Cardiovascular extracardiac pacing system for delivering composite pacing pulses

Abstract

An implantable medical device is configured to control a therapy module to couple a capacitor array including a plurality of capacitors to a plurality of extravascular electrodes, and to control the therapy module to deliver a composite pacing pulse to a heart of a patient via the plurality of extravascular electrodes by sequentially discharging at least a portion of the plurality of capacitors to generate a series of at least two individual pulses that define the composite pacing pulse.

Description

[0001] This application is a divisional application of the invention patent application entitled “Extracardiac Cardiac Pacing System for Delivering Composite Pacing Pulses”, with international application number PCT / US2016 / 064762, international application date of December 2, 2016, and Chinese national phase application number 201680070459.6. Technical Field

[0002] This disclosure generally relates to implantable medical devices, and more particularly to a system, apparatus, and method for delivering cardiac pacing pulses using a cardiovascular external electrode. Background Technology

[0003] Various implantable medical devices (IMDs) for delivering treatment, monitoring a patient's physiological condition, or combinations thereof, have been clinically implanted or proposed for clinical implantation in patients. Some IMDs may employ one or more elongated electrical leads carrying stimulating electrodes, sensing electrodes, and / or other sensors. IMDs can deliver treatment or monitor the condition of various organs, nerves, muscles, or tissues, such as the heart, brain, stomach, spinal cord, and pelvic floor. Implantable medical leads can be configured to position electrodes or other sensors at desired locations to deliver electrical stimulation or sense physiological conditions. For example, electrodes or sensors may be carried along the distal portion of the lead, which extends subcutaneously, intravenously, or submuscularly. The proximal portion of the lead may be coupled to an implantable medical device housing containing circuitry such as signal generation and / or sensing circuitry.

[0004] Some intracardiac devices (IMDs), such as pacemakers or implantable cardioverter defibrillators (ICDs), deliver therapeutic electrical stimulation to a patient's heart via electrodes carried by one or more implantable leads and / or the pacemaker's housing. These leads may be venous, for example, advanced into the heart through one or more veins to position the endocardial electrodes in close contact with cardiac tissue. Other leads may be non-venous leads implanted outside the heart, such as in the epicardium, pericardium, or subcutaneously. The electrodes are used to deliver electrical stimulation pulses to the heart to address abnormal rhythms.

[0005] An ICD capable of delivering electrical stimulation to treat aberrant heart rhythms typically senses signals representing the heart's inherent depolarization and analyzes the sensed signals to identify aberrant rhythms. Upon detecting an aberrant rhythm, the device can deliver appropriate electrical stimulation therapy to restore a more normal rhythm. For example, when bradycardia or tachycardia is detected using endocardial or epicardial electrodes, a pacemaker or ICD can deliver low-pressure pacing pulses to the heart. When rapid ventricular tachycardia or fibrillation is detected using electrodes carried by transvenous or non-transvenous leads, an ICD can deliver high-pressure cardioversion or defibrillation electrodes to the heart. The type of treatment delivered and its effectiveness in restoring a normal rhythm depends at least in part on the type of electrode used to deliver the electrical stimulation and its location relative to the cardiac tissue. Summary of the Invention

[0006] In general, this disclosure relates to techniques for delivering cardiovascular external pacing pulses via implantable medical devices. Pacemakers or ICDs operating according to the techniques disclosed herein use cardiovascular external electrodes to deliver a series of fused low-voltage electrical pulses to generate a composite cardiac pacing pulse defined by said fused low-voltage pulses. The composite pacing pulse delivered using the cardiovascular external electrodes can capture the heart when the cumulative pulse energy of individual pulses exceeds a cardiac capture threshold, or even when the energy of individual pulses is less than said capture threshold.

[0007] In one example, this disclosure provides an implantable medical device including a pacing control module and a treatment module. The treatment module has a capacitor array comprising a plurality of capacitors and is configured to couple the capacitor array to a cardiovascular external electrode to deliver a composite pacing pulse to a patient's heart. The pacing control module is coupled to the treatment module and is configured to control the treatment module to sequentially discharge at least a portion of the capacitors to generate a sequence / series of at least two individual pulses defining the composite pacing pulse.

[0008] In another example, this disclosure provides a method performed by an implantable medical device. The method includes: controlling a treatment module to couple a capacitor array comprising a plurality of capacitors to a cardiovascular external electrode; and controlling the treatment module by a pacing control module to deliver a composite pacing pulse to a patient's heart via the cardiovascular external electrode in such a manner that at least a portion of the capacitors are sequentially discharged to generate a series / series of at least two separate pulses defining the composite pacing pulse.

[0009] In another example, this disclosure provides a non-transitory computer-readable storage medium comprising a set of instructions, which, when executed by a control module of an implantable medical device, cause the implantable medical device to control a treatment module to couple a capacitor array comprising a plurality of capacitors to a cardiovascular external electrode; and to control the treatment module to deliver a composite pacing pulse to a patient’s heart via the cardiovascular external electrode by sequentially discharging at least a portion of the capacitors to generate a series / series of at least two separate pulses defining the composite pacing pulse.

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

[0011] Figures 1A to 1B This is a conceptual diagram of a patient with an implanted IMD system, which includes a subcutaneously implanted IMD coupled to extra-cardiovascular sensing, pacing, and cardioversion / defibrillation leads for delivering extra-cardiovascular pacing pulses.

[0012] Figure 1C yes Figure 1A A schematic diagram of alternative implantation sites for cardiovascular external sensing, pacing, and cardioversion / defibrillation leads in the IMD system.

[0013] Figure 2A It is a demonstration Figure 1A A conceptual diagram of the distal portion of another example of an implantable electrical lead with alternative electrode arrangements.

[0014] Figure 2B It is a demonstration Figure 1A Having similar Figure 2A A conceptual diagram of the distal portion of another example of an external cardiovascular lead with electrode arrangement but a lead body of a different shape along its distal portion.

[0015] Figure 3 It is based on an example Figure 1A A schematic diagram of an IMD.

[0016] Figure 4A It is possible to be by Figure 1A A depiction of an example of IMD generation and delivery to pace a patient’s heart with a compound pacing pulse using a cardiovascular external electrode.

[0017] Figure 4B This is based on a description of a compound pacing pulse from another example.

[0018] Figure 5This is a schematic diagram of an example pacing control module and a low-pressure therapy module.

[0019] Figure 6 It is based on an example Figure 5 A schematic diagram of the pacing control module.

[0020] Figure 7 This is a schematic diagram of a capacitor selection and control module based on an example.

[0021] Figure 8 This is a flowchart of an example method for delivering cardiovascular external pacing pulses.

[0022] Figure 9 It is a flowchart of a method that can be executed to select a capacitor sequence for delivering a compound pacing pulse.

[0023] Figure 10 This is a flowchart based on another example of a method for delivering composite pacing pulses.

[0024] Figure 11 This is a conceptual diagram of an IMD coupled to a vein-guided lead.

[0025] Figure 12A yes Figure 11 A conceptual diagram of the IMD and the proximal portion of the cardiovascular external lead.

[0026] Figure 12B yes Figure 11 The diagram shows the concept of the IMD and the proximal portion of the venous access.

[0027] Figure 13 This is a concept diagram based on another example of a low-pressure treatment module.

[0028] Figure 14 It can be made by Figure 13 A conceptual diagram of an example of a low-pressure therapy module delivering a compound pacing pulse.

[0029] Figure 15 It is used for programmable configuration Figure 11 The flowchart describes a method for operating an IMD to deliver multichannel multichamber cardiac pacing by combining a transvenous lead with a cardiovascular external lead and a cardiovascular external electrode. Detailed Implementation

[0030] In general, this disclosure describes a technique for delivering low-pressure pacing pulses using an extra-cardiovascular electrode that does not directly contact cardiac tissue. As used herein, the term "extra-cardiovascular" refers to a location outside the blood vessels, heart, and pericardium surrounding the patient's heart. The implantable electrode carried by the extra-cardiovascular lead can be positioned outside the thoracic cavity (outside the pleural cavity and sternum) or inside the thoracic cavity (below the pleural cavity or sternum), but not in close contact with myocardial tissue.

[0031] Pacing pulses delivered by endocardial or epicardial electrodes are generally not painful for patients. Pacing pulses delivered by extracardiac electrodes may cause extracardiac capture of nerves and skeletal muscle recruitment, depending on the voltage amplitude of the pacing pulse, which may cause noticeable sensations and, in some cases, pain or discomfort. For a given pacing pulse width, the pulse voltage amplitude required to capture the heart when pacing with extracardiac electrodes (such as subcutaneous or submuscular electrodes) may exceed a level of acceptable comfort for the patient. Pacing pulses with lower voltage amplitudes may require relatively longer pulse widths when delivered by extracardiac electrodes to deliver sufficient energy for heart capture. Due to the relatively rapid decay rate of the pulse amplitude, the longer pulse width may exceed the capacity of a typical low-voltage pacing capacitor. Because the pacing pulse is delivered as the pacing capacitor discharges across the pacing electrode vector, the pacing pulse amplitude may decay below the effective voltage amplitude before the required pacing pulse width fails, resulting in a pacing pulse with insufficient energy to capture the heart.

[0032] As disclosed herein, an implantable extracardiac medical device system is configured to continuously deliver multiple individual electrical pulses within a selected pacing pulse width to generate a composite low-pressure pacing pulse. This composite low-pressure pacing pulse has a total pulse width long enough to successfully pac the heart and a sufficiently low pulse amplitude acceptable to the patient. The composite pacing pulse can be delivered using an extracardiac pacing electrode that does not directly contact myocardial tissue. The energy of each individual pulse is temporally “fused” or effectively accumulated to generate a total pulse energy within the composite pulse width sufficient to induce depolarization of myocardial tissue, even if each individual pulse (if delivered individually) is insufficient to induce capture of myocardial tissue.

[0033] The techniques disclosed herein can be implemented in any implantable pacemaker or ICD, and specifically in pacemakers or ICDs coupled to external cardiovascular electrodes. The electrodes can be carried by medical electrical leads extending from the pacemaker or ICD and / or by the housing of the pacemaker or ICD. The techniques disclosed herein are not necessarily limited to implantable systems, and can be implemented in external pacemakers or ICDs using surface skin electrodes or percutaneous electrodes.

[0034] Figure 1A and Figure 1B This is a conceptual diagram of a patient 12 with an implanted extra-cardiovascular IMD system 10, which includes a subcutaneously implanted IMD 14 coupled to extra-cardiovascular sensing, pacing, and cardioversion / defibrillation (CV / DF) leads 16. Figure 1A This is a frontal view of patient 12, and Figure 1B This is a landscape view of patient 12. Figure 1A and Figure 1B In the illustrative embodiment, IMD 14 is an ICD configured to deliver high-voltage cardioversion / defibrillation (CV / DF) shocks in addition to low-voltage cardiovascular pacing pulses delivered using the techniques disclosed herein.

[0035] The IMD 14 includes a housing 15 and a connector assembly 17 for receiving a cardiovascular external lead 16. The IMD 14 uses electrodes carried by the lead 16 to acquire cardiac electrical signals from a heart 26 and is configured to deliver cardiac pacing pulses to the heart 26 using the cardiovascular external electrode carried by the lead 16. As will be described herein, the IMD 14 includes a pacing control module that controls a pacing capacitor array to deliver composite pacing pulses, each comprising a series of fused low-voltage pulses. The composite pacing pulses have a pulse amplitude that can be set to a level comfortable for the patient (e.g., less than 20 V) and a pulse width long enough to successfully capture and pace the heart using the cardiovascular external electrode.

[0036] The cardiac electrical signals received by the IMD 14 are used to determine the patient's cardiac rhythm and to provide appropriate pacing therapy as needed, such as, for example, bradycardia pacing, antitachycardia pacing (ATP), or pacing to treat cardiac arrest due to atrioventricular block or after cardioversion or defibrillation. When the IMD 14 is implemented as an ICD, it is configured to detect shockable rhythms (e.g., non-sinus tachycardia and ventricular fibrillation) and deliver CV / DF shock therapy via defibrillation electrodes 24A and / or 24B carried by leads 16. In other examples, the IMD 14 may be configured as a pacemaker to deliver low-pressure pacing therapy without the ability to deliver high-pressure CV / DF shock therapy. In this case, leads 16 may not include defibrillation electrodes 24A and 24B.

[0037] Lead 16 includes a proximal end 27 connected to IMD 14 and a distal portion 25 carrying electrodes 24A, 24B, 28A, 28B and 30. All or part of the housing 15 of IMD 14 may be formed of a conductive material such as titanium or titanium alloy and coupled to the internal IMD circuitry to act as electrodes, sometimes referred to as “metal-cased electrodes”.

[0038] Electrodes 24A and 24B are referred to as defibrillation electrodes because they can be used together or in combination with the conductive housing 15 of IMD 14 to deliver high-voltage CV / DF shocks. Electrodes 24A and 24B may be elongated coil electrodes and generally have a relatively higher surface area for delivering high-voltage electrical stimulation pulses compared to low-voltage pacing and sensing electrodes 28A, 28B, and 30. However, electrodes 24A and 24B can also be used to provide pacing, sensing, or both pacing and sensing functions in addition to or in lieu of high-voltage stimulation therapy. In this sense, the use of the term "defibrillation electrode" herein should not be construed as limiting electrodes 24A and 24B to high-voltage CV / DF therapy applications only. As described herein, electrodes 24A and / or 24B can be used in pacing electrode vectors to deliver compound extravascular pacing pulses.

[0039] In some cases, defibrillator electrodes 24A and 24B may form a defibrillator electrode together because they are configured to be activated simultaneously. Alternatively, defibrillator electrodes 24A and 24B may form separate defibrillator electrodes, in which case these electrodes 24A and 24B can each be activated independently. In some instances, defibrillator electrodes 24A and 24B are coupled to an electrically isolating conductor, and IMD 14 may include a switching mechanism to allow electrodes 24A and 24B to be used as a single defibrillator electrode (e.g., activated simultaneously to form a common cathode or anode) or as separate defibrillator electrodes (e.g., activated separately, one as a cathode and one as an anode; or activated one at a time, one as an anode or cathode and the other remaining inactive). In other examples, lead 16 may include a single defibrillator electrode instead of two defibrillator electrodes as shown.

[0040] Electrodes 28A, 28B, and 30 are relatively small surface area electrodes used for delivering low-pressure pacing pulses and for sensing cardiac electrical signals. Electrodes 28A, 28B, and 30 are referred to as pacing / sensing electrodes because they are generally configured for low-pressure applications, for example, as either a cathode or anode for delivering pacing pulses and / or sensing cardiac electrical signals. In some instances, electrodes 28A, 28B, and 30 may provide pacing functionality only, sensing functionality only, or both.

[0041] exist Figure 1A and Figure 1B In the example shown, electrodes 28A and 28B are located between defibrillator electrodes 24A and 24B, and electrode 30 is located distal to defibrillator electrode 24A. Figure 1A In the example, electrodes 28A and 28B are shown as ring electrodes, and electrode 30 is shown as a hemispherical tip electrode. However, electrodes 28A, 28B, and 30 can comprise any type of electrode from a variety of different types, including ring electrodes, short coil electrodes, paddle electrodes, hemispherical electrodes, directional electrodes, segmented electrodes, etc., and can be positioned at any location along lead body 18. Furthermore, electrodes 28A, 28B, and 30 can have similar types, shapes, sizes, and materials, or they can differ from each other.

[0042] ECG signals can be acquired using any combination of sensing vectors including electrodes 28A, 28B, 30 and housing 15. In some examples, the sensing vectors may even include defibrillation electrodes 24A and / or 24B. The IMD 14 may include more than one sensing channel, allowing the IMD 14 to select sensing electrode vectors two at a time for monitoring shockable rhythms or determining the need for cardiac pacing.

[0043] Pacing pulses can be delivered using any combination of electrodes 24A, 24B, 28A, 28B, 30 and housing 15. The pacing electrode vector selected for delivering the pacing pulse can be chosen based on pacing electrode vector impedance measurements and capture threshold tests. For example, a pacing vector with the lowest impedance and / or lowest composite pacing pulse width for capturing the heart with a programmed pacing pulse voltage amplitude can be selected from electrodes 24A, 24B, 28A, 28B, 30 and housing 15. The pacing pulse voltage amplitude can be programmed to be below a threshold of pain and discomfort, which can be based on individual patient testing and / or clinical data. In some examples, a pacing electrode vector is selected between one of the pacing / sensing electrodes 28A, 28B, or 30 and one of the defibrillation electrodes 24A or 24B. In other examples, a pacing electrode vector is selected between two electrodes of the pacing / sensing electrodes 28A, 28B, and / or 30. Compared to a sensing vector including the IMD housing 15, selecting a pacing electrode vector between two electrodes carried by the distal portion 25 of the lead 16 can reduce skeletal muscle recruitment when delivering cardiovascular pacing pulses.

[0044] In some instances, the electrodes 24A, 24B, 28A, 28B, and / or 30 of lead 16 may be shaped, oriented, designed, or otherwise configured to reduce extracardiac stimulation. For example, the electrodes 24A, 24B, and / or electrodes 28A, 28B, and / or 30 of lead 16 may be shaped, oriented, designed, partially insulated, or otherwise configured to concentrate, direct, or point the electrodes 24A, 24B, and / or electrodes 28A, 28B, and / or 30 toward the heart 26. In this way, electrical stimulation pulses delivered via lead 16 are directed toward the heart 26 rather than outward toward skeletal muscle. For example, the electrodes 24A, 24B, and / or electrodes 28A, 28B, and / or 30 of lead 16 may be partially coated or covered on one side or in different areas with a polymer (e.g., polyurethane) or other coating material (e.g., tantalum pentoxide) to direct electrical energy toward the heart 26 rather than outward toward skeletal muscle. For example, in the case of a ring electrode, the ring electrode may be partially coated with a polymer or other material to form a semi-ring electrode, a quarter-ring electrode, or other partially ring electrode. When the IMD 14 delivers pacing pulses via electrodes 24A, 24B, 28A, 28B and / or 30, the recruitment of peripheral skeletal muscles that may cause discomfort to the patient by the pacing pulses may be reduced by shaping, orienting, or partially insulating electrodes in order to concentrate or direct electrical energy toward the heart 26.

[0045] In various examples, electrodes 24A, 24B, 28A, 28B, and 30 may be carried along lead 16 at locations other than those shown and in different arrangements relative to each other, but are generally positioned to acquire cardiac electrical signals with acceptable cardiac signal strength for sensing cardiac events (such as R-wave signals occurring during ventricular depolarization) and to deliver low-pressure pacing pulses for successful capture of the patient's heart 26. Although three pacing / sensing electrodes 28A, 28B, and 30 are shown along lead 16, in other examples, lead 16 may carry more or fewer pacing / sensing electrodes. Other arrangements of defibrillation electrodes and pacing / sensing electrodes carried by cardiovascular external leads that can be used to deliver compound pacing pulses are generally disclosed in pending U.S. Patent Application No. 2015 / 0306375 (Marshall et al.) and U.S. Patent Publication No. 2015 / 0306410 (Marshall et al.). In other examples, lead 16 may carry a single pacing / sensing electrode for use with housing 15 as a pacing cathode (or anode) electrode, or may carry a defibrillation electrode (e.g., defibrillation electrode 24A or 24B) for use as a return anode (or cathode) electrode.

[0046] In other examples, a dedicated pacing electrode and a separate dedicated sensing electrode may be carried by lead 16 or another lead coupled to IMD 14. It should be understood that one or more leads may be coupled to IMD 14 for connecting at least one defibrillation electrode and at least one pacing and sensing electrode to IMD 14 for monitoring cardiac electrical signals, delivering pacing pulses, and delivering CV / DF shock therapy when IMD 14 is configured as an ICD. Pacing therapy that can be delivered by IMD 14 using any of electrodes 24A, 24B, 28A, 28B, 30, and housing 15 may include, but is not limited to: bradycardia pacing, ATP, post-shock pacing for treating bradycardia or cardiac arrest after a CV / DF shock, and pacing during cardiac arrest due to atrioventricular block. Alternatively, the composite pulse delivered using any of electrodes 24A, 24B, 28A, 28B, 30 and / or housing 15 according to the techniques disclosed herein may be an entrained pulse for sensing rapid arrhythmias delivered prior to a T-shock, or may include a pulse for sensing rapid arrhythmias within a high-frequency pulse burst (e.g., at 50 Hz), for example, for testing anti-tachyarrhythmic therapy in a clinical setting. The methods disclosed herein for delivering composite pacing pulses may be used in conjunction with the rapid arrhythmia sensing methods generally disclosed in U.S. Patent Application No. 62 / 262,500 (Attorney-in-charge: C00012278.USP1) and the corresponding U.S. Patent Application No. C00012278.USU2, filed on the same day thereafter.

[0047] Figure 1B This is a transverse view of patient 12, showing the distal portion 25 of a guide 16 extending below the sternum, for example, at least partially in or adjacent to the anterior mediastinum 36. The guide 16 is... Figure 1A and Figure 1B The lead is shown to be at least partially implanted in a substernal location, such as between the heart and the thoracic cavity 32 or sternum 22. In one such configuration, the proximal portion of the lead 16 extends subcutaneously from the IMD 14 (which is implanted near the midaxillary line on the left side of the patient 12) toward the sternum 22. At a location near the xiphoid process 20, the lead 16 is bent or rotated superiorly, and the distal portion 25 of the lead 16 (with its carrier electrodes 24A, 24B, 28A, 28B, and 30) extends substernally in the anterior mediastinum 36, below or beneath the sternum 22.

[0048] The anterior mediastinum 36 is laterally defined by the pleura 39, posteriorly by the pericardium 38, and anteriorly by the sternum 22. In some instances, the anterior wall of the anterior mediastinum 36 may also be formed by the transverse sternotomy muscle and one or more costal cartilages. The anterior mediastinum 36 includes a certain amount of loose connective tissue (e.g., celluloid), adipose tissue, some lymphatic vessels, lymph nodes, substernal muscle tissue, small lateral branches of the internal thoracic artery or vein, and the thymus. In one example, the distal portion of the lead 16 extends substantially along the posterior side of the sternum 22 within the loose connective tissue and / or substernal muscle tissue of the anterior mediastinum 36. The lead 16 may be implanted at least partially in other extracardiac intrathoracic locations, such as along the pleural cavity 32 or along or adjacent to the pericardium or within the pleural cavity.

[0049] The IMD 14 can also be implanted in other subcutaneous locations in the patient 12, such as further posteriorly along the trunk towards the posterior axillary line, further anteriorly along the trunk towards the anterior axillary line, in the chest region, or in other locations in the patient 12. In an example where the IMD 14 is implanted in the chest, the lead 16 can follow different paths, such as crossing the upper chest region and descending along the sternum 22. When the IMD 14 is implanted in the pectoral muscle region, the system 10 may include a second lead extending along the patient's left side and including a defibrillation electrode and / or one or more pacing electrodes positioned along the patient's left side to act as the anode or cathode of a treatment delivery vector, which includes an anterior electrode for delivering electrical stimulation to the heart 26 located therebetween.

[0050] Figure 1C This is a schematic diagram of alternative implantation sites for lead 16. In other examples, the distal portion of lead 16 can be implanted in locations other than... Figure 1A Other extravascular locations besides the substernal location shown. For example, such as... Figure 1CAs shown, the suture 16 can be implanted subcutaneously or submuscularly between the skin and the thoracic cavity 32 or between the skin and the sternum 22. Figure 1A As shown, the lead 16 may extend subcutaneously from the IMD 14 toward the xiphoid process 20, but not along the posterior side of the sternum 22 below the sternum. The lead 16 may bend or turn near the xiphoid process 20 and extend subcutaneously or submuscularly above the sternum 22 and / or the thoracic cavity 32. The distal portion 25 of the lead 16 may be parallel to the sternum 22 or offset to the left or right from the sternum 22. In other examples, the distal portion 25 of the lead 16 may be angled to the left or right away from the sternum 22, such that the distal portion 25 does not extend parallel to the sternum 22.

[0051] In another example, IMD 14 can be subcutaneously implanted outside the pleural cavity 32 at an anterior midline location. Lead 16 can be subcutaneously inserted into a location adjacent to a portion of the latissimus dorsi muscle of the patient 12, laterally and posteriorly into the pocket of IMD 14 towards the patient's back to a position opposite the heart 26, such that the heart 26 is typically positioned between IMD 14 and electrodes 24A, 24B, 28A, 28B, and 30. The techniques disclosed herein for generating low-pressure pacing pulses for pacing the heart using cardiovascular external electrodes are not limited to specific subcutaneous, submuscular, suprasternal, substernal, or intrathoracic / external locations for cardiovascular external electrodes.

[0052] Refer again Figure 1A Lead 16 includes an elongated lead body 18 that carries electrodes 24A, 24B, 28A, 28B, and 30 and insulates elongated electrical conductors (not shown) extending from the corresponding electrodes 24A, 24B, 28A, 28B, and 30 through the lead body 18 to a proximal connector (not shown), which is coupled at a proximal end 27 of the lead to a connector assembly 17 of the IMD 14. Lead body 18 may be formed of a non-conductive material, such as silicone, polyurethane, fluoropolymers, mixtures thereof, or other suitable materials, and is shaped to form one or more lumens in which the one or more conductors extend. The conductors are electrically coupled to IMD circuitry (such as a therapeutic delivery module and / or a sensing module) via connections in the IMD connector assembly 17, which includes a connector bore for receiving the proximal connector of lead 16 and an associated electrical feedthrough through the IMD housing 15. The electrical conductors transmit electrical stimulation therapy from the treatment delivery module within the IMD 14 to one or more of electrodes 24A, 24B, 28A, 28B and / or 30, and transmit cardiac electrical signals from one or more of electrodes 24A, 24B, 28A, 28B and / or 30 to the sensing module within the IMD 14.

[0053] Housing 15 forms a hermetically sealed enclosure protecting the internal electronic components of IMD 14. As described above, housing 15 can act as a “metal-cased electrode” because the conductive housing or a portion thereof can be electrically coupled to the internal circuitry to serve as an unrelated electrode or grounding electrode during ECG sensing or during treatment delivery. As will be described in further detail herein, housing 15 can enclose one or more processors, memory devices, transmitters, receivers, sensors, sensing circuitry, treatment circuitry, and other suitable components.

[0054] Figure 1A The example system 10 described herein is illustrative in nature and should not be considered as limiting the technology described herein. The technology disclosed herein can be implemented in many ICD or pacemaker and electrode configurations, including those for delivering cardiac pacing pulses. IMD system 10 is referred to as an extravascular IMD system because lead 16 is a non-venous lead located outside the blood vessels, heart 26, and pericardium 38. The technology disclosed herein can also be used by leadless devices implanted substernally, intrathoracically, or extrathoracically and having electrodes carried by a housing and / or, in some cases, by conductors extending from the housing. Another example of an IMD that can implement the currently disclosed technology is generally disclosed in U.S. Patent No. 8,758,365 (Bonner et al.).

[0055] External device 40 is shown to telemetry communicate with IMD 14 via communication link 42. External device 40 may include a processor, display, user interface, telemetry unit, and other components for communicating with IMD 14, for transmitting and receiving data via communication link 42. Communication link 42 may be established between IMD 14 and external device 40 using a radio frequency (RF) link (such as BLUETOOTH®, Wi-Fi, or Medical Implantable Communication Service (MICS) or other RF or communication frequency bandwidth).

[0056] External device 40 can be implemented as a programmer for use in hospitals, clinics, or doctors' offices to retrieve data from IMD 14 and program the operating parameters and algorithms in IMD 14 for controlling IMD functions. External device 40 can be used to program the heart rate monitoring parameters and treatment control parameters used by IMD 14. Data stored or acquired by IMD 14 (including physiological signals or associated data derived therefrom, device diagnostic results, and the history of detected rhythmic events and delivered treatments) can be retrieved from IMD 14 by external device 40 upon query command. External device 40 can alternatively be implemented as a home monitor or a handheld device.

[0057] Figure 2AThis is a conceptual diagram of the distal portion 25' of another example of an implantable electrical lead 16 with an alternative electrode arrangement. In this example, the distal portion 25' includes two pacing / sensing electrodes 28A and 28B and two defibrillation electrodes 24A and 24B, along with corresponding conductors, to provide the combination as described above. Figure 1A The described electrical stimulation and sensing functions. However, in this example, electrode 28B is proximal to the proximal defibrillator electrode 24B, and electrode 28A is distal to the proximal defibrillator electrode 24B, such that pacing / sensing electrodes 28A and 28B are spaced apart by defibrillator electrode 24B. In a further example, in addition to electrodes 28A and 28B, lead 16 may also include a third pacing / sensing electrode located distal to defibrillator electrode 24A. IMD 14 can use any electrode vector to deliver cardiac pacing pulses and / or sensing electrical signals, said electrode vector including defibrillator electrodes 24A and / or 24B (alone or together), and / or electrodes 28A and / or 28B, and / or the housing 15 of IMD 14.

[0058] The spacing and position of pacing / sensing electrodes 28A and 28B can be selected to provide a pacing vector enabling efficient pacing of the heart 26. The lengths and spacing of electrodes 24A, 24B, 28A, and 28B can correspond to any of the examples provided in the above-incorporated references. For example, the lead 16 from distal to proximal electrode (e.g., Figure 2A The distal portion 25' of the proximal side of electrode 28B in the example can be less than or equal to 15 cm, and can be less than or equal to 13 cm, and can even be less than or equal to 10 cm. It is conceivable that one or more pacing / sensing electrodes may be located distal to the distal defibrillator 24A; one or more pacing / sensing electrodes may be located between defibrillator electrodes 24A and 24B; and / or one or more pacing / sensing electrodes may be located proximal to the proximal defibrillator 24B. Having multiple electrodes at different locations along the lead body 18 enables selection from a variety of inter-electrode spacings, allowing selection of pacing electrode pairs (or combinations) with inter-electrode spacings that result in maximum pacing efficiency.

[0059] Figure 2B It demonstrates something similar to Figure 2AA conceptual diagram of the distal portion 25'' of another example of a cardiovascular external lead 16 with electrode arrangement, but having a non-linear or curved distal portion 25'' of the lead body 18'. The lead body 18' can be pre-formed to have a normal curve, bend, meander, wave-like, or serrated shape along the distal portion 25''. In this example, defibrillation electrodes 24A' and 24B' are carried along the pre-formed curved portion of the lead body 18'. A pacing / sensing electrode 28A' is carried between defibrillation electrodes 24A' and 24B'. A pacing / sensing electrode 28B' is carried proximally to the proximal end of the proximal defibrillation electrode 24B'.

[0060] In one example, lead 18' can be formed as a curved distal portion 25'' comprising two "C"-shaped curves, which together may resemble the Greek letter epsilon "ε". Defibrillation electrodes 24A' and 24B' are each carried by these two corresponding C-shaped portions of the distal portion 25'' and extend or bend in the same direction. In the example shown, pacing / sensing electrode 28A' is proximal to the C-shaped portion of carrying electrode 24A', and pacing / sensing electrode 28B' is proximal to the C-shaped portion of carrying electrode 24B'. Pacing / sensing electrodes 24A' and 24B' are generally aligned with the central axis 31 of the straight proximal portion of lead 18', such that the midpoints of defibrillation electrodes 24A' and 24B' are laterally offset from electrodes 28A' and 28B'. Defibrillation electrodes 24A' and 24B' are positioned along the distal portion 25'' of the lead body, with corresponding C-shaped portions extending laterally away from the central axis 31 and electrodes 28A' and 28B' in the same direction. Other examples of cardiovascular external leads are generally disclosed in pending U.S. Patent Publication No. 2016 / 0158567 (Marshall et al.), including one or more defibrillation electrodes and one or more pacing and sensing electrodes carried by a curved, meandering, wavy, or serrated distal portion of the lead body, which can be implemented using the pacing techniques described herein.

[0061] Figure 3 This is a schematic diagram based on an example IMD 14. It is enclosed in housing 15 (in...). Figure 5 The electronic circuitry within the IMD 14 (schematically shown as a metal-cased electrode) includes software, firmware, and hardware that collaboratively monitor one or more ECG signals, determine when pacing therapy is needed, and deliver the prescribed pacing therapy as required. When the IMD 14 is configured as an ICD as shown herein, the software, firmware, and hardware are also configured to determine when CV / DF shock or cardiac pacing is needed and deliver the prescribed CV / DF shock or pacing therapy. The IMD 14 may be coupled to carrier cardiovascular external electrodes 24A, 24B, 28A, and 28B, and electrode 30 in some examples (…). Figure 3Leads (such as those not shown in the image) Figure 1A , Figure 1B , Figure 1C , Figure 2A and Figure 2B Lead 16 is shown in any of the examples for use in delivering pacing therapy, CV / DF shock therapy and sensing cardiac electrical signals.

[0062] The IMD 14 includes a control module 80, a memory 82, a treatment delivery module 84, an inductive module 86, and a telemetry module 88, and may include an impedance measurement module 90 and an optional sensor module 92. A power supply 98 provides power to the circuitry of the IMD 14 (including each of modules 80, 82, 84, 86, 88, 90, and 92) when needed. The power supply 98 may include one or more energy storage devices, such as one or more rechargeable or non-rechargeable batteries. The power supply 98 is coupled to low-voltage (LV) and high-voltage (HV) charging circuitry included in the treatment delivery module 84 for charging LV and HV capacitors, respectively, for generating therapeutic electrical stimulation pulses.

[0063] Figure 3 The functional blocks shown represent functions contained in IMD 14 and may include any discrete and / or integrated electronic circuit components that implement analog and / or digital circuitry capable of producing the functions attributed to IMD 14 herein. As used herein, the term "module" means an ASIC, electronic circuitry, a processor (shared, dedicated, or grouped) and memory executing one or more software or firmware programs, combinational logic circuitry, a state machine, or other suitable component that provides the described functions. The specific form of the software, hardware, and / or firmware used to implement the functions disclosed herein will be determined primarily by the specific system architecture used in the device and the specific detection and treatment delivery method employed by the IMD. Describing different features as modules is intended to highlight different functional aspects and does not necessarily imply that such modules must be implemented by separate hardware or software components. Rather, the functions associated with one or more modules may be performed by separate hardware or software components or integrated within a common hardware or software component. For example, pacing therapy control operations performed by control module 80 may be implemented in a processor executing instructions stored in memory 82. IMD 14 may include more than Figure 3 The diagram shows more or fewer of those modules. For example, impedance measurement module 90 and sensor module 92 may be optional and excluded in some instances. Given the disclosure herein, providing the software, hardware, and / or firmware to implement the described functionality within the context of any modern IMD system is within the capabilities of those skilled in the art.

[0064] Memory 82 may include any volatile, non-volatile, magnetic, or electrical non-transitory computer-readable storage medium, such as random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, or any other memory device. Furthermore, memory 82 may include a non-transitory computer-readable medium storing instructions that, when executed by one or more processing circuits, cause control module 80 or other IMD modules to perform various functions belonging to IMD 14 or those IMD modules. The non-transitory computer-readable medium storing instructions may include any of the media listed above.

[0065] The control module 80 communicates with the treatment delivery module 84 and the sensing module 86 to sense cardiac electrical activity, detect heart rhythm, and control the delivery of cardiac electrical stimulation therapy in response to sensed cardiac signals. The treatment delivery module 84 and the sensing module 86 are electrically coupled to electrodes 24A, 24B, 28A, 28B carried by leads 16 and a housing 15, which can serve as a common electrode or a ground electrode.

[0066] The sensing module 86 is selectively coupled to electrodes 28A and 28B and housing 15 to monitor the electrical activity of a patient's heart. The sensing module 86 may also be selectively coupled to electrodes 24A and 24B. The sensing module 86 is enabled to selectively monitor one or more sensing vectors selected from the available electrodes 24A, 24B, 28A, and 28B and housing 15. For example, the sensing module 86 may include switching circuitry for selecting which of electrodes 24A, 24B, 28A, and 28B and housing 15 are coupled to a sensing amplifier or other cardiac event detection circuitry included in the sensing module 86. The switching circuitry may include a switch array, switch matrix, multiplexer, or any other type of switching device suitable for selectively coupling a sensing amplifier to selected electrodes. The cardiac event detection circuitry within the sensing module 86 may include one or more sensing amplifiers, filters, rectifiers, threshold detectors, comparators, analog-to-digital converters (ADCs), or other analog-to-digital components.

[0067] In some examples, the electrical sensing module 86 includes multiple sensing channels for acquiring cardiac electrical signals from multiple sensing vectors selected from electrodes 24A, 24B, 28A, and 28B and housing 15. Each sensing channel can be configured to amplify, filter, and rectify the cardiac electrical signals received from selected electrodes coupled to the corresponding sensing channel to improve signal quality for sensing cardiac events (e.g., R waves and P waves).

[0068] For example, each sensing channel in sensing module 86 may include: an input or pre-filter and amplifier for receiving cardiac electrical signals from a corresponding sensing vector; an analog-to-digital converter; a post-amplifier and filter; and a rectifier for generating a digitized, rectified, and amplified cardiac electrical signal that is passed to a cardiac event detector included in sensing module 86 and / or to control module 80. The cardiac event detector may include a sensing amplifier, comparator, or other circuitry for comparing the rectified cardiac electrical signal with a cardiac event sensing threshold (such as an R-wave sensing threshold), which may be automatically adjusted. Sensing module 84 may generate a sensed cardiac event signal in response to a sensing threshold exceeding a limit. The cardiac event sensing threshold used by each sensing channel may be automatically adjusted according to sensing control parameters that may be stored in memory 82.

[0069] The sensing event signal generated by the sensing module 86 can be used by the control module 80 to detect shockable rhythms and / or to detect the need for pacing. For example, the control module 80 can respond to the sensing event signal by setting the pacing escape interval, which controls the timing of the pacing pulses delivered by the treatment delivery module 84. In addition to the sensed cardiac event signal, the sensing module 86 can also output a digitized ECG signal for use by the control module 80 in detecting / confirming tachycardia, for example, via morphological analysis or wavelet analysis.

[0070] The treatment delivery module 84 includes an LV treatment module 85 for delivering low-pressure pacing pulses using a cardiovascular extra-cardiac pacing electrode vector selected from electrodes 24A, 24B, 28A, and 28B and housing 15. The LV treatment module 85 includes a capacitor array selectively controlled by a control module 80 to provide a single composite pacing pulse comprising a series of two or more fused pulses delivered individually by discharging capacitors in the capacitor array sequentially within the width of the composite pacing pulse. Multiple capacitors can be selected sequentially, one at a time, to deliver individual pulses included within the composite pacing pulse. In other instances, multiple capacitors can be selected two at a time to deliver each individual pulse in the composite pacing pulse. In various examples, two or more combinations of one or more capacitors are selected in a timing series to deliver two or more sequentially fused pulses that together define the composite pacing pulse. As used herein, the term "fused pulse" refers to an electrical pulse that is sequentially delivered within the composite pacing pulse to generate cumulative pulse energy sufficient to induce pacing-induced myocardial depolarization and capture the heart. The pulse energy of each individual fusion pulse in a fusion pulse may not be sufficient to take over the heart, but the cumulative energy of the fusion pulses delivered within the time envelope of the combined pacing pulse width is sufficient to induce a single evoked response in the myocardium.

[0071] The LV capacitors included in the LV therapy module 85 are charged via an LV charging circuit to a voltage based on the programmed pacing pulse amplitude. The LV charging circuit may include a state machine for charging the LV capacitors to a multiple (e.g., four times the battery charge) of the battery voltage included in the power supply 98. At appropriate times, the LV therapy module 85 couples individual capacitors (or combinations of individual capacitors) of the capacitor array to the pacing electrode vector in a timing sequence. The capacitor combinations are sequentially discharged to deliver a composite pacing pulse defined by sequentially delivered individual pulses. The individually delivered pulses are temporally fused such that the energy of the individual pulses is accumulated to produce a total pulse energy greater than the pacing capture threshold of the patient's heart, even though each individual pulse may have a pulse energy less than the pacing capture threshold. In some examples, the leading edge of an individual pulse delivered by a capacitor (or a combination of capacitors) occurs at or before the immediate preceding individual pulse reaches its termination edge (e.g., within inherent electronic timing constraints). In some cases, individual pulses can be spaced apart by non-zero time intervals within the width of a composite pacing pulse; however, the cumulative electrical energy of individual pulses within the width of a composite pulse is sufficient to sabotage the myocardium.

[0072] As described below, the LV treatment module 85 can be configured to sample the amplitude of the compound pacing pulse in real time over the width of the compound pacing pulse. When the amplitude of a single pulse reaches a threshold amplitude, the next capacitor (or combination of capacitors) in the capacitor sequence can be coupled to the pacing electrode vector. In this way, the amplitude of the compound pacing pulse is not allowed to fall below a predetermined minimum amplitude over the entire width of the compound pacing pulse.

[0073] Impedance measurement module 90 can be electrically coupled to available electrodes 24A, 24B, 28A, and 28B and housing 15 to perform impedance measurements on one or more candidate pacing electrode vectors. Control module 80 can control impedance measurement module 90 to perform impedance measurements for selecting a pacing electrode vector. For example, control module 80 can transmit a signal to impedance measurement module 90 to initiate an impedance measurement for a pacing electrode vector. Impedance measurement module 90 is configured to apply a drive current or excitation current across the pacing electrode vector and determine the resulting voltage. The voltage signal can be used directly as the impedance measurement result, or the impedance can be determined based on the applied current and the measured voltage. The impedance measurement result can be transmitted to control module 80 for selecting a pacing electrode vector for therapeutic delivery.

[0074] As described below, the impedance measurement results can be used by the control module 80 to select the number of individual pulses and / or the number of the series of capacitors to be discharged to generate a composite pacing pulse. The impedance of the selected pacing vector and the capacitance of a given capacitor or combination of capacitors in the capacitor array will determine the decay rate of the individual pulse. If the impedance is relatively low, the individual pulse has a relatively fast decay rate. The rapid decay of a single pulse requires the next pulse in a series of fusion pulses to occur earlier, and then the first pulse decays to below the minimum amplitude that would result in a loss of capture. If the impedance is low and the decay rate is fast compared to when the impedance is high and the pacing pulse decay rate is relatively slow, the next capacitor (or combination of capacitors) in the series may need to begin discharging relatively early. Therefore, the individual pulse width is longer when the impedance is relatively high, and may be relatively shorter when the impedance is relatively low.

[0075] To achieve the desired overall pulse width and maintain the composite pulse amplitude above the minimum amplitude for all or most of the composite pulse widths, individual pulse widths can be relatively short, and the number of pulses can be increased when the pacing vector impedance is low. When the pacing vector impedance is relatively high, fewer relatively long individual pulses can be delivered. Individual pulse widths can be reduced, and the number of individual pulses can be increased to achieve the desired composite pulse width where the pulse amplitude is maintained above the minimum amplitude threshold for each individual pulse width. The time interval from one leading edge of an individual pulse to the next leading edge, as well as the total number of pulses, will determine the overall composite pacing pulse width.

[0076] If the impedance is low, the decay time of the pulse can be prolonged by using a higher capacitance to deliver each individual pulse. The individual pulse width and number of pulses can remain the same, but the decay time is adjusted by selecting a capacitor or combination of capacitors with a higher capacitance value when the pacing vector impedance is low. Therefore, the impedance measurement results from the impedance measurement module 90 can be used by the control module 80 to determine the required number of individual pulses, the individual pulse width, and / or the capacitance used to generate each individual pulse in the composite pacing pulse, thereby generating a composite pacing pulse with an amplitude profile over the duration of the pulse width that successfully captures and paces the heart.

[0077] In embodiments where the IMD 14 provides high-voltage therapy (such as cardioversion / defibrillation shock pulses), the therapy delivery module 84 may additionally include a high-voltage (HV) therapy module 83, which includes one or more high-voltage output capacitors. The HV therapy module 83 may be optional and omitted when the IMD 14 is provided for delivering pacing pulses but is not capable of delivering high-voltage therapy. When included, the IMD 14 may be configured to detect shockable rhythms, such as ventricular fibrillation or tachycardia. In response to the detection of a shockable rhythm, the HV capacitor is charged to a pre-programmed voltage level via an HV charging circuit. The HV charging circuit may include a transformer and may be a processor-controlled charging circuit controlled by the control module 80. Upon detecting a feedback signal from the therapy delivery module 84 that the HV capacitor has reached the voltage required to deliver the programmed shock energy, the control module 80 applies a signal to trigger the discharge of the HV capacitor. In this way, the control module 80 controls the operation of the high-voltage treatment module 83 so as to deliver CV / DF shocks using the defibrillation electrodes 24 and the housing 15.

[0078] High-energy CV / DF shocks are typically at least 5 joules and more generally about 20 joules or higher. For comparison, the HV capacitors (when included) of the HV treatment module 83 can be charged to an effective voltage greater than 100 V for delivering cardioversion / defibrillation shocks. For example, in the HV treatment module 83, two or three HV capacitors can be connected in series to have an effective capacitance of 148 microfarads. These series capacitors can be charged to generate 750 V to 800 V for series combination to deliver shocks with pulse energies of 5 joules or more, and more typically 20 joules or more. In contrast, low-voltage pacing pulses delivered using cardiovascular external electrodes can be less than 0.1 joules. The low-voltage capacitors (multiple) charged for delivering low-voltage pacing pulses can have much smaller capacitances than the HV capacitors (e.g., 6 to 10 microfarads) and can be charged to a certain multiple of the battery charge of the power supply 90 using a state machine without the use of a transformer. If an LV capacitor or capacitor combination is charged to 8 V for a composite pacing pulse amplitude of 8 V and a total pulse width of 8 ms, the delivered energy is approximately 1 millijoule with a pacing vector impedance of 500 ohms. For a pacing load range between 400 ohms and 1000 ohms, a composite pacing pulse with an amplitude of 8 V and a pulse width of 8 ms delivered by the LV therapy module 85 can range from 0.5 millijoules to 1.3 millijoules. The maximum pulse amplitude obtainable from the LV therapy module 85 for delivering low-voltage composite pacing pulses can be 10 volts in some examples and higher in others, for example, not exceeding 40 volts or not exceeding 20 volts. For an endocardial pacing pulse with an amplitude of 2 V, a pulse width of 0.5 ms, and a pacing electrode vector impedance applied across 400 ohms to 1000 ohms, the energy of the pacing pulse delivered using an endocardial electrode or epicardial electrode can be on the order of microjoules, for example, 2 microjoules to 5 microjoules. For example, extravascular compound pacing pulses can be greater than 100 microjoules and less than 1 joule.

[0079] Sensor module 92 may include additional sensors for monitoring the patient to control treatment delivery. For example, sensor module 92 may include activity sensors, posture sensors, heart sound sensors, or other physiological sensors(s) for monitoring the patient and making treatment delivery decisions. In various examples, rate-responsive pacing may be provided based on patient activity signals. The rate of low-pressure pacing pulses delivered using external cardiovascular electrodes may be adjusted based on said activity signals. Decisions for delivering ATP or electrical shock therapy may also be based in part on physiological sensor signals, in addition to cardiac electrical signals. Thus, ATP pulses may be delivered as LV external cardiovascular pacing pulses in response to treatment delivery decisions made by control module 80 using physiological sensor signals from sensor module 92.

[0080] Control parameters used by the control module 80 can be programmed into the memory 82 via the telemetry module 88. For example, the composite pacing pulse width and pacing pulse amplitude can be programmable parameters. The control module 80 can use the programmed pacing pulse width and pacing pulse amplitude to control the selection, sequencing, and charging of the LV capacitor included in the LV treatment module 85. The telemetry module 88 includes features for communicating with external devices 40 via RF communication. Figure 1A and 1C (As shown in the diagram) The transceiver and antenna for communication. Under the control of the control module 80, the telemetry module 88 can receive downlink telemetry from the external device 40 and send uplink telemetry to the external device. The IMD 14 can use the telemetry module 88 to communicate with other implantable devices implanted in the patient's body.

[0081] Figure 4A It is for use with cardiovascular external electrodes that can be generated and delivered by IMD 14 (such as from...) Figures 1A to 2B The image depicts an example of a compound pacing pulse 50 for a paced heart 26, showing electrodes 24A, 24B, 28A, 28B and / or 30 and / or the electrode vector selected in the housing 15. In one example, the compound pacing pulse (such as those described below) Figure 4A Pulse 50 and Figure 4B The pulse 80 is delivered via one of electrodes 28A or 28B as the cathode and housing 15 as the return anode. In other examples, the composite pulse is delivered using one of electrodes 28A or 28B as the cathode and (in examples including defibrillation electrodes) a defibrillation electrode (such as one of defibrillation electrodes 24A or 24B) as the return anode. However, the techniques disclosed herein for delivering composite pacing pulses are not limited to use with a specific pacing electrode vector.

[0082] The composite pacing pulse 50 comprises four pulses 52a, 52b, 52c, and 52d, each delivered individually via an output capacitor through a cross-pacing electrode vector discharging at least two different holding capacitors (or two different combinations of holding capacitors). The first pulse 52a defines the leading edge 58a of the composite pulse 50. Each of pulses 52a through 52d has a peak voltage amplitude 66 according to a programmed pulse amplitude. The decay portions 56a, 56b, 56c, and 56d of each individual pulse decay according to the RC time constant of the charging circuit. Each individual pulse 52a through 52d may be truncated at a separate pulse width 62. The leading edges 58b, 58c, and 58d of the corresponding pulses 52b, 52c, and 52d coincide in time with the terminating edges 60a, 60b, and 60c of the pulses 52a, 52b, and 52c, respectively. The terminating edge 60d of the last pulse 52d defines the trailing edge of the composite pulse 50.

[0083] The composite pulse 50 has a time-varying pulse amplitude that reaches a peak voltage amplitude 66 at the leading edge 58a to 58d of each individual pulse having a decay period between leading edges 58a to 58d, and reaches a minimum pulse amplitude 68 just before the next leading edge. The individual pulse width 62 can be set to maintain the minimum pulse amplitude 68 of each individual pulse 52a to 52d above a minimum amplitude threshold to ensure that the total pulse energy delivered in the composite pulse 50 successfully captures and paces the heart 26. The individual pulse width 62 can be fixed, for example, up to 2 ms in some examples, so that when four fused consecutive pulses 52a to 52b are... Figure 4A The example shown has a total pulse width of up to 8 ms during delivery. The individual pulse width can be a maximum individual pulse width, which can be generated by the LV treatment module 85 when a single low-voltage capacitor (or combination of capacitors) included in the LV treatment module 85 is discharged to deliver a single pulse. This maximum available pulse width can be based on the effective capacitance of a single low-voltage holding capacitor (or combination of holding capacitors) and can be the maximum programmable pulse width for a single pulse.

[0084] For a given peak voltage amplitude 66 and individual pulse width 62, the number of individual pulses delivered in a fusion sequence can be selected based on the total pacing pulse width 64 required to capture the heart. The composite pacing pulse width 64 can be up to 8 ms (as shown), 10 ms, 12 ms, 16 ms, or even 20 ms or more. In some examples, the individual pulse width 62 is set to the maximum achievable individual pulse width without allowing the minimum pulse amplitude 68 to fall to a lower amplitude threshold. For example, the minimum pulse amplitude 68 can be prevented from reaching 0 V at termination edges 60a, 60b, 60c, and 60d and can be maintained above an amplitude threshold, which can be defined as a certain percentage of the programmed peak voltage amplitude 66, such as 25%, 50%, or other selected percentage of the programmed peak voltage amplitude 66.

[0085] In other examples, the pacing pulse amplitude can be monitored in real time during the delivery of the compound pacing pulse 50, and the next individual pulse can be initiated when the decay amplitude drops to an amplitude threshold. For example, the amplitude of the decay portion 56a can be sampled, and the next pulse 52b can be initiated when a minimum amplitude 68 is reached. When the next pulse 52b is initiated, the first pulse 52a is truncated such that the termination edge 60a of pulse 52a and the leading edge 58b of the second pulse 52b occur simultaneously or nearly simultaneously within the limits of the electronic circuitry. It should be recognized that in some examples, the limitations within the electronic circuitry may result in non-zero time gaps between the individual pulses 52a to 52d. However, the energy delivered by each individual pulse 52a to 52d is temporally fused sufficiently close to the preceding and / or following individual pulse so that the energy of the individual pulses accumulates to achieve the dose response necessary to achieve capture of the patient's heart. Each individual pulse 52a to 52d may have pulse energy below the capture threshold of the heart. By delivering individual pulses 52a to 52b within a time window defined by the total pulse width 64, the total energy of the delivered composite pacing pulses is greater than the cardiac pacing capture threshold. Thus, the composite pulse captures the heart even when individual pulses 52a to 52d, delivered alone or at larger temporal intervals, might not be sufficient to capture and pace the heart. In some examples, the pacing capture threshold test can be performed using methods generally disclosed in U.S. Patent Application No. 62 / 262,499 (Attorney-in-charge No.: C00012104.USP1) and the corresponding U.S. Patent Application No.: C00012104.USU2, filed on the same day.

[0086] Each individual pulse 52a to 52d can be delivered across a selected pacing electrode vector by sequentially coupling different capacitor elements across the pacing electrode vector having the same polarity (positive in the example shown). Each of the different capacitor elements is pre-charged to the peak voltage amplitude 66 before being coupled across the pacing electrode vector. In some examples, the same capacitor or combination of capacitors may not be used to deliver two consecutive individual pulses (e.g., 52a and 52b) because charging the capacitor (or combination of capacitors) to the peak voltage amplitude 66 occurs before initiating each of the corresponding individual pulses 52a to 52d. The same capacitor or combination of capacitors may be used to deliver two non-consecutive individual pulses, such as 52a and 52d, by recharging the same capacitor or combination of capacitors to the peak voltage amplitude 66 during one or more of the intermediate individual pulses 52b and 52c.

[0087] All individual pulses 52a to 52d in Figure 4A The peak voltage amplitude 66 is shown as having the same peak voltage amplitude. This peak voltage amplitude can be the maximum voltage amplitude obtainable from the LV treatment module 85, or the maximum voltage amplitude acceptable to the patient. The total pulse energy of the composite pacing pulse 50 is controlled by setting the number of individual pulses and the individual pulse width of pulses 52a to 52d. However, it is conceivable that a capacitor (or capacitor combination) discharged to deliver one of the individual pulses 52a to 52d can be charged to a different voltage than another capacitor (or capacitor combination) used to deliver a different pulse from those in individual pulses 52a to 52d. Therefore, in some instances, individual pulses 52a to 52d can have different peak voltage amplitudes. However, individual pulses 52a to 52d are generated by disconnecting the first discharge capacitor (or capacitor combination) and connecting the next capacitor (or capacitor combination) charged to the desired peak voltage amplitude of the next individual pulse. The first individual pulse is thus terminated by stopping the discharge of the first capacitor(s), and the next individual pulse is initiated by initiating the discharge of the next capacitor(s).

[0088] The pacing pulse 50 is followed by a recharge pulse 70, which comprises low-amplitude pulses of opposite polarity for each of the individual pulses 52a to 52d. If the output capacitor of the LV therapy module 85 has already been charged during the delivery of the pacing pulse 50, the recharge pulse 70 allows the output capacitor to be passively discharged to promote charge neutralization. The recharge pulse 70 can reduce polarization artifacts at the pacing electrodes.

[0089] exist Figure 4AIn this example, the individual pulses 52a to 52d are temporally merged but do not overlap because the leading and ending edges of the individual pulses are simultaneous or nearly simultaneous within the limits of the electronic device. In other examples, the several individual pulses may overlap. Figure 4B This is a depiction of a compound pacing pulse 80 having a leading edge 88a and a terminating edge 90c, according to another example. Pulse 80 comprises three overlapping pulses 82a, 82b, and 82c. The leading edges 88b and 88c of the second pulse 82b and the third pulse 82c occur before the terminating edges 90a and 90b of the corresponding preceding pulses 82a and 82b, respectively. In this case, the decay portions 86a, 86b, and 86c of the individual pulses 82a, 82b, and 82c may have different decay rates due to the overlap of pulses 82a and 82b and the overlap of pulses 82b and 82c. Electronic circuitry (such as one or more diodes) can be used to prevent charge distribution between capacitors when a single pulse 82b or 82c begins before the truncation of the preceding pulse 82a or 82b, respectively.

[0090] Figure 5 This is a schematic diagram of a pacing control module 102 included in a control module 80 and an LV therapy module 85 included in a therapy delivery module 84. The LV therapy module 85 includes a capacitor selection and control module 104 and a capacitor array 110. The capacitor array 110 includes a plurality of holding capacitors 115a to 115n (labeled C1 to Cn, collectively referred to as 115) arranged in parallel in this example. Each capacitor C1 to Cn is selectable via a corresponding switch among parallel switches 116a, 116b, 116c to 116n (collectively referred to as 116, labeled S1 to Sn). Switch 116 is controlled by the capacitor selection and control module 104 to selectively control which capacitors of C1 to Cn 115 are coupled to the pacing pulse output signal line 130 via switch 112 for pacing pulse delivery across the output capacitor 122. Although output capacitor 122 is represented as a single output capacitor element, it should be understood that output capacitor 122 may represent multiple output capacitors, one of which may be connected in series with each holding capacitor 115a to 115n, such that each holding capacitor in array 110 can be discharged across the corresponding output capacitor to deliver each individual pulse in a timing sequence. In this case, each output capacitor may be coupled to the corresponding holding capacitor 115a to 115n via a corresponding switch, which, when closed, enables discharge across the corresponding output capacitor of one or more holding capacitors 115a to 115n selected by closing a corresponding switch in switch 116. Figure 13 The diagram shows the configuration of the LV therapy module 85, which includes multiple output capacitors.

[0091] If the output capacitor 122 is provided as a single capacitor as shown, the output capacitor may have an equivalent capacitance selected based on the sum of the capacitances of all parallel holding capacitors C1 to Cn of array 110, such that the output capacitor 122 is not charged on the first individual pulse, thereby preventing the delivery of subsequent pulses delivered by subsequently discharging one or more holding capacitors 115. For example, the output capacitor 122 may have a capacitance at least equal to the sum of capacitors C1-Cn115.

[0092] For a single pulse width, switch 116 can be enabled or closed one at a time to couple one corresponding capacitor from capacitor 115 to output signal line 130 in a controlled sequence for delivering fused individual pulses of the composite pacing pulse. In some examples, switch 116 can be enabled or closed in a combination that allows two or more of capacitors 115a to 115n to be simultaneously coupled to output signal line 130 for delivering individual pulses. When two or more of capacitors 115a to 115n are used in combination to deliver individual pulses of the composite pulse, the higher effective capacitance results in a longer RC time constant and slower pulse amplitude decay during the composite pacing pulse.

[0093] Although four capacitors are shown, capacitor array 110 may include more or fewer capacitors, depending on the requirements of a particular pacing application and the available volume of housing 15. In other examples, capacitor array 110 includes two or three capacitors. In yet another example, capacitor array 110 includes five or six capacitors. In one example, capacitors C1 to Cn 115 may be provided with capacitances from 6 microfarads to 10 microfarads and may have the same or different capacitances, but capacitances larger or smaller than this range can be used to provide the desired effective capacitance for delivering each individual pulse. Larger capacitors (or larger effective capacitance of a combination of capacitors) can make it possible to use longer individual pulse widths to generate longer overall composite pacing pulses or composite pacing pulses comprising fewer individual pulses. Capacitors C1 to Cn 115 are shown as parallel coupled. In other examples, some capacitors in array 110 may be coupled in series; for example, C1 and C2 may be coupled in series and in parallel with C3. The optional arrangement of parallel and / or series capacitors 115 provides control over the RC time constant of the discharge circuit and the effective capacitance of the discharge circuit, including the output capacitor 122, as well as the pacing electrode vector impedance, depending on the specific pacing application. Various configurations of individual parallel or series capacitors 115 can be selected via switching circuitry included in the capacitor array 110 to achieve the desired effective capacitance for delivering individual pulses of composite pacing pulses.

[0094] The pacing control module 102 provides control signals to the capacitor selection and control module 104 to control the timing, pulse amplitude, and pulse width of the composite pacing pulse. The pulse amplitude can be set by the pacing control module 102 according to a programmed pulse amplitude, and the pulse width can be controlled according to a programmed pulse width. The pacing control module 102 can determine the capacitor configuration based on the number of fused individual pulses required to achieve the overall pulse width of the composite pacing pulse.

[0095] The capacitor selection and control module 104 controls the LV charging circuit 114 to charge a selected number of capacitors C1 to Cn 115 for delivering composite pacing pulses. For example, three capacitors C1 to C3 can be selected one at a time to deliver a composite pulse including three fusion pulses; four capacitors C1 to C4 can be selected one at a time to deliver a composite pulse including four fusion pulses, and so on. The LV charging circuit 114 charges the selected capacitors to a voltage level according to the programmed pacing pulse amplitude to supply pacing pulse energy. Power supply 98 ( Figure 3 The LV charging circuit 114 can be supplied with regulated power. The LV charging circuit 114 can be controlled by a state machine to charge selected capacitors using a multiple (e.g., four times) of the battery voltage of the power supply 98. The LV charging circuit 114 can be controlled to charge selected capacitors simultaneously or sequentially as needed to deliver the series of fused individual pulses.

[0096] In response to a timing signal from the pacing control module 102, the capacitor selection and control module 104 sequentially couples selected capacitors (or combinations of capacitors) to the output signal line 130 one at a time via switch 112 so that the selected capacitors (or combinations of capacitors) are discharged sequentially across the output capacitor 122 coupled to the output signal line 130 and the pacing electrode vector. Each capacitor (or combination of capacitors) is discharged for a single pulse width, which is merged in an overlapping or non-overlapping manner with the next single pulse delivered by discharging the next capacitor (or combination of capacitors) in the sequence. For example, the capacitor selection and control module 104 may sequentially cause selected switches of switches 116a to 116n to sequentially couple selected capacitors of capacitors C1 to Cn 115 to the output signal line 130. The capacitor selection and control module 104 decouples the capacitor array 110 from the output signal line 130 by opening switch 112 when the programmed compound pacing pulse width fails (or when the last single pulse width fails).

[0097] In some examples, the LV therapy module 85 includes an analog-to-digital converter (ADC) 106 for sampling the pacing pulse output on signal line 130 and providing digital feedback signals to capacitor selection and control module 104 and / or pacing control module 102. During the pacing pulse, pacing control module 102 enables ADC 106 to sample the pacing pulse output signal on output signal line 130 at a desired sampling rate (e.g., every 2 microseconds) across the pacing pulse width. ADC 106 can be configured to sample the pacing pulse amplitude from the beginning of the pacing pulse when switch 112 is enabled until the end of the pacing pulse or a portion thereof when switch 112 is disabled.

[0098] The pacing control module 102 can monitor the sampled pacing pulse amplitude received from the ADC 106 during pacing pulse delivery by comparing sample points with an amplitude threshold or with a expected amplitude. The expected amplitude can be based on the predicted decay rate of a single pulse according to the known or estimated RC time constant of the discharge circuit. In one example, the sample points are compared with an amplitude threshold, which can be set as a certain percentage of the programmed pacing pulse amplitude, such as 50% of the programmed pacing pulse amplitude. If the pacing pulse amplitude drops below the amplitude threshold, the pacing control module 102 passes a timing signal to the capacitor selection and control module 104 to initiate the next single pulse in the fused pulse series by turning on the next capacitor (or combination of capacitors) in array 110 to begin discharging (e.g., by closing the associated switches from switches S1 to Sn), thereby maintaining the amplitude above the minimum amplitude threshold level throughout the composite pacing pulse width. The previous individual pulse can continue to predefine the individual pulse width, or it can be truncated when the next pulse begins by disabling the previously enabled capacitor(s) by opening the associated switches from switches S1 to Sn 116 when the next holding capacitor(s) is enabled to discharge the next individual pulse.

[0099] Figure 6 This is a schematic diagram of a pacing control module 102, included in a control module 80 and capable of accessing instructions stored in a memory 82, according to an example. The pacing control module 102 may include a microprocessor 140 configured to execute instructions stored in the memory 82 for selecting a series of capacitors or combinations of capacitors and setting the pulse amplitude and pulse width for delivering composite pacing pulses.

[0100] Microprocessor 140 provides capacitor configuration data to capacitor configuration module 146, which then transmits the capacitor configuration data to LV treatment module 85. Figure 3The capacitor selection and control module 104 is used to select capacitors (or combinations of capacitors) to be used to deliver each individual pulse. These capacitors can be passed to the capacitor selection and control module 104 one at a time (e.g., over a clock cycle) until all individual pulses have been delivered. In other examples, the capacitor configuration module 146 can pass capacitor configuration data for an entire series of individual pulses, and the capacitor selection and control module 104 can select the capacitor(s) for each individual pulse in a suitable sequence.

[0101] The timing control module 150 can be controlled by the microprocessor 140 to transmit timing signals to the capacitor selection and control module 104, thereby controlling the timing of the leading edge of the composite pulse, the leading edge of subsequent pulses, the truncation time of individual pulses, and the termination edge of the composite pulse. The individual pulse widths and the overall pulse width of the composite pacing pulse can be predetermined, for example, stored in memory 82. The microprocessor 140 can control the delivery of the series of fused individual pulses by transmitting capacitor selection and timing information for each individual pulse to the capacitor selection and control module 104 via the capacitor configuration module 146 and the timing control module 150.

[0102] The microprocessor 140 can also pass instructions to the ADC control module 148. The ADC control module 148 can be configured to control the ADC 106 (…). Figure 5 The sampling rate and sampling interval are enabled. Pulse amplitude sample points can be received from ADC 106 by data buffer 144 and passed to microprocessor 140. Microprocessor 140 can be configured to compare the sampled amplitude values ​​with an amplitude threshold. Based on this comparison, microprocessor 140 can determine when the next pulse in the individual pulse sequence is needed and pass a timing signal to timing control module 150. Timing control module 150 then passes the timing signal to capacitor selection and control module 104, for example, on the next clock signal. Capacitor selection and control module 104 responds to the timing signal by turning on the next capacitor(s) or capacitor combination(s) in the series of capacitors, which is arranged to start the next individual pulse in the series of fused pulses. For example, the next individual pulse in the series of fused pulses can start when the pulse amplitude drops to an amplitude threshold (below the expected or predicted amplitude based on a known or estimated RC time constant of the discharge circuit) or when a predetermined individual pulse width fails, whichever comes first.

[0103] Data buffer 144 can receive impedance data from impedance measurement module 90. Microprocessor 140 can retrieve the impedance measurement data to determine the individual pulse width for delivering the fusion pulse. The decay rate of the individual pulse will depend on the impedance of the selected pacing electrode vector and the effective capacitance of the single capacitor or capacitor combination used to deliver the individual pulse. The RC time constant (sometimes referred to as tau) can be determined using the measured pacing vector impedance and the capacitance of the single capacitor or capacitor combination used to deliver the individual pulse. Based on the RC time constant, the voltage amplitude of the individual pulse at the truncation point can be determined at different pulse widths. The individual pulse width can be set to a value that makes the predicted voltage amplitude at the termination edge of the individual pulse greater than an amplitude threshold.

[0104] The timing control module 150 receives pacing pulse timing data from the microprocessor 140, which may include the start time and / or pulse width of each individual pulse. The start time of the first pacing pulse and the pulse width of each individual pulse are transmitted to the capacitor selection and control module 104. The pulse width of the first pulse can be applied to all individual pulses in the composite pulse such that if the individual pulse width fails, the nth pulse is truncated and the (n+1)th pulse begins, and the individual pulse width timer is restarted. If the next pulse in the series of pulses begins before the previous pulse is truncated (as in...), the timing control module 150 receives pacing pulse timing data from the microprocessor 140, which may include the start time and / or pulse width of each individual pulse. Figure 4B In the fusion overlap mode shown, the timing of the leading edge for starting the next pulse is also passed from the timing control module 150 to the capacitor selection and control module 104. In other examples, different individual pulse widths can be used so that the timer control module passes an individual pulse width for each pulse in the series. The following is combined with... Figure 14 Composite pacing pulses with different individual fusion pulse widths are described.

[0105] Figure 7 This is a schematic diagram based on an example of a capacitor selection and control module 104 included in an LV therapy module 85. The capacitor selection and control module 104 includes a capacitor control 160, a capacitor selection latch 162, a pulse width timer 164, and a pacing pulse enable / disable gating 166. The capacitor control 160 is derived from the pacing control module 102 (… Figure 6 The capacitor configuration control module 146 receives a clock signal 154 and an input signal 156. The input signal 156 includes capacitor selection data indicating the capacitor(s)(s) to be selected for each individual pulse of the composite pacing pulse.

[0106] Capacitor control 160 latches capacitor configuration data to capacitor selection latch 162, which stores the configuration data until it is passed to capacitor array 110. Figure 5The capacitor selection latch 162 is configured to send separate signals to each of the corresponding switches S1 to Sn 116 according to configuration data, so as to selectively enable or disable each of the capacitors C1 to Cn 115 according to the needs of each individual pulse delivery. The capacitor selection latch 162 is controlled by capacitor control 160 to sequentially select individual capacitors or combinations of capacitors to deliver the series of fused pulses.

[0107] Pulse width sequencer 164 receives signal from timing control module 150 on signal line 158. Figure 6 The timing module 150 receives clock signal 154 and input. Pulse width timing module 164 transmits timing control signals to pulse enable / disable gating 166. For example, when the pacing effervescence interval expires, timing control module 150 signals pulse width timing module 164 to enable LV therapy module 85 to begin pacing pulses. Pulse enable / disable signal gating 166 transmits signals to switch 112 on signal line 168. Figure 5 The output signal initiates the pacing pulse. Switch 112 is controlled by gating 166 to couple a first selected capacitor or combination of capacitors to the pacing pulse output signal line 130 for the first individual pulse. Under the control of pulse enable / disable gating 166, switch 112 remains enabled or closed for composite pacing pulse widths. Pulse width timer 164 can be set to composite pulse widths such that pulse enable / disable gating 166 disables or opens switch 112 to decouple capacitor 110 from output signal line 130 when the composite pacing pulse width fails.

[0108] In some examples, capacitor control 160 and pulse width timer 164 receive capacitor and timing data from pacing control module 102 on signal lines 156 and 158 on a pulse-by-pulse basis. Pulse width timer 164 can enable switch 112 for the duration of the composite pacing pulse width. During the composite pacing pulse width, pulse width timer 164 can be set to control the timing of individual switches S1 to Sn 115 for capacitor selection and for control module 104 to enable / disable individual switches based on capacitor selection for each individual pulse. Pulse width timer 164 may include one or more individual pulse timers for controlling the termination time of individual pulses and the timing of the leading edge of the next pulse. When each individual pulse width fails, capacitor control 160 controls capacitor selection latch 162 to select the next capacitor or combination of capacitors to begin the next individual pulse based on data received on signal line 156. The capacitor control 160 can receive data on signal line 156 in a serial manner indicating the capacitor(s) for each individual pulse, and continuously select the capacitor via latch 162.

[0109] Alternatively, all capacitor selection data, representing the desired number of individual pulses and capacitor selections for delivering the entire composite pacing pulse, can be passed to capacitor control 160 via a single path. Capacitor control 160 sequentially controls latch 162 to iterate through the individual capacitor selections according to timing signals from timer 164 when each individual pulse width fails.

[0110] In some examples, the pacing control module 102 receives the sampled amplitude of the pacing pulse signal and compares the sampled amplitude with an amplitude threshold. For example, if the pacing pulse amplitude drops to the amplitude threshold before the start of the next individual pulse or before the composite pulse width fails, the next capacitor selection for the next individual pulse can be triggered.

[0111] When the composite pacing pulse width fails, the pulse width timer 164 transmits a pulse termination signal to the pulse enable / disable gate 166, which outputs a signal on the control signal line 168 to terminate the pacing pulse by decoupling the capacitor array 110 from the output signal line 130 through the disable switch 112.

[0112] Figure 8 This is a flowchart 200 of an example method for delivering extracardiac pacing pulses by an IMD 10. At box 202, the composite pacing pulse width is selected. The pacing pulse width can be selected based on a capture threshold test. For example, using a default pacing pulse amplitude or a pacing pulse amplitude selected below a level of patient discomfort, the minimum pacing pulse width required to capture (successfully pace) the heart can be determined. The pacing pulse width of the composite pacing pulse can be set to a safety interval longer than the capture pulse width threshold to reduce the likelihood of missed capture.

[0113] At box 204, a capacitor sequence for delivering the composite pulse is selected. In one example, the pacing pulse width set at box 202 is divided by a predetermined individual pulse width to determine the number of fusion individual pulses with equal pulse widths that meet or exceed the composite pacing pulse width. For example, if the pulse width capture threshold is 2.5 ms, the composite pacing pulse width can be set to 3 ms at box 202. The predetermined individual pulse width can be set to 1 ms, such that three fusion pulses are required to achieve a 3 ms composite pacing pulse width. The capacitor sequence selected at box 204 consists of three capacitors, such as C1, C2, and C3, that are to be enabled sequentially for discharge across the pacing vector (each for 1 ms).

[0114] In another example, if the composite pacing pulse width is set to 2 ms, the pacing control module 102 can select a capacitor sequence as a combination of C1 and C2 to deliver a first 1 ms individual pulse and as a combination of C3 and C4 to deliver a second 1 ms individual pulse. In yet another example, if the pacing pulse width is set to 7.5 ms, a sequence of C1-C2-C3-C4-C1 can be selected such that each individual capacitor is sequentially enabled one at a time to discharge for a 1.5 ms individual pulse width, and C1 can be recharged after the first individual pulse during the delivery of the second through fourth individual pulses to enable it to deliver a fifth individual pulse. The five sequential 1.5 ms pulses are fused in a non-overlapping manner so that a 7.5 ms pacing pulse is delivered.

[0115] In each example, the maximum composite pacing pulse width can be up to 10 ms or higher. The maximum individual pulse width can be set based on the capacitance of the single capacitor or combination of capacitors used. For example, for a given effective capacitance used to deliver a single pulse, the maximum individual pulse width can be 2 ms, 4 ms, or other predetermined values.

[0116] The capacitors 115 in array 110 can be selected once for each individual pulse of the composite pacing pulse, or selected once in combination of two or more capacitors for each individual pulse. Various sequences of capacitor(s) selected for each individual pulse delivery are conceivable. Moreover, the selected sequence can involve discharging, recharging, and discharging again to deliver more than one individual pulse during a single composite pacing pulse.

[0117] The capacitors selected for delivering composite pacing pulses are charged at block 206 by LV charging circuitry 114 under the control of capacitor selection and control module 104. All capacitors being used to deliver pacing pulses can be charged simultaneously to the programmed pacing pulse voltage amplitude. In other examples, the capacitors can be charged sequentially according to the order in which they will be discharged during pacing pulse delivery. When a capacitor or capacitor combination is used more than once during a composite pacing pulse, LV charging circuitry 114 recharges the capacitor (or capacitor combination) while another capacitor or capacitor combination is being discharged to deliver a separate pulse. LV charging circuitry 114 may include a capacitor charge pump or an amplifier for a charge source to enable rapid recharging of the holding capacitors included in capacitor array 110.

[0118] At block 208, the pacing control module 102 determines whether it is time to deliver a pacing pulse. This determination can be based on the expiration of a pacing interval. For example, and without intended limitations, the pacing interval can be a VV pacing escape interval, such as the lower limit rate interval for bradycardia pacing, a spare escape interval for pacing during cardiac arrest or post-shock pacing, or the ATP interval during ATP delivery. Alternatively, the pacing interval can be an interval for delivering an entrained pacing pulse for rapid arrhythmia sensing prior to T-shock delivery, or a 50 Hz burst interval for rapid arrhythmia sensing. The pacing control module 102 can wait for the pacing escape interval to expire at block 208, and upon its expiration, the timing control module 150 signals the capacitor selection and control module 104 to initiate a composite pacing pulse.

[0119] The capacitor selection and control module 104 can set a composite pulse width timer included in the pulse width timer 164 at block 210 and couple the capacitor array 110 to the pacing output signal line 130 (e.g., by enabling or disabling it). Figure 5 Switch 112). At box 212, capacitor selection and control module 104 selects and controls the capacitor according to capacitor configuration module 146 ( Figure 6 The received data sequentially activates the capacitor(s) selected for delivering each individual pulse. Each capacitor(s) or combination of capacitors in the series is activated by closing the individual pulse width of the corresponding switches(s) S1 to Sn 116, so as to discharge the selected capacitor(s) across the pacing electrode vector. A single capacitor(s) or combination of capacitors is selected as the capacitive element to be discharged for delivering a composite pacing pulse. The pacing control module 102 selects a sequence of capacitive elements from the capacitors in the capacitor array 110, and a corresponding individual pulse width for each capacitive element in the sequence, such that the sum of the individual pulse widths is equal to or greater than the selected composite pacing pulse width, which is equal to or greater than the pacing pulse width capture threshold of the pacing pulse voltage amplitude being used.

[0120] When the fusion pulse sequence is completed in the event of a composite pacing pulse width failure, the capacitor selection and control module 104 decouples the capacitor array 110 from the pacing output signal line 130 at block 214, and the composite pacing pulse is completed. The composite pacing pulse is delivered to induce a single depolarization of a cardiac chamber (e.g., a ventricular chamber), thereby causing a single mechanical contraction or pulsation of the cardiac chamber. The leading-edge pulse amplitude of each individual pulse and the composite pulse width are selected such that, by using the selected extravascular pacing electrode vector for pacing the heart, the cumulative delivered energy of the fusion individual pulses meets or exceeds the pacing capture threshold. Each individual pulse of the composite pulse may have a pulse energy below the capture threshold, but the combined individual pulse energy accumulates during the composite pulse width to reach the pacing capture threshold, thereby inducing an induced response.

[0121] Figure 9 This can be performed by IMD 14 to select the capacitor sequence (e.g., in...). Figure 8 The flowchart 250 shows the method at block 204. At block 252, the pacing control module 102 sets an amplitude threshold. The amplitude threshold can be at or above the minimum acceptable voltage of the decaying individual pulses included in the composite pacing pulse. The amplitude threshold can be set based on the programmed pacing pulse amplitude (e.g., 50% of the programmed pacing pulse amplitude). At block 254, the pacing control module 102 acquires the impedance measurement results of the pacing electrode vector. The control module 80 can control the impedance measurement module 90 to perform impedance measurement on the pacing electrode vector, or the pacing control module 102 can retrieve previous impedance measurement results stored in the memory 82.

[0122] At block 256, the pacing control module 102 selects a component capacitor. This component capacitor is the effective capacitance of a single capacitor or a combination of two or more capacitors in the capacitor array 110, which may be selected simultaneously in series and / or in parallel for delivering individual pulses of the composite pacing pulse. In some examples, the component capacitor selected at block 256 is the capacitance of a single holding capacitor 115a, 115b, 115c, or 115n in the capacitor array 110, or the effective capacitance of a single holding capacitor 115a through 115n and the corresponding output capacitor 122. In other examples, the component capacitor selected at block 256 depends on the impedance measurement results. If the pacing electrode vector impedance measurement results are relatively low, a higher component capacitor (e.g., two of the capacitors 115 in parallel) can be selected. If the pacing electrode vector impedance is relatively high, the pacing control module 102 can select the component capacitance of a single capacitor in the capacitors 115.

[0123] At block 258, the pacing control module 102 determines the RC time constant of the measured pacing electrode vector impedance and the selected element capacitance. Based on the RC time constant, the pacing control module 102 can predict the maximum possible individual pulse width, which can be delivered at the termination edge of the individual pulse, and then at the leading edge of the next pulse in the sequence, without the pulse amplitude falling below an amplitude threshold. For example, the maximum individual pulse width can be estimated based on the RC time constant as the expected time for the individual pulse to decay from the programmed pacing pulse amplitude at the pulse leading edge to the amplitude threshold. At block 260, for the series of individual pacing pulses, the maximum possible individual pulse width is determined for each element capacitance. The pacing control module 102 can set the actual individual pulse width of each individual pulse to the maximum possible individual pulse width or set it to a value less than the maximum possible individual pulse width at block 262.

[0124] At block 264, the pacing control module 102 determines the number of individual pulses required to achieve at least the composite pacing pulse width at the individual pulse width. For example, if the composite pacing pulse width is set to 4 ms based on the RC time constant and the individual pulse width is set to 1 ms at block 262, four fusion pulses are required. If the individual pulse width is set to 0.75 ms, the minimum number of pulses can be determined to be 6 pulses producing a total individual pulse duration of 4.5 ms (longer than the composite pacing pulse width). Figure 8 At box 214, capacitor array 110 can be decoupled from pacing output signal line 130 at 4.0 ms, thereby truncating the last individual pulse 0.25 ms after its leading edge. In other examples, after all individual pulses have been delivered within the full width of the individual pulse, capacitor array 110 can be decoupled from pacing output signal line 130 such that, in some cases, the composite pacing pulse width is exceeded by a portion of the individual pulse width.

[0125] At box 266, the capacitor elements of the capacitor sequence are selected based on the required number of individual pulses and the element capacitance. For illustration, if the minimum number of individual pulses is determined to be four based on the element capacitance of 10 microfarads (each capacitor C1 to Cn is a 10 microfarad capacitor), then the capacitor element sequence can be selected as C1-C2-C3-C4 at box 266. If only three capacitors are available, the capacitor sequence can be selected as C1-C2-C3-C1. If the element capacitance is selected to be twice the 10 microfarads used to deliver two fused pulses (for a composite pulse width of 8 ms, each 4 ms long), then at box 266, the capacitor elements in the sequence can be selected as C1 and C2 in parallel for the first element and as C3 and C4 in parallel for the second element. After selecting the capacitor elements of the capacitor sequence at box 266, it is possible to... Figure 8 At frame 206, the capacitors included in the sequence are charged to prepare for delivery of pacing pulses.

[0126] In some cases, a relatively large effective capacitance can be selected for the first individual pulse as a single larger capacitor or a combination of capacitors to ensure that the decay rate of the first pulse, based on feedback from ADC 106, is not faster than expected. Subsequent capacitor elements can be selected in real-time by pacing control module 102 based on the decay rate of the first pulse. If the decay rate is faster than expected, subsequent capacitor elements can be selected with an effective capacitance equal to or greater than that of the first capacitor element. If the first pulse does not decay faster than expected, subsequent individual pulses with a lower effective capacitance than the first pulse can be delivered. When one capacitor (e.g., C1 115a) has a larger capacitance than the other capacitors (C2 to Cn 115b to 115n), a larger capacitor element for the first individual pulse can be selected as a single holding capacitor. Alternatively, a larger capacitor element for the first individual pulse can be selected by selecting two or more individual holding capacitors in parallel (e.g., C1 115a and C2 115b in parallel).

[0127] Figure 10 This is flowchart 300 of a method for delivering compound pacing pulses, according to another example. At block 302, a capacitor sequence is selected. The capacitor sequence includes capacitor elements (a single capacitor or a combination of capacitors) selected sequentially for delivering individual pulse sequences. The capacitor sequence can be configured according to... Figure 8 and Figure 9 The described method can be selected or pre-defined.

[0128] At block 304, the capacitor array 110 is charged according to the programmed pacing pulse amplitude. At block 306, when pacing pulse delivery is required, the pacing control module 102 transmits timing signals to the capacitor selection and control module 104. At block 308, the capacitor selection and control module 104 sets a composite pulse width timer and couples the capacitor array 110 to the pacing output signal line 130 for the composite pacing pulse width.

[0129] At block 310, the first capacitor element in the capacitor sequence is enabled by closing the associated switches 116 to initiate a separate pulse, thereby allowing discharge of the first capacitor element across the pacing electrode vector. During the pulse, the pacing control module 102 may enable the ADC 106 to monitor the pulse amplitude at block 312. The pacing control module 102 receives the sampled voltage signal and compares it to an amplitude threshold at block 314. The pacing control module 102 may establish the amplitude threshold based on a programmed pulse amplitude (e.g., 50% or another percentage of the programmed pulse amplitude). If the pulse amplitude sampled at block 314 is less than the amplitude threshold, the next separate pulse begins at block 310.

[0130] If the pulse amplitude sampled at box 314 remains above the threshold and the individual pulse width timer expires at box 316, the next individual pulse is started at box 310 by selecting the next capacitor element in the sequence. As long as the pulse amplitude remains above the amplitude threshold, sampling and monitoring of the pulse amplitude can continue until the individual pulse width timer expires at box 316. If the individual pulse width timer expires at box 316 but the composite pulse width timer has not yet expired (box 318), the next individual pulse is started at box 310. If the composite pulse width timer has expired, the capacitor array 110 is decoupled from the output signal line 130 at box 320, and the delivery of the pacing pulse is complete. The process can return to box 304 to charge capacitor 115 and wait at box 306 for the next pacing pulse to be delivered.

[0131] In some examples, the expiration of the composite pulse width timer at any time during a single pulse (e.g., before the single pulse width timer expires) may cause the last pulse to be truncated before the single pulse width timer expires. In other examples, when the composite pulse width timer expires, it may be allowed to continue delivering single pulses until the single pulse width expires, which could be after the composite pulse width timer has expired. Figure 10In this method, the number of pulses and / or the width of individual pulses in a composite pulse may or may not be predetermined by the pacing control module 102. The pacing control module 102 may enable the capacitor selection and control module 104 to activate the next capacitor element in the sequence to begin the next individual pulse (n+1) when the sampled pulse amplitude of the current pulse (the nth pulse) drops to or below an amplitude threshold. In the absence of a predetermined number of fusion pulses for delivering the composite pacing pulse, individual pulses can continue to be delivered in this manner until the composite pulse width timer expires. In this case, the capacitor sequence selected at block 302 may include a sequence of capacitor elements that can be used to deliver up to a maximum number of individual pulses (e.g., 10 pulses), but not all capacitor elements in the sequence may be used to deliver pulses if the composite pulse width timer expires before reaching the maximum number of individual pulses.

[0132] Figure 11 This is a conceptual diagram of an IMD 14 coupled to a transvenous lead communicating with the right atrium (RA) 402, right ventricle (RV) 404, and left ventricle 406 of the heart 26. In some examples, the IMD 14 is a multifunctional device that can be programmably configured to operate as a multi-chamber pacemaker and defibrillator when coupled to transvenous leads 410, 420, and 430, or when coupled to one or more external cardiovascular leads (e.g., such as...). Figures 1A to 2B Lead 16 shown in the diagram is used as an external cardiovascular pacemaker and defibrillator. IMD 14 is... Figure 11 The IMD 14 is shown as being implanted in the right chest position; however, it will be appreciated that the IMD 14 can be implanted in the left chest position, particularly when the IMD 14 includes the cardioversion and defibrillation capabilities of using the housing 15 as an electrode.

[0133] exist Figure 1A In the example, IMD 14 may have a connector assembly 17 having a single connector bore for receiving a cardiovascular external lead 16. Figure 11In this configuration, the IMD 14 includes a connector assembly 170 having three connector bores for receiving proximal connectors of a right atrial (RA) lead 410, a right ventricular (RV) lead 420, and a coronary sinus (CS) lead 430, enabling the IMD 14 to deliver multi-chamber pacing to the heart 26. The RA lead 410 may carry a distal tip electrode 412 and a loop electrode 414 for acquiring an intracardiac electrocardiogram (EGM) signal and delivering RA pacing pulses. The RV lead 420 may carry pacing and sensing electrodes 422 and 424 for acquiring an RV EGM signal and delivering RV pacing pulses. The RV lead 420 may also carry an RV defibrillation electrode 426 and a superior vena cava (SVC) defibrillation electrode 428. Defibrillation electrodes 426 and 428 are shown as coil electrodes proximal to the distal pacing and sensing electrodes 422 and 424.

[0134] The CS lead 430 is shown as a quadrupole lead carrying four electrodes 432 that can be positioned along the myocardial vein 405. The CS lead 430 can advance through the coronary sinus into the myocardial vein 405 to position the electrodes 432 along the left ventricular lateral wall for obtaining a left ventricular EGM signal and delivering pacing pulses to the left ventricle. In other examples, one or more electrodes carried by the CS lead 430 can be positioned along the left atrium 408 for obtaining a left atrial EGM signal and / or pacing the left atrium 408.

[0135] The IMD 14 can be configured to provide dual-chamber or multi-chamber pacing therapy, including CRT, using electrodes 412, 414, 422, 424, and 432 with transvenous leads 410, 420, and 430. The IMD 14 can also be used with defibrillation electrodes 426 and 428 to detect and identify rapid cardiac arrhythmias and deliver CV / DF shocks as needed.

[0136] Figure 12A It is IMD 14 and Figure 2A or Figure 2B A conceptual diagram of the proximal portion of the cardiovascular external lead 16. The IMD connector assembly 170 includes three connector bores 440, 450, and 460. Connector bore 440 may include four electrical contacts 442, 444, 446, and 448, and may conform to the DF-4 industry standard. Electrical contacts 442, 444, 446, and 448 are electrically coupled to electronics enclosed within the housing 15 via an electrical feedthrough extending from the connector assembly 170 into the housing 15.

[0137] The cardiovascular external lead 16 includes a proximal lead connector 470, which may be a four-pole internal connector and conform to the DF-4 industry standard. The lead connector 470 is configured to mate with a connector bore 440 and may include pin terminals 472 and three annular terminals 474, 476, and 478, which are configured to mate with corresponding contacts 442, 444, 446, and 448 aligned along the connector bore 440, respectively. Contacts 442 and 444 may be coupled to the HV treatment module 83 and are therefore electrically coupled to at least one defibrillation electrode carried by the lead 16 (e.g., Figure 2A Electrodes 24A and 24B shown in the figure or Figure 2B The HV contacts of electrodes 24A' and 24B' are shown in the figure.

[0138] The annular terminals 476 and 478 of the lead connector 470 can be coupled to the pacing and sensing electrodes 28A and 28B (or 28A' and 28B') of the lead 16 via necessary conductors (not shown) extending through the lead body 18 (or 18'). The annular terminals 476 and 478 are configured to mate with corresponding contacts 446 and 448 of the connector bore 440, such that electrodes 28A and 28B (or 28A' and 28B') are electrically coupled to the LV therapy module 585 via terminals 476 and 478 and contacts 446 and 448. As combined below... Figure 13 As described, the LV therapy module 585 is programmably configured to operate for delivering a compound pacing pulse for extravascular pacing when the IMD 14 is coupled to an extravascular lead 16, or to deliver multichannel multichamber pacing when the IMD 14 is coupled to a set of transvenous leads (such as leads 410, 420, and 430). Although in Figure 12A Not shown, but it should be understood that additional connections may exist as needed at contacts 442, 444, 446, and 448 with other circuitry within housing 15 (such as inductance module 86 and impedance measurement module 90, both of which are located within the housing). Figure 3 (shown in the diagram) and used to couple all electrodes 24A, 24B, 28A and 28B to the LV treatment module 585 so that the pacing electrode vector can be selected from any combination of electrodes 24A, 24B, 28A and 28B (or 28A' and 28B') and / or housing 15.

[0139] When the IMD 14 is coupled to the cardiovascular lead 16, bores 450 and 460 may not be used. These two bores 450 and 460 can be sealed with plugs 480 and 482. As described below, the IMD 14 can be automatically configured to deliver low-voltage composite pacing pulses via contacts 442, 444, 446 and / or 448 by coupling the capacitor array 110 to contacts 442, 444, 446 and / or 448 in such a way that selected capacitors or combinations of capacitors are allowed to be sequentially coupled to 442, 444, 446 and / or 448 and discharged across a pacing vector selected from pacing electrodes 24A, 24B, 28A and 28B (or 28A' and 28B') and / or housing 15. In some examples, the electrical contacts 442 and 444 of the connector bore 440 can also be coupled to the LV therapy module 585 to allow selection of a defibrillator electrode or defibrillator segment carried by lead 16 within the pacing electrode vector for delivering extra-cardiovascular pacing pulses generated by the LV therapy module 585. For example, the pacing electrode vector can be selected to include pacing / sensing electrodes 28A or 28B (or 28A' or 28B') as pacing cathodes, and as... Figure 2A (or Figure 2B The defibrillator 24A or defibrillator 24B (or 24A' or 24B') shown in the diagram serve as the return anode electrode.

[0140] Figure 12B It is IMD 14 and Figure 11 A conceptual diagram of the proximal portion of each of the transvenous leads 410, 420, and 430, which carry... Figure 11 The corresponding electrodes 412, 414, 422, 424, 426, 428, and 430 are shown. In this example, the RV lead 420 includes an internal quad-pole lead connector 425 configured to mate with a connector bore 440, which may conform to the DF-4 industry standard. The RV lead connector 425 is similar to the cardiovascular external lead connector 470 described above, including a pin terminal 492 and three annular terminals 494, 496, and 498, which are configured to mate with corresponding contacts 442, 444, 446, and 448 of the connector bore 440, respectively.

[0141] Pin terminals 492 and ring terminals 494 are electrically coupled to RV defibrillator electrodes 426 and SVC defibrillator electrodes 428 via elongated electrical connectors (not shown) extending through lead wire 420. When RV lead connector 425 is properly sealed within connector bore 440, pin terminals 492 and ring terminals 494 are electrically coupled to HV treatment module 83 via contacts 442 and 444 to enable HV treatment, such as CV / DF shock, to be delivered via defibrillator electrodes 426 and / or 428. When RV lead connector 425 is properly sealed in connector bore 440, ring terminals 496 and 498 are coupled to LV treatment module 585, thereby electrically coupling RV pacing and sensing electrodes 422 and 424 (electrically coupled to terminals 496 and 498 via corresponding conductors extending through lead wire 420) to LV treatment module 585 via contacts 446 and 448.

[0142] The RA lead 410 includes a proximal connector 415 with terminals 416, which may conform to the IS-1 industry standard for mating with a connector bore 460. The connector bore 460 includes a pair of contacts that make electrical contact with the RA lead connector terminals 416 when the RA lead connector 415 is properly sealed within the connector bore 460, thereby providing an electrical connection between the RA electrodes 412 and 414 (which are electrically coupled to the terminals 416 via corresponding conductors extending through the lead 410) and the LV therapy module 585 for delivering RA pacing pulses.

[0143] CS lead 430 includes a proximal connector 435 (shown as an internal four-pole connector) with four connector terminals 436, which may conform to the IS-4 industry standard. When the CS lead connector 435 is properly sealed within the connector bore 450, the CS lead 430 ( Figure 11 Electrode 432 is electrically coupled to the LV therapeutic module 585 via an electrical connection between the CS lead connector terminal 436 and the corresponding contact of the connector bore 450. It should be understood that the contacts of connector bores 440, 450, and 460 are connected to, for example,... Figure 3 Additional connections between the inductive module 86 and the impedance measurement module 90, and other internal IMD circuits, may be provided as needed, but are not shown for clarity. Figure 12B As shown in the image.

[0144] Figure 13 When the IMD 14 is programmably configured as a multi-channel pacing device, it can be used with transvenous leads and electrodes (such as...). Figure 11 and Figure 12B (as shown in the image) used together, or configured as a cardiovascular external pacing device to be used with cardiovascular external leads and electrodes (such as... Figures 1A to 2B and Figure 12AA conceptual diagram of an LV therapy module 585 used together (as shown in the example). The capacitor array 610 of the LV therapy module 585 includes three pacing channels 602, 604, and 606, which can provide at least three separate pacing outputs when the IMD 14 is programmed to operate as a multi-channel, multi-chamber pacemaker. For example, when the IMD 14 is coupled to, as shown in the example, a conceptual diagram of an LV therapy module 585 used together. Figure 12B When the three transvenous leads 410, 420, and 430 are shown, the three pacing channels 602, 604, and 606 can be referred to as: left ventricular output channel 602 coupled to coronary sinus lead 430; right ventricular output channel 604 coupled to RV lead 420; and atrial output channel 606 coupled to RA lead 410. The three pacing channels 602, 604, and 606 are disconnected from each other by opening or disabling operation configuration switches 620a to 620d (collectively referred to as 620) and 630, such that each channel 602, 604, and 606 delivers pacing pulses to the corresponding cardiac chamber along separate signal pacing output lines 642, 646, and 648 for delivering multi-chamber intracardiac pacing pulses.

[0145] However, the IMD 14 can be programmed to operate as a single-channel external cardiovascular pacemaker. When programmed to operate as an external cardiovascular pacemaker, the three pacing channels 602, 604, and 606 are bundled together via closed-operation configuration switches 620a to 620d and 630, such that the signal pacing output line 646, when coupled to the IMD 14 via connector bore 440, is used to deliver external cardiovascular pacing pulses, for example, via... Figures 1A to 2B as well as Figure 12A The example shown is a cardiovascular external lead 16.

[0146] The capacitor array 610 includes an array of four holding capacitors 612, 614, 616, and 618, which can be coupled to three separate pacing channels 602, 604, and 606 when operation configuration switches 620 and 630 are turned on to enable multi-channel pacing. The control of the capacitor array 610 by the capacitor selection and control module 504 when the IMD 14 is programmed to operate as a multi-channel pacemaker will be described first.

[0147] Starting with pacing channel 602, holding capacitor 612 and backup holding capacitor 614 are charged or overcharged by LV charging circuit 514 during the time interval between left ventricular pacing pulses. Holding capacitor 612 can be selectively coupled to one of output capacitors 632a, 632b, 632c, and 632d via pacing enable switch 622 and a corresponding cathode selection switch 634a, 634b, 634c, and 634d. When lead 430 is via Figure 12B When the connector bore 450 shown is connected to the IMD 14, the output lines 642a, 642b, 642c and 642d are coupled to the corresponding electrodes in the electrodes 436 carried by the quadrupole coronary sinus leads 430.

[0148] Electrode selection switches 634a to 634d select which of the output capacitors 632a to 632d corresponding to the output signal lines 642a to 642d is coupled to the holding capacitor 612 for delivering pacing pulses. Another electrode of the electrodes 432 carried by the coronary sinus lead 430 can be selected as the return anode electrode and coupled to ground. The capacitor selection and control module 504 controls switch 622 and one of the electrode selection switches 634a to 634d to close for the duration during which left ventricular pacing pulses are delivered using the coronary sinus lead 430. When a backup ventricular pacing pulse is needed (e.g., due to loss of capture detection), the backup capacitor 614 is coupled via switch 624 to the selected output capacitor 632a, 632b, 632c, or 632d.

[0149] The pacing channel 604 can be used to deliver right ventricular pacing pulses using the RV lead 420. When the pacing enable switch 626 is closed by the capacitor selection and control module 504 according to the RV pacing pulse timing information, the holding capacitor 616 is coupled along the output line 646 to the output capacitor 636.

[0150] The pacing channel 606 can be used to deliver right atrial pacing pulses using the RA lead 410. When the pacing enable switch 628 is closed under the control of the capacitor selection and control module 504 according to the RA pacing pulse timing information received from the pacing control module 102, the holding capacitor 618 is discharged on the output line 648 through the output capacitor 638.

[0151] If the IMD 14 is programmed to operate as a cardiovascular pacemaker, the capacitor selection and control module 504 closes operation configuration switches 620 and 630 so that all holding capacitors 612, 614, 616, and 618 can be discharged to output line 646 at appropriate times via their corresponding output capacitors 632a to 632d, 636, and 638. Figure 12AAs shown in the example, when the IMD 14 is used to deliver pacing pulses using a cardiovascular external electrode carried by lead 470, connector bores 450 and 460 can be sealed by plugs 480 and 482 so that all pacing current is directed to output line 646.

[0152] When programmed to deliver extracardiac pacing pulses, pacing channel 602 can be used to deliver one or more individual pulses from a composite pacing pulse by selectively closing electrode selection switches 634a to 634d one at a time or simultaneously, so as to discharge one or a combination of holding capacitors 612 or 614 across corresponding output capacitors 632a to 632b on output line 646. If pacing channel 604 is selected to deliver a single pulse, switch 626 is closed to discharge capacitor 616 across output capacitor 636. Similarly, if pacing channel 606 is selected to deliver a single pulse from a composite pacing pulse, switch 628 is closed to discharge capacitor 618 across output capacitor 638 to output line 646.

[0153] In one example, holding capacitors 612, 614, 616, and 618 are 10 microfarad capacitors. Output capacitors 632a to 632d, 636, and 638 are each 7 microfarad capacitors. A holding capacitor 612, 614, 616, or 618, connected in series with a corresponding output capacitor 632a, 632b, 632c, 632d, 636, or 638, has an effective capacitance of 4 microfarads. The maximum available pulse width for this 4 microfarad effective capacitance can be set to 2 ms. Therefore, a single pulse can be delivered by discharging a holding capacitor 612, 614, 616, or 618 for up to 2 ms across one of the output capacitors 632, 636, or 638, respectively.

[0154] If the holding capacitor 612 and the backup holding capacitor 614 are selected in parallel by closing both pacing enable switches 622 and 624, and the holding capacitor and the backup holding capacitor are discharged across all parallel output capacitors 632a to 632d by closing all selection switches 634a to 634d, the effective capacitance is 12 microfarads in the example given above, where each of the holding capacitors 612 and 614 is 10 microfarads and each of the output capacitors 632a to 632d is 7 microfarads. With this effective capacitance, the maximum available individual pulse width can be set to 4 ms. The higher effective capacitance results in a longer RC time constant, so that the maximum possible individual pulse width is longer than when the holding capacitors 612, 614, 616, or 618 are selected one at a time using a corresponding output capacitor selected from capacitors 632, 636, or 638.

[0155] The capacitor selection and control module 504 selects which holding capacitors 612, 614, 616, and 618 are coupled to the output line 646 and in what combination and sequence by controlling corresponding switches 622, 624, 626, and 628 of the pacing channel 602 and electrode selection switches 634a to 634d. By sequentially enabling or closing the corresponding switches 622, 624, 626, and 628, pulse sequences can be delivered to generate composite pacing pulses by discharging the holding capacitors 612, 614, 616, and 618 one at a time (or one combination at a time) across the corresponding output capacitors 632a-d, 636, or 638. For example, sequentially discharging at least two of the holding capacitors 612, 614, 616, and 618 generates at least two composite pacing pulses fused from individual pulses.

[0156] Refer again Figure 12A For example, output line 646 can be electrically coupled to a pacing cathode electrode carried by lead 470 via ring terminal 476, and a return anode electrode carried by lead 470 can be coupled to ground via ring terminal 478 during extracardiac pacing. For example, the pacing cathode electrode and return anode electrode can respectively correspond to... Figure 1A Electrodes 28A and 28B shown, or any pacing electrode vector selected from electrodes 24A, 24B, 28A, 28B, 30 and housing 15. In other examples, see reference to Figure 2A (or 2B), one of electrodes 28A or 28B (or 28A' or 28B') can be selected as the pacing cathode, and one of defibrillation electrodes 24A or 24B (or 24A' or 24B') can be selected as the return anode.

[0157] In other examples, two pacing channels (e.g., channels 602 and 604) can be coupled together to output line 646 by enabling or disabling switch 620, enabling the delivery of sequential fusion pulses using holding capacitors 622, 624, and 626. Composite pacing pulses comprising at least two fused individual pulses can be delivered using the two channels 602 and 604 electrically coupled to output line 646. A third pacing channel 606 can be isolated from output line 646 by disabling or opening operation configuration switch 630. The third pacing channel (pacing channel 606 in this example) can remain separate and be used for other pacing purposes. Alternatively, channels 604 and 606 can be coupled to output line 646 by enabling or disabling operation configuration switch 630 and opening switch 620. In this case, pacing channel 602 remains separate and can be used for other pacing purposes, and channels 604 and 606 are bundled together for delivering composite pacing pulses.

[0158] Figure 14 This is a conceptual diagram of an example of a compound pacing pulse 650 that can be delivered by the LV therapy module 585 according to the techniques disclosed herein. In this example, individual pulses 652, 654, and 656 have different pulse widths. (See also...) Figure 13 Pulse 652 can be delivered by discharging the holding capacitor 616 across the output capacitor 636 on the output line 646 for a single pulse width 662. Pulse 654 can be delivered by discharging the holding capacitor 618 across the output capacitor 638 on the output line 646 for a single pulse width 664. In the illustrative example given above, when the effective capacitance of a holding capacitor 616 or 618 and the corresponding output capacitor 636 or 638 is 4 microfarads, the pulse width of each of pulses 652 and 654 can be 2 ms.

[0159] The final individual pulse 656 has a longer pulse width 666 than pulse widths 662 and 664, and can be delivered using a larger effective capacitance than that used to deliver pulses 652 and 654. Continuing with the illustrative example given above, if the parallel 10 microfarad holding capacitors 612 and 614 are used across all the parallel 7 microfarad output capacitors 632a to 632d to deliver pulse 656, the effective capacitance is 12 microfarads. Pulse width 666 can be set to 4 ms, longer than pulse widths 662 and 664. In this example, the composite pacing pulse width 670 is 8 ms.

[0160] The leading-edge pulse amplitude 660 of each pulse 652, 654, and 656 can be programmed to any range of pulse amplitudes, such as 1 V, 2 V, 4 V, 6 V, and 8 V. When the composite pulse width 670 is 8 ms, the pulse amplitude 660 can be selected to be greater than the pacing amplitude capture threshold. Due to limitations of the electronics, non-zero gaps may occur between each pulse 652, 654, and 656, but pulses 652, 654, and 656 are delivered close enough in time to provide cumulative delivered pulse energy within a composite pacing pulse width 670 greater than the pacing capture threshold, even when each pulse 652, 654, and 656 individually has a pulse energy less than the pacing capture threshold of the patient's heart.

[0161] In other examples, the longer pulse 656 may be delivered first with one or more shorter pulses 652 and 654, followed by the longer pulse 656, or it may be delivered between the shorter pulses 652 and 654. It will be appreciated that various combinations of the number of individual pulses, the width of individual pulses, and the sequence of individual pulses can be considered as methods for delivering composite pacing pulses using different effective capacitances of each individual pulse selected from a capacitor array comprising multiple hold and output capacitors, which may have different capacitance values ​​without departing from the scope of the extracardiac pacing techniques disclosed herein. Figure 14 The negative recharge pulse is not shown, but it should be understood that the composite pacing pulse 650 can be a biphasic composite pacing pulse, which has similar characteristics to... Figure 4A The negative portion of the composite pacing pulse 50 with the recharge pulse 70.

[0162] Figure 15 This is a flowchart 700 of a method for programmably configuring the IMD 14 to operate as a multi-channel, multi-chamber pacemaker with a transvenous lead, or as a single-channel pacemaker with a cardiovascular lead and a cardiovascular electrode. If the control module 80 is connected via the telemetry module 88 ( Figure 3 If a user command indicating that cardiovascular pacing should be enabled is received (as specified in box 702), then capacitor array 610 ( Figure 13 The control module 80 is configured to enable sequential pacing pulses on a single output line 646. At block 704, the control module 80 directs input to the capacitor selection and control module 504. Figure 13 Control signals are sent to enable or disable operation configuration switches 620 and 630, such that all holding capacitors 612, 614, 616, and 618 can be selectively coupled to output line 646 at appropriate times for discharging across the cardiovascular pacing electrode vector coupled to output line 646. At block 704, output lines 642a to 642d and 648 are bundled to output line 646 by keeping operation configuration switches 620a to 620d and 630 in the closed or enabled state.

[0163] If cardiovascular pacing is not enabled by user command at box 702, control module 80 controls capacitor selection and control module 504 to keep switches 620a to 620d and 630 in the open or disabled state, so that holding capacitors 612, 614, and 618 cannot be coupled to output line 646 during pacing. Electrode selection switches 634a to 634d selectively open or close to enable pacing channel 602 to deliver pacing pulses to electrodes(s) coupled to the corresponding output lines 642a to 642d. When operation configuration switches 620a to 620d and 630 are kept in the open state, pacing channel 606 is enabled to deliver pacing pulses on output line 648 using holding capacitor 618 and output capacitor 638. Pacing channel 604 is enabled to deliver pacing pulses on output line 646 using holding capacitor 616 and output capacitor 636.

[0164] In some examples, control module 80 automatically determines whether external cardiovascular pacing should be enabled at block 702 based on automatic detection of electrodes coupled to connector bores 440, 450, and 460, rather than based on user-input commands. Automatic detection of electrodes coupled to connector bores 440, 450, and 460 can be based on impedance measurements performed by impedance measurement module 90. When the impedance measurement result is high (indicating an open circuit across the connectors included in connector bores 450 and 460), external cardiovascular pacing configuration is enabled at block 704. When the impedance measurement result is relatively low (indicating a connection between the leads within connector bores 450 and 460 and the electrodes), multi-channel pacing configuration is enabled at block 706.

[0165] Operational configuration switches 620a to 620d and 630 can be once set to a closed or enabled state for single-channel external cardiovascular pacing, or set to an open or disabled state for multi-channel pacing and remain in this state for the duration of the IMD 14's operational lifespan. The operational configuration of the IMD 14 can be set at manufacturing time or by the user based on the intended use of the IMD 14. It can be assumed that the IMD 14 will be used only as a multi-channel pacemaker with transvenous leads or only as a single-channel external cardiovascular pacemaker for the duration of its service life. In other examples, if the patient's treatment needs change, the leads and electrodes coupled to the IMD 14 can be removed and replaced with different leads and electrodes, and the operational configuration of the IMD 14 can be programmably changed (manually or automatically) as needed. For example, single-channel external cardiovascular pacing may initially be sufficient for the patient, while at a later time, due to changes in the patient's disease state, multi-channel pacing may be required to provide multi-chamber pacing therapy. Figure 12A The single cardiovascular lead 470 shown can be used as follows Figure 12B The transvenous three-lead system shown in the diagram is used instead, and the IMD 14 can be programmed to change its operating configuration from a single-channel extravascular configuration to a multi-channel configuration for use with transvenous leads 410, 420 and 430.

[0166] Therefore, methods and apparatus for delivering pacing pulses using cardiovascular external electrodes have been given in the foregoing description with reference to specific embodiments. In other examples, the various methods described herein may include steps performed in a different order or combination than those shown and described herein. It should be understood that various modifications may be made to the referenced embodiments without departing from the scope of this disclosure and the foregoing claims.

Claims

1. An implantable medical device, comprising: The treatment module (85) has a capacitor array (110) including a plurality of capacitors and is configured to couple the capacitor array to a plurality of cardiovascular external electrodes to deliver a composite pacing pulse for cardiovascular external pacing to the patient’s heart. A pacing control module (102) is coupled to the treatment module and configured to control the treatment module to sequentially discharge at least a portion of the plurality of capacitors to generate a series of at least two individual pulses defining the composite pacing pulse.

2. An implantable medical device, comprising: A treatment module having a capacitor array including multiple capacitors and an output signal line, and the treatment module being configured to selectively couple the capacitor array to the output signal line to generate a composite pacing pulse for cardiovascular external pacing; Impedance measurement module; as well as A pacing control module, coupled to the treatment module and the impedance measurement module, is configured to control the treatment module to sequentially discharge at least a portion of the plurality of capacitors to generate a series of at least two individual pulses defining the composite pacing pulse. The pacing control module is further configured to: Select a capacitor element from the plurality of capacitors in the capacitor array; The impedance measurement results are obtained through the impedance measurement module. The RC time constant is determined based on the impedance measurement results and the effective capacitance of the selected capacitor element. Individual pulse widths should be set based at least on the determined RC time constant; and The treatment module is controlled to generate the at least two separate pulses using the selected capacitor element and having the separate pulse width.

3. The device as described in claim 2, wherein, The pacing control module is configured to control the treatment module: Discharging of a first portion of the plurality of capacitors begins to generate the leading edge of the first individual pulse of the at least two individual pulses, and discharging of the first portion of the plurality of capacitors ceases to generate the terminating edge of the first individual pulse of the at least two individual pulses. and On the termination edge of the first individual pulse in the individual pulse, discharge begins on a second portion of the plurality of capacitors that is different from the first portion to generate a second individual pulse in the at least two individual pulses.

4. The device as claimed in claim 2, wherein, The pacing control module is configured to control the treatment module to deliver each of the at least two individual pulses with a corresponding individual pulse energy below the pacing capture threshold.

5. The device as described in claim 2, wherein, The pacing control module is configured to control the treatment module to deliver the at least two individual pulses that define the composite pacing pulse with a cumulative pulse energy above a pacing capture threshold.

6. The device as claimed in claim 2, wherein, The pacing control module is configured to: Select the pacing pulse width for the composite pacing pulse; Select a sequence of capacitor elements from the plurality of capacitors in the capacitor array; A separate pulse width is set for each capacitive element in the sequence, such that the sum of the individual pulse widths is equal to or greater than the selected pacing pulse width; and Control the treatment module: Each of the capacitor elements in the sequence is charged to the pulse voltage amplitude; and The series of at least two individual pulses is generated by sequentially discharging each of the capacitor elements in the sequence for a time equal to the width of the corresponding individual pulse set for the corresponding capacitor element.

7. The device as claimed in claim 2, wherein: The plurality of capacitors in the capacitor array include at least two holding capacitors; and The pacing control module is configured to control the treatment module to discharge the at least two holding capacitors one at a time in sequence to generate the series of at least two individual pulses.

8. The device as claimed in claim 2, wherein: The capacitor array includes at least four holding capacitors; and The pacing control module is configured to control the treatment module to sequentially discharge the at least four holding capacitors to generate a series of at least three individual pulses.

9. The device as claimed in claim 2, wherein, The pacing control module is configured to control the treatment module to deliver a first individual pulse having a first pulse width among the at least two individual pulses, and a second individual pulse having a second pulse width greater than the first pulse width among the at least two individual pulses.

10. The device of claim 2, further comprising: Multiple operation configuration switches and multiple pacing output lines; The plurality of capacitors includes a plurality of holding capacitors and a plurality of output capacitors, each of the plurality of output capacitors being adjacent to a corresponding pacing output line among the plurality of pacing output lines; The pacing control module is configured to enable cardiovascular pacing by the treatment module using compound pacing pulses by controlling the plurality of operation configuration switches to couple at least a portion of the plurality of output capacitors to a single pacing output line among the plurality of pacing output lines.

11. The device as claimed in claim 10, characterized in that, The pacing control module is configured to disable cardiovascular pacing performed by the treatment module using compound pacing pulses and enable multichannel pacing by controlling the plurality of operation configuration switches to decouple at least a portion of the plurality of output capacitors from the individual pacing output line of the plurality of pacing output lines.

12. The device of claim 2, further comprising: A housing that encloses the treatment module and the pacing control module; A connector block, coupled to the housing, includes at least one connector bore configured to receive a connector for a cardiovascular lead to electrically couple an electrode in the cardiovascular lead to the treatment module.

13. The device as claimed in claim 2, wherein, The pacing control module is further configured to: control the treatment module to sequentially discharge a first portion of the plurality of capacitors for a first individual pulse width and discharge a second portion of the plurality of capacitors for a second individual pulse width, the first individual pulse width and the second individual pulse width defining a composite pacing pulse width of at least four milliseconds.

14. The device as claimed in claim 2, wherein, The pacing control module is further configured to control the treatment module: The first portion of the plurality of capacitors is charged to a certain voltage amplitude; The second portion of the plurality of capacitors is charged to the voltage amplitude; The first portion of the plurality of capacitors is discharged to deliver the first individual pulse of the at least two individual pulses having the voltage amplitude; and The second portion of the plurality of capacitors is discharged to deliver a second individual pulse, which follows the first individual pulse and has the voltage amplitude, of the at least two individual pulses.

15. An implantable medical device, comprising: A treatment module having a capacitor array including multiple capacitors and an output signal line, and the treatment module being configured to selectively couple the capacitor array to the output signal line to generate a composite pacing pulse for cardiovascular external pacing; A pacing control module, coupled to the treatment module, is configured to control the treatment module to sequentially discharge at least a portion of the plurality of capacitors to generate a series of at least two separate pulses defining the composite pacing pulse; as well as Impedance measurement module The pacing control module is further configured to: Select a capacitor element from the plurality of capacitors in the capacitor array; The impedance measurement results are obtained through the impedance measurement module. The RC time constant is determined based on the impedance measurement results and the effective capacitance of the selected capacitor element. Individual pulse widths should be set based at least on the determined RC time constant; and The number of individual pulses to be generated in the series of at least two individual pulses is determined based on the individual pulse width, such that the cumulative pulse width of the at least two individual pulses is greater than the pacing pulse width capture threshold.

16. An implantable medical device, comprising: A treatment module having a capacitor array including multiple capacitors and an output signal line, and the treatment module being configured to selectively couple the capacitor array to the output signal line to generate a composite pacing pulse for cardiovascular external pacing; A pacing control module, coupled to the treatment module, is configured to control the treatment module to sequentially discharge at least a portion of the plurality of capacitors to generate a series of at least two separate pulses defining the composite pacing pulse; as well as An analog-to-digital converter configured to sample the amplitude of the composite pacing pulse. The pacing control module is further configured to: The sampled amplitude of the composite pacing pulse is compared with an amplitude threshold, and In response to the sampled amplitude dropping to or below the amplitude threshold, the treatment module is controlled to start the next individual pulse in the series of at least two individual pulses.

17. An implantable medical device, comprising: A treatment module having a capacitor array including multiple capacitors and an output signal line, and the treatment module being configured to selectively couple the capacitor array to the output signal line to generate a composite pacing pulse for cardiovascular external pacing; A pacing control module, coupled to the treatment module, is configured to control the treatment module to sequentially discharge at least a portion of the plurality of capacitors to generate a series of at least two separate pulses defining the composite pacing pulse; as well as An analog-to-digital converter configured to sample the amplitude of the composite pacing pulse. The pacing control module is further configured to: Compare the sampled amplitude with the amplitude threshold; Based on the comparison, the capacitor element for generating the next individual pulse of the at least two individual pulses is selected in the following manner: a first capacitor element with a first effective capacitance is selected in response to the sampled amplitude being greater than the amplitude threshold, and a second capacitor element with a second effective capacitance greater than the first effective capacitance is selected in response to the sampled amplitude being less than the amplitude threshold.

18. An implantable medical device, comprising: A treatment module having a capacitor array including multiple capacitors and an output signal line, and the treatment module being configured to selectively couple the capacitor array to the output signal line to generate a composite pacing pulse for cardiovascular external pacing; as well as A pacing control module, coupled to the treatment module, is configured to control the treatment module to sequentially discharge at least a portion of the plurality of capacitors to generate a series of at least two separate pulses defining the composite pacing pulse. The pacing control module is further configured to: The pacing timing period is set by configuring one of the following: bradycardia pacing interval, cardiac arrest pacing interval, post-shock pacing interval, anti-tachycardia pacing interval, pre-tachycardia induction pacing interval, or tachycardia induction sudden onset interval; and When the pacing timeout period expires, the treatment module is controlled to deliver the composite pacing pulse.

19. A medical device comprising: The treatment module has a capacitor array including multiple capacitors and an output signal line, and is configured to generate a composite pacing pulse for cardiovascular extracorporeal pacing comprising a series of at least two individual pulses: By selectively coupling a first portion of the plurality of capacitors to the output signal line, a first pulse of the at least two individual pulses is generated, wherein the selectively coupled first portion of the plurality of capacitors has a first effective capacitance, and the first pulse of the at least two individual pulses has a first attenuation rate corresponding to the first effective capacitance. By selectively coupling a second portion of the plurality of capacitors to the output signal line, a second pulse is generated among the at least two individual pulses. The selectively coupled second portion of the plurality of capacitors has a second effective capacitance different from the first effective capacitance, and the second pulse among the at least two individual pulses has a second attenuation rate different from the first attenuation rate, the second attenuation rate corresponding to the second effective capacitance.

20. The device of claim 19, wherein the treatment module is further configured to: The first pulse is generated by coupling the first portion of the plurality of capacitors to the output signal line for a duration of the first pulse width. The second pulse is generated by coupling the second portion of the plurality of capacitors to the output signal line for a duration of a second pulse width, the second pulse width being different from the first pulse width.

21. The device of claim 20, wherein the treatment module is further configured to: The first pulse width is set such that the first pulse, attenuated at the first attenuation rate, is terminated at a first termination voltage amplitude, the first termination voltage amplitude being at least a threshold voltage amplitude; and The second pulse width is set such that the second pulse, which decays at the second decay rate, is terminated at a second termination voltage amplitude, which is at least a threshold voltage amplitude.

22. The device of claim 19, wherein the treatment module is further configured to generate a third pulse of the composite pacing pulse by coupling a third portion of the plurality of capacitors to the output signal line for a duration of a third pulse width, wherein the third portion of the plurality of capacitors has a third effective capacitance.

23. The device of claim 22, wherein the third effective capacitor is different from the second effective capacitor.

24. The device of claim 22, wherein the treatment module is further configured to generate the third pulse by coupling the third portion of the plurality of capacitors to the output signal line for a duration equal to the first pulse width.

25. The device of claim 22, wherein the treatment module is further configured to generate the composite pacing pulse in such a way that: The first pulse is generated by coupling the first portion of the plurality of capacitors to the output signal line for a duration equal to the first pulse width. The third pulse, which follows the composite pacing pulse continuously after the first pulse, is generated by coupling the third portion of the plurality of capacitors to the output signal line for a duration equal to the first pulse width. The second pulse is generated by coupling the second portion of the plurality of capacitors to the output signal line for a duration equal to the second pulse width, thereby continuously following the third pulse of the composite pacing pulse.

26. The device of claim 25, wherein the treatment module is further configured to: The second portion of the plurality of capacitors is selected to have a second effective capacitance, which is greater than the first effective capacitance and greater than the third effective capacitance; and The second pulse width is set to be greater than the first pulse width.

27. The device of claim 19, wherein the treatment module is further configured to: Generate a first pulse with a first pulse energy below the pacing capture threshold; Generate a second pulse with a second pulse energy lower than the pacing capture threshold; and The composite pacing pulse is generated, comprising at least the first pulse and the second pulse, the composite pacing pulse having a cumulative pulse energy comprising at least the energy of the first pulse and the energy of the second pulse, the cumulative pulse energy being at least the pacing capture threshold.

28. The apparatus of claim 19, further comprising: A switching circuit configured to sequentially couple the first portion of the plurality of capacitors and the second portion of the plurality of capacitors to the output signal line.

29. A non-transient computer-readable storage medium comprising a set of instructions, which, when executed by a control module of a medical device, cause the medical device to generate a composite pacing pulse for cardiovascular external pacing comprising a series of at least two separate pulses: The first pulse of the at least two individual pulses is generated by selectively coupling a first portion of a plurality of capacitors to an output signal line, wherein the selectively coupled first portion of the plurality of capacitors has a first effective capacitance, and the first pulse of the at least two individual pulses has a first attenuation rate corresponding to the first effective capacitance. By selectively coupling a second portion of the plurality of capacitors to the output signal line, a second pulse is generated among the at least two individual pulses. The selectively coupled second portion of the plurality of capacitors has a second effective capacitance different from the first effective capacitance, and the second pulse among the at least two individual pulses has a second attenuation rate different from the first attenuation rate, the second attenuation rate corresponding to the second effective capacitance.

Images