Adaptive cardiac conduction system pacing therapy for single lumen devices

Abstract

An adaptive cardiac conduction system pacing therapy may monitor electrical activity of a patient's heart and select a cardiac conduction system pacing therapy pacing pattern based on the monitored electrical activity. For example, one or more metrics, such as a P-wave to R-wave interval and a QRS complex wave width, may be determined based on monitored electrical activity, and one of a suppression pacing mode, a ventricular fusion pacing mode, an atrioventricular synchronization pacing mode, and an atrial fibrillation pacing mode may be selected based on the determined one or more metrics.

Description

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 411,986, filed on September 30, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure generally relates to adaptive cardiac conduction system pacing therapy provided by a single chamber device.

[0003] Implantable medical devices (IMDs), such as pacemakers or implantable cardioverter-defibrillators, deliver therapeutic stimulation to the patient's heart, thereby improving the lives of millions of heart disease patients. Figure 1 As shown, conventional pacing techniques involve pacing one or more of the four chambers of the patient's heart 12, including the left atrium 33, the right atrium 26, the left ventricle 32, and the right ventricle 28. A common conventional therapeutic pacing technique for treating a slow heart rate (called bradycardia) involves delivering electrical pulses to the patient's right ventricular tissue. In response to the electrical pulses, both the right and left ventricles contract. However, because the pulses propagate from the right ventricle through the left ventricle, the heartbeat process may be significantly delayed. The electrical pulses pass through muscle cells called myocytes. Conduction between myocytes may be very slow. The delayed electrical pulses may cause the left ventricle to lose synchronization with the right ventricle.

[0004] Over time, the left ventricle can become very inefficient at pumping blood to the body. For some patients, heart failure can develop to the point where the heart is too weak to pump blood to the body. Heart failure can be a devastating diagnosis because, for example, fifty percent of heart failure patients have a life expectancy of five years or less. Another 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 heart's atria may beat out of sync with the heart's ventricles due to the arrhythmia of the atria, which can cause blood clots in the heart and increase the risk of, for example, stroke or heart failure.

[0005] To avoid the potential development of heart failure, some physicians have considered alternative pacing methods involving the heart's conduction system. Pacing the heart's conduction system can conduct electrical impulses quickly (e.g., similar to a car traveling on a highway), while pacing the heart muscle or myocardial tissue can conduct electrical impulses more slowly (e.g., similar to a car traveling on a muddy road).

[0006] The cardiac conduction system includes the sinoatrial node 1, the atrial nodal bundles 2, 4, 5 (i.e., the anterior nodal bundle 2, the middle nodal bundle 4, and the posterior nodal bundle 5), the atrioventricular node 3, the His bundle 13 (also called the atrioventricular bundle or His bundle), the left bundle branch 8a, and the right bundle branch 8b. Figure 1 The aortic arch 6 and Buckman's bundle 7 are also shown. Figure 1The sinoatrial node 1, located at the junction of the superior vena cava and the right atrium, is considered the heart's natural pacemaker because it continuously and repeatedly fires electrical impulses. The electrical impulses travel through the muscle of the right atrium 26 to the left atrium 33 to cause synchronized contraction of the atria. The electrical impulses are also delivered to the atrioventricular node 3 (the only connection between the atria and ventricles) via the interatrial nodal bundle. Conduction through the atrioventricular node, or atrioventricular node tissue, takes longer than through atrial tissue, which results in a delay between atrial contraction and the start of ventricular contraction. Atrioventricular delay is the delay between atrial contraction and ventricular contraction that allows the atria to empty blood into the ventricles. Then, and Arises via His bundle branch Ventricle shrink Together , the valve between the atria and ventricles closes. The bundle of His or His bundle 13 is located in the membranous atrioventricular septum, near the tricuspid annulus. The bundle of His 13 divides into left and right bundle branches 8a, 8b, and is formed by specialized fibers called "Purkinje fibers" 9. The Purkinje fibers 9 can be described as being able to rapidly conduct action potentials along the ventricular septum (VS), rapidly extend the depolarization wave front through the remaining ventricular myocardium, and produce a coordinated contraction of the ventricular muscle groups.

[0007] Cardiac resynchronization devices and implanted cardiac defibrillators are complex devices that may include two or more cardiac leads placed in the heart with up to 10 insulated conductors extending between the device and the heart. The risk of adverse events associated with a CRT or ICD device may increase with the number of implanted leads and the number of conductors contained within the leads. Therefore, it is desirable to reduce the number of leads and the number of conductors contained within the leads.

[0008] Conventional cardiac pacing may risk desynchronizing normal ventricular contraction. Although cardiac resynchronization therapy (CRT) was invented to correct cardiac desynchronization, the left ventricular epicardium and right ventricular apex pacing commonly used in CRT may be suboptimal pacing locations. Therefore, a ventricular pacing method to restore normal ventricular synchronization is needed.

[0009] Additionally, patients with long P-wave to R-wave intervals (e.g., indicating first-degree heart block) may suffer from an increased risk of atrial fibrillation and heart failure. Additionally, triggered ventricular pacing to correct the long P-wave to R-wave intervals may result in less synchronized ventricular contractions. Therefore, it may be desirable to provide both atrioventricular and ventricular synchronized pacing, which allows correction of any cardiac conduction abnormalities without introducing desynchronization. Summary of the invention

[0010] The present disclosure generally relates to adaptive cardiac conduction system pacing.In addition, exemplary systems, devices, and methods may be described as providing a single chamber device solution for patients indicated for cardiac resynchronization therapy.

[0011] Exemplary systems, devices, and methods may be described as providing adaptive cardiac conduction system pacing therapy for a single chamber device that produces atrioventricular and ventricular synchronization for altering conduction disorders. In one or more embodiments, far-field P wave sensing may provide a cardiac conduction system pacing therapy trigger when not in atrial fibrillation. A conduction check may be performed or performed periodically to determine whether the patient has a normal P wave to R wave interval (e.g., normal atrioventricular conduction), a narrow QRS complex wave width, and a consistent R wave to R wave interval and T wave to P wave interval. The applied pacing mode may then be determined based on the results of the conduction check. If the patient has a normal P wave to R wave interval and a narrow QRS complex wave width, pacing may be avoided. If the patient has a normal P wave to R wave interval and a wide QRS complex wave width, the cardiac conduction system pacing therapy may be configured to achieve ventricular fusion between intrinsic ventricular depolarization and paced depolarization. If the patient has a long P wave to R wave interval, cardiac conduction system pacing therapy may be delivered at a fixed time interval after a far-field P wave is detected. If atrial fibrillation is detected, cardiac conduction system pacing therapy may be delivered to slightly overdrive the ventricles, thereby providing effective cardiac resynchronization therapy during the atrial fibrillation mode.

[0012] Exemplary systems, devices, and methods may be described as utilizing a combination of far-field P-wave sensing to allow triggered ventricular pacing without the need for atrial leads and cardiac conduction system pacing, thereby maintaining synchronized ventricular activation when pacing the ventricles. Thus, a single lead having two conductors electrically coupled to the tip and ring electrodes or the tip and coil electrodes may be used to correct long P-wave to R-wave intervals, complete atrioventricular block, or pathological ventricular asynchrony without introducing ventricular asynchrony. In addition, exemplary systems, devices, and methods may be configured to sense P waves from far-field electrograms (e.g., monitored from ring electrodes to shell electrodes, monitored from coil electrodes to shell electrodes), which may be used to synchronize cardiac conduction system pacing (e.g., delivered to the His bundle, left bundle branch, or bundle branch bundle).

[0013] Exemplary systems, devices, and methods may be described as providing, among other things, a single-chamber pacemaker mode to restore or maintain atrioventricular synchronization using heart sounds or heart motion. In particular, exemplary systems, devices, and methods may be described as providing an adaptive pacing mode for a single-chamber device with a single lead for cardiac conduction system pacing using a mechanical cardiac activation sensor such as an accelerometer or microphone. Cardiac conduction system pacing (e.g., His or left bundle branch area pacing) can provide synchronized left ventricular contraction, and in some embodiments, appropriate atrioventricular timing of cardiac conduction system pacing can produce improved right ventricular and left ventricular synchronization. In order to provide optimal atrioventricular synchronization, a microphone or accelerometer may be used to sense atrial drive (i.e., atrial mechanical activation) to trigger cardiac conduction system pacing. In some embodiments, electrical far-field P wave sensing may be combined with atrial mechanical sensing to improve detection of atrial activation. In addition, a mode switch may be triggered or activated when a patient has atrial fibrillation. Atrial fibrillation may be detected by the absence of a mechanical shock or a combination of mechanical and electrical changes from normal sinus rhythm. Additionally, periodic conduction studies can be used to determine the optimal AV interval.Thus, atrioventricular and ventricular synchrony can be maintained by a device having a single lead and microphone or accelerometer.

[0014] In other words, the exemplary systems, systems, and devices can utilize a single lead or a leadless device and provide atrioventricular and ventricular synchronization. A microphone or accelerometer located in the housing or can or on the lead of the IMD can be configured to sense atrial drive (e.g., mechanical activation of the atrium) to trigger cardiac conduction system pacing (e.g., VDD pacing with His bundle pacing or left bundle branch area pacing). In some embodiments, electrical sensing of far-field P waves can supplement or assist mechanical sensing, or vice versa. For example, after a suspected far-field P wave, the signal from the microphone / accelerometer can be checked for a confirmatory mechanical signal indicating atrial drive. Conduction checks can be performed periodically to determine whether the patient has normal atrioventricular conduction and a narrow QRS complex width. The pacing mode applied can depend on the results of the conduction check. If the patient has a normal P wave to R wave interval and a narrow QRS complex width, pacing can be avoided (e.g., using an inhibitory pacing mode). If the patient has a normal P-wave to R-wave interval and a wide QRS complex width, the exemplary methods and processes may attempt to achieve ventricular fusion between cardiac conduction system pacing and any remaining intrinsic activation of the ventricles to provide cardiac resynchronization therapy. If the patient has a long P-wave to R-wave interval, cardiac conduction system pacing may be delivered at a fixed time interval after atrial activation. If atrial fibrillation is detected, the exemplary methods and processes may switch to attempting to slightly overdrive the ventricles during an atrial fibrillation mode using cardiac conduction system pacing therapy with effective cardiac resynchronization therapy.

[0015] Exemplary systems, devices and methods may also be described as providing cardiac conduction system pacing therapy to correct desynchronization in implantable cardioverter-defibrillator patients. Exemplary systems, devices and methods may provide cardiac conduction system pacing leads that can detect electrical desynchronization that has worsened in the implanted patient, and upon such detection, pacing the cardiac conduction system to correct desynchronization and prevent worsening heart failure. In addition, in the case of cardiac arrest or AV block, such functions may be functions in addition to standard pacing functions. In at least one embodiment, the interval between the start and offset of the QRS complex wave, also referred to as the QRS complex wave width, may be sensed or monitored on a far-field electrogram (e.g., using a tip electrode to a housing electrode measurement). Such QRS measurements may be periodic, such as, for example, once every 12 hours when the baseline heart rate is less than 90 beats per minute. Gradually worsening heart failure may be detected in response to a consistent trend in the width of a wide QRS complex wave. In at least one embodiment, worsening heart failure can be detected in response to the QRS complex width exceeding a certain threshold value, such as 130 milliseconds (ms), in a selected number n of consecutive measurements. If progressive worsening heart failure is detected, cardiac conduction system pacing therapy can be initiated in synchronization with atrial activity at a nominal sensed AV delay of 100 ms or a paced AV delay of 120 ms to correct the desynchronization. Periodic measurements can be continued by pausing pacing for a few beats. If the consecutive measurements of the QRS complex width are below a certain threshold value, such as, for example, 120 ms, which would indicate normal electrical function, the cardiac conduction system pacing therapy can be stopped.

[0016] An exemplary implantable medical device may include a computing device that includes a processing circuit and is operably connected to one or more electrodes. The one or more electrodes may include a cardiac conduction system pacing electrode that can be positioned near a portion of a patient's cardiac conduction system. The computing device may be configured to provide an inhibition pacing mode, a ventricular fusion pacing mode, an atrioventricular synchronization pacing mode, and an atrial fibrillation pacing mode. The computing device may be further configured to perform a conduction test. Performing a conduction test may include delaying the delivery of cardiac conduction system pacing therapy to allow intrinsic cardiac activation, monitoring the intrinsic electrical activity of the patient's heart using one or more electrodes during intrinsic cardiac activation, determining one or more metrics based on the monitored intrinsic electrical activity, and selecting one of the inhibition pacing mode, the ventricular fusion pacing mode, the atrioventricular synchronization pacing mode, and the atrial fibrillation pacing mode based on the determined one or more metrics. The computing device may be further configured to deliver cardiac conduction system pacing using the cardiac conduction system pacing electrode according to the selected mode.

[0017] An exemplary system may include one or more implantable electrodes to sense the electrical activity of a patient's heart and deliver cardiac therapy to the patient's heart. The one or more implantable electrodes may include a cardiac conduction system pacing electrode that can be positioned proximate to a portion of the patient's cardiac conduction system to deliver cardiac conduction system pacing therapy to the portion of the patient's cardiac conduction system. The system may further include a computing device that includes a processing circuit and is operably connected to the one or more implantable electrodes. The computing device may be configured to provide an inhibition pacing mode, a ventricular fusion pacing mode, an atrioventricular synchronization pacing mode, and an atrial fibrillation pacing mode, and perform a conduction test. Performing a conduction test may include delaying the delivery of cardiac conduction system pacing therapy to allow intrinsic cardiac activation, monitoring the intrinsic electrical activity of the patient's heart using one or more electrodes during the intrinsic cardiac activation, determining one or more metrics based on the monitored intrinsic electrical activity, and selecting one of the inhibition pacing mode, the ventricular fusion pacing mode, the atrioventricular synchronization pacing mode, and the atrial fibrillation pacing mode based on the determined one or more metrics. The computing device may further be configured to deliver cardiac conduction system pacing using the cardiac conduction system pacing electrode according to the selected mode.

[0018] An exemplary method may include providing an inhibition pacing mode, a ventricular fusion pacing mode, an atrioventricular synchronization pacing mode, and an atrial fibrillation pacing mode, and performing a conduction test. Performing a conduction test may include delaying the delivery of cardiac conduction system pacing therapy to allow intrinsic cardiac activation, monitoring intrinsic electrical activity of the patient's heart using one or more electrodes during the intrinsic cardiac activation, determining one or more metrics based on the monitored intrinsic electrical activity, and selecting one of the inhibition pacing mode, the ventricular fusion pacing mode, the atrioventricular synchronization pacing mode, and the atrial fibrillation pacing mode based on the determined one or more metrics. The method may further include delivering cardiac conduction system pacing according to the selected mode using a cardiac conduction system pacing electrode that can be positioned proximate to a portion of the patient's cardiac conduction system.

[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 in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic diagram of a patient's heart and conduction system.

[0021] Figure 2A is a conceptual diagram illustrating an illustrative therapy system configured to provide cardiac conduction system pacing therapy to the His bundle using leads placed in the right atrium.

[0022] Figure 2B It is shown Figure 2A A more detailed conceptual diagram of an exemplary treatment system.

[0023] Figure 2C It is shown Figure 2A Detailed conceptual diagram of an exemplary treatment system including only two leads.

[0024] Figure 2D It is shown Figure 2A Detailed conceptual diagram of an exemplary treatment system but including only a single lead.

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

[0026] Figure 3B yes Figure 3A A close up view of the leads in a patient's heart.

[0027] Figure 3C is a diagram showing a heart sound signal changing over time.

[0028] Figure 4A is a conceptual diagram of an illustrative therapy system configured to provide cardiac conduction system pacing therapy to the left and / or right bundle branches using leads placed in the right ventricle.

[0029] Figure 4B It is shown Figure 4A Detailed conceptual diagram of an exemplary treatment system including only two leads.

[0030] Figure 5 It is shown FIG. 2A to FIG. 2D A functional block diagram of an example configuration of an implantable medical device.

[0031] Figure 6 Figure 2 to Figure 5 A block diagram of an illustrative method for an adaptive cardiac conduction system that may be utilized by a device.

[0032] Figure 7 Select Figure 2 to Figure 5 Single chamber devices are available Figure 6 A state diagram of an illustrative method of a cardiac conduction system pacing mode.

[0033] Figure 8 Select Figure 2 to Figure 5 The device can be used Figure 6 to Figure 7 Block diagram of an illustrative method of an atrial fibrillation pacing mode.

[0034] Fig. 9 Figure 2 to Figure 5 Block diagram of an illustrative method for far-field sensing of P-waves that may be employed by a single-chamber device.

[0035] Fig.10 It is available with Fig. 9 A block diagram of an illustrative method for determining and adjusting the posterior ventricular atrial blanking period for use with the method.

[0036] Fig.11 It is shown Fig. 9 Plot of the filtered and rectified far-field signal of the method.

[0037] Fig.12 It further shows Fig. 9 Method Fig.11 The extended part of the graph.

[0038] Fig.13 Figure 2 to Figure 5 Block diagram of an illustrative method for delivering cardiac conduction system pacing therapy in response to worsening heart failure that may be utilized by a device. DETAILED DESCRIPTION

[0039] In the following detailed description of exemplary embodiments, reference is made to the accompanying drawings, which form a part of the embodiments, and in which are shown by way of illustration specific embodiments that can be practiced. It should be understood that other embodiments can be utilized and the structural scope can be changed without departing from (e.g., still falling within) the scope of the present disclosure hereby presented.

[0040] Will refer to Figures 1 to 13 Describe exemplary systems, devices and methods. It will be apparent to those skilled in the art that elements or processes from one embodiment may be used in combination with elements or processes of other embodiments, and possible embodiments of such systems, devices and methods using the feature combinations set forth herein are not limited to the specific embodiments shown in the figures and / or described herein. Further, it will be appreciated that the embodiments described herein may include many elements that are not necessarily shown to scale. Further, it will be appreciated that the timing of the processes herein and the size and shape of the individual elements may be modified but still fall within the scope of the present disclosure, but certain timings, one or more shapes and / or sizes or element types may be superior to other timings, one or more shapes and / or sizes or element types.

[0041] Figure 1 A schematic diagram of a heart 12 is depicted, and FIGS. 2-4 depict conceptual diagrams showing exemplary treatment systems that may be used to provide treatment to the heart 12 of a patient 14. The patient 14 is typically, but not necessarily, a human. FIG. 2A to FIG. 2BAs shown, therapy system 10 may include an IMD 16 coupled to three leads 18, 20, 23 and a programmer 24. IMD 16 may be, for example, an implantable pacemaker, cardioverter, and / or defibrillator that provides electrical pulses to heart 12 via electrodes coupled to one or more of leads 18, 20, 23. Other non-limiting examples of IMD 16 include the following: a pacemaker with medical leads, 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., a neurostimulator, an insertable monitoring device, etc.).

[0042] Leads 18, 20, 23 may extend into the heart 12 of the patient 14 to sense electrical activity of the heart 12 and / or deliver electrical stimulation to the heart 12. Figure 2A In the example shown, the right ventricular lead 18 extends through one or more veins (not shown), the superior vena cava (not shown), and the right atrium 26, and into the right ventricle 28. 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 reach an area adjacent to the free wall of the left ventricle 32 of the heart 12. The cardiac conduction system pacing therapy lead 23 (e.g., a left bundle branch pacing lead, a right bundle branch pacing lead, a His bundle pacing lead, etc.) extends through one or more veins and the vena cava, and into the right atrium 26 of the heart 12 to pace the cardiac conduction system (e.g., through the triangle of Koch's region, within the septal wall, near and / or in direct contact with the left bundle branch 8a, near and / or in direct contact with the right bundle branch 8b, near and / or in direct contact with the His bundle 13, etc.). In some embodiments, the cardiac conduction system pacing therapy lead 23 can be positioned within about 1 mm of a portion of the cardiac conduction system, such as, for example, the His bundle 13, the left bundle branch 8a, the right bundle branch 8b, etc. In one or more embodiments, the cardiac conduction system therapy lead can be further positioned or placed through the tricuspid valve into the right ventricle 28 and implanted in the ventricular septum (VS), for example, about 1 cm to 2 cm in the apical direction, as will be referred to herein. FIG. 3A to FIG. 3B and FIG. 4A to FIG. 4B An example of a cardiac conduction system pacing therapy lead (eg, a His lead) may be a SELECTSECURE TM 3830. SELECTSECURE TM For a description of the 3830 see Medtronic Model SELECTSECURE TM 3830 Manual (2013), which is incorporated herein by reference in its entirety. TM 3830 includes two conductors having lumens.

[0043] As used herein, cardiac conduction system pacing therapy refers to any pacing therapy configured to deliver pacing therapy (e.g., pacing pulses, electrical stimulation, etc.) to the cardiac conduction system, including, for example, the His bundle 13, the left bundle branch 8a, the right bundle branch 8b, etc. As used herein, the term "activation" refers to a sensed or paced event. For example, atrial activation can refer to an atrial sense or event (As) or atrial pacing or an atrial pacing artifact (Ap). As will be described herein, atrial sensing can be detected or identified in one or more different signals monitored using one or more different devices or sensors located at one or more different locations. For example, atrial sensing can be detected in a near-field electrical signal from an electrode positioned in the right atrium. In addition, for example, atrial sensing can be detected in a far-field electrical signal from an electrode positioned outside the right atrium (such as in the right ventricle or ventricular septum). In addition, for example, atrial sensing can be detected in far-field signals from a mechanical cardiac activation sensor, such as an accelerometer or microphone (e.g., a heart sound sensor) positioned outside the right atrium (such as in the right ventricle or ventricular septum) or another part of the patient's body (e.g., within a can or housing of an IMD positioned outside the patient's heart). Similarly, ventricular activation can refer to ventricular perception or events (Vs) or ventricular pacing or ventricular pacing artifacts (Vp), which can be described as ventricular stimulation pulses. In some embodiments, activation intervals from As or Ap to Vs or Vp and from Vp to Vs can be detected. In particular, activation intervals can include pacing (Ap or Vp) to ventricular intervals (left ventricle or right ventricle sensing) or atrial sensing (As) to ventricular sensing intervals (left ventricle or right ventricle sensing).

[0044] An exemplary IMD may be described as delivering one or both of conventional pacing therapy and cardiac conduction system pacing therapy. Conventional or traditional pacing therapy may be described as delivering pacing pulses to myocardial tissue that is not part of the cardiac conduction system of the patient's heart, such that, for example, the pacing pulse triggers 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 before the myocardial tissue. For example, conventional pacing therapy may deliver pacing pulses directly to muscular heart tissue (e.g., myocardial tissue) that is to be depolarized to provide cardiac contraction. For example, conventional left ventricular pacing therapy may utilize an implanted left ventricular coronary sinus lead 20 to extend through one or more veins, the vena cava, the right atrium 26 and into the coronary sinus 30 to reach an area adjacent to the free wall of the left ventricle 32 of the heart 12 to deliver pacing pulses to the myocardial tissue of the free wall of the left ventricle 32.

[0045] An exemplary left ventricular lead 20 having a set of spaced electrodes is shown in U.S. Patent Publication No. WO2019 / 104174A1, filed by Ghosh et al. on May 4, 2012, which is incorporated herein by reference in its entirety. Exemplary electrodes on a lead for forming a pacing vector are shown and described in U.S. Patent No. 8,355,784B2 and U.S. Patent No. 8,126,546, each of which is incorporated herein by reference in its entirety.

[0046] In addition, the pacing therapy leads 18, 20, 23 can be used to deliver left ventricular or left ventricular septal pacing to the ventricular septal wall. At least one of the pacing therapy leads 18, 20, 23 can 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 septal wall of the left ventricle 32 of the heart 12.

[0047] Exemplary cardiac conduction system pacing therapy may be described, for example, in U.S. Patent Application Publication No. 2019 / 0111270A1, entitled “His Bundle and Bundle Branch Pacing Adjustment,” published on April 18, 2019, which is incorporated herein by reference in its entirety. Exemplary left ventricular septal pacing may be described, for example, in U.S. Patent Application Serial No. 16 / 521,000, entitled “AV Synchronous Septal Pacing,” filed on July 24, 2019, which is incorporated herein by reference in its entirety.

[0048] One or more elongated conductors of any one of the leads 18, 20, 23 may extend through the airtight feedthrough assembly and within the insulating tubular member of the corresponding lead, and an electrical pulse generator (contained in the housing) may be electrically connected to one or more electrodes, such as, for example, a ring electrode, a tip electrode, a spiral electrode, etc. The conductor may be formed by one or more conductive wires in a coiled or cabled configuration, the conductive wire comprising, for example, an MP35N alloy known to those skilled in the art, and the insulating tubular member may be any suitable medical grade polymer, such as polyurethane, silicone rubber, or a blend thereof. According to one or more exemplary embodiments, the flexible lead body may extend from the proximal end to a predetermined length (e.g., about 10 centimeters (cm) to about 20 cm, or about 15 cm to 20 cm) to the distal end. The size of the lead body may be less than about 7 French (FR), but is typically in the range of about 3 FR to 4 FR. In one or more embodiments, a lead body of about 2 FR size to about 3 FR size is used.

[0049] Cardiac conduction system pacing may include at least one of His bundle pacing and left bundle branch pacing and / or right bundle branch pacing. Bundle branch pacing may bypass pathological areas and may have a low and stable pacing threshold. In some embodiments, only one of the left bundle branch or the right bundle branch may be paced using one or more pacing leads. In another embodiment, both bundle branches may be paced simultaneously (e.g., dual bundle branch pacing), which may simulate the inherent activation propagation via the His bundle-Purkinje conduction system, for example, the activation of pacing propagates to both ventricles via the two bundle branches for synchronous contraction. On the other hand, His bundle pacing typically paces the His bundle close to the bundle branch. In some embodiments, the IMD 16 may include one, two, or more electrodes located in one or more bundle branches configured for bundle branch pacing.

[0050] In some embodiments, the IMD 16 may be an intracardiac pacemaker or a leadless pacing device (LPD) configured to pace one or more portions of the cardiac conduction system, such as the His bundle. As used herein, "leadless" refers to a device without leads extending out of the heart 12. In other words, the leads of the leadless device may not extend from the outside of the heart to the inside of the heart. Some leadless devices may be introduced through a vein, but once implanted, the leadless device does not or may not include any transvenous leads, and may be configured to provide cardiac therapy without the use of any transvenous leads. In one or more embodiments, when the housing of the device is positioned in the atrium, an exemplary LPD for bundle pacing does not use leads to be operably connected to electrodes disposed proximal to the septum. The leadless electrode can be connected to the housing of the medical device without leads, without the use of leads between the electrode and the housing.

[0051] IMD 16 may be coupled to at least one of leads 18, 20, 23 via a Figure 2B The various electrodes shown are used to sense electrical signals associated with depolarization and repolarization of heart 12. In some examples, IMD 16 provides pacing pulses to heart 12 based on the electrical signals sensed within heart 12. The configuration of electrodes used by IMD 16 for sensing and pacing may be unipolar or bipolar.

[0052] IMD 16 may also provide defibrillation therapy and / or cardioversion therapy via electrodes located on at least one of leads 18, 20, 23. For example, IMD 16 may detect an atrial arrhythmia of heart 12, such as atrial fibrillation of atria 26, 33, and may then deliver defibrillation therapy in the form of electrical pulses to heart 12. IMD 16 may also detect a ventricular arrhythmia of heart 12, such as ventricular fibrillation of ventricles 28, 32, and may then deliver defibrillation therapy in the form of electrical pulses to heart 12. In some examples, IMD 16 may be programmed to deliver a course of therapy, e.g., pulses of increasing energy levels, until the fibrillation of heart 12 ceases. IMD 16 may detect fibrillation using one or more fibrillation detection techniques known in the art.

[0053] In some examples, such as Figure 2A The programmer 24 shown may be a handheld computing device or a computer workstation or a mobile phone. The programmer 24 may include a user interface for receiving input from a user. The user interface may include, for example, a keypad and a display, which may be, for example, a cathode ray tube (CRT) display, a liquid crystal display (LCD), or a light emitting diode (LED) display. The keypad may take the form of an alphanumeric keypad or a reduced set of keys associated with specific functions. The programmer 24 may additionally or alternatively include a peripheral pointing device such as a mouse, via which the user may interact with the user interface. In some embodiments, the display of the programmer 24 may include a touch screen display, and the user may interact with the programmer 24 via the display. Through a graphical user interface on the programmer 24, the user may configure one or more pacing therapies, select one or more pacing modes, etc.

[0054] In addition, various pacing settings can be adjusted or configured based on various sensed signals. For example, various near-field signals and far-field signals can be sensed by one or more of the electrodes of the IMD 16 and / or other devices operably connected thereto. For example, the P-wave to R-wave interval can be monitored or measured within the near-field or far-field signal, and can then be used to adjust, configure, and select cardiac conduction system pacing therapy. In addition, for example, the QRS width can be monitored or measured within the near-field or far-field signal, and can then be used to adjust, configure, and select cardiac conduction system pacing therapy. In addition, for example, one or more of the R-wave to R-wave interval consistency, the T-wave to P-wave interval consistency, and the P-wave morphology consistency can be monitored or measured within the near-field or far-field signal, and can then be used to adjust, configure, and select cardiac conduction system pacing therapy.

[0055] Exemplary therapy systems described herein, such as IMD 16, may be used to deliver cardiac conduction system pacing therapy according to a variety of different modes, such as, for example, an inhibition pacing mode, a ventricular fusion pacing mode, an atrioventricular synchronization pacing mode, an atrial fibrillation pacing mode, etc.

[0056] The ventricular fusion pacing mode can be configured to deliver cardiac conduction system pacing therapy to provide effective ventricular fusion. Effective ventricular fusion can be described as synchronizing the timing of left ventricular activation with activation on the right ventricle. For example, in a fusion pacing configuration, the medical device can deliver one or more pacing pulses 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 due to the intrinsic conduction of the heart. In this way, the intrinsic and pacing-induced excitation wavefronts can fuse together, thereby resynchronizing the depolarization of the left ventricle with the depolarization of the right ventricle.

[0057] As used herein, the term "far-field" electrical signal refers to the result of measuring cardiac activity using a sensor such as an electrode located outside the region of interest. For example, a far-field electrical signal representing the electrical activity of the chamber of interest of the patient's heart can be measured from an electrode positioned in an adjacent cavity (i.e., a cavity different from the cavity of interest that is immediately adjacent to or close to the cavity of interest). More specifically, for example, atrial electrical activity representing depolarization of one or both atria or electrical activity originating from one or more of the atria on both sides can be monitored in a far-field electrical signal, which is measured using an electrode positioned outside the right atrium (such as in the right ventricle 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 the region of interest. For example, an electrical signal measured from an electrode located on the left side of the patient's ventricular septum is an example of a near-field electrical signal of the patient's LV.

[0058] The P wave timing is the time at which a P wave is detected. Typically, the P wave timing includes using the maximum first derivative of the rising edge of the P wave (or the time of the maximum P wave value). The P wave timing is also used in device marker channels to indicate the P wave time or atrial activation time. The P wave timing can be determined using near-field signals obtained by sensors (e.g., electrodes, accelerometers, heart sound sensors, etc.) positioned in the atrium (e.g., right atrium) and / or far-field near-field signals obtained by sensors (e.g., electrodes, accelerometers, heart sound sensors, etc.) positioned outside the atrium (e.g., right atrium) (such as in the right ventricle and / or ventricular septum).

[0059] R wave timing is the time in which the QRS complex is detected. Typically, R wave timing includes using the maximum first derivative of the rising edge of the R wave (or the time of maximum R wave value). R wave timing is also used in the device marker channel to indicate the R wave time or ventricular activation time.

[0060] A user, such as a physician, technician, or other clinician, may interact with programmer 24 to communicate with IMD 16. For example, a user may interact with programmer 24 to retrieve physiological or diagnostic information from IMD 16. In addition, a user may also interact with programmer 24 to program IMD 16, for example, to select values ​​for operating parameters of IMD 16. IMD 16 and programmer 24 may communicate via wireless communications using any technology known in the art. Examples of communication technologies may include, for example, low frequency or radio frequency (RF) telemetry, but other technologies are also contemplated. In some examples, programmer 24 may include a programming head that may be placed adjacent to the patient's body near the implant site of IMD 16 to improve the quality or safety of communication between IMD 16 and programmer 24.

[0061] Figure 2B is a conceptual diagram illustrating IMD 16 and leads 18, 20, 23 of therapy system 10 in greater detail. Three-chamber IMD 16 may be used for cardiac rhythm therapy and defibrillation or cardioversion therapy (CRT-D). 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 are electrically coupled to corresponding electrical contacts within connector block 34. Additionally, in some examples, leads 18, 20, 23 may be mechanically coupled to connector block 34 by means of set screws, connecting pins, or another suitable mechanical coupling mechanism.

[0062] Each of the leads 18, 20, 23 includes an elongated insulated lead body that can carry a plurality of concentric coiled conductors separated from one another by a tubular insulated sheath. In the example shown, an optional pressure sensor 38 and bipolar electrodes 40 and 42 are positioned proximate the distal end of the right ventricular lead 18. Additionally, bipolar electrodes 44 and 46 are positioned proximate the distal end of the left ventricular lead 20, and bipolar electrodes 48 and 50 are positioned proximate the distal end of the cardiac conduction pacing lead 23. The cardiac conduction system pacing electrode 50 can be used for pacing and / or sensing of cardiac conduction system tissue (e.g., His bundle tissue or bundle branch tissue).

[0063] exist Figure 2BIn the embodiment of the present invention, pressure sensor 38 is disposed in right ventricle 28 and may be responsive to absolute pressure inside right ventricle 28. Pressure sensor 38 may be, for example, a capacitive or piezoelectric absolute pressure sensor. In other examples, pressure sensor 38 may be positioned in other areas of heart 12 and may monitor pressure in one or more of the other areas of heart 12, or pressure sensor 38 may be positioned elsewhere within or near the cardiovascular system of patient 14 to monitor cardiovascular pressure associated with mechanical contraction of the heart. Optionally, a pressure sensor in the pulmonary artery in communication with IMD 16 may be used.

[0064] Electrodes 40, 44, and 48 may take the form of ring electrodes, and electrodes 42, 46, and 50 may take the form of extendable and / or fixed spiral tip electrodes mounted within insulating electrode heads 52, 54, and 56, respectively. Each of electrodes 40, 42, 44, 46, 48, and 50 may be electrically coupled to a respective one of the coil conductors within the lead body of its associated lead 18, 20, 23, and thereby to a respective one of the electrical contacts on the proximal end of leads 18, 20, 23.

[0065] Electrodes 40, 42, 44, 46, 48, and 50 can sense electrical signals associated with depolarization and repolarization of heart 12. The electrical signals are conducted to IMD 16 via corresponding leads 18, 20, 23. In some examples, IMD 16 also delivers pacing pulses via electrodes 40, 42, 44, 46, 48, 50 to cause depolarization of cardiac tissue of heart 12. In some examples, such as Figure 2B As shown, IMD 16 may include one or more housing electrodes (such as housing electrode 58) that may be integrally formed with an outer surface of an airtight housing 60 of IMD 16 or otherwise coupled to housing 60. In some examples, housing electrode 58 may be defined by a non-insulated portion of an outwardly facing portion of housing 60 of IMD 16. Other separations between the insulated portion and the non-insulated portion of housing 60 may be used to define two or more housing electrodes. In some examples, housing electrode 58 includes substantially all of housing 60. Any of electrodes 40, 42, 44, 46, 48, 50 may be used in combination with housing electrode 58 for unipolar sensing or pacing, or for bipolar sensing with two electrodes in the same pacing lead. In one or more embodiments, housing 60 may enclose a stimulation generator that generates cardiac pacing pulses and defibrillation or cardioversion shocks (see Figure 5 ), and a sensing module for monitoring the patient's heart rhythm.

[0066] Leads 18, 20, 23 may also include elongated electrodes 62, 64, 66, respectively, which may take the form of coils. IMD 16 may deliver defibrillation shocks to heart 12 via any combination of elongated electrodes 62, 64, 66 and housing electrode 58. Electrodes 58, 62, 64, 66 may also be used to deliver cardioversion pulses to heart 12. Electrodes 62, 64, 66 may be made of any suitable conductive material, such as, but not limited to, platinum, platinum alloys, or other materials known to be useful in implantable defibrillation electrodes.

[0067] The pressure sensor 38 may be coupled to one or more coil conductors within the lead 18. Figure 2B In some examples, pressure sensor 38 is located on lead 18 more distally than elongated electrode 62. In other examples, pressure sensor 38 may be located closer to elongated electrode 62, rather than distal to electrode 62. Furthermore, in other examples, pressure sensor 38 may be coupled to another of leads 20, 23, or to leads other than leads 18, 20, 23 that carry stimulation and sensing electrodes. Additionally, in some examples, pressure sensor 38 may be a stand-alone device implanted within heart 12, such as within the ventricular septum that separates right ventricle 28 from left ventricle 32, or within the atrial septum that separates right atrium 26 from left atrium 33. In such examples, pressure sensor 38 may communicate wirelessly with IMD 16.

[0068] Figure 2C to Figure 2D are conceptual diagrams showing additional examples of a dual-chamber treatment system 70 and a single-chamber treatment system 71, respectively. The treatment system 70 is similar to FIG. 2A to FIG. 2B Therapy system 70 is similar to therapy system 10, but includes two leads 18, 23 instead of three leads. Therapy system 70 may utilize an IMD 16 configured to deliver or perform dual-chamber pacing. Leads 18, 23 are implanted in the right ventricle 28 and right atrium 26 to pace one or more portions of the cardiac conduction system, such as the His bundle or one or both bundle branches, respectively. Therapy system 71 is similar to FIG. 2A to FIG. 2B Therapy system 10 of the present invention is similar to that of the present invention, but includes a single lead 23 instead of three leads. Therapy system 71 may utilize an IMD 16 configured to deliver or perform single chamber pacing. Lead 23 is implanted in right atrium 26 to pace one or more portions of the cardiac conduction system, such as the bundle of His or one or both bundle branches, respectively.

[0069] The cardiac conduction system pacing lead 23 may include an electrode 50 in the form of a spiral (also referred to as a spiral electrode) that may be positioned near, adjacent, adjacent, or in an area or portion of the cardiac conduction system, such as, for example, the ventricular septum, Koch's triangle, the bundle of His, left and right bundle branch tissue, and / or right bundle branch tissue. The cardiac conduction system pacing lead 23 may be configured as a bipolar lead or a quadripolar lead that may be used with a pacemaker device, a CRT-P device, or a CRT-ICD.

[0070] FIG. 3A to FIG. 3B A patient's heart 12 is shown implanted with implantable medical electrical leads 723 coupled to an IMD 716 for delivering bundle branch pacing in accordance with one example of an IMD system 710 . Figure 3B yes Figure 3A 723 in a patient's heart 12. In some embodiments, electrical lead 723 may be the only lead implanted in heart 12. In other embodiments, as discussed herein, there may be multiple leads implanted in heart 12. For example, one or more implantable electrodes may include a pacing electrode that can be implanted proximate to the cardiac conduction system, or can be implanted in the ventricular septum (VS) to deliver cardiac conduction system pacing therapy.

[0071] In one embodiment, lead 723 can be configured for dual-bundle pacing and lead 723 can be used with FIG. 2A to FIG. 2B ) except that lead 723 is implanted near a bundle branch in the ventricular septum (VS) from the right ventricle 28, rather than, for example, the bundle of His 13. As shown, lead 723 is implanted in the septal wall or ventricular septum from the right ventricle 28 toward the left ventricle 32. Lead 723 may not pierce the wall of the left ventricle 32 or extend into the left ventricular cavity. Electrode 752 and tissue-piercing electrode 761 may be disposed on a distal end portion of lead 723, which may also be described as a shaft. Electrode 752 and tissue-piercing electrode 761 may be similar to those shown in FIG. Figure 2B The electrodes shown are the same or similar to the tissue-piercing electrode 50, except that the electrode 752 is configured as a cathode electrode to sense or pace the right bundle branch and the electrode 761 is configured to sense or pace the left bundle branch, for example, during dual bundle branch pacing. Thus, the electrode 752 can be implanted near the right bundle branch 8b and the electrode 761 can be implanted near the left bundle branch 8a. The electrode 761 can be described as a unipolar cathode electrode that can be implanted on the left side of the patient's ventricular septum. The electrode 752 can be described as a unipolar cathode electrode that can be implanted on the right side of the patient's ventricular septum.

[0072] During dual bundle branch pacing, both electrode 752 and electrode 761 can each deliver cathodic pulses to achieve synchronized activation or excitation of the right bundle branch 8b and the left bundle branch 8a, which can result in synchronized activation of the right ventricle 28 and the left ventricle 32. In some embodiments, the pulses can be delivered simultaneously to achieve synchronization. In other embodiments, the pulses can be delivered with a delay to achieve synchronization.

[0073] Although lead 723 is shown as being configured for dual bundle branch pacing using electrodes 752, 761, it should be understood that lead 723 or a lead similar thereto may be considered herein to include only one of electrode 752 and electrode 761 and, therefore, be configured to deliver cardiac conduction system pacing therapy to only one of the right bundle branch and the left bundle branch.

[0074] In addition, lead 723 may include a right atrial electrode 770 disposed along lead 723 closer to electrode 752 and electrode 761. Right atrial electrode 770 may be positioned in or near right atrium 26 and may serve as an anode for cathodic pulses from electrode 752 and / or electrode 761. In addition, right atrial electrode 770 may provide atrial sensing to, for example, sense atrial depolarization or activation, sense or detect atrial fibrillation, etc. Although lead 723 is shown to include right atrial electrode 770, it should be understood that lead 723 may not include right atrial electrode 770, but may include only one or both of electrode 752 and electrode 761.

[0075] In addition, the device system 710 may include Figure 3B A mechanical cardiac activation sensor 751 is shown coupled to the lead 723. As shown in this embodiment, when the distal end of the lead 723 is implanted through the right ventricle 28 into the ventricular septum, the mechanical cardiac activation sensor 751 can be positioned in the right ventricle 28. The mechanical cardiac activation sensor 751 can be a motion sensor (e.g., an accelerometer) and / or a heart sound sensor (e.g., a microphone) that can be used to determine atrial activation or depolarization (e.g., atrial drive) for use in delivering atrioventricular timed cardiac conduction system pacing therapy. In other words, the device system 710 can be configured to monitor the mechanical activity of the patient's heart using a mechanical cardiac activation sensor, determine atrial activation based on the monitored mechanical activity, and deliver cardiac conduction system pacing using a cardiac conduction system pacing electrode based on the determined atrial activation. In addition, in one or more embodiments, the mechanical cardiac activation sensor 751 can be located in a housing of the IMD 716 that is not located within the patient's heart. For example, the housing of the IMD 716 can be positioned subcutaneously with the patient's body. In addition, if the device system 710 includes a leadless device, the mechanical cardiac activation sensor 751 may be located in a housing of the leadless device implanted in the right ventricle 28.

[0076] In addition, atrial activation determined using the mechanical heart activation sensor 751 can be used in conjunction with atrial activation determined using near-field or far-field electrical activity. In at least one embodiment, atrial activation determined using the mechanical heart activation sensor 751 can be used to confirm atrial activation determined using near-field or far-field electrical activity, or vice versa.

[0077] Figure 3CA graph showing a heart sound signal varying over time is depicted in As shown, atrial activation is indicated by ellipse 399 (eg, depolarization, atrial drive, heart sound A4 or S4, etc.).

[0078] Figure 4A is a conceptual diagram of an exemplary system 801 that includes an IMD or pacemaker 814 configured as a multi-chamber pacemaker, a right atrial pacing and sensing lead 919, a coronary sinus lead 992, and a cardiac conduction system pacing lead 918 configured for delivering bundle branch pacing. The IMD 814 is shown coupled to the right atrial lead 919 carrying a pacing tip electrode 936 and a proximal ring electrode 938 that can be used to sense right atrial signals and deliver atrial pacing to the right atrium. The coronary sinus lead 992 can be advanced into the RA, through the coronary sinus ostium and into the cardiac veins of the left ventricle to position electrodes 94a, 94b, 94c, 94d (collectively referred to as "CS electrodes 94") on the epicardium along the left ventricular myocardium to sense electrocardiographic signals and pace the left ventricular myocardium. Coronary sinus lead 992 is shown as a quadripolar lead carrying four electrodes 94a-94d that can be selected from a variety of bipolar pacing electrode pairs to pace left ventricular myocardial tissue and sense left ventricular epicardial electrocardiogram signals. One of CS electrodes 94 can be selected in conjunction with pacemaker housing 815 or coil electrode 935 to deliver unipolar left ventricular myocardial pacing and / or sense unipolar ventricular electrocardiogram signals.

[0079] In this example, the IMD 814 may be capable of delivering a high voltage cardioversion / defibrillation shock therapy for cardioversion or defibrillation of the heart in response to detecting a ventricular tachyarrhythmia. Thus, the lead 918 is shown as carrying a coil electrode 935 for delivering a high voltage shock pulse. In various examples, one or more coil electrodes may be included along one or more of the leads 918, 919, or 992. A coil electrode such as the coil electrode 935 may be selected in a unipolar pacing electrode vector with any of the lead-based tip or ring electrodes 932, 934, 936, 938, or 94 to sense a unipolar electrocardiogram signal for analyzing and determining ventricular conduction conditions. In some cases, the coil electrode 935 may be used together with the housing 815 to sense a near-field electrocardiogram signal for determining atrial depolarization or activation, etc.

[0080] When pacing lead 918 is positioned for delivering bundle branch pacing of one or both bundle branches, cardiac conduction system pacing therapy can be combined with conventional ventricular myocardial pacing of the left ventricle using coronary sinus lead 992 to correct left ventricular conduction delays and achieve electrical and mechanical synchronization of the left and right ventricles. Thus, in some examples, one or more processors, one or more processing circuits, or computing devices of IMD 814 can select cardiac conduction system pacing therapy plus conventional left ventricular myocardial pacing therapy, which conventional left ventricular myocardial pacing therapy includes, for example, single bundle branch pacing or dual bundle branch pacing (e.g., using lead 918) combined with left ventricular myocardial pacing using coronary sinus lead 992. Figure 4B is another basically similar Figure 4A Conceptual diagram of exemplary treatment system 802 of exemplary treatment system 801 , except that system 802 does not include coronary sinus lead 992 .

[0081] Figure 2A The configuration of the treatment system 10 shown in FIG. 4 is merely an example. In other examples, the treatment system may include epicardial leads and / or patch electrodes instead of or in addition to the Figure 2A 4, or other configurations shown or described herein or incorporated by reference. In addition, IMD 16, 716, 814 need not be implanted in patient 14. Thus, it should be appreciated that the exemplary treatment systems described herein may include any suitable number of leads coupled to IMD 16, 716, 814, and each of the leads may extend to any location within or near heart 12. For example, the exemplary treatment systems may include locations such as FIG. 2A to FIG. 2C and Figure 4A The three transvenous lines shown are located as FIG. 3A to FIG. 3B A single transvenous line or position as shown Figure 2D and 4B Two transvenous leads are shown.

[0082] Figure 5 is a functional block diagram of an exemplary configuration of IMD 16. FIG. 2A to FIG. 2D The system shown in Figure 5 16, however, it should be understood that IMDs 716, 814 may be substantially similar to IMD 16, and therefore, IMDs 716, 814 may include any or all of the functionality described with respect to the functional block diagram of IMD 16.

[0083] The IMD 16 includes a processor 80, a memory 82, a stimulation generator 84 (e.g., an electrical pulse generator or signal generating circuit), a sensing module 86 (e.g., a 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 housed 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 the 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, nonvolatile, magnetic, optical, or electrical medium, such as a random access memory (RAM), a read-only memory (ROM), a nonvolatile RAM (NVRAM), an electrically erasable programmable ROM (EEPROM), a flash memory, or any other digital medium.

[0084] The processor 80 may include any one or more of the following: a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or an equivalent discrete or integrated logic circuit. In some examples, the 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) and other discrete or integrated logic circuit systems. The functions of the processor 80 attributed to this article may be embodied as software, firmware, hardware, or any combination thereof. The processor 80 controls the stimulation generator 84 to select a treatment mode (e.g., one or more of the inhibition pacing mode, ventricular fusion pacing mode, atrioventricular synchronization pacing mode, atrial fibrillation pacing mode, etc.), and delivers stimulation therapy to the heart 12 according to the selected pacing mode and various sensing (e.g., atrial depolarization or activation, ventricular atrial depolarization or activation, heart rate, P wave to R wave interval, etc.) that can be stored in the memory 82. Specifically, processor 80 may control stimulation generator 84 to deliver electrical pulses having an amplitude, pulse width, frequency, or electrode polarity specified by the selected one or more treatment programs and treatment modes.

[0085] In some embodiments, lead 23 may be operably coupled to electrode 61 that may be used to monitor or pace the right atrium. Stimulation generator 84 may be electrically coupled to electrodes 40, 42, 44, 46, 48, 50, 58, 61, 62, 64, and 66, for example, via conductors of respective leads 18, 20, 23 or, in the case of housing electrode 58, via electrical conductors disposed within housing 60 of IMD 16. Stimulation generator 84 may be configured to generate and deliver electrical stimulation therapy to heart 12. For example, stimulation generator 84 may deliver a defibrillation shock to heart 12 via at least two of electrodes 58, 62, 64, 66. Stimulation generator 84 may deliver pacing pulses via ring electrodes 40, 44, 48 coupled to leads 18, 20, 23, respectively, and / or via helical electrodes 42, 46, 50 of leads 18, 20, or 23, respectively. Cardiac conduction system pacing therapy may be delivered via cardiac conduction system lead 23 connected to an atrial, right ventricular, or left ventricular connection port of connector block 34. In some embodiments, cardiac conduction system pacing therapy may be delivered via leads 18 and / or 23. In some examples, stimulation generator 84 delivers pacing, cardioversion, or defibrillation stimulation in the form of electrical pulses. In other examples, 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.

[0086] Stimulation generator 84 may include a switch module, and processor 80 may use the switch module to select which of the available electrodes is used to deliver a defibrillation shock or pacing pulse, for example, via a data / address bus. The switch module may include a switch array, a switch matrix, a multiplexer, or any other type of switching device suitable for selectively coupling stimulation energy to selected electrodes.

[0087] The sensing module 86 monitors signals from at least one of the electrodes 40, 42, 44, 46, 48, 50, 58, 61, 62, 64, or 66 to monitor the electrical activity of the heart 12, such as via an electrocardiogram (ECG) signal and / or an electrogram (EGM). The sensing module 86 may also include a switch module to select which of the available electrodes is used to sense cardiac activity. In some examples, the processor 80 may select an electrode to act as a sensing electrode via a switch module within the sensing module 86, such as by providing a signal 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 a signal from the processor 80, the switch module may connect an output from a selected electrode to one of the sensing channels.

[0088] In some examples, one channel of sensing module 86 may include an R-wave amplifier that receives signals from electrodes 44, 46 used for pacing and sensing in the left ventricle 32 near heart 12. Another channel may include another R-wave amplifier that receives signals from electrodes 40, 42 used for pacing and sensing in the right ventricle 28 of heart 12. In some examples, the R-wave amplifier may take the form of an automatic gain control amplifier that provides an adjustable sensing threshold based on the R-wave amplitude of the measured heart rate.

[0089] Additionally, in some examples, one channel of the sensing module 86 may include a P-wave amplifier that receives signals from electrodes 48, 50 that are used for pacing and sensing in the right atrium 26 of the heart 12. In some examples, the P-wave amplifier may take the form of an automatic gain control amplifier that provides an adjustable sensing threshold based on the P-wave amplitude of the measured heart rate. Examples of R-wave amplifiers and P-wave amplifiers are described in U.S. Patent No. 5,117,824, entitled "APPARATUS FOR MONITORING ELECTRICAL PHYSIOLOGIC SIGNALS," issued to Keimel et al. on June 2, 1992, which is incorporated herein by reference in its entirety. Other amplifiers may also be used. In addition, in some examples, one or more of the sensing channels of the sensing module 86 may be selectively connected to the shell electrode 58 or the slender electrodes 62, 64 or 66, together with or in place of one or more of the electrodes 40, 42, 44, 46, 48 or 50, for example for unipolar sensing of R waves or P waves in any of chambers 26, 28 or 32 of the heart 12.

[0090] In some examples, the sensing module 86 includes a channel including an amplifier having a relatively wider passband than an R wave amplifier or a P wave amplifier or a high resolution amplifier having a relatively narrow passband for recording of His bundle or bundle branch potentials. Signals from selected sensing electrodes selected for connection to this broadband amplifier may be provided to a multiplexer and thereafter converted by an analog-to-digital converter into a multi-bit digital signal 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 the memory 82 to detect and classify the patient's heart rhythm from the electrical signals. The processor 80 may detect and classify the patient's heart rhythm by employing any of numerous signal processing methods known in the art.

[0091] If the IMD 16 is configured to generate and deliver pacing pulses to the heart 12, the processor 80 may include a pacemaker timing and control module, which may be embodied in hardware, firmware, software, or any combination thereof. The pacemaker timing and control module may include a dedicated hardware circuit (such as an ASIC) separate from other 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 an ASIC. The pacemaker timing and control module may include a programmable counter that controls basic time intervals associated with DDD, VVI, DVI, VDD, AAI, DDI, DDDR, VVIR, DVIR, VDDR, AAIR, DDIR, and other single-chamber and dual-chamber pacing modes. In the aforementioned pacing modes, "D" may indicate dual chamber, "V" may indicate ventricle, "I" may indicate inhibited pacing, and "A" may indicate atrium. The first letter in the pacing mode may indicate the chamber being paced, the second letter may indicate the chamber in which the electrical signal is sensed, and the third letter may indicate the chamber in which the response to the sensing is provided.

[0092] The intervals defined by the pacemaker timing and control module may include atrial and ventricular pacing escape intervals, refractory periods during which sensed P and R waves are ineffective for restarting the timing of the escape interval, and pulse widths of pacing pulses. As another example, the pacemaker timing and control module may define blanking periods and provide signals from the sensing module 86 to blank one or more channels, such as amplifiers, for a period of time during and after delivery of electrical stimulation to the heart 12. The duration of these intervals may be determined by the processor 80 in response to data stored in the memory 82. The pacemaker timing and control module may also determine the amplitude of the cardiac pacing pulses.

[0093] During pacing, an escape interval counter within the pacemaker timing / control module may be reset when R and P waves are sensed. The stimulation generator 84 may include a pacemaker output circuit that is selectively coupled, for example, via a switch module, to any combination of electrodes 40, 42, 44, 46, 48, 50, 58, 61, 62, or 66 suitable for delivering bipolar or unipolar pacing pulses to one of the chambers of the heart 12. The processor 80 may reset the escape interval counter when a pacing pulse is generated by the stimulation generator 84, and thereby control the basic timing of cardiac pacing functions including anti-tachyarrhythmia pacing.

[0094] In some examples, processor 80 may operate as an interrupt driven device and respond to interrupts from a pacemaker timing and control module, where the interrupts may correspond to the occurrence of sensed P and R waves and the generation of cardiac pacing pulses. Any necessary mathematical calculations are performed by processor 80, and any updates to values ​​or intervals controlled by the pacemaker timing and control module of processor 80 may occur following such interrupts. A portion of memory 82 may be configured as a plurality of recirculating buffers capable of maintaining a series of measured intervals that may be analyzed by processor 80 in response to the occurrence of a pacing or sensing interruption to determine whether the patient's heart 12 is currently exhibiting an atrial or ventricular tachyarrhythmia.

[0095] Telemetry module 88 includes any suitable hardware, firmware, software, or any combination thereof, for communicating with another device, such as programmer 24. Telemetry module 88 may receive downlink telemetry from programmer 24 and send uplink telemetry to the programmer, under the control of processor 80, via an antenna, which may be internal and / or external. Processor 80 may provide data to be uplinked to programmer 24 and control signals for telemetry circuitry within telemetry module 88, for example, via an address / data bus. In some examples, telemetry module 88 may provide received data to processor 80 via a multiplexer.

[0096] The various components of IMD 16 are coupled to a power source 90, which may include a rechargeable or non-rechargeable battery. Non-rechargeable batteries may be selected to last for several years, while rechargeable batteries may be inductively charged from an external device, for example, on a daily or weekly basis.

[0097] The example systems, devices, and methods described herein may provide adaptive cardiac conduction system pacing therapy that may select an appropriate cardiac conduction system pacing therapy mode based on one or more conditions or parameters measured from a patient.

[0098] Figure 6 The diagram in Figure 2 shows Figure 5 An exemplary method 100 of adaptive cardiac conduction system pacing therapy utilized by an IMD and delivering such adaptive cardiac conduction system pacing therapy is provided. As shown, the method 100 may include delivering cardiac therapy 102 and monitoring electrical activity 104. In particular, the method 100 may be performed by an IMD sensing electrical activity of a patient's heart 104 using one or more implanted electrodes and delivering cardiac therapy to the patient's heart 102.

[0099] In a single chamber embodiment, one or more electrodes may include a cardiac conduction system pacing electrode that can be positioned proximate to a portion of the patient's cardiac conduction system to deliver cardiac conduction system pacing therapy to the portion of the patient's cardiac conduction system. The single chamber embodiment may be configured to deliver four or more different cardiac conduction system pacing therapy modes, such as, for example, an inhibition pacing mode, an atrioventricular synchronization pacing mode, a ventricular fusion pacing mode, and an atrial fibrillation pacing mode, which will be further described herein.

[0100] In a dual chamber embodiment, one or more electrodes may include a right atrial electrode positionable in the right atrium of the patient to sense electrical activity in the right atrium and deliver pacing therapy to one or more of the right atrium, and a cardiac conduction system pacing electrode positionable proximate a portion of the patient's cardiac conduction system to deliver cardiac conduction system pacing therapy to that portion of the patient's cardiac conduction system. The dual chamber embodiment may be configured to deliver four or more different cardiac conduction system pacing therapy modes, such as, for example, an inhibition pacing mode, an atrioventricular synchronization pacing mode, a ventricular fusion pacing mode, and an atrial fibrillation pacing mode, which will be further described herein.

[0101] In a three-chamber embodiment, one or more electrodes may include a right atrial electrode positionable in the right atrium of the patient to sense electrical activity of the right atrium and deliver pacing therapy to one or more of the right atrium, a left ventricular electrode positionable in the coronary sinus to sense electrical activity of the left ventricle and deliver pacing therapy to one or more of the left ventricle, and a cardiac conduction system pacing electrode positionable proximate a portion of the patient's cardiac conduction system to deliver cardiac conduction system pacing therapy to that portion of the patient's cardiac conduction system. The three-chamber embodiment may be configured to deliver three or more different cardiac conduction system pacing therapy modes, such as, for example, an atrioventricular synchronization pacing mode, a ventricular fusion pacing mode, and an atrial fibrillation pacing mode, which will be further described herein. Dual-chamber and triple-chamber adaptive cardiac conduction system pacing therapies may be described in a patent application entitled “Adaptive Cardiac Conduction System Pacing Therapy for Multi-Chamber Devices” filed on September 30, 2022, the same day as the present application, which patent application corresponds to Medtronic file number A0007988US01 and is incorporated by reference in its entirety.

[0102] It should be understood that although the exemplary systems, devices, and methods described herein generally relate to single-chamber embodiments, such systems, devices, and methods may also be performed or carried out using dual-chamber or triple-chamber embodiments when, for example, the other chamber functions are not used. In other words, any process described for a single-chamber embodiment may also be used in dual-chamber and triple-chamber embodiments.

[0103] The method 100 may include delivering cardiac conduction system pacing therapy 102 according to one of the modes supported by the provided cardiac therapy. During the delivery of therapy 102, cardiac electrical activity 104 may be monitored using one or more of the electrodes. In particular, one or more of intrinsic or paced atrial depolarization or activation and intrinsic or paced ventricular depolarization or activation may be sensed in the monitored electrical activity 104 for use by the cardiac therapy 102.

[0104] Periodically, cardiac conduction system pacing therapy being delivered may be paused 106, and a cardiac conduction system pacing therapy pacing mode may be selected 108. In other words, cardiac conduction system pacing therapy 102 may be temporarily halted or inhibited 106 so that intrinsic cardiac electrical activity may be monitored for selection of a cardiac conduction system pacing therapy mode 108 to be utilized. In at least one embodiment, the atrioventricular delay may be set or configured to a time value that is long enough to ensure intrinsic conduction to the ventricles for intrinsic depolarization or activation. In other words, the atrioventricular delay may be extended or prolonged to allow intrinsic ventricular activation, but still deliver ventricular pacing if no intrinsic ventricular activation occurs (e.g., due to AV block, etc.). References herein Figures 7 and 8 Options 108 for cardiac conduction system pacing therapy for a single chamber embodiment are described.

[0105] The cardiac conduction system pacing therapy may be selected 108 as one of an inhibition pacing mode 110 , an atrioventricular synchronization pacing mode 112 , a ventricular fusion pacing mode 114 , and an atrial fibrillation pacing mode 116 .

[0106] The inhibited pacing mode 110 (also referred to as VDI or VDIR) can be described as delivering cardiac conduction system pacing when intrinsic ventricular activation does not occur after atrial activation. More specifically, cardiac conduction system pacing can be delivered 110 in response to termination of inhibited AV delay after atrial activation without sensing intrinsic ventricular activation, or in response to maintenance of a baseline heart rate during the inhibited pacing mode. In other words, during the inhibited pacing mode 110, atrial depolarization or activation sensing can trigger or initiate the onset of inhibited AV delay, and the inhibited pacing mode can be selected to allow intrinsic ventricular depolarization or activation. If intrinsic ventricular depolarization or activation occurs before termination of inhibited AV delay, cardiac conduction system pacing therapy is withheld or not delivered during the cardiac cycle. If intrinsic ventricular depolarization or activation does not occur before termination of inhibited AV delay, cardiac conduction system pacing therapy can be delivered during the cardiac cycle to initiate depolarization or activation of one or both of the ventricles. The suppressed AV delay may be between about 220 milliseconds (ms) and about 350 ms. In at least one embodiment, the suppressed AV delay may be 250 ms.

[0107] In addition, the inhibit pacing mode 110 may also be configured to deliver cardiac conduction system pacing therapy to maintain a selected or desired heart rate (or R-wave to R-wave interval). Thus, during the inhibit pacing mode 110, a previous ventricular depolarization or activation sensing may trigger or initiate the start of an inhibit R-wave to R-wave interval, and the inhibit pacing mode may be selected to maintain a selected or desired heart rate or R-wave to R-wave interval. If intrinsic ventricular depolarization or activation occurs before the termination of the inhibit R-wave to R-wave interval, cardiac conduction system pacing therapy is withheld or not delivered during the cardiac cycle. If intrinsic ventricular depolarization or activation does not occur before the termination of the inhibit R-wave to R-wave interval, cardiac conduction system pacing therapy may be delivered during the cardiac cycle to initiate depolarization or activation of one or both ventricles of the ventricles. The inhibit R-wave to R-wave interval may be between about 1 second and about 1.75 seconds. In at least one embodiment, the inhibit R-wave to R-wave interval is 1.5 seconds (corresponding to a heart rate of 40 beats per minute).

[0108] The AV synchronization pacing mode 112 can be described as delivering cardiac conduction system pacing in response to the termination of a fixed AV delay following atrial activation. In other words, during the AV synchronization pacing mode 112, atrial depolarization or activation sensing can trigger or initiate the start of the fixed AV delay, and the AV synchronization pacing mode can be selected to allow or provide optimal AV synchronization. At the termination of the fixed AV delay, cardiac conduction system pacing therapy can be delivered within the cardiac cycle to initiate depolarization or activation of one or both ventricles of the heart. The fixed AV delay can be between about 200 ms and about 300 ms. In at least one embodiment, the fixed AV delay can be 220 ms.

[0109] The ventricular fusion pacing mode 114 can be described as the delivery of cardiac conduction system pacing to initiate cardiac depolarization at the same time or substantially the same time as the intrinsic ventricular activation. In other words, during the ventricular fusion pacing mode 114, atrial depolarization or activation sensing can trigger or initiate the start of a fusion AV delay, and the ventricular fusion pacing mode can be selected to synchronize the cardiac depolarization initiated by the cardiac conduction system pacing with the intrinsic ventricular activation. At the termination of the fusion AV delay, cardiac conduction system pacing therapy can be delivered within the cardiac cycle to initiate depolarization or activation of one or both ventricles of the ventricles. In order to achieve ventricular fusion, one or more intrinsic AV delays can be monitored or measured, and the fusion AV delay can be determined as a selected percentage of the shortest monitored intrinsic AV delay. In particular, when delivering left bundle branch pacing, the monitored intrinsic AV is measured from atrial sensing or pacing to left bundle branch sensing (for example, the left bundle branch can be paced using the same electrode or another electrode positioned near the left bundle branch can be used to sense or monitor the left bundle branch sensing). The selected percentage may be between about 50% and about 90%. In one embodiment, the selected percentage is about 70%.

[0110] The atrial fibrillation pacing mode 116 may include an atrial fibrillation suppression pacing mode, effective cardiac resynchronization therapy pacing during the atrial fibrillation mode, and a conduction atrial fibrillation response (CAFR) mode. The atrial fibrillation suppression pacing mode (also known as VVI or VVIR) may be described as the delivery of cardiac conduction system pacing when intrinsic ventricular activation does not occur after a previous ventricular activation. More specifically, cardiac conduction system pacing may be delivered in response to the termination of a suppression VV delay after a previous ventricular activation without sensing intrinsic ventricular activation, or in response to the maintenance of a baseline heart rate (e.g., such as 50 beats per minute). In other words, during the atrial fibrillation suppression pacing mode, ventricular depolarization or activation sensing may trigger or initiate the start of a suppression ventricular delay, and the atrial fibrillation suppression pacing mode may be selected to allow intrinsic ventricular depolarization or activation. If intrinsic ventricular depolarization or activation occurs before the termination of the suppression ventricular delay, cardiac conduction system pacing therapy is withheld or not delivered within the cardiac cycle. If intrinsic ventricular depolarization or activation does not occur prior to termination of the inhibited ventricular delay, cardiac conduction system pacing therapy may be delivered during the cardiac cycle to initiate depolarization or activation of one or both ventricles.

[0111] Effective cardiac resynchronization therapy pacing during atrial fibrillation mode can generally be described as a pacing mode that automatically changes the pacing rate to increase the effectiveness of cardiac resynchronization therapy during atrial fibrillation. Typically, if a beat of ventricular pacing is determined to be ineffective, the pacing rate can be increased, and if a beat of ventricular pacing is determined to be effective, the pacing rate can be reduced. An exemplary effective cardiac resynchronization therapy pacing mode during atrial fibrillation can be described in U.S. Provisional Patent Application Serial No. 63 / 393,072, entitled "Advanced Pacing Delay During Atrial Fibrillation," filed by Stadler et al. on July 28, 2022, which is incorporated by reference in its entirety.

[0112] CAFR modes can generally be described as pacing modes that provide low, medium, and high response values ​​to adjust the amount by which the pacing rate is increased on a beat-to-beat basis. For example, the ventricular pacing rate can be adjusted slightly up or down within each cardiac cycle. In particular, if the current cardiac cycle ends with ventricular pacing, the pacing rate can be reduced, and if the current cardiac cycle ends with ventricular sensing, the pacing rate can be increased. Exemplary effective cardiac resynchronization therapy pacing modes during atrial fibrillation can be described in U.S. Patent No. 6,434,424, entitled "Regularization of Ventricular Rate During Atrial Tachyarrhythmia," filed on December 22, 1999 by Igel et al., which is incorporated by reference in its entirety.

[0113] As mentioned, cardiac conduction system pacing therapy pause 106 and cardiac conduction system pacing therapy pacing mode selection 108 may occur or be performed periodically. In other words, method 100 may be performed or performed at regular intervals or after the expiration of a recurring test period. The test period may be between about 2 minutes and about 24 hours. In addition, the test period may be different depending on the selected cardiac conduction system pacing therapy pacing mode. For example, if the inhibition pacing mode 110 is selected, the test period may be 10 hours. In addition, in at least one embodiment, if the inhibition pacing mode 110 is selected, the QRS complex width may be rechecked in response to a high heart rate (e.g., a heart rate above a heart rate threshold). In addition, for example, if the atrioventricular synchronization pacing mode 112 is selected, the test period may be started at 16 minutes, then reduced to 5 minutes for the second test period, then reduced to 4 minutes for the third test period, and then reduced to 2 minutes for the fourth and final test period. Also, for example, if the ventricular fusion pacing mode 114 is selected, the test period may be initiated at 16 minutes, then reduced to 5 minutes for the second test period, then reduced to 4 minutes for the third test period, and then reduced to 2 minutes for the fourth and final test period. Still further, for example, if the atrial fibrillation pacing mode 116 is selected, the test period may be initiated at 512 minutes, then reduced to 256 minutes for the second test period, then reduced to 128 minutes for the third test period, and continuously reduced by half.

[0114] One embodiment of the cardiac conduction system pacing therapy pause 106 and cardiac conduction system pacing therapy pacing mode selection 108 frequencies is shown in Table 1. As shown, Table 1 summarizes the frequencies of the interval measurements for each of the inhibition pacing mode 110, the atrioventricular synchronization pacing mode 112, the ventricular fusion pacing mode 114, and the atrial fibrillation pacing mode 116. Sometimes, more than one measurement may be used to confirm that a change has occurred. For example, the P wave width and QRS width may be stored in a buffer of the three most recent measurements, and the median of the three highest measurements may be the result used for all comparisons. In addition, the P wave to R wave interval result may sometimes be used as a single measurement result and sometimes as a combination of measurements.

[0115]

[0116] Table 1.

[0117] *The hysteresis described here applies to the transition from a narrow to a wide QRS pattern in atrial fibrillation pacing mode.

[0118] If the A-fib pacing mode is entered from the inhibition pacing mode, the A-fib pacing mode starts with a narrow QRS pattern. If the A-fib pacing mode is entered from the atrioventricular synchronization pacing mode, the A-fib pacing mode starts with a wide QRS pattern. If the A-fib pacing mode is entered from the ventricular fusion pacing mode, ≤110ms is the threshold for the narrow QRS pattern in the A-fib pacing mode.

[0119] exist Figure 7 The following diagram depicts the selection of an exemplary single chamber device when used. Figure 6 An exemplary method 700 for a cardiac conduction system pacing mode of a patient's heart may include a cardiac conduction system pacing electrode that can be positioned proximate to a portion of a patient's heart to deliver cardiac conduction system pacing therapy to the portion of the patient's heart. In one embodiment, the cardiac conduction system pacing electrode is positioned proximate to the His bundle and implanted in the right atrium. In another embodiment, the cardiac conduction system pacing electrode is positioned proximate to the left bundle branch and implanted in the right ventricle. The single chamber device may include leads or may be a leadless device. For example, a single chamber device may include a Figure 2D Extending in the right atrium as shown or FIG. 3A to FIG. 3B A single lead extending through the right atrium in the right ventricle is shown. For example, a single chamber device may include Figure 2D Implanted in the right atrium as shown or FIG. 3A to FIG. 3B A leadless device is shown implanted in the right ventricle.

[0120] The method 700 may include performing a conduction test 701 during a pause in delivering cardiac conduction system pacing therapy to determine one or more metrics using the monitored electrical activity. In particular, the electrical activity may be far-field electrical activity monitored using one or more electrodes positioned outside the right atrium (such as, for example, near the His bundle, the left bundle branch, in the ventricular septum, in the right ventricular blood pool, etc.). More specifically, in at least one embodiment, the atrioventricular delay may be set or configured to ensure intrinsic conduction to the ventricles for a time value for intrinsic depolarization or activation. The conduction test 701 may be performed for a single cardiac cycle or over a single cardiac cycle. In other embodiments, the conduction test 701 may be performed for two or more cardiac cycles (e.g., cardiac conduction system pacing therapy may be paused for two or more cardiac cycles), but still a relatively small number of cardiac cycles, such as, for example, less than 10.

[0121] The one or more metrics may include at least one atrial fibrillation indicator, QRS complex width, and P wave to R wave interval. The at least one atrial fibrillation indicator may include one or more of R wave to R wave interval consistency, T wave to P wave interval consistency, and far-field P wave morphology. The one or more metrics may then be utilized to determine which cardiac conduction system pacing therapy may be selected.

[0122] For example, as shown, the inhibited pacing mode 702 may be selected in response to at least one atrial fibrillation metric being consistent, a narrow QRS complex width, and a short P-wave to R-wave interval.

[0123] Determining that at least one atrial fibrillation metric is consistent or has consistency may include comparing the monitored P wave morphology to a template P wave morphology. The template P wave morphology may be determined using a far-field P wave signal measured during normal heart operation using a vector from a cardiac conduction pacing electrode to an IMD housing, a vector from a right ventricular electrode to an IMD housing, a vector from a left bundle branch coil electrode to an IMD housing, and the like. Subsequent far-field P waves will be compared to the morphology monitored during normal heart operation. If the morphology changes abruptly, atrial fibrillation may be indicated. Additionally, determining that at least one atrial fibrillation metric is consistent or has consistency may include evaluating R-wave to R-wave and / or T-wave to R-wave consistency. In particular, for example, variability (e.g., standard deviation or mean absolute deviation between adjacent beats) may be established during a normal rhythm, and if R-wave to R-wave variability or T-wave to R-wave variability increases abruptly, atrial fibrillation may be indicated. The sudden increase may be that five of the five most recent beats or five of the seven most recent beats have a variability that is higher than the expected variability (e.g., the average variability of the previous 5 or 7 beats). In addition, the criteria for classifying atrial fibrillation should be based on, for example, one, two, or all three of these consistency metrics.

[0124] Determining whether the QRS complex width is narrow may utilize a QRS complex width threshold. For example, the QRS complex width determined from the monitored electrical activity during a pause in cardiac conduction system pacing therapy may be compared to a QRS complex width threshold. If the monitored QRS complex width is less than or equal to the QRS complex width threshold, it may be determined that the monitored QRS complex width is narrow. Conversely, if the monitored QRS complex width is greater than the QRS complex width threshold, it may be determined that the monitored QRS complex width is not narrow. The QRS complex width threshold may be between about 110 ms and about 150 ms. In one embodiment, the QRS complex width threshold is 120 ms. In addition, in one embodiment, when switching from one pacing mode to another, a selected amount of hysteresis may be utilized, for example, to limit rapid switching between pacing modes. For example, if the QRS complex width threshold may be 120 ms when selecting or determining a pacing mode, but may then be reduced to 110 ms to trigger or initiate switching to another pacing mode and / or exiting the current pacing mode.

[0125] A PR interval threshold may be used to determine whether the P wave to R wave interval is short. For example, the P wave to R wave interval determined by the monitored electrical activity during a pause in cardiac conduction system pacing therapy may be compared to the PR interval threshold. If the monitored P wave to R wave interval is less than or equal to the PR interval threshold, it may be determined that the monitored P wave to R wave interval is short. Conversely, if the monitored P wave to R wave interval is greater than the PR interval threshold, it may be determined that the monitored P wave to R wave interval is not short. The PR interval threshold may be between about 180 ms and about 230 ms. In one embodiment, the PR interval threshold is 200 ms. In addition, in one embodiment, when switching from one pacing mode to another, a selected amount of hysteresis may be used, for example, to limit rapid switching between pacing modes. For example, if the PR interval threshold may be 200 ms when selecting or determining a pacing mode, but then may be increased to 220 ms to trigger or initiate switching to another pacing mode and / or exit the current pacing mode.

[0126] In addition, each of one or more metrics, such as the P-wave to R-wave interval and the width of the QRS complex, may be monitored for a selected number of heartbeats or cardiac cycles, and each metric may be evaluated for a selected number of heartbeats to further delay. For example, the P-wave to R-wave interval may be compared to a PR interval threshold for a selected number (e.g., three) of the previous heartbeats, and a mode switch may not occur unless the P-wave to R-wave interval is less than (or equal to or greater than, depending on the mode switched to) the PR interval threshold for all of the selected number of previous beats.

[0127] During the inhibited pacing mode 702, if cardiac conduction system pacing therapy is delivered for at least a first number n of cardiac cycles or heartbeats of a second number of cardiac cycles or heartbeats, atrioventricular synchronous pacing 704 may be selected. The second number of cardiac cycles may be greater than the first number of cardiac cycles. In other words, atrioventricular synchronous pacing 704 may be selected if a selected percentage of the previous cardiac cycles were paced. In at least one embodiment, the atrioventricular synchronous pacing mode 704 may be selected if two of the last four cardiac cycles resulted in paced heartbeats.

[0128] Additionally, as shown, ventricular fusion pacing mode 703 may be selected in response to at least one atrial fibrillation metric being consistent, the QRS complex width not being narrow, and the P wave to R wave interval being short.

[0129] Still further, as shown, the AV synchronized pacing mode 704 may be selected in response to one of two sets of criteria being met or satisfied. First, the AV synchronized pacing mode 704 may be selected in response to at least one atrial fibrillation metric being consistent, the QRS complex width being narrow, and the P wave to R wave interval being not short. Second, the AV synchronized pacing mode 704 may be selected in response to at least one atrial fibrillation metric being consistent, the QRS complex width being not narrow, and the P wave to R wave interval being not short. In essence, the AV synchronized pacing mode 704 may be selected in response to at least one atrial fibrillation metric being consistent and the P wave to R wave interval being not short regardless of the state of the QRS complex width.

[0130] Finally, the long-term conduction test 705 may be selected in response to meeting or complying with one of two sets of criteria. First, the long-term conduction test 705 may be selected in response to at least one atrial fibrillation metric being inconsistent, the QRS complex width not being narrow, and the P-wave to R-wave interval being short. Second, the long-term conduction test 705 may be selected in response to at least one atrial fibrillation metric being inconsistent, the QRS complex width not being narrow, and the P-wave to R-wave interval not being short. In essence, the long-term conduction test 705 may be selected in response to at least one atrial fibrillation metric being inconsistent and the QRS complex width not being independent of the state of the P-wave to R-wave interval.

[0131] The long-term conduction test 705 can generally be described as being similar to the conduction test 701, but over a longer period of time or more cardiac cycles. For example, as described herein, the conduction test 701 can monitor intrinsic cardiac electrical activity within a single cardiac cycle or a relatively small number of cardiac cycles. The long-term conduction test 705 can suspend the delivery of cardiac conduction system pacing therapy and monitor intrinsic cardiac electrical activity for a long or extended period of time, i.e., more than a single cardiac cycle or a relatively small number of cardiac cycles. For example, the long-term or extended period of time may be 30 or more cardiac cycles or 30 seconds or longer. In at least one embodiment, the long-term or extended period of time may be less than or equal to 1 minute. Exemplary atrial fibrillation episode detection may be described in U.S. Patent No. 10,004,418, entitled "Atrial arrhythmia episode detection in a cardiac medical device" and issued on June 26, 2018, which is incorporated herein by reference in its entirety.

[0132] The at least one atrial fibrillation indicator may then be further analyzed over a chronic or extended period of time to confirm or verify whether the patient is experiencing atrial fibrillation.If it is confirmed that the patient is experiencing atrial fibrillation, the method 700 may select an atrial fibrillation pacing mode 706 .

[0133] If the patient is not confirmed to be experiencing atrial fibrillation, the atrioventricular synchronization pacing mode 704 may be selected in response to the QRS complex width not being narrow and the P wave to R wave interval not being short. If the patient is not confirmed to be experiencing atrial fibrillation, the ventricular fusion pacing mode 703 may be selected in response to the QRS complex width not being narrow and the P wave to R wave interval being short.

[0134] Figure 8 The diagram in Figure 2 shows Figure 5 The choice of single chamber device utilization Figure 6 to Figure 7 An exemplary method 200 for an atrial fibrillation pacing mode is provided. The method 200 may be performed or conducted periodically, such as, for example, every day or every 24 hours. At the beginning, the QRS complex width may be analyzed 201. If the QRS complex width is determined to be narrow 201, the method 200 may select an inhibited atrial fibrillation pacing mode 213 (also known as VVI or VVIR). In addition, the method 200 is configured to demonstrate that capture can occur as expected because loss of capture may result in a "runaway" pacing rate because the expected pacing will always be detected as invalid. In one or more embodiments, various processes may be used to determine whether consistent capture has occurred. For example, if at least 4 of 5 test beats have confirmed capture, effective CRT during the AF method may be performed for the next 24 hours.

[0135] In response to the QRS complex width being determined to be not narrow 201, a pacing capture threshold (PCT) test 202 may be performed. The pacing capture thresholds 204 may be compared to determine whether the pacing capture threshold is determined to be normal (indicating consistent capture) or high (indicating inconsistent capture). For example, the pacing capture threshold determined during the left bundle branch pacing capture threshold (PCT) test 202 may be compared to a normal pacing capture threshold. If the determined pacing capture threshold is greater than the normal pacing capture threshold, it may be determined that the pacing capture threshold is high, thereby indicating inconsistent capture. If the determined pacing capture threshold is less than or equal to the normal pacing capture threshold, it may be determined that the pacing capture threshold is normal, thereby indicating consistent capture. The normal pacing capture threshold may be between about 1 volt (V) and about 6V. In at least one embodiment, the normal pacing capture threshold is 3V.

[0136] If a high pacing capture threshold is determined indicating that consistent capture cannot be established, the method 200 may issue a warning 206 regarding loss of capture and select an ongoing atrial fibrillation responsive pacing mode 208. If a normal pacing capture threshold is determined indicating that consistent capture can be established, the method 200 may make a capture determination 210. If the capture is determined to be invalid, the method 200 may select an ongoing atrial fibrillation responsive pacing mode 208. Conversely, if the capture is determined to be valid, the method 200 may select an effective cardiac resynchronization therapy pacing during an atrial fibrillation mode 212.

[0137] One or more cardiac conduction system pacing therapy modes described herein may utilize detection of atrial depolarization or activation to deliver cardiac conduction system pacing therapy. More specifically, for example, each of the inhibition pacing mode, ventricular fusion pacing mode, atrioventricular synchronization pacing mode, and atrial fibrillation pacing mode described herein may utilize detection of atrial depolarization or activation to determine when and / or whether to deliver cardiac conduction system pacing therapy. For example, an atrioventricular delay may be triggered or initiated by sensing or detecting, and then termination of the atrioventricular delay may trigger or initiate a cardiac conduction system pacing pulse.

[0138] In addition, many cardiac conduction system pacing therapy systems may not include electrodes positioned near the atria (e.g., the right atrium) in order to collect and monitor near-field or local atrial electrical activity. For example, a cardiac conduction system pacing therapy system may include electrodes positioned outside the right atrium. In at least one embodiment, a cardiac conduction system pacing therapy system may include only a single-chamber device having electrodes implanted in the right ventricle and the ventricular septum from the right ventricle. As a result, such a system may utilize far-field electrical activity using one or more electrodes positioned outside the right atrium of the patient's heart. Such far-field electrical activity may be processed to determine a P wave indicative of atrial depolarization in order to be used for timing and delivery of cardiac conduction system pacing therapy.

[0139] exist Fig. 9 The following describes the FIG. 3A to FIG. 3B An illustrative method of far-field sensing of P waves utilizing a single-chamber device with electrodes implanted in the right ventricle is shown. As shown, method 300 may include monitoring electrical activity 302 of a patient's heart using one or more electrodes positioned outside the right atrium of the patient's heart. For example, electrical activity may be monitored using a left bundle branch electrode implanted in the ventricular septum proximal to the left bundle branch. For example, electrical activity may be monitored using a ring or coil electrode that is positioned proximal to the tip of the lead and is located in the blood pool of the right ventricle when the tip of the lead is implanted in the ventricular septum proximal to the left bundle branch. For example, electrical activity may be monitored using one of spiral electrode 761 and ring electrode 752 on lead 723 and the like. FIG. 3A to FIG. 3BThe electrical activity can be monitored by a combination of the housing or can electrodes of the device system 710. In other words, the sensing vector between the helical electrode 761 and the housing or can electrodes of the device 716 or the sensing vector between the ring electrode 752 and the housing or can electrodes of the device 716 can be used to provide the monitored electrical activity.

[0140] Method 300 may include determining a P wave 303 within the monitored electrical activity, and then delivering cardiac conduction system pacing therapy 314 based on the determined P wave. Determining a P wave 303 within the monitored electrical activity may include many of the processes described herein. For example, determining a P wave 303 within the monitored electrical activity may include filtering 304 the monitored electrical activity using one or more filters to produce the filtered electrical activity. In one embodiment, the one or more filters may include one or more of a 4th order Chebyshev type 2 low pass filter at 100 Hertz (Hz), a 1st order Butterworth high pass filter at 2.5 Hz, a 3rd order Butterworth low pass filter at 39 Hz, and a 2nd order Butterworth high pass filter at 13 Hz. In one embodiment, electrical activity monitored using a right ventricular coil electrode may be filtered from 13 Hertz (Hz) to 39 Hz. In Fig.11 A graph of the filtered and rectified far-field signal 350 over four cardiac cycles is depicted in FIG.

[0141] When determining a P wave within the electrical activity 303, one or more portions of the filtered electrical activity may be blanked 306 or ignored. In other words, one or more portions of the filtered electrical activity may not be utilized when attempting to detect or determine a P wave within the filtered electrical activity. For example, a post-ventricular atrial blanking period 308 may be determined and adjusted and used to blank or ignore one or more portions of the filtered electrical activity. Fig.10 The figure shows that Fig. 9 The exemplary method 308 for determining and adjusting the post-ventricular atrial blanking period is used in conjunction with the method of . The post-ventricular atrial blanking period can be described as a time period for blanking or ignoring the filtered electrical activity (i.e., ventricular depolarization or activation) after R wave sensing. For example, the post-ventricular atrial blanking period 360 is Figure 11 to Figure 12 As shown in the figure, it extends from the detected R wave 361.

[0142] Determining a P wave 303 within the monitored electrical activity may further include determining a P wave sensing 310 within the monitored electrical activity when the electrical activity is greater than or equal to a P wave threshold. For example, any electrical activity that is greater than or equal to the P wave threshold and does not occur during the post-ventricular atrial blanking period may be identified as a P wave sensing. In at least one embodiment, a P wave sensing may be determined within the monitored electrical activity when a sample of the monitored electrical activity is greater than or equal to the P wave threshold after two or more samples of the monitored electrical activity are less than the P wave threshold. The P wave threshold may be between approximately 10 microvolts and 15 microvolts. For example, the P wave threshold may be activated at 11 microvolts, which may be adjusted or adapted as further described herein. Additionally, if a P wave is sensed within a selected time period (e.g., 50 ms) prior to R wave sensing, the P wave sensing may be ignored.

[0143] The sensed P wave 362 is Figure 11 to Figure 12 , indicated by the thick solid vertical line, where the electrical activity exceeds the P wave threshold 365 indicated by the horizontal dashed line. As shown, P waves are identified in the first three cardiac cycles, but Fig.11 In addition, the P wave identified in the third cardiac cycle can be ignored because it is sensed within a selected time period 366 (e.g., 50 ms) before the R wave is sensed. The selected time period 366 is Fig.12 Shown in.

[0144] The P-wave threshold may be adaptive in that the P-wave threshold 312 may be continuously determined and / or adjusted. For example, the P-wave threshold may be determined based on the peak value of one or more previously sensed P-waves. More specifically, the P-wave peak value within a selected P-wave period after sensing of a P-wave within the monitored electrical activity may be determined or identified and then used to determine or generate the P-wave threshold value. The selected P-wave period may be between about 30 milliseconds (ms) and about 90 ms. In at least one embodiment, the selected P-wave period may be 60 ms. The P-wave threshold may be a selected percentage of one or more previous P-wave peak values. The selected percentage may be between about 40% and about 75% of one or more previous P-wave peak values. In one embodiment, if 50% of the P-wave peak value minus 1 microvolt is greater than the P-wave threshold value, the current P-wave threshold value may be multiplied by 1.0313, thereby generating an increased P-wave threshold value, and if 50% of the P-wave peak value plus 1 microvolt is less than the P-wave threshold value, the current wave threshold value may be multiplied by 0.9688, thereby generating a decreased P-wave threshold value. Additionally, the minimum P wave threshold may be approximately 10 microvolts. In other words, the P wave threshold may not decrease below 10 microvolts.

[0145] As a result, P waves, particularly P wave sensing indicating when atrial depolarization or activation occurs, can be determined 310 within the monitored electrical activity 303, which can then be used to deliver cardiac conduction system pacing therapy 314.

[0146] Fig.10 The figure shows that Fig. 9 An exemplary method 308 for determining and adjusting the post-ventricular atrial blanking period is provided for use with the method of . The method 308 can generally be described as using a representative cardiac cycle length to determine the post-ventricular atrial blanking period, and then adjusting one or both of the post-ventricular atrial blanking period and the representative cardiac cycle length.

[0147] The method 308 may further determine a representative cardiac cycle length 340. The representative cardiac cycle length may be based on a plurality of monitored cardiac cycle lengths. For example, an initial representative cardiac cycle length may be set to the median of the first five cardiac cycle lengths. The cardiac cycle length may be measured between consecutive R waves.

[0148] Then, the method 308 can determine the ventricular-atrial blanking period 342 based on the representative cardiac cycle length. For example, the ventricular-atrial blanking period can be a blanking period percentage of the representative cardiac cycle length. The blanking period percentage can be between about 60% and about 80% of the representative cardiac cycle length. In at least one embodiment, the blanking period percentage is 70%. In addition, in at least one embodiment, the ventricular-atrial blanking period can also be limited by a fixed maximum time period (such as, for example, 360ms).

[0149] During the performance of methods 300, 308, the ventricular-atrial blanking period 344 may be adjusted and the representative cardiac cycle length 346 may be adjusted. For example, the blanking period percentage may be adjusted based on when each P wave is sensed relative to the end of the atrial-atrial blanking period. For example, if a P wave is sensed greater than 137 ms after the end of the previous ventricular-atrial blanking period, the blanking period percentage may be incrementally increased (e.g., increased by 0.5%). Additionally, for example, if a P wave is sensed less than 58 ms after the end of the previous ventricular-atrial blanking period, the blanking period percentage may be incrementally decreased (e.g., decreased by 0.5%).

[0150] Additionally, if the blanking period percentage is currently 60% and a P wave is sensed less than 39 ms after the end of the previous post-ventricular atrial blanking period, the blanking period percentage may be substantially increased (e.g., by 10%) to, for example, avoid sensing a T wave as a P wave.

[0151] In addition, for example, based on Fig.12346 is continuously adjusted based on the currently measured cardiac cycle length 369 (e.g., R-wave to R-wave interval) identified in the representative cardiac cycle length. In at least one embodiment, the representative cardiac cycle length may be incrementally increased (e.g., increased by 5 ms, increased by 8 ms, increased by 10 ms, etc.) in response to an R-wave to R-wave interval that is greater than the representative cardiac cycle length, and incrementally decreased (e.g., decreased by 5 ms, decreased by 8 ms, decreased by 10 ms, etc.) in response to an R-wave to R-wave interval that is less than the representative cardiac cycle length.

[0152] In addition, a ventricular premature contraction may be detected in a cardiac cycle when the R-wave to R-wave interval is less than the percentage of ventricular premature contraction of the representative cardiac cycle length. The percentage of ventricular premature contraction may be between about 75% and 90%. In at least one embodiment, the percentage of ventricular premature contraction is 85%. Therefore, if a ventricular premature contraction is detected, the representative cardiac cycle length may not decrease even if the R-wave to R-wave interval is less than the representative cardiac cycle length. In this way, the representative cardiac cycle length may be incrementally reduced in response to an R-wave to R-wave interval that is less than the representative cardiac cycle length and greater than or equal to the percentage of ventricular premature contraction of the representative cardiac cycle length. In addition, as further described herein, if a ventricular premature contraction is detected, rate smoothing may be disabled in the next cardiac cycle.

[0153] Still further, for example, the representative cardiac cycle length 346 can be adjusted smoothly and continuously based on the rate. For example, if no P wave is detected during the cardiac cycle, the representative cardiac cycle length can be increased by a selected time value, such as, for example, 80 ms. In addition, for example, if no P wave is detected during the cardiac cycle, cardiac conduction system pacing therapy can be delivered based on the increased representative cardiac cycle length (i.e., the representative cardiac cycle length can be increased by a selected time value in response to no P wave being detected during the cardiac cycle). As a result, persistent undersensing of P waves may result in delivery of pacing therapy at a lower pacing rate limit. Additionally, if P waves are consistently undersensed, an atrial fibrillation pacing mode can be selected. Furthermore, if an accelerometer or other sensor indicates high patient activity, an inhibited pacing mode can be selected.

[0154] Fig.13Another exemplary method 400 for delivering cardiac therapy to a patient is depicted in . As shown, method 400 may include monitoring electrical activity 402. The electrical activity may be near-field activity or far-field activity using any of the electrodes described herein. Method 400 may then determine heart failure worsening 404 based on the monitored electrical activity. In particular, determining heart failure worsening 404 may detect the QRS complex width of the QRS complex of each cardiac cycle within the monitored electrical activity, and then evaluate the QRS complex width to determine whether heart failure is worsening. For example, a QRS complex that widens over time may indicate worsening of heart failure. In addition, for example, the QRS complex width may be compared to a QRS complex width threshold. The QRS complex width threshold may be between about 100 ms and about 180 ms. In at least one embodiment, the QRS complex width threshold is 130 milliseconds. If the QRS complex width is greater than or equal to the QRS complex width threshold, it may be determined that heart failure is worsening. In contrast, if the QRS complex width is less than the QRS complex width threshold, it may be determined that the heart failure has not worsened.

[0155] Additionally, more than one QRS complex width that is greater than or equal to a QRS complex width threshold may be detected to determine worsening heart failure. In other words, a single QRS complex width that is greater than or equal to the QRS complex width threshold may not be sufficient to determine worsening heart failure. Thus, worsening heart failure may be determined in response to a selected number of QRS complex widths from a plurality of QRS complex widths being greater than or equal to the QRS complex width threshold. In at least one embodiment, the selected number is 5.

[0156] If it is determined that heart failure is worsening, method 400 may deliver cardiac conduction system pacing using the cardiac conduction system pacing electrodes 406. In other words, method 400 may deliver cardiac conduction system pacing using the cardiac conduction system pacing electrodes in response to determining that heart failure is worsening.

[0157] Method 400 may be performed or executed periodically, for example, in response to the expiration of an evaluation period. The evaluation period may be between about 1 hour and 3 days. In at least one embodiment, the evaluation period is 1 day.

[0158] Illustrative Embodiments

[0159] Although the present disclosure is not limited thereto, an understanding of various aspects of the present disclosure will be gained through a discussion of the specific exemplary embodiments provided below. Various modifications to the exemplary embodiments as well as additional embodiments of the present disclosure will become apparent herein.

[0160] Embodiment 1: An implantable medical device, comprising: one or more implantable electrodes, the one or more implantable electrodes being used to sense and pace a patient's heart, wherein the one or more implantable electrodes include a cardiac conduction system electrode, the cardiac conduction system electrode being positionable proximate to a portion of the patient's cardiac conduction system; and a computing device, the computing device comprising a processing circuit, the computing device being operably connected to the one or more implantable electrodes, wherein the computing device is configured to: monitor electrical activity of the patient's heart using one or more electrodes positioned outside the right atrium of the patient's heart; determine a P wave within the monitored electrical activity; and deliver pacing therapy using the one or more implantable electrodes based on the determined P wave.

[0161] Example 2: A method comprising: monitoring electrical activity of a patient's heart using one or more electrodes positioned outside of the right atrium of the patient's heart; determining a P wave within the monitored electrical activity; and delivering cardiac conduction system pacing therapy based on the determined P wave using a cardiac conduction system pacing electrode comprising the one or more implantable electrodes, wherein the cardiac conduction system pacing electrode is positionable proximate to a portion of the patient's cardiac conduction system.

[0162] Example 3: The device according to Example 1 or the method according to Example 2, wherein the cardiac conduction system pacing electrode is a left bundle branch pacing electrode configured to deliver cardiac conduction system pacing therapy to the left bundle branch of the patient's heart.

[0163] Example 4: A device or method according to Example 3, wherein the electrical activity of the patient's heart is monitored using the left bundle branch pacing electrode.

[0164] Embodiment 5: A device or method according to any one of embodiments 1 to 4, wherein the one or more implantable electrodes include a right ventricular electrode configured to be positioned within the right ventricle, wherein the right ventricular electrode is used to monitor the electrical activity of the patient's heart.

[0165] Example 6: A device or method according to Example 5, wherein the right ventricular electrode is a coil electrode.

[0166] Embodiment 7: A device or method according to any one of embodiments 1 to 6, wherein determining a P wave within the monitored electrical activity comprises: filtering the monitored electrical activity using one or more filters to generate filtered electrical activity; and identifying a P wave within the filtered electrical activity.

[0167] Embodiment 8: A device or method according to embodiment 7, wherein the one or more filters include one or more of a 4th order Chebyshev type 2 low-pass filter at 100 Hz, a 1st order Butterworth high-pass filter at 2.5 Hz, a 3rd order Butterworth low-pass filter at 39 Hz, and a 2nd order Butterworth high-pass filter at 13 Hz.

[0168] Embodiment 9: A device or method according to any one of Embodiments 7 to 8, wherein determining a P wave within the monitored electrical activity comprises applying a gain to the filtered electrical activity to compensate for the filtering /

[0169] Embodiment 10: A device or method according to any one of embodiments 1 to 9, wherein determining a P wave within the monitored electrical activity comprises: determining a representative cardiac cycle length; determining a post-ventricular atrial blanking period based on the representative cardiac cycle length; and blanking the monitored electrical activity for the post-ventricular atrial blanking period after R wave sensing.

[0170] Embodiment 11: The device or method according to embodiment 10, wherein determining the representative cardiac cycle length comprises: determining a plurality of cardiac cycle lengths; and determining the representative cardiac cycle length based on the plurality of cardiac cycle lengths.

[0171] Embodiment 12: A device or method according to any one of embodiments 10 to 11, wherein the post-ventricular atrial blanking period is a blanking period percentage of the representative cardiac cycle length.

[0172] Embodiment 13: A device or method according to embodiment 12, wherein determining P waves within the monitored electrical activity further comprises adjusting the blanking period percentage based on when each P wave is sensed relative to the end of the post-atrial ventricular blanking period.

[0173] Embodiment 14: The device or method of any one of Embodiments 10 to 13, wherein determining a P wave within the monitored electrical activity further comprises:

[0174] Determining an R wave and an R wave to R wave interval within the monitored electrical activity; and adjusting the representative cardiac cycle length based on the R wave to R wave interval.

[0175] Embodiment 15: The device or method of Embodiment 14, wherein adjusting the representative cardiac cycle length based on the R-wave to R-wave interval comprises:

[0176] detecting a premature ventricular contraction in response to the R-wave to R-wave interval being less than a percentage of premature ventricular contraction of the representative cardiac cycle length; increasing the representative cardiac cycle length in response to the R-wave to R-wave interval being greater than the representative cardiac cycle length; and

[0177] The representative cardiac cycle length is reduced in response to the R-wave to R-wave interval being less than the representative cardiac cycle length and greater than or equal to the percentage of premature ventricular contractions of the representative cardiac cycle length.

[0178] Embodiment 15: A device or method according to any one of embodiments 10 to 14, wherein the post-ventricular atrial blanking period is limited to be less than a maximum percentage of the representative cardiac cycle length.

[0179] Embodiment 16: An apparatus or method according to any one of embodiments 10 to 15, wherein the computing device is further configured to perform the following items or the method further includes the following items: determining that no P wave is detected during the cardiac cycle; increasing the representative cardiac cycle length in response to not detecting the P wave during the cardiac cycle; and delivering pacing therapy based on the increased representative cardiac cycle length.

[0180] Embodiment 17: A device or method according to any one of Embodiments 1 to 16, wherein determining a P wave within the monitored electrical activity includes determining P wave sensing within the monitored electrical activity when the monitored electrical activity is greater than or equal to a P wave threshold.

[0181] Embodiment 18: A device or method according to Embodiment 17, wherein determining a P wave within the monitored electrical activity further comprises: determining a P wave peak within a selected P wave time period after the P wave sensing within the monitored electrical activity, and adjusting the P wave threshold based on the determined P wave peak.

[0182] Embodiment 19: A device or method according to any one of Embodiments 1 to 16, wherein determining a P wave within the monitored electrical activity includes determining P wave sensing within the monitored electrical activity when a sample of the monitored electrical activity is greater than or equal to a P wave threshold after two or more samples of the monitored electrical activity are less than the P wave threshold.

[0183] Embodiment 20: An implantable medical device, comprising: a cardiac conduction system pacing electrode, which is capable of being positioned proximate to a portion of a patient's cardiac conduction system to deliver cardiac conduction system pacing therapy to the portion of the patient's cardiac conduction system; a mechanical cardiac activation sensor, which is used to monitor the mechanical activity of the patient's heart; and a computing device, which includes a processing circuit and is operably connected to the cardiac conduction system pacing electrode and the mechanical cardiac activation sensor, wherein the computing device is configured to: monitor the mechanical activity of the patient's heart using the mechanical cardiac activation sensor; determine atrial activation based on the monitored mechanical activity; and deliver cardiac conduction system pacing using the cardiac conduction system pacing electrode based on the determined atrial activation.

[0184] Example 20: A method comprising: monitoring mechanical activity of a patient's heart using a mechanical cardiac activation sensor of a device; determining atrial activation based on the monitored mechanical activity; and delivering cardiac conduction system pacing using a cardiac conduction system pacing electrode of the device based on the determined atrial activation, wherein the cardiac conduction system pacing electrode is positionable proximate to a portion of the patient's cardiac conduction system to deliver cardiac conduction system pacing therapy to the portion of the patient's cardiac conduction system.

[0185] Embodiment 21: The device of Embodiment 19 or the method of Embodiment 20, wherein the mechanical cardiac activation sensor comprises one or more of a microphone and an accelerometer.

[0186] Example 22: According to the device or method of any one of Examples 19 to 21, the device further comprises a single lead configured for implantation in the right ventricle, wherein the cardiac conduction system electrode and the mechanical cardiac activation sensor are connected to the single lead.

[0187] Example 23: According to the device or method described in any one of Examples 19 to 21, the device further includes a leadless housing, which is configured for implantation in the right ventricle, wherein the cardiac conduction system pacing electrode and the mechanical cardiac activation sensor are connected to the leadless housing.

[0188] Example 24: A device or method according to any one of Examples 19 to 23, wherein delivering cardiac conduction system pacing using the cardiac conduction system pacing electrode based on the determined atrial activation includes delivering cardiac conduction system pacing at the termination of atrioventricular delay after the determined atrial activation.

[0189] Embodiment 25: A device or method according to embodiment 24, wherein the atrioventricular delay is fixed.

[0190] Embodiment 26: The device or method of embodiment 24, wherein the AV delay is less than the minimum intrinsic AV delay measured.

[0191] Example 27: A device or method as described in any one of Examples 19 to 26, wherein the cardiac conduction system pacing electrode is configured to deliver cardiac conduction system pacing therapy to the left bundle branch of the patient's heart.

[0192] Example 28: A device or method as described in any one of Examples 19 to 26, wherein the cardiac conduction system pacing electrode is configured to deliver cardiac conduction system pacing therapy to the bundle of His of the patient's heart.

[0193] Embodiment 29: An implantable medical device, comprising: one or more implanted electrodes for sensing electrical activity of a patient's heart and delivering cardiac therapy to the patient's heart, wherein the one or more implanted electrodes include a cardiac conduction system pacing electrode, wherein the cardiac conduction system pacing electrode is positionable proximate to a portion of the patient's cardiac conduction system to deliver cardiac conduction system pacing therapy to the portion of the patient's cardiac conduction system; and a computing device comprising a processing circuit and operably connected to the one or more implanted electrodes, wherein the computing device is configured to: perform a heart failure assessment, the heart failure assessment comprising: monitoring the electrical activity of the patient's heart using the one or more implanted electrodes; determining a QRS complex width based on the monitored electrical activity; and determining worsening of heart failure based on the determined QRS complex width; and delivering cardiac conduction system pacing using the cardiac conduction system pacing electrode in response to determining worsening of heart failure.

[0194] Example 30: A method comprising: performing a heart failure assessment, wherein the performing a heart failure assessment comprises: monitoring the electrical activity of the patient's heart using one or more implanted electrodes; determining a QRS complex width based on the monitored electrical activity; and determining worsening heart failure based on the determined QRS complex width; and delivering cardiac conduction system pacing using the cardiac conduction system pacing electrode in response to determining worsening heart failure.

[0195] Example 31: The device of Example 29 or the method of Example 30, wherein the cardiac conduction system pacing electrode is configured to deliver cardiac conduction system pacing therapy to the left bundle branch of the patient's heart.

[0196] Example 32: The apparatus of Example 29 or the method of Example 30, wherein the cardiac conduction system pacing electrode is configured to deliver cardiac conduction system pacing therapy to the bundle of His of the patient's heart.

[0197] Embodiment 33: A device or method according to any one of Embodiments 29 to 32, wherein the heart failure assessment is performed periodically in response to expiration of an assessment time period.

[0198] Embodiment 34: A device or method according to any one of embodiments 29 to 33, wherein determining worsening heart failure based on the determined QRS complex width includes determining worsening heart failure in response to the determined QRS complex width exceeding a QRS complex width threshold.

[0199] Embodiment 35: A device or method according to embodiment 34, wherein the QRS complex wave width threshold is 130 milliseconds.

[0200] Embodiment 36: A device or method according to any one of embodiments 29 to 33, wherein determining the QRS complex wave width based on the monitored electrical activity includes determining multiple QRS complex wave widths based on the monitored electrical activity within an evaluation time period, and wherein determining the worsening of heart failure based on the determined QRS complex wave widths includes determining the worsening of heart failure in response to a selected number of the determined QRS complex wave widths among the multiple determined QRS complex wave widths exceeding a QRS complex wave width threshold.

[0201] Embodiment 37: An implantable medical device, the implantable medical device comprising: a computing device including processing circuitry and operably coupled to one or more electrodes, the one or more electrodes including a cardiac conduction system pacing electrode positionable proximate a portion of a patient's cardiac conduction system, wherein the computing device is configured to: provide an inhibition pacing mode, a ventricular fusion pacing mode, an atrioventricular synchronization pacing mode, and an atrial fibrillation pacing mode;

[0202] Conducting a conduction test comprising: delaying delivery of cardiac conduction system pacing therapy to allow intrinsic cardiac activation; using the one or more

[0203] electrodes monitoring intrinsic electrical activity of the patient's heart;

[0204] determining one or more metrics based on the monitored intrinsic electrical activity; and

[0205] selecting one of an inhibition pacing mode, a ventricular fusion pacing mode, an atrioventricular synchronization pacing mode, and an atrial fibrillation pacing mode based on the determined one or more metrics; and delivering cardiac conduction system pacing using the cardiac conduction system pacing electrode in accordance with the selected mode.

[0206] Example 38: A system comprising: one or more implanted electrodes for sensing electrical activity of a patient's heart and delivering cardiac therapy to the patient's heart, wherein the one or more implanted electrodes include a cardiac conduction system pacing electrode that is positionable proximate to a portion of the patient's cardiac conduction system to deliver cardiac conduction system pacing therapy to the portion of the patient's cardiac conduction system; and a computing device comprising processing circuitry and operably coupled to the one or more implanted electrodes, wherein the computing device is configured to: provide pacing inhibition mode, ventricular fusion pacing mode, atrioventricular synchronous pacing mode and atrial fibrillation pacing mode; performing a conduction test, the conduction test comprising: delaying delivery of cardiac conduction system pacing therapy to allow intrinsic cardiac activation; monitoring the intrinsic electrical activity of the patient's heart using the one or more electrodes during intrinsic cardiac activation; determining one or more metrics based on the monitored intrinsic electrical activity; and selecting one of the inhibition pacing mode, ventricular fusion pacing mode, atrioventricular synchronous pacing mode and atrial fibrillation pacing mode based on the determined one or more metrics; and delivering cardiac conduction system pacing using the cardiac conduction system pacing electrodes according to the selected mode.

[0207] Example 39: A method comprising: providing an inhibition pacing mode, a ventricular fusion pacing mode, an atrioventricular synchronization pacing mode, and an atrial fibrillation pacing mode; performing a conduction test, the conduction test comprising: delaying delivery of cardiac conduction system pacing therapy to allow intrinsic cardiac activation; monitoring the intrinsic electrical activity of the patient's heart using the one or more electrodes during intrinsic cardiac activation; determining one or more metrics based on the monitored intrinsic electrical activity; and selecting one of the inhibition pacing mode, the ventricular fusion pacing mode, the atrioventricular synchronization pacing mode, and the atrial fibrillation pacing mode based on the determined one or more metrics; and delivering cardiac conduction system pacing in accordance with the selected mode using a cardiac conduction system pacing electrode that can be positioned proximate to a portion of the patient's cardiac conduction system.

[0208] Example 40: An apparatus according to Example 37, a system according to Example 38, or a method according to Example Ex39, wherein the computing device is further configured to perform the following items or the method further includes the following items: monitoring far-field electrical activity of the patient's heart using at least one of the one or more electrodes positioned outside the right atrium of the patient's heart; and determining electrical atrial activation based on the monitored far-field electrical activity, wherein delivering cardiac conduction system pacing includes delivering cardiac conduction system pacing based on the determined electrical atrial activation.

[0209] Example 41: An apparatus, system or method according to any one of Examples Ex37 to Ex40, wherein the computing device is further configured to perform the following items or the method further includes the following items: using a mechanical cardiac activation sensor to monitor the mechanical activity of the patient's heart to monitor the mechanical activity of the patient's heart; and determining mechanical atrial activation based on the monitored mechanical activity, wherein delivering cardiac conduction system pacing includes delivering cardiac conduction system pacing based on the determined mechanical atrial activation.

[0210] Embodiment 42: A device, system or method according to Embodiment 41, wherein the mechanical heart activation sensor comprises one or more of a microphone and an accelerometer.

[0211] Example 43: A device, system or method according to any one of Examples 37 to 42, wherein the cardiac conduction system pacing electrode is configured to deliver cardiac conduction system pacing therapy to the left bundle branch of the patient's heart.

[0212] Example 44: A device, system or method according to any one of Examples 37 to 43, wherein the cardiac conduction system pacing electrode is configured to deliver cardiac conduction system pacing therapy to the bundle of His of the patient's heart.

[0213] Embodiment 45: A device, system or method according to any one of embodiments 37 to 44, wherein the one or more metrics include QRS complex width, P wave to R wave (PR) interval and at least one atrial fibrillation indicator.

[0214] Embodiment 46: A device, system or method according to embodiment 45, wherein the at least one atrial fibrillation indicator includes one or more of R wave to R wave (RR) interval consistency, T wave to P wave (TP) interval consistency and far-field P wave morphology.

[0215] Example 47: A device, system or method according to any one of Examples Ex45 to Ex46, wherein the inhibited pacing mode is selected in response to at least the QRS complex width being less than or equal to a QRS complex width threshold, the PR interval being less than or equal to a PR interval threshold, and the atrial fibrillation indicator indicating that the patient is experiencing atrial fibrillation, wherein the inhibited pacing mode includes delivering cardiac conduction system pacing when intrinsic ventricular activation is not occurring.

[0216] Example 48: A device, system or method of Example 47, wherein the delivery of cardiac conduction system pacing is in response to termination of suppressed atrioventricular delay following atrial activation without sensing intrinsic ventricular activation, or in response to maintenance of baseline heart rate.

[0217] Example 49: A device, system or method according to any of Examples 47 to 48, wherein the atrioventricular synchronous pacing mode is selected in response to delivering at least pacing for at least two of four cardiac cycles.

[0218] Example 50: A device, system or method according to any of Examples 45 to 49, wherein the ventricular fusion pacing mode is selected in response to at least the QRS complex width being greater than a QRS complex width threshold, the PR interval being less than or equal to a PR interval threshold, and the atrial fibrillation indicator not indicating that the patient is experiencing atrial fibrillation, wherein the ventricular fusion pacing mode includes delivering cardiac conduction system pacing to initiate cardiac depolarization at the same time as intrinsic ventricular activation.

[0219] Example 51: A device, system or method according to Example 50, wherein the delivery of cardiac conduction system pacing is in response to termination of fused AV delay following atrial activation, wherein the fused AV delay is less than the measured minimum intrinsic AV delay.

[0220] Example 52: A device, system or method according to any one of Examples 45 to 51, wherein the AV synchronous pacing mode is selected in response to at least the atrial fibrillation indicator not indicating that the patient is experiencing atrial fibrillation and the PR interval is greater than a PR interval threshold, wherein the AV synchronous pacing mode includes delivering cardiac conduction system pacing in response to termination of a fixed atrioventricular delay following atrial activation.

[0221] Example 53: A device, system or method according to any one of Examples 45 to 52, wherein performing the conduction test further comprises performing a long-term conduction test in response to at least the atrial fibrillation indicator indicating that the patient is experiencing atrial fibrillation.

[0222] Example 54: A device, system or method according to Example 53, wherein the long-term conduction test includes monitoring the intrinsic electrical activity of the patient's heart using the one or more electrodes during intrinsic cardiac activation occurring during a long-term conduction time period, wherein the long-term conduction time period is greater than or equal to 30 seconds, and wherein the atrial fibrillation pacing mode is selected in response to at least the atrial fibrillation indicator indicating that the patient is experiencing atrial fibrillation during the long-term conduction time period.

[0223] Example 55: A device, system or method according to Example 54, wherein selecting the atrial pacing mode includes: selecting an inhibited atrial fibrillation response pacing mode in response to the QRS complex width being less than or equal to a QRS complex width threshold; selecting a conducted atrial fibrillation response pacing mode in response to a pacing capture threshold (PCT) being greater than or equal to a PCT threshold or in response to invalid capture; and selecting a cardiac resynchronization pacing mode in response to a pacing capture threshold (PCT) being less than a PCT threshold and valid capture.

[0224] Example 56: A device, system or method according to any one of Examples Ex37 to Ex55, wherein the monitoring of the intrinsic electrical activity of the patient's heart using the one or more electrodes occurs within a tested number of intrinsic heartbeats, wherein the tested number of intrinsic heartbeats is less than or equal to 10.

[0225] Embodiment 57: A device, system or method according to any one of Embodiments 37 to 56, wherein the conduction test is performed periodically in response to the termination of the test time period.

[0226] Example 58: A device, system or method according to Example 57, wherein the test time period is adjusted based on the selected pacing mode.

[0227] The present disclosure has been provided with reference to exemplary embodiments and examples, and is not meant to be interpreted in a limiting sense. As previously mentioned, those skilled in the art will recognize that various other exemplary applications can utilize the beneficial properties of the apparatus and methods described herein using the techniques as described herein. Various modifications of the exemplary embodiments and examples will become apparent after reference to this specification.

[0228] In one or more examples, the described techniques can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions can be stored as one or more instructions or codes on a computer-readable medium and executed by a hardware-based processing unit. The computer-readable medium may include a non-transitory computer-readable medium that corresponds to a tangible medium, such as a data storage medium (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 can be accessed by a computer).

[0229] 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 circuit systems. Thus, the term "processor" as used herein may refer to any of the aforementioned structures or any other physical structure suitable for implementing the described techniques. Additionally, these techniques may be fully implemented in one or more circuits or logic elements.

[0230] All references and publications cited herein are expressly incorporated by reference in their entirety for all purposes unless in any respect directly contradictory to this disclosure.

[0231] Unless otherwise specified, all scientific and technical terms used herein have the meanings commonly used in the art. The definitions provided herein are intended to facilitate understanding of certain terms frequently used herein and are not intended to limit the scope of the present disclosure.

[0232] Unless otherwise indicated, all numerical values ​​expressing feature sizes, amounts, and physical properties used in the specification and claims may be understood to be modified by the terms "exactly" or "about." Therefore, unless otherwise indicated, the numerical parameters set forth in the foregoing specification and the appended claims are approximations that may vary depending upon the desired properties sought to be obtained by one skilled in the art utilizing the teachings disclosed herein or, for example, within typical ranges of experimental error.

[0233] The recitation of numerical ranges by endpoints includes all values ​​within the range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within the range. As used herein, the term "at most" or "not greater than" a value (e.g., at most 50) includes that value (e.g., 50), and the term "not less than" a value (e.g., not less than 5) includes that value (e.g., 5).

[0234] The terms "coupled" or "connected" refer to elements being directly attached to one another (being in direct contact with one another) or indirectly attached (having one or more elements between and attaching two elements). Both terms may be modified by the interchangeable use of "operably" and "operably" to describe a connection or connection that is configured to allow the components to interact to perform at least some functions (e.g., a mobile user device may be operatively coupled to a cellular network to send data to or receive data from it).

[0235] References to "one embodiment," "an embodiment," "certain embodiments," or "some embodiments," etc., mean that a particular feature, configuration, composition, or characteristic described in conjunction with the embodiment is included in at least one embodiment of the present disclosure. Thus, the appearance of such phrases in various places throughout the text are not necessarily referring to the same embodiment of the present disclosure. Furthermore, the particular features, configurations, compositions, or characteristics may be combined in any suitable manner in one or more embodiments.

[0236] 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 used in its sense, including "and / or", unless the context clearly dictates otherwise.

[0237] As used herein, "having", "including", "comprising", etc. are used in their open-ended sense and generally mean "including but not limited to". It should be understood that "consisting essentially of", "consisting of", etc. are subsumed under "comprising", etc.

[0238] The term "and / or" means one or all of the listed elements or a combination of at least two of the listed elements.

[0239] The phrases "at least one of," "including at least one of," and "one or more of" accompanying a list refer to any one of the items in the list and any combination of two or more items in the list.

Claims

1. An implantable medical device, comprising: A computing device comprising processing circuitry and operably coupled to one or more implanted electrodes, the one or more implanted electrodes comprising a cardiac conduction system pacing electrode positionable proximate a portion of a cardiac conduction system of a patient, wherein the computing device is configured to: Provides inhibition pacing mode, ventricular fusion pacing mode, atrioventricular synchronization pacing mode and atrial fibrillation pacing mode; Conducting a conduction test, the conduction test comprising: Delayed delivery of cardiac conduction system pacing therapy to allow intrinsic cardiac activation; monitoring intrinsic electrical activity of the patient's heart using the one or more implantable electrodes during intrinsic cardiac activation; determining one or more metrics based on the monitored intrinsic electrical activity; and selecting one of an inhibited pacing mode, a ventricular fusion pacing mode, an atrioventricular synchronization pacing mode, and an atrial fibrillation pacing mode based on the determined one or more metrics; and Cardiac conduction system pacing is delivered using the cardiac conduction system pacing electrodes according to the selected mode.

2. The apparatus according to claim 1, wherein the computing device is further configured to perform the following items or the method further includes the following items: monitoring far-field electrical activity of the patient's heart using at least one of the one or more implanted electrodes positioned outside of a right atrium of the patient's heart; and determining electrical atrial activation based on the monitored far-field electrical activity, Wherein delivering cardiac conduction system pacing comprises delivering cardiac conduction system pacing based on the determined electrical atrial activation.

3. The apparatus according to any one of claims 1 to 2, wherein the computing device is further configured to perform the following items or the method further includes the following items: monitoring the mechanical activity of the patient's heart using a mechanical heart activation sensor to monitor the mechanical activity of the patient's heart; and Determining mechanical atrial activation based on the monitored mechanical activity, Wherein delivering cardiac conduction system pacing comprises delivering cardiac conduction system pacing based on the determined mechanical atrial activation.

4. The apparatus of any one of claims 1 to 3, wherein the cardiac conduction system pacing electrode is configured to deliver cardiac conduction system pacing therapy to a left bundle branch of the patient's heart or a bundle of His of the patient's heart.

5. A device according to any one of claims 1 to 4, wherein the one or more metrics include QRS complex width, P wave to R wave (PR) interval and at least one atrial fibrillation indicator, wherein the at least one atrial fibrillation indicator includes one or more of R wave to R wave (RR) interval consistency, T wave to P wave (TP) interval consistency and far-field P wave morphology.

6. An apparatus according to claim 5, wherein the inhibited pacing mode is selected in response to at least the QRS complex width being less than or equal to a QRS complex width threshold, the PR interval being less than or equal to a PR interval threshold, and the atrial fibrillation indicator indicating that the patient is experiencing atrial fibrillation, wherein the inhibited pacing mode includes delivering cardiac conduction system pacing when intrinsic ventricular activation is not occurring.

7. An apparatus according to claim 6, wherein the delivery of cardiac conduction system pacing is in response to termination of suppressed atrioventricular delay following atrial activation without sensing intrinsic ventricular activation, or in response to maintenance of baseline heart rate.

8. The apparatus of any one of claims 6 to 7, wherein the atrioventricular synchronous pacing mode is selected in response to delivering pacing for at least two of four cardiac cycles.

9. An apparatus according to any one of claims 5 to 8, wherein the ventricular fusion pacing mode is selected in response to at least the QRS complex width being greater than a QRS complex width threshold, the PR interval being less than or equal to a PR interval threshold, and the atrial fibrillation indicator not indicating that the patient is experiencing atrial fibrillation, wherein the ventricular fusion pacing mode includes delivering cardiac conduction system pacing to initiate cardiac depolarization at the same time as intrinsic ventricular activation.

10. The apparatus of claim 9, wherein the delivery of cardiac conduction system pacing is responsive to termination of a fused AV delay following atrial activation, wherein the fused AV delay is less than a measured minimum intrinsic AV delay.

11. An apparatus according to any one of claims 5 to 10, wherein the atrioventricular synchronous pacing mode is selected in response to at least the atrial fibrillation indicator not indicating that the patient is experiencing atrial fibrillation and the PR interval is greater than a PR interval threshold, wherein the atrioventricular synchronous pacing mode includes delivering cardiac conduction system pacing in response to termination of a fixed atrioventricular delay following atrial activation.

12. The apparatus of any one of claims 5 to 11, wherein performing the conduction test further comprises performing a long-term conduction test in response to at least the atrial fibrillation indicator indicating that the patient is experiencing atrial fibrillation.

13. The apparatus of claim 12, wherein the long-term conduction test comprises monitoring the intrinsic electrical activity of the patient's heart using the one or more implanted electrodes during an intrinsic cardiac activation period occurring within a long-term conduction period, wherein the long-term conduction period is greater than or equal to 30 seconds, Wherein the atrial fibrillation pacing mode is selected in response to at least the atrial fibrillation indicator indicating that the patient is experiencing atrial fibrillation during the prolonged conduction time period.

14. The apparatus of claim 13, wherein selecting the atrial pacing mode comprises: selecting an inhibit atrial fibrillation response pacing mode in response to the QRS complex width being less than or equal to a QRS complex width threshold; selecting a conducted atrial fibrillation response pacing mode in response to a pacing capture threshold (PCT) being greater than or equal to a PCT threshold or in response to ineffective capture; as well as A cardiac resynchronization pacing mode is selected in response to a pacing capture threshold (PCT) being less than the PCT threshold and valid capture.

15. An apparatus according to any one of claims 1 to 14, wherein the monitoring of the intrinsic electrical activity of the patient's heart using the one or more implantable electrodes occurs within a tested number of intrinsic heart beats, wherein the tested number of intrinsic heart beats is less than or equal to 10.

Images