Left ventricular capture and synchronization verification using a single multi-electrode coronary sinus lead

Abstract

A method and implantable medical device system for delivering left ventricular (LV) cardiac pacing therapy via a single-pass coronary sinus lead and sensing far-field cardiac signals via one or more far-field sensing vectors formed between a plurality of electrodes. Beat morphologies corresponding to the far-field cardiac signals are determined, and a beat morphology match between each of the far-field beat morphologies and an intrinsic beat morphology template is determined, such that in response to the determined beat morphology match, one of LV loss of capture, pseudo-fusion, and desynchronization is determined. In response to one of LV loss of capture, pseudo-fusion, and desynchronization determined as a response to the determined beat morphology match, one of a loss of capture adjustment, a pseudo-fusion adjustment, and a resynchronization adjustment is performed to generate an adjusted LV cardiac pacing therapy.

Description

Technical Field

[0001] The present disclosure relates to cardiac pacing methods and systems and, more particularly, to a method and apparatus for delivering cardiac pacing therapy in an implantable cardiac therapy device system having only a single multi-electrode coronary sinus lead. Technical Background

[0002] The activity of a normal healthy heart involves the synchronized contraction of the heart's atria and ventricles. Blood is received into the atria, which contract, forcing the blood into the ventricles. Subsequent contraction of the ventricles then causes the blood to be pumped through the body and eventually back into the atria. The contraction of the heart's chambers is caused by the coordinated electrical activation of multiple parts of the myocardium.

[0003] The heartbeat cycle begins with the generation of an electrical impulse by a bundle of fibers located in the heart's sinoatrial node, which is near the entrance of the superior vena cava in the upper part of the right atrium. The impulse propagates across the atria, stimulating the atrial muscles and causing them to contract, which forces blood into the ventricles. Atrial contraction is manifested as the so-called "P wave" in the electrocardiogram signal. The electrical impulse conducted through the atrial muscles is then received at the atrioventricular node or AV node at the partition wall of the valve between the right atrium and the right ventricle. The AV node introduces a slight delay in the transmission of the electrical impulse to the ventricles. The AV delay is usually on the order of 100 milliseconds. After the AV delay, the electrical impulse is conducted to the ventricles, causing the ventricles to contract, which is manifested as the "QRS complex" of the electrocardiogram signal. The subsequent repolarization and relaxation of the ventricular muscles occur at the end of the cardiac cycle, which is manifested as the "T wave portion" of the electrocardiogram signal.

[0004] For patients described above in which the conduction of electrical impulses through the myocardium is impaired in some way, a pacemaker can provide artificial electrical stimulation in the absence of natural electrical impulses. Thus, for example, a ventricular pacemaker can act to cause ventricular contraction in a patient in whom, for some reason, the natural cardiac electrical impulses are not transmitted across the AV node. However, it is important that any artificial stimulation pulses be delivered at the appropriate time so that the correct synchronization of atrial and ventricular action is maintained. In addition, it is known that electrical impulses delivered to the myocardium during the repolarization phase at the end of the cardiac cycle can cause the onset of tachyarrhythmias. Therefore, it is important to prevent the pacemaker from delivering stimulatory pulses during the T wave.

[0005] To maintain AV synchronization and prevent delivery of pacing pulses at undesirable times, the pacemaker is preferably capable of detecting atrial activity or ventricular activity or both, as manifested by P waves and QRS complexes (or more typically, R waves), via atrial and ventricular electrogram signals sensed by the pacemaker, respectively.

[0006] Pacemakers are typically characterized by which chambers of the heart they are able to sense, which chambers they deliver pacing stimuli to, and their response, if any, to sensed intrinsic cardiac electrical activity. Some pacemakers deliver pacing stimuli at fixed, regular intervals, regardless of naturally occurring cardiac activity. More commonly, however, pacemakers sense cardiac electrical activity in one or two chambers of the heart and inhibit or trigger the delivery of pacing stimuli to the heart based on the occurrence and identification of sensed intrinsic electrical events.

[0007] The beating of the heart is controlled by the sinoatrial node, which is a group of conducting cells located in the right atrium near the entrance of the superior vena cava. The depolarization signal generated by the sinoatrial node excites the atrioventricular node. The atrioventricular node temporarily delays the propagation of the depolarization signal, allowing the atria to empty before the depolarization signal is transmitted to the ventricles of the heart. The coordinated contraction of these two ventricles drives blood flow through the patient's body. In some cases, the conduction of the polarization signal from the atrioventricular node to the left and right ventricles may be interrupted or slowed. This may result in asynchronous contraction of the left and right ventricles, which may lead to heart failure or death.

[0008] Cardiac resynchronization therapy (CRT) can correct the symptoms of electrical dyssynchrony by providing pacing therapy to one or both ventricles or atria via medical electrical leads to stimulate early activation of the left or right ventricle. By pacing the contraction of the ventricles, the ventricles can be controlled so that the ventricles contract synchronously.

[0009] CRT resynchronization pacing devices operate by delivering pacing stimulation to both ventricles or to one ventricle, obtaining the desired result of more or less simultaneous mechanical contraction and blood ejection from the ventricles. Ideally, each pacing pulse stimulus delivered to the ventricles induces a response from the ventricles. Delivering electrical stimulation that causes the ventricles to respond is generally referred to as capturing the ventricles. For various reasons, a cardiac pacing system may not achieve effective capture of the ventricles. For example, the pacing lead and / or electrode may not be placed in the optimal position. Sensed atrioventricular delay (SAV), paced atrioventricular delay (PAV), and right ventricular pre-excitation may also affect whether the ventricles are effectively captured. Exemplary causes of ineffective capture include too long sensed atrioventricular delay (SAV), too long paced atrioventricular delay (PAV), and RV pre-excitation, which are usually addressed by adjusting the delivery of electrical stimulation to the ventricles. Other exemplary causes of ineffective capture may include: the occurrence of atrial fibrillation (AF); medical electrical leads placed in scar tissue, loss of capture due to lead migration; failure to sense the atria, rates above the upper tracking rate; and right ventricular leads and left ventricular leads being too close together. In addition, pacing leads may migrate or dislodge after the medical device has been implanted, resulting in ineffective capture.

[0010] One form of CRT is fusion pacing, which generally involves LV-only pacing using electrodes on the left ventricular (LV) medical electrical leads in coordination with intrinsic right ventricular (RV) excitation. Effective fusion requires, for example, synchronization of the timing of LV pacing with the earliest excitation on the RV chamber. For example, in a fusion pacing configuration, the medical device delivers one or more fusion pacing pulses to the late-contracting left ventricle (LV) in order to pre-excite the LV and synchronize the depolarization of the LV with the depolarization of the early-contracting right ventricle (RV). The ventricular excitation of the LV can be "fused" (or "merged") with the ventricular excitation of the RV attributable to the intrinsic conduction of the heart. In this way, the intrinsic and pacing-induced excitation wavefronts can be fused together so that the depolarization of the LV is resynchronized with the depolarization of the RV.

[0011] Current therapy systems for delivering CRT typically include: a right atrial lead extending into the right atrium (RA) of a patient's heart; a right ventricular lead extending through the right atrium and into the right ventricle (RV); and a left ventricular lead extending through the right and into the coronary sinus to a region adjacent to the free wall of the left ventricle (LV) of the heart. What is needed is a method of verifying LV capture and / or proper synchronization or fusion with other chambers of the heart during delivery of LV pacing in a cardiac therapy device system having only a single-pass left DDD lead that provides pacing and sensing to both the ventricle and atrium without the need to introduce leads or electrodes in the right ventricle. Summary of the invention

[0012] The present disclosure relates to methods for delivering LV pacing therapy, and implantable medical devices for delivering LV pacing therapy and comprising only a single-pass coronary sinus lead. The single-pass coronary sinus lead comprises electrodes spaced from one another such that when the lead is positioned within the patient's coronary sinus, the electrodes can be positioned near the left ventricle and close to the left and / or right atrium. In some examples, the electrode near the left ventricle can be positioned near the intraventricular septum.

[0013] In this way, a lead according to the present disclosure is designed to provide pacing and sensing to both the atria and ventricles, and does not require the introduction of a lead or electrode into the right ventricle, and may be referred to as a single-pass left-sided DDD lead. The lead may be referred to as a single-pass because the single lead places electrodes near both the atria and ventricles, and may be referred to as a left-sided because the lead places electrodes (e.g., via the coronary sinus) near the left ventricle rather than the right ventricle. The lead may also be referred to as a single-pass coronary sinus lead.

[0014] According to one example of the present disclosure, a method for delivering left ventricular (LV) cardiac pacing therapy to a patient includes: delivering LV cardiac pacing therapy via one of a plurality of electrodes; sensing far-field cardiac signals via one or more far-field sensing vectors formed between the plurality of electrodes; determining a beat morphology corresponding to the far-field cardiac signal sensed for each of the far-field sensing vectors to generate a corresponding far-field beat morphology; determining a beat morphology match between each of the far-field beat morphologies and an intrinsic beat morphology template; determining one of LV loss of capture, pseudo-fusion, and loss of synchrony in response to the determined beat morphology match; performing one of a loss of capture adjustment, a pseudo-fusion adjustment, and a resynchronization adjustment in response to one of LV loss of capture, pseudo-fusion, and loss of synchrony determined as a response to the determined beat morphology match to generate an adjusted LV cardiac pacing therapy; and delivering the adjusted LV cardiac pacing therapy via one of the plurality of electrodes.

[0015] Another example of the present disclosure includes an implantable medical device system for delivering left ventricular (LV) cardiac pacing therapy to a patient, comprising: an implantable medical device housing; a single-pass coronary sinus lead capable of being electrically coupled to the implantable medical device housing; a plurality of electrodes positioned along the single-pass coronary sinus lead for sensing far-field cardiac signals of the patient and delivering the LV cardiac pacing therapy; and a processor positioned within the implantable medical device housing and configured to sense the far-field cardiac signals via one or more far-field sensing vectors formed between the plurality of electrodes, determine a corresponding signal for each of the far-field sensing vectors, and The invention relates to a method of detecting a beat morphology of a plurality of sensed far-field cardiac signals to generate a corresponding far-field beat morphology, determining a beat morphology match between each of the far-field beat morphologies and an intrinsic beat morphology template, determining one of LV loss-of-capture, pseudo-fusion, and desynchronization in response to the determined beat morphology match, performing one of a loss-of-capture adjustment, a pseudo-fusion adjustment, and a resynchronization adjustment in response to the one of the LV loss-of-capture, pseudo-fusion, and desynchronization determined as a response to the determined beat morphology match to generate an adjusted LV cardiac pacing therapy, and delivering the adjusted LV cardiac pacing therapy via an electrode of the plurality of electrodes.

[0016] Another example of the present disclosure includes a non-transitory computer-readable medium storing instructions that cause an implantable medical device to perform a method comprising: delivering LV cardiac pacing therapy via an electrode among a plurality of electrodes; sensing a far-field cardiac signal via one or more far-field sensing vectors formed between the plurality of electrodes; determining a beat morphology corresponding to the far-field cardiac signal sensed for each of the far-field sensing vectors to generate a corresponding far-field beat morphology; determining a beat morphology match between each of the far-field beat morphologies and an intrinsic beat morphology template; determining one of LV loss of capture, pseudo-fusion, and desynchronization in response to the determined beat morphology match; performing one of a loss of capture adjustment, a pseudo-fusion adjustment, and a resynchronization adjustment in response to one of LV loss of capture, pseudo-fusion, and desynchronization determined as a response to the determined beat morphology match to generate an adjusted LV cardiac pacing therapy; and delivering the adjusted LV cardiac pacing therapy via an electrode among the plurality of electrodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a conceptual diagram illustrating an example cardiac therapy device system for delivering pacing stimulation to a patient's heart in accordance with the present disclosure.

[0018] Figure 2 is a conceptual diagram illustrating an example configuration of leads of a cardiac therapy device system for delivering pacing therapy to a patient's heart in accordance with the present disclosure.

[0019] Figure 3 is a conceptual diagram illustrating an example configuration of leads of a cardiac therapy device system for delivering pacing therapy to a patient's heart in accordance with the present disclosure.

[0020] Figure 4 is a conceptual diagram illustrating an example configuration of leads of a cardiac therapy device system for delivering pacing therapy to a patient's heart in accordance with the present disclosure.

[0021] Figure 5 is a functional block diagram of an implantable cardiac therapy device system for delivering pacing therapy in accordance with the present disclosure.

[0022] Figure 6 is a flow chart of a method of delivering pacing therapy in a cardiac therapy device system according to the present disclosure.

[0023] Figure 7 is a flow chart of a method of delivering pacing therapy in a cardiac therapy device system according to the present disclosure. DETAILED DESCRIPTION

[0024] 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 that possible embodiments of such methods, devices, and systems using the combinations of features set forth herein are not limited to the specific embodiments shown in the drawings 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.

[0025] In general, the present disclosure relates to methods of verifying LV capture and / or proper synchronization or fusion with other chambers of the heart during delivery of cardiac resynchronization pacing therapy without the need to introduce a lead or electrode in the right ventricle in a cardiac therapy device system having only a single-pass left-side DDD lead that provides pacing and sensing of both the ventricles and atria. The lead may be referred to as single-pass because the single lead places electrodes near both the atria and ventricles, and may be referred to as left-side because the lead places electrodes near the left ventricle (e.g., via the coronary sinus) but not the right ventricle.

[0026] For example, a cardiac treatment device system may include a housing or can and a single lead that is electrically coupled to the housing and capable of providing left ventricular LV DDD pacing. The lead of the present disclosure may include four electrodes that are spaced apart from each other so that when the lead is positioned in the patient's coronary sinus, the electrodes may be positioned near the left ventricle and close to the left atrium and / or right atrium. In some examples, the electrode near the left ventricle may be positioned near the intraventricular septum. In other examples, more than four electrodes or less than 4 electrodes may be used.

[0027] Figure 1 is a conceptual diagram illustrating an example cardiac therapy device system for delivering pacing stimulation to a patient's heart according to the present disclosure. Figure 1 As shown in FIG. 1 , in one example, an implantable cardiac therapy device system 10 may include an implantable medical device (IMD) 12 and an implantable medical lead 16 electrically coupled to the IMD 12. Figure 1 In the example shown in , system 10 is implanted in a patient 18 for use in delivering electrical stimulation therapy to a heart 20 of patient 18. Patient 18 will typically be a human patient, but need not necessarily be a human patient.

[0028] exist Figure 1In the example shown in , IMD 12 is a cardiac pacemaker, cardioverter, defibrillator, or pacemaker-cardioverter-defibrillator (PCD) that generates therapeutic electrical stimulation for pacing, cardioversion, or defibrillation, which may take the form of pulses, such as pacing pulses of about 1 volt to about 5 volts and a frequency of about 50 pulses per minute to about 150 pulses per minute, or less frequent cardioversion / defibrillation stimulation of about 100 volts to about 800 volts. Leads 16 include four electrodes, each of which is positioned within heart 20 (e.g., within a blood vessel) to facilitate delivery of therapeutic electrical stimulation from IMD 12 to heart 20.

[0029] In the example shown, the distal end of lead 16 is positioned near the left ventricle (LV) of patient 18, and more specifically, within the coronary sinus or within the coronary vein via a coronary sinus incision. In the example shown, lead 16 is configured to be introduced intravenously into heart 20. For example, lead 16 may have a lead body diameter between about 1 mm and about 3 mm. When lead 16 is positioned within the coronary sinus or coronary vein, four electrodes ( Figure 1 The IMD 12 (not shown) can be positioned so that the two most proximal electrodes are positioned within or near the right atrium (RA) and in close proximity to the AV node. In some examples, one electrode can be in the RA and one electrode can be in the coronary sinus. The third electrode can be positioned in the great cardiac vein, and the fourth most distal electrode can be positioned in one of the multiple branches of the great coronary vein. For example, the fourth electrode can be positioned in the lateral coronary vein, the anterior coronary vein, or the anterior lateral coronary vein. As described in further detail below, this configuration of electrodes allows atrial sensing and pacing as well as ventricular sensing and pacing using a single lead, if desired. The housing 14 of the IMD 12 can be used as an anode in some examples.

[0030] To facilitate downward passage through narrowed blood vessels, the electrode of the lead 16 has a diameter that is nearly the same as the lead body, and is typically a few tenths of a millimeter thicker than the lead body to ensure that the electrode contacts the vessel wall. Figure 2 ) may also be slightly thicker (e.g., a few tenths of a millimeter thicker) than the lead body. The electrode is typically about 0.2 cm to about 0.5 cm long. The entire lead is about 50 cm to about 100 cm long, depending on the patient's size.

[0031] like Figure 1As shown in , system 10 may also include programmer 22, which may be a handheld device, portable computer, or workstation that provides a user interface for a clinician or other user. The clinician may interact with the user interface to program stimulation and sensing parameters of IMD 12, which may include, for example, which electrodes of leads 16 are activated to provide stimulation and sensing, respectively, and selecting from different pacing modes, rate response modes, chamber intervals, arrhythmia detection algorithms, and arrhythmia termination therapy progressions.

[0032] Programmer 22 supports telemetry (e.g., radio frequency telemetry) with IMD 12 for downloading stimulation parameters and optionally uploading operational data or physiological data stored by IMD 12. In this way, a clinician can periodically query IMD 12 to assess therapeutic efficacy and modify the operating parameters of the IMD if necessary. IMD 12 and programmer 22 may communicate via wireless communication, such as Figure 1 Programmer 22 may communicate with IMD 12 via wireless communication, for example, using RF telemetry techniques known in the art.

[0033] In some examples, at least one of the electrodes of lead 16 may be used as a sensor that senses a physiological parameter of patient 12, such as, but not limited to, an electrogram (EGM) parameter, heart rate, QRS width, or atrioventricular (AV) separation. The sensing electrode may be the same electrode as the electrode used to deliver electrical stimulation to patient 18, or a different electrode.

[0034] Figure 2 is a conceptual diagram illustrating an example configuration of leads of a cardiac therapy device system for delivering pacing therapy to a patient's heart in accordance with the present disclosure. Figure 2 As shown in FIG, lead 16A of cardiac treatment device system 10A may include electrodes 24, 26, 28, and 30, and a helical fixation member 32. In some examples, helical fixation member 32 may also be electrode 28, e.g., helical fixation member 32 is conductive and serves as electrode 28 or is a portion of electrode 28. Lead 16A may be anchored to a wall of coronary sinus 36, near ostium 34, via helical fixation member 32. When the electrode is positioned within heart 20 as intended, lead 16A may be anchored by turning the lead clockwise to embed helical fixation member 32 into the wall of coronary sinus 36.

[0035] like Figure 2As shown in , the electrodes of lead 16 are spaced apart from one another so that electrodes 24 and 26 are positioned within RA 40. In some examples, electrodes 24 and 26 are suspended electrodes within RA 40, e.g., not necessarily in contact with tissue of RA 40. For example, electrodes 24 and 26 may be suspended atrial sensing electrodes that operate in a similar manner to suspended sensing electrodes in a conventional VDD lead. In some examples, electrodes 24 and 26 are positioned near the septum of the heart. Figure 2 In an example of, electrode 28 is positioned within the coronary sinus 36, and electrode 30 is positioned at the distal end of lead 16, within one of the branch veins of the great coronary veins. For example, electrode 30 may be positioned in the lateral coronary vein, the anterior coronary vein, or the anterior lateral coronary vein. The branch vein is selected so that electrode 30 is approximately adjacent to the left ventricle (LV) and relatively far from the apex of the right ventricle (RV). Electrodes 24 and 26 may be positioned less than about 1 cm apart from each other. In some examples, electrodes 24 and 26 may be spaced less than about 0.5 cm apart from each other. The close spacing of atrial electrodes 24 and 26 may help avoid R-wave oversensing, including far-field R-wave oversensing. In addition, the location of the electrodes may assist in detecting the occurrence of AV block. In some examples, either of electrodes 24 and 26 may use a monopolar configuration, in which an electrode formed on or by housing 14 is used to sense atrial activity. In some examples, electrode 28 may serve as an atrial pacing cathode, and housing 14 of IMD 12 may serve as an atrial sensing anode. Electrode 28 may also serve as a ventricular sensing anode, and electrode 30 may serve as a ventricular sensing cathode. Housing 14 may also serve as an anode when electrode 30 delivers stimulation to LV 40.

[0036] Figure 3 is a conceptual diagram illustrating an example configuration of leads of a cardiac therapy device system for delivering pacing therapy to a patient's heart in accordance with the present disclosure. Figure 3 As shown in , lead 16B of implantable cardiac pacing device system 10B may include electrodes 24, 26, 28, and 30, and a helical fixation member 32, which may be used as electrode 26 or electrically coupled to electrode 26. Lead 16B may be anchored to the wall of coronary sinus 36, near ostium 34, via helical fixation member 32. When the electrode is positioned in the heart as intended, lead 16B may be anchored by rotating the lead clockwise to embed helical fixation member 32 into the wall of coronary sinus 36. As shown in FIG. Figure 3As shown in , the electrodes of lead 16 are spaced so that electrode 24 is positioned within RA 40, electrode 26 is positioned near the coronary sinus ostium 34, electrode 28 is positioned in the great cardiac vein near the left atrium, and electrode 30 is positioned at the distal end of lead 16 and within one of the branch veins of the great coronary vein. For example, electrode 30 may be positioned in the lateral coronary vein, the anterior coronary vein, or the anterior lateral coronary vein. The branch vein is selected so that electrode 30 is generally adjacent to the left ventricle (LV) and relatively far from the apex of the right ventricle (RV).

[0037] Electrodes 24 and 26 may be used as a bipolar pair to sense atrial activity. Electrodes 24 and 26 may be positioned less than about 1 cm apart from each other. In some examples, electrodes 24 and 26 may be spaced less than about 0.5 cm apart from each other. The close spacing of atrial electrodes 24 and 26 may help avoid R-wave oversensing, including far-field R-wave oversensing. In addition, the location of the electrodes may assist in detecting the occurrence of AV block. In some examples, either of electrodes 24 and 26 may use a monopolar configuration, where an electrode formed on or by housing 14 is used to sense atrial activity.

[0038] In some examples, electrode 26 may serve as an atrial pacing cathode, and housing 14 of IMD 12 may serve as an atrial sensing anode. Electrode 28 may serve as a ventricular sensing anode, while electrode 30 may serve as a ventricular sensing cathode, or either of electrodes 28 and 30 may be used in a unipolar configuration for sensing electrical activity of the ventricles. In addition, electrodes 28 and 30 may be used to deliver bipolar pacing or other stimulation to LV 40, or either or both of electrodes 28 and 30 may be used in a unipolar configuration with electrodes of housing 14 for delivering unipolar stimulation. When electrode 28 or 30 stimulates, housing 14 may serve as an anode. In some examples, both electrodes 28 and 30 may be used in a unipolar configuration for delivering sequential pacing to the ventricles. For example, electrode 28 may provide a first pacing pulse. A delay of approximately 10 milliseconds may be programmed between a pacing pulse from electrode 28 and a second pacing pulse from electrode 30. During the delay, electrode 30 is in a sensing mode. If electrodes 30 sense that the pulses from electrodes 28 successfully captured the heart, then pacing pulses from electrodes 30 are suppressed. However, if the pacing pulses from electrodes 28 did not result in capture, then electrodes 30 provide a second pacing pulse.

[0039] Figure 4 is a conceptual diagram illustrating an example configuration of leads of a cardiac therapy device system for delivering pacing therapy to a patient's heart in accordance with the present disclosure. Figure 4As shown in , lead 16C of implantable cardiac pacing device system 10B may include electrodes 24, 26, 28, and 30, and a helical fixation member 32, which may be used as electrode 26 or electrically coupled to electrode 26. Lead 16C may be anchored to the wall of coronary sinus 36, near ostium 34, via helical fixation member 32. When the electrode is positioned within heart 20 as intended, lead 16C may be anchored by rotating lead 16C clockwise to embed helical fixation member 32 into the wall of coronary sinus 36. Figure 4 As shown in , the electrodes of lead 16 are spaced from each other so that electrode 24 is positioned distally of coronary sinus 36 and proximal to coronary sinus ostium 34, electrode 26 is positioned distally within coronary sinus 36 and proximal to electrode 24, electrode 28 is positioned in the great cardiac vein and proximal to the left atrium, and electrode 30 is positioned at the distal end of lead 16 and within one of the branch veins of the great coronary vein. For example, electrode 30 may be positioned in the lateral coronary vein, the anterior coronary vein, or the anterior lateral coronary vein. The branch vein is selected so that electrode 30 is generally adjacent to the left ventricle (LV) and relatively far from the apex of the right ventricle (RV).

[0040] As described above, electrodes 24 and 26 can be used as a bipolar pair to sense atrial activity. Electrode 24 and electrode 26 can be positioned less than about 1 cm apart from each other. In some examples, electrode 24 and electrode 26 can be separated from each other by less than about 0.5 cm. The close spacing of atrial electrodes 24 and 26 can help avoid R-wave oversensing, including far-field R-wave oversensing. In addition, the location of the electrodes can assist in detecting the occurrence of AV block. In some examples, either of electrodes 24 and 26 can use a monopolar configuration, where an electrode formed on or by housing 14 is used to sense atrial activity.

[0041] In some examples, electrode 26 may serve as an atrial pacing cathode, and housing 14 of IMD 12 may serve as an atrial sensing anode. Electrode 28 may serve as a ventricular sensing anode, while electrode 30 may serve as a ventricular sensing cathode, or either of electrodes 28 and 30 may be used in a unipolar configuration for sensing electrical activity of the ventricles. In addition, electrodes 28 and 30 may be used to deliver bipolar pacing or other stimulation to LV 40, or either or both of electrodes 28 and 30 may be used in a unipolar configuration with electrodes of housing 14 for delivering unipolar stimulation. Housing 14 may also serve as an anode when electrodes 28 or 30 stimulate. In some examples, both electrodes 28 and 30 may be used in a unipolar configuration for delivering sequential pacing to the ventricles. For example, electrode 28 may provide a first pacing pulse. A delay of approximately 10 milliseconds may be programmed between a pacing pulse from electrode 28 and a second pacing pulse from electrode 30. During the delay, electrode 30 is in a sensing mode. If electrodes 30 sense that the pulses from electrodes 28 successfully captured the heart, then pacing pulses from electrodes 30 are suppressed. However, if the pacing pulses from electrodes 28 did not result in capture, then electrodes 30 provide a second pacing pulse.

[0042] Figure 5 is a functional block diagram of an implantable cardiac therapy device system for delivering pacing therapy according to the present disclosure. Figure 5As shown in , according to an example of the present disclosure, the IMD 12 may include a processor 70, a memory 72, a signal generator 74, a sensing module 76, a telemetry module 78, and a signal analyzer 80. The memory 72 may include computer-readable instructions that, when executed by the processor 70, cause the IMD 12 and the processor 70 to perform various functions attributed to the IMD 12 and the processor 70 herein. The memory 72 may include any volatile, non-volatile, magnetic, optical, or electrical medium, such as a random access memory (RAM), a read-only memory (ROM), a non-volatile RAM (NVRAM), an electrically erasable programmable ROM (EEPROM), a flash memory, or any other digital or analog medium. The processor 70 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 analog logic circuit system. In some examples, the processor 70 may include multiple components, such as any combination of the following: 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 attributed to the processor 70 herein may be implemented as software, firmware, hardware, or any combination thereof. In general, the processor 70 controls the signal generator 74 and the sensing module 76 for sensing cardiac activity and delivering stimulation therapy to the heart 20 of the patient 18 according to one or more selected operating modes, programs or parameters that may be stored in the memory 72.

[0043] Signal generator 74 is configured to generate and deliver electrical stimulation therapy to patient 18. Figure 5 , signal generator 74 is electrically coupled to electrodes 24, 26, 28, and 30 of lead 16. Signal generator 74 is also connected to housing electrode 50 on or integrated with housing 14. For example, signal generator 74 may deliver pacing pulses to heart 20 via at least two of electrodes 24, 26, 28, 30, and 50. In other examples, signal generator 74 delivers stimulation in the form of a signal other than a pulse, such as a sine wave, a square wave, or other substantially continuous time signal.

[0044] The signal generator 74 may include a switch module (not shown), and the processor 70 may use the switch module to select which of the available electrodes are used to deliver electrical stimulation, 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 switch device suitable for selectively coupling stimulation energy to selected electrodes. The electrode sensing module 76 monitors electrical cardiac signals from any combination of electrodes 24, 26, 28, 30, and 50. The sensing module 76 may also include a switch module that the processor 70 controls to select which of the available electrodes are used to sense cardiac activity, depending on which electrode combinations are used in the current sensing configuration.

[0045] The sensing module 76 may include one or more detection channels, each of which may include an amplifier. The detection channels may be used to sense cardiac signals. Some detection channels may detect events (such as R waves or P waves) and provide an indication of the occurrence of such events to the processor 70 and / or the signal analyzer 80. One or more other detection channels may provide a signal to an analog-to-digital converter for conversion to a digital signal for processing or analysis by the processor 70 or the signal analyzer 80.

[0046] For example, the sensing module 76 may include one or more narrowband channels, each of which may include a narrowband filtered sense amplifier that compares the detected signal to a threshold. If the filtered and amplified signal is greater than the threshold, the narrowband channel indicates that an electrical signal event (e.g., depolarization) has occurred. The processor 70 then uses this detection to measure the frequency of the sensed event.

[0047] In one example, at least one narrowband channel may include an R-wave or P-wave amplifier. In some examples, the R-wave and P-wave amplifiers may take the form of an automatic gain control amplifier that provides an adjustable sensing threshold as a function of the measured R-wave or P-wave amplitude. Examples of R-wave and P-wave amplifiers are described in the following U.S. patents: U.S. Patent No. 5,117,824, entitled "APPARATUS FOR MONITORING ELECTRICALPHYSIOLOGIC SIGNALS," issued on June 2, 1992 to Keimel et al., which is incorporated herein by reference in its entirety.

[0048] In some examples, the sensing module 76 includes a broadband channel, which may include an amplifier with a wider passband relative to the narrowband channel. The signal from the electrode selected for coupling to the broadband amplifier may be converted into a multi-bit digital signal by an analog-to-digital converter (ADC), which is provided by, for example, the sensing module 76, the processor 70, or the signal analyzer 80. The processor 70 may analyze the digitized version of the signal from the broadband channel. The processor 70 may use digital signal analysis techniques to characterize the digitized signal from the broadband channel for, for example, detecting and classifying the patient's cardiac rhythm. In other examples, the signal analyzer 80 uses digital signal analysis techniques to characterize the digitized signal from the broadband channel.

[0049] The processor 70 can detect and classify the patient's cardiac rhythm based on the cardiac electrical signals sensed by the sensing module 76 using any of the many signal processing methods known in the art. In other examples, the sensing module 76 provides the sensed cardiac electrical signals directly to the signal analyzer 80. In some examples, the sensing module 76 provides the sensed cardiac electrical signals to both the processor 70 and the signal analyzer 80 for different signal processing. In various examples, the processor 70 can maintain an escape interval counter that can be reset when an R wave is sensed by the sensing module 76. The value of the count that appears in the escape interval counter when reset by the sensed depolarization can be used by the processor 70 to measure the duration of the RR interval, which can be stored in the memory 72 and can be used by the cardiac signal analyzer 80. The processor 70 can use the count in the interval counter to detect rapid arrhythmias, such as ventricular fibrillation or ventricular tachycardia. A portion of memory 72 may be configured as a plurality of recirculating buffers capable of storing a series of measured intervals that may be analyzed by processor 70 to determine whether the patient's heart 20 is currently exhibiting an atrial or ventricular tachyarrhythmia.

[0050] Cardiac resynchronization therapy (CRT) can correct the symptoms of electrical dyssynchrony by providing pacing therapy to one or both ventricles or atria via medical electrical leads to stimulate early activation of the left or right ventricle. By pacing the contraction of the ventricles, the ventricles can be controlled so that the ventricles contract synchronously.

[0051] CRT resynchronization pacing devices operate by delivering pacing stimulation to both ventricles or to one ventricle, obtaining the desired result of more or less simultaneous mechanical contraction and blood ejection from the ventricles. Ideally, each pacing pulse stimulus delivered to the ventricles induces a response from the ventricles. Delivering electrical stimulation that causes the ventricles to respond is generally referred to as capturing the ventricles. For various reasons, a cardiac pacing system may not achieve effective capture of the ventricles. For example, the pacing lead and / or electrode may not be placed in the optimal position. Sensed atrioventricular delay (SAV), paced atrioventricular delay (PAV), and right ventricular pre-excitation may also affect whether the ventricles are effectively captured. Exemplary causes of ineffective capture include too long sensed atrioventricular delay (SAV), too long paced atrioventricular delay (PAV), and RV pre-excitation, which are usually addressed by adjusting the delivery of electrical stimulation to the ventricles. Other exemplary causes of ineffective capture may include: the occurrence of atrial fibrillation (AF); medical electrical leads placed in scar tissue, loss of capture due to lead migration; failure to sense the atria, rates above the upper tracking rate; and right ventricular leads and left ventricular leads being too close together. In addition, pacing leads may migrate or dislodge after a medical device has been implanted, resulting in ineffective capture.

[0052] A specific form of CRT is known as fusion pacing, which generally involves LV-only pacing using electrodes on the left ventricular (LV) medical electrical leads in coordination with intrinsic right ventricular (RV) excitation. Effective fusion requires, for example, synchronization of the timing of LV pacing with the earliest excitation on the RV chamber. For example, in a fusion pacing configuration, the medical device delivers one or more fusion pacing pulses to the late-contracting left ventricle (LV) in order to pre-excite the LV and synchronize the depolarization of the LV with the depolarization of the early-contracting right ventricle (RV). The ventricular excitation of the LV can be "fused" (or "merged") with the ventricular excitation of the RV attributable to the intrinsic conduction of the heart. In this way, the intrinsic and pacing-induced excitation wavefronts can be fused together, so that the depolarization of the LV is resynchronized with the depolarization of the RV. In some cases, the delivered LV pacing therapy can result in a condition known as pseudo fusion, in which the timing of the ventricular output pulse causes the ventricular pacing pulse to fall into the absolute refractory period of the intrinsic conducted R wave, resulting in a pseudo fusion beat.

[0053] As described in detail below, the present disclosure provides a method for verifying LV capture and / or proper synchronization or fusion with other chambers of the heart during delivery of LV pacing in a cardiac treatment device system having only a single-pass left DDD lead without the need to introduce a lead or electrode in the right ventricle, the method providing pacing and sensing of both the ventricles and atria. For example, the present disclosure relates to a cardiac treatment device system having only a single-pass left DDD lead that utilizes far-field electrogram morphology to a) verify LV capture and b) verify proper synchronization with other chambers of the heart, more specifically, fusion with intrinsic conduction. If the morphology analysis indicates LV loss of capture, the device increases pacing output or switches stimulation to other pacing electrode pairs / pacing electrode vectors. On the other hand, if the morphology analysis indicates loss of synchronization, the system adjusts pacing timing. By using only a single-pass left-side DDD lead, the cardiac treatment device system of the present disclosure reduces the risk of complications by introducing less device hardware into the patient's body compared to current treatment systems for delivering CRT (typically including a right atrial lead, a right ventricular lead, and a left ventricular lead).

[0054] Figure 6 is a flow chart of a method for delivering pacing therapy in a cardiac therapy device system according to the present disclosure. Figure 6 As shown, according to an example of the present disclosure, during the delivery of cardiac resynchronization therapy, the processor 70 senses cardiac signals via any one or combination of electrodes 24, 26, 28, 30, and 50 (block 100), and determines whether an arrhythmia is occurring based on or in response to the sensed cardiac signal(s) (block 102). For example, the device 12 may sense far-field cardiac signals from three sensing vectors (block 104), such as a far-field sensing vector formed between the electrode 24 and an electrode formed by the housing 14 of the device 12, a far-field sensing vector formed between the electrode 30 and an electrode formed by the housing 14 of the device 12, and a far-field sensing vector formed between the electrode 24 and the electrode 30 of the lead 16.

[0055] In one example, if it is determined that an arrhythmia is occurring (yes in block 102), the processor 70 may switch a pacing mode associated with the delivery of cardiac resynchronization therapy by the device 12. For example, the processor 70 may switch from a LV DDD pacing mode delivered during CRT pacing to an asynchronous VVI pacing mode (block 104), and may subsequently switch back to the LV DDD pacing mode once the arrhythmia is terminated (yes in block 106). In this manner, once the processor 70 determines that the sensed cardiac signal is associated with a normal or conventional cardiac rhythm, the processor 70 suspends or delays the delivery of CRT pacing (block 108) in order to evaluate intrinsic non-paced electrical conduction for use in generating or determining an intrinsic beat morphology template from the sensed intrinsic cardiac signal (block 110).

[0056] Once the intrinsic beat morphology template is generated (block 110), the processor 70 resumes the delivery of CRT pacing by the device 12 (block 112) and senses paced signals or extrinsic signals via one or more far-field sensing vectors formed between any combination of electrodes 24, 26, 28, 30, and 50. For example, the processor 70 may continue to sense cardiac signals from the far-field sensing vectors formed between electrode 24 and an electrode formed by housing 14 of the device 12, between electrode 30 and an electrode formed by housing 14 of the device 12, and between electrode 24 and electrode 24 of lead 16. The processor 70 determines the beat morphology of the cardiac signal sensed for each far-field sensing vector on a beat-by-beat basis to generate a corresponding far-field cardiac signal beat morphology. The processor 70 compares each of the generated far-field cardiac signal morphologies with the intrinsic beat morphology template and determines a beat morphology match between the far-field beat morphology and the determined intrinsic beat morphology template for each of the generated far-field cardiac signal beat morphologies (block 114). For example, the processor may generate an intrinsic beat morphology template based on the morphology of the intrinsic R-wave of the sensed cardiac signal, and thereby determine a beat morphology match by comparing the induced response or R-wave of the sensed cardiac signal(s) via each of the far-field sensing vector(s) with the intrinsic beat morphology template (i.e., the intrinsic R-wave) (box 114).

[0057] According to one example, the processor 70 may use any known waveform template acquisition and matching algorithm to generate an intrinsic beat morphology template in block 110 and determine a beat morphology matching score (block 114). For example, a wavelet method for template acquisition and ECG signal analysis may be used, as generally described in U.S. Pat. No. 6,393,316 (Gillberg et al.) and U.S. Pat. No. 7,062,315 (Koyrakh et al.), both of which are incorporated herein by reference in their entirety. It should be understood that although a wavelet method for template generation and beat morphology matching is not described, other waveform template matching algorithms known in the art, such as correlation, area of ​​difference, etc., may also be used.

[0058] The intrinsic beat morphology template can be generated by digitizing and averaging a predetermined number of continuously or non-continuously sensed far-field cardiac cycles (e.g., 3 to 8 cardiac cycles). It should be appreciated that template generation can be postponed when the ECG signal is determined to be noisy or the heart rate is not determined to be in normal sinus rhythm (i.e., an arrhythmia is detected). Determination of the beat morphology match score may involve comparison of the peak amplitude, zero crossing, signal width, signal slope, or any other feature of the ECG signal. The comparison may further involve various waveform analysis methods, such as correlated waveform analysis (CWA), regional difference analysis (AD), wavelet transform analysis, or other methods.

[0059] Once a beat morphology match for the evoked response has been determined from the far-field sensing vectors, processor 70 may determine whether LV loss of capture is indicated by determining whether the beat morphology match score (block 114) is greater than a loss of capture threshold (block 116). If the determined beat morphology match score is greater than the loss of capture threshold (yes in block 116), then loss of capture is indicated and thus processor 70 may make a loss of capture adjustment to the pacing therapy (block 118).

[0060] For example, to perform a loss of capture adjustment (block 118), the processor may increase the pacing output or switch to a different pacing electrode. In one example, the loss of capture threshold may be set to a 90% beat morphology match, such that if the match score between the paced beat morphology and the intrinsic beat morphology is determined to be greater than a 90% match, the beat morphology match between the paced beat morphology and the intrinsic beat morphology is determined to be very high, and therefore, it is determined that the currently delivered pacing therapy results in non-capture or loss of capture.

[0061] After making the loss of capture adjustment (block 118), the processor 70 determines whether a predetermined time period for updating the beat morphology template has expired since the last update, and therefore determines whether the beat morphology template is to be updated (yes in block 130). In one example, the predetermined time period may be 16 hours, such that the intrinsic beat morphology template is updated every 16 hours. If the predetermined time period for updating the beat morphology template has not expired (no in block 130), the process is then repeated for the evoked response associated with the next paced beat (block 120). On the other hand, if the predetermined time period for updating the beat morphology template has expired (yes in block 130), indicating that the beat morphology template is to be updated, the processor 70 repeats the determination of the intrinsic beat morphology template from the sensed intrinsic cardiac signal as described above (block 110) to generate an updated intrinsic beat morphology template.

[0062] If the determined beat morphology match between the paced beat morphology and the intrinsic beat morphology is not greater than the loss of capture threshold (No in block 116), the processor 70 may determine whether pseudo fusion is indicated by determining whether the currently determined beat morphology match (block 114) is greater than a pseudo fusion threshold (block 122). If the determined beat morphology match score is greater than the pseudo fusion threshold (Yes in block 122), pseudo fusion is indicated and thus the processor 70 may make pseudo fusion adjustments to the pacing therapy (block 124).

[0063] For example, to perform a pseudo fusion adjustment (block 124), the processor 70 may shorten or reduce the AV delay associated with the currently delivered pacing therapy. In one example, the pseudo fusion threshold may be set to an 80% beat morphology match, such that if the match score between the paced beat morphology and the intrinsic beat morphology is determined to be greater than an 80% match, but less than or equal to a 90% match, the beat morphology match between the paced beat morphology and the intrinsic beat morphology is determined to be high, and thus pseudo fusion is inferred or indicated for the currently delivered pacing therapy.

[0064] After making the pseudo-fusion adjustment (block 124), the processor 70 determines whether a predetermined time period for updating the beat morphology template has expired since the last update, and therefore determines whether to update the beat morphology template (block 130). If the predetermined time period for updating the beat morphology template has not expired (no in block 130), the process is then repeated for the evoked response associated with the next paced beat (block 120). On the other hand, if the predetermined time period for updating the beat morphology template has expired (yes in block 130), the processor 70 repeats the determination of the intrinsic beat morphology template from the sensed intrinsic cardiac signal (block 110) as described above to generate an updated intrinsic beat morphology template.

[0065] If the determined beat morphology match score is not greater than the pseudo fusion capture threshold (No in block 122), the processor 70 may determine whether out-of-synchronization is indicated by determining whether the current beat morphology match (block 114) is less than the out-of-synchronization threshold (block 126). If the determined beat morphology match is less than the out-of-synchronization threshold (Yes in block 126), out-of-synchronization is indicated and thus the processor 70 may make resynchronization adjustments to the pacing therapy (block 128).

[0066] For example, to perform the resynchronization adjustment (block 128), the processor 70 may increase the AV delay associated with the delivered pacing therapy when the device 12 is operating in the LV DDD mode. In one example, the desynchronization threshold may be set to a 20% beat morphology match, such that if the match score between the paced beat morphology and the intrinsic beat morphology is determined to be less than 20%, the beat morphology match between the paced beat morphology and the intrinsic beat morphology is determined to be low, thereby determining that the currently delivered pacing therapy results in a lack of LV-RV resynchronization or results in non-fusion pacing, and desynchronization is inferred or indicated for the currently delivered pacing therapy.

[0067] After making the resynchronization adjustment (block 128), the processor 70 determines whether the predetermined time period for updating the beat morphology template has expired since the last update, and therefore determines whether to update the beat morphology template (block 130). If the predetermined time period for updating the beat morphology template has not expired (no in block 130), the process is then repeated for the evoked response associated with the next paced beat (block 120). On the other hand, if the predetermined time period for updating the beat morphology template has expired (yes in block 130), the processor 70 repeats the determination of the intrinsic beat morphology template from the sensed intrinsic cardiac signal (block 110) as described above to generate an updated intrinsic beat morphology template.

[0068] According to one example of the present disclosure, if the currently determined beat morphology match score is not greater than the loss-of-capture threshold (No in block 116), not greater than the pseudo-fusion threshold (No in block 122), and not less than the desynchronization threshold (No in block 126), and thus indicates neither loss-of-capture nor pseudo-fusion or desynchronization for the current paced beat, the processor 70 determines whether a predetermined time period for updating the beat morphology template has expired since the last update, and thus determines whether to update the beat morphology template (block 130). If the predetermined time period for updating the beat morphology template has not expired (No in block 130), the process is then repeated for the evoked response associated with the next paced beat (block 120). On the other hand, if the predetermined time period for updating the beat morphology template has expired (Yes in block 130), the processor 70 repeats the determination of the intrinsic beat morphology template from the sensed intrinsic cardiac signal as described above (block 110) to generate an updated intrinsic beat morphology template.

[0069] Figure 7 is a flow chart of a method for delivering pacing therapy in a cardiac therapy device system according to the present disclosure. Figure 7 As shown, according to an example of the present disclosure, during the delivery of cardiac resynchronization therapy, the processor 70 senses cardiac signals via any one or combination of electrodes 24, 26, 28, 30, and 50 (block 200), and determines whether an arrhythmia is occurring based on or in response to the sensed cardiac signal(s) (block 202). For example, the device 12 may sense far-field cardiac signals from three far-field sensing vectors, such as a far-field sensing vector formed between the electrode 24 and an electrode formed by the housing 14 of the device 12, a far-field sensing vector formed between the electrode 30 and an electrode formed by the housing 14 of the device 12, and a far-field sensing vector formed between the electrode 24 and the electrode 30 of the lead 16.

[0070] In one example, if it is determined that an arrhythmia is occurring (yes in block 202), the processor 70 may switch a pacing mode associated with the delivery of cardiac resynchronization therapy by the device 12. For example, the processor 70 may switch from a LV DDD pacing mode delivered during CRT pacing to an asynchronous VVI pacing mode (block 104), and then switch back to the LV DDD pacing mode once the arrhythmia is terminated (yes in block 106). In this manner, once the processor 70 determines that the sensed cardiac signal is associated with a normal or conventional cardiac rhythm, the processor 70 suspends or delays the delivery of CRT pacing (block 208) in order to evaluate non-paced intrinsic electrical conduction for use in generating or determining an intrinsic beat morphology template from the sensed intrinsic cardiac signal (block 210).

[0071] Once the intrinsic beat morphology template is determined (block 210), processor 70 resumes delivery of CRT pacing by device 12 (block 212) and senses paced or extrinsic signals via one or more far-field sensing vectors formed between any combination of electrodes 24, 26, 28, 30, and 50, as described above with reference to Figure 6 The processor 70 determines the beat morphology associated with the cardiac signal sensed for each far-field sensing vector on a beat-by-beat basis to generate a corresponding far-field cardiac pacing beat morphology. The processor 70 compares each of the generated far-field cardiac pacing beat morphologies with an intrinsic beat morphology template and determines a beat morphology match between the far-field signal and the determined intrinsic beat morphology template for each of the generated far-field cardiac pacing beat morphologies (block 214).

[0072] According to one example, the processor 70 may utilize any known waveform template acquisition and matching algorithm to generate an intrinsic beat morphology template in block 210 and determine a beat morphology match (block 214), as described above with reference to Figure 6 In one example, as described above, the processor 70 may generate an intrinsic beat morphology template based on the morphology of the intrinsic R-wave of the sensed cardiac signal, and thus, determine a beat morphology match by comparing the induced response or R-wave of the cardiac signal(s) sensed via each of the far-field sensing vector(s) with the intrinsic beat morphology template (i.e., the intrinsic R-wave) (block 214).

[0073] Once a beat morphology match has been determined for the evoked response from one or more far-field sensing vectors (block 214), the processor 70 determines whether LV loss of capture is indicated. For example, the processor 70 may determine whether the beat morphology match score (block 214) is greater than a loss of capture threshold (block 216). If the determined beat morphology match score is greater than the loss of capture threshold (yes in block 216), then loss of capture is indicated. As a result, the processor 70 may make a loss of capture adjustment to the pacing therapy (block 218) to address the indicated loss of capture.

[0074] For example, to perform a loss of capture adjustment (block 218), the processor may increase the pacing output or switch to a different pacing electrode. In one example, the loss of capture threshold may be set to a 90% beat morphology match, such that if the match score between the paced beat morphology and the intrinsic beat morphology is determined to be greater than a 90% match, the beat morphology match between the paced beat morphology and the intrinsic beat morphology is determined to be very high, and thus non-capture or loss of capture is inferred or indicated for the currently delivered pacing therapy.

[0075] After making the loss of capture adjustment (block 218), the processor 70 determines whether to update the intrinsic beat morphology template (block 230). For example, the updating of the template may be programmed to occur within a predetermined time period (such as 16 hours) so that the intrinsic beat morphology template is updated every 16 hours. If the predetermined time period for updating the beat morphology template has not expired, and it is therefore determined that the intrinsic beat morphology template will not be updated (no in block 230), the process is then repeated for the evoked response associated with the next paced beat (block 220). On the other hand, if the predetermined time period for updating the beat morphology template has expired, indicating that the beat morphology template is to be updated (yes in block 230), the processor 70 repeats the determination of the intrinsic beat morphology template from the sensed intrinsic cardiac signal (block 210) as described above to generate an updated intrinsic beat morphology template.

[0076] If the determined beat morphology match between the paced beat morphology and the intrinsic beat morphology is not greater than the loss of capture threshold (No in block 216), the processor 70 may determine whether pseudo fusion is indicated. For example, the processor 70 may determine whether the currently determined beat morphology match (block 214) is greater than the pseudo fusion threshold (block 222). If the determined beat morphology match score is greater than the pseudo fusion threshold (Yes in block 222), pseudo fusion is indicated. Therefore, the processor 70 may make pseudo fusion adjustments to the pacing therapy (block 224).

[0077] For example, to perform a pseudo fusion adjustment (block 124), the processor 70 may shorten or reduce the AV delay associated with the currently delivered pacing therapy. In one example, the pseudo fusion threshold may be set to an 80% beat morphology match, such that if the match score between the paced beat morphology and the intrinsic beat morphology is determined to be greater than an 80% match, but less than or equal to a 90% match, the beat morphology match between the paced beat morphology and the intrinsic beat morphology is determined to be high, and thus pseudo fusion is inferred or indicated for the currently delivered pacing therapy.

[0078] The processor 70 may then determine whether delivery of the pacing therapy adjusted in accordance with the pseudo-fusion adjustment will result in the pacing therapy being delivered too close to the P wave or too close to the R wave. For example, the processor 70 may determine whether the pacing therapy is delivered within a P wave threshold or within an R wave threshold (box 225). In one example, the P wave threshold may be set to a 30 ms window after the end of the P wave of the corresponding cardiac signal, and the R wave threshold may be set to a 30-40 ms window before the R wave of the cardiac signal. If the adjustment to the delivered pacing therapy will result in the pacing therapy being delivered within the P wave threshold or within the R wave threshold (yes in box 225), the processor 70 may adjust the AV delay (box 227).

[0079] Once the adjustment to the AV delay is made (block 227), or if the adjustment to the delivered pacing therapy will not result in the adjusted pacing therapy being delivered within the P wave threshold or the R wave threshold (no in block 225), the processor 70 may determine whether to update the intrinsic beat morphology template (block 230), as described above. If the predetermined time period for updating the beat morphology template has not expired, and it is therefore determined that the intrinsic beat morphology template will not be updated (no in block 230), the process is then repeated for the evoked response associated with the next paced beat (block 220). On the other hand, if the predetermined time period for updating the beat morphology template has expired, indicating that the beat morphology template is to be updated (yes in block 230), the processor 70 repeats the determination of the intrinsic beat morphology template from the sensed intrinsic cardiac signal (block 210) as described above to generate an updated intrinsic beat morphology template.

[0080] If the determined beat morphology match score is not greater than the pseudo fusion threshold (No in block 222), the processor 70 may determine whether out-of-synchronization is indicated. For example, the processor 70 may determine whether the current beat morphology match (block 214) is less than the out-of-synchronization threshold (block 226). If the determined beat morphology match is less than the out-of-synchronization threshold (Yes in block 226), out-of-synchronization is indicated and thus the processor 70 may make an out-of-synchronization adjustment to the pacing therapy (block 228).

[0081] For example, to perform an out-of-sync adjustment (block 228), the processor 70 may increase the AV delay associated with the delivered pacing therapy when the device 12 is operating in the LV DDD mode. In one example, the out-of-sync threshold of block 226 may be set to a 20% beat morphology match such that if the beat morphology match score between the paced beat morphology and the intrinsic beat morphology is determined to be low, and therefore out-of-sync or non-fused pacing is indicated for the currently delivered pacing therapy.

[0082] The processor 70 may then determine whether delivery of the pacing therapy adjusted in accordance with the resynchronization adjustment (block 228) will result in the pacing therapy being delivered too close to the P wave or too close to the R wave. For example, the processor 70 may determine whether the pacing therapy is delivered within the P wave threshold or within the R wave threshold (block 225), as described above. If the adjustment to the delivered pacing therapy will result in the pacing therapy being delivered within the P wave threshold or within the R wave threshold (yes in block 225), the processor 70 may adjust the AV delay (block 227).

[0083] Once the adjustment to the AV delay is made (block 227), or if the adjustment to the delivered pacing therapy will not result in the adjusted pacing therapy being delivered within the P wave threshold or the R wave threshold (no in block 225), the processor 70 may determine whether to update the intrinsic beat morphology template (block 230), as described above. If the predetermined time period for updating the beat morphology template has not expired, and it is therefore determined that the intrinsic beat morphology template will not be updated (no in block 230), the process is then repeated for the evoked response associated with the next paced beat (block 220). On the other hand, if the predetermined time period for updating the beat morphology template has expired, indicating that the beat morphology template is to be updated (yes in block 230), the processor 70 repeats the determination of the intrinsic beat morphology template from the sensed intrinsic cardiac signal (block 210) as described above to generate an updated intrinsic beat morphology template.

[0084] According to one example of the present disclosure, if the currently determined beat morphology match score is not greater than the loss of capture threshold (No in box 216), not greater than the pseudo fusion threshold (No in box 222), and not less than the desynchronization threshold (No in box 226), and therefore indicates neither loss of capture nor pseudo fusion or desynchronization for the current paced beat, the processor 70 determines whether to update the intrinsic beat morphology template (box 230), as described above. If the predetermined time period for updating the beat morphology template has not expired, and therefore it is determined that the intrinsic beat morphology template will not be updated (No in box 230), then the process is repeated for the evoked response associated with the next paced beat (box 220). On the other hand, if the predetermined time period for updating the beat morphology template has expired, indicating that the beat morphology template will be updated (Yes in box 230), the processor 70 repeats the determination of the intrinsic beat morphology template from the sensed intrinsic cardiac signal as described above (box 210) to generate an updated intrinsic beat morphology template.

[0085] In examples where more than one far-field sensor vector is used, such as a far-field sensing vector formed between electrode 24 and an electrode formed by housing 14 of device 12, a far-field sensing vector formed between electrode 30 and an electrode formed by housing 14 of device 12, and a far-field sensing vector formed between electrode 24 and electrode 30 of lead 16, the determination of a beat morphology match (blocks 114, 214) includes comparing the pacing beat morphology for each far-field sensing vector to an intrinsic beat morphology template. Processor 70 may then use the pacing beat morphology that is most different from the intrinsic beat morphology template to determine whether loss of capture, pseudo-fusion, or loss of synchronization is indicated for the current paced beat. Thus, in an example where the pacing beat morphology match determined for the far-field sensing vector between electrode 24 and the electrode formed by housing 14 of device 12 is 91%, the pacing beat morphology match determined for the far-field sensing vector formed between electrode 30 and the electrode formed by housing 14 of device 12 is 85%, and the pacing beat morphology match determined for the far-field sensing vector formed between electrode 24 and electrode 30 of lead 16 is 43%, processor 70 will use the pacing beat morphology match score of 43% when determining whether loss of capture, pseudo-fusion, or loss of synchronization is indicated for the current pacing beat, as described above. In another example, processor 70 may average the pacing beat morphology matches determined for each far-field sensing vector, i.e., using the example beat morphology matches described above, the averages of 91%, 81%, and 43%.

[0086] In this manner, a method for delivering pacing therapy in a cardiac therapy device system according to the present disclosure includes: collecting pacing R-wave morphologies associated with cardiac signals sensed by a single far-field sensor formed by electrodes of a single-pass coronary sinus lead, or each of a plurality of far-field sensing vectors formed by electrodes of a single-pass coronary sinus lead, comparing the R-wave morphology of each vector with an intrinsic R-wave morphology template, and in response to the comparison, generating a pacing beat morphology match for a current pacing beat, and determining whether there is a degree of dissimilarity between the sensed R-wave or an induced response associated with the delivered pacing therapy and the intrinsic R-wave, which would indicate that the delivered pacing therapy is effectively pacing the patient's heart.

[0087] In this way, the present disclosure sets forth a method of adaptive cardiac resynchronization in a system using only a single-pass coronary sinus lead, the method comprising utilizing far-field electrogram morphology to verify LV capture and verify proper synchronization with other chambers of the heart, more specifically, fusion with intrinsic conduction. If the morphology analysis indicates LV loss of capture, the device increases pacing output or switches stimulation to other pacing electrode pairs / pacing electrode vectors. On the other hand, if the morphology analysis indicates loss of synchronization, the system adjusts pacing timing. Compared to current treatment systems for delivering CRT (typically including a right atrial lead, a right ventricular lead, and a left ventricular lead), by using only a single-pass left DDD lead, the cardiac treatment device system of the present disclosure reduces the risk of complications because less device hardware is introduced into the patient's body.

[0088] The techniques described in the present disclosure (including those attributable to the IMD 12, processor 70, programmer 22, or various constituent components) may be implemented, at least in part, in hardware, software, firmware, or any combination thereof. For example, aspects of the techniques may be implemented within one or more processors including one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic circuitry, as well as any combination of such components embodied in a programmer (such as a physician programmer or patient programmer, stimulator, image processing device, or other device). The terms "module," "processor," or "processing circuitry" may generally refer to any of the foregoing logic circuitry, either independently or in combination with other logic circuitry, or any other equivalent circuitry.

[0089] Such hardware, software and / or firmware may be implemented in the same device or in separate devices to support the various operations and functions described in the present disclosure. In addition, any of the described units, modules or components may be implemented together, or may be implemented separately as discrete but interoperable logical devices. Depicting different features as modules or units is intended to emphasize different functional aspects, and does not necessarily imply that such modules or units must be implemented by separate hardware or software components. Instead, the functions associated with one or more modules or units may be performed by separate hardware or software components, or may be integrated in common or separate hardware or software components.

[0090] When implemented in software, the functionality attributed to the systems, devices, and techniques described in this disclosure may be embodied as instructions on a computer-readable medium (such as RAM, ROM, NVRAM, EEPROM, flash memory, magnetic data storage media, optical data storage media, etc.). These instructions may be executed by one or more processors to support one or more aspects of the functionality described in this disclosure.

[0091] The present disclosure has been provided with reference to illustrative embodiments, and the disclosure is not intended to be interpreted in a limiting sense. As previously stated, those skilled in the art will recognize that various other illustrative applications can use the techniques described herein to take advantage of the beneficial properties of the apparatus and methods described herein. Various modifications of the illustrative embodiments and additional embodiments of the present disclosure will be apparent when referring to this specification.

Claims

1. An implantable medical device system for delivering left ventricular (LV) cardiac pacing therapy to a patient, comprising: Implantable medical device housing; a single implanted lead, the single implanted lead comprising a single-pass coronary sinus lead capable of being electrically coupled to the implantable medical device housing; a plurality of electrodes positioned along one or both of the single-pass coronary sinus lead and the implantable medical device housing, the single-pass coronary sinus lead being proximate to both the atria and ventricles, the plurality of electrodes being configured for sensing far-field cardiac signals of the patient and delivering LV cardiac pacing therapy, the plurality of electrodes comprising a right atrial electrode positioned in the right atrium, a left ventricular electrode positioned proximate to the left ventricle, and a housing electrode positioned on the implantable medical device housing; as well as a processor positioned within the implantable medical device housing and configured to: sensing far-field cardiac signals via one or more far-field sensing vectors formed between any combination of the right atrial electrode, the left ventricular electrode, and the housing electrode, determining a beat morphology corresponding to the far-field cardiac signal sensed for each of the far-field sensing vectors to generate a corresponding far-field beat morphology, determining a beat morphology match between each of the far-field beat morphologies and an intrinsic beat morphology template, determining one of LV loss of capture, pseudo-fusion, and desynchronization in response to the determined beat morphology match, In response to one of LV loss of capture, pseudo fusion, and desynchronization determined in response to the determined beat morphology match, performing one of a loss of capture adjustment, a pseudo fusion adjustment, and a resynchronization adjustment to generate an adjusted LV cardiac pacing therapy, and The adjusted LV cardiac pacing therapy is delivered via an electrode of the plurality of electrodes.

2. The implantable medical device system according to claim 1, wherein: The processor is configured to determine whether the beat morphology match is one of greater than a loss-of-capture threshold, not greater than the loss-of-capture threshold and greater than a pseudo-fusion threshold, and less than a loss-of-synchronization threshold.

3. The implantable medical device system according to claim 2, wherein: The loss of capture threshold is 90% beat morphology matching, the pseudo-fusion threshold is 80% beat morphology matching, and the desynchronization threshold is 20% beat morphology matching score.

4. The implantable medical device system according to claim 2, wherein: The processor is configured to, in response to the beat morphology match being greater than the loss-of-capture threshold, perform one of increasing a pacing output of a delivered LV cardiac pacing therapy and switching the delivery of the LV cardiac pacing therapy from the electrode of the plurality of electrodes to another electrode of the plurality of electrodes.

5. The implantable medical device system according to any one of claims 2 to 4, characterized in that: The processor is configured to, in response to the beat morphology match being no greater than the loss-of-capture threshold and greater than the false fusion threshold, reduce AV delay associated with the delivered LV cardiac pacing therapy.

6. The implantable medical device system according to any one of claims 2 to 4, characterized in that: The processor is configured to, in response to the beat morphology match being less than the desynchronization threshold, increase an AV delay associated with the delivered LV cardiac pacing therapy.

7. The implantable medical device system according to any one of claims 2 to 4, characterized in that: The processor is configured to determine whether the LV cardiac pacing therapy is delivered within one of a P wave threshold and an R wave threshold, and in response to the LV cardiac pacing therapy being delivered within one of the P wave threshold and the R wave threshold, adjust an AV delay associated with the delivered LV cardiac pacing therapy.

8. The implantable medical device system according to claim 7, wherein: The P wave threshold is 30 ms and the R wave threshold is between 30 ms and 40 ms.

9. A non-transitory computer readable medium comprising instructions stored thereon, which instructions, when executed by a processor included in a medical device, cause the processor to perform the operations defined in claims 1-8.

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