Ventricular event reclassification

Abstract

Cardiac events classified as ventricular events after atrial events may be reclassified as negligible events using the illustrative devices and methods described herein. For example, cardiac events classified as ventricular events within a time window following after atrial events. The negligible events will not be inadvertently used to affect cardiac pacing therapy including, for example, ventricular sense response pacing.

Description

VENTRICULAR EVENT RECLASSIFICATIONCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from U.S. Provisional Patent Application 63 / 545,630 filed 25 October 2023, the entire content of which is incorporated herein by reference.

[0002] The present disclosure relates generally to reclassifying cardiac events as negligible ventricular events to, for example, accurately classify cardiac events and optimize pacing delivered to a patient. Implantable medical devices (IMDs), such as cardiac pacemakers or implantable cardioverter defibrillators, deliver therapeutic stimulation to patients’ hearts thereby improving the lives of millions of patients living with heart conditions. Conventional pacing techniques involve pacing one or more of the four chambers of a patient’s heart 12 as illustrated in FIG. 1, including the left atrium (LA) 33, the right atrium (RA) 26, the left ventricle (LV) 32 and the right ventricle (RV) 28. One common conventional therapeutic pacing technique that treats a slow heart rate, referred to as bradycardia, involves delivering an electrical pulse to a patient’s right ventricular tissue. In response to the electrical pulse, both the right and left ventricles contract. However, the heartbeat process may be significantly delayed because the pulse travels from the right ventricle through the left ventricle. The electrical pulse passes through the muscle cells that are referred to as myocytes. Myocyte-to-myocyte conduction may be very slow. Delayed electrical pulses can cause the left ventricle to be unable to maintain synchrony with the right ventricle.

[0003] In some patients, heart failure can develop such that the heart is too weak to pump blood to the body. Heart failure may be a devastating diagnosis since, for example, fifty percent of heart failure patients have a life expectancy of five years or less. A possible cause of heart failure is due to atrial fibrillation, which is an irregular and often very rapid heart rhythm or arrhythmia. During atrial fibrillation, the atria of the heart can beat out of sync with the ventricles of the heart because of the arrythmia of the atria,which can lead to blood clots in the heart and increase the risk of stroke or heart failure, for example.

[0004] Even for patients with a 1 : 1 ratio of atrial beats per minute to ventricular beats per minute (a 1 : 1 cardiac rhythm), if a cardiac pacing therapy is sensing ventricular events using a lead placed proximate the LBB, sometimes the lead incorrectly identifies an atrial event as a ventricular event, for example, because of the proximity of the lead to the atria. Such a misclassification of ventricular events can lead to mis-timed pacing pulses based on the cardiac therapy being delivered to the patient.

[0005] To avoid potential development of heart failure, some physicians have considered alternative pacing methods that involve the cardiac conduction system. Pacing the cardiac conduction system may quickly conduct electrical pulses (for example, akin to a car driving on a highway), whereas pacing cardiac muscle, or myocardial, tissue may more slowly conduct electrical pulses (for example, akin to a car driving on a dirt road).

[0006] The cardiac conduction system includes the sinoatrial (SA) node 1, atrial intemodal tracts 2, 4, 5 (i.e., anterior internodal 2, middle internodal 4, and posterior intemodal 5), atrioventricular (AV) node 3, His bundle 13 (also known as the atrioventricular bundle or bundle of His), LBB 8a, and RBB 8b as shown in FIG. 1. The arch of aorta 6 and the Bachman’s bundle 7 are also shown in FIG. 1. The sinoatrial node 1, located at the junction of the superior vena cava and right atrium, is considered to be the natural pacemaker of the heart as it continuously and repeatedly emits electrical impulses. The electrical impulses spread through the muscles of RA 26 to LA 33 to cause synchronous contraction of the atria. The electrical impulses are also carried through atrial intemodal tracts to the atrioventricular node 3 — the sole connection between the atria and the ventricles. The conduction through the atrioventricular node or atrioventricular nodal tissue takes longer than through the atrial tissue, which results in a delay between the atrial contractions and the start of the ventricular contractions. The atrioventricular (AV) delay, which is the delay between atrial contractions and ventricular contractions, allows the atria to empty blood into the ventricles. Then, the valves between the atria and ventricles close in conjunction with ventricular contraction via branches of the bundle of His. The bundle of His, or His bundle, 13 is located in the membranous atrioventricular septum near the annulus of the tricuspid valve. The His bundle 13 splits into the left and right bundle branches 8a, 8b and are formed of specialized fibers called “Purkinje fibers” 9. The Purkinje fibers 9 may be described as being capable of rapidlyconducting an action potential down the ventricular septum (VS), spreading the depolarization wavefront quickly through the remaining ventricular myocardium, and producing a coordinated contraction of the ventricular muscle mass.SUMMARY

[0007] This disclosure generally relates to determining a misclassified ventricular event and reclassifying the ventricular event to a negligible ventricular event, to, for example, optimize pacing delivered to a patient depending on the patient’s needs. For example, LBB and / or RBB pacing may be delivered to a patient, and additionally ventricular sense response (VSR) or non- VSR modes may be enabled for either of LBB and RBB pacing. For example, if a cardiac event classified as a ventricular event is sensed within a time window after an atrial event, the cardiac event may be reclassified as a negligible ventricular event.

[0008] A cardiac event may be any sensed or paced event in any chamber of the heart, and additionally a cardiac event may be any monitored electrical activity from the heart indicative of an event (e.g., an atrial sensed or paced event, a ventricular sensed or paced event, a premature ventricular contraction, an arrhythmic heartbeat, etc.). A negligible ventricular event may refer to any cardiac event that is not a true or physiologic event (e.g., not a representative or standard ventricular event). A negligible ventricular event may occur as a result of noise or potential oversensing of electrical activity.

[0009] The reclassification of the cardiac event may be useful in non-VSR pacing to avoid skipping a paced ventricular event at the expiration of an atrioventricular (AV) delay or may be useful in VSR pacing to avoid unnecessary and early ventricular pacing. More particularly, the cardiac event may be reclassified as at least one of an over-sensed atrial depolarization, an arrhythmia beat, a PVC, etc., which, for example, may advantageously provide a more accurate assessment of cardiac events and optimized pacing therapy. For instance, for patients with misclassified ventricular events, reclassification of the event from a ventricular event to a negligible ventricular event (e.g., an over-sensed atrial depolarization, etc.) may help to coordinate heart chamber contractions and provide optimized pacing therapy to the patient.

[0010] Additionally, misclassified ventricular events may occur as a result of the lead(s) beginning to sense negligible ventricular events due to dislodgment of the lead(s) from their original implantation location. It can be difficult to implant a lead close enoughto the LBB or RBB to effectively pace the LBB or RBB, or implanted lead(s) may dislodge over time due to natural movement or due to injury, for example, and misclassified ventricular events may occur as a result of the lead(s) sensing negligible ventricular events. Use of different pacing therapies and modes may affect how events are determined and when, which can also give rise to misclassified ventricular events. Pacing therapies and modes may be chosen based on the individual patient’s needs, and correct classification of cardiac events is important to optimize those pacing therapies and modes.

[0011] Additionally, continuously sensing cardiac events during the time window immediately following an atrial event (e.g., an atrial pace or an intrinsic atrial activation) may be advantageous compared to, e.g., blanking or purposefully not sensing anything during the time window. Further, it may be described that continuous sensing may advantageously allow for proper classification of cardiac events during the time window and may offer more in-depth information to patients and medical professionals.

[0012] In particular, illustrative devices and methods are described herein to determine a cardiac event classified as a ventricular event within a time window of a determined atrial event, and to further reclassify the determined cardiac event and provide effective pacing therapy in response thereto. Still further, electrical signal analysis may indicate, for example, LBB block, RBB block, atrioventricular (AV) block, normal intrinsic conduction, 1 : 1 cardiac rhythm, etc., based on the measured start of depolarization of the left and right atria and / or the left and right ventricles.

[0013] In some examples, the illustrative devices and methods described herein also perform the ventricular event reclassification during one of VSR or non-VSR modes. VSR may be described as a pacing mode that provides ventricular biventricular pacing or pacing from a conduction system lead based on ventricular sensing from one ventricle (e.g., ensuring that if one ventricle begins to depolarize, the other ventricle is paced to depolarize at the same time or close to the same time). Non-VSR may be described as any other pacing mode. If VSR is enabled and a cardiac event classified as a ventricular event is determined within the time window and is reclassified as a negligible ventricular event, the automatic mono- or biventricular pacing pulse is inhibited.

[0014] Additionally, in either VSR or non-VSR modes, a set AV delay may be programmed as part of the delivered cardiac therapy. If the AV delay expires, a ventricular pacing pulse may be delivered. If a ventricular event is determined (e.g.,sensed) before the AV delay expires, and if VSR mode is enabled, a ventricular pacing pulse may be delivered. If a ventricular event is determined before the AV delay expires, and if VSR mode is not enabled, then no ventricular pacing pulse may be delivered upon expiration of the AV delay.

[0015] In embodiments where VSR mode is enabled, misclassification of cardiac events as ventricular events may result in ventricular paces being automatically delivered based on the misclassified cardiac event, which in turn may result in non-synchronous ventricular depolarizations. In embodiments where VSR mode is not enabled, misclassification of cardiac events as ventricular events may result in loss of synchronized pacing therapy. Proper classification of cardiac events (either with VSR mode enabled or not enabled) may advantageously avoid non-synchronous ventricular depolarizations and / or loss of synchronized pacing therapy.

[0016] In one embodiment, an implantable medical device (IMD) can include at least one electrode configured to be disposed proximate a patient’s heart to sense cardiac electrical activity of the patient’s heart and to deliver a pacing therapy to the patient’s heart. The IMD can include a computing apparatus including processing circuitry and operably coupled to the at least one electrode. The computing apparatus can be configured to monitor cardiac electrical activity using the at least one electrode. The computing apparatus can be further configured to determine an atrial event based on the monitored cardiac electrical activity. The computing apparatus can be further configured to determine a cardiac event classified as a ventricular event within a time window after the determined atrial event. The computing apparatus can be further configured to, in response to determination of the cardiac event classified as a ventricular event within the time window, reclassify the cardiac event as a negligible ventricular event.

[0017] In one embodiment, a method can include initiating delivery of a pacing therapy to a patient’s heart using at least one implantable electrode configured to be disposed proximate the patient’s heart. The method can further include monitoring cardiac electrical activity using the at least one implantable electrode. The method can further include determining occurrence of an atrial event based on the monitored cardiac electrical activity. The method can further include determining occurrence of a cardiac event classified as a ventricular event within a time window after a determined atrial event occurrence. The method can further include, in response to determination of thecardiac event classified as a ventricular event within the time window, reclassifying the cardiac event as a negligible ventricular event.

[0018] In one embodiment, an implantable medical device (IMD) can include at least one electrode configured to be disposed proximate a patient’s heart to sense cardiac electrical activity of the patient’s heart and to deliver a pacing therapy to the patient’s heart. The IMD can include a computing apparatus including processing circuitry and operably coupled to the at least one electrode. The computing apparatus can be configured to monitor cardiac electrical activity using the at least one electrode. The computing apparatus can be further configured to determine an atrial event based on the monitored cardiac electrical activity. The computing apparatus can be further configured to determine a cardiac event classified as a ventricular event within a time window after the determined atrial event. The computing apparatus can be further configured to determine a pacing interval is below a threshold. The computing apparatus can be further configured to, in response to determination of the cardiac event classified as a ventricular event within the time window and determination of the pacing interval below the threshold, inhibit delivery of a ventricular sensing response (VSR) pacing pulse when VSR is enabled, and initiate delivery of a pacing pulse to the patient’s heart using the at least one electrode when an AV delay expires when VSR or non-VSR is enabled.

[0019] The above summary is not intended to describe each embodiment or every implementation of the present disclosure. A more complete understanding will become apparent and appreciated by referring to the following detailed description and claims taken in conjunction with the accompanying drawings.

[0020]

[0021] BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. l is a schematic diagram of a heart and conduction system of a patient.

[0023] FIG. 2A is a conceptual diagram of an illustrative therapy system that is configured to provide cardiac conduction system pacing therapy to the left and / or right bundle branches using a lead placed in the right ventricle.

[0024] FIG. 2B is a detailed conceptual diagram showing the illustrative therapy system of FIG. 2 A but only including two leads.

[0025] FIG. 3 A is a conceptual diagram illustrating an illustrative therapy system that is configured to provide cardiac conduction system pacing therapy to the left bundle branch using a single lead placed in the right ventricle.

[0026] FIG. 3B is a close-up view of the lead in the patient’s heart of FIG. 2 A.

[0027] FIG. 4 is a functional block diagram illustrating an example of a configuration of an implantable medical device of FIGS. 2A-3B.

[0028] FIG. 5 is a block diagram of an illustrative method of ventricular event reclassification based on monitored electrical activity that may be utilized by the devices of FIGS. 2-3, and optionally pacing the heart using VSR pacing or non- VSR pacing.

[0029] DETAILED DESCRIPTION

[0030] In the following detailed description of illustrative embodiments, reference is made to the accompanying figures of the drawing which form a part hereof, and in which are shown, by way of illustration, specific embodiments which may be practiced. It is to be understood that other embodiments may be utilized, and structural changes may be made without departing from (e.g., still falling within) the scope of the disclosure presented hereby.

[0031] Illustrative devices and methods shall be described with reference to FIGS. 1- 5. It will be apparent to one skilled in the art that elements or processes from one embodiment may be used in combination with elements or processes of the other embodiments, and that the possible embodiments of such devices and methods using combinations of features set forth herein is not limited to the specific embodiments shown in the Figures and / or described herein. Further, it will be recognized that the embodiments described herein may include many elements that are not necessarily shown to scale. Still further, it will be recognized that timing of the processes and the size and shape of various elements herein may be modified but still fall within the scope of the present disclosure, although certain timings, one or more shapes and / or sizes, or types of elements, may be advantageous over others.

[0032] FIG. 1 depicts a schematic diagram of a heart 12 and FIGS. 2-3 depict conceptual diagrams showing illustrative therapy systems that may be used to provide therapy to the heart of a patient. In particular, the systems shown in FIGS. 1-3 areconfigured to deliver cardiac conduction system pacing, and more specifically, one or both of left bundle branch pacing and right bundle branch pacing. Although cardiac conduction system pacing systems are depicted, it is to be understood that the illustrative functionality, methods, and processes associated with reclassifying a cardiac event as a negligible ventricular event may be executed, performed, or used by cardiac therapy systems that do not provide cardiac conduction system pacing such as, for example, traditional myocardial pacing systems and such traditional myocardial pacing systems used in combination with cardiac conduction system pacing systems. In one or more embodiments, the cardiac therapy by the systems of FIGS. 1-3 may include cardiac resynchronization therapy.

[0033] As shown, the therapy may be delivered to the cardiac conduction system (e.g., left bundle branch pacing lead, right bundle branch pacing lead, His-bundle pacing lead, etc.) and / or may be delivered to other areas of the heart. The patient ordinarily, but not necessarily, will be a human. As shown in FIGS. 2A-2B, the therapy system 10 may include IMD 16, which is coupled to three leads 18, 20, 23, and a programmer 24. The lead 18 may include a cardiac conduction system pacing therapy lead 18. The IMD 16 may be, for example, an implantable pacemaker, cardioverter, and / or defibrillator that provides electrical pulses to the heart via electrodes coupled to one or more of the leads 18, 20, 23. Further non-limiting examples of the IMD 16 include the following: a pacemaker with a medical lead, an implantable cardioverter-defibrillator (ICD), an intracardiac device, a leadless pacing device (LPD), a subcutaneous ICD (S-ICD), and a subcutaneous medical device (e.g., nerve stimulator, inserted monitoring device, etc.).

[0034] The leads 18, 20, 23 may extend into the heart of the patient to sense electrical activity of the heart and / or deliver electrical stimulation to the heart. In the example shown in FIG. 2A, the right atrial (RA) lead 23 extends through one or more veins (not shown), the superior vena cava (not shown), and into the RA 26. The RA lead 23 may be positioned for positioning electrodes 40, 42 near, adjacent, on, within, or around the RA for sensing electrocardiogram signals and pacing the right atrial myocardium. The RA lead 23 is shown with a ring electrode 40 and a helix tip electrode 42 that may be selected in various bipolar pacing electrode pairs for pacing the right atrial myocardial tissue and for sensing right atrial epicardial electrocardiogram signals. One of the electrodes 40, 42 may be selected in combination with IMD housing 60 or a coil electrode 62 for deliveringunipolar right atrial myocardial pacing and / or sensing unipolar atrial electrocardiogram signals.

[0035] The left ventricular coronary sinus lead 20 extends through one or more veins, the vena cava, the right atrium 26, and into the coronary sinus 30 to a region adjacent to the free wall of the LV 32. The left ventricular coronary sinus lead 20 may be positioned for positioning electrodes 94a, 94b, 94c, 94d (collectively “94”) epicardially along the left ventricular myocardium for sensing electrocardiogram signals and pacing the left ventricular myocardium. The left ventricular coronary sinus lead 20 is shown as a quadripolar lead carrying four electrodes 94a-94d that may be selected in various bipolar pacing electrode pairs for pacing the left ventricular myocardial tissue and for sensing left ventricular epicardial electrocardiogram signals. One of the electrodes 94 may be selected in combination with IMD housing 60 or a coil electrode 64 for delivering unipolar left ventricular myocardial pacing and / or sensing unipolar ventricular electrocardiogram signals.

[0036] In one embodiment, the cardiac conduction system pacing therapy lead 18 (e.g., left bundle branch pacing lead, right bundle branch pacing lead, His-bundle pacing lead, etc.) extends through one or more veins and the vena cava, the RA 26, through the tricuspid valve and into the RV 28 of the heart to pace the cardiac conduction system (e.g., within the ventricular septal wall, proximate and / or in direct contact with the LBB 8a, proximate and / or in direct contact with the RBB 8b, proximate and / or in direct contact with the His bundle 13, etc.). In some embodiments, the cardiac conduction system pacing therapy lead 18 may be positioned within about 1 millimeter of a portion of the cardiac conduction system such as, e.g., the His bundle 13, the LBB 8a, the RBB 8b, etc. The cardiac conduction system pacing therapy lead 18 may be positioned for positioning electrodes 48, 50 near, adjacent, on, within, or around the RBB, LBB (respectively) for sensing electrocardiogram signals and pacing the cardiac conduction system. The cardiac conduction system pacing therapy lead 18 is shown with a ring electrode 48 and a helix tip electrode 50 that may be selected in various bipolar pacing electrode pairs for pacing the RBB and the LBB (respectively) and for sensing RBB and LBB electrocardiogram signals (respectively). One of the electrodes 48, 50 may be selected in combination with IMD housing 60 or a coil electrode (66) for delivering unipolar RBB and LBB pacing and / or sensing unipolar RBB and LBB electrocardiogram signals. In alternative embodiments, the cardiac conduction system pacing therapy lead 18 is also used to pacethe RA using an electrode 75 (shown in FIGS. 3 A-B) in addition to the cardiac conduction system, such as in a two lead configuration which does not include the RA lead 23.

[0037] One example of a cardiac conduction system pacing therapy lead (e.g., a His lead) can be the SELECTSECURE™ 3830. A description of the SELECT SECURE™ 3830 is found in the Medtronic model SELECTSECURE™ 3830 manual (2013), incorporated herein by reference in its entirety. The SELECTSECURE™ 3830 includes two conductors without lumens.

[0038] As used herein, cardiac conduction system pacing therapy refers to any techniques that are configured to deliver pacing therapy (e.g., pacing pulses, electrical stimulation, etc.) to the cardiac conduction system including, e.g., the His bundle 13, the LBB 8a, the RBB 8b, etc., in order to initiate activation. As used herein, the term “activation” refers to a sensed or paced event. For example, an atrial activation may refer to an atrial sense or event (As) or an atrial pace or artifact of atrial pacing (Ap). As will be described herein, an atrial sense may be detected, or identified, in one or more various signals monitored using one or more various devices or sensors located in one or more various locations. For example, an atrial sense may be detected in a near-field electrical signal using an electrode positioned in the right atrium with a respective reference electrode (e.g., an electrode on the housing of the implantable medical device). Further, for example, an atrial sense may be detected in a far-field electrical signal using electrodes positioned outside of the right atrium such as in the right ventricle or ventricular septum and a respective reference electrode. Still, for example, an atrial sense may be detected in a far-field signal using a mechanical cardiac activation sensor such as an accelerometer or microphone (e.g., a heart sound sensor) positioned outside of the right atrium such as in the right ventricle or ventricular septum or another portion of the patient’s body (e.g., within the can or housing of an IMD positioned outside of the patient’s heart). Similarly, a ventricular activation may refer to a ventricular sense or event (Vs) or a ventricular pace or artifact of ventricular pacing (Vp), which may be described as ventricular stimulation pulses. Atrial and ventricular activations (sensed and paced) may be understood as cardiac events. In some embodiments, an atrio-ventricular (AV) interval can be detected from As or Ap to Vs or Vp, as well as Vp to Vs.

[0039] Illustrative IMDs may be described as delivering cardiac conduction system pacing therapy, and additionally may also deliver conventional pacing therapy.Conventional, or traditional, pacing therapy may be described as delivering pacing pulses into myocardial tissue that is not part of the cardiac conduction system of the patient’s heart such that, e.g., the pacing pulses trigger electrical activation that propagates primarily from one myocardial cell to another myocardial cell (also referred to as “cell-to- cell”) as opposed to propagating within the cardiac conduction system prior to the myocardial tissue. For instance, conventional pacing therapy may deliver pacing pulses directly into the muscular heart tissue (e.g., myocardial tissue) that is to be depolarized to provide the contraction of the heart. For example, conventional left ventricular pacing therapy may utilize a left ventricular coronary sinus lead 20 that is implanted so as to extend through one or more veins, the vena cava, the right atrium 26, and into the coronary sinus 30 to a region adjacent to the free wall of the left ventricle 32 of the heart so as to deliver pacing pulses to the myocardial tissue of the free wall of the left ventricle 32.

[0040] An illustrative left ventricular lead 20 with a set of spaced apart electrodes is shown in PCT Pat. Pub. No. WO 2019 / 104174 Al, filed on November 21, 2018, by Ghosh et al., which is incorporated by reference in its entirety herein. Illustrative electrodes on leads to form pacing vectors are shown and described in U.S. Pat. No. 8,355,784 B2, and U.S. Pat. No. 8,126,546, each of which are incorporated by reference in their entireties.

[0041] Additionally, the pacing therapy leads 18, 20, 23 may be utilized to deliver left ventricle or left ventricular septal pacing to the ventricular septal wall. At least one of pacing therapy leads 18, 20, 23 may extend through one or more veins, the vena cava, right atrium 26, and into the coronary sinus 30 to a region adjacent to the septal wall of left ventricle 32 of the heart.

[0042] Illustrative cardiac conduction system pacing therapy may be described in, for example, U.S. Pat. App. Pub. No. 2019 / 0111270 Al entitled “His Bundle and Bundle Branch Pacing Adjustment” published on April 18, 2019, which is incorporated herein by reference in its entirety. Illustrative left ventricular septal pacing may be described in, for example, U.S. Pat. No. 11,633,607 entitled “AV Synchronous Septal Pacing” filed on July 24, 2019, which is incorporated herein by reference in its entirety.

[0043] One or more elongated conductors of any of the leads 18, 20, 23 may extend through a hermetic feedthrough assembly, and within an insulative tubular member of therespective lead, and may electrically couple an electrical pulse generator (contained within housing) to one or more electrodes such as, e.g., ring electrodes, tips electrodes, helical electrodes, etc. The conductors may be formed by one or more electrically conductive wires comprising, for example, MP35N alloy known to those skilled in the art, in a coiled or cabled configuration, and the insulative tubular member may be any suitable medical grade polymer, for example, polyurethane, silicone rubber, or a blend thereof. According to one or more illustrative embodiments, the flexible lead body may extend a pre-specified length (e.g., about 10 centimeters (cm) to about 20 cm, or about 15 to 20 cm) from a proximal end to a distal end. The lead body may be less than about 7 French (FR) but typically in the range of about 3 FR to 4 FR in size. In one or more embodiments, about 2 FR size to about 3 FR size lead body is employed.

[0044] Cardiac conduction system pacing may include at least one of His bundle pacing, LBB pacing, and RBB pacing. Bundle branch pacing may bypass the pathological region and may have a low and stable pacing threshold. In some embodiments, only one of the LBB or the RBB may be paced using one or more pacing leads. In further embodiments, both bundle branches may be paced at the same time (e.g., dual bundle branch pacing), which may mimic intrinsic activation propagation via the His bundle- Purkinje conduction system, e.g., paced activation propagates via both bundle branches to both ventricles for synchronized contraction. His bundle pacing, on the other hand, typically paces the His bundle proximal to the bundle branches. In some embodiments, the IMD 16 may be coupled to one, two, or more electrodes located in one or more bundle branches configured for bundle branch pacing.

[0045] In some embodiments, the IMD 16 may be an intracardiac pacemaker or leadless pacing device (LPD) configured to pace one or more portions of the cardiac conduction system such as one or both of the bundle branches. As used herein, “leadless” refers to a device being free of a lead extending out of the heart 12. In other words, a leadless device may have a lead that does not extend from outside of the heart to inside of the heart. Some leadless devices may be introduced through a vein, but once implanted, the leadless devices are free of, or may not include, any transvenous lead and may be configured to provide cardiac therapy without using any transvenous lead. In one or more embodiments, an illustrative LPD for bundle pacing does not use a lead to operably connect to an electrode disposed proximate to the septum when a housing of the device ispositioned in the atrium. A leadless electrode may be leadlessly coupled to the housing of the medical device without using a lead between the electrode and the housing.

[0046] The IMD 16 may sense electrical signals attendant to the depolarization and repolarization of the heart via various electrodes as shown in FIG. 2A coupled to at least one of leads 18, 20, 23. In some examples, the IMD 16 provides pacing pulses to the heart based on the electrical signals sensed within the heart. The configurations of the electrodes used by the IMD 16 for sensing and pacing may be unipolar or bipolar.

[0047] The IMD 16 may also provide defibrillation therapy and / or cardioversion therapy via electrodes located on at least one of the leads 18, 20, 23. For example, the IMD 16 may detect atrial arrhythmias of heart, such as atrial fibrillation of the atria 26, 33, and then may deliver defibrillation therapy to the heart in the form of electrical pulses. Also, the IMD 16 may detect ventricular arrhythmias of the heart, such as ventricular fibrillation of the ventricles 28, 32, and then may deliver defibrillation therapy to the heart in the form of electrical pulses. In some examples, the IMD 16 may be programmed to deliver a progression of therapies, e.g., pulses with increasing energy levels, until fibrillation of the heart is stopped. The IMD 16 may detect fibrillation employing one or more fibrillation detection techniques known in the art.

[0048] In some examples, the programmer 24 as shown in FIGS. 2A-B may be a handheld computing device or a computer workstation or a mobile phone. The programmer 24 may include a user interface that receives input from a user. The user interface may include, for example, a keypad and a display, which may for example, be a cathode ray tube display, a liquid crystal display (LCD) or light emitting diode (LED) display. The keypad may take the form of an alphanumeric keypad, or a reduced set of keys associated with particular functions. The programmer 24 can additionally or alternatively include a peripheral pointing device, such as a mouse, via which a user may interact with the user interface. In some embodiments, a display of the programmer 24 may include a touch screen display, and a user may interact with the programmer 24 via the display. Through the graphical user interface on the programmer 24, a user may configure one or more pacing therapies, select one or more pacing modes, etc.

[0049] Additionally, various pacing settings may be adjusted, or configured, based on various sensed signals. For example, various near-field and far-field signals may be sensed by one or more of the electrodes coupled to the IMD 16 and / or other devicesoperatively coupled thereto. For example, right ventricular depolarization and left ventricular depolarization intervals may be monitored or measured within a near-field or far-field signal and then may be used to adjust, configure, and select cardiac conduction system pacing therapy. Further, for example, QRS morphology (e.g., QRS peak, various QRS intervals) may be monitored or measured within a near-field or far-field signal and then may be used to adjust, configure, and select cardiac conduction system pacing therapy. Still further, for example, one or more of right ventricular depolarization and left ventricular depolarization interval consistency, and QRS morphology consistency may be monitored or measured within a near-field or far-field signal and then may be used to adjust, configure, and select cardiac conduction system pacing therapy. Misclassification of cardiac events (e.g., classifying a far-field atrial event as a near-field ventricular event as described herein) may lead to non-optimal pacing of the patient’s heart (e.g., if VSR is enabled then an automatic ventricular pulse may be generated at the wrong time based on a misclassified cardiac event). Thus, accurate cardiac event classification may result in optimal pacing of the patient’s heart.

[0050] The illustrative therapy systems described herein such as IMD 16 may be utilized to deliver cardiac conduction system pacing therapy according to a variety of different modes such as, e.g., cardiac resynchronization therapy mode, inhibited pacing mode, ventricular fusion pacing mode, atrioventricular synchronous pacing mode, atrial fibrillation pacing mode, etc.

[0051] The ventricular fusion pacing mode may be configured to deliver cardiac conduction system pacing therapy to provide effective ventricular fusion. Effective ventricular fusion may be described as synchronizing the timing of the left ventricular activation with the activation on the right ventricle. For example, in a fusion pacing configuration, a medical device may deliver one or more pacing pulses in order to pre-excite the left ventricle and synchronize the depolarization of the left ventricle with the depolarization of the earlier contracting right ventricle. The ventricular activation of the left ventricle may “fuse” (or “merge”) with the ventricular activation of the right ventricle that is attributable to intrinsic conduction of the heart. In this way, the intrinsic and pacing-induced excitation wave fronts may fuse together such that the depolarization of the left ventricle is resynchronized with the depolarization of the right ventricle. Further, for example, VSR mode may be enabled. With VSR enabled, biventricular pacing may be provided based on ventricular sensing from one ventricle(e.g., ensuring that if one ventricle begins to depolarize and that is sensed, the other ventricle is then paced to depolarize at the same time or close to the same time).

[0052] As used herein, the term “far-field” electrical signal refers to the result of measuring cardiac activity using a sensor, such as an electrode, positioned outside of an area of interest. For example, a far-field electrical signal representing electrical activity of a chamber of interest of the patient’s heart may be measured from an electrode positioned in an adjacent chamber (i.e., a chamber different from than that of the chamber of interest that is next to or near the chamber of interest). More specifically, for example, atrial electrical activity, or electrical activity originating one or more both atria, representative of depolarization of the one or both atria may be monitored in a far-field electrical signal measured using an electrode positioned outside of the right atrium such as in the right or left ventricle, or in the ventricular septum. As used herein, the term “near-field” electrical signal refers to the result of measuring cardiac activity using a sensor, such as an electrode, positioned near an area of interest. For example, an electrical signal measured using an electrode positioned on the left side of the patient’s ventricular septum is one example of a near-field electrical signal of the patient’s LV.

[0053] P-wave timing is the time at which a P-wave, which is an atrial event, is detected. Typically, P-wave timing includes using the maximal first derivative of a P- wave upstroke (or the time of the maximal P-wave value). P-wave timing is also used in the device marker channel to indicate the time of the P-wave or the time of atrial activation. P-wave timing may be determined using near-field signals obtained by sensors (e.g., electrodes, accelerometers, heart sound sensors, etc.) positioned in the atria (e.g., the right atrium) and / or far-field near-field signals obtained by sensors (e.g., electrodes, accelerometers, heart sound sensors, etc.) positioned outside of the atria (e.g., the right atrium) such as in the right ventricle and / or ventricular septum.

[0054] R-wave timing is the time at which the QRS complex, which is a ventricular event, is detected. Typically, R-wave timing includes using the maximal first derivative of an R-wave upstroke (or the time of the maximal R-wave value). R-wave timing is also used in the device marker channel to indicate the time of the R-wave or the time of ventricular activation.

[0055] A user, such as a physician, technician, or other clinician, may interact with the programmer 24 to communicate with the IMD 16. For example, the user may interactwith the programmer 24 to retrieve physiological or diagnostic information from the IMD 16. Additionally, a user may also interact with the programmer 24 to program the IMD 16, e.g., select values for operational parameters of the IMD 16. The IMD 16 and programmer 24 may communicate via wireless communication using any techniques known in the art. Examples of communication techniques may include, for example, low frequency or radiofrequency (RF) telemetry, but other techniques are also contemplated. In some examples, the programmer 24 may include a programming head that may be placed proximate to the patient’s body near the IMD 16 implant site in order to improve the quality or security of communication between the IMD 16 and the programmer 24.

[0056] The three chamber IMD 16 may be used for cardiac resynchronization therapy and defibrillation or cardioversion therapy (CRT-D). The leads 18, 20, 23 may be electrically coupled to a stimulation generator, a sensing module, or other modules of IMD 16 via connector block 34. In some examples, proximal ends of leads 18, 20, 23 may include electrical contacts that electrically couple to respective electrical contacts within the connector block 34. In addition, in some examples, the leads 18, 20, 23 may be mechanically coupled to the connector block 34 with the aid of set screws, connection pins, or another suitable mechanical coupling mechanism.

[0057] While the cardiac conduction system pacing therapy lead 18 is shown and described with respect to FIGS. 2A, 2B, 3A, and 3B as being placed in the RV along the intraventricular septal wall, in other examples, the cardiac conduction system pacing therapy lead 18 may be placed in the right atrium within the triangle of Koch region (not shown) with the corresponding electrodes 48, 50 tunneled through the septal tissue to be positioned proximate the RBB and LBB, respectively. In such examples, the system may not contain a lead positioned within the RV, yet still obtain the benefit of LBB or RBB pacing and sensing as described herein. Additionally or alternatively, the system in such examples may include an additional lead or electrode(s) (e.g., RA lead 23 or electrode(s) 40, 42) positioned in the RA configured to pace the RA that may be different from the cardiac conduction system pacing therapy lead 18 or the respective LBB and RBB electrodes.

[0058] Each of the leads 18, 20, 23 includes an elongated, insulative lead body, which may carry any number of conductors. In the illustrated example, an optional pressure sensor 38 and bipolar electrodes 48 and 50 are located proximate to a distal end of the cardiac conduction system pacing therapy lead 18. The pressure sensor 38 may respond toan absolute pressure inside RV, or may be positioned within other regions of the heart or elsewhere within or proximate to the cardiovascular system of the patient to monitor cardiovascular pressure associated with mechanical contraction of the heart. In addition, in some examples, the pressure sensor 38 may be self-contained device that is implanted within the heart and wirelessly correspond with the IMD 16. In addition, the bipolar electrodes 94a-94d (collectively referred to as reference number 94) are located proximate to a distal end of the left ventricular lead 20 and bipolar electrodes 40 and 42 are located proximate to a distal end of RA lead 23. The electrodes 48, 50 may be used for pacing and / or sensing of the cardiac conduction system tissue (e.g., His bundle or bundle branch tissue).

[0059] The electrodes 40, 94a-c and 48 may take the form of ring electrodes, and the electrodes 42, 94d and 50 may take the form of extendable and / or fixed helix tip electrodes mounted within the insulative electrode heads 52, 54 and 56, respectively. Each of the electrodes 40, 42, 94, 48 and 50 may be electrically coupled to a respective one of the coiled conductors within the lead body of its associated lead 23, 20, 18, and thereby coupled to respective ones of the electrical contacts on the proximal end of the leads 23, 20, 18.

[0060] The electrodes 40, 42, 94, 48 and 50 may sense electrical signals attendant to the depolarization and repolarization of the heart. The electrical signals are conducted to the IMD 16 via the respective leads 23, 20, 18. In some examples, the IMD 16 also delivers pacing pulses via the electrodes 40, 42, 94, 48, 50 to cause depolarization of cardiac tissue of heart. In some examples, as illustrated in FIG. 2A, the IMD 16 may include one or more housing electrodes, such as housing electrode 58, which may be formed integrally with an outer surface of a hermetically sealed housing 60 of the IMD 16 or otherwise coupled to the housing 60. In some examples, the housing electrode 58 may be defined by an uninsulated portion of an outward facing portion of the housing 60 of the IMD 16. Other divisions between insulated and uninsulated portions of housing 60 may be employed to define two or more housing electrodes. In some examples, the housing electrode 58 includes substantially all of the housing 60. Any of the electrodes 40, 42, 94, 48, 50 may be used for unipolar sensing or pacing in combination with the housing electrode 58 or for bipolar sensing with two electrodes in the same pacing lead. In one or more embodiments, the housing 60 may enclose a stimulation generator (see FIG. 4) thatgenerates cardiac pacing pulses and defibrillation or cardioversion shocks, as well as a sensing module for monitoring the patient’s heart rhythm.

[0061] The leads 23, 20, 18 may also include elongated electrodes 62, 64, 66, respectively (shown in FIG. 2 A), which may take the form of a coil. The IMD 16 may deliver defibrillation shocks to the heart via any combination of the elongated electrodes 62, 64, 66, and the housing electrode 58. The electrodes 58, 62, 64, 66 may also be used to deliver cardioversion pulses to the heart. The electrodes 62, 64, 66 may be fabricated from any suitable electrically conductive material, such as, but not limited to, platinum, platinum alloy or other materials known to be usable in implantable defibrillation electrodes.

[0062] The elongated electrodes may be selected in a unipolar electrode vector with any of the lead-based tip or ring electrodes for sensing unipolar electrocardiogram signals for analysis and determination of ventricular conduction conditions. In some instances, the elongated electrodes may be used with the housing 60 for sensing a far-field electrocardiogram signal for use in determining atrial depolarizations or activations, etc. The pressure sensor 38 may be coupled to one or more coiled conductors within the lead 18.

[0063] FIGS. 2B-3B are conceptual diagrams illustrating additional examples of a dual chamber therapy system 70 and a single chamber therapy system 71. The therapy system 70 is similar to therapy system 10 of FIG. 2A, but includes two leads 18, 23, rather than three leads. The therapy system 70 may utilize the IMD 16 configured to deliver, or perform, dual chamber pacing. The leads 18, 23 are implanted within the RV and the RA to pace one or more portions of the cardiac conduction system such as the His bundle or one or both bundle branches, and to pace the RA, respectively. The therapy system 71 is similar to therapy system 10 of FIG. 2A, but includes a single cardiac conduction system pacing lead 18, rather than three leads. The therapy system 71 may utilize the IMD 16 configured to deliver, or perform, single chamber pacing. The cardiac conduction system pacing lead 18 is implanted the RV to pace one or more portions of the cardiac conduction system such as one or both bundle branches.

[0064] The cardiac conduction system pacing lead 18 may be include an electrode 50 in the form of a helix (also referred to as a helical electrode) that may be positioned proximate to, near, adjacent to, or in, area or portions of the cardiac conduction systemsuch as, e.g., ventricular septum, triangle of Koch, the His bundle, left bundle branch tissues, and / or right bundle branch tissue. The cardiac conduction system pacing lead 18 may be configured as a bipolar lead that may be used with a pacemaker device, a CRT-P device, or a CRT-ICD.

[0065] FIGS. 3A-3B show the patient’s heart implanted with cardiac conduction system pacing lead 18 to deliver bundle branch pacing according to one example of the single chamber therapy system 71. The cardiac conduction system therapy lead 18 is positioned, or located, through the tricuspid valve into the RV and implanted in the interventricular septum, e.g., about 1 to 2 centimeters in an apical direction away from the RA (as illustrated in FIGS. 2A-B). FIG. 3B is a close-up view of the cardiac conduction system therapy lead 18 in the patient’s heart of FIG. 3 A. In some embodiments, the cardiac conduction system therapy lead 18 may be the only lead implanted in the heart. In other embodiments as discussed herein, there may be leads in addition to the cardiac conduction system therapy lead 18 implanted in the heart. The one or more implantable electrodes of the cardiac conduction system therapy lead 18 may include a pacing electrode implantable proximate the cardiac conduction system to deliver cardiac conduction system pacing therapy.

[0066] As illustrated, the cardiac conduction system pacing therapy lead 18 is implanted in the septal wall, or ventricular septum, from the RV toward the LV. The cardiac conduction system pacing therapy lead 18 may not pierce through the wall of the LV or extend into the LV chamber. The electrodes 48 and 50 may be disposed on a distal end portion of the cardiac conduction system pacing therapy lead 18 as discussed herein at least with respect to FIG. 2A. The cardiac conduction system pacing therapy lead 18 may also be described as a shaft. The electrodes 48 and 50 may be the same as or similar to electrode 48 and electrode 50 shown in FIG. 2A and the electrode 48 is configured to sense or pace the right bundle branch and the electrode 50 is configured to sense or pace the left bundle branch, for example, during dual bundle branch pacing. Accordingly, the electrode 48 may be implanted near right bundle branch 8b, and the electrode 50 may be implanted near the left bundle branch 8a. The electrode 50 may be implanted towards the left side of the patient’s ventricular septum. The electrode 48 may be implanted towards the right side of the patient’s ventricular septum. In one embodiment, the electrode 50 may be a helix electrode, and the electrode 48 may be a ring electrode.

[0067] During dual bundle branch pacing, both the electrodes 48 and 50 may each deliver a pulse to achieve synchronized activation, or excitation, of the RBB 8b and the LBB 8a, which may result in synchronized activation of the RV and the LV. In some embodiments, the pulses may be delivered at the same time to achieve synchrony. In other embodiments, the pulses may be delivered with a delay to achieve synchrony.

[0068] Although the cardiac conduction system pacing therapy lead 18 as shown in configured for dual bundle branch pacing using the electrodes 48, 50, it is to be understood that the cardiac conduction system pacing therapy lead 18 or leads similar thereto are considered herein that may only include one of the electrode 48 and the electrode 50, and thus, only configured to deliver cardiac conduction system pacing therapy to one of the right bundle branch and the left bundle branch. In alternative embodiments, both electrodes 48 and 50 may be located on the cardiac conduction system pacing therapy lead 18, but the IMD 16 may use just one of electrodes 48, 50 to pace only one bundle branch.

[0069] Additionally, the cardiac conduction system pacing therapy lead 18 may include an RA electrode 75 disposed more proximal to the electrodes 48, 50 along the cardiac conduction system pacing therapy lead 18. The RA electrode 75 may be positioned in or near the RA and may function as an anode for cathodal pulses from the electrode 48 and / or the electrode 50. Further, the RA electrode 75 may provide atrial sensing to, e.g., sense atrial depolarizations or activations, to sense or detect atrial fibrillation, etc. Although the cardiac conduction system pacing therapy lead 18 as shown includes the RA electrode 75, it is to be understood that the cardiac conduction system pacing therapy lead 18 may not include the RA electrode 75, and instead, only include one or both of the electrode 48 and the electrode 50.

[0070] When the cardiac conduction system pacing therapy lead 18 is positioned for delivering bundle branch pacing, of one or both bundle branches, cardiac conduction system pacing therapy may be combined with traditional ventricular myocardial pacing of the left ventricle using the coronary sinus lead 20 to correct a left ventricular conduction delay and achieve electrical and mechanical synchrony of the left and right ventricles. As such, in some examples, one or more processors, one or more processing circuits, or a computing apparatus of the IMD 16 may select a cardiac conduction system pacing therapy plus traditional left ventricular myocardial pacing therapy that includes, for example, single or bilateral bundle branch pacing, e.g., using the cardiac conductionsystem pacing therapy lead 18, combined with left ventricular myocardial pacing using the coronary sinus lead 20.

[0071] The configuration of therapy systems 10, 70, and 71 illustrated in FIGS. 2-3 are merely examples. In other examples, a therapy system may include epicardial leads and / or patch electrodes instead of or in addition to the transvenous leads 18, 20, 23 illustrated in FIGS. 2-3 or other configurations shown or described herein or incorporated by reference. Further, the IMD16 need not be implanted within patient. As such, it is to be understood that the illustrative therapy systems described herein may include any suitable number of leads coupled to IMD 16, and each of the leads may extend to any location within or proximate to the heart. For example, illustrative therapy systems may include three transvenous leads located as illustrated in FIG. 2A, a single transvenous lead located as illustrated in FIGS. 3 A-3B, or two transvenous leads located as illustrated in FIG. 2B.

[0072] FIG. 4 is a functional block diagram of one example configuration of the IMD 16. The IMD 16 of FIG. 4 may be substantially similar to the IMD 16. The IMD 16 includes a processor 80, a memory 82, a stimulation generator 84 (e.g., electrical pulse generator or signal generating circuit), a sensing module 86 (e.g., sensing circuit), a telemetry module 88, and a power source 90. One or more components of the IMD 16, such as the processor 80, may be contained within a housing of the IMD 16 (e.g., within a housing of a pacemaker). The telemetry module 88, the sensing module 86, or both the telemetry module 88 and the sensing module 86 may be included in a communication interface. The memory 82 includes computer-readable instructions that, when executed by the processor 80, cause the IMD 16 and the processor 80 to perform various functions attributed to the IMD 16 and the processor 80 herein. The memory 82 may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random-access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, or any other digital media.

[0073] The processor 80 may include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or integrated logic circuitry. In some examples, processor 80 may include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functions attributed to processor 80 herein may be embodied assoftware, firmware, hardware, or any combination thereof. The processor 80 controls the stimulation generator 84 to select a therapy mode (e.g., select one or more of a ventricular sense response (VSR) pacing mode, an inhibited pacing mode, ventricular fusion pacing mode, atrioventricular synchronous pacing mode, atrial fibrillation pacing mode, etc.) and deliver stimulation therapy to the heart according to the selected pacing mode, which may be stored in the memory 82, and various sensing (e.g., atrial depolarizations or activations, ventricular atrial depolarizations or activations, heartrate, P-wave-to-R-wave intervals, etc.). Specifically, the processor 80 may control the stimulation generator 84 to deliver electrical pulses with amplitudes, pulse widths, frequency, or electrode polarities specified by the selected one or more therapy programs and therapy modes.

[0074] The stimulation generator 84 may be electrically coupled to the electrodes 40, 42, 94, 48, 50, 75, 62, 64, and 66, e.g., via conductors of the respective lead 23, 20, 18 or, in the case of housing electrode 58, via an electrical conductor disposed within the housing 60 of the IMD 16. The stimulation generator 84 may be configured to generate and deliver electrical stimulation therapy to the heart. For example, the stimulation generator 84 may deliver defibrillation shocks to the heart via at least two of the electrodes 58, 62, 64, 66. The stimulation generator 84 may deliver pacing pulses via the ring electrodes 40, 94, 48 coupled to the leads 23, 20, 18, respectively, and / or the helical electrodes 42, 94, 50 of the leads 23, 20, or 18, respectively. In various embodiments, the cardiac conduction system pacing therapy can be delivered through the cardiac conduction system pacing lead 18 that is connected to an atrial, right ventricular, or left ventricular connection port of the connector block 34. In some examples, the stimulation generator 84 delivers pacing, cardioversion, or defibrillation stimulation in the form of electrical pulses. In other examples, the stimulation generator 84 may deliver one or more of these types of stimulation in the form of other signals, such as sine waves, square waves, or other substantially continuous time signals.

[0075] The stimulation generator 84 may include a switch module and the processor 80 may use the switch module to select, e.g., via a data / address bus, which of the available electrodes are used to deliver defibrillation shocks or pacing pulses. The switch module may include a switch array, switch matrix, multiplexer, or any other type of switching device suitable to selectively couple stimulation energy to selected electrodes.

[0076] The sensing module 86 monitors signals from at least one of the electrodes 40, 42, 94, 48, 50, 58, 75, 62, 64 or 66 in order to monitor electrical activity of the heart, e.g.,via electrical signals, such as electrocardiogram (ECG) signals and / or electrograms (EGMs). The sensing module 86 may also include a switch module to select which of the available electrodes are used to sense the heart activity. In some examples, the processor 80 may select the electrodes that function as sense electrodes via the switch module within the sensing module 86, e.g., by providing signals via a data / address bus. In some examples, the sensing module 86 includes one or more sensing channels, each of which may include an amplifier. In response to the signals from the processor 80, the switch module may couple the outputs from the selected electrodes to one of the sensing channels.

[0077] In some examples, one channel of the sensing module 86 may include an Il- wave amplifier that receives signals from the electrodes 94, which are used for pacing and sensing proximate to the LV of the heart. Another channel may include another R-wave amplifier that receives signals from the electrodes 48, 50, which are used for pacing and sensing in the RV of the heart. In some examples, the R-wave amplifiers may take the form of an automatic gain-controlled amplifier that provides an adjustable sensing threshold as a function of the measured R-wave amplitude of the heart rhythm.

[0078] In addition, in some examples, one channel of the sensing module 86 may include a P-wave amplifier that receives signals from electrodes the 40, 42, which are used for pacing and sensing in the RA of heart. In some examples, the P-wave amplifier may take the form of an automatic gain-controlled amplifier that provides an adjustable sensing threshold as a function of the measured P-wave amplitude of the heart rhythm. Examples of R-wave and P-wave amplifiers are described in U.S. Patent No. 5,117,824 to Keimel et al., which issued on June 2, 1992, and is entitled, “APPARATUS FOR MONITORING ELECTRICAL PHYSIOLOGIC SIGNALS,” and is incorporated herein by reference in its entirety. Other amplifiers may also be used. Furthermore, in some examples, one or more of the sensing channels of the sensing module 86 may be selectively coupled to the housing electrode 58, or the elongated electrodes 62, 64, or 66, with or instead of one or more of the electrodes 40, 42, 94, 48 or 50, e.g., for unipolar sensing of R-waves or P-waves in any of the chambers 26, 28, or 32 of the heart.However, for example, if an electrode (e.g., the electrode 50) on the lead 18 senses an atrial depolarization (e.g., a P-wave with or without a P-wave amplifier) or other cardiac activity, it may beneficial that the sensed atrial depolarization or other cardiac activity isnot misclassified as a ventricular event, which the illustrative methods and processes described herein may be configured to avoid.

[0079] In some examples, the sensing module 86 includes a channel that includes an amplifier with a relatively wider pass band than the R-wave or P-wave amplifiers or a high-resolution amplifier with relatively narrow-pass band for His bundle or bundle branch potential recording. Signals from the selected sensing electrodes that are selected for coupling to this wide-band amplifier may be provided to a multiplexer, and thereafter converted to multi-bit digital signals by an analog-to-digital converter for storage in the memory 82 as an electrogram (EGM). In some examples, the storage of such EGMs in the memory 82 may be under the control of a direct memory access circuit. The processor 80 may employ digital signal analysis techniques to characterize the digitized signals stored in memory 82 to detect and classify the patient’s heart rhythm from the electrical signals. The processor 80 may detect and classify the heart rhythm of the patient by employing any of the numerous signal processing methodologies known in the art.

[0080] If the IMD 16 is configured to generate and deliver pacing pulses to the heart, the processor 80 may include pacer timing and control module, which may be embodied as hardware, firmware, software, or any combination thereof. The pacer timing and control module may include a dedicated hardware circuit, such as an ASIC, separate from other the processor 80 components, such as a microprocessor, or a software module executed by a component of the processor 80, which may be a microprocessor or ASIC. The pacer timing and control module may include programmable counters which control the basic time intervals associated with DDD, VVI, DVI, VDD, AAI, DDI, DDDR, VVIR, DVIR, VDDR, AAIR, DDIR and other modes of single and dual chamber pacing. In the aforementioned pacing modes, “D” may indicate dual chamber, “V” may indicate a ventricle, “I” may indicate inhibited pacing (e.g., no pacing), and “A” may indicate an atrium. The first letter in the pacing mode may indicate the chamber that is paced, the second letter may indicate the chamber in which an electrical signal is sensed, and the third letter may indicate the chamber in which the response to sensing is provided.

[0081] Intervals defined by the pacer timing and control module may include atrial and ventricular pacing escape intervals, refractory periods during which sensed P-waves and R-waves are ineffective to restart timing of the escape intervals, and the pulse widths of the pacing pulses. As another example, the pace timing and control module may define a blanking time period and provide signals from sensing module 86 to blank one or morechannels, e.g., amplifiers, for a period during and after delivery of electrical stimulation to the heart. The durations of these intervals may be determined by the processor 80 in response to stored data in the memory 82. The pacer timing and control module may also determine the amplitude of the cardiac pacing pulses.

[0082] During pacing, escape interval counters within the pacer timing / control module may be reset upon sensing of R- waves and P-waves. The stimulation generator 84 may include pacer output circuits that are coupled, e.g., selectively by a switching module, to any combination of the electrodes 40, 42, 94, 48, 50, 58, 75, 62, 64, or 66 appropriate for delivery of a bipolar or unipolar pacing pulse to one of the chambers of the heart. The processor 80 may reset the escape interval counters upon the generation of pacing pulses by stimulation generator 84, and thereby control the basic timing of cardiac pacing functions, including anti-tachyarrhythmia pacing.

[0083] In some examples, the processor 80 may operate as an interrupt driven device and is responsive to interrupts from pacer timing and control module, where the interrupts may correspond to the occurrences of sensed P-waves and R-waves and the generation of cardiac pacing pulses. Any necessary mathematical calculations to be performed by the processor 80 and any updating of the values or intervals controlled by the pacer timing and control module of the processor 80 may take place following such interrupts. A portion of the memory 82 may be configured as a plurality of recirculating buffers, capable of holding series of measured intervals, which may be analyzed by the processor 80 in response to the occurrence of a pace or sense interrupt to determine whether the patient’s heart is presently exhibiting atrial or ventricular tachyarrhythmia.

[0084] The telemetry module 88 includes any suitable hardware, firmware, software, or any combination thereof for communicating with another device, such as the programmer 24. Under the control of the processor 80, the telemetry module 88 may receive downlink telemetry from and send uplink telemetry to the programmer 24 with the aid of an antenna, which may be internal and / or external. The processor 80 may provide the data to be uplinked to the programmer 24 and the control signals for the telemetry circuit within the telemetry module 88, e.g., via an address / data bus. In some examples, the telemetry module 88 may provide received data to the processor 80 via a multiplexer.

[0085] The various components of the IMD 16 are coupled to the power source 90, which may include a rechargeable or non-rechargeable battery. A non-rechargeable battery may be selected to last for several years, while a rechargeable battery may be inductively charged from an external device, e.g., on a daily or weekly basis.

[0086] The illustrative devices and methods described herein may provide and use monitored electrical activity (e.g., ECG, EGM, etc.) to determine various cardiac events and to provide effective pacing therapy for use in cardiac therapy such as, for example, cardiac resynchronization therapy (CRT), biventricular pacing, LBB pacing (with or without atrial pacing), LBB block mode pacing, RBB pacing, RBB block mode pacing, etc. Further, the monitored electrical activity may be used to determine a cardiac event classified as a ventricular event within a time window of a determined atrial event, and may reclassify the cardiac event as a negligible ventricular event. Still further, the monitored electrical activity may be used to determine whether an AV delay has expired or not, and may deliver a ventricular pace once the AV delay has expired. As discussed further herein, one of either VSR or non-VSR pacing modes may be enabled or utilized, and if VSR is enabled, a sensed response pace may be inhibited if the determined cardiac event is reclassified as a negligible ventricular event. Still further, when VSR is enabled, a ventricular pace may be delivered prior to the AV delay expiring in response to a ventricular event being sensed (that is not reclassified) after the time window and prior to the AV delay. Still further, when VSR is not enabled, a ventricular pace may not be delivered prior to the AV delay expiring in response to a ventricular event being sensed (that is not reclassified) after the time window and prior to the AV delay.

[0087] Additionally, many cardiac conduction system pacing therapy systems may not include electrodes positioned proximate the atria (e.g., the right atrium) so as to acquire and monitor near-field, or local, atrial electrical activity. For instance, cardiac conduction system pacing therapy systems may only include electrodes positioned outside of the right atrium. In at least one embodiment, cardiac conduction system pacing therapy systems may only include single chamber devices having electrodes implanted in the RV. As a result, such systems may utilize far-field electrical activity using one or more electrodes positioned outside of the right atrium of the patient’s heart. Such far-field electrical activity may be processed to determine the P-waves, which are indicative of atrial depolarization, so as to be used to time and deliver cardiac conduction system pacing therapy. However, it is important that such far-field electrical activity indicative ofatrial events is not misclassified as ventricular events. Misclassification may result in ventricular pacing pulses being delivered at non-optimal times (e.g., a ventricular pulse may be delivered too soon if an atrial event is misclassified as a ventricular event).

[0088] For example, the single chamber device may include a single lead extending through the right atrium into the RV as shown in FIGS. 3A-3B. The dual chamber device may include one or more leads or leadless devices. For example, the dual chamber device may include a first lead extending into the right atrium and a second lead extending into the RV as shown in FIG. 2B. The three-chamber device may include multiple leads or leadless devices. For example, the three-chamber device may include a first lead extending into the RV, a second lead extending into the coronary sinus to a region adjacent to the free wall of the LV, and a third lead extending into the right atrium, as shown in FIG. 2A.

[0089] An illustrative method 100 of determining a cardiac event classified as a ventricular event within a time window of a determined atrial event, and reclassifying such a determined cardiac event as a negligible ventricular event (and which method 100 may be utilized by the devices of FIGS. 2-3) is depicted in FIG. 5. The method 100 may include ongoing delivery of pacing therapy (not shown) as a preset for a patient. The ongoing delivery of the pacing therapy as a preset for a patient may also be understood as a standard device operation 108 (e.g., the standard device operation 108 may include the ongoing delivery of the pacing therapy as a preset for a patient). Standard device operation 108 may further include ongoing delivery of pacing therapy using VSR mode, or operating in non-VSR mode when VSR mode is not programmed or selected. When operating in non-VSR mode, a ventricular sensing event following an atrial event but occurring before the programmed AV pacing interval expires may result in the subsequent ventricular pacing not being delivered when the AV interval expires.

[0090] During the delivery of the therapy, electrical activity may be monitored using one or more of the electrodes as part of the pacing regimen. In particular, one or more of intrinsic atrial depolarizations or activations, paced atrial depolarizations or activations, intrinsic ventricular depolarizations or activations, and paced ventricular depolarizations or activations may be sensed in the monitored electrical activity so as to be used to detect various cardiac physiological conditions, to determine when to initiate delivery of a ventricular pacing pulse based on a set AV delay, to determine when to initiate deliveryof a ventricular pacing pulse based on a sensed atrial event and / or a sensed ventricular event, etc.

[0091] The method 100 may include monitoring electrical activity using one or more implantable electrodes 102. Monitoring electrical activity in the heart may include monitoring near-field and far-field electrical signals using the systems and devices as described above. Monitoring electrical activity may be accomplished using the sensing module 86, for example, as described herein. Electrical activity may include a near-field ECG or EGM signal as sensed from the at least one implanted electrode, and may further include a far-field ECG or EGM signal as sensed from the at least one implanted electrode. In one or more embodiments, electrical activity may be monitored in at least one of: the RV, the LV, and the ventricular septum (including the RBB and LBB) of the heart. The sensing module 86 or other sensing apparatus may monitor the electrical activity 102 (e.g., ECG, EGM signal).

[0092] In one embodiment, monitoring electrical activity 102 may include use of one or more implanted electrodes as discussed herein with respect to FIGS. 1-4, such as a ring electrode to a housing electrode unipolar EGM, a tip electrode to a housing electrode unipolar EGM, an RV coil electrode to a housing electrode unipolar EGM, and an atrial ring electrode to a housing electrode unipolar EGM. A tip electrode may be an electrode located on the tip of any lead as described above. A coil electrode may be an electrode shaped in or on a coil and located proximal to the tip of the lead along the lead body. A ring electrode may be an electrode shaped in a ring around the lead body and located proximal to the tip of the lead along the lead body. A housing electrode may be an electrode located in or about the housing of the IMD. Location identifiers such as RBB are examples of possible electrode locations. For example, the “atrial” location may be one of either atrium. In alternative embodiments, bipolar EGM signals may be monitored.

[0093] In one embodiment, and as described above, an RBB electrode (e.g., RBB ring to can unipolar implanted electrogram using electrode 48) may be used to monitor electrical activity of the right ventricle along the RBB. The RBB electrode may be used to produce an electrical signal, illustrating at least part of the monitored electrical activity of the method 100 of FIG. 5. An LBB electrode (e.g., LBB tip to can unipolar implanted electrogram using electrode 50) may be used to monitor electrical activity of the left ventricle along the LBB. The LBB electrode may be used to produce an electrical signal, illustrating at least part of the monitored electrical activity of the method 100 of FIG. 5. Inalternative embodiments, the monitored electrical activity can be based on, for example, the patient’s intrinsic cardiac electrical activity during a pause in pacing.

[0094] The method 100 may further include determining an atrial event (e.g., RA depolarization, LA depolarization, etc.) based on the monitored electrical activity 104. The determined atrial event can be based on the monitored electrical activity from the LBB electrode 50, for example. In alternative embodiments, the determined atrial event can be based on the monitored electrical activity from the RA electrode 75, from the RBB electrode 48, etc. Additionally, either the RBB electrode or the LBB electrode may sense far-field atrial events and misclassify such events as ventricular events. Reclassification of such events may advantageously optimize pacing delivered to the patient by, for example, inhibiting VSR pacing pulses based on misclassified cardiac events, etc. In embodiments where the RA electrode 75 is used to determine atrial events, or in embodiments where atrial pacing pulses are being delivered, the atrial events may be properly classified and the RBB and LBB electrodes may avoid misclassification of atrial events as ventricular events because the atrial events have already been identified as atrial events. The detected electrical activity indicative of an atrial event can be determined based on the monitored electrical activity from an initial monitored heartbeat, based on a second monitored heartbeat, based on a subsequent monitored heartbeat, based on an average heartbeat, etc.

[0095] The devices as described herein may identify the atrial events using any calculations or methodologies, such as by using sensing module 86 as described herein, processor 80 as described herein, etc. Some examples of fiducial points indicative of atrial events may include one or more of the following: onset of a P-wave morphology or any specific points therein, maximum signal amplitude, minimum signal amplitude, minimum and maximum signal slopes, any other monitored electrical activity signal waveform, etc.

[0096] The method 100 may further include determining a cardiac event classified as a ventricular event (e.g., RV depolarization, LV depolarization, etc.) based on the monitored electrical activity and within a time window 106. The determined cardiac event classified as a ventricular event can be based on the monitored electrical activity from the LBB electrode 50, for example. In alternative embodiments, the determined cardiac event classified as a ventricular event can be based on the monitored electrical activity from the RBB electrode 48, the LV electrode 94, etc. The detected electrical activity of a cardiacevent classified as a ventricular event can be determined based on the monitored electrical activity from an initial monitored heartbeat, based on a second monitored heartbeat, based on a subsequent monitored heartbeat, based on an average heartbeat, etc.

[0097] The devices as described herein may identify the cardiac events classified as ventricular events using any calculations or methodologies, such as by using sensing module 86 as described herein, processor 80 as described herein, etc. Some examples of fiducial points indicative of ventricular events may include one or more of the following: onset of a QRS morphology or any specific points therein, maximum signal amplitude, minimum signal amplitude, minimum and maximum signal slopes, any other monitored electrical activity signal waveform, etc.

[0098] The time window may define a preset time window where any sensed or determined cardiac event classified as ventricular events are considered to be misclassified because they occur too soon after a determined atrial event. Ventricular events do not happen simultaneously with atrial events due to normal heart function wherein the atria contract before the ventricles in order to pump blood through the heart. The time window may be based on at least one of a statistical analysis of a patient population, a pacing therapy algorithm, and a present value as set by a medical professional. Continuously sensing cardiac events during the time window may be advantageous compared to, e.g., blanking or purposefully not sensing anything during the time window. Continuous sensing may advantageously allow for proper classification of cardiac events during the time window and may offer more in-depth information to patients and medical professionals.

[0099] The time window may be between about 1 millisecond (ms) and about 200 ms. In at least one embodiment, the time window is 60 ms. In at least one embodiment, the time window is 150 ms. In other embodiments, the time window may be greater than or equal to 10 ms, greater than or equal to 20 ms, greater than or equal to 30 ms, greater than or equal to 40 ms, greater than or equal to 50 ms, greater than or equal to 57 ms, greater than or equal to 70 ms, etc. and / or less than or equal to 75 ms, 60 ms, 65 ms, 55 ms, 45 ms, 35 ms, 25 ms, 15 ms, 5 ms, etc.

[0100] If the determined cardiac event classified as a ventricular event does not occur within the time window, the method 100 may further execute or perform the standard device operation 108. For example, the devices described herein may continue toprovide ongoing delivery of the pacing therapy as a preset for a patient. Standard device operation 108 may further include ongoing delivery of pacing therapy using VSR or nonVSR modes.

[0101] If the determined cardiac event classified as a ventricular event occurs within the time window, then the method 100 may further include determining whether a pacing interval is below a threshold 110. The pacing interval may be defined as the interval between the sensed or determined cardiac event classified as ventricular event and the next scheduled ventricular pacing pulse to be delivered to the device (e.g., upon expiration of a scheduled AV interval).

[0102] A premature ventricular contraction (PVC) may be detected by the device as a ventricular event that follows another ventricular event without any intervening atrial event. However, in some cases (e.g., in rare cases), for example, a PVC may occur immediately following an atrial event, coincident with, or very close to an atrial event. The PVC may be sensed by the device as a ventricular event following close to the atrial event. A subsequent ventricular pacing pulse that depolarizes the ventricles may thus do so after the ventricles have already been depolarized due to the PVC. Such double-depolarization of the ventricles may create a risk of non-desirable proarrhythmic cardiac rhythm. However, if the ventricles have recently depolarized and the ventricular tissue is in its refractory period, then a paced pulse may be delivered without such risk because the paced pulse will not propagate through refractory tissue. After an action potential initiates in the ventricles, the ventricular tissue is unable to initiate another action potential for some duration of time. The pacing interval may be used to advantageously avoid delivering a pacing pulse (if the pacing pulse is based on misclassified cardiac events) on non-refractory tissue and creating proarrhythmic cardiac rhythm.

[0103] In one embodiment, the ventricular refractory period is about 250 ms.In alternative embodiments, the ventricular refractory period may be greater than or equal to 100 ms, greater than or equal to 125 ms, greater than or equal to 150 ms, greater than or equal to 175 ms, greater than or equal to 200 ms, greater than or equal to 225 ms, etc. and / or less than or equal to 250 ms, 215 ms, 180 ms, 160 ms, 140 ms, 120 ms, 105 ms, etc.

[0104] The threshold may be between about 10 ms and about 250 ms. In at least one embodiment, the pacing interval is 200 ms. In alternative embodiments, the pacing interval may be greater than or equal to 50 ms, greater than or equal to 100 ms, greater than or equal to 150 ms, greater than or equal to 175 ms, greater than or equal to 200 ms, greater than or equal to 225 ms, greater than 250 ms, etc. and / or less than or equal to 215 ms, 180 ms, 160 ms, 140 ms, 120 ms, 105 ms, 75 ms, 25 ms, etc.

[0105] If the determined pacing interval is not below the threshold, then the tissue will not be refractory and pacing pulses will propagate normally through the tissue. If the determined pacing interval is not below the threshold, then the method may further include delivering a ventricular pacing pulse at a nominal interval, or provide standard device operation 108. The nominal interval may be less than or equal to the ventricular refractory period. Thus, the delivered ventricular pacing pulse will avoid proarrhythmic double-depolarization of the ventricles in cases where the determined cardiac event classified as a ventricular event is a PVC. In cases where the determined cardiac event classified as a ventricular event is an atrial event that was over-sensed on a ventricular electrode, for example, the delivered ventricular pacing pulse at the nominal interval during standard device operation 108 will provide the sole ventricular depolarization.

[0106] If the determined pacing interval is below the threshold, the cardiac event classified as a ventricular event may be reclassified as a negligible ventricular event 112. For example, the cardiac event may be reclassified as at least one of: an over-sensed atrial depolarization, an arrhythmia beat, or a PVC. Continuous sensing and classification of cardiac events may advantageously allow for proper classification of cardiac events and may offer more in-depth information to patients and medical professionals compared to blanking or not sensing any cardiac events.

[0107] Reclassification may be based on at least one of a statistical analysis of a patient population, a pacing therapy algorithm, a present value as set by a medical professional, etc. For example, an ectopic heartbeat may be determined using the monitored electrical activity that is indicates an inconsistent PP interval or an inconsistent RR interval between a currently monitored heartbeat and a preceding average heart rate. Further, for example, an arrhythmic ventricular beat indicative of ventricular tachycardia may be determined as any ventricular event that follows another ventricular event at an interval that's less than or equal to a programmed ventricular tachycardia detection zone interval. An arrhythmic ventricular beat indicative of ventricular fibrillation may bedetermined as any ventricular event that follows another ventricular event at an interval that's less than or equal to a programmed ventricular fibrillation detection zone interval.

[0108] The method 100 may further include determining a ratio of atrial beats per minute to ventricular beats per minute (not shown). Determining the cardiac event classified as a ventricular event within the time window after the determined atrial event 106, determining the pacing interval below the threshold 110, and reclassifying the cardiac event as a negligible ventricular event 112, may be executed if the ratio of atrial beats per minute to ventricular beats per minute is about 1 : 1 (“one-to-one”). The 1 : 1 cardiac rhythm may advantageously allow for VSR and non- VSR modes to be enabled and used with LBB or RBB pacing and with the time window and AV delay as discussed herein. In at least one embodiment, the ratio of atrial beats per minute to ventricular beats per minute is 1 : 1.

[0109] In other embodiments, the ratio may be considered to be 1 : 1 if each of the last five atrial events were followed by a single ventricular event. In further embodiments, the ratio may be considered to be 1 : 1 if each of the last two, three, four, five, six, seven, eight, nine, ten, etc. atrial events were followed by a single ventricular event. In further embodiments, the ratio may be considered to be 1 : 1 if eight of the last ten atrial events were followed by a single ventricular event. In further embodiments, the ratio may be considered to be 1 : 1 if 50% or more of the last two, three, four, five, six, seven, eight, nine, ten, etc. atrial events were followed by a single ventricular event. In further embodiments, the ratio may be considered to be 1 : 1 if 60% or more, 70% or more, 80% or more, 90% or more, etc. of the last two, three, four, five, six, seven, eight, nine, ten, etc. atrial events were followed by a single ventricular event.

[0110] The method 100 of FIG. 5 may further include determining whetherVSR mode is enabled 114. If VSR mode is enabled, the method 100 may further include inhibiting a ventricular pacing pulse based on the cardiac event reclassification 116. VSR mode may be selected (either manually or automatically). Since VSR-enabled pacing results in a left ventricular pacing pulse when a right ventricular event is determined (or vice versa), accurate and correct ventricular sensing / event determination is beneficial in order to achieve biventricular pacing. If a determined cardiac event classified as a ventricular event is reclassified as a negligible ventricular event during VSR pacing, the VSR-automatic ventricular pacing pulse may be inhibited in order to avoid a pacing pulse that is not associated with a correct or accurate ventricular event.

[0111] If VSR mode is not enabled, the method 100 may further include delivering a ventricular pacing pulse when an AV delay expires and based on the cardiac event reclassification 118. The AV delay may be preset (such as by a physician or other medical professional) for the patient based on the patient’s physiological condition or may be calculated based on the pacing therapy and any algorithms associated with the pacing therapy. In at least one embodiment, the AV delay is 150 ms. In other embodiments, the AV delay may be greater than or equal to 100 ms, greater than or equal to 125 ms, greater than or equal to 150 ms, greater than or equal to 175 ms, greater than or equal to 200 ms, greater than or equal to 225 ms, etc. and / or less than or equal to 250 ms, 215 ms, 180 ms, 160 ms, 140 ms, 120 ms, 105 ms, etc.

[0112] If it is determined that the AV delay has expired, a ventricular pacing pulse may be delivered to the patient’s heart using at least one electrode 118. The ventricular pacing pulse may be delivered to the LV 32 using the LBB electrode 50, for example. In alternative embodiments, the ventricular pacing pulse may be delivered to the RV 28 using the RBB electrode 48. In further alternative embodiments, the ventricular pacing pulse may be delivered to the LV 32 using the LV electrode 94, etc.

[0113] If it is determined that the AV delay has not yet expired, the method100 may continue to wait until the AV delay has expired. The method 100 may further include determining if a ventricular event is sensed or determined after expiration of the time window and prior to expiration of the AV delay (not shown). If no ventricular event is determined prior to the expiration of the AV delay, then the method 100 may include delivering a ventricular pace 118 as described herein. If a ventricular event is determined prior to the expiration of the AV delay, and VSR is not enabled, then the ventricular pace may not be delivered when the AV delay expires. Instead, a determined ventricular event prior to expiration of the AV delay may be indicative of an already-synchronized ventricular depolarization, and no further ventricular pacing is required.

[0114] Various embodiments describing delivery of cardiac system pacing are discussed herein (e.g., using an IMD). Additionally, the method 100 may be performed more than once, so that a medical provider or user may periodically determine atrial and ventricular events (e.g., for each heartbeat), change pacing configurations, pacing configuration settings, etc., based on the determined atrial and ventricular events. Disease progression can make arrythmias more permanent, and continued monitoring can ensure optimized treatment for the patient over time.

[0115] The method 100 may further optionally include delivering a pacing therapy based on the determined cardiac events and / or AV delay (not shown), and such delivery may be done using the devices as described with respect to FIGS. 2-4.

[0116] Various examples have been described. These and other examples are within the scope of the following claims. For example, a single chamber, dual chamber, or triple chamber pacemakers (e.g., CRT-P) or ICDs (e.g., CRT-D) devices can be used to implement the illustrative methods described herein.

[0117] ILLUSTRATIVE EXAMPLES

[0118] While the present disclosure is not so limited, an appreciation of various aspects of the disclosure will be gained through a discussion of the specific illustrative examples provided below. Various modifications of the illustrative examples, as well as additional examples of the disclosure, will become apparent herein.

[0119] Example Exl : An implantable medical device (IMD) including at least one electrode configured to be disposed proximate a patient’s heart to sense cardiac electrical activity of the patient’s heart and to deliver a pacing therapy to the patient’s heart. The IMD also includes a computing apparatus including processing circuitry and operably coupled to the at least one electrode. The computing apparatus is configured to monitor cardiac electrical activity using the at least one electrode. The computing apparatus is further configured to determine an atrial event based on the monitored cardiac electrical activity. The computing apparatus is further configured to determine a cardiac event classified as a ventricular event within a time window after the determined atrial event. The computing apparatus is further configured to, in response to determination of the cardiac event classified as a ventricular event within the time window, reclassify the cardiac event as a negligible ventricular event.

[0120] Example Ex2: The IMD of Exl, where the computing apparatus is further configured to determine a pacing interval is below a threshold, and in response to determination of the pacing interval below the threshold, reclassify the cardiac event as a negligible ventricular event.

[0121] Example Ex3 : The IMD of Exl, where the pacing therapy includes cardiac resynchronization pacing.

[0122] Example Ex4: The IMD of Exl, where the at least one electrode is configured to be disposed proximate a left bundle branch.

[0123] Example Ex5: The IMD of Exl, where the time window is less than or equal to 150 milliseconds (ms).

[0124] Example Ex6: The IMD of Ex2, where the threshold is less than or equal to 200 ms.

[0125] Example Ex7: The IMD of Exl, where the computing apparatus is further configured to inhibit delivery of a ventricular sensing response (VSR) pacing pulse in response to reclassification of the cardiac event as a negligible ventricular event when VSR is enabled.

[0126] Example Ex8: The IMD of Exl, where the computing apparatus is further configured to initiate delivery of a pacing pulse to the patient’s heart using the at least one electrode when an AV delay expires in response to reclassification of the cardiac event as a negligible ventricular event.

[0127] Example Ex9: The IMD of Exl, where the computing apparatus is further configured to determine a ventricular event after expiration of the time window and prior to expiration of the AV delay. The computing apparatus is further configured to initiate delivery of a ventricular sensing response (VSR) pacing pulse in response to the determined ventricular event after expiration of the time window and prior to the expiration of the AV delay when VSR is enabled.

[0128] Example ExlO: The IMD of Exl, where the computing apparatus is further configured to determine a ratio of atrial beats per minute to ventricular beats per minute. Determining the cardiac event classified as a ventricular event within the time window after the determined atrial event and reclassifying the cardiac event is executed if the ratio of atrial beats per minute to ventricular beats per minute is 1 : 1.

[0129] Example Exl 1 : The IMD of Exl, where the negligible ventricular event includes one or more of an over-sensed atrial depolarization, an arrhythmia beat, and a premature ventricular contraction.

[0130] Example Exl2: A method including initiating delivery of a pacing therapy to a patient’s heart using at least one implantable electrode configured to be disposed proximate the patient’s heart. The method further includes monitoring cardiac electrical activity using the at least one implantable electrode. The method further includes determining occurrence of an atrial event based on the monitored cardiac electrical activity. The method further includes determining occurrence of a cardiac eventclassified as a ventricular event within a time window after a determined atrial event occurrence. The method further includes, in response to determination of the cardiac event classified as a ventricular event within the time window, reclassifying the cardiac event as a negligible ventricular event.

[0131] Example Exl3: The method of Exl2, further including determining a pacing interval is below a threshold, and in response to determination of the pacing interval below the threshold, reclassifying the cardiac event as a negligible ventricular event.

[0132] Example Exl4: The method of Exl2, where the pacing therapy includes cardiac resynchronization pacing.

[0133] Example Exl5: The method of Exl2, where the at least one electrode is configured to be disposed proximate a left bundle branch.

[0134] Example Exl6: The method of Exl2, where the time window is less than or equal to 150 milliseconds.

[0135] Example Exl7: The method of Exl3, where the threshold is less than or equal to 200 ms.

[0136] Example Exl8: The method of Exl2, further including inhibiting delivery of a ventricular sensing response (VSR) pacing pulse in response to reclassification of the cardiac event as a negligible ventricular event when VSR is enabled.

[0137] Example Exl9: The method of Exl2, further including initiating delivery of a pacing pulse to the patient’s heart using the at least one electrode when an AV delay expires in response to reclassification of the cardiac event as a negligible ventricular event.

[0138] Example Ex20: The method of Exl2, further including determining a ventricular event after expiration of the time window and prior to expiration of the AV delay. The method further includes initiating delivery of a ventricular sensing response (VSR) pacing pulse in response to the determined ventricular event after expiration of the time window and prior to expiration of the AV delay when VSR is enabled.

[0139] Example Ex21 : The method of Exl2, where the method further includes determining a ratio of atrial beats per minute to ventricular beats per minute, andwhere determining the cardiac event classified as a ventricular event within the time window after the determined atrial event and reclassifying the cardiac event is executed if the ratio of atrial beats per minute to ventricular beats per minute is 1 : 1.

[0140] Example Ex22: The method of Exl2, where the negligible ventricular event includes one or more of an over-sensed atrial depolarization, an arrhythmia beat, and a premature ventricular contraction.

[0141] Example Ex23: An implantable medical device (IMD) including at least one electrode configured to be disposed proximate a patient’s heart to sense cardiac electrical activity of the patient’s heart and to deliver a pacing therapy to the patient’s heart. The IMD further includes a computing apparatus including processing circuitry and operably coupled to the at least one electrode. The computing apparatus is configured to monitor cardiac electrical activity using the at least one electrode. The computing apparatus is further configured to determine an atrial event based on the monitored cardiac electrical activity. The computing apparatus is further configured to determine a cardiac event classified as a ventricular event within a time window after the determined atrial event. The computing apparatus is further configured to determine a pacing interval is below a threshold. The computing apparatus is further configured to, in response to determination of the cardiac event classified as a ventricular event within the time window and determination of the pacing interval below the threshold, inhibit delivery of a ventricular sensing response (VSR) pacing pulse when VSR is enabled, and initiate delivery of a pacing pulse to the patient’s heart using the at least one electrode when an AV delay expires when VSR or non-VSR is enabled.

[0142] This disclosure has been provided with reference to illustrative embodiments and examples and is not meant to be construed in a limiting sense. As described previously, one skilled in the art will recognize that other various illustrative applications may use the techniques as described herein to take advantage of the beneficial characteristics of the devices and methods described herein. Various modifications of the illustrative embodiments and examples will be apparent upon reference to this description.

[0143] In one or more examples, the described techniques may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions or codeon a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include non-transitory computer-readable media, which corresponds to a tangible medium such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other 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).

[0144] Instructions may 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 logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor” as used herein may refer to any of the foregoing structure or any other physical structure suitable for implementation of the described techniques. Also, the techniques could be fully implemented in one or more circuits or logic elements.

[0145] All references and publications cited herein are expressly incorporated herein by reference in their entirety for all purposes, except to the extent any aspect directly contradicts this disclosure.

[0146] All scientific and technical terms used herein have meanings commonly used in the art unless otherwise specified. The definitions provided herein are to facilitate understanding of certain terms used frequently herein and are not meant to limit the scope of the present disclosure.

[0147] Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims may be understood as being modified either by the term “exactly” or “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein or, for example, within typical ranges of experimental error.

[0148] The recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within that range. Herein, the terms “up to” or “no greater than” a number (e.g., up to 50) includes the number (e.g., 50), and the term “no less than” a number (e.g., no less than 5) includes the number (e.g., 5).

[0149] The terms “coupled” or “connected” refer to elements being attached to each other either directly (in direct contact with each other) or indirectly (having one or more elements between and attaching the two elements). Either term may be modified by “operatively” and “operably,” which may be used interchangeably, to describe that the coupling or connection is configured to allow the components to interact to carry out at least some functionality (for example, a mobile user device may be operatively coupled to a cellular network transmit data to or receive data therefrom).

[0150] Reference to “one embodiment,” “an embodiment,” “certain embodiments,” or “some embodiments,” etc., means that a particular feature, configuration, composition, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of such phrases in various places throughout are not necessarily referring to the same embodiment of the disclosure. Furthermore, the particular features, configurations, compositions, or characteristics may be combined in any suitable manner in one or more embodiments.

[0151] As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” encompass embodiments having plural referents, unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and / or” unless the content clearly dictates otherwise.

[0152] As used herein, “have,” “having,” “include,” “including,” “comprise,”“comprising” or the like are used in their open-ended sense, and generally mean “including, but not limited to.” It will be understood that “consisting essentially of,” “consisting of,” and the like are subsumed in “comprising,” and the like.

[0153] The term “and / or” means one or all of the listed elements or a combination of at least two of the listed elements.

[0154] The phrases “at least one of,” “comprises at least one of,” and “one or more of’ followed by a list refers to any one of the items in the list and any combination of two or more items in the list.

Claims

CLAIMSWhat is claimed:

1. An implantable medical device (IMD) comprising: a computing apparatus comprising processing circuitry and operably coupled to at least one electrode configured to be disposed proximate a patient’s heart to sense cardiac electrical activity of the patient’s heart and to deliver a pacing therapy to the patient’s heart, the computing apparatus configured to: monitor cardiac electrical activity using the at least one electrode; determine an atrial event based on the monitored cardiac electrical activity; determine a cardiac event classified as a ventricular event within a time window after the determined atrial event; and in response to determination of the cardiac event classified as a ventricular event within the time window, reclassify the cardiac event as a negligible ventricular event.

2. The IMD of claim 1, wherein the computing apparatus is further configured to determine a pacing interval is below a threshold, and in response to determination of the pacing interval below the threshold, reclassify the cardiac event as a negligible ventricular event.

3. The IMD of claim 1, wherein the time window is less than or equal to 150 milliseconds (ms).

4. The IMD of claim 2, wherein the threshold is less than or equal to 200 ms.

5. The IMD of claim 1, wherein the computing apparatus is further configured to: inhibit delivery of a ventricular sensing response (VSR) pacing pulse in response to reclassification of the cardiac event as a negligible ventricular event when VSR is enabled.

6. The IMD of claim 1, wherein the computing apparatus is further configured to: initiate delivery of a pacing pulse to the patient’s heart using the at least one electrode when an AV delay expires in response to reclassification of the cardiac event as a negligible ventricular event.

7. The IMD of claim 1, wherein the computing apparatus is further configured to: determine a ventricular event after expiration of the time window and prior to expiration of an AV delay; and initiate delivery of a ventricular sensing response (VSR) pacing pulse in response to the determined ventricular event after expiration of the time window and prior to the expiration of the AV delay when VSR is enabled.

8. The IMD of claim 1, wherein the computing apparatus is further configured to determine a ratio of atrial beats per minute to ventricular beats per minute, and wherein determining the cardiac event classified as a ventricular event within the time window after the determined atrial event and reclassifying the cardiac event is executed if the ratio of atrial beats per minute to ventricular beats per minute is 1 : 1.

9. The IMD of claim 1, wherein the negligible ventricular event comprises one or more of an over-sensed atrial depolarization, an arrhythmia beat, and a premature ventricular contraction.

10. A cardiac therapy system comprising: the IMD of any one of the preceding claims; and at least one implantable cardiac pacing lead coupled to the IMD, the at least one cardiac pacing lead including the at least one electrode.

11. The cardiac therapy system of claim 10, wherein the at least one electrode is configured to be disposed proximate a left bundle branch.

12. A method comprising: initiating delivery of a pacing therapy to a patient’s heart using at least one implantable electrode configured to be disposed proximate the patient’s heart; monitoring cardiac electrical activity using the at least one implantable electrode; determining occurrence of an atrial event based on the monitored cardiac electrical activity; determining occurrence of a cardiac event classified as a ventricular event within a time window after a determined atrial event occurrence; andin response to determination of the cardiac event classified as a ventricular event within the time window, reclassifying the cardiac event as a negligible ventricular event.

13. The method of claim 12, further comprising determining a pacing interval is below a threshold, and in response to determination of the pacing interval below the threshold, reclassifying the cardiac event as a negligible ventricular event.

14. The method of claim 12, further comprising inhibiting delivery of a ventricular sensing response (VSR) pacing pulse in response to reclassification of the cardiac event as a negligible ventricular event when VSR is enabled.

15. A cardiac therapy system comprising: at least one electrode configured to be disposed proximate a patient’s heart to sense cardiac electrical activity of the patient’s heart and to deliver a pacing therapy to the patient’s heart; and an implantable medical device (IMD) comprising a computing apparatus comprising processing circuitry and operably coupled to the at least one electrode, the computing apparatus configured to: monitor cardiac electrical activity using the at least one electrode; determine an atrial event based on the monitored cardiac electrical activity; determine a cardiac event classified as a ventricular event within a time window after the determined atrial event; determine a pacing interval is below a threshold; and in response to determination of the cardiac event classified as a ventricular event within the time window and determination of the pacing interval below the threshold, inhibit delivery of a ventricular sensing response (VSR) pacing pulse when VSR is enabled, and initiate delivery of a pacing pulse to the patient’s heart using the at least one electrode when an AV delay expires when VSR or non-VSR is enabled.

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