Medical device and method for generating modulated high frequency electrical stimulation pulses

Abstract

A medical device configured to deliver therapeutic electrical stimulation pulses by generating a frequency-modulated electrical stimulation pulse signal. The medical device includes a pulse signal source and a modulator. The pulse signal source generates an electrical stimulation pulse signal having a pulse width. The modulator can include a high frequency modulator configured to modulate a frequency of the pulse signal from a starting frequency down to a minimum frequency during the pulse width. In other examples, the modulator can include a low frequency offset generator to modulate the offset of the pulse signal between a minimum offset and a maximum offset.

Description

Technical Field

[0001] This disclosure generally relates to a medical device and method for generating modulated high-frequency electrical stimulation pulses. Background Technology

[0002] Medical devices can be configured to generate electrical pulses for delivering electrical stimulation therapy to treat pathological conditions or otherwise alter the state or activity of electrically excitable tissues such as a patient's heart, brain, spinal cord, nerves, skeletal muscle, or smooth muscle. Such devices can be implantable, wearable, or external devices that include or are electrically coupled to implantable and / or surface (skin) electrodes for delivering electrical stimulation pulses. In some cases, the electrical stimulation device can be configured to sense electrophysiological signals from the heart, brain, nerves, muscles, or other tissues and deliver electrical stimulation therapy based on the sensed electrophysiological signals.

[0003] For example, implantable or external pacemakers, cardioverter-defibrillators, cardiac monitors, and the like can sense electrical signals from a patient's heart. A pacemaker or cardioverter-defibrillator can deliver therapeutic electrical stimulation to the heart via electrodes carried by one or more medical electrical leads and / or electrodes on the housing of the medical device. The electrical stimulation may include, for example, a pacing pulse or a cardioverter-defibrillating shock. In some cases, the medical device can sense inherent or pacing-induced depolarization of the heart's electrical signals and control the delivery of stimulation signals to the heart based on the sensed electrical signals. Upon detection of an abnormal rhythm (e.g., bradycardia, tachycardia, or fibrillation), one or more appropriate electrical stimulation signals can be delivered to restore or maintain a more normal heart rhythm. For example, an implantable cardioverter defibrillator (ICD) can deliver a pacing pulse to a patient's heart when bradycardia or tachycardia is detected, or deliver a cardioverter defibrillator (CV / DF) shock to the heart when tachycardia or fibrillation is detected.

[0004] In some proposed or available ICD systems, an external lead can be attached to the ICD. In this case, the delivery of cardiac electrical stimulation pulses from electrodes outside the heart may result in electrical stimulation of other non-target excitable tissues, such as skeletal muscle or nerves. This external stimulation may be perceived by the patient and may cause annoyance, discomfort, or pain. In other medical devices or systems, electrodes may be located on the surface of the patient's body (e.g., on the patient's skin) to deliver electrical stimulation pulses to target nerves, organs, or muscles. Summary of the Invention

[0005] Generally speaking, this disclosure relates to a medical device and technique for generating therapeutic electrical stimulation pulses. A medical device operating according to the technique disclosed herein generates therapeutic electrical stimulation pulses by generating a high-frequency electrical stimulation pulse signal modulated over the pulse width of a pulse signal. Modulation may include modulation between a maximum and minimum frequency of oscillation of the pulse signal during the pulse width. In other instances, modulation may additionally or alternatively include modulating the bias of the pulse signal between a minimum and maximum offset. In some instances, the amplitude of the oscillation of the pulse signal is modulated upward to a maximum amplitude; in some instances, the maximum amplitude may temporally coincide with the minimum frequency of oscillation and / or the maximum bias offset.

[0006] In one example, this disclosure provides a medical device having a therapeutic delivery circuit including a signal source and a modulator. The signal source is configured to generate an electrical stimulation pulse signal having a pulse width. The modulator is configured to modulate the oscillation frequency of the electrical stimulation pulse signal between a minimum frequency and a maximum frequency during the pulse width, and / or modulate the bias of the electrical stimulation pulse signal between a minimum offset and a maximum offset during the pulse width. The modulator may be connected to an output circuit that may be connected to an electrical stimulation electrode for delivering the modulated electrical stimulation pulse signal.

[0007] In another example, this disclosure provides a method for delivering electrical stimulation therapy. The method includes generating an electrical stimulation pulse signal having a pulse width and modulating the oscillation frequency of the electrical stimulation pulse signal between a minimum frequency and a maximum frequency during the pulse width, and / or modulating the bias of the electrical stimulation pulse signal between a minimum offset and a maximum offset during the pulse width.

[0008] In another instance, this disclosure provides a non-transitory computer-readable medium storing a set of instructions that, when executed by control circuitry of a medical device, cause the medical device to deliver electrical stimulation therapy by: generating an electrical stimulation pulse signal having a pulse width and modulating the oscillation frequency of the electrical stimulation pulse signal between a minimum frequency and a maximum frequency during the pulse width, and / or modulating the bias of the electrical stimulation pulse signal between a minimum offset and a maximum offset during the pulse width.

[0009] The present invention is intended to provide an overview of the subject matter described herein. It is not intended to provide an exclusive or exhaustive explanation of the devices and methods described in detail in the following drawings and description. Further details of one or more examples are set forth in the following drawings and description. Attached Figure Description

[0010] Figure 1A and 1B This is a conceptual diagram of an extra-cardiac ICD system configured to sense cardiac electrical events and deliver cardiac electrical stimulation therapy, based on an example.

[0011] Figures 2A to 2C Therefore with Figures 1A to 1B The image shows a concept diagram of a patient with an extra-cardiac ICD system implanted, with different implantation configurations.

[0012] Figure 3 This is a conceptual diagram of a medical device configured to generate modulated electrical stimulation pulse signals, based on an example.

[0013] Figure 4 It is based on an instance. Figure 3 A description of the frequency-modulated pacing pulses generated by a medical device.

[0014] Figure 5 It is based on another instance. Figure 3 A description of the frequency-modulated pacing pulses generated by a medical device.

[0015] Figure 6 It is based on an instance. Figure 3 A conceptual diagram of the treatment delivery circuitry for a medical device.

[0016] Figure 7 It is based on the availability of an instance Figure 6 A depiction of the pacing pulse signal generated by the therapeutic delivery circuit.

[0017] Figure 8 It is based on another instance that is available. Figure 6 A depiction of the pacing pulse signal generated by the therapeutic delivery circuit.

[0018] Figure 9 This is a flowchart illustrating, based on some examples, a method for generating therapeutic electrical stimulation pulses by a medical device.

[0019] Figure 10 It is a diagram of a modulated high-frequency signal that can be generated by a medical device, based on another example.

[0020] Figure 11 This is a flowchart illustrating a method for controlling cardiac electrical stimulation therapy performed by a medical device, based on an example. Detailed Implementation

[0021] Generally, this disclosure describes techniques for generating and delivering therapeutic electrical stimulation pulses for treating conditions or diseases while minimizing patient discomfort or pain caused by extrinsic stimulation of non-target tissues by the therapeutic electrical stimulation pulses. The techniques disclosed herein can be implemented in various external, wearable, or implantable medical devices configured to deliver electrical stimulation pulses to body tissues using external surface (skin) electrodes, percutaneous electrodes, or implantable electrodes. In some applications, the therapeutic delivery electrode may not be in direct contact with the target body tissue stimulated by the therapeutic electrical stimulation pulses. The delivered current can pass through non-target tissues (including muscles and nerves), causing extrinsic stimulation of excitable tissues, which may result in pain, discomfort, or other sensations or perceptions of the stimulation. In other applications, the therapeutic delivery electrode may be in direct contact with the target body tissue, but the current of the stimulation pulse may diffuse into adjacent tissues, thereby causing extrinsic stimulation. The techniques disclosed herein provide the delivery of high-frequency electrical stimulation pulses to reduce pain or sensation caused by the delivery of the electrical stimulation pulses. High-frequency electrical stimulation pulses are modulated to cause depolarization of target tissues (e.g., heart, muscle, or nerves) by the delivered electrical stimulation pulses for therapeutic or medical purposes.

[0022] In the illustrative examples presented herein, cardiac medical devices, such as pacemakers or ICDs, are configured to deliver cardiac electrical stimulation pulses for capturing and depolarizing the myocardium. In various instances, the pacemaker or ICD may be connected to an extracardiac electrode or extravascular electrode. As used herein, the term “extravascular” refers to a location outside the blood vessels surrounding the patient’s heart, the heart, and the pericardium. For example, an implantable electrode carried by an extravascular lead may be positioned extrathoracically (outside the thoracic cavity and sternum) or intrathoracically (below the thoracic cavity or sternum, sometimes referred to as a substernal location), but may not necessarily be in close contact with myocardial tissue. In other instances, the medical device may be connected to a transvenous lead that positions the electrode within a blood vessel but may remain outside the heart in an “extracardiac” location. For example, as an example, a transvenous medical lead may advance along a venous pathway to position the electrode within the internal thoracic vein (ITV), intercostal vein, epigastric vein, or azygos vein, hemiazygos vein, or accessory hemiazygos vein. In any of these locations (e.g., extracardiac or extracardiac), the electric field around the electrodes generated by the electrical stimulation pulses delivered to the heart can encompass skeletal muscle and nerves.

[0023] When cardiac pacing pulses or other cardiac electrical stimulation pulses with the pulse amplitude and pulse width required to capture a patient's heart but without the modulation techniques disclosed herein are delivered, the patient may feel the pacing and / or experience pain, discomfort, or other sensations. Continuous cardiac pacing in patients requiring frequent or continuous pacing may not be well tolerated. Techniques for generating and delivering modulated pacing pulses to reduce pain and perception of the delivered cardiac pacing pulses enable extracardiac or extravascular pacemakers or ICD systems to deliver a wider range of cardiac pacing therapies for the treatment of various arrhythmias, including, for example, bradycardia, atrioventricular block, cardiac arrest, or ventricular tachycardia.

[0024] However, the electrical stimulation techniques disclosed herein can be implemented in a variety of medical devices, including implantable pacemakers, ICDs, neurostimulators, muscle stimulators, brain stimulators, spinal cord stimulators, or other devices configured to deliver therapeutic electrical stimulation pulses. In some instances, the electrodes delivering the stimulation pulses are carried by medical electrical leads extending remotely from the medical device. In other instances, the electrodes may be on the housing of the medical device. The techniques disclosed herein for delivering modulated electrical stimulation pulses are not limited to specific medical device lead or electrode configurations.

[0025] Figure 1A and 1B This is a conceptual diagram of an example medical device system 10 employing the electrical stimulation pulse modulation technique disclosed herein. System 10 includes an ICD 14, leads 16, and an external device 40. The ICD 14 is configured to sense cardiac electrical signals and deliver cardiac electrical stimulation therapy via electrodes carried by the leads 16. Figure 1A This is a front view of the ICD 14 and lead 16 implanted in patient 12. Figure 1B This is a side view of the ICD 14 and lead 16 implanted in patient 12. Figure 1A and 1B This is described in the context of an ICD14 capable of delivering a high-voltage cardiopulmonary bypass (CV / DF) shock and a relatively low-voltage cardiac pacing pulse in response to the detection of an arrhythmia. However, the techniques disclosed herein can be implemented in other cardiac devices configured to deliver cardiac pacing therapy only or to deliver only a high-voltage CV / DF shock.

[0026] The ICD 14 includes a hermetically sealed housing 15 forming a protective shell for the internal components of the ICD 14. The housing 15 of the ICD 14 may be formed of a conductive material, such as titanium or a titanium alloy. The housing 15 may function as an electrode (sometimes referred to as a "can" electrode). The housing 15 may be used as an active can electrode for delivering CV / DF shocks or other high-voltage pulses delivered using high-voltage therapeutic circuitry. In other instances, the housing 15 may be used to deliver monopolar, lower-voltage cardiac pacing pulses and / or for sensing cardiac electrical signals in conjunction with electrodes carried by leads 16. In other cases, the housing 15 of the ICD 14 may include multiple electrodes on an external portion of the housing. One or more external portions of the housing 15 that serve as one or more electrodes may be coated with a material such as titanium nitride, for example, to reduce post-stimulation polarization artifacts.

[0027] The ICD 14 includes a connector assembly 17 (also referred to as a connector block or head) that includes an electrical feedthrough through a housing 15 to provide electrical connection between a conductor extending within the lead body 18 of the lead 16 and electronic components contained within the housing 15 of the ICD 14. As will be described in more detail herein, the housing 15 may accommodate one or more processors, memories, transceivers, cardiac electrical signal sensing circuitry, therapeutic delivery circuitry, power supplies, and other components for sensing cardiac electrical signals, detecting heart rhythm, and controlling and delivering electrical stimulation pulses to treat abnormal heart rhythms.

[0028] The elongated lead body 18 has a proximal end 27 and a distal end 25, the proximal end 27 including a lead connector (not shown) configured to connect to an ICD connector assembly 17, and the distal end 25 including one or more electrodes. Figure 1A and 1B In the example illustrated, the distal portion 25 of the lead body 18 includes defibrillation electrodes 24 and 26, and pacing / sensing electrodes 28 and 30. In some cases, defibrillation electrodes 24 and 26 may form a defibrillation electrode together, as they can be configured to be activated simultaneously. Alternatively, defibrillation electrodes 24 and 26 may form a separate defibrillation electrode, in which case each of electrodes 24 and 26 can be activated independently.

[0029] Electrodes 24 and 26 (and in some instances, housing 15) are referred to herein as defibrillation electrodes because they are used, individually or collectively, to deliver high-voltage stimulation therapy (e.g., CV / DF shock). Electrodes 24 and 26 may be elongated coil electrodes and generally have a relatively large surface area for delivering high-voltage electrical stimulation pulses compared to pacing and sensing electrodes 28 and 30. However, in addition to or instead of high-voltage stimulation therapy, electrodes 24 and 26 and housing 15 may also be used to provide pacing functionality, sensing functionality, or both pacing and sensing functionality. In this sense, the use of the term "defibrillation electrode" herein should not be construed as limiting electrodes 24 and 26 to applications of high-voltage cardioversion / defibrillation shock therapy only. For example, either electrode 24 or 26 may be used as a sensing electrode in a sensing vector to sense cardiac electrical signals and determine the need for electrical stimulation therapy.

[0030] Electrodes 28 and 30 are relatively small surface area electrodes of a sensing electrode vector that can be used to sense cardiac electrical signals and, in some configurations, can be used to deliver relatively low-voltage pacing pulses. Electrodes 28 and 30 are referred to as pacing / sensing electrodes because they are typically configured for use in low-voltage applications, as opposed to delivering high-voltage CV / DF shocks, for example, as cathodes or anodes for delivering pacing pulses and / or sensing cardiac electrical signals. In some cases, electrodes 28 and 30 may provide pacing functionality only, sensing functionality only, or both. The cardiac electrical stimulation pulses disclosed herein can be delivered by any combination of available electrodes 24, 26, 28, 30 and / or housing 15. ICD 14 can sense cardiac electrical signals corresponding to the electrical activity of the heart 8 via a combination of sensing electrode vectors comprising combinations of electrodes 24, 26, 28 and / or 30. In some instances, housing 15 of ICD 14 is used in combination with one or more of electrodes 24, 26, 28 and / or 30 in the sensing electrode vector.

[0031] exist Figure 1A and 1B In the example illustrated herein, electrode 28 is located proximal to defibrillator electrode 24, and electrode 30 is located between defibrillator electrodes 24 and 26. One, two, or more pacing / sensing electrodes may be carried by lead body 18. For example, in some instances, a third pacing / sensing electrode may be located distal to defibrillator electrode 26. Electrodes 28 and 30 are illustrated as loop electrodes; however, electrodes 28 and 30 may comprise any of several different types of electrodes, including loop electrodes, short coil electrodes, hemispherical electrodes, directional electrodes, segmented electrodes, or the like. Electrodes 28 and 30 may be positioned along lead body 18 at other locations, not limited to those shown. In other instances, lead 16 may contain fewer or more pacing / sensing electrodes and / or defibrillator electrodes than in the examples shown herein.

[0032] In the illustrated example, lead 16 extends from connector assembly 27 of ICD 14 toward the center of the patient 12's torso (e.g., toward the xiphoid process 20 of patient 12) and medially above the thoracic cavity 32, subcutaneously or submuscularly. Near the xiphoid process 20, lead 16 bends or turns upward, subcutaneously or submuscularly, above the thoracic cavity and / or sternum 22. Although in Figure 1A The description indicates that the lead 16 extends laterally from and substantially parallel to the sternum 22, but the distal portion 25 of the lead 16 may be implanted at other locations, such as above the sternum 22, offset to the right or left of the sternum 22, angled laterally from the sternum 22 to the left or right, or similar. Alternatively, the lead 16 may be placed along other subcutaneous or submuscular pathways. The path of the cardiovascular lead 16 may depend on the location of the ICD 14, the arrangement and location of the electrodes carried by the lead body 18, and / or other factors.

[0033] Electrical conductors (not shown) extend from a lead connector at the proximal lead end 27 to electrodes 24, 26, 28, and 30 positioned along the distal portion 25 of the lead body 18 through one or more cavities of the elongated lead body 18 of lead 16. Each elongated electrical conductor (which may be a separate, corresponding insulated conductor within the lead body 18) is electrically coupled to the respective defibrillation electrodes 24 and 26 and pacing / sensing electrodes 28 and 30. The respective conductors electrically couple the electrodes 24, 26, 28, and 30 to the circuitry of the ICD 14, such as treatment delivery circuitry and / or sensing circuitry, via connections in a connector assembly 17 (including associated electrical feedthroughs through the housing 15). The electrical conductors transmit treatment from the treatment delivery circuitry within the ICD 14 to one or more of the defibrillation electrodes 24 and 26 and / or the pacing / sensing electrodes 28 and 30, and transmit sensed electrical signals generated by the patient's heart 8 from one or more of the defibrillation electrodes 24 and 26 and / or the pacing / sensing electrodes 28 and 30 to the sensing circuitry within the ICD 14.

[0034] The lead body 18 of lead 16 may be formed of a non-conductive material, including silicone, polyurethane, fluoropolymers, mixtures thereof, and / or other suitable materials, and shaped to form one or more cavities in which one or more conductors extend. The lead body 18 may be tubular or cylindrical. In other examples, the distal portion 25 (or all) of the elongated lead body 18 may have a flat, strip, or paddle-shaped shape. The lead body 18 may be formed with a pre-shaped distal portion 25, which is typically straight, curved, bent, serpentine, wavy, or serrated.

[0035] In the example shown, the lead body 18 includes a curved distal portion 25 with two "C"-shaped curves, which together resemble the Greek letter epsilon "ε". Defibrillation electrodes 24 and 26 are each carried by one of the two corresponding C-shaped portions of the distal portion 25 of the lead body. The two C-shaped curves extend or bend in the same direction away from the central axis of the lead body 18, along which the pacing / sensing electrodes 28 and 30 are positioned. In some cases, the pacing / sensing electrodes 28 and 30 may be substantially aligned with the central axis of the straight proximal portion of the lead body 18, such that the midpoints of the defibrillation electrodes 24 and 26 are laterally offset from the pacing / sensing electrodes 28 and 30.

[0036] Other examples of cardiovascular external leads comprising one or more defibrillation electrodes and one or more pacing and sensing electrodes carried by a curved, serrated, wavy, or serrated distal portion of the lead body 18 are generally disclosed in U.S. Patent Publication No. 2016 / 0158567 (Marshall et al.). However, the technology disclosed herein is not limited to any particular lead body design or electrode arrangement. In other examples, the lead body 18 is a flexible, elongated lead body without any pre-formed shape, bend, or curvature.

[0037] The ICD 14 analyzes cardiac electrical signals received from one or more sensing electrode vectors to monitor abnormal rhythms, such as cardiac arrest, bradycardia, ventricular tachycardia (VT), or ventricular fibrillation (VF). The ICD 14 can analyze the heart rate and morphology of cardiac electrical signals to monitor tachyarrhythmias according to any of several tachyarrhythmia detection techniques.

[0038] The ICD 14 generates and delivers electrical stimulation therapy in response to the detection of a tachyarrhythmia (e.g., VT or VF) using a therapeutic delivery electrode vector selectable from any of the available electrodes 24, 26, 28, 30 and / or housing 15. The ICD 14 may deliver antitachycardia pacing (ATP) in response to VT detection, and in some cases may deliver ATP prior to a CV / DF shock or during high-voltage capacitor charging to attempt to avoid the need for a CV / DF shock. If ATP fails to terminate VT or when VF is detected, the ICD 14 may deliver one or more CV / DF shocks via one or both of the defibrillation electrodes 24 and 26 and / or housing 15. The ICD 14 may deliver a CV / DF shock individually or together using electrodes 24 and 26 as cathodes (or anodes) and housing 15 as an anode (or cathode). The ICD 14 can use the pacing electrode vector of the housing 15 containing one or more of electrodes 24, 26, 28 and 30 and the ICD 14 to generate and deliver other types of electrical stimulation pulses, such as post-shock pacing pulses or bradycardia pacing pulses.

[0039] ICD 14 is shown as a subcutaneous implantation along the left side of patient 12, along the thoracic cavity 32. In some cases, ICD 14 may be implanted between the left posterior axillary line and the left anterior axillary line of patient 12. However, ICD 14 may be implanted in other subcutaneous or submuscular locations in patient 12. For example, ICD 14 may be implanted in a subcutaneous pouch in the chest region. In this case, lead 16 may extend subcutaneously or submuscularly from ICD 14 toward the manubrium of sternum 22, and bend or turn downward from said manubrium and extend to the desired subcutaneous or submuscular location. In yet another example, ICD 14 may be placed in the abdomen. Lead 16 may also be implanted in other extracardiac or extravascular locations. For example, as per [reference to...] Figures 2A to 2C As described, the distal portion 25 of the lead 16 can be implanted under the sternum / pleural cavity in the substernal space. Figure 1A and 1B This is illustrative in nature and should not be considered as limiting the practice of the techniques disclosed herein.

[0040] External device 40 is shown communicating telemetry with ICD 14 via communication link 42. External device 40 may include processor 52, memory 53, display 54, user interface 56, and telemetry unit 58. Processor 52 controls the operation of external device and processes data and signals received from ICD 14. Display 54, which may include a graphical user interface, displays data and other information to the user for viewing parameters of ICD operation and programming, as well as cardiac electrical signals retrieved from ICD 14.

[0041] User interface 56 may include a mouse, touchscreen, keypad, or the like, enabling a user to interact with external device 40 to initiate a telemetry session with ICD 14 for retrieving and / or transmitting data to ICD 14, including programmable parameters for controlling cardiac event sensing and treatment delivery. Telemetry unit 58 includes a transceiver and antenna configured for bidirectional communication with telemetry circuitry contained in ICD 14 and configured to operate in conjunction with processor 52 for sending and receiving data related to ICD functionality via communication link 42.

[0042] For example, A communication link 42 is established between ICD 14 and external device 40 via Wi-Fi or a Medical Implantable Communication Service (MICS) or other RF or communication frequency bandwidth or communication protocol. Data stored or acquired by ICD 14, including physiological signals or associated data derived therefrom, device diagnostic results, and the history of detected rhythmic episodes and delivered treatments, can be retrieved by external device 40 from ICD 14 upon request.

[0043] External device 40 may be embodied as a programmer used in a hospital, clinic, or physician's office to retrieve data from ICD 14 and program the operating parameters and algorithms in ICD 14 to control ICD functions. External device 40 may alternatively be embodied as a home monitor or a handheld device. External device 40 can be used to program cardiac signal sensing parameters, heart rate monitoring parameters, and treatment control parameters used by ICD 14. In some instances, at least some control parameters used in generating and delivering modulated cardiac electrical stimulation pulses according to the techniques disclosed herein may be programmed into ICD 14 using external device 40. In some instances, when patient 12 senses the delivered electrical stimulation pulse or experiences associated pain, patient or caregiver may use external device 40 to transmit a pain notification signal to ICD 14. (See below for further details.) Figure 11 As described, the ICD 14 can be configured to adjust the modulation of the cardiac electrical stimulation pulse signal to reduce pain or perception of the delivered electrical stimulation pulse.

[0044] Figures 2A to 2C Therefore with Figures 1A to 1B The diagram shows a concept of a patient 12 with different implant configurations and implanted leads 16. Figure 2A This is a front view of patient 12 with system 10 implanted. Figure 2B This is a side view of patient 12 with system 10 implanted. Figure 2C This is a transverse view of a patient 12 with system 10 implanted. In this arrangement, the lead 16 of system 10 is implanted in an extravascular location at least partially below the sternum 22 of the patient 12. The lead 16 extends subcutaneously or submuscularly from the ICD 14 toward the xiphoid process 20, and bends or turns within the anterior mediastinum 36 in a substernal location near the xiphoid process 20 and extends upward.

[0045] The anterior mediastinum 36 can be considered to be defined laterally by the pleura 39, posteriorly by the pericardium 38, and anteriorly by the sternum 22 (see [reference]). Figure 2C The distal portion 25 of the guide 16 may extend substantially within the loose connective tissue and / or substernal muscle tissue of the anterior mediastinum 36 along the posterior side of the sternum 22. A guide implanted such that the distal portion 25 is substantially within the anterior mediastinum 36 may be referred to as a “substernal guide”.

[0046] exist Figures 2A to 2CIn the example described, lead 16 is located substantially below the center of the sternum 22. However, in other cases, lead 16 may be implanted such that it is laterally offset from the center of the sternum 22. In some cases, lead 16 may extend laterally such that, in addition to or in place of the sternum 22, the distal portion 25 of lead 16 is below / below the thoracic cavity 32. In other examples, the distal portion 25 of lead 16 may be implanted in other extracardiac intrathoracic locations, including the pleural cavity or the pericardium 38 surrounding and adjacent to the pericardium 38 of the heart 8. For example, the distal portion 25 of lead 16 may advance to a supradiaphragmatic location, which in various examples may be intrathoracic or extrathoracic. As described above, lead 16 may alternatively advance intravenously to position electrodes for delivering electrical stimulation pulses to the heart 8 from an intravenous location.

[0047] Figure 3 This is a conceptual diagram of a circuit system that can be contained in a medical device (e.g., ICD 14) configured to deliver modulated electrical stimulation pulses, based on one example. The electronic circuit system is enclosed within a housing 15. Figure 3 The ICD (illustrated schematically as an electrode) comprises software, firmware, and hardware that collaboratively monitor cardiac electrical signals, determine when electrical stimulation therapy is needed, and deliver therapy as needed based on a programmed therapy delivery algorithm and control parameters. The ICD 14 can be connected to leads, such as lead 16 carrying electrodes 24, 26, 28, and 30, which can be positioned in an extracardiac or extravascular location for delivering electrical stimulation pulses to the patient's heart and for sensing cardiac electrical signals. In various instances, the ICD 14 can be connected to extracardiac transvenous leads, subcutaneous, submuscular, or substernal leads carrying electrodes such as electrodes 24, 26, 28, and 30 for sensing cardiac electrical signals and delivering electrical stimulation pulses to the patient's heart.

[0048] The ICD 14 includes control circuitry 80, memory 82, treatment delivery circuitry 84, cardiac electrical signal sensing circuitry 86, and telemetry circuitry 88. A power supply 98 provides power to the ICD 14's circuitry (including each of components 80, 82, 84, 86, and 88) as needed. The power supply 98 may include one or more energy storage devices, such as one or more rechargeable or non-rechargeable batteries. Connections between the power supply 98 and each of the other components 80, 82, 84, 86, and 88 will be made via... Figure 3The overall block diagram is for understanding purposes, but is not shown for clarity. For example, power supply 98 may be connected to one or more charging circuits included in treatment delivery circuitry 84 to charge a holding capacitor included in treatment delivery circuitry 84, which discharges at appropriate times under the control of control circuitry 80 to generate electrical pulses according to a treatment protocol. Power supply 98 may also be connected as needed to components of cardiac electrical signal sensing circuitry 86, such as sensing amplifiers, analog-to-digital converters, switching circuit systems, etc., to enable the cardiac electrical signal sensing functionality of sensing circuitry 86 as described herein.

[0049] Figure 3 The circuitry shown represents the functionality contained within ICD 14 and may include any discrete and / or integrated electronic circuitry components implementing analog and / or digital circuitry capable of producing the functionality attributed herein to ICD 14. The functionality associated with one or more circuits may be implemented by separate hardware, firmware, or software components, or integrated within general-purpose hardware, firmware, or software components. For example, the sensing of cardiac electrical signals (e.g., R-wave and / or P-wave sensing) and the detection of tachyarrhythmias, bradycardia, or cardiac arrest may be performed cooperatively by sensing circuitry 86 and control circuitry 80, and may include operations implemented by a processor or other signal processing circuitry system included in control circuitry 80, which executes instructions and control signals (e.g., blanking and timing) stored in memory 82 and senses threshold amplitude signals sent from control circuitry 80 to sensing circuitry 86.

[0050] The various circuits of the ICD 14 may include application-specific integrated circuits (ASICs), electronic circuitry, a processor (shared, dedicated, or grouped) and memory executing one or more software or firmware programs, combinational logic circuitry, state machines, or other suitable components or combinations of components that provide the described functionality. The specific form of the software, hardware, and / or firmware used to implement the functionality disclosed herein will be determined primarily by the specific system architecture employed in the ICD and the specific detection and treatment delivery methods employed by the ICD. Given the disclosure herein, providing software, hardware, and / or firmware to implement the described functionality in the context of any modern medical device is within the capabilities of those skilled in the art.

[0051] Memory 82 may comprise any volatile, non-volatile, magnetic, or electrically non-transitory computer-readable storage medium, such as random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, or any other memory device. Furthermore, memory 82 may comprise a non-transitory computer-readable medium storing instructions that, when executed by one or more processing circuits, cause control circuitry 80 and / or other ICD components to perform various functions attributable to ICD 14 or those ICD components. The non-transitory computer-readable medium storing instructions may comprise any of the media listed above.

[0052] The control circuit 80 communicates, for example, via a data bus with the treatment delivery circuit 84 and the sensing circuit 86, for sensing cardiac electrical activity, detecting heart rhythm, and controlling the delivery of cardiac electrical stimulation therapy in response to the sensed cardiac signals. The treatment delivery circuit 84 and the sensing circuit 86 are electrically coupled to electrodes 24, 26, 28, and 30 carried by leads 16 and housing 15, which can serve as common or ground electrodes or as active canister electrodes for delivering CV / DF shock pulses or cardiac pacing pulses.

[0053] Sensing circuitry 86 may be selectively connected to electrodes 28, 30 and / or housing 15 to monitor the electrical activity of a patient's heart. Sensing circuitry 86 may also be selectively connected to defibrillation electrodes 24 and / or 26 for use in a sensing electrode vector together or in combination with one or more of electrodes 28, 30 and / or housing 15. Sensing circuitry 86 may be enabled to selectively receive cardiac electrical signals from one or more sensing electrode vectors from available electrodes 24, 26, 28, 30 and housing 15. In some instances, at least two cardiac electrical signals from two different sensing electrode vectors may be received simultaneously by sensing circuitry 86. Sensing circuitry 86 may simultaneously monitor one or both of the cardiac electrical signals for sensing cardiac electrical events and / or generating digitized cardiac signal waveforms for analysis by control circuitry 80. For example, sensing circuitry 86 may include two sensing channels and a switching circuit system for selecting which of electrodes 24, 26, 28, 30 and housing 15 is connected to a first sensing channel and which electrodes are connected to a second sensing channel of sensing circuitry 86.

[0054] Each sensing channel can be configured to amplify, filter, and digitize cardiac electrical signals received from selected electrodes connected to the corresponding sensing channel to improve signal quality for detecting cardiac electrical events, such as R waves accompanied by ventricular depolarization (pacing-induced or inherent) and / or P waves accompanied by atrial depolarization, or to perform other signal analyses. The cardiac event detection circuitry system within sensing circuit 86 may include one or more sensing amplifiers, filters, rectifiers, threshold detectors, comparators, analog-to-digital converters (ADCs), timers, or other analog or digital components. The cardiac event sensing threshold can be automatically adjusted by sensing circuit 86 under the control of control circuit 80 based on a time period and sensing threshold determined by control circuit 80, stored in memory 82, and / or controlled by the hardware, firmware, and / or software of control circuit 80 and / or sensing circuit 86.

[0055] When a cardiac event is detected based on a sensing threshold, the sensing circuit 86 can generate a sensed event signal, such as an R-wave sensed event signal, which is then transmitted to the control circuit 80. A timing circuit 90 included in the control circuit 80 can set a pacing escape interval in response to the R-wave sensed event signal and / or the delivered pacing pulse. The pacing escape interval can be a programmed lower rate interval, a standby pacing rate interval, a post-shock pacing interval, or other pacing intervals for cardiac arrest, bradycardia, or tachycardia treatment, used to control the timing of pacing pulses delivered according to treatment control parameters and using modulation techniques disclosed herein. The control circuit 80 can be configured to operate in various pacing modes, including demand- or trigger-based bradycardia pacing modes and rate-responsive pacing modes.

[0056] The event signals sensed by the R-wave can also be used by the control circuit 80 to determine the R-R interval (RRI) to detect arrhythmias and determine the need for treatment. The RRI is the time interval between consecutively sensed R waves and can be determined between consecutive R-wave sensed event signals received from the sensing circuit 86. For example, the control circuit 80 may include a timing circuit 90 for determining the RRI between consecutive R-wave sensed event signals received from the sensing circuit 86 and for controlling various timers and / or counters for controlling the timing of treatment delivery by the treatment delivery circuit 84. The timing circuit 90 may additionally set a time window, such as a morphological template window, a morphological analysis window, or perform other timing-related functions of the ICD 14, including synchronizing CV / DF shocks or other treatments delivered by the treatment delivery circuit 84 with the sensed cardiac events.

[0057] The control circuit 80 is also shown to include a tachyarrhythmia detector 92 configured to analyze signals received from the sensing circuit 86 to detect tachyarrhythmia episodes. The tachyarrhythmia detector 92 may be implemented in the control circuit 80 as hardware, software, and / or firmware for processing and analyzing signals received from the sensing circuit 86 for detecting VT and / or VF. The timing circuit 90 uses the timing of R-wave sensing event signals received from the sensing circuit 86 to determine the RRI between consecutively sensed event signals. The tachyarrhythmia detector 92 may include comparators and counters for counting the RRIs determined by the timing circuit 92, the RRIs falling into various rate detection regions for determining ventricular rates or performing other rate- or interval-based assessments for detecting and distinguishing VT and VF.

[0058] For example, the tachyarrhythmia detector 92 can compare the RRI determined by the timing circuit 90 with one or more tachyarrhythmia detection intervals, such as tachycardia detection intervals and fibrillation detection intervals. RRIs falling within the detection intervals are counted by the corresponding VT interval counter or VF interval counter, and in some cases by a combination of VT / VF interval counters included in the tachyarrhythmia detector 92. When the interval counter value reaches the detection threshold number of intervals, a ventricular tachyarrhythmia can be detected by the tachyarrhythmia detector 92. The tachyarrhythmia detector 92 can be configured to perform further signal analysis to determine whether other detection criteria, such as R-wave morphology criteria, episodic criteria, and noise and oversensitivity suppression criteria, are met before detecting VT or VF.

[0059] To support these additional analyses, sensing circuitry 86 can transmit digitized cardiac electrical signals, such as electrocardiogram (ECG) signals, to control circuitry 80 for morphological analysis by the tachyarrhythmia detector 92. The cardiac electrical signals may pass through filters and amplifiers, be provided to a multiplexer, and subsequently converted into multi-bit digital signals by an analog-to-digital converter; all of this is contained within sensing circuitry 86 for storage in memory 82. Memory 82 may include one or more loop buffers to temporarily store segments of the digital cardiac electrical signals used for analysis by control circuitry 80. Control circuitry 80 may be a microprocessor-based controller that employs digital signal analysis techniques to characterize the digitized signals stored in memory 82, using any of the numerous signal processing methods available for analyzing cardiac signals and cardiac event waveforms (e.g., R waves) to identify and classify individual beats and patient rhythms.

[0060] The treatment delivery circuit 84 includes a signal source, a modulator, and an output circuit, as described below. Figure 6As described below, the signal source may include a charging circuit system connected to power supply 98, one or more charge storage devices (e.g., one or more high-voltage capacitors and / or low-voltage capacitors), and a switching circuit system that controls when the one or more capacitors are charged and discharged across a selected pacing electrode vector or CV / DF shock vector. The treatment delivery circuit 84 may charge the capacitors to a programmed pulse amplitude and discharge them for a programmed pulse width via a modulator and output circuitry, as described below, based on control signals received from control circuitry 80. In other instances, the signal source may be a voltage regulator or current regulator connected to power supply 98 and configured to pass a voltage or current-controlled signal to the modulator to generate a modulated high-frequency electrical stimulation pulse signal.

[0061] Control circuit 80 may include various timers or counters for controlling when cardiac pacing pulses are delivered. For example, timing circuit 90 may include a programmable digital counter set by the microprocessor of control circuit 80 for controlling the basic pacing time interval associated with various pacing modes or ATP sequences delivered by ICD 14. The microprocessor of control circuit 80 may also set pulse amplitude, pulse width, maximum frequency, minimum frequency, maximum bias offset, minimum bias offset, modulation rate of frequency, amplitude, and bias, or other control parameters for generating cardiac electrical stimulation pulses, which may be based on programmed values ​​stored in memory 82. As disclosed herein, control circuit 80 may set control signals passed to treatment delivery circuit 84 for controlling amplitude modulation, frequency modulation, and / or bias modulation of cardiac electrical stimulation pulses. For example, control circuit 80 may set control signals passed to treatment delivery circuit 84 for controlling the maximum and minimum frequencies in frequency-modulated pacing pulses, and the time intervals for frequency increases and decreases. In other examples, control circuit 80 may set control signals passed to treatment delivery circuit 84 to control the maximum and minimum offset of the cardiac electrical stimulation pulse signal, and the rate at which the offset increases and / or decreases between the maximum and minimum offset. These and other modulation control parameters are described below with reference to the accompanying drawings and flowcharts.

[0062] In some instances, the treatment delivery circuit 84 may include a high-voltage (HV) treatment circuit 83 and a low-voltage (LV) treatment circuit 85. The treatment delivery circuit 84 may be configured to deliver high-voltage therapy, such as a relatively high-voltage pacing pulse and / or CV / DF shock delivered by an extracardiac electrode. Alternatively, the treatment delivery circuit 84 may be configured to deliver relatively low-voltage therapy, such as a cardiac pacing pulse. The low-voltage treatment circuit 85 may be configured to deliver relatively low-voltage therapy by generating pulses with a maximum voltage and pulse energy much smaller than the shock pulse delivered by the HV treatment circuit 83, as described below, for example. In other instances, the treatment delivery circuit 84 is a single treatment circuit configured to generate therapeutic pulse signals within a range of voltage amplitude and pulse energy as required by a particular medical application.

[0063] The therapeutic delivery circuit 84 may include an LV therapeutic circuit 85 for delivering low-voltage pacing pulses using a pacing electrode vector selected from electrodes 24, 26, 28, 30 and / or housing 15. The LV therapeutic circuit 85 may be configured to deliver low-voltage pacing pulses, such as a maximum pulse amplitude of 8V or less, or 10V or less. One or more capacitors or other charge storage devices included in the LV therapeutic circuit 85 may be charged to voltage by an LV charging circuit, which may include a state machine, according to a programmed pacing pulse amplitude. The LV charging circuit may charge the capacitors to a multiple of the voltage of a battery included in the power supply 98 without requiring a transformer. At appropriate times, the LV therapeutic circuit 85 connects one or more capacitors to the pacing electrode vector to deliver the pacing pulse to the heart 8.

[0064] As described below, the LV therapy circuit 85 may include a high-frequency modulator for modulating the oscillation frequency of the pacing pulse signal between a maximum frequency and a minimum frequency during the pacing pulse width. The LV therapy circuit 85 may additionally include an amplitude modulator to modulate the amplitude of the pacing pulse during the pacing pulse width. The LV therapy circuit 85 may additionally or alternatively include a low-frequency bias generator for modulating the bias of the high-frequency pacing pulse signal. The LV therapy circuit 85 may generate a high-frequency pacing pulse modulated according to modulation control parameters in response to receiving a pacing timing signal from a control circuit 80 according to any of the examples described herein.

[0065] The high-voltage (HV) therapy circuit 83 may include one or more high-voltage capacitors. When a shockable rhythm is detected, the HV capacitors may be charged to the shock voltage amplitude by an HV charging circuit according to a programmed shock energy. The HV charging circuit may include a transformer and is a processor-controlled charging circuit controlled by control circuit 80. Control circuit 80 applies a signal to trigger the discharge of one or more HV capacitors when it detects a feedback signal that the HV capacitors from the therapy delivery circuit 84 have reached the shock voltage amplitude required to deliver the programmed shock energy. In this way, control circuit 80 controls the operation of the high-voltage therapy circuit 83 to deliver CV / DF shocks using defibrillation electrodes 24, 26 and / or housing 15.

[0066] In some instances, the HV therapy circuit 83 can be used to deliver cardiac pacing pulses. In this case, the HV capacitors can be charged to a voltage much lower than the voltage used to deliver electrical shock therapy, but said voltage can be higher than the maximum available pulse voltage amplitude generated by the LV therapy circuit 85. For example, one or more HV capacitors can be charged to 40V or less, 30V or less, or 20V or less to generate pacing pulses. The pulses delivered by the HV therapy circuit 83 can have a higher voltage amplitude and a relatively longer pulse width compared to the pacing pulses delivered by the LV therapy circuit 85, for delivering higher energy pacing pulses to capture the heart. A low-impedance pacing electrode vector can be used to deliver more current, for example, between electrodes 24 and 26. A longer pulse width is obtained due to the higher capacitance (and therefore the higher RC time constant) of the one or more HV capacitors. In some instances, the LV therapy circuit 85 may be able to generate a maximum pulse voltage amplitude of up to and including 10V. Due to the RC time constant associated with the low-voltage capacitor of the LV treatment circuit 85, the maximum pacing pulse width generated by the LV treatment circuit 85 can be 2 milliseconds (ms). Therefore, in some patients, the HV treatment circuit 83 can respond to a pacing timing signal from the control circuit 80 to generate and deliver cardiac pacing pulses according to the techniques disclosed herein.

[0067] The HV therapy circuit 83 can generate pulse voltage amplitudes of 10V or greater, with relatively long pacing pulse widths, such as 10ms or greater, due to the higher capacitance (and high RC time constant) of the high-voltage capacitors included in the HV therapy circuit 83. A typical HV pacing pulse width can be 10ms; however, examples of usable pulse widths can range from 0.2ms to 20ms or from 20ms up to 60ms. An example of the maximum voltage amplitude that can be used to deliver high-voltage pacing pulses is 40V. When the patient can tolerate a relatively high pacing pulse voltage amplitude (e.g., greater than 10V), a relatively short pacing pulse width (e.g., 2 to 5ms) can be delivered by the HV therapy circuit 83. However, longer pacing pulse widths, such as 10V, 20ms pacing pulses, can be used as needed.

[0068] For comparison, one or more HV capacitors that may be included in the HV treatment circuit 83 can be charged to an effective voltage greater than 100V for delivering cardioversion / defibrillation shocks. For example, two or three HV capacitors with an effective capacitance of 148 to 155 microfarads in the HV treatment circuit 83 may be provided in series. These series capacitors can be charged to generate 100 to 800V for the series combination to deliver a shock with a pulse energy of 5 joules or greater, and more typically 20 joules or greater.

[0069] Conversely, depending on the pacing electrode impedance, the pacing pulse delivered by the HV treatment circuit 83 can have pulse energy of less than 1 joule and even in the millijoule or one-tenth of a millijoule range. For example, a pacing pulse with an amplitude of 10V and a pulse width of 20ms generated by the HV treatment circuit 83 can deliver 5 to 7 millijoules of energy, delivered using a pacing electrode vector with an impedance in the range of 20 to 200 ohms. When using a relatively short pulse width (e.g., as low as 2ms), the pacing pulse delivered by the HV treatment circuit 83 using defibrillation electrodes 24 and 26 can be as low as 1 millijoule. Cardiac pacing pulses delivered by the HV treatment circuit 83 are expected to have a pacing voltage amplitude of less than 100V and typically no greater than 40V, and deliver at least 1 millijoule but less than 1 joule of energy. The delivered energy for a given pacing voltage amplitude will vary depending on the pulse width and the pacing electrode vector impedance.

[0070] If the pacing / sensing electrodes 28 or 30 are included in the pacing electrode vector, producing a relatively high impedance (e.g., in the range of 400 to 1000 ohms), then the delivered pacing pulse energy can be in the range of 2 to 5 millijoules. The HV treatment circuit 83 can deliver more current via a lower impedance pacing electrode vector (e.g., between defibrillation electrodes 24 and 26) than the LV treatment circuit 85 can deliver via a pacing electrode vector containing the pacing / sensing electrodes 28 or 30 (with relatively high impedance), even when the pacing voltage amplitude is also equal. The relatively high pacing pulse amplitude and width required to capture myocardium by electrodes positioned in the extracardiac pacing location can lead to extrinsic activation of non-cardiac tissues, causing the patient to perceive the delivery of the pacing pulse and / or experience discomfort or pain. The high-frequency modulation of the pacing pulse signal as disclosed herein is expected to reduce the perceived and / or pain experienced by the patient during extracardiac pacing pulse delivery by blocking sensory and / or motor nerves that might otherwise be captured by the extracardiac pacing pulse.

[0071] Either the HV treatment circuit 83 or the LV treatment circuit 85 can be selected to generate and deliver cardiac pacing pulses using the techniques disclosed herein, depending on the pacing capture threshold of the given patient's myocardium. The HV treatment circuit 83 is configured to deliver CV / DF shock pulses, but can be selected by the control circuit 80 to deliver pacing pulses, such as for delivering ATP, post-shock pacing pulses, or ventricular pacing pulses during atrioventricular block, bradycardia, or cardiac arrest. The HV treatment circuit 83 may include a frequency modulator, a bias modulator, and an amplitude modulator as described below for generating cardiac pacing pulses with modulated high-frequency oscillations over the pacing pulse width, modulated between a maximum and a minimum frequency. In this way, the HV treatment circuit 83 can generate cardiac electrical stimulation pulse signals that effectively capture the heart but reduce patient discomfort or perception of the delivered pulse signal. The high-frequency component of the expected pacing pulse blocks sensors and / or motor nerves to minimize extrinsic activation of non-cardiac tissues.

[0072] In response to the detection of VT or VF, control circuit 80 can control treatment delivery circuit 84 to deliver treatment, such as ATP and / or CV / DF treatment. Treatment, including treatment for tachyarrhythmias, bradycardia, cardiac arrest, and post-shock therapy (as examples), can be delivered by initiating charging of a high-voltage capacitor via a charging circuit, both of which are included in HV treatment circuit 83. Charging is controlled by control circuit 80, which monitors the voltage on the high-voltage capacitor, which is transmitted to control circuit 80 via a charging control line. When the voltage reaches a predetermined value set by control circuit 80, a logic signal is generated across the capacitor and transmitted to treatment delivery circuit 84, thereby terminating charging. CV / DF or pacing pulses are delivered to heart 8 via a control bus by output circuit of HV treatment circuit 84 under the control of timing circuit 90. Output circuit may include output capacitors through which the charged high-voltage capacitors discharge via a switching circuit system (e.g., an H-bridge), which determines the electrodes and pulse waveforms used for delivering CV / DF or pacing pulses.

[0073] Control parameters used by control circuitry 80 to sense cardiac events and control treatment delivery can be programmed into memory 82 via telemetry circuitry 88. Telemetry circuitry 88 includes a transceiver and antenna for communication with external device 40 (in...) using RF communication or other communication protocols as described above. Figure 1A (As shown in the diagram) Communication. Under the control of control circuit 80, telemetry circuit 88 can receive downlink telemetry from external device 40 and send uplink telemetry to external device 40. In some cases, telemetry circuit 88 can be used to transmit communication signals to / receive communication signals from another medical device implanted in patient 12. In some instances, telemetry circuit 88 can receive pain notification signals from external device 40. Control circuit 80 can receive pain notification signals and adjust electrical stimulation pulse modulation control parameters to reduce pain or sensation of the delivered pulse signals.

[0074] Figure 4This is a depiction of a modulated high-frequency pacing pulse signal 100 generated by a therapeutic delivery circuit 84 according to one example. In this example, pulse 100 is shown as having a total pulse width 102 of 10 milliseconds (ms). The pulse amplitude increases from 0 to a maximum pulse amplitude 104 over the first 50% of the pacing pulse width 102 (5 ms in this example). The pulse amplitude 104 may be in the range, for example, between 0.25 volts and 10 volts, or fall within the range of other examples listed herein. In the various illustrative examples described herein, the pulse signal generated by the therapeutic delivery circuit 84 may be a voltage-controlled signal, wherein the amplitude of the signal is a voltage amplitude. However, it should be understood that in any of the examples presented herein, the therapeutic delivery circuit 84 may generate a current-controlled signal, in which case the amplitude of the signal is a current amplitude rather than a voltage amplitude. In either case, according to the examples disclosed herein, the voltage or current amplitude may be modulated by the therapeutic delivery circuit 84 over the pulse width 102.

[0075] exist Figure 4 In the second 50% of the pulse width 102 (from 5 ms to 10 ms in this example), the amplitude decreases from the maximum amplitude 104 to 0V. The bias 112 can be controlled at 0V by the treatment circuitry 84. The pacing pulse 100 is biphasic, such that the resulting envelope of the amplitude of the modulated pacing pulse oscillation, as shown, is sinusoidal. In other examples, the amplitude of the modulated high-frequency pacing pulse signal 100 can be fixed over the duration of the pulse width 102 to produce a square pacing pulse signal. In still other examples, the amplitude of the oscillation can be modulated or adjusted over the pulse width 102 to produce various pulse shapes, including triangular, sawtooth, step-up, step-down, ramp, ramp, sinusoidal, or any combination thereof (as examples).

[0076] The treatment delivery circuit 84 modulates the frequency of the pacing pulse 100 by reducing the frequency from a starting frequency to a minimum frequency, which in some instances may be 50 Hz or less, and may be close to 0 Hz. The oscillation frequency of the pulse signal 110 decreases on a first portion 106 of the pulse width 102, which in this instance may be half the pulse width 102, ranging from 0 to 5 ms. The treatment delivery circuit 84 increases the oscillation frequency from the minimum frequency to the end frequency on a second portion 108 of the pulse width 102, which in this instance may be the second half of the pulse width 102, ranging from 5 ms to 10 ms. In various instances, the starting frequency of the oscillation at the beginning (0 ms) of the pulse width 102 may be in the range of 500 Hz to 5000 kHz. In some instances, the starting frequency is in the range of 1 kHz to 10 kHz and may be 2.5 kHz or 5 kHz (as examples). The end frequency at the end of the pulse width 102 (10 ms in this instance) may be equal to the starting frequency, but not necessarily. The ending frequency can be equal to, higher than, or lower than the starting frequency. In some instances, both the starting and ending frequencies are greater than the minimum frequency reached during the pacing pulse width 102. At least one of the starting or ending frequencies can be the maximum frequency during the pacing pulse 100. The starting frequency at the beginning of the pulse width 102 can be the maximum frequency that decreases to a minimum frequency during the pulse width 102, and said frequency may or may not increase again after reaching the minimum frequency. (See the following in conjunction with...) Figure 10 In some of the examples described, the end frequency can be the minimum frequency during a pulse width of 102.

[0077] exist Figure 4 In one example, the pacing pulse signal 100 is shown to be symmetrical at the midpoint of the pulse width 102; however, the first portion 106 of the pulse width 102 need not be the first half of the pulse width 102, on which the pulse frequency decreases from the starting frequency to the minimum frequency, as shown. In other examples, the treatment delivery circuit 84 may decrease the frequency from the starting frequency to the minimum frequency on the first portion 106 of the pulse width 102, which may be greater than or less than half of the pulse width 102. The treatment delivery circuit 84 may increase the frequency from the minimum frequency to the ending frequency on the remaining second portion 108 of the pulse width 102, which may be less than or greater than half of the pulse width 102, depending on the duration of the first portion 106.

[0078] The high-frequency oscillation of the pulse signal 100 delivered during the first portion 106 blocks motor and / or sensory nerves that would otherwise be activated by the pacing pulse, causing pain or other sensations. As the initial high frequency of the oscillation decreases and the pulse amplitude increases during the first portion 106, the net delivered charge of the pacing pulse signal 100 reaches the cardiac capture threshold for inducing myocardial depolarization. The minimum frequency may occur at a time corresponding to the maximum pulse amplitude 104 during the pulse width 102, as indicated by the low-frequency, high-amplitude portion 110 of the pulse signal 100. The minimum frequency and the maximum pulse amplitude 104 may be reached simultaneously during the pulse width 102, either at the midpoint of the pulse width 102 or not, as shown herein. By reducing the frequency from an initial high frequency (e.g., greater than 1 kHz or higher) to a minimum frequency (e.g., 50 Hz or lower), and decreasing the frequency (and in this example, increasing the pulse amplitude), the pulse signal generates charge accumulation, causing the delivered current to increase as the frequency decreases until myocardial capture occurs. After myocardial capture occurs, the frequency can be increased again (with a reduced amplitude in this example).

[0079] In some instances, a recharge pulse may follow the modulated high-frequency pulse signal, which is a secondary pulse that causes an equal amount of charge to flow in the opposite direction to the modulated high-frequency pulse signal. The charge in the recharge pulse is intended to be equal to the amount of charge in the therapeutically modulated high-frequency pulse signal to minimize charge accumulation at the electrode surface over time. Over time, charge accumulation at the electrode-tissue interface can lead to chemical reactions at the electrode-tissue interface, potentially causing tissue and / or electrode damage over time.

[0080] The therapeutically modulated high-frequency reduction of the pacing pulse signal 100 reduces the patient's perception and / or discomfort during the delivery of the pacing pulse signal 100 to capture the patient's heart. The start and / or end frequencies can be selected such that the high-frequency component of the pacing pulse signal 100 blocks sensory and / or motor nerves to minimize or avoid activation of sensory and / or motor nerves, while still capturing the myocardium through the low-frequency portion 110 of the pacing pulse signal 100. The pulse signal 100 includes a low-frequency component with a pulse amplitude within a pulse width 102 that meets or exceeds the myocardial capture threshold during portion 110.

[0081] Although in the illustrated example, the maximum pulse amplitude 104 (and twice the peak-to-peak amplitude of the maximum pulse amplitude 104) occurs at the midpoint of the pulse width 102, the maximum pulse amplitude 104 may occur earlier than the midpoint and may be maintained, for example, as a portion of the pulse width 102 with a rhomboid wave. In other examples, the maximum pulse amplitude 104 may be reached earlier in the first portion 106 and begin to decrease before the midpoint of the pulse width 102. In some cases, the maximum pulse amplitude 104 may be reached during a relatively high-frequency portion of the pulse signal 100 (e.g., earlier in portion 106) to facilitate the blocking of sensory and / or motor nerves before the low-frequency portion 110 of the pulse signal 100, particularly when high amplitude is required to capture the myocardium during the low-frequency portion 110. In some examples, the maximum peak amplitude 104 of the pulse signal 100 may be reached before reaching the minimum frequency and maintained at the maximum pulse amplitude through the minimum frequency portion until the frequency increases again. In other instances, the maximum pulse amplitude may be maintained at its maximum value until the pulse width 102 expires or decreases to a lower pulse amplitude during the low-frequency portion 110 of the myocardium capture. The pulse amplitude may or may not be at its maximum value during the low-frequency portion 110, but it must be at least high enough during the low-frequency portion 110 of the pulse signal 100 to capture the myocardium and induce depolarization.

[0082] Figure 5 It is based on another instance. Figure 3 A depiction of the modulated high-frequency pacing pulse signal 130 generated by the treatment delivery circuit 84. The pulse signal 130 has a total pulse width 132, shown in this example as 60 milliseconds (ms), but the pulse width may be shorter depending on any of the examples given herein. In various examples, the modulated high-frequency pacing pulse signal generated by the treatment delivery circuit 84 may have a pulse width of 1 ms or less or up to 60 ms or more. The duration of the pulse width may depend on the pulse energy required to capture tissue for a particular therapeutic application and the treatment delivery circuitry used to generate the pulse signal. In some examples, the pulse width is in the range of 0.02 ms to 1.2 ms. In other examples, the pulse width is in the range of 1 ms to 10 ms. In other examples, the pulse width is in the range of 10 ms to 40 ms. In still other examples, the pulse width is in the range of 30 ms to 60 ms.

[0083] On the first frequency reduction portion 136 of the pulse width 132, the oscillation frequency of the pulse signal 130 decreases from a high frequency at the start time (0 ms) of the pulse width 132 to a minimum frequency, which may be close to 0 Hz. The frequency may effectively be 0 Hz at its minimum, but due to constraints of the pulse generation circuitry, a true 0 Hz signal may not be achieved. In various instances, the minimum frequency may be less than or equal to 100 Hz, less than or equal to 50 Hz, less than or equal to 20 Hz, less than or equal to 10 Hz, less than or equal to 5 Hz, less than or equal to 1 Hz, or as low as 0.1 Hz. The frequency increases from the minimum frequency on the second frequency increase portion 138 until the pulse width 132 expires. The frequency reduction portion 136 may be greater than the second frequency increase portion 138 of the pulse width 132. In the illustrated example, the second frequency increase portion 138 is 20% of the first reduction portion 136. However, the second portion 138 may be any percentage of the first portion 136 or the total pulse width 132.

[0084] The first frequency reduction portion 136 may be at least 50% or more (up to 100%) of the pulse width 132 to facilitate nerve block and minimize perception or discomfort caused by the pacing pulse signal during the high-amplitude, low-frequency portion 140 by delivering high frequencies as the pulse amplitude decreases and increases until the maximum pulse amplitude 134 is reached. However, in other instances, the first frequency reduction portion 136 may be less than 50% of the pulse width. In one instance, the first portion 136 is between 10% and 30% of the pulse width 132, and the second portion 138 is between 90% and 70% of the pulse width. In another instance, the first portion is between 30% and 50% of the pulse width, and the second portion is between 70% and 50% of the pulse width. In yet another instance, the first portion is between 50% and 100% of the pulse width 132, and the second portion is between 0% (without the frequency increase portion) and 50% of the pulse width 132. These ranges are provided as examples and are not intended to be limiting.

[0085] The final frequency reached at the end of pulse width 132 may be lower than the initial frequency at the beginning of pulse width 132 because the frequency increase portion 138 is shorter than the frequency decrease portion 136. In the illustrated example, the rate of frequency decrease on the first portion 136 may be equal in magnitude to the rate of frequency increase on the second portion 138. However, since the second portion 138 is shorter in duration than the first portion 136, the final frequency is lower than the initial frequency at the beginning of pulse width 132. In other examples, the rate of frequency increase may be greater than the rate of frequency decrease, causing the frequency to increase more rapidly on the second portion 138 of pulse width 132. In this case, the final frequency at the end of pulse width 132 may be less than or equal to the initial frequency. In some cases, the final frequency may be greater than the initial frequency.

[0086] In this example, the pulse amplitude of the oscillation of the pulse signal 130 increases from zero to a maximum pulse amplitude 134 on a first frequency reduction portion 136 of the pacing pulse width 132, and decreases from the maximum pulse amplitude 134 to zero on a second frequency increase portion 138 of the pulse width 132 (from 50 ms to 60 ms in this example). The pacing pulse signal 130 is biphasic, with the bias 142 controlled at zero amplitude. The resulting maximum amplitude envelope 144 and the minimum amplitude envelope 146 of the oscillation of the modulated high-frequency pacing pulse signal 130 are both triangular in shape. However, other shapes of the modulated high-frequency pacing pulse signal with the first frequency reduction portion 136 and the optional second frequency increase portion 138 are possible. Figure 4 and Figure 5 The sine and triangle shapes shown are for illustrative purposes only and are not intended to relate to amplitude modulation of pulse signals 100 and 130 over their respective pulse widths 102 and 132. The maximum pulse amplitude 104 or 134 occurs near or coincides with the minimum frequency of pulses 100 or 130, making the high-amplitude, low-frequency portion of the pacing pulse signal ( Figure 4 Part 110 and Figure 5 Part 140) captures the myocardium. In other instances, step changes or other nonlinear rates of change, instead of the constant rate of change shown, can be used to upmodulate or adjust the pulse amplitude to the maximum amplitude 134 on the first reduced frequency part 136.

[0087] The amplitude of pulse 130 decreases at a faster rate on the second increasing frequency portion 138 than it increases on the first decreasing frequency portion 136. Therefore, the amplitude is shown to decrease from the maximum pulse amplitude 134 to zero at the end of the shorter second portion 138. However, in various instances, the rate of amplitude change on the first portion 136 and the second portion 138 may be the same or different. The rate of decrease in pulse amplitude may be slower than shown, such that the amplitude of the final pulse of the high-frequency oscillation at the end of pulse width 132 may be greater than 0. In other instances, the pulse amplitude may remain constant at the maximum pulse amplitude 134 for the duration of the second portion 138 until the end of pulse width 132. In this case, only the frequency is modulated on the second portion 138 of pulse width 132.

[0088] Figure 6 This is a conceptual diagram of a treatment delivery circuit 84 based on one example. As described above, in some examples, the treatment delivery circuit 84 may include an HV treatment circuit 83 and an LV treatment circuit 85. In other examples, the treatment delivery circuit 84 may include an HV treatment circuit 83 without an LV treatment circuit 85, or it may include an LV treatment circuit 85 without an HV treatment circuit 83. Figure 6The components shown, such as signal source 150, modulator 151, pulse width timer 164, and output circuit 158, may correspond to components included in HV treatment circuit 83 and / or LV treatment circuit 85. In some examples, Figure 6 Some components shown may be included in both HV treatment circuit 83 and LV treatment circuit 85, or shared between HV treatment circuit 83 and LV treatment circuit 85. The components and associated functionality of HV treatment circuit 83 or LV treatment circuit 85 may be provided by... Figure 6 The components shown herein represent the components. Therefore, the HV treatment circuit 83 and / or the LV treatment circuit 85 can be configured to generate an electrical stimulation pulse signal using the modulation techniques disclosed herein. In some instances, the electrical stimulation pulse signal is a relatively low-energy cardiac pacing pulse (generated by the LV treatment circuit 85 or the HV treatment circuit 83) used to pace the patient's heart at a desired rate. In other instances, the cardiac electrical stimulation signal is a high-energy cardioversion / defibrillation pulse generated by the HV treatment circuit 83 to terminate rapid arrhythmias, such as tachycardia or fibrillation.

[0089] The treatment delivery circuit 84 includes a pulse signal source 150 that receives power from the power supply 98 of the ICD 14 on line 165. The pulse signal source 150 can be a voltage-controlled signal source or a current-controlled signal source. The pulse signal source 150 receives a pacing timing signal 160 from the control circuit 80. The pulse signal source 150 responds to the pacing timing signal 160 by initiating a pulse signal delivered to the modulator 151. In some instances, the signal source 150 includes a charging circuit and one or more holding capacitors or other charge storage devices, which are charged by the charging circuit to generate a desired maximum pulse amplitude (e.g., ...). Figure 4 The voltage required for the electrical stimulation pulse signal (maximum pulse amplitude 104) shown in the diagram. One or more holding capacitors may be charged before receiving the pacing timing signal 160 (e.g., during the pacing (or other stimulation) interval) or in response to receiving the pacing timing signal 160. As described above, when the signal source 150 is included in the HV treatment circuit 83, the signal source 150 may include a transformer (connected to power supply 98) charged to the desired voltage under the control of the processor and one or more high-voltage capacitors. In one example, the high-voltage capacitors may comprise two or three high-voltage capacitors with an effective capacitance of 148 to 155 microfarads connected in series.

[0090] When the pulse signal source 150 is included in the LV treatment circuit 85, the pulse signal source 150 may include a state machine and one or more low-voltage holding capacitors. The pulse signal source 150 may be configured to charge one or more low-voltage holding capacitors to a multiple of the voltage of the battery included in the power supply 98 without the need for a transformer. The pulse signal source 150 may include one or more low-voltage capacitors, each having a capacitance of up to 6 microfarads, up to 10 microfarads, up to 20 microfarads, or other selected capacitance, but all having a capacitance significantly smaller than the effective capacitance of the high-voltage capacitors included in the HV treatment circuit 83. The low-voltage holding capacitors included in the LV treatment circuit 85 may have a lower breakdown voltage than the high-voltage holding capacitors in the HV treatment circuit 83, thereby allowing one or more high-voltage capacitors to be charged to the shock voltage amplitude required to deliver a CV / DF shock, such as 100V or greater.

[0091] In response to the pacing timing signal 160, the pulse signal source 150 can transmit a signal to the modulator 151 for generating a high-frequency electrical stimulation pulse signal, such as a cardiac pacing pulse, which is delivered via a selected electrode vector 168. The electrode vector 168 can be selected from any available electrode, such as... Figure 1A and 2A Electrodes 24, 26, 28, 30 and / or housing 15 are shown. The signal from pulse signal source 150 is transmitted to output circuit 158 ​​via modulator 151, which can provide high-frequency modulation by high-frequency modulator 152, bias modulation by low-frequency bias generator 156, and / or amplitude modulation by amplitude modulator 154. In one example, modulator 151 includes high-frequency modulator 152 configured to downmodulate the signal from pulse signal source 150 from a starting frequency to a minimum frequency, and to increase the frequency from the minimum frequency to the ending frequency during the pulse width, as described above. Figure 4 and 5 As described. The high-frequency modulator 152 can modulate the oscillation frequency of the pulse signal according to frequency modulation control parameters, which can be received from the control signal 161 transmitted from the control circuit 80 to the modulator 151.

[0092] In some instances, the start frequency is the maximum frequency of the pulse signal. The end frequency may be equal to the maximum frequency of the pulse signal. In some instances, the start frequency and the end frequency may be the same frequency. In other instances, the high-frequency modulator 152 may modulate the frequency of the pulse signal upward from the start frequency to a first maximum frequency greater than the start frequency and downward from the first maximum frequency to a minimum frequency during a first portion of the pulse width. In some instances, the high-frequency modulator 152 may modulate the frequency of the pulse signal upward from the minimum frequency to a second maximum frequency greater than the end frequency during a second portion of the pulse width and downward from the second maximum frequency to the end frequency. The start frequency and the end frequency may or may not be the same frequency. The first maximum frequency and the second maximum frequency may or may not be the same frequency.

[0093] The treatment delivery circuit 84 may include a pulse width timer 164 that receives a pacing pulse width signal 162, which can provide timing signals to a high-frequency modulator 152, a low-frequency bias generator 156, and an amplitude modulator 154. For example, the timing signal from the pulse width timer 164 can be used by the high-frequency modulator 152 to control time intervals of decreasing and increasing frequency over one or more portions of the pulse width (e.g., over a first and second portion of the pulse width), such as... Figure 4 and 5 As shown in the diagram. In some instances, the high-frequency modulator 152 maintains a constant high-frequency carrier signal over the entire pulse width, without modulating between the minimum and maximum frequencies. In these instances, the low-frequency bias generator 156 can be enabled to modulate the bias of the high-frequency signal to generate a pulse signal that results in a net charge accumulation at electrode vector 168 over the pulse width, which induces a net current flow to capture myocardium (or another target tissue).

[0094] Modulator 151 may include a low-frequency bias generator 156 to modulate the bias of a high-frequency signal, which may include a constant high frequency during frequency modulation or pulse width modulation. The low-frequency bias generator 156 may be configured to maintain the bias of the high-frequency signal received from high-frequency modulator 152 at a constant offset (e.g., 0 offset), such as... Figure 4 and 5 As illustrated in the examples. In other examples, the low-frequency bias generator 156 can slowly modulate the bias of the high-frequency pulse signal received from the high-frequency modulator 152 to cause charge imbalance accumulation, resulting in myocardial pacing capture during the pacing pulse signal. The following is in conjunction with... Figure 7 and 8 The example pulse signal shown in the figure is used to describe an example of a pulse signal containing bias modulation.

[0095] When the low-frequency bias generator 156 modulates the bias of a high-frequency pulse signal, the high-frequency pacing pulse signal received from the high-frequency modulator 152 may or may not be frequency modulated during the pulse width. As discussed below, when the low-frequency bias generator 156 is configured to modulate the bias, the high-frequency modulator 152 can output a fixed frequency signal, such as a 2.5 kHz or 5.0 kHz signal, for the duration of the pulse width. The bias can be modulated between a minimum offset (e.g., 0 offset) and a maximum offset during the pulse width. The bias can be modulated by controlling the low-frequency cutoff for how long the bias is maintained at the offset value (without significant decay) and the high-frequency cutoff for controlling the frequency at which the offset is adjusted from one value to another. For example, by setting the low-frequency cutoff to 0 Hz based on the control signal 161 from the control circuit 80, the bias can, for example, remain constant at zero offset. As an example, the low-frequency bias generator 156 can frequently adjust the offset every 1 ms by setting the high-frequency cutoff to 1 kHz. The low-frequency bias generator 156 modulates the bias according to bias modulation control parameters included in the control signal 161 by adjusting the offset of the signal bias according to a specified timing or frequency interval. The bias of the high-frequency signal can be modulated to have a sinusoidal, square, slanted, or other desired shape to facilitate net charge accumulation at the electrode vector 168 during the pulse signal. As an example of bias control parameters, the control signal 161 from the control circuit 80 may include bias modulation control parameters used by the low-frequency bias generator 156 to control the minimum offset, maximum offset, rate of change of the offset (increasing and / or decreasing), number of low-frequency oscillations of the bias during the pulse width, width of each oscillation, amplitude of each oscillation, and / or time interval of a constant offset, which may be a zero offset or a non-zero offset.

[0096] In some instances, the treatment delivery circuit 84 includes an amplitude modulator 154. The amplitude modulator 154 can receive a high-frequency signal, which may be a frequency-modulated and / or bias-modulated signal. The amplitude modulator 154 can modulate the pulse amplitude of the received signal to generate an output pulse signal having a desired maximum pulse amplitude and a desired envelope or shape defined by the oscillation amplitude of the pulse signal. The amplitude modulator 154 can receive amplitude modulation control parameters from a control signal 161 from the control circuit 80, including amplitude control parameters for controlling the rate of change of the oscillation of the high-frequency signal received from the low-frequency bias generator 156 (or, in some instances, from the high-frequency modulator 152) and the minimum and maximum amplitudes. The amplitude modulator 154 can also receive signals from a pulse width timer 164 for controlling the amplitude modulator 154 to adjust the timing of the oscillation amplitude of the pulse signal, such that, for example, the maximum pulse amplitude occurs during the pulse width at a specified time, the maximum pulse amplitude being consistent with the minimum frequency, maximum bias offset, or other characteristics of the high-frequency signal received from the low-frequency bias generator 156.

[0097] Various pulse shapes, such as square, triangular, sawtooth, oblique, stepped, and sinusoidal, can be generated by amplitude modulator 154. Amplitude modulator 154 can be configured to modulate the amplitude from the initial pulse amplitude to the maximum pulse amplitude in a first portion of the pulse width, and from the maximum pulse amplitude to the end pulse amplitude in a second portion of the pulse width. Amplitude modulator 154 can receive a timing signal from pulse width timer 164 for controlling the timing of amplitude modulation over the pulse width. For example, amplitude modulator 154 can be configured to modulate the amplitude to a maximum pulse amplitude that coincides temporally with the minimum frequency of the pulse signal, such that net charge accumulation causes myocardial capture during the pulse signal. In other instances, amplitude modulator 154 modulates the pulse amplitude to achieve a maximum pulse amplitude that temporally corresponds to the maximum offset of the bias. However, the maximum amplitude of the pulse signal can be reached before or after the minimum frequency and / or the maximum bias offset. The maximum pulse amplitude can occur within the time interval of the minimum frequency and / or the maximum bias offset, for example... Figure 4 Within a time interval of 110, the pulse energy within a portion of the pulse signal is equal to or exceeds the energy required to capture the myocardium and induce depolarization.

[0098] In some cases, amplitude modulator 154 can maintain the oscillation amplitude of the pulse signal at a constant maximum pulse amplitude, which is all or part of the pulse width. The pulse signal generated by modulator 151 may correspond to any of the example pulse signals described herein and / or shown in the accompanying drawings, each pulse signal comprising modulation of a high-frequency oscillation between a minimum and a maximum frequency and / or modulation of a bias between a minimum and a maximum offset, so as to accumulate net charge at electrode vector 168 during the capture of the myocardial pulse signal.

[0099] A pulse width timer 164 transmits a pulse width timing signal to an output circuit 158 ​​to control the opening and closing of switches included in the output circuit 158 ​​for connecting the output of modulator 151 to electrode vector 168. The output circuit 158 ​​includes a switching circuit system configured to connect a modulated high-frequency pulse signal to the selected electrode vector 168 for the duration of a pacing pulse width controlled by the pulse width timer 164. The output circuit 158 ​​may include one or more switches connecting the output of modulator 151 to the selected electrode vector 168 via a switching circuit system (e.g., an H-bridge or a combination of switches and diodes). The switches included in the output circuit 158 ​​may be implemented as silicon controlled rectifiers (SCRs), insulated-gate bipolar transistors (IGBTs), metal-oxide-semiconductor field-effect transistors (MOSFETs), and / or other switching circuit components or combinations thereof.

[0100] Figure 7This is a depiction of an electrical stimulation pulse signal 200 that can be generated by a therapeutic delivery circuit 84, according to another example. As an example, the pulse signal 200 may be a cardiac pacing pulse or a CV / DF shock pulse. Continue to refer to... Figure 6 The high-frequency modulator 152 can generate a high-frequency signal, such as 2.5 kHz, 5 kHz, or other selected frequencies. In this example, the high-frequency oscillation of the pulse signal 200 has a constant frequency. The amplitude modulator 154 can modulate the amplitude of the high-frequency oscillation over the pulse width 202 from a starting minimum pulse amplitude, which may be 0 volts, to a maximum amplitude 220 and then down to an ending amplitude, for example, back to 0 volts. In this example, the modulation of the amplitude of the oscillation of the high-frequency pulse signal 200 produces a sinusoidal envelope 210 of the maximum amplitude of the oscillation of the pulse signal 200.

[0101] The low-frequency bias generator 156 can modulate the bias 212 of the high-frequency signal at a modulated low frequency over the pulse width 202. For example, the bias 212 can be modulated over the offset range 208 from an initial minimum offset 216 (e.g., at 0 volts) to a maximum offset 218. In this example, the maximum offset 218 can have an amplitude up to 100% of the maximum pulse amplitude 220 of the high-frequency oscillation of the pacing pulse 200. In other examples, the maximum offset 218 can be greater than or less than the maximum pulse amplitude 220 of the high-frequency oscillation. Depending on the rate at which the bias 212 is increased and the rate at which the pulse amplitude is increased, the offset of the bias 212 can sometimes be greater than the pulse amplitude of the high-frequency oscillation during the pulse width, and at other times less than or equal to the pulse amplitude of the high-frequency oscillation of the pulse signal. In this example, the maximum pulse amplitude 220 of the high-frequency oscillation is temporally aligned with the maximum offset 218, generating the overall maximum peak-to-peak amplitude 204 of the pulse signal 200.

[0102] The low-frequency bias generator 256 can frequently adjust the offset of the pulse signal 200 every 1 ms to generate a bias 212 of any desired shape and rate of change over the pulse width 202. In the example shown, during this 20 ms pulse width 202, the oscillation frequency of the bias 212 between the minimum initial offset 216 and the maximum offset 218 can correspond to a low frequency of 50 Hz (as an example). This low-frequency modulation of the bias 212 causes charge accumulation during the pulse signal 200, which causes myocardial capture and subsequent myocardial depolarization during the pulse signal 200. In this case, the charge accumulation during the pulse signal 200 is caused by the low-frequency modulation of the bias 212 of the pulse signal 200, without the need for frequency modulation of the high-frequency oscillation of the pulse signal 200. In various examples, the bias 212 of the pulse signal 200 can be modulated at frequencies from 2 Hz to 500 Hz without being intended to limit it, and in some examples, it is modulated at frequencies from 10 Hz to 300 Hz. The frequency of the bias-modulated oscillation can be selected in part based on the pulse width 202. For a relatively short pulse width 202, a relatively high modulation frequency of the bias 212 can be used to facilitate at least a quarter cycle, at least a half cycle, at least one cycle, or multiple cycles, such as up to four cycles, of the bias oscillation between the minimum and maximum offsets during the pulse width 202. The modulation of the bias 212 causes the minimum amplitude envelope 214 of the high-frequency oscillation to have a sinusoidal shape different from the maximum amplitude envelope 210.

[0103] exist Figure 4 pulse signal 100 or Figure 5 The charge accumulation caused by myocardial capture during the pulse signal 130 is generated by high-frequency modulation performed by the high-frequency modulator 152. Figure 7 pulse signal 200 and Figure 8 The accumulation of captured charge during the pulse signal 250 (described below) is caused by low-frequency bias modulation performed by the low-frequency bias generator 156. Therefore, in some instances, the high-frequency modulator 152 may be configured to generate a fixed high-frequency signal without frequency modulation, and the low-frequency bias generator 156 may be configured to generate a low-frequency bias change to produce an electrical stimulation pulse that captures the myocardium and reduces patient-perceived and / or uncomfortable electrical stimulation pulses compared to electrical stimulation pulses that do not contain high-frequency oscillations. In other instances, the high-frequency modulator 152 is configured to downmodulate the high frequency from the starting frequency to a minimum frequency, and the low-frequency bias generator 156 may be optional or configurable to maintain a constant offset, such as 0 offset, of the high-frequency signal generated by the high-frequency modulator 152. Figure 4 and 5 As shown in the illustration. In other instances, the treatment delivery circuit 84 may be configured to generate high-frequency modulation (e.g., as shown in the illustration). Figure 4 and 5 (as shown in the image) and low-frequency bias modulation (e.g., as shown in the image) Figure 7 and 8 (As shown in the diagram) A combination of both electrical stimulation pulse signals. In each of these cases, amplitude modulation by amplitude modulator 154 may or may not be performed. In some instances, the high-frequency modulated and / or low-frequency bias modulated signals may have a fixed pulse amplitude throughout the entire duration of the pulse width.

[0104] Figure 8 This is a depiction of a modulated electrical stimulation pulse signal 250, which can be generated by a therapeutic delivery circuit 84, according to another example. A high-frequency modulator 152 can generate a constant high-frequency signal, such as 2.5 kHz, 5 kHz, or other selected frequencies, which can be between 1 kHz and 10 kHz, without being intended to limit it. An amplitude modulator 154 can modulate the pulse amplitude of the high-frequency oscillation from an initial amplitude (which may be 0 volts) to a maximum pulse amplitude 270 (with a maximum peak-to-peak amplitude 254) and downmodulate it back to an ending amplitude (e.g., back to 0 volts or a value greater than 0 volts) over a pulse width 252 to generate a generally sinusoidal maximum amplitude envelope 260 of the pulse signal 250. The maximum envelope 260 of the pulse signal 250 can be varied by different modulations of the pulse amplitude of the high-frequency oscillation by the amplitude modulator 154. Figure 8 The amplitude modulator 154 may be any of the examples given herein, as shown in the different configurations.

[0105] A low-frequency bias generator 156 can modulate a bias 262 of a high-frequency signal over a pulse width 252. The bias 262 can begin at a minimum offset (e.g., 0V) and modulate to a maximum offset 258, which in some instances may be equal to the maximum pulse amplitude 270 of the high-frequency oscillation. In this example, the minimum amplitude envelope 264 of the high-frequency oscillation is observed to increase from a minimum of 0V to a maximum amplitude aligned with the maximum peak-to-peak amplitude 254, and then return to the minimum offset of 0V over the pulse width 252. Figure 7 The different shapes of the minimum amplitude envelope 264, compared to the minimum amplitude envelope 214 of the pulse signal 200 shown, are achieved by the different rates at which the offset is increased and decreased by the low-frequency offset generator 256 than the rates at which the pulse amplitude is increased and decreased by the amplitude modulator 154. For example, the initial rate of increasing the offset is greater than the initial rate of increasing the pulse amplitude, so that the minimum amplitude envelope does not drop below 0V.

[0106] In this example, bias 262 can be modulated to generate a biased oscillation of 5 to 20 Hz over a 60 ms pulse width, such as a 16 Hz oscillation as shown. By controlling the rate of increase of bias 262 and the rate of increase of the pulse signal amplitude, the minimum amplitude envelope 264 remains positive in polarity and does not become negative. In the example shown, the pulse width 252 is 60 ms, thus allowing for a relatively low rate of change of bias 262 over a relatively long pulse width 252. When the pulse signal 250 reaches the maximum peak-to-peak amplitude 254, charge accumulation is expected to occur, thereby causing myocardial capture.

[0107] In other instances, depending on the rate at which the bias offset is changed and the resulting oscillation frequency of the bias 262, and depending on the rate of amplitude modulation applied by the amplitude modulator 154, the maximum bias offset 258 may (but does not necessarily) be aligned with the maximum pulse amplitude 270 of the high-frequency oscillation, such as... Figure 7 and 8 As shown in [the document]. Although in [the document] Figure 7 and 8 The diagram shows only one oscillation from the minimum offset to the maximum offset and back to the minimum offset, but the number of oscillations for the offset between the minimum and maximum offsets can be one, two, three, four, or other chosen number of oscillations. An oscillation frequency of offset 262 that differs from the amplitude modulation rate can cause a different number of peaks in the maximum amplitude envelope 260 than the number of peaks in the minimum amplitude envelope 264. Figure 8 (Only one in the middle). Therefore, the maximum amplitude envelope 260 and the minimum amplitude envelope 264 of the pulse signal 250 can be different from each other in the bias-modulated pulse signal, such as Figure 7 and 8 As illustrated in the example. This difference facilitates charge accumulation during pulse signals of 200 or 250 to achieve myocardial capture during pulse width 252, while high-frequency oscillations are used to reduce patient pain and the sensation of pulse signal delivery.

[0108] The modulation of the bias generated by the low-frequency bias generator 156 in Figure 7 and 8 In the example shown, it is approximately sinusoidal. In other examples, the low-frequency bias generator 156 can modulate the bias of the high-frequency pulse signal according to other linear or nonlinear rates of change, which can be skewed, sawtooth, or other shapes, but occur at a rate of change different from the modulation of the pulse amplitude, such that charge accumulation occurs when the pulse signal reaches the maximum pulse amplitude set to capture the myocardium. For example, the low-frequency bias generator 156 can frequently increase the offset every 1 ms to ramp up the offset to the maximum offset, maintain the offset at the maximum offset in a predetermined portion of the pulse width, and then adjust the offset down to the minimum offset to produce an approximately square waveform of the bias.

[0109] Figure 9 This is a flowchart 300 of a method for generating therapeutic electrical stimulation pulses by a medical device, based on an example. At box 302, the stimulation interval expires. The stimulation interval can be determined by… Figure 3 The timing circuit 90 of the control circuit 80 shown in the diagram sets the pacing interval. In other medical applications (such as nerve or muscle stimulation applications), the pulse interval may expire at box 302, as controlled by the processor or timing circuitry of the medical device. The pulse interval can be set to control the rate at which nerve stimulation is applied to induce contraction of muscles (such as skeletal muscle, diaphragm, or gastrointestinal smooth muscle). Pulse width timer (e.g.) Figure 6 The pulse width timer 164 begins timing the electrical stimulation pulse width at block 304 and can provide timing signals to the high-frequency modulator 152, amplitude modulator 154, low-frequency bias generator 156, and / or output circuitry 158 of the treatment circuitry 84. In cardiac pacing applications, the pulse width is the cardiac pacing pulse width, and as an example, its duration can be less than 1 ms or up to 60 ms, without being intended to limit it. The pacing pulse width can be 5 ms to 20 ms in some instances, and 10 ms in one instance. In other therapeutic electrical stimulation applications, the pulse width timer is set to the pulse width or duration of the electrical stimulation pulse signal, which can be within the range of the examples given above or longer or shorter than the examples given above, depending on the energy required to depolarize the target tissue and achieve the desired response (e.g., activation or contraction of a nerve or muscle), and on the duration of the high-frequency portion of the pulse signal required to reduce pain or sensation induced by the exogenous stimulus.

[0110] Figure 6The signal source 150 of the treatment delivery circuit 84 initiates a pulse signal at block 304 when the pulse width timer 164 is activated. Modulator 151 modulates the pulse signal initiated at a selected high frequency (e.g., 1 to 10 kHz). The pulse signal can be initiated with 0 pulse amplitude or with another selected starting pulse amplitude, which can be the maximum pulse amplitude. During the pulse width, at block 306, the treatment delivery circuit 84 can downmodulate the high-frequency oscillation of the pulse signal from the starting frequency to a minimum frequency and upmodulate it back to the ending frequency, according to any of the examples given above. In one example, high-frequency modulator 152 downmodulates the frequency from 2.5 kHz or 5 kHz to 0 Hz and upmodulates it back to 2.5 kHz or 5 kHz. In other examples, at block 310, high-frequency modulator 152 maintains a fixed high frequency throughout the pulse width, and low-frequency bias generator 156 modulates the bias to produce a low-frequency oscillation of bias offset, such as 500 Hz or less. At block 308, amplitude modulator 154 can modulate the amplitude of the pulse signal over the pulse width according to any of the examples given above. In other examples, the amplitude of the pulse signal is fixed during the pulse width (although some amplitude attenuation may occur over the pulse width, for example, depending on the RC time constant of the pacing output circuit and the pacing electrode impedance).

[0111] Modulations performed in blocks 306, 308, and 310 are used to generate charge accumulation, which causes current to flow through body tissue to capture and depolarize the target tissue. In some instances, the therapeutic delivery circuit 84 modulates only the high-frequency oscillation of the pulse signal at block 306 (and optionally modulates the amplitude at block 308), or only modulates the low-frequency bias at block 310 to generate accumulated charge to induce depolarization of the target tissue. In other instances, both the oscillation frequency and the bias of the pulse signal are modulated to generate a modulated high-frequency electrical stimulation pulse signal.

[0112] When the pulse width timer expires, the treatment delivery circuit 84 terminates the therapeutic electrical stimulation pulse at block 312. The control circuit 80 can then begin the next stimulation interval (e.g., a pacing interval) at block 314. During the stimulation interval, the charging circuit (e.g., ...) Figure 6 The included pulse signal source 150 can charge a holding capacitor or one or more other charge storage devices at block 316 to the voltage required to generate the desired maximum pulse amplitude during the next electrical stimulation pulse signal. In other instances, a battery or other medical device power source can be directly connected to the voltage or current regulator of the treatment delivery circuit 84 to generate the pulse signal, without requiring charging of the storage device between electrical stimulation pulses at block 316.

[0113] In some instances, the type of modulation (e.g., high-frequency modulation between the maximum and minimum frequencies of oscillation within the pulse signal or low-frequency modulation of the bias) can be selected and programmed based on patient response. Different control parameters include, but are not limited to, starting high frequency, ending high frequency, maximum oscillation frequency, minimum oscillation frequency, starting pulse amplitude, ending pulse amplitude, maximum pulse amplitude, pulse signal envelope or shape (determined by the pulse amplitude change rate and pulse amplitude control), total pulse width, bias oscillation frequency, maximum and minimum bias offset, bias change rate, duration for which the bias is kept constant at a specified offset, or any combination of these modulation control parameters that can be adjusted to determine patient-tailored parameter values ​​or combinations of parameter values ​​that achieve target tissue capture and depolarization while minimizing patient sensation and / or discomfort caused by the electrical stimulation pulses. In some instances, these various control parameters can be user-programmable via interaction with external device 40, allowing selection and control of any combination of high-frequency modulation and / or low-frequency bias modulation, with or without pulse amplitude modulation, based on default or programmable control parameters.

[0114] Figure 10 This is a diagram of a modulated high-frequency pulse signal 400 generated by a treatment delivery circuit 84 according to another example. In this example, as the pulse amplitude of the high-frequency oscillation increases from a minimum pulse amplitude to a maximum pulse amplitude 404, the high frequency of the pulse signal oscillation decreases from a maximum starting frequency to a minimum frequency over a modulation interval 406. At the end of modulation interval 406 and the beginning of the next modulation interval 408, the pulse amplitude decreases to a minimum value (0 volts in this example), and the frequency increases stepwise from the minimum frequency to the maximum frequency. In this example, the high-amplitude low-frequency portion 410 during modulation interval 406 can capture myocardium (or other target tissue) to induce an evoked response (stimulus-induced depolarization). When the pulse amplitude increases to the maximum pulse amplitude 404, the frequency of the pulse signal oscillation can decrease again over the next modulation interval 408. At the end of modulation interval 408, the next high-amplitude low-frequency portion 412 can also capture myocardium (or other target tissue) that induces the next evoked response. In this example, the bias 416 can be kept constant by the treatment delivery circuit 84. However, in other instances, the low-frequency bias generator 156 may modulate the bias 416 according to any of the examples given above to facilitate charge accumulation during each modulation interval 406. For example, the bias 416 may be adjusted to achieve maximum offset during the low-frequency amplitude portions 410 and 412 of each modulation interval 406 and 408, respectively.

[0115] In this example, the modulation intervals 406 and 408 that determine the rate at which the low-frequency, high-amplitude capture portions 410 and 412 occur may correspond to electrical stimulation rate intervals. For example, according to a pacing therapy protocol, modulation intervals 406 and 408 may be lower pacing rate intervals, anti-tachycardia pacing intervals, or other pacing intervals set by the timing circuit 90 of the control circuit 80. Modulation intervals 406 and 408 may be continuously repeated with zero millisecond delay between the end of one interval 406 and the beginning of the next interval 408, such that a continuously modulated signal is delivered via the selected stimulation electrode pair, wherein the oscillation frequency is down-modulated to a minimum frequency at a rate corresponding to the pacing (or other stimulation) rate. Modulation intervals 406 and 408 may be adjusted to change the stimulation rate. When modulation intervals 406 and 408 are changed to, for example, adjust the pacing rate, the rate at which the oscillation frequency is reduced from the initial maximum frequency to the ending minimum frequency and the rate at which the pulse amplitude is increased from the minimum to the maximum pulse amplitude can be adjusted accordingly, such that the low-frequency high-amplitude portions 410 and 412 of modulation intervals 406 and 408 are defined by the minimum frequency and maximum amplitude required to achieve capture at the desired stimulation rate. In this example, the low-frequency high-amplitude portions 410 and 412 are the terminal portions of each modulation interval 406 and 408. However, in other examples, the low-frequency high-amplitude portions 410 and 412 may occur earlier during modulation intervals 406 and 408, such that they occur at therapeutic stimulation rate intervals spaced apart from each other.

[0116] In other instances, the modulated high-frequency signal 400 may correspond to a single composite electrical stimulation pulse, wherein the charge generated by both the high-amplitude low-frequency portions 410 and 412 of the pulse signal 400 accumulates within a sufficiently short time interval, such that the two high-amplitude low-frequency portions 410 and 412 together cause capture of the myocardium (or other target tissue). In this case, the modulation intervals 406 and 408 are set such that the time interval 414 between the high-amplitude low-frequency portions 410 and 412 is sufficiently small, for example, less than 1 ms, to generate a sufficient net accumulated charge over the pulse width 402 to capture the target tissue. The total pulse width 402 comprising two (or more) high-amplitude low-frequency portions 410 and 412 may correspond to a single electrical stimulation pulse that generates a single depolarization of the target tissue (e.g., single myocardial depolarization).

[0117] Figure 11This is a flowchart 500 of a method for controlling cardiac electrical stimulation therapy performed by a medical device according to one example. At block 502, a modulated high-frequency pulse signal, which may correspond to any of the modulated pulse signals described herein, is delivered according to a treatment delivery protocol (e.g., upon expiration of a specified pacing interval). As described above, the signal may be a pacing pulse delivered to treat tachycardia, bradycardia, cardiac arrest, or as part of any other pacing protocol that includes, for example, pacing to induce tachyarrhythmias. At block 504, control circuitry 80 determines whether the modulated pulse signal has captured myocardium. In some examples, capture is detected by control circuitry 80 based on a sensed induced cardiac event (e.g., an R-wave sensed by sensing circuitry 86) or by detecting an induced cardiac event signal from a digitized cardiac electrical signal received by control circuitry 80 from sensing circuitry 86. Capture from the cardiac electrical signal may be detected by control circuitry 80 based on waveform morphology or other signal characteristic analysis. When capture is detected, it is not necessary to adjust the modulation control parameters used by treatment delivery circuitry 84 when generating the pulse signal. The treatment delivery circuit 84 can continue to generate pulse signals at block 502 based on the current modulation control parameters of the control pulse amplitude, frequency, bias, pulse width and other pulse characteristics.

[0118] When the control circuit 80 does not detect a capture at block 504, the control circuit 80 may optionally control the treatment delivery circuit 84 at block 508 to generate a backup pacing pulse to prevent cardiac arrest. For example, the control circuit 80 may control the treatment delivery circuit 84 to generate a modulated high-frequency signal with an increased pulse amplitude. The pulse amplitude may be set to a maximum value expected to be well above the capture threshold to ensure a highly deterministic pacing capture. In other instances, the control circuit 80 may control the treatment delivery circuit 84 to generate a standard high-amplitude pacing pulse (which is not a high-frequency oscillating signal) intended to capture the myocardium. In this case, the patient may experience sensation or discomfort due to the standard high-amplitude pacing pulse. However, occasional discomfort may be necessary to avoid arrhythmias or other symptoms.

[0119] At block 510, control circuitry 80 may adjust one or more modulation control parameters in response to a capture loss (no capture detected) detected at block 504. For example, control circuitry 80 may increase the maximum pulse amplitude or the rate of pulse amplitude increase, enable bias modulation, increase the maximum bias offset, decrease the minimum frequency reached at maximum amplitude, increase the rate of oscillation frequency reduction, increase the pulse width, or any combination thereof. In some instances, the adjustment of modulation control parameters at block 510 may be combined with adjustments to modulation parameters to increase the likelihood of cardiac capture, and said adjustment may also decrease the likelihood of pain or sensation caused by the adjusted pulse signal. For example, if the maximum pulse amplitude increases, then the maximum frequency and / or shape of the maximum amplitude envelope of the pulse signal may be adjusted (e.g., by adjusting the rate of pulse amplitude increase or decrease and / or increasing the duration of the first portion of the frequency-reduced pulse width) to promote sensory and / or muscular nerve blockade prior to the capture portion of the modulated pulse signal. After adjusting the modulation control parameters at block 510, therapeutic delivery circuitry 84 may generate the next modulated pulse signal at block 502 according to the adjusted modulation control parameters.

[0120] In some instances, control circuitry 80 may be configured to detect pain notification at block 506. For example, a patient or caregiver may use external device 40 to transmit a signal to ICD 14 indicating that the patient is experiencing pain or a sensation of pain as a delivered pacing pulse signal. Telemetry circuitry 88 may transmit the pain notification signal to control circuitry 80. In some instances, control circuitry 80 may include a piezoelectric sensor or other device that responds to a tap of the finger on ICD 14 as a signal of pain or a sensation of pain as a delivered pulse signal. As long as pain notification is not received or detected by control circuitry 80 (the "No" branch of block 506), treatment delivery circuitry 84 may continue to generate a modulated high-frequency pulse signal at block 502 according to the current modulation control parameters. When control circuitry 80 receives a pain notification signal at block 506, control circuitry 80 may adjust the modulation control parameters of block 510, regardless of the capture detection that occurs at block 504.

[0121] At block 510, control circuitry 80 can increase or decrease the maximum frequency of the modulated pulse signal, adjust amplitude modulation to increase the amplitude of one or more high-frequency portions of the pulse signal, and / or decrease the maximum amplitude of one or more low-frequency portions of the pulse signal. In some instances, control circuitry 80 can adjust modulation control parameters at block 510 to promote a reduction in pain or sensation and to promote capture at the adjusted modulation control parameters. For example, if reducing the maximum pulse amplitude reduces the likelihood of pain or sensation, control circuitry 80 can add bias modulation, increase the maximum offset of the bias modulation, or the number of bias modulation oscillations, and / or decrease the minimum frequency of frequency modulation that matches the maximum pulse amplitude to increase charge accumulation during the high-amplitude portion of the pulse signal to promote capture. After adjusting the modulation control parameters, treatment delivery circuitry 84 can generate the next modulated pulse signal at block 502 according to the adjusted parameters.

[0122] exist Figure 11 In one example, control circuit 80 is configured to adjust modulation control parameters in response to both capture loss detection and pain notification detection. It should be understood that in other examples, control circuit 80 may be configured to detect capture and adjust modulation control parameters to increase the likelihood of capture in response to capture loss detection, without being configured to detect pain notification. In other examples, control circuit 80 may be configured to detect pain notification and adjust modulation control parameters to reduce the likelihood of pain or sensation caused by the delivery of modulated high-frequency pulse signals, without necessarily being configured to detect capture. In each of these examples, it should be understood that modulation adjustment may be limited to a predetermined range of available settings to minimize the likelihood of capture loss and / or increased pain or sensation.

[0123] It should be understood that, depending on the instance, certain actions or events in any of the methods described herein may be performed in a different order, added, combined, or omitted entirely (e.g., practicing the methods does not require all of the described actions or events). Furthermore, in some instances, actions or events may be performed simultaneously rather than sequentially, for example, through multithreaded processing, interrupt handling, or multiple processors. Moreover, although some aspects of this disclosure are described for clarity as being performed by a single circuit or unit, it should be understood that the techniques of this disclosure may be performed by a combination of units or circuits associated with, for example, a medical device.

[0124] In one or more instances, the described function may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the function may be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. The computer-readable medium may include a computer-readable storage medium, which corresponds to a tangible medium, such as a data storage medium (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and is accessible by a computer).

[0125] The instructions can be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPLAs), or other equivalent integrated circuits or discrete logic circuits. Therefore, the term "processor" as used herein can refer to any of the foregoing structures or any other structures suitable for implementing the techniques described herein. Furthermore, the techniques can be fully implemented in one or more circuit or logic elements.

[0126] Therefore, specific examples have been presented in the foregoing description. It should be understood that the various aspects disclosed herein can be combined in different combinations rather than the specific combinations shown in the accompanying drawings. It should be understood that various modifications can be made to the mentioned examples without departing from the scope of this disclosure and the appended claims and examples.

[0127] Example 1. A method for delivering electrical stimulation therapy, comprising: generating an electrical stimulation pulse signal having a pulse width; modulating at least one of the following: an oscillation frequency of the electrical stimulation pulse signal during the pulse width between a minimum frequency and a maximum frequency greater than the minimum frequency; or a bias of the electrical stimulation pulse signal during the pulse width between a minimum offset and a maximum offset greater than the minimum offset; and delivering the modulated electrical stimulation pulse signal via a stimulating electrode.

[0128] Example 2. According to the method of Example 1, wherein modulating the oscillation frequency includes reducing the oscillation frequency from an initial maximum frequency to a minimum frequency over a first portion of the pulse width.

[0129] Example 3. According to the method of Example 2, wherein modulating the oscillation frequency includes increasing the oscillation frequency from the minimum frequency on a second portion of the pulse width after the first portion of the pulse width.

[0130] Example 4. The method according to any one of Examples 1 to 3 further includes modulating the amplitude of the oscillation of the electrical stimulation pulse signal between a minimum amplitude and a maximum amplitude during the pulse width.

[0131] Example 5. The method according to Example 4, wherein modulating the oscillation frequency includes modulating the electrical stimulation pulse signal to the minimum frequency at a time corresponding to the maximum amplitude during the pulse width.

[0132] Example 6. The method according to Example 5 further includes modulating the electrical stimulation pulse signal to the minimum frequency at a plurality of times during the pulse width, each of the plurality of times of the minimum frequency corresponding to the time of the maximum amplitude of the electrical stimulation pulse signal.

[0133] Example 7. The method according to any one of Examples 1 to 6 further includes: initiating the electrical stimulation pulse signal when the previous pulse signal expires; and modulating the electrical stimulation pulse signal to the minimum frequency at a time corresponding to the maximum amplitude of the electrical stimulation pulse signal during the pulse width, wherein the time corresponding to the maximum amplitude of the electrical stimulation pulse signal during the pulse width is the cardiac pacing rate interval from the time corresponding to the maximum amplitude and minimum frequency of the previous pulse signal.

[0134] Example 8. The method according to any one of Examples 1 to 7 further includes modulating the bias to the maximum offset at a time corresponding to the maximum amplitude of the oscillation of the electrical stimulation pulse signal during the pulse width.

[0135] Example 9. The method according to any one of Examples 1 to 8 further includes modulating the bias between a minimum offset and a maximum offset, the maximum offset being equal to or greater than the maximum amplitude of the oscillation of the pulse signal.

[0136] Example 10. The method according to any one of Examples 1 to 9 further includes: setting a cardiac pacing interval; detecting the expiration of the cardiac pacing interval; and generating the electrical stimulation pulse signal in response to the expiration of the cardiac pacing interval.

[0137] Example 11. The method according to any one of Examples 1 to 10 further includes: sensing a cardiac signal; detecting a tachyarrhythmia based on the cardiac signal; and generating the electrical stimulation pulse signal in response to detecting the tachyarrhythmia.

[0138] Example 12. The method according to any one of Examples 1 to 11 further includes: sensing a cardiac signal; detecting a capture loss based on the sensed cardiac signal after the electrical stimulation pulse signal; and adjusting modulation control parameters used by the modulator in response to detecting a capture loss.

[0139] Example 13. The method according to any one of Examples 1 to 12 further includes: detecting a pain notification signal; and adjusting modulation control parameters used by the modulator in response to detecting the pain notification signal.

[0140] Example 14. The method according to any one of Examples 12 to 13, wherein adjusting the modulation control parameters includes adjusting at least one of the following: the maximum frequency of the oscillation, the minimum frequency of the oscillation, the maximum amplitude of the oscillation, the rate of decreasing the oscillation frequency, the rate of increasing the oscillation frequency, the rate of increasing the amplitude of the oscillation, the rate of decreasing the amplitude of the oscillation, the maximum offset of the bias, the rate of increasing the bias, the rate of decreasing the bias, and the time interval of zero offset of the bias.

[0141] Example 15. A non-transitory computer-readable medium comprising a set of instructions, which, when executed by control circuitry of a medical device, cause the medical device to deliver electrical stimulation therapy by: generating an electrical stimulation pulse signal having a pulse width; and modulating at least one of: an oscillation frequency of the electrical stimulation pulse signal between a minimum frequency and a maximum frequency greater than the minimum frequency during the pulse width; and a bias of the electrical stimulation pulse signal between a minimum offset and a maximum offset greater than the minimum offset during the pulse width.

Claims

1. A medical device having a therapeutic delivery circuit, comprising: The signal source is configured to generate an electrical stimulation pulse signal with a pulse width; A modulator configured to modulate the electrical stimulation pulse signal by at least one of the following operations: During the pulse width, the oscillation frequency of the electrical stimulation pulse signal is modulated between a minimum frequency and a maximum frequency greater than the minimum frequency; or During the pulse width, the bias of the electrical stimulation pulse signal is modulated between a minimum offset and a maximum offset greater than the minimum offset; and An output circuit is configured to receive modulated electrical stimulation pulse signals, and the output circuit can be connected to a stimulation electrode for delivering the electrical stimulation pulse signals.

2. The medical device of claim 1, wherein the modulator includes a high-frequency modulator configured to reduce the oscillation frequency from an initial maximum frequency to a minimum frequency over a first portion of the pulse width.

3. The medical device of claim 2, wherein the high-frequency modulator is further configured to increase the oscillation frequency from the minimum frequency on a second portion of the pulse width following the first portion of the pulse width.

4. The medical device of claim 1, wherein the modulator further comprises an amplitude modulator configured to modulate the amplitude of the oscillation of the electrical stimulation pulse signal between a minimum amplitude and a maximum amplitude during the pulse width.

5. The medical device of claim 4, wherein the modulator is configured to modulate the electrical stimulation pulse signal to the minimum frequency at a time corresponding to the maximum amplitude during the pulse width.

6. The medical device of claim 5, wherein the modulator is configured to modulate the electrical stimulation pulse signal to the minimum frequency at a plurality of times during the pulse width, each of the plurality of times of the minimum frequency corresponding to the time of the maximum amplitude of the electrical stimulation pulse signal.

7. The medical device according to any one of claims 1 to 6, wherein: The signal source is configured to begin the electrical stimulation pulse signal with the pulse width when the previous pulse signal with the pulse width expires, and The modulator is configured to modulate the electrical stimulation pulse signal to the minimum frequency at a time corresponding to the maximum amplitude of the electrical stimulation pulse signal during the pulse width, wherein the time corresponding to the maximum amplitude of the electrical stimulation pulse signal during the pulse width is the cardiac pacing rate interval from the time corresponding to the maximum amplitude and minimum frequency of the previous pulse signal.

8. The medical device according to any one of claims 1 to 6, wherein the modulator includes a bias generator configured to modulate the bias to a maximum offset at a time corresponding to the maximum amplitude of the oscillation of the electrical stimulation pulse signal during the pulse width.

9. The medical device according to any one of claims 1 to 6, wherein the modulator modulates the bias between a minimum offset and a maximum offset, the maximum offset being equal to or greater than the maximum amplitude of the oscillation of the pulse signal.

10. The medical device according to any one of claims 1 to 6, further comprising: The control circuit is configured as follows: Set the cardiac pacing interval; and Detecting the expiration of the cardiac pacing interval. The treatment delivery circuit is configured to generate the electrical stimulation pulse signal in response to the expiration of the cardiac pacing interval.

11. The medical device according to any one of claims 1 to 6, further comprising: A cardiac sensing circuit, configured to sense cardiac signals; The control circuit is configured to detect rapid arrhythmias based on the cardiac signals. and The treatment delivery circuit is configured to generate the electrical stimulation pulse signal in response to the control circuit detecting the rapid arrhythmia.

12. The medical device according to any one of claims 1 to 6, further comprising: The control circuit is configured to detect one of the following: Based on the loss of capture of the sensed cardiac signal after the pulse signal; or Pain notification signals; and The modulation control parameters used by the modulator are adjusted in response to the detection of capture loss or the pain notification signal.

13. The medical device according to any one of claims 1 to 6, wherein the treatment delivery circuit comprises at least one of the following: A low-voltage therapeutic delivery circuit is used to generate the pulse signal as a cardiac pacing pulse; or A high-voltage therapeutic delivery circuit is used to generate the pulse signal as a cardioversion-defibrillation shock pulse.

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