 signal 116 in response to a threshold crossover, control circuit 80 can detect the peak amplitude, negative peak slope, return to baseline, or A4 signal terminus 115 or other characteristics of the A4 signal 116 to identify the signal sampling time point used to determine the synchronicity measure as a time interval (e.g., the time interval from said A4 signal terminus 115 to the immediately following A1 signal 112 or 118). In other instances, the A4 window 150 can be set relative to a ventricular event, for example, after the postventricular atrial refractory period following a ventricular pacing pulse 122 or a ventricular sensed event signal 124.

[0064] In some instances, an A1 window 130 may be set after the ventricular pacing pulse 122 to detect the paced A1 signal 112 based on the A1 amplitude threshold crossover of the motion signal 110 during the A1 window 130. Similarly, an A1 window 134 may be set after the ventricularly sensed event signal 124 to detect the intrinsic A1 signal 118. A1 windows 130 and 134 may have the same or different durations due to any difference between the timing of the mechanical contraction following the intrinsic R wave and the timing of the mechanical contraction following the ventricular pacing pulse. Figure 5 As shown, in some cases, A1 signals 112 and 118 may have bimodal peaks. Intra-atrial or inter-ventricular A1 signals may contain two or more peaks due to ventricular asynchrony between the right and left ventricles and / or regional asynchrony of ventricular segments. Intracardiac (or epicardial motion signals) can be more sensitive to regional or segmental and / or inter-ventricular asynchrony, resulting in multi-peaked A1 signals rather than signals from other types of sensors further away from the heart, providing a more comprehensive signal of cardiac electrical and / or mechanical events. The timing of characteristics of the A1 signal (e.g., first peak, second peak, maximum peak, maximum slope, or other features) can be identified by control circuitry 80 for determining the synchronicity measure as the time interval beginning or ending with A1 signal 112. In other instances, the synchronicity measure can be determined as characteristics of the A1 signal, such as maximum peak amplitude, signal width, maximum slope, number of peaks, or other features that may indicate ventricular synchronicity or contractility.

[0065] Control circuit 80 may set A2 window 132 after ventricular pacing pulse 122 and A2 window 136 after ventricularly sensed event signal 124 to aid in the detection of A2 signals 114 and 119, respectively. A2 windows 132 and 136 may have the same or different durations because the timing of A2 signal 119 after the inherent R wave 108 may differ from the timing of A2 signal 114 after ventricular pacing pulse 122. A2 signals 114 and 119 may be detected during the corresponding A2 windows 132 and 136 after the corresponding A1 windows 130 and 134 have expired or after the corresponding A1 signals 112 and 118 have been detected. The timing of A2 signal detection in response to threshold amplitude crossover of motion signal 110 and / or the timing of characteristics of A2 signals 114 or 119 identified by control circuit 80 (e.g., maximum peak amplitude, maximum slope (or derivative), number of peaks, or signal width) can be determined to determine a synchronicity metric.

[0066] In other instances, detection of end 115 of the A4 signal 116 can be used to set the A1 time window 140 and / or the A2 time window 142 to help detect ventricular mechanical event signals 112, 114, 118 or 119 following the end of the A4 signal 116. Figure 5 Various examples of sensing windows that can be used to assist in the detection of cardiac mechanical events from motion signal 110 are depicted. It should be understood that mechanical event sensing control parameters, including sensing threshold amplitude and sensing window, can be set according to the needs of individual patients. Various sensing windows for assisting in the detection of specific cardiac mechanical events can be defined relative to previous electrical or mechanical events identified by control circuitry 80.

[0067] Figure 6 yes Figure 5 A diagram 180 of the EGM signal 102 and motion signal 110 illustrates various examples of synchronicity measures that can be determined by the control circuit 80 using the motion signal 110. Various time intervals for the start and / or end of cardiac mechanical events detected from the motion signal 110 or cardiac mechanical event signal characteristics can be determined by the control circuit 80 as synchronicity measures. Different synchronicity measures can be determined for setting and adjusting the AV interval, thereby controlling ventricular pacing and / or setting the ventricular interval according to clinical application. In some instances, the timing of the A4 signal 116 (specifically, terminal 115 of the A4 signal 116) relative to the ventricular pacing pulse 122 or the A1 signal 112 can be determined as a synchronicity measure. Ventricular contraction should begin after atrial contraction has completed to avoid incomplete ventricular filling during atrial contraction and to avoid ventricular contraction against the still-contracting atrial cavity. Therefore, the control circuit 80 can determine the A4-A1 time interval 182 from the reference point of the A4 signal 116 to the reference point of the A1 signal 112 as a synchronicity measure. The reference point of the A4 signal 116 can be the time when an A4 event is detected based on the motion signal exceeding the A4 sensing threshold amplitude 170, the maximum peak amplitude of the A4 signal 116, the end time 115 of the A4 signal 116, the maximum negative slope of the A4 signal, or other reference points identified by the control circuit 80 as reference time points for atrial mechanical contraction. The reference point of the A1 signal 112 can be the time when an A1 event is detected based on the motion signal exceeding the A1 sensing threshold amplitude 172, the maximum peak amplitude of the A1 signal 116, the maximum positive slope of the A1 signal, or other reference points identified by the control circuit 80 as reference time points for the start of ventricular mechanical contraction. If the A4-A1 time interval 182 is less than (or greater than) the threshold interval (or outside the target range), the AV pacing interval 178, which is initiated in response to the atrial sensing event signal 120, can be adjusted until the A4-A1 time interval falls within the target range or is at least longer than the minimum A4-A1 time interval threshold.

[0068] In some instances, a target synchronicity metric can be determined during non-paced, intrinsic ventricular beats. For example, in patients undergoing bradycardia ventricular pacing to treat intermittent AV block, a synchronicity metric can be determined and used to set a target synchronicity metric value or range that is desired when delivering ventricular pacing pulses in the absence of an intrinsic R wave. Patients experiencing intermittent AV block may intermittently have normal conduction, which can result in normal synchronicity between the atria and ventricles, and between the right and left ventricles. An intrinsic A4-A1 interval 188 can be determined between an A4 signal 116 following a ventricularly sensed event signal 124 and a subsequent A1 signal 118. The intrinsic A4-A1 interval 188 can be used as a target A4-A1 interval during ventricular pacing. When the A4-A1 interval 182 during ventricular pacing is shorter than the inherent A4-A1 interval 188 or a percentage thereof, the control circuit 80 may increase the AV interval 178. When the paced A4-A1 interval 182 is longer than the inherent A4-A1 interval 188 or a percentage thereof, the control circuit 80 may decrease the AV interval 178. When the A4-A1 interval 182 during ventricular pacing is within a threshold or target range of the inherent A4-A1 interval 188, the control circuit 80 may keep the AV interval 178 unchanged. It should be recognized that in some instances, a target A4-A1 interval based on the inherent A4-A1 interval 188 can be determined for multiple different atrial rates, thereby allowing the AV interval 178 to be adjusted according to the target A4-A1 interval for a given heart rate or heart rate range.

[0069] In other instances, patients may experience conduction delays or even complete AV block during the inherent AV conduction period, rendering the inherent A4-A1 interval useless or undeterminable for setting a target value for the A4-A1 interval used as a measure of synchronicity during ventricular pacing. In such cases, the target A4-A1 interval can be set based on empirical data or established during other AV interval optimization studies on the patient, for example, using echocardiography or other hemodynamic assessments or measurements to determine the optimized AV interval 178. When the AV interval 178 is deemed optimal for a given patient based on echocardiography or other clinical hemodynamic assessments, the optimized A4-A1 interval can be determined from the motion signal 110 and used as the target A4-A1 interval in adjusting the AV pacing interval 178.

[0070] Other synchronicity measures can be determined from motion signal 110, which can be used as a supplement or alternative to the A4-A1 time interval for adjusting the pacing interval. Other synchronicity measures that can be determined by control circuitry 80 include the A1 width interval 184 and / or the A1-A2 interval 186. The A1 width interval 184 can be the time interval between two individual peaks of a biphasic A1 signal, as in the example of A1 signal 112. The A1 width interval between the two peaks of A1 signal 112 can be correlated with synchronicity between the RV and LV (or segments thereof), where one peak may correspond to right ventricular contraction and the other to left ventricular contraction. In other instances, the A1 width can be, for example, the width of a single-peak A1 signal at a predefined threshold amplitude. A relatively long A1 width interval 184 can indicate an increase in ventricular asynchrony. The AV interval 178 can be adjusted until the A1 width interval 184 is minimized or until the A1 signal 112 decreases from two peaks to a single peak, indicating improved ventricular synchrony. Improved ventricular synchrony can include improved simultaneous synchronous contraction of the left and right ventricles and / or improved coordinated contraction of segments of one of the left or right ventricles. For example, in some patients, the contraction of a portion of the ventricular wall of a ventricular cavity (right or left ventricle) may be delayed compared to other parts or segments of the ventricular cavity. For illustration, the contraction of the left ventricular lateral wall may be delayed compared to other parts of the left ventricle. The synchrony measure corresponding to the improved ventricular synchrony between ventricular segments can correspond to a correction or reduction of regional or segmental contraction delays within the ventricular cavity.

[0071] Another example measure of synchronicity is the A1-A2 interval 186, determined between reference points of A1 signal 112 and A2 signal 184. For example, the A1-A2 interval 186 can be determined between motion signal 110 exceeding an A1 sensing threshold 172 and motion signal 110 exceeding an A2 sensing threshold 174. Alternatively, the A1-A2 interval 186 can be determined as the interval between the maximum peak value of A1 signal 112 and the maximum peak value of A2 signal 116, or another combination of the reference points of A1 signal 112 and A2 signal 116 defining the A1-A2 interval. The A1-A2 interval 186 can be correlated with the ventricular systolic time interval or ejection period and can be an indicator of ventricular synchronicity. The A1 width 184 and / or the A1-A2 interval 186 can be determined during ventricular pacing and compared to corresponding target widths and target A1-A2 intervals. The target A1 width and the target A1-A2 interval may be based on the inherent A1 width and inherent A1-A2 interval determined during non-paced ventricular beats, or on the A1 width and A1-A2 interval determined during other pacing interval optimization procedures such as echocardiography.

[0072] In other instances, synchronicity measures can be defined as the time interval between inherently sensed or paced cardiac electrical events and cardiac mechanical events. For example, the Vpace-A1 interval 190 can be defined as the time interval from the ventricular pacing pulse 122 to the maximum peak amplitude of the A1 signal 112 or other reference point. The Vpace-A2 interval 192 can be defined as the time interval from the ventricular pacing pulse 122 to the maximum peak amplitude of the A2 signal 116 or other reference point. In some instances, when the Vpace-A1 interval 190 or Vpace-A2 interval 192 is used as a synchronicity measure, a target range or threshold for the synchronicity measure can be set based on the corresponding inherent Vsense-A1 interval 194 or inherent Vsense-A2 interval 196 determined during non-paced ventricular beats.

[0073] The synchronicity measure is not limited to being determined as a time interval. In other instances, the synchronicity measure may be determined as a characteristic of the A1 and / or A2 signals. In some instances, the control circuit 80 may set the A1 window 130 and / or the A2 window 132 (see...). Figure 5 Furthermore, motion signal sampling points with amplitudes greater than a predetermined threshold can be identified during the A1 window 130 and / or A2 window 132. A synchronicity metric can be determined from the identified sampling points, which may include, for example, integrating or summing the sampling points, counting the sampling points, determining the slope from the identified sampling points, or determining the maximum peak amplitude from the identified sampling points. The identified sampling points may include sampling points from one or both of the A1 signal 112 and the A2 signal 114. For example, the area of ​​the A1 signal 112 with amplitudes greater than a predetermined baseline or threshold can be determined by an integrator or summing circuit included in the control circuitry 80 and can be an indicator of ventricular synchronicity. As the A1 signal area increases, greater ventricular asynchrony may occur between the left and right ventricles and / or between regions of a ventricular cavity. Based on the target A1 signal area, the AV interval 182 can be adjusted (increased or decreased) until the A1 signal area is minimized (reaching the minimum of all tested AV intervals) or falls within the target range or below the target threshold.

[0074] In another example, the number of sampling points for the A1 signal and / or A2 signal can be counted, where the sampling points are greater than a predetermined threshold amplitude and are within window 130 of A1, within both window 130 of A1 and window 132 of A2, or within window 130 of A2 but not within window 130 of A1. Figure 5(Window A1 130 and window A2 132 are shown). A synchronicity measure can be determined as the number of sampling points greater than the predetermined threshold. A relatively high sampling point count can be associated with greater ventricular asynchrony. The sampling point count can be determined by the firmware or software of processor 92 or by comparators and counters implemented in the hardware of control circuitry 80.

[0075] In other instances, the area of ​​motion signal 110 within window A1 130, the area of ​​motion signal within window A2 132, the maximum peak amplitude of signal A1 112, the maximum peak amplitude of signal A2 114, the maximum slope (positive or negative) of signal A1 112, the maximum slope (positive or negative) of signal A2 114, or any combination thereof, can be identified as one or more synchronicity measures used to control the adjustment of AV interval 182 (or ventricular interval) in a manner that promotes normal or improved cardiac synchronicity. Another example synchronicity measure can be identified as a measure of the variability of motion signal 110 within window A1 130 and / or window A2 132. For example, the number of inflection points or the number of threshold crosses can indicate changes in the motion signal associated with ventricular synchronicity. A larger number of inflection points or a larger number of threshold crosses during windows A1 and / or A2 can be evidence of increased ventricular asynchrony. The pacing interval, which controls the timing of ventricular pacing pulse delivery, can be adjusted to reduce the number of inflection points or threshold crossovers during the A1 and / or A2 windows.

[0076] In some patients, such as those diagnosed with heart failure, ventricular pacing can be delivered by pacemaker 10 to provide CRT to improve ventricular synchrony. Therefore, a synchrony measure can be determined from the A1 signal 112 and / or the A2 signal 114, which are associated with ventricular synchrony. The AV interval 178 can be adjusted until the synchrony measure indicates an improvement in ventricular synchrony, depending on the synchrony measure being determined; the improvement may be an increase or decrease in the synchrony measure value. Because inherent AV conduction and conduction through the inherent ventricular conduction system (if present) may be abnormal or delayed, a target value for the synchrony measure can be determined based on empirical data, or from the motion signal 110 when the AV interval is considered optimal based on other clinical measurements or assessments such as echocardiography studies. When pacemaker 10 is implanted in the RV, the AV interval and / or ventricular interval can be adjusted until the synchrony measure indicates an improvement in ventricular synchrony.

[0077] exist Figure 4 and 5In this example, the atrial electrical event shown in the EGM signal 102 is an inherently atrial-sensed event, such as a P wave sensed by the atrial channel 87 of the sensing circuit 86. However, it should be understood that the atrial electrical event used to set the A4 window 150 and trigger the start of the AV interval 178 can be an atrial pacing pulse delivered by the pacemaker 10. The patient may be pacemaker-dependent and require long-term atrial pacing. In some cases, atrial pacing pulses are delivered in response to the absence of a sensed P wave or at a pacing rate indicated by the sensor to provide rate-responsive pacing. The AV interval following the atrial pacing pulse can be set differently from the AV interval set after the atrial-sensed event signal. However, in both cases, the AV interval can be adjusted based on a synchronicity metric to facilitate optimized chamber synchronization. The target value or range of the synchronicity metric can be the same during atrial sensing and atrial pacing, as the target value indicates optimization and improvement of the synchronicity of the chamber mechanical function. In other instances, the target values ​​or ranges for the synchronicity measure of the AV interval used during atrial sensing can be defined differently than those used to adjust the AV interval synchronization measure during atrial pacing. The heart's contractile response can differ during atrial pacing and atrial sensing. Therefore, different target values ​​or ranges for the synchronicity measure can indicate optimization of cardiac chamber synchronicity during atrial sensing and atrial pacing. Furthermore, different synchronicity measures can be determined during atrial sensing to adjust the sensing-AV interval, compared to those determined during atrial pacing.

[0078] In some instances, the atrial event that initiates the AV pacing interval is the sensed A4 signal 116. Figure 3 In this example, when pacemaker 10 is implanted in the ventricular cavity, control circuitry 80 can be configured to detect A4 signal 116 and initiate an AV pacing interval. In this case, the AV pacing interval is set relatively short compared to an AV pacing interval 178 initiated in response to an atrial sensing event signal 120, because ventricular contraction should begin at or shortly after the completion of atrial contraction. However, in both cases, the AV pacing interval can be adjusted based on a synchronicity measure determined after ventricular pacing pulse delivery and an established target value for said synchronicity measure.

[0079] Figure 7This is a flowchart 200 of a method performed by pacemaker 10 to control the AV interval during ventricular pacing synchronized with the atria, according to an example. At block 201, target values ​​for one or more synchronicity measures are established. As described above, the target values ​​can be based on the value of a synchronicity measure determined during the inherent conduction period to the ventricle, which may follow an atrial pacing pulse or an inherently sensed P wave. For example, if the synchronicity measure is the A1 signal width, the A1 signal width can be measured when ventricular pacing is not delivered. The target value can be set as a maximum threshold for the A1 signal width, which can be defined as a percentage of the A1 signal width or a predetermined interval greater than the A1 signal width. In this example, it is assumed that an increase in the A1 signal width exceeding the target value indicates a trend of asynchronous increase in RV and LV contractions.

[0080] In another instance, if the synchronicity measure is the A4-A1 interval, this A4-A1 interval can be determined during ventricular sensing (before ventricular pacing pulses are delivered). A target A4-A1 interval range can be set based on a target A4-A1 interval value determined during ventricular sensing. A minimum A4-A1 interval can be defined as a first percentage of the A4-A1 interval determined during ventricular sensing and can represent the minimum time delay from the end of atrial mechanical contraction to the beginning of ventricular contraction. A maximum A4-A1 interval can be defined as a second percentage of the A4-A1 interval determined during ventricular sensing and can represent the maximum time delay from the end of atrial mechanical contraction to the beginning of ventricular contraction, to promote optimal hemodynamic function during ventricular pacing.

[0081] In other instances, target thresholds or ranges for one or more synchronicity measures can be programmed into memory 82 by a user at box 201, for example, using an external programmer. When it is determined during ventricular pacing that the AV interval will be optimized, such as during an echocardiography study, based on another clinical measurement or assessment method, a target synchronicity measure value can be determined. A target value for the synchronicity measure can be determined during ventricular pacing with an optimized AV interval, and a target threshold or range based on the determined target synchronicity measure value can be programmed into memory 82.

[0082] At box 202, control circuitry 80 detects an atrial event. In some instances, the atrial event is an electrical event. The atrial electrical event may be an inherent P wave sensed by sensing circuitry 86 or an atrial pacing pulse delivered by therapy delivery circuitry 84. However, in some instances, the atrial event detected at box 202 may be an A4 signal sensed from motion signals received from motion sensor 90. Control circuitry 80 initiates an AV interval at box 204 in response to the detection of an atrial event. The AV interval initiated at box 204 may be a sensed AV (SAV) interval following the sensed P wave, a paced AV (PAV) interval following the delivered atrial pacing pulse, or an A4-V interval following the sensed A4 signal. The SAV interval, PAV interval, and A4-V pacing interval may each be different intervals to account for the differences in the relative timing of atrial and ventricular electrical events and atrial and ventricular mechanical events. Furthermore, the SAV interval can be set differently when the sensed P wave is a sinus P wave caused by the sinoatrial node, compared to the SAV interval set when the sensed P wave is an ectopic beat or atrial premature contraction (PAC). For example, a PAC can be sensed when a P wave is sensed consecutively after a previously sensed P wave or atrial pacing pulse without any ventricular event intervention. If the PAC is sensed early, such as during the atrial refractory period, it can be ignored. However, if the PAC is sensed after the atrial refractory period has elapsed, the control circuit 80 can initiate the SAV interval at box 204 in response to the sensing of a PAC at box 202. The SAV interval initiated in response to a PAC can be set to a different interval than the SAV interval initiated in response to a sinus P wave.

[0083] If an R-wave is sensed at box 208, for example, a ventricular sensed event signal is received from sensing circuit 86, then before the AV interval expires (the "No" branch of box 206), control circuit 80 cancels the scheduled ventricular pacing pulse and returns to box 202 to wait for the next atrial event to begin the next AV interval. In some instances, control circuit 80 may return from box 208 to box 201 when an inherent R-wave is sensed and the target synchronicity measurement threshold or range is based on a synchronicity measurement target value determined during ventricular sensing. Control circuit 80 may determine a synchronicity measurement value after the ventricular sensed event and update the target synchronicity measurement threshold or range at box 201 based on the determined value. For example, multiple synchronicity measurement values ​​determined during the inherent, sensed ventricular cycle may be stored and averaged on a first-in-first-out basis (where outliers are ignored), or a weighted combination of the most recently stored synchronicity measurement target value (which may be the average of multiple values) and the currently measured synchronicity measurement value may be determined as the updated synchronicity measurement target value. The target value can be used to set a target threshold or range for a synchronicity measure used to control AV interval adjustment.

[0084] When the AV interval expires at box 206 and the R wave is not sensed, a ventricular pacing pulse is delivered at box 210 via therapy delivery circuit 84. Control circuit 212 determines a synchronicity measure at box 212 after the ventricular pacing pulse. In some instances, the synchronicity measure can be determined beat-by-beat after each ventricular pacing pulse to allow the AV interval to be adjusted as frequently as each ventricular pacing pulse delivery. In other instances, the synchronicity measure is determined at box 212 when the ventricular pacing pulse delivered at box 210 is the nth ventricular pacing pulse, where n is a predetermined number of ventricular pacing pulses. For example, it can be determined every 8... th 12 pacing pulses, every 12 th pacing pulses, every 20 th The synchronicity measure can be determined by a number of pacing pulses or by other selected number of pacing pulses. In other instances, the synchronicity measure can be determined at box 212 according to a predetermined schedule, such as once per day, once per hour, once per minute, or other frequencies. Furthermore, it should be recognized that determining the synchronicity measure at box 212 can involve determining the synchronicity measures of multiple pacing ventricular cycles and combining the determined values ​​by averaging or other statistical methods to determine a representative synchronicity measure of the currently applied AV interval, which can be the SAV interval, PAV interval, PAC-AV interval, or A4-V interval.

[0085] At box 214, control circuit 80 compares the synchronicity measure with a target synchronicity measure threshold or range. If the synchronicity measure determined at box 212 meets the target synchronicity measure threshold or range established at box 201, control circuit 80 returns to box 202 without adjusting the AV interval to await the next atrial event. The synchronicity measure determined at box 212 may not meet the target threshold or range if the synchronicity measure is less than the minimum threshold established at box 201 or greater than the maximum threshold established at box 201. In response to the synchronicity measure determined at box 212 not meeting the target synchronicity measure requirement at box 214, control circuit 80 adjusts the AV pacing interval at box 216.

[0086] Adjusting the AV interval can involve increasing or decreasing the step interval, such as 10ms, 15ms, 20ms, 25ms, 30ms, 50ms, or other selected intervals. Depending on the synchronicity metric value determined at box 212 and the corresponding target threshold or range, the AV interval adjustment can be, for example, an increase when the A4-A1 interval is too short, or a decrease when the A4-A1 interval is too long. In some instances, the AV interval can be increased or decreased in a single step based on the difference between the target value and the synchronicity metric value determined at box 212. In this way, the AV interval can be corrected in a single adjustment to bring the synchronicity metric within the target requirement range.

[0087] In some cases, it may not be obvious whether the AV interval needs to be increased or decreased, or by how much. Therefore, the adjustment at box 216 can be incremental or incremental, and the process from box 202 to box 216 can be repeated until the synchronicity measure determined at box 212 meets the synchronicity measure requirement at box 214. This may include multiple increases and / or decreases in the AV interval.

[0088] Figure 8 This is a flowchart 300 of a method for controlling AV intervals via pacemaker 10, according to another example. Pacemaker 10 can be configured to learn an optimized synchronicity metric value by adjusting the AV interval until a change in the synchronicity metric associated with improved cardiac synchronicity is achieved, without requiring additional AV interval adjustments to obtain further improvement. Control circuitry 80 can determine one or more synchronicity metrics during ventricular pacing with multiple AV interval settings and select the AV interval setting that produces the synchronicity metric value considered to generate the greatest improvement or considered more optimized than other synchronicity metric values ​​determined under other AV interval settings, rather than combining... Figure 7 As described, a target synchronization metric threshold or range is established based on the target value.

[0089] At box 302, control circuit 80 detects an atrial event, such as an atrial pacing pulse, a sensed P wave, or a sensed A4 signal. Control circuit 80 initiates an AV interval at box 304 in response to the detection of an atrial event. If an R wave is sensed by the sensing circuit (box 308) before the AV interval expires (box 306), for example, when an R wave-sensing event signal is received from sensing circuit 86 during the AV interval, control circuit 80 waits for the next atrial event. Scheduled ventricular pacing pulses are suppressed.

[0090] When the AV interval expires at box 306 and the R wave is not sensed, a scheduled ventricular pacing pulse is delivered via therapy delivery circuit 84 at box 310. At box 312, control circuit 80 determines a synchronicity measure from the motion signal. The synchronicity measure can be a combination of the above. Figure 5 and 6 In any given instance, and in some instances, more than one measure of synchronicity may be determined. In one instance, the A4-A1 interval is determined in addition to at least one other measure of ventricular mechanical events, such as A1 amplitude, A1 width, A1-A2 interval, or other measures that may indicate RV and LV synchronicity. At block 314, each measure of synchronicity determined at block 312 may be compared with a previously determined measure of synchronicity. This comparison may be performed by control circuitry 80 by determining a trend or difference between the currently determined value and the previously determined value of the synchronicity measure.

[0091] If the currently determined value represents an improvement in cardiac synchrony, as determined at box 316, then at box 320, control circuit 80 can adjust the AV interval to another test interval. The AV interval can continue to be adjusted until no further improvement is achieved based on the determination at box 316. If the value of the measurement increases or decreases compared to a previous value (depending on what the measurement is), control circuit 80 can determine that the synchrony measurement has been improved. For example, an increase in the peak amplitude of A1 can indicate an improvement in ventricular synchrony, while an increase in the width or area of ​​A1 can indicate a deterioration in the value. An increase in the duration of ventricular mechanical events, such as the Vpace-A1, Vpace-A2, or A1-A2 intervals, can indicate a deterioration in the value associated with an increase in ventricular asynchrony, while a decrease in the ventricular duration value can indicate an improvement in the value associated with an improvement in ventricular synchrony.

[0092] If the currently determined synchronicity metric value is not determined by the control circuit 80 to be an improved value at block 316 and is not determined to be a worse value than the previous value (e.g., remains unchanged), at block 320, while searching for an AV interval that would improve the synchronicity metric, the control circuit 80 can adjust the AV interval to another test setting. However, when the synchronicity metric value is determined to be a worse value than the previous value, at block 322, the AV interval can be adjusted back to the previous AV interval setting. The previous AV interval setting is the setting corresponding to the synchronicity metric with the greatest degree of improvement (to date), which is determined relative to other synchronicity metric values ​​determined for all AV intervals tested.

[0093] It should be recognized that when monitoring two or more synchronicity measures during AV interval adjustment, one synchronicity measure can act as a constraint on possible AV interval settings and the maximum possible variation achievable in another synchronicity measure. For example, when the A4-A1 interval is at a minimum limit, the A4-A1 interval may be limited by the minimum limit, preventing further reduction of the AV interval to improve A1 amplitude or A1 width. Within the AV interval limit defined by the minimum A4-A1 interval, another synchronicity measure that indicates ventricular synchronicity can be optimized (e.g., minimized or maximized).

[0094] Figure 8 The process can be executed by pacemaker 10 on a per-beat basis, allowing control circuitry 80 to adjust the AV interval as needed to maintain an improvement in one or more monitored synchronicity measures. In other instances, the process of flowchart 300 can be executed on a scheduled, periodic basis, so that once an optimal AV interval is found based on achieving the improved synchronicity measure, said optimal AV interval can be used until the process of flowchart 300 is scheduled to be executed again. In still other instances, the process of determining a synchronicity measure and adjusting the AV interval during ventricular pacing to achieve an improvement in said synchronicity measure or a target threshold or range can be executed on a triggered basis.

[0095] Figure 9 This is a flowchart 350 illustrating a method for controlling the interventricular pacing interval based on an example. (e.g.) Figure 3As shown, pacemaker 10 can be positioned in the right ventricle to provide LV pacing using distal ventricular electrode 42. LV pacing pulses can be delivered with an AV pacing interval after a sensed A4 signal from a motion signal or after an interventricular pacing interval between the RV and LV to provide cardiac resynchronization therapy. The interventricular pacing interval can be initiated in response to the sensing of an R wave in the RV or in response to the delivery of RV pacing pulses using distal housing-based electrode 22 and proximal housing-based electrode 24. In some instances, atrial-synchronized biventricular pacing is delivered by initiating an AV interval in response to the sensing of an A4 signal from a motion signal to deliver ventricular pacing pulses to the first ventricular chamber, RV, or LV, and then an interventricular pacing interval is initiated in response to the first ventricular pacing pulse to time the delivery from the second ventricular pacing pulse to the second ventricular chamber, LV, or RV.

[0096] At box 351, a target synchronicity metric value is established via control circuitry 80 using any of the example techniques described above. The target synchronicity metric value is an indicator of ventricular synchronicity. At box 352, an atrial event is detected. The atrial event may be an A4 signal corresponding to a mechanical atrial contraction event. The atrial event can be detected during an early portion of the A4 signal (e.g., before the peak of the A4 signal) based on an A4 sensing threshold of the motion signal to initiate the AV pacing interval. The AV pacing interval can be adjusted based on the synchronicity metric described above, for example, based on the A4-A1 time interval. The A4-A1 time interval may be the time interval from the end of the A4 signal to the start of the A1 signal to avoid initiating ventricular contraction before the end of the A4 signal. As an example, the end time of the A4 signal (e.g., when returning to the baseline amplitude, a negative crossover of a predetermined end time threshold amplitude, or a predetermined number of sampling points below a predetermined end time threshold amplitude) can be detected. Figure 5 As shown, such as the end time 115).

[0097] Upon expiration of the AV interval, at box 356, a V1 pacing pulse is delivered to the first ventricular cavity (right or left) via therapy delivery circuit 84. At box 358, control circuit 80 initiates an interventricular pacing interval (V1-V2 pacing interval) in response to the delivery of the first V1 pacing pulse. At box 360, upon expiration of the V1-V2 pacing interval, a second V2 pacing pulse is delivered to the other, opposite ventricular cavity (left or right) via therapy delivery circuit 84. After delivery of the biventricular pacing pulses, at box 362, a synchronicity measure is determined from the motion signal. The synchronicity measure can be any of the examples described above determined from the A1 and / or A2 signals, serving as an indicator of ventricular synchronicity. Control circuit 80 compares the synchronicity measure with a target value (or a threshold or range based on the target value determined at box 351). If the synchronicity measure does not meet the synchronicity requirements, the V1-V2 pacing interval can be adjusted at box 366 via control circuit 80. If the synchronicity requirements applied at box 364 are met, control circuit 80 waits at box 352 to detect the next atrial event without adjusting the V1-V2 pacing interval. Figure 9 The process can be repeated on a beat-by-beat basis or less frequently, for example, every nth cardiac cycle, once per minute, once per hour, once per day, or other scheduled intervals. It should be recognized that in some instances, Figure 7 or Figure 8 The process can be with Figure 9 The process combination is used to adjust the AV pacing interval and the V1-V2 pacing interval.

[0098] Figure 10This is a flowchart 400 of a method for performing pacing interval optimization on a trigger basis using a pacemaker 10. At block 402, control circuitry 80 detects a trigger event to optimize the pacing interval based on at least one synchronicity metric. The optimized pacing interval may be the AV pacing interval and / or the interventricular pacing interval. The trigger event may be a change in cardiac electrical signals or a change in cardiac motion signals. In one example, control circuitry 80 is configured to monitor the R-wave rotation rate from an EGM signal received from self-sensing circuitry 86. The change in the R-wave rotation rate may indicate a change in ventricular synchronicity. For example, a decrease in rotation rate may indicate an increase in ventricular asynchrony. Other changes in the R-wave that may be detected by control circuitry 80 as trigger events may include changes in the peak amplitude of the R-wave and / or changes in the R-wave width. In another example, control circuitry 80 may monitor changes in the slope or peak amplitude of the A1 signal. The control circuit 80 can detect a trigger event at block 402 by detecting a change in the R-wave slew rate, such as a decrease compared to a previously determined slew rate or average slew rate. Alternatively, the control circuit 80 can detect a trigger event at block 402 by detecting a change in the slope or peak amplitude of the A1 signal or other characteristics of the A1 signal compared to a previously determined characteristic value or average value.

[0099] When a trigger event is detected at box 402, at box 404, control circuitry 80 determines one or more synchronicity measures following ventricular pacing delivered with the currently set AV pacing interval and / or V1-V2 pacing interval. These one or more synchronicity measures can be determined according to any of the examples given above. At box 406, control circuitry 80 compares the one or more synchronicity measures to a corresponding target threshold or range. If the determined synchronicity measure meets the target range or threshold, control circuitry 80 returns to box 402 to await the next trigger event. If the synchronicity measure does not meet the target range or threshold, control circuitry 80 adjusts the pacing interval at box 408, and then at box 404, redetermines the synchronicity measure following one or more subsequent ventricular pacing pulses with the adjusted one or more pacing intervals. This process can continue as needed with multiple pacing interval adjustments to adjust to one or both of the AV and intraventricular pacing intervals until one or more synchronization measure target ranges or thresholds are met at box 406.

[0100] In other instances, activation may be initiated in response to the detection of a triggering event (rather than adjusting the pacing interval until a previously established target threshold or range for synchronicity metrics is met). Figure 10During the process, control circuit 80 can adjust one or more pacing intervals to multiple settings (or a combination of AV interval settings and V1-V2 interval settings) until an improvement in the synchronicity measure is detected. This improvement can be the maximum improvement within any predefined limits of the AV interval setting and / or the A4-A1 interval and / or the upper and lower limits of the interventricular pacing interval. Depending on the synchronicity measure, it can be minimized or maximized within any predefined limits of the AV interval, V1-V2 interval, and / or another synchronicity measure.

[0101] The following examples illustrate the exemplary techniques of this disclosure.

[0102] Example 1: A method comprising: generating a motion signal, the motion signal including an atrial contraction event signal, a first ventricular contraction event signal corresponding to the start of ventricular contraction, and a second ventricular contraction event signal corresponding to the end of ventricular contraction; generating a ventricular pacing pulse upon the expiration of a pacing interval; determining a synchronicity measure from the motion signal based on at least one of the first ventricular contraction event signal and the second ventricular contraction event signal following the ventricular pacing pulse; and adjusting the pacing interval based on the synchronicity measure.

[0103] Example 2: The method according to Example 1 further includes: determining the synchronicity measure as the time interval from the atrial contraction event signal to the first ventricular contraction event signal; determining that the time interval is less than a time interval threshold; and increasing the pacing interval in response to the time interval being less than the time interval threshold.

[0104] Example 3: The method according to Example 1 or 2 further includes: determining the synchronicity measure as the time interval ending at one of the first ventricular contraction event and the second ventricular contraction event; determining that the time interval is greater than a threshold time interval; and adjusting the pacing interval in response to the time interval being greater than the threshold time interval to reduce the synchronicity measure.

[0105] Example 4: The method according to any one of Examples 1 to 3 further includes: determining the synchronicity measure by determining the time interval from a first peak of the first ventricular systolic event signal to a second peak of the first ventricular systolic event signal; and adjusting the pacing interval to increase the time interval from the first peak to the second peak.

[0106] Example 5: The method according to any one of Examples 1 to 4 further includes: sensing an inherent R wave accompanying inherent depolarization of the ventricular myocardium; determining a target value for the synchronicity measure from the motion signal following the inherent R wave; setting a threshold for the synchronicity measure based on the target value; determining that the synchronicity measure does not meet the threshold; and adjusting the pacing interval in response to the synchronicity measure not meeting the threshold.

[0107] Example 6: The method according to any one of Examples 1 to 5 further includes: sensing an R wave associated with depolarization of the ventricular myocardium; detecting a change in the R wave; and determining the synchronicity measure from the motion signal in response to detecting the change in the R wave.

[0108] Example 7: The method according to Example 6 further includes detecting the change in the R-wave by detecting the change in the slew rate of the R-wave.

[0109] Example 8: The method according to any one of Examples 1 to 7, wherein: generating the motion signal includes generating an intraatrial motion signal, the intraatrial motion signal including the atrial contraction event signal, the first ventricular contraction event signal and the second ventricular contraction event signal; and when the housing is implanted in the atrial cavity, delivering the generated ventricular pacing pulses through a plurality of housing-based electrodes.

[0110] Example 9: The method according to any one of Examples 1 to 8 further includes: adjusting the pacing interval to a plurality of settings; determining the synchronicity measure of each of the plurality of settings of the pacing interval by determining the synchronicity measure after a ventricular pacing pulse delivered in each of the plurality of settings; comparing the synchronicity measures determined for the plurality of settings of the pacing interval, and based on the comparison, identifying a synchronicity measure that corresponds to the maximum improvement in the synchronicity measure; identifying a setting that corresponds to the maximum improvement in the synchronicity measure among the plurality of settings of the pacing interval; and setting the pacing interval to the identified setting among the plurality of settings of the pacing interval.

[0111] Example 10: The method according to any one of Examples 1 to 9, wherein determining the synchronicity measure includes: setting a time window corresponding to at least one of the first ventricular contraction event and the second ventricular contraction event; identifying sampling points of the motion signal with an amplitude greater than a threshold during the time window; and determining the synchronicity measure from at least a portion of the identified sampling points.

[0112] Example 11: The method according to any one of Examples 1 to 10, wherein adjusting the pacing interval includes adjusting at least one of the atrial-ventricular pacing interval and the interventricular pacing interval.

[0113] Example 12: The method according to any one of Examples 1 to 11 further includes: sensing an inherent P wave accompanying inherent depolarization of the atrial myocardium; setting the pacing interval by setting an atrial-ventricular pacing interval; determining a first synchronicity measure from the motion signal in response to sensing the inherent P wave; adjusting the pacing interval by adjusting the first atrial-ventricular pacing interval based on the first synchronicity measure; generating an atrial pacing pulse; determining a second synchronicity measure from the motion signal in response to the generated atrial pacing pulse; and adjusting a second atrial-ventricular pacing interval based on the second synchronicity measure.

[0114] Example 13: The method according to any one of Examples 1 to 12 further includes: generating a first ventricular pacing pulse delivered to a first ventricular pacing site; initiating an interventricular pacing interval in response to the generation of the first ventricular pacing pulse; generating a second ventricular pacing pulse when the interventricular pacing interval expires, the second ventricular pacing pulse being delivered to a second ventricular pacing site; determining the synchronicity measure from the motion signal after the generation of the second ventricular pacing pulse; and adjusting the pacing interval by adjusting the interventricular pacing interval based on the synchronicity measure.

[0115] Example 14: The method according to any one of Examples 1 to 13 further includes: sensing the atrial contraction event from the motion signal; setting an atrial-ventricular pacing interval in response to sensing the atrial contraction event; generating a first ventricular pacing pulse when the atrial-ventricular pacing interval expires; setting an interventricular pacing interval in response to the generation of the first ventricular pacing pulse; generating a second ventricular pacing pulse when the interventricular pacing interval expires; determining the synchronicity measure from the motion signal after the second ventricular pacing pulse; and adjusting the pacing interval by adjusting the interventricular pacing interval based on the synchronicity measure.

[0116] Example 15: A non-transitory computer-readable storage medium storing a set of instructions, which, when executed by a pacemaker, cause the pacemaker to: generate a motion signal including an atrial contraction event signal, a first ventricular contraction event signal corresponding to the start of ventricular contraction, and a second ventricular contraction event signal corresponding to the end of ventricular contraction; generate ventricular pacing upon the expiration of a pacing interval; determine a synchronicity measure from the motion signal based on at least one of the first and second ventricular contraction event signals following the ventricular pacing pulse; and adjust the pacing interval based on the synchronicity measure.

[0117] It should be understood that, depending on the examples, certain actions or events in any of the methods described herein may be performed in a different order, or may be added, combined, or omitted entirely (e.g., not all described actions or events are necessary for practicing the methods). Furthermore, in some instances, actions or events may be performed, for example, through multithreaded processing, interrupt handling, or simultaneous execution by multiple processors, rather than sequentially. Additionally, although some aspects of this disclosure are described for clarity as being performed by a single circuit or unit, it should be understood that the techniques of this disclosure can be performed by a combination of units, circuits, or processors associated with, for example, a medical device.

[0118] In one or more instances, the described functionality may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software or firmware, the functionality may be stored on a computer-readable medium in the form of one or more instructions or code and may be executed by a hardware-based processing unit. The computer-readable medium may comprise a non-transitory computer-readable storage medium, which corresponds to a tangible medium such as a data storage medium (e.g., RAM, ROM, EEPROM, flash memory, or any other non-transitory medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer).

[0119] Instructions can be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field-programmable arrays (FPGAs), or other equivalent integrated or discrete logic circuit systems. Therefore, as used herein, the term "processor" can refer to any of the foregoing structures or any other structure suitable for implementing the techniques described herein. Furthermore, the techniques can be fully implemented in one or more circuit or logic elements.

[0120] Therefore, pacemakers have been presented with reference to specific examples in the foregoing description. It should be understood that the various aspects disclosed herein can be combined in different combinations than those presented in the accompanying drawings. It should be understood that various modifications can be made to the reference examples without departing from the scope of this disclosure and the appended claims.

Claims

1. A medical device comprising: A motion sensor configured to generate motion signals, the motion signals including an atrial contraction event signal, a first ventricular contraction event signal corresponding to the start of ventricular contraction, and a second ventricular contraction event signal corresponding to the end of ventricular contraction; A therapy delivery circuit configured to generate ventricular pacing pulses, each ventricular pacing pulse being generated upon the expiration of the pacing interval; as well as Control circuit, the control circuit being configured to: A synchronicity measure is determined from the motion signal based on at least one of the first ventricular systolic event signal and the second ventricular systolic event signal following at least one ventricular pacing pulse generated by the therapy delivery circuit; as well as The pacing interval is adjusted based on the synchronicity measure.

2. The medical device according to claim 1, wherein the control circuit is configured to: The synchrony measure is defined as the time interval from the atrial contraction event signal to the first ventricular contraction event signal; Determining that the time interval is less than a time interval threshold; and The pacing interval is increased in response to the time interval being less than the time interval threshold.

3. The medical device according to claim 1, wherein the control circuit is configured to: The synchronicity measure is defined as the time interval ending at one of the first ventricular contraction event and the second ventricular contraction event; Determining that the time interval is greater than the threshold time interval; and The pacing interval is adjusted in response to the time interval being greater than the threshold time interval in order to reduce the synchronicity measure.

4. The medical device according to claim 1, wherein the control circuit is configured to: The synchrony measure is determined by determining the time interval from the first peak of the first ventricular systolic event signal to the second peak of the first ventricular systolic event signal; and The pacing interval is adjusted to increase the time interval from the first peak to the second peak.

5. The medical device according to claim 1, further comprising: A cardiac electrical signal sensing circuit, configured to sense an inherent R wave accompanying the inherent depolarization of the ventricular myocardium. The control circuit is further configured to: A target value for the synchronicity measure is determined from the motion signal following the sensed inherent R-wave, and a threshold for the synchronicity measure is set based on the target value; It is determined that the synchronization measure does not meet the threshold. as well as The pacing interval is adjusted in response to the synchronicity measure not meeting the threshold.

6. The medical device according to claim 1, further comprising: A cardiac electrical signal sensing circuit, the cardiac electrical signal sensing circuit being configured to sense R waves associated with depolarization of the ventricular myocardium; The control circuit is further configured to: Detecting changes in the R wave sensed by the cardiac electrical signal sensing circuit; and The synchronicity measure is determined from the motion signal in response to the detection of the change in the R-wave.

7. The medical device of claim 6, wherein the control circuit is configured to detect the change in the R-wave by detecting a change in the slew rate of the R-wave.

8. The medical device according to any one of claims 1 to 7, further comprising: A housing configured for implantation within the atrial cavity; as well as A ventricular electrode, which is coupled to the housing and configured to advance into the ventricular tissue when the housing is implanted into the atrial cavity; The motion sensor is configured to generate intraatrial motion signals, which include the atrial contraction event signal, the first ventricular contraction event signal, and the second ventricular contraction event signal.

9. The medical device according to any one of claims 1 to 7, wherein the control circuit is configured to: Adjust the pacing interval to multiple settings; The synchronicity measure of each of the plurality of settings of the pacing interval is determined by determining the synchronicity measure after the ventricular pacing pulse delivered in each of the plurality of settings. Compare the synchronicity measures determined for the multiple settings of the pacing interval; Based on the comparison of the synchronization measures, identify the synchronization measure that corresponds to the greatest improvement of the synchronization measure; Identify the setting among the plurality of settings for the pacing interval that corresponds to the maximum improvement in the synchronicity measure; and The pacing interval is set to one of the identified settings among the plurality of settings for the pacing interval.

10. The medical device according to any one of claims 1 to 7, wherein the control circuitry is configured to determine the synchronicity measure by means of the following steps: Set a time window corresponding to at least one of the first ventricular contraction event and the second ventricular contraction event; Identify sampling points of the motion signal with amplitudes greater than a threshold during the time window; as well as The synchronicity measure is determined based on at least a portion of the identified sampling points.

11. The medical device according to any one of claims 1 to 7, wherein the control circuit is configured to adjust the pacing interval by adjusting at least one of the atrial-ventricular pacing interval and the interventricular pacing interval.

12. The medical device according to any one of claims 1 to 7, further comprising a cardiac electrical signal sensing circuit configured to sense an inherent P wave accompanying inherent depolarization of the atrial myocardium. in: The therapy delivery circuit is further configured to generate atrial pacing pulses; The control circuit is further configured to: The pacing interval is set by setting the atrial and ventricular pacing interval; A first synchronicity measure is determined from the motion signal in response to the cardiac electrical signal sensing circuit sensing an inherent P wave; The pacing interval is adjusted by adjusting the first atrial-ventricular pacing interval based on the first synchronicity measure; In response to the generation of an atrial pacing pulse by the therapy delivery circuit, a second synchronicity measure is determined from the motion signal; and Adjust the second atrial-ventricular pacing interval based on the second synchronicity measure.

13. The medical device according to any one of claims 1 to 7, wherein: The therapy delivery circuit is configured to: A first ventricular pacing pulse is generated and delivered to the first ventricular pacing site; as well as A second ventricular pacing pulse is generated when the interventricular pacing interval expires, the interventricular pacing interval starting when the first ventricular pacing pulse is delivered, and the second ventricular pacing pulse is delivered to the second ventricular pacing site; The control circuit is further configured to: The interventricular pacing interval is initiated in response to the delivery of the first ventricular pacing pulse by the therapy delivery circuit. The synchronicity measure is determined from the motion signal following the second ventricular pacing pulse; as well as The pacing interval is adjusted by adjusting the interventricular pacing interval based on the synchronicity measure.

14. The medical device according to any one of claims 1 to 7, wherein: The therapy delivery circuit is configured to: The first ventricular pacing pulse is generated when the atrial-ventricular pacing interval expires; and A second ventricular pacing pulse is generated when the interventricular pacing interval expires, the interventricular pacing interval starting when the first ventricular pacing pulse is delivered; The control circuit is further configured to: The atrial contraction event is sensed from the motion signal; The atrial-ventricular pacing interval is set in response to sensing the atrial contraction event; The interventricular pacing interval is set in response to the generation of the first ventricular pacing pulse; The synchronicity measure is determined from the motion signal following the second ventricular pacing pulse, which is delivered when the interventricular pacing interval expires; as well as The pacing interval is adjusted by adjusting the interventricular pacing interval based on the synchronicity measure.

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