Heart Device System

Abstract

In some instances, a medical device system delivers one or more anti-tachyarrhythmia shocks (e.g., one or more defibrillation shocks) to the patient's heart in coordination with the patient's breathing. In one instance, a medical device system includes a therapy generation circuit system configured to generate a defibrillation shock. The medical device system also includes a processing circuit system configured to: identify a time when the respiratory volume of the patient's lungs is at about the terminal tidal volume or less; and control the therapy generation circuit system to deliver the defibrillation shock to the patient's heart at the time when the respiratory volume of the patient's lungs is at about the terminal tidal volume or less.

Description

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 716,863, filed on August 9, 2018, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present disclosure relates generally to cardiac device systems, such as implantable cardiac device systems configured to deliver anti-tachyarrhythmia therapy. Background Art

[0003] For patients at risk of tachyarrhythmias such as ventricular fibrillation (VF) and / or non-perfusing ventricular tachycardia (VT), an implantable cardiac device system such as an implantable cardioverter-defibrillator (ICD) system can be used to deliver anti-tachyarrhythmia therapy to the patient's heart. An ICD system can include an electrical housing electrode (sometimes referred to as a can electrode) coupled to one or more electrical leads placed in the heart. If an arrhythmia is sensed, the ICD can send pulses through the electrical leads to shock the heart and restore its normal rhythm. In some instances, an extravascular ICD system has been designed to provide an electric shock to the heart without placing electrical leads in the heart, rather than placing and attaching electrical leads directly in the patient's heart. Summary of the invention

[0004] Various aspects of the present disclosure relate to medical device systems (e.g., ICD systems) that are configured to coordinate the delivery of anti-tachyarrhythmia therapy (e.g., in the form of one or more defibrillation shocks or one or more cardioversion shocks) to a patient with the respiration of the patient's lungs. For example, the ICD system can take the form of an extravascular implantable cardiac device that is configured to determine when one or both lungs of the patient are at approximately terminal tidal volume or less, and then deliver an anti-tachyarrhythmia shock (e.g., one or more defibrillation shocks) to the patient's heart to treat, for example, VF or VT of the heart when the respiration volume of the one or both lungs is at approximately tidal volume or less. For example, the ICD system can coordinate the delivery of one or more defibrillation shocks so that the shocks are delivered substantially coincidentally with approximately the end of exhalation performed by the patient as determined by the ICD system.

[0005] In some instances, timing the delivery of one or more anti-tachyarrhythmia shocks in such a manner in coordination with the respiration and respiratory volume of one or more lungs of the patient can allow defibrillation of the patient's heart at a lower threshold (e.g., compared to one or more anti-tachyarrhythmia shocks delivered when the respiratory volume of one or more lungs is at or near maximum tidal volume), thereby producing less electroporation and / or troponin release. Additionally or alternatively, timing the delivery of one or more defibrillation shocks in such a manner in coordination with the respiration and respiratory volume of one or more lungs of the patient can allow for a relatively higher defibrillation efficacy of a shock having an amount of energy, for example, compared to the efficacy of a defibrillation shock having the same amount of energy but delivered when the respiratory volume of one or more lungs is at or near maximum tidal volume.

[0006] In an example, the present disclosure relates to a method comprising identifying a time when a respiratory volume of a patient's lungs is at approximately a terminal tidal volume or less; and delivering, by a medical device system, an anti-tachyarrhythmia shock to the patient's heart at the time when the respiratory volume of the patient's lungs is at approximately the terminal tidal volume or less.

[0007] In another example, the present disclosure relates to a medical device system comprising: a therapy generation circuit system configured to generate an anti-tachyarrhythmia shock; and a processing circuit system configured to: identify a time when the respiratory volume of a patient's lungs is at approximately a terminal tidal volume or less; and control the therapy generation circuit system to deliver the anti-tachyarrhythmia shock to the heart of the patient at the time when the respiratory volume of the patient's lungs is at approximately the terminal tidal volume or less.

[0008] The present disclosure is intended to provide an overview of the subject matter described in this disclosure. It is not intended to provide an exclusive or exhaustive explanation of the systems, devices, and methods described in detail in the following drawings and descriptions. Additional details of one or more examples are set forth in the following drawings and descriptions. Other features, objects, and advantages will become apparent from the description and drawings and statements provided below. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figures 1A-1C The diagrams are front view, side view, and top view, respectively, showing an example medical device system coupled to a patient.

[0010] Figure 2 is a functional block diagram of an example configuration of electronic components of an example IMD.

[0011] Figure 3 A conceptual diagram showing the respiratory volume of the lungs at various stages.

[0012] Figure 4 is a flow chart illustrating an example technique for coordinating the delivery of one or more defibrillation shocks with a patient's breathing.

[0013] Figure 5 is to show, for example, Figure 4 Conceptual illustration of an example technique for timing the delivery of a defibrillation shock in coordination with a patient's breathing.

[0014] Figure 6 is a flow chart illustrating an example technique for coordinating the delivery of one or more defibrillation shocks with a patient's breathing and the patient's posture.

[0015] Figure 7 is a plot of the defibrillation threshold (DFT) versus various combinations of IMD positioning within the patient and the patient's respiratory phase.

[0016] Figure 8 is another plot of the DFT for various combinations of IMD location within a patient and the patient's breathing phase.

[0017] Fig. 9 Four MRI scans are shown (top) and a corresponding model showing the position of the patient's heart within the patient's body (bottom).

[0018] Fig.10 are plots of EV ICD cardiac signals for four patient postures.

[0019] Fig.11A and 11B is in the supine position during inspiration ( Fig.11A ) and upright posture ( Fig. 11B )'s heart and an MRI image of an EV ICD.

[0020] Fig.12 Graphs showing the variation of DFT with posture and respiration for various modeled patients. DETAILED DESCRIPTION

[0021] Various aspects of the present disclosure relate to methods and systems for delivering anti-tachyarrhythmia therapy to a patient's heart in coordination with the patient's respiratory cycle. As described above, in some instances, the present disclosure relates to an ICD system in the form of an extravascular implantable cardiac device that can be configured to determine the relative respiratory volume of one or more lungs of the patient (e.g., by monitoring the patient's inhalation and exhalation) and deliver one or more defibrillation shocks to the patient's heart to treat, for example, VF or VT of the heart when the respiratory volume of one or more lungs is at about tidal volume or less. In some instances, such coordination may result in withholding delivery of anti-tachyarrhythmia therapy to the patient's heart for a period of time after VF or VT of the heart is detected until the respiratory volume of the patient's lungs is at about tidal volume or less. For example, the ICD system can detect VF or VT of the heart while the patient is nearing the end of inspiration (inhalation of air) during normal, quiet breathing. In such a scenario, the ICD system may withhold delivery of anti-tachyarrhythmia therapy to the patient's heart (e.g., delivery of one or more defibrillation shocks) until the patient's lungs are respiratory volume at approximately tidal volume or less (e.g., at the end of the next exhalation following the previous inhalation).

[0022] In some instances, in addition to the respiratory volume of one or more lungs of the patient, the ICD system can also coordinate the delivery of anti-tachyarrhythmia therapy with the patient's posture. For example, after the ICD system detects VF or VT of the patient's heart, the ICD system can time one or more anti-tachyarrhythmia shocks so that one or more shocks are delivered at a time when the patient's respiratory volume is at about tidal volume or less (e.g., at about the end of exhalation performed by the patient) and the patient adopts a target posture (e.g., when the patient is in a supine position or other lying position compared to an upright / standing position or a reclining position). Such instances can again allow for a lower DFT for a given shock energy and / or more therapeutically effective defibrillation, for example compared to delivering one or more anti-tachyarrhythmia shocks when the patient does not adopt a target posture except that the patient is at about terminal tidal volume or less.

[0023] For ease of description, examples of the present disclosure are described primarily in the context of coordinating the delivery of anti-tachyarrhythmia therapy (e.g., one or more shocks) with the patient's breathing in the form of coordinating the delivery of one or more defibrillation shocks with the patient's breathing. However, examples of anti-tachyarrhythmia therapy are not limited to the delivery of one or more defibrillation shocks. For example, in some examples, the anti-tachyarrhythmia therapy delivered to the patient can take the form of one or more cardioversion shocks to the heart (e.g., to VF or VT of the heart), anti-tachycardia pacing (ATP), post-shock pacing, bradycardia pacing, or other suitable therapies.

[0024] Figures 1A-1C 1 and 1 , which are front view conceptual diagrams, side view conceptual diagrams, and top view conceptual diagrams, respectively, showing an example of a medical device system 10 (also referred to as "system 10") in combination with a patient 14. In the example shown, the medical device system 10 is a cardiovascular implantable cardioverter defibrillator (ICD) system implanted in the patient 14. However, the described systems and techniques may be applicable to other cardiac systems, including pacemaker systems, cardiac resynchronization therapy defibrillator (CRT-D) systems, cardiovertor systems, or combinations thereof. In addition, the system 10 may not be limited to treating human patients. In alternative examples, the system 10 may be implemented in non-human patients (such as primates, dogs, horses, pigs, cattle, sheep, cats, etc.). These other animals may undergo clinical therapies or research therapies that may benefit from the subject matter of the present disclosure.

[0025] The medical device system may include one or more medical devices, leads, external devices, or other components configured for the technology described herein. In the example shown, system 10 includes an implantable medical device (IMD) 12, which may be an ICD. IMD 12 is connected to at least one implantable cardiac defibrillator lead 20. In some instances, two leads or more than two leads are used. IMD 12 may be configured to deliver high-energy cardioversion or defibrillation pulses to the patient's heart 18 when ventricular tachyarrhythmias (e.g., ventricular tachycardia (VT) or ventricular fibrillation (VF)) are detected. Cardioversion shocks would typically be delivered synchronously with the detected R wave when the fibrillation detection criteria are met. Defibrillation shocks would typically be delivered when the fibrillation criteria are met and the R wave cannot be distinguished from the signal sensed by IMD 12.

[0026] IMD 12 may be implanted subcutaneously or submuscularly on the left side above the thorax of patient 14. Lead 20 may be at least partially implanted in the substernal space, such as at a target site between the thorax or sternum 24 and heart 18. In one such configuration, a proximal portion of lead 20 may be configured to extend subcutaneously from IMD 12 toward sternum 24 and a distal portion of lead 20 may be configured to extend superiorly below or beneath sternum 24 in anterior mediastinum 26 ( Figure 1C ). Lead 20 may include one or more bends to configure lead 20 to extend naturally (e.g., in a self-biased manner) in this manner when deployed. In some cases, the target site may be substantially in anterior mediastinum 26. Anterior mediastinum 26 is laterally bounded by pleura 28 ( Figure 1C ), bounded posteriorly by the pericardium 16 ( Figure 1C ), and is bounded anteriorly by the sternum 24. In some cases, the anterior wall of the anterior mediastinum can also be formed by the transverse thoracic muscle and one or more costal cartilages. The anterior mediastinum contains a large amount of loose connective tissue (such as cellulite), some lymphatic vessels, lymph glands, substernal musculature (e.g., transverse pectoral muscles), branches of the internal thoracic artery, and the internal thoracic vein. In one example, the distal portion of the lead 20 extends substantially along the posterior side of the sternum 24 within the loose connective tissue or substernal musculature of the anterior mediastinum.

[0027] The term "substernal space" may refer to the area defined by the lower surface between the sternum 24 and the body cavity, but does not include the pericardium 16. In other words, the area is behind the sternum 24 and in front of the ascending aorta. The substernal space may alternatively be referred to as the term "retrosternal space" or "mediastinum" or "infrasternal", and may include an area referred to as the anterior mediastinum. Although the term substernal space is used throughout this disclosure for ease of description, it should be understood that the term may be interchangeable with any other of the aforementioned terms. Further, in the present disclosure, the term "extrapericardial" space may refer to the area surrounding the outer surface of the heart, but not to the pericardial sac or the area within the pericardial space. The area defined as the extrapericardial space includes the spaces, tissues, bones, or other anatomical features surrounding the perimeter of the pericardium 16 and adjacent to the pericardium.

[0028] In other examples, when implanted, the lead 20 can be implanted at other extravascular locations, such as laterally offset to the left or right side of the sternum 24 or positioned above the sternum 24, or alternatively configured to extend substantially parallel to the sternum 24, or laterally angled to the sternum 24 at the proximal or distal end. Although primarily described in the context of an implantable medical device system including a lead having a distal portion positioned in the substernal space, other lead positions are contemplated. The lead 20 can be at least partially implanted at other intrathoracic locations, such as other non-vascular extrapericardial locations, including spaces, tissues, or other anatomical features surrounding the perimeter of the pericardium 16 or other portions of the heart 18 and adjacent to but not attached to and not above the sternum 24 or the thoracic cavity.

[0029] Lead 20 may include an insulated lead body having a proximal end including connector 30 configured to connect to IMD 12 and a distal portion including one or more electrodes. Lead 20 also includes one or more conductors that form an electrically conductive path within the lead body and interconnect the electrical connector and corresponding ones of the electrodes.

[0030] Lead 20 may include defibrillation electrodes 32A, 32B (individually or collectively, "defibrillation electrodes 32"). In other examples, defibrillation electrodes 32A, 32B may be functionally different segments of a single defibrillation electrode 32, such that both defibrillation electrodes 32 are coupled to the same conductor or are otherwise configured to provide the same electrical stimulation. Although for clarity, defibrillation electrodes 32 are referred to in Figures 1A-1C , but it should be understood that the defibrillation electrode 32 can be other configurations, such as an elongated coil electrode, in other instances. The defibrillation electrode 32 can be positioned on a distal portion of the lead 20, wherein the distal portion of the lead 20 is the portion of the lead 20 that is configured to be implanted while extending along the sternum 24. The lead 20 can be implanted at a target location below or along the sternum such that the therapy carrier between the defibrillation electrode 32 and a housing electrode formed by or on the IMD 12 (or other second electrode of the therapy carrier) substantially spans the ventricle of the heart 18. In one example, the therapy carrier can be considered to be a line extending from a point on the defibrillation electrode 32 (e.g., the center of one of the defibrillation electrodes 32) to a point on the housing electrode of the IMD 12. As such, this can be advantageous for increasing the amount of area over which the defibrillation electrode 32 (and the distal portion of the lead 20 therein) extends across the heart 18. Thus, the lead 20 can be configured to define a region such as Figure 1A The curved distal portion is depicted, which may enable lead 20 to provide relatively more effective pacing, sensing and / or defibrillation to heart 18.

[0031] In some examples, based on the position of defibrillation electrodes 32 and housing electrodes of IMD 12 relative to heart 18, one or more lungs ( Figures 1A-1C 14) can be positioned at least partially in the path of a therapy carrier for delivering one or more defibrillation shocks to heart 18 of patient 14. It has been determined that, in at least some instances, the positioning of one or more lungs of patient 18 may affect the DFT and / or therapeutic efficacy of the delivered defibrillation shocks when one or more defibrillation shocks are delivered. In some instances, depending on the positioning of the defibrillation electrodes on leads 20 and the positioning of IMD 14 relative to heart 18, left lung capacity may be of greater concern than right lung capacity in terms of the effect of respiratory volume on defibrillation therapy. Cranio-caudal positioning of the heart relative to the electrodes and in sync with diaphragm movement due to the heart being located on top of the diaphragm may be of greater concern.

[0032] As described herein, in some instances, one or more lungs of patient 14 may be advantageously positioned to deliver one or more defibrillation shocks to heart 18 of patient 14 when the respiratory volume of one or more lungs is at about end-tidal or less. For example, a lower DFT and / or more therapeutically effective defibrillation therapy may result from delivering one or more defibrillation shocks at a time when one or more lungs of patient 14 are at or near end-tidal volume (e.g., by delivering one or more defibrillation shocks substantially coincident with the end of exhalation performed by patient 14). In this manner, the amount of energy consumed by the device while still providing therapeutically effective defibrillation to patient 14 may be reduced, which may allow for a reduction in the size of the power supply, a reduction in the overall volume of IMD 12, and / or limiting electroporation and / or troponin increases from delivering defibrillation therapy. Both electroporation and troponin release may increase with increasing shock energy. Electroporation and troponin release are associated with tissue damage from very high electric fields near the electrodes. These effects may be particularly pronounced near the electrodes because in order to achieve an adequate electric field on the side of the heart away from the electrodes, the electric field strength at the proximal tissue may be relatively high and the proximal tissue may be overstimulated and possibly damaged. Reducing the shock amplitude may reduce the extent of this damage or, in some cases, eliminate it.

[0033] Lead 20 may also include one or more pacing / sensing electrodes 34A, 34B (individually or collectively, "one or more pacing / sensing electrodes 34") positioned on a distal portion of lead 20. Electrodes 34 are referred to herein as pacing / sensing electrodes because they are generally configured to deliver pacing pulses and / or sense cardiac electrical signals. In some cases, electrodes 34 may provide only pacing functionality, only sensing functionality, or both pacing functionality and sensing functionality. Figure 1A and Figure 1BIn the illustrated example, the pacing / sensing electrodes 34 are separated from each other by the defibrillation electrode 32B. However, in other examples, the pacing / sensing electrodes 34 may all be distal to the defibrillation electrode 32B or all be proximal to the defibrillation electrode 32B. In other examples, the lead 20 may include more or fewer electrodes 32, 34 at different locations on the lead 20. In some examples, the IMD 12 may include one or more electrodes 32, 34 on another lead (not shown). Other lead configurations may be used, such as various electrode arrangements. For example, one or more pacing / sensing electrodes 34 may be placed between two defibrillation electrodes 32, as described above. In one example, a plurality of pacing / sensing electrodes 34 may be placed between two defibrillation electrodes 32. In one example, two defibrillation electrodes 32 may be adjacent (e.g., so that the two defibrillation electrodes 32 are not separated by any pacing / sensing electrode 34 between the two defibrillation electrodes 32). Other arrangements may be used in addition or alternatively.

[0034] Lead 20 may define different sizes and shapes that may be suitable for different purposes (e.g., different patients or different therapies). As discussed above, in some examples, the distal portion of lead 20 may have one or more curved sections. Figure 1A As shown in the example of , the distal portion of lead 20 is a serpentine shape that includes two "C"-shaped curves that together can resemble the Greek letter ε, "ε". Defibrillation electrodes 32 are each carried by one of the two corresponding C-shaped portions of the distal portion 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. In some cases, the pacing / sensing electrode 34 can be substantially aligned with the central axis of the straight proximal portion of the lead 20. In this case, the midpoint of the defibrillation electrode 32 is laterally offset from the pacing / sensing electrode 34. Other examples of cardiovascular external leads that include one or more defibrillation electrodes and one or more pacing and sensing electrodes 34 carried by a curved, serpentine, wavy, or zigzag-shaped distal portion of the lead body 18 can be implemented with the techniques described herein. In some examples, the distal portion of lead 20 can be straight (e.g., straight or nearly straight).

[0035] In some examples, the system 10 may sense electrical signals, such as through one or more sensing vectors comprising a combination of the pacing / sensing electrodes 34 and / or the housing electrodes of the IMD 12. In some examples, the IMD 12 may sense cardiac electrical signals using sensing vectors comprising one or two defibrillation electrodes in the defibrillation electrodes 32 and / or one of the defibrillation electrodes 32 and one of the pacing / sensing electrodes 34 or the housing electrodes of the IMD 12. The sensed electrical intrinsic signals may include electrical signals generated by the myocardium and indicate depolarization and repolarization of the heart 18 at different times during the cardiac cycle. The IMD 12 may be configured to analyze the electrical signals sensed by the one or more sensing vectors to detect tachyarrhythmias, such as ventricular tachycardia or ventricular fibrillation. In response to detecting a tachyarrhythmia, the IMD 12 may begin charging a storage element, such as a bank of one or more capacitors, and while charging, if the tachyarrhythmia is still present, one or more defibrillation pulses are delivered through the defibrillation electrodes 32 and / or the housing electrodes of the lead 20. Additionally or alternatively, IMD 12 may deliver pacing therapy via electrodes 32, 34 and / or housing electrodes of IMD 12. In some examples, the pacing therapy may include anti-tachycardia pacing (ATP).

[0036] System 10 may include external device 22. External device 22 may be a computing device configured to be used in a home, ambulatory, clinic, or hospital environment to communicate with IMD 12 via wireless telemetry. Examples of communication technologies used by IMD 12 and external device 22 include radio frequency (RF) telemetry, which may include an RF link established via Bluetooth, wireless LAN, or Medical Implant Communication Service (MICS). Communication may include one-way communication in which one device is configured to transmit communication messages and the other device is configured to receive those messages. Alternatively or additionally, communication may include two-way communication in which each device is configured to transmit and receive communication messages.

[0037] The external device 22 may include a communication circuit system configured to communicate according to the techniques described above. When the external device 22 is configured as a programmer for the IMD 12, the external device 22 may be used to program commands or operating parameters of the IMD 12 to control the functions of the IMD 12. The external device 22 may be used to communicate with the IMD 12 to retrieve data, such as operational data, physiological data, etc., accumulated in the IMD memory. In this way, the external device 22 may act as a programmer for the IMD 12, an external monitor for the IMD 12, or a consumer device such as a smart phone. The external device 22 may be coupled to a remote patient monitoring system, such as the EM-1000, available from Medtronic plc, of Dublin, Ireland. The user may use external device 22 to program or update treatment parameters that define therapy or perform other activities with respect to IMD 12. The user may be a physician, technician, surgeon, electrophysiologist, or other healthcare professional. In some instances, the user may be patient 14.

[0038] Figure 2 1 is a functional block diagram of an example configuration of electronic components and other components of an example IMD 12. IMD 12 includes processing circuit system 40, sensing circuit system 42, therapy generation circuit system 44, telemetry circuit system 46, power supply 48, memory 50, posture sensor 51 and breathing sensor 53. The electronic components can receive power from power supply 48, which can be a rechargeable or non-rechargeable battery (e.g., a lithium-ion battery). In other embodiments, IMD 12 can include more or fewer electronic components. The described circuit systems and other components can be implemented together on a shared hardware component, or separately as discrete but interoperable hardware or software components. The depiction of different features is intended to highlight different functional aspects, and does not necessarily imply that such circuit systems and other components must be implemented by separate hardware or software components. On the contrary, the functions associated with one or more modules or circuit systems and components can be performed by separate hardware or software components, or integrated in shared or separate hardware or software components.

[0039] Sensing circuitry 42 may be electrically coupled to some or all of electrodes 32 and 34 via conductors of lead 20 and one or more electrical feedthroughs, or to housing electrodes via conductors inside the housing of IMD 12. Sensing circuitry 42 is configured to obtain signals sensed via one or more combinations of electrodes 32 and 34 and housing electrodes of IMD 12 and to process the obtained signals.

[0040] The components of the sensing circuit system 42 may be analog components, digital components, or a combination thereof. The sensing circuit system 42 may, for example, include one or more sensing amplifiers, filters, rectifiers, threshold detectors, analog-to-digital converters (ADCs), etc. The sensing circuit system 42 may convert the sensed signal into a digital form and provide the digital signal to the processing circuit system 40 for processing or analysis. For example, the sensing circuit system 42 may amplify the signal from the sensing electrode and convert the amplified signal into a multi-bit digital signal through the ADC. The sensing circuit system 42 may also compare the processed signal with a threshold value to detect the presence of atrial or ventricular depolarization (e.g., a P wave or an R wave) and indicate the presence of atrial depolarization (e.g., a P wave) or ventricular depolarization (e.g., an R wave) to the processing circuit system 40.

[0041] According to some examples of the present disclosure, processing circuit system 40 may be configured to monitor the respiration of one or both lungs of patient 14 (e.g., the cycle between inspiration and exhalation) to allow processing circuit system 40 to coordinate the delivery of one or more defibrillation shocks to heart 18 of patient 14 with the respiratory cycle of patient 14. Processing circuit system 40 may use, for example, respiration sensor 53 and / or sensing circuit system 42 to monitor respiration of patient 14. For example, sensing circuit system 42 and / or respiration sensor 53 may be employed so that processing circuit system 40 identifies one or more times when the respiratory volume of the patient's lungs is at about the end-tidal volume or less, and IMD 12 may deliver one or more defibrillation shocks during the identified time when the respiratory volume of the patient's lungs is at about the end-tidal volume or less. In some examples, IMD 12 may determine the time when patient 14 is at or near the end of exhalation (e.g., at the end of exhalation or just before or just after the end of exhalation) to identify the time when the respiratory volume of the patient's lungs is at about the end-tidal volume or less. In some instances, processing circuit system 40 may not determine a value or otherwise measure the respiratory volume of the lungs of patient 14, but may instead determine the relative respiratory volume of the lungs by, for example, distinguishing between periods of inspiration and expiration of patient 14 and delivering defibrillation therapy substantially coincident with approximately the end of exhalation performed by patient 14.

[0042] The respiration sensor 53 may include one or more sensors configured to monitor the respiration of the patient 14, such as a microphone configured to detect sounds associated with the respiration of the patient 14, a magnetometer configured to measure changes in the dimensions of the anatomical structure of the chest of the patient 14 during respiration, or a pressure sensor configured to measure changes in the pressure applied to the lead 20 associated with changes in respiration. In some instances, the accelerometer may generate a signal that changes based on respiration (e.g., based on vibrations and / or movements associated with respiration). As an example, the sensing circuit system 42 may include filters, amplifiers, and / or analog-to-digital conversion circuit systems to condition any of these sensed signals for analysis and / or detection of features of the signals by the processing circuit system 40. In any such instance, the processing circuit system 40 may determine the respiration state of the patient 14 based on the signals obtained from the electrodes 32, 34 and the sensor 53, and may identify the time when the respiration volume of one or both lungs of the patient 14 is greater than or less than the terminal tidal volume. IMD 12 may then deliver one or more defibrillation shocks to heart 18 of patient 14 when respiratory volume is at greater than end-tidal volume or less.

[0043] In one example, IMD 12 can be configured to sense and monitor the respiration of one or both lungs of patient 18 by sensing two or more electrodes (e.g., two or more of pacing / sensing electrodes 34 and / or housing electrodes on housing 20) via sensing circuit system 42. In some examples, the respiration of one or both lungs of patient 18 can be monitored using an impedance signal (e.g., transthoracic), where respiration characteristics can be directly observed. For example, the impedance measured between the can electrode and one or more of electrodes 32, 34 is determined by the amount and type of tissue between the electrodes. At the end of exhalation, the impedance rate of the lung tissue decreases as non-conductive air is expelled. Therefore, the impedance measured between the electrodes tends to decrease, for example to allow detection of the end of exhalation based on the monitored impedance.

[0044] Additionally or alternatively, the sensing circuit system 42 can be configured to sense and monitor the respiration of one or both lungs of the patient 18 by analyzing the cardiac EGM signal. For example, the EGM signal can have lower frequency components that can be otherwise filtered out of the EGM signal (e.g., with a DC filter) due to changes in impedance associated with respiration. The components can be analyzed to monitor the respiration of the patient 14. In some instances, the EGM signal amplitude can vary with respiration as the heart moves relative to the electrodes.

[0045] Additionally or alternatively, the sensing circuit system 42 can be configured to sense and monitor the breathing of one or both lungs of the patient 18 by using a breathing sensor 53 in the form of an accelerometer or an acoustic sensor (e.g., a microphone for sensing lung sounds). In some instances, the breathing sensor 53 can be used to detect low-amplitude breathing traces. The output of the breathing sensor 53 in the form of an accelerometer can have a cyclic component that can be used to monitor breathing, generated by the movement of the IMD 12 as it tilts at the implant site and moves with the breathing of the patient 14. A microphone or other acoustic sensor near the lungs can detect breathing sounds in the same manner as a stethoscope. The processing performed on the audio signal can extract the signal from interfering background noise to monitor the breathing of the patient 14.

[0046] Additionally or alternatively, sensing circuit system 42 can be configured to sense and monitor the respiration volume of one or both lungs of patient 18 with a respiration sensor 53 in the form of a magnetometer and / or a pressure sensor. The pressure sensor can be used, for example, to evaluate pressure changes on lead 20 and / or the canister of IMD 12 as an indication of respiration of patient 12. The magnetometer may be sensitive to movement within the earth's magnetic field that occurs with respiration. The pressure sensor within the canister of IMD 12 can be configured to respond to flexing of the canister caused by respiration. The pressure sensor in the canister may also have changes caused by atmospheric pressure but which can be discarded by high pass filtering of the signal.

[0047] like Figure 2 , IMD 14 may optionally include a posture sensor 51. Posture sensor 51 allows IMD 12 to sense a posture assumed by patient 14. In such instances, IMD 14 may be configured to coordinate the delivery of one or more defibrillation shocks with the posture of patient 14, such as such that a defibrillation shock is delivered when patient 14 assumes a particular posture (e.g., a lying down posture or a supine posture) and when the respiratory volume of one or more lungs of patient 14 is at approximately end-tidal or less.

[0048] exist Figure 2 In an example of, the posture sensor 51 may include one or more accelerometers capable of detecting a static orientation or three-dimensional vector (e.g., an x, y, z coordinate vector), such as a three-axis accelerometer. An example accelerometer may include an accelerometer based on a microelectromechanical system (MEMS). In other examples, the posture sensor 51 may alternatively or additionally include one or more gyroscopes, piezoelectric crystals, pressure transducers, or other sensors for sensing the posture of the patient 12. The posture sensor data generated by the posture sensor 51 and the processing circuit system 40 may correspond to a posture taken by the patient 12, such as a lying posture (e.g., including a supine / lying on back posture), an upright / standing posture, or a reclining posture.

[0049] Although posture sensor 51 is described as containing a 3-axis accelerometer, posture sensor 51 may contain multiple single-axis accelerometers, dual-axis accelerometers, 3-axis accelerometers, or some combination thereof. In some instances, the accelerometer or other sensor may be positioned within or on lead 20 (e.g., at the distal tip or at an intermediate location) within IMD 12, positioned within patient 14 at a certain location within a separate implanted sensor, or even worn on another sensor lead on patient 14. For example, one or more microsensors may be implanted within patient 14 to wirelessly transmit posture information to IMD 12. In this way, the patient's posture can be determined from multiple posture sensors placed at various locations on or within the body of patient 14.

[0050] In one example, each of the x, y, and z signals provided by the posture sensor has both a DC component and an AC component. The DC component describes the gravitational force exerted on the sensor and can thereby be used to determine the orientation of the sensor within the earth's gravitational field. Assuming that the orientation of the sensor is relatively fixed relative to the patient, the DC components of the x, y, and z signals can be used to determine the orientation of the patient within the gravitational field, and therefore, assuming that the sensor is properly oriented relative to the patient's body, the DC components can be used to determine the patient's posture.

[0051] Example systems and techniques for detecting the posture of patient 14 using posture sensor 51 may include one or more of the examples described in U.S. Patent No. 8,708,934 to Skelton et al., which is incorporated herein by reference in its entirety.

[0052] exist Figure 2 In the illustrated example of FIG. 1 , both sensing circuitry 42 and posture sensor 51 are enclosed within the housing of IMD 12. In other examples, all or portions of one or both of sensing circuitry 42 and posture sensor 51 may be located on leads coupled to IMD 12 or may be implemented in a remote sensor that wirelessly communicates with IMD 12. In any case, sensing circuitry 42 and posture sensor 51 are electrically or wirelessly coupled to circuitry contained within IMD 12.

[0053] The processing circuit system 40 can process signals from the sensing circuit system 42 to monitor the electrical activity of the heart 18 of the patient 14. The processing circuit system 40 can store the signals obtained by the sensing circuit system 42 and any generated EGM waveforms, marker channel data, or other data derived based on the sensed signals in the memory 50. The processing circuit system 40 can analyze the EGM waveforms and / or marker channel data to detect cardiac events (e.g., tachycardia). In response to detecting a cardiac event, the processing circuit system 40 can control the therapy generation circuit system 44 to deliver a desired therapy to treat the cardiac event, such as a defibrillation shock, a cardioversion shock, ATP, post-shock pacing, or bradycardia pacing.

[0054] The therapy generation circuit system 44 is configured to generate and deliver electrical stimulation therapy to the heart 18. The therapy generation circuit system 44 may include one or more pulse generators, capacitors, and / or other components capable of generating and / or storing energy for delivery as pacing therapy, defibrillation therapy, cardioversion therapy, cardiac resynchronization therapy, other therapies, or a combination of therapies. In some cases, the therapy generation circuit system 44 may include a first group of components configured to provide pacing therapy and a second group of components configured to provide defibrillation therapy. In other cases, the therapy generation circuit system 44 may utilize the same group of components to provide both pacing therapy and defibrillation therapy. In still other cases, the therapy generation circuit system 44 may share some of the defibrillation and pacing therapy components, while using other components only for defibrillation or pacing.

[0055] Processing circuitry 40 may control therapy generation circuitry 44 to deliver generated therapy to heart 18 through one or more combinations of electrodes 32 and 34 and housing electrodes of IMD 12 in accordance with one or more therapy programs that may be stored in memory 50. Processing circuitry 40 controls therapy generation circuitry 44 to generate electrical stimulation therapy having an amplitude, pulse width, timing, frequency, electrode combination, or electrode configuration specified by the selected therapy program.

[0056] In the case of pacing therapy (e.g., ATP, post-shock pacing, and / or bradycardia pacing provided via one or more of electrodes 34 of lead 20), processing circuitry 40 controls therapy generation circuitry 44 to generate and deliver pacing pulses of any of a number of shapes, amplitudes, pulse widths, or other characteristics to capture heart 18. For example, pacing pulses may be monophasic, biphasic, or multiphasic (e.g., more than two phases). When pacing pulses are delivered from the substernal space (e.g., from one or more electrodes 34 substantially within anterior mediastinum 26), the pacing thresholds of heart 18 may depend on a number of factors, including the location, type, size, orientation, and / or spacing of electrodes 28 and 30, the location of IMD 12 relative to electrodes 34, a physical abnormality of heart 18 (e.g., pericardial adhesions or myocardial infarction), or one or more other factors.

[0057] In the case of cardioversion or defibrillation therapy (e.g., a cardioversion or defibrillation shock provided by one or more of the defibrillation electrodes 32A and 32B of the lead 20), the processing circuit system 40 controls the therapy generation circuit system 44 to generate a cardioversion or defibrillation shock having any of a variety of waveform characteristics (including leading edge voltage, slope, energy delivered, pulse phase, etc.). The therapy generation circuit system 44 can, for example, generate a monophasic, biphasic, or multiphasic waveform. Additionally, the therapy generation circuit system 44 can generate a cardioversion or defibrillation waveform with different amounts of energy. As with pacing, delivering a cardioversion or defibrillation shock from the substernal space (e.g., from one or more electrodes 32 substantially within the anterior mediastinum 26) can reduce the amount of energy that needs to be delivered to defibrillate the heart 18. As an example, the therapy generation circuit system 44 can generate and deliver a cardioversion or defibrillation shock having an energy of less than 80 joules (J). As another example, therapy generation circuit system 44 can generate and deliver cardioversion or defibrillation shock with energy less than 65J. As an example, therapy generation circuit system 44 can generate and deliver cardioversion or defibrillation shock with energy less than 60J. In some instances, therapy generation circuit system 44 can generate and deliver cardioversion or defibrillation shock with energy of about 40 to about 50J (e.g., about 40J). In other cases, therapy generation circuit system 44 can generate and deliver cardioversion or defibrillation shock with energy of about 35 to about 60J. In still other cases, therapy generation circuit system 44 can generate and deliver cardioversion or defibrillation shock with energy less than 35J. On the other hand, subcutaneous IMD system generates and delivers cardioversion or defibrillation shock with energy of about 80J. Placing defibrillation lead 20 in the substernal space (e.g., the distal portion is substantially in the anterior mediastinum 26) can cause reduced energy consumption and thereby smaller devices and / or devices with increased lifespan.

[0058] As described herein, in some examples, therapy system 10 (e.g., processing circuitry 40) may be configured to time the delivery of defibrillation therapy (e.g., one or more defibrillation shocks) such that one or more electrical stimulation shocks (one or more pulses) are delivered to heart 18 of patient 14 when the respiratory volume of one or more lungs of patient 14 is at approximately end-tidal volume or less. For example, therapy system 10 may be configured to identify when the respiratory volume of a lung of patient 18 (e.g., the left lung of patient 14) is at approximately end-tidal volume or less, such as by monitoring the respiratory cycle of patient 18 using sensing circuitry 42, and deliver one or more defibrillation shocks to heart 18 using one or more electrodes 32 and the housing electrodes of IMD 12 when the respiratory volume of the patient's lung is at approximately end-tidal volume or less. As described herein, in some instances, controlling the delivery of one or more defibrillation shocks to coincide with, for example, approximately the end of exhalation by the patient or at another time when the respiratory volume of patient 14 is at approximately end-tidal or less can provide a lower DFT and / or more effective defibrillation shocks, for example, compared to delivering one or more defibrillation shocks when the respiratory volume of patient 14 is greater than approximately end-tidal or at or near the end of an inhalation by the patient.

[0059] The therapy generation circuit system 44 can also generate defibrillation waveforms with different slopes. In the case of a biphasic defibrillation waveform, the therapy generation circuit system 44 can use a 65 / 65 slope, a 50 / 50 slope, or other combinations of slopes. In some cases, the slope on each phase of the biphasic or multi-phase waveform can be the same, such as a 65 / 65 slope. However, in other cases, the slope on each phase of the biphasic or multi-phase waveform can be different, such as a slope of 65 on the first phase and a slope of 55 on the second phase. The energy, leading edge voltage, phase, slope, etc. delivered by the example are provided for exemplary purposes only and should not be considered to limit the type of waveform characteristics that can be used to provide substernal defibrillation through the defibrillation electrode 24.

[0060] Telemetry circuitry 46 includes any suitable hardware, firmware, software, or any combination thereof, for communicating with another device, such as a clinician programmer, a patient monitoring device, etc. For example, telemetry circuitry 46 may include appropriate modulation, demodulation, frequency conversion, filtering, and amplifier components that may be located within a connector block of IMD 12 or within the housing IMD 12 for transmitting and receiving data via an antenna.

[0061] The various components of IMD 12 may include any one or more processors, controllers, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or equivalent discrete or integrated circuit systems (including analog circuit systems, digital circuit systems, or logic circuit systems). Processing circuit system 40 may include fixed function circuit systems and / or programmable processing circuit systems. The functions attributed to processing circuit system 40 herein may be embodied in software, firmware, hardware, or any combination thereof.

[0062] Memory 50 may contain computer-readable instructions that, when executed by processing circuitry 40 or other components of IMD 12, cause one or more components of IMD 12 to perform various functions attributed to those components in the present disclosure. Memory 50 may include any volatile, nonvolatile, magnetic, optical, or electronic media, such as random access memory (RAM), read-only memory (ROM), nonvolatile RAM (NVRAM), static nonvolatile RAM (SRAM), electrically erasable programmable ROM (EEPROM), flash memory, or any other nonvolatile computer-readable storage medium.

[0063] Figure 3 is a conceptual diagram illustrating various components of respiratory volume of the lungs of a patient, such as patient 14, over an example time period. The respiratory volume of the lungs may be the amount of air contained within the lungs at a given time. The respiratory volume may depend on the amount of air inhaled (e.g., during normal quiet inspiration 56), exhaled (during normal quiet exhalation 58), and stored within the lungs at a given time.

[0064] like Figure 3 As shown, the breathing cycle of the patient 14 may include an inhalation period 56 followed by an exhalation period 58, such that the respiratory volume of one or more lungs cycles between a maximum tidal volume 60 following the inhalation period 56 and a terminal tidal volume 54 following the exhalation period 58. During inhalation 56, the diaphragm may contract and pull downward, while the muscles between the ribs contract and pull upward. This increases the size of the chest cavity and decreases the pressure inside. As a result, air rushes in and fills the lungs. During exhalation 58, the diaphragm relaxes, and the volume of the chest cavity decreases while the pressure within it increases. As a result, the lungs contract and air is squeezed out.

[0065] like Figure 3As shown, tidal volume can refer to the amount of air that enters the lungs during normal inspiration when the patient is at rest (e.g., as opposed to exercise). For example, if the patient 14 is sitting normally and breathing quietly, the total amount of air inhaled during inspiration can be the tidal volume. The amount of air in the lungs after normal exhalation can be called the terminal tidal volume 54. An example tidal volume for the patient 14 can be approximately 500 milliliters. The inspiratory reserve volume can refer to the amount of excess air that may be inhaled during a deep breath above the tidal volume. For example, if the patient 14 inhales a normal amount at rest, the maximum additional air that exceeds the normal tidal inspiration that the patient 14 can inhale constitutes the inspiratory reserve volume. Conversely, the expiratory reserve volume can refer to the amount of excess air that is exhaled during a forced breath that exceeds the tidal volume. For example, if the patient 14 were to exhale normally and then try to exhale even more until he / she physically could not exhale any more air, the amount exhaled after the terminal tidal volume 54 constitutes the expiratory reserve volume. Residual volume may refer to the amount of air that remains in the lungs after a maximum exhalation. This amount prevents the lungs of the patient 14 from collapsing. Vital capacity may refer to the maximum amount of air that can be exhaled after a deep breath is possible. Total lung capacity may refer to vital capacity plus residual volume and is the total amount of air that the lungs can hold.

[0066] According to examples of the present disclosure, a medical device system (such as system 10 of FIG. 1 ) can be configured to coordinate the delivery of one or more defibrillation shocks to a patient when one or more of the patient's lungs is at approximately end-tidal volume or less. Examples of such respiratory volumes are Figure 3 52, where threshold 52 corresponds to approximately the end-tidal volume. Medical device system 10 may be configured to deliver one or more defibrillation shocks to heart 18 of patient 14 at a point in time when the respiratory volume of patient 14 is at threshold 52 or less (e.g., when VF or VT of heart 18 is detected). As described herein, IMD 12 may be configured to determine when the respiratory volume of one or more lungs of patient 14 is at approximately the end-tidal volume or less, for example, by monitoring the respiration (inspiration and / or expiration) of patient 14.

[0067] In some examples, threshold 52 may be equal to the terminal tidal volume 54 of patient 14. In some examples, threshold 52 may be about 50%, about 40%, about 35%, about 30%, about 25%, about 20%, about 15%, about 10%, about 5%, about 2.5% of the tidal volume of patient 18. In other examples, from a time perspective, threshold 52 may represent the respiratory volume of one or more lungs of patient 14 about 5 seconds, about 4 seconds, about 3 seconds, about 2 seconds, or about 1 second before and / or after the occurrence of the terminal tidal volume 54 of one or more lungs of patient 14. In some examples, threshold 52 may be set to an absolute value of the vital capacity that is higher than the terminal tidal volume of one or more lungs of patient 14. In some instances, threshold 52 may be the respiratory volume of one or more lungs of patient 14 approximately 5 seconds, approximately 3 seconds, approximately 2 seconds, or approximately 1 second after the start of an exhalation period of patient 14 and / or approximately 5 seconds, approximately 3 seconds, approximately 2 seconds, or approximately 1 second after the start of an inhalation period of patient 12.

[0068] In other instances, a particular patient may receive one or more defibrillation shocks timed at any location within the cardiac cycle at the discretion of the clinician, rather than delivering the defibrillation shock at or near terminal tidal expiration. Factors determining timing may be the relative alignment of the electrodes, heart and cans, and / or lung capacity.

[0069] Figure 4 is a flowchart showing an example technique according to some examples of the present disclosure. For ease of description, Figure 4 The example techniques are described as being performed by the medical device system 10 of FIG1 on the patient 14. However, any suitable medical device system may employ the example techniques to deliver defibrillation stimulation therapy to a patient, including any suitable extravascular ICD system.

[0070] like Figure 4 As shown, processing circuitry 40 of IMD 14 may determine that heart 18 of patient 14 is in a state of VF or VT or otherwise requires defibrillation stimulation therapy (62). Processing circuitry 40 may make such a determination using any suitable technique. For example, processing circuitry 40 may use sensing circuitry 42 to sense electrical activity of heart 18 to detect the occurrence of VF or VT, or to sense other electrical activity indicating that defibrillation therapy should be delivered to defibrillate heart 18 of patient 14. Although in Figure 4 In the example of , IMD 12 determines that patient 14 requires defibrillation stimulation therapy when VT or VF of heart 18 is detected, but other scenarios are contemplated in which heart 18 of patient 14 requires defibrillation stimulation therapy.

[0071] In response to detecting VF or VT of heart 18 (62), processing circuitry 40 of IMD 12 determines whether the respiratory volume of one or more lungs (e.g., the left lung or both the right lung and the left lung) of patient 18 is at approximately the end-tidal volume or less (64). IMD 12 may employ any suitable technique that allows identification of a time when the respiratory volume of one or both lungs of patient 14 is at approximately the end-tidal volume or less. For example, as described above, processing circuitry 40 may use sensing circuitry 42 and / or respiratory sensor 53 to monitor the respiratory volume of one or more lungs of patient 14. In some examples, to identify a time when the respiratory volume of one or both lungs of patient 14 is at approximately the end-tidal volume or less, processing circuitry 40 may monitor the respiratory cycle of patient 14 to determine a time when patient 14 is at or near the end of the expiratory phase of the respiratory cycle. The time when patient 14 is at or near the end of the expiratory phase of the respiratory cycle may correspond to a time when one or more lungs of patient 14 is at approximately the end-tidal volume or less. Conversely, processing circuitry 40 may determine that the respiratory volume of patient 14 is not at approximately the end tidal volume or less by determining that the patient is at or near the end of the inspiratory phase of the respiratory cycle.

[0072] If processing circuitry 40 determines that respiratory volume is at approximately end-tidal volume or less (64), processing circuitry 40 may control therapy generation circuitry 44 to deliver one or more defibrillation shocks to heart 18 of patient 14 via one or more of electrodes 32 on lead 20 when respiratory volume of one or more lungs of patient 14 is at approximately end-tidal volume or less (66). The one or more defibrillation shocks may be configured to defibrillate heart 18 by delivering an amount of energy sufficient to terminate an arrhythmia of heart 18. The amount of energy of the one or more defibrillation shocks delivered may be equal to or greater than a defibrillation threshold (also referred to as a DFT) of heart 18 of patient 14.

[0073] In some instances, when it is determined, for example, using respiration sensor 53, that patient 14 is at or near the end of exhalation, processing circuit system 40 determines that the respiratory volume is at approximately end-tidal or less. In some instances, processing circuit system 40 may time the delivery of one or more defibrillation shocks to a set amount of time at the end of exhalation by patient 14. For example, processing circuit system 40 may identify the approximate end of exhalation via respiration sensor 53 and control therapy generation circuit system 44 to deliver one or more defibrillation shocks within (i.e., before or after) approximately 5 seconds, approximately 2.5 seconds, or approximately 1 second of the end of exhalation by patient 14 (e.g., where the respiratory volume is approximately 50% or less of the tidal volume when the one or more shocks are delivered). In some instances, processing circuit system 40 may deliver a defibrillation shock at the end of exhalation or (e.g., in terms of time) within approximately 25% of the entire respiratory cycle before or after the end of exhalation.

[0074] In some examples, processing circuit system 40 may identify the approximate end of inspiration by patient 14 via respiration sensor 53, and then deliver one or more defibrillation shocks to patient 14 within a set amount of time after the approximate end of inspiration, such that the defibrillation shocks may be substantially consistent with the respiratory volume of patient 14 being at approximately the end tidal volume or less. For example, processing circuit system 40 may identify the approximate end of inspiration via respiration sensor 53, and control therapy generation circuit system 44 to deliver one or more defibrillation shocks after approximately 1 second, approximately 2 seconds, approximately 5 seconds, approximately 7 seconds, or approximately 10 seconds of the end of inspiration by patient 14 (e.g., where the shocks are delivered when the tidal volume is approximately 50% or less after the end of inspiration). In some examples, the timing from the end of inspiration to the identification of the end of exhalation may be sensitive to the respiratory rate and this may be affected by the VT or VF of patient 14. Processing circuit system 40 may be configured to compensate by sensing the cyclic signal and dividing by approximately two to estimate the end of exhalation of patient 14. Processing circuitry 40 may time one or more defibrillation shocks offset from the inspiration of patient 14 by a delay of half a cycle (+ / - a quarter cycle).

[0075] Conversely, if processing circuit system 40 determines that the respiratory volume is not at approximately end-tidal or less (64), processing circuit system 40 may control therapy generation circuit system 44 to withhold or otherwise delay the delivery of one or more defibrillation shocks (68). During the delay in the delivery of one or more defibrillation shocks (68), processing circuit system 40 may continue to evaluate the respiratory volume of one or more lungs of patient 14 (e.g., via sensing circuit system 42) to identify when one or more lungs of patient 14 transition to a respiratory volume that is approximately end-tidal or less. In response to determining that the respiratory volume is approximately end-tidal or less, processing circuit system 40 may then control therapy generation circuit system 44 to deliver one or more defibrillation shocks to heart 18 of patient 14 via one or more of electrodes 32 on lead 20 when the respiratory volume of one or more lungs of patient 14 is at approximately end-tidal volume or less (66).

[0076] Although Figure 418, but in some instances, processing circuitry 40 may be unable to determine a respiratory volume (62) of one or more lungs of patient 14 after detecting VF or VT of heart 18 of patient 14, for example due to an error in sensing circuitry 42. In such cases, processing circuitry 40 may be configured to identify that the respiratory volume of patient 14 is undetermined and control therapy generation circuitry to deliver one or more defibrillation shocks to heart 18 of patient 14 without coordinating the one or more defibrillation shocks to coincide with the respiratory volume of the one or more lungs being at approximately end-tidal volume or less.

[0077] Figure 5 is a graph showing the respiratory volume of one or more lungs of the patient 14 Figure 4 5 , processing circuitry 40 may detect VF or VT (62) of heart 18 of patient 14 occurring during inspiration 56 performed by patient 14 at time T(1). Rather than processing circuitry 40 automatically controlling therapy generation circuitry 44 to deliver one or more defibrillation shocks to substantially coincide with detection of VF or VT of heart 18 of patient 14, processing circuitry 40 may, for example, assess the respiratory volume of patient 18 in response to detecting VF or VT of heart 18.

[0078] like Figure 5 As shown, the respiratory volume of one or more lungs of patient 14 may not be at approximately the end tidal volume (represented by threshold 52) until after patient 14 completes an inspiration 56 by patient 14 and at least an initial portion of a subsequent exhalation by patient 14 consistent with processor 40 detecting VF or VT of heart 18 of patient 14. Figure 4 In some embodiments, processing circuitry 40 may delay or otherwise withhold delivery of one or more defibrillation shocks until after patient 14 completes inspiration 56 and at least an initial portion of a subsequent exhalation by patient 14 consistent with detection of VF or VT by processing circuitry 40. In such a scenario, therapy generation circuitry 44, under control of processing circuitry 40, may not deliver one or more defibrillation shocks to patient 14 until time T(2) but not after time T(3), i.e., IMD 12 delivers one or more defibrillation shocks to patient 14 at or during a time when a respiratory volume of one or more lungs of patient 14 is at or below threshold 52. As described herein, threshold 52 indicates that a respiratory volume of one or more lungs of patient 14 is approximately end-tidal volume or less.

[0079] Additionally or alternatively, processing circuitry 40 may control therapy generation circuitry 44 to deliver one or more defibrillation shocks from time T(4) to T(5). For example, rather than delivering one or more defibrillation shocks to patient 14 when respiratory volume is at or below threshold 52 for the first time after VF or VT detection is detected, IMD 14 may not deliver a defibrillation pulse when one or more lungs of patient 14 first fall below threshold 52, but may deliver one or more defibrillation shocks until the next or otherwise subsequent occurrence of respiratory volume of patient 14 being at or below threshold 52.

[0080] In some instances, for example, when the shock delivered from T(2) to T(3) is unsuccessful in defibrillating heart 18, the defibrillation shock may be delivered at some point from T(2) to T(3) and T(4) to T(5). In some instances, for example, after one or more defibrillation shocks coordinated with the breathing of patient 14 are unsuccessful, the defibrillation shock may be delivered without regard to the breathing of patient 14. In some instances, the defibrillation shock may be delivered at some point from T(2) to T(3) and then delivered again at some point from T(3) to T(4).

[0081] Although VF or VT of heart 18 is detected in Figure 5 56 as occurring during inspiration 56 performed by patient 14, but other instances may include detecting VF or VT of heart 18 during expiration performed by patient 14. In this case, if the respiratory volume of one or more lungs of patient 14 is above threshold 52 when VF or VT is detected, IMD 12 may still withhold or otherwise delay delivery of a defibrillation shock. In the event that VT or VF of heart 18 is detected at a time during which the respiratory volume of one or more lungs of patient 14 is at or below threshold 52, IMD 12 may deliver one or more defibrillation shocks before the respiratory volume of one or more lungs rises above threshold 52 (e.g., one or more defibrillation shocks may be delivered approximately coincident with IMD 12 detecting VF or VT of heart 18). In other words, if IMD 12 detects VF or VT of heart 18 from time T(2) to T(3), IMD 12 may deliver one or more defibrillation shocks to heart 18 of patient 14 at or before T(3). Additionally or alternatively, if IMD 12 detects VF or VT of heart 18 from time T(2) to T(3), IMD 12 may wait to deliver one or more defibrillation shocks until some point from time T(4) to T(5) or other subsequent occurrence when patient 14's respiratory volume is at approximately end-tidal volume or less.

[0082] IMD 12 may continuously or periodically monitor the respiration of patient 12, for example to perform Figure 4 In some instances, the processing circuit system 40 continuously monitors the respiratory cycle of the patient 14, for example in combination with monitoring the VT or VF of the heart 18 of the patient 14, to continuously identify one or more times when the respiratory volume of the patient 14 is at about the terminal tidal volume or less. Data indicating the monitored respiration of the patient 14 can be stored by the processing circuit system, for example, in the memory 50. When the VT or VF of the heart 18 is detected, the processing circuit system 40 can access the respiratory data stored in the memory 50 in response to the detection to determine whether the respiratory volume of the patient 14 is at about the terminal tidal volume or less (for example, whether the patient is at or near the end of exhalation). As described above, if the respiratory volume is at about the terminal tidal volume or less, the IMD 12 can deliver one or more defibrillation shocks to the heart 18 of the patient 14, or if the respiratory volume is not at about the terminal tidal volume or less, the IMD can delay the delivery of one or more defibrillation shocks. In other examples, processing circuitry 40 may initiate monitoring of the respiration of patient 14 based on detecting VT or VF of the patient. For example, upon detecting VF or VT of heart 14, IMD 12 may then initiate monitoring of the respiration of patient 14 to identify times when the respiration volume of patient 14 is at approximately end-tidal volume or less.

[0083] Figure 6 is a flow chart illustrating another example technique for coordinating the delivery of defibrillation pulses with the patient's breathing. Figure 6 An example technique similar to Figure 4 1 and similar steps are numbered similarly. Additionally, for ease of description, the example techniques of FIG. 1 are described as being performed on a patient 14 by the medical device system 10 of FIG. 1 . However, any suitable medical device system may employ the example techniques to deliver defibrillation stimulation therapy to a patient, including any suitable extravascular ICD system.

[0084] Except for example Figure 4 Timing the delivery of defibrillation pulses to be coordinated with the respiratory volume of one or more lungs of the patient at about the end tidal volume or less as described in the art, Figure 6 The example technology also coordinates the delivery of defibrillation pulses with the patient's posture. Figure 6 Techniques may include delivering one or more defibrillation shocks to a patient such that delivery coincides with patient 14's respiratory volume being at approximately end-tidal volume or less and while patient 14 assumes a target posture. In the event that processing circuitry 40 detects VF or VT of heart 18 at a time when patient 14 is not in the target posture and / or its respiratory volume is not at approximately end-tidal volume or less, processing circuitry 40 may delay delivery of one or more defibrillation shocks to heart 18 of patient 14 until both conditions are met.

[0085] like Figure 6 As shown, processing circuitry 40 of IMD 14 may determine that heart 18 of patient 14 is in a state of VF or VT or otherwise requires defibrillation therapy (62). In response, processing circuitry 40 may identify whether respiratory volume of one or more lungs of patient 14 is at approximately end-tidal or lower (e.g., by detecting whether patient 14 is at approximately the end of exhalation) (64). If processing circuitry 40 determines that respiratory volume is not at approximately end-tidal or lower (64), processing circuitry 40 may control therapy generation circuitry 44 to withhold or otherwise delay delivery of one or more defibrillation shocks (68).

[0086] Conversely, if processing circuit system 40 determines that the respiratory volume is at about end-tidal or less (64), processing circuit system 40 may determine, via posture sensor 51, whether patient 14 is in the target posture (70). If, in addition to patient 14's respiratory volume being at about end-tidal or less, processing circuit system 40 determines that patient 14 is not in the target posture (70), processing circuit system 40 may control therapy generation circuit system 44 to deliver one or more defibrillation shocks to heart 18 of patient 14 via one or more of electrodes 32 on lead 20 when the respiratory volume of one or more lungs of patient 14 is at about end-tidal volume or less and the patient is in the target posture (74). The one or more defibrillation shocks may be configured to defibrillate heart 18 by delivering an amount of energy sufficient to terminate an arrhythmia of heart 18. The amount of energy of the one or more defibrillation shocks delivered may be equal to or greater than a defibrillation threshold (also referred to as a DFT) of heart 18 of patient 14.

[0087] However, if processing circuitry 40 determines that patient 14 has not assumed the target posture (70), processing circuitry 40 may again control therapy generation circuitry 44 to withhold or otherwise delay delivery of one or more defibrillation shocks (68). Figure 6As shown, such delay in the delivery of one or more defibrillation shocks to the heart 18 of the patient 14 may be affected by the expiration of the timer (72). If the processing circuit system 40 determines that the patient 14 has not assumed the target posture but the timer has expired, the processing circuit system 40 may control the therapy generation circuit system 44 to deliver one or more defibrillation shocks to the heart 18 of the patient 14 through one or more of the electrodes 32 on the lead 20 when the respiratory volume of one or more lungs of the patient 14 is at about the end-tidal volume or less but the patient 14 has not assumed the target posture. The timer may correspond to an amount of time after detecting VT or VF of the heart 18 of the patient 14 that is appropriately delayed without unnecessarily affecting the effectiveness of the therapy regardless of the DFT level. The timer may be used based on the recognition that the patient 14 may not assume the target posture within a reasonable amount of time after detecting VF or VT of the heart 18, for example, if the patient is in a reclining posture or a sitting posture, he / she may not convert to a lying posture, such as a supine posture, within a reasonable amount of time. The timer can be started when VF or VT is detected and can be a pre-programmed value set by a clinician, for example, during a programming session. In some instances, the timer can expire after, for example, about 5 seconds, about 10 seconds, about 15 seconds, about 20 seconds, about 30 seconds, or about 45 seconds, although other values ​​are contemplated. In some cases, the length of the timer can be set by a clinician with a default value provided by the manufacturer of the implantable medical device system.

[0088] Despite Figure 3 , but in some instances, a method similar to that for Figure 6 The timer described in the example techniques of the present invention may be configured to provide a timer for the defibrillation shock so that, for example, delivery of a defibrillation shock is not delayed too long in situations where IMD 12 is unable to identify a respiration of patient 14 after detecting a VT or VT of patient 14. In such situations, the timer may expire after, for example, about 5 seconds, about 10 seconds, about 15 seconds, about 20 seconds, about 30 seconds, or about 45 seconds, although other values ​​are contemplated.

[0089] The target posture of patient 14 can correspond to a posture in which it can be expected that one or more defibrillation shocks will be delivered to patient 14 when patient 14 assumes the posture while the patient's respiratory volume is at approximately end-tidal or less. For example, the combination of patient 14's respiratory volume being at approximately end-tidal or less and the patient adopting the target posture can provide a lower DFT and / or more effective defibrillation shocks compared to delivering one or more defibrillation shocks when patient 14's respiratory volume is at approximately end-tidal or less but the patient is not in the target posture. As an example, a supine posture can achieve a lower DFT relative to an upright posture, and except when patient 14 is at approximately the end of exhalation, adopting a supine posture can result in an even better (e.g., lower) DFT than when patient 14 is in the supine posture when at or near the end of inspiration. Based on Figure 6 In an exemplary embodiment of the present invention, a medical device system having the ability to monitor a patient's posture and breathing during defibrillation may allow for customized defibrillation therapy strategies.

[0090] The target posture can be a preprogrammed value determined on a patient-by-patient basis (e.g., defined by a clinician during a programming session), or can be a predefined value set for all patients. In some instances, the target posture can be a supine posture or other lying posture (e.g., left lying, right lying, front lying), and can be a single posture or a group of multiple postures that can be detected, for example, by the posture sensor 51. In some instances, the target posture can be defined as any posture that is not defined as an undesirable posture. For example, if the patient is taking one or more specific postures that are defined as undesirable (e.g., an upright / standing posture or a reclining posture), the processing circuit system 40 can deny the delivery of a defibrillation shock, and if the patient takes any posture (defined or undefined) that is different from one or more defined undesirable / non-target postures, the processing circuit system can Figure 6 Deliver one or more defibrillation shocks as described.

[0091] Experimental Results

[0092] The present disclosure includes the following discussion that forms a part of the present disclosure, and many details and examples consistent with the present disclosure may be provided. As further described below, one or more studies and experiments are conducted to evaluate one or more aspects of the examples of the present disclosure. However, the present disclosure is not limited to the studies and experiments. Certain aspects of the studies and experiments are further described below. The details and examples discussed below may quantify changes in cardiac signal sensing performed by an extravascular ICD (EV-ICD) such as IMD 12 based on respiration and posture. In such examples, modeling may be similarly used to quantify changes in desired anti-tachyarrhythmia shock parameters in response to changing posture and respiratory states to achieve therapeutic benefits with efficient use of power resources.

[0093] Acute human clinical studies evaluating substernal therapy delivery have been completed and modeling efforts are aimed at predicting chronic electrical performance of EV ICDs. For example, electrophysiological modeling is used to evaluate defibrillation thresholds (DFT) for various can positionings (e.g., cranial versus caudal and anterior versus posterior) and for posture changes and respiration. The following discussion describes an example of the method in the context of sensing for modeling. The model used for defibrillation (and pacing) is the same, except that the electrode is the source of the driving potential rather than the surface of the heart.

[0094] In some instances, EV ICDs use defibrillation leads that are placed outside the heart in the anterior mediastinal space. In this position, the electrodes have some freedom of movement relative to the heart as posture changes. The extent to which this motion affects the electrograms acquired by the electrodes in this novel implant location has not been systematically characterized. Studies have been conducted to quantify changes in the sensed signal due to changes in posture and respiration.

[0095] The first modeling study used a set of MRI scans acquired in various postures and respiratory states to derive anthropometric data that quantified organ motion and shape relative to the supine end-inspiratory posture that represents the implant condition. Detailed data for key anatomical structures, such as the heart and epicardial fat, were obtained from high-resolution ex vivo MRI scans and fused with lower-resolution MRI to create anatomical structures with the appropriate level of detail for accurate simulation. A set of matched computational meshes representing the subject in various postures was created, and the ICD was then "implanted" multiple times in matched positioning across these postures. The epicardial potentials were estimated separately from the surface recordings and mapped to the myocardial surface.

[0096] Fig. 9 1 is a diagram showing four MRI scans during inspiration (INH) of a patient in supine (SUP), left lateral lying (LD), right lateral lying (RD), and upright (UP) positions (upper figure) and a corresponding model showing the position of the patient's heart within the patient (e.g., within the thorax) (lower figure). As shown, the relative positioning of the patient's heart is different for each different position. In one patient, a 20 mm cranial / caudal movement of the heart was observed during tidal breathing and a 60 mm movement was observed during deep breathing.

[0097] The epicardial potential data were manually annotated through a scoring window to identify various types of heart beats, such as normal sinus rhythm (NSR) or ventricular tachycardia (VT). An automated system calculated the cardiac signals of more than 2000 data sets at the electrodes of the ICD, automatically scored them, and stored the results in a database for statistical analysis.

[0098] From the motion analysis of the MRI image data, it was found that the average craniocaudal motion of the apex was 34 mm (range: 3 to 70 mm, N = 9). Fig.10 An example of a prediction signal with a scoring window for four combinations of supine (SUP), upright (UP), inspiration (INH), and expiration (EXH) represented by SUP-INH, SUP-EXH, UP-INH, and UP-EXH is shown in FIG. In this single example, the baseline to peak amplitude in millivolts (mVpk) for the NSR complex ranges from 1.46 to 2.09 mVpk, while the range for the VT complex is 0.75 to 2.22 mVpk. For both complexes, the smallest amplitude is associated with the supine exhalation posture (SUP-EXH) and the largest amplitude is associated with the upright inhalation posture (UP-INH).

[0099] Results from modeling can be used to assess both signal amplitude and postural stability. Results are also used as a guide for testing device and lead implant placement to ensure adequate signal levels in all postures to successfully detect arrhythmias. Inclusion of postural variations is critical to ensure dynamic performance of EV ICDs with external cardiac electrodes.

[0100] Fig.11A and 11B is in the supine position during inspiration ( Fig.11A ) and upright posture ( Fig. 11B ) is a conceptual illustration of an MRI image of a patient's heart 102 and an EV ICD 104. Fig.11A and Fig. 11B The shaded area in both indicates a high current density region after delivery of defibrillation therapy using a defibrillation carrier D1, which includes a housing electrode in combination with at least one lead electrode. As shown, while standing and during inspiration, the heart 102 moves caudally as indicated by the arrows between the images. In some instances, this may cause the defibrillation carrier D1 to become less effective during defibrillation. Thus, in some cases, defibrillation efficacy can be improved by sensing an upright posture and responding to the sensed upright posture, thereby disabling a carrier (e.g., carrier D1), increasing defibrillation energy, or both.

[0101] Fig.12is a graph showing the variation of DFT with posture and respiration for various modeled patients. The stability graph compares the defibrillation threshold (DFT) for the supine inspiratory condition (X-axis) with the values ​​for all other postures (Y-axis). For some patients (HB-F-004-A and HB-F-004-B), the DFT is stable with respect to posture, while for other patients (HB-M-005-A and HB-M-005-B), the DFT may vary greatly. It is believed that patients with unstable DFT may benefit from a device that increases the shock energy when it senses that the patient is in a posture that has been determined to be problematic.

[0102] Surprisingly, aspects of the modeling work revealed that DFT is affected by the respiratory cycle, with the lowest predicted DFT coinciding with end-tidal exhalation for a given can placement or patient posture. Results from electrophysiological modeling are shown in Figure 7 and 8 middle.

[0103] Figure 7 It is a diagram of DFT for nominal leads and various IMD housing (can-shaped electrode) implant positioning and patient posture in a modeled patient. For modeling, as described above, the IMD housing is usually subcutaneously positioned on the left side of the patient above the chest and the defibrillation electrode is positioned below the sternum. In the figure, the nominal IMD housing implant positioning is marked at approximately the horizontal center, wherein the modeled positioning moves from the nominal positioning to the tail in increments of 20 mm when the figure moves to the right and moves from the nominal positioning to the cranial in increments of 20 mm when the figure moves to the left. For each implant position, DFT should be determined for the modeled conditions of the patient in a supine position and approximately the end of inspiration ("Sup-In"), in a supine position and approximately the end of exhalation ("Sup-Ex"), in an upright / standing position and approximately the end of inspiration ("Up-In"), and in an upright / standing position and approximately the end of exhalation ("Up-Ex").

[0104] Based on Figure 7 The results shown in the figure of confirm that: although the nominal positioning is favorable for the Sup-In case in terms of DFT, the Sup-In is relatively unstable relative to the Up-In in terms of DFT variability. Both Sup-In and Up-In are marked in Figure 7 It was also determined that in both cases, the more caudal placement of the IMD housing improved stability with respect to DFT variability, such that the increase in DFT in the Sup-In case was small.

[0105] like Figure 7As shown, for each of the IMD housing positions, the DFT at approximately the end of exhalation in each of the upright / standing and supine positions was generally lower than that in the same position but at approximately the end of inspiration. Further, the DFT for Sup-Ex was lower for most IMD housing positions compared to the other three. For all subjects, the end of exhalation was determined to be the optimal state for delivering a defibrillation shock.

[0106] Figure 8 It is a diagram of DFT for nominal leads and various IMD housing (can-shaped electrodes) implant positioning and patient posture in a modeled patient. For modeling, as described above, the IMD housing is usually subcutaneously positioned on the left side of the patient above the chest and the defibrillation electrode is positioned below the sternum. In the figure, the nominal IMD housing implant positioning is marked to be approximately in the horizontal center, wherein the modeled positioning moves backward from the nominal positioning in increments of 20 mm when the figure moves to the right and moves forward from the nominal positioning in increments of 20 mm when the figure moves to the left. For each implant position, DFT should be determined for the modeled conditions of the patient in a supine position and approximately the end of inspiration ("Sup-In"), in a supine position and approximately the end of exhalation ("Sup-Ex"), in an upright / standing position and approximately the end of inspiration ("Up-In"), and in an upright / standing position and approximately the end of exhalation ("Up-Ex").

[0107] based on Figure 8 The results shown in determine that the nominal IMD housing positioning is favorable for Sup-In in terms of relatively low DFT, but it is the least stable positioning in terms of variability. Figure 8 The results plotted in indicate that placing 20 mm to 40 mm further back from the nominal positioning improves stability in terms of DFT variability.

[0108] Although processing circuitry 40 of IMD 12 is described above as being configured to perform one or more of the steps of the techniques described with reference to FIGS. 1-6 , any of the steps of the techniques described herein may be performed by processing circuitry of other devices. For example, processing circuitry of a remote computer located at a clinician's location or any other suitable implantable or external device or server may be configured to perform one or more of the steps described as being performed by processing circuitry 40 of IMD 12. Such other implantable or external devices may include, for example, an implantable or external monitoring device or any other suitable device.

[0109] Various aspects of the technology may be implemented within one or more processors (including one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic circuitry) embodied in a programmer (e.g., a physician or patient programmer), an electrical stimulator, or other device, as well as any combination of such components. The term "processor" or "processing circuitry" may generally refer to any of the aforementioned logic circuitry, alone or in combination with other logic circuitry or any other equivalent circuitry.

[0110] In one or more instances, the functions described in the present disclosure may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software form, the functions may be stored as one or more instructions or codes on a computer-readable medium, and the functions may be performed by a hardware-based processing unit. The computer-readable medium may include a computer-readable storage medium forming a tangible non-temporary medium. The instructions may be executed by one or more processors (such as one or more DSPs, ASICs, FPGAs, general-purpose microprocessors, or other equivalent integrated or discrete logic circuit systems). Therefore, the term "processor" or "processing circuit system" as used herein may refer to one or more of any of the aforementioned structures or any other structure suitable for implementing the technology described herein.

[0111] In addition, in some aspects, the functions described herein can be arranged in dedicated hardware and / or software modules. Depicting different features as modules or units is intended to highlight different functional aspects, and does not necessarily imply that such modules or units must be implemented by separate hardware or software components. On the contrary, the functions associated with one or more modules or units can be performed by separate hardware or software components, or integrated in shared or separate hardware or software components. Moreover, the technology can be implemented completely in one or more circuits or logic elements. The technology disclosed herein can be implemented in various devices or equipment (comprising an IMD, an external programmer, a combination of an IMD and an external programmer, a collection of integrated circuits (ICs) or ICs and / or a discrete circuit system residing in an IMD and / or an external programmer).

[0112] Various aspects of the disclosure have been described. These and other aspects are within the scope of the following claims and clauses.

[0113] Item 1. A method comprising identifying a time when a patient's lung respiratory volume is at approximately a terminal tidal volume or less; and delivering, via a medical device system, an anti-tachyarrhythmia shock to the patient's heart at the time when the patient's lung respiratory volume is at approximately a terminal tidal volume or less.

[0114] Clause 2. A method according to clause 1, further comprising monitoring the respiration of the patient's lungs during a time period prior to delivering the anti-tachyarrhythmia shock, wherein the time when the patient's lung respiration volume is at approximately the end-tidal volume or less is identified at least in part based on the monitored respiratory cycles of the patient's lungs.

[0115] Clause 3. The method of clause 1 or 2, wherein identifying the time at which the respiratory volume of the patient's lungs is at approximately end-tidal volume or less comprises identifying an approximate end of exhalation of the patient.

[0116] Clause 4. A method according to Clause 3, wherein delivering the anti-tachyarrhythmia shock to the patient's heart at the time when the respiratory volume of the patient's lungs is at approximately the terminal tidal volume or less includes delivering the anti-tachyarrhythmia shock to the patient's heart substantially coincident with the approximate end of the patient's exhalation.

[0117] Clause 5. A method according to any one of clauses 1 to 4, further comprising detecting ventricular fibrillation (VF) or ventricular tachycardia (VT) of the heart of the patient by an implantable medical device, wherein delivering the anti-tachyarrhythmia shock comprises delivering the anti-tachyarrhythmia shock in response to detecting the VF or VT.

[0118] Clause 6. A method according to Clause 5, wherein identifying the time when the respiratory volume of the patient's lungs is at approximately terminal tidal volume or less includes identifying the time when the respiratory volume of the patient's lungs is at terminal tidal volume or less in response to detecting the VF or VT of the patient's heart.

[0119] Clause 7. A method according to Clause 5, wherein detecting the ventricular fibrillation (VF) or the ventricular tachycardia (VT) of the heart of the patient by a medical device comprises: when the respiratory volume of the lungs of the patient is greater than the approximate terminal tidal volume, detecting the ventricular fibrillation (VF) or the ventricular tachycardia (VT) of the heart of the patient by the implantable device.

[0120] Clause 8. The method of clause 5, further comprising determining that the respiratory volume of the patient's lungs is greater than the approximately terminal tidal volume in response to detecting the ventricular fibrillation (VF) or the ventricular tachycardia (VT) of the patient's heart; and delaying delivery of the anti-tachyarrhythmia shock to the patient's heart until the time when the respiratory volume of the patient's lungs is at the approximately terminal tidal volume or less.

[0121] Clause 9. A method according to any one of clauses 1 to 8, further comprising determining that a posture assumed by the patient at the time when the respiratory volume of the patient's lungs is at approximately terminal tidal volume or less is a target posture, wherein delivering the anti-tachyarrhythmia shock to the patient's heart at the time when the respiratory volume of the patient's lungs is at approximately terminal tidal volume or less comprises delivering the anti-tachyarrhythmia shock to the patient's heart at the time when the respiratory volume of the patient's lungs is at approximately terminal tidal volume or less and the patient assumes the target posture.

[0122] Clause 10. A method according to any one of Clauses 1 to 9, further comprising determining that the posture assumed by the patient at the time when the respiratory volume of the patient's lungs is at approximately terminal tidal volume or less is not a target posture, and delaying the delivery of the anti-tachyarrhythmia shock to the patient's heart at the time when the respiratory volume of the patient's lungs is at approximately terminal tidal volume or less in response to determining that the patient's posture is not the target posture.

[0123] Clause 11. The method of any one of clauses 9 and 10, wherein the target posture of the patient is a lying flat posture.

[0124] Clause 12. The method of any one of clauses 9 and 10, wherein the target posture of the patient is a supine posture.

[0125] Clause 13. A method according to any one of clauses 1 to 12, wherein identifying the time when the respiratory volume of the lungs of the patient is at approximately terminal tidal volume or less includes identifying the time when the respiratory volume of the lungs of the patient is at terminal tidal volume or less.

[0126] Clause 14. A method according to any one of Clauses 1 to 12, wherein identifying the time when the respiratory volume of the lungs of the patient is at approximately terminal tidal volume or less includes identifying the time when the respiratory volume of the lungs of the patient is at approximately terminal tidal volume.

[0127] Clause 15. A method according to any one of Clauses 1 to 12, wherein identifying the time when the respiratory volume of the patient's lungs is at approximately terminal tidal volume or less includes identifying the time when the respiratory volume of the patient's lungs is approximately 50% or less of the tidal volume of the patient's lungs.

[0128] Clause 16. A method according to any one of Clauses 1 to 12, wherein identifying the time when the respiratory volume of the patient's lungs is at approximately terminal tidal volume or less includes identifying the time when the respiratory volume of the patient's lungs is within approximately 5 seconds after the end of exhalation of the patient's lungs.

[0129] Clause 17. A method according to any one of clauses 1 to 12, wherein identifying the time when the respiratory volume of the patient's lungs is at approximately terminal tidal volume or less includes identifying the time when the respiratory volume of the patient's lungs is approximately 5 seconds after the end of inspiration of the patient's lungs.

[0130] Clause 18. A method according to any one of clauses 1 to 17, wherein delivering the anti-tachyarrhythmia shock to the patient's heart at the time when the respiratory volume of the patient's lungs is at approximately the terminal tidal volume or less includes delivering the anti-tachyarrhythmia shock to the patient's heart at approximately the end of exhalation of the patient's lungs.

[0131] Clause 19. A method according to any one of clauses 1 to 17, wherein delivering the anti-tachyarrhythmia shock to the patient's heart at the time when the respiratory volume of the patient's lungs is at approximately the terminal tidal volume or less includes delivering the anti-tachyarrhythmia shock to the patient's heart at the end of exhalation of the patient's lungs.

[0132] Clause 20. The method of any one of Clauses 1 to 19, wherein the medical device system comprises an implantable medical device system comprising an implantable medical device.

[0133] Clause 21. The method of Clause 20, wherein the implantable medical device system comprises an extravascular implantable cardiac device system.

[0134] Clause 22. A method according to Clause 20, wherein the extravascular implantable cardiac device system comprises a lead comprising one or more electrodes configured to deliver the anti-tachyarrhythmia shock, wherein the one or more electrodes are at a substernal and extravascular location within the patient's body.

[0135] Clause 23. The method of any one of Clauses 1 to 22, wherein the anti-tachyarrhythmia shock comprises one or more defibrillation shocks.

[0136] Clause 24. The method of any one of Clauses 1 to 22, wherein the anti-tachyarrhythmia shock comprises one or more cardioversion shocks.

[0137] Clause 25. A method comprising determining an approximate end of exhalation by a patient; and delivering, by a medical device system, an anti-tachyarrhythmia shock to a heart of the patient based on the determination substantially coinciding with the approximate end of exhalation by the patient.

[0138] Item 26. A medical device system comprising: a therapy generating circuit system configured to generate an anti-tachyarrhythmia shock; and a processing circuit system configured to: identify a time when the respiratory volume of a patient's lungs is at approximately a terminal tidal volume or less; and control the therapy generating circuit system to deliver the anti-tachyarrhythmia shock to the patient's heart at the time when the respiratory volume of the patient's lungs is at approximately the terminal tidal volume or less.

[0139] Clause 27. The medical device system of clause 26, wherein the medical device system is configured to perform any of the methods of clauses 1 to 25.

[0140] Clause 28. A method comprising any method described herein or any combination of methods described herein.

[0141] Clause 29. A method comprising any combination of the methods described in clauses 1 to 25.

[0142] Clause 30. A system comprising means for performing the method of any one of clauses 1 to 25.

[0143] Clause 31. A non-transitory computer-readable storage medium comprising instructions stored thereon that, when executed by processing circuitry, cause the processing circuitry to perform the method of any one of clauses 1 to 25.

[0144] Clause 32. A method comprising identifying a time when a patient's lung respiratory volume is at approximately a terminal tidal volume or less; and delivering, via a medical device system, anti-tachyarrhythmia therapy to the patient's heart at the time when the patient's lung respiratory volume is at approximately a terminal tidal volume or less.

[0145] Clause 33. A method according to clause 32, wherein delivering the anti-tachyarrhythmia therapy comprises delivering one or more of: one or more defibrillation shocks, one or more cardioversion shocks, anti-tachycardia pacing (ATP), post-shock pacing, or bradycardia pacing.

[0146] Item 34. A system comprising a therapy generating circuit system configured to generate anti-tachyarrhythmia therapy; and a processing circuit system configured to: identify a time when the respiratory volume of a patient's lungs is at approximately a terminal tidal volume or less; and control the therapy generating circuit system to deliver the anti-tachyarrhythmia therapy to the patient's heart at the time when the respiratory volume of the patient's lungs is at approximately a terminal tidal volume or less.

[0147] Clause 35. A system as described in Clause 35, wherein the anti-tachyarrhythmia therapy includes one or more of the following: one or more defibrillation shocks, one or more cardioversion shocks, anti-tachycardia pacing (ATP), post-shock pacing, or bradycardia pacing.

Claims

1. A medical device system, comprising: a therapy generating circuitry configured to generate an anti-tachyarrhythmia shock; as well as processing circuitry configured to: identify a time when a respiratory volume of a patient's lungs is at approximately an end-tidal volume or less; and controlling the therapy generating circuitry to deliver the anti-tachyarrhythmia shock to the patient's heart at the time when the respiratory volume of the patient's lungs is at about the end-tidal volume or less.

2. The system of claim 1 , wherein the processing circuit system is configured to: monitoring respiration of the lungs of the patient during a period prior to delivery of the anti-tachyarrhythmia shock, and The time at which the respiratory volume of the lung of the patient is at the approximately end-tidal volume or less is identified based at least in part on a monitored respiratory cycle of the lung of the patient. 3 . The system of claim 1 , wherein the processing circuitry is configured to identify an approximate end of exhalation of the patient.

4. A system according to claim 3, wherein the processing circuit system is configured to control the therapy generation circuit system to deliver the anti-tachyarrhythmia shock to the heart of the patient substantially in line with the approximate end of the patient's exhalation.

5. The system of any one of claims 1 to 4, wherein the processing circuit system is configured to: detecting ventricular fibrillation (VF) or ventricular tachycardia (VT) in the heart of the patient via an implantable medical device, and The therapy generating circuitry is controlled to deliver the anti-tachyarrhythmia shock in response to detecting the ventricular fibrillation or ventricular tachycardia.

6. A system according to claim 5, wherein the processing circuit system is configured to identify the time when the respiratory volume of the patient's lungs is at about the end-tidal volume or less in response to detecting the ventricular fibrillation or the ventricular tachycardia of the patient's heart.

7. A system according to claim 5, wherein the processing circuit system is configured to: detect the ventricular fibrillation (VF) or the ventricular tachycardia (VT) of the heart of the patient through the implantable medical device when the respiratory volume of the lungs of the patient is greater than the approximately end-tidal volume.

8. The system of claim 5, wherein the processing circuitry is configured to: determining that the respiratory volume of the lungs of the patient is greater than the approximately end-tidal volume in response to detecting the ventricular fibrillation (VF) or the ventricular tachycardia (VT) of the heart of the patient; and The therapy generating circuitry is controlled to delay delivery of the anti-tachyarrhythmia shock to the heart of the patient until the time when the respiratory volume of the lungs of the patient is at the approximately end-tidal volume or less.

9. The system of claim 1 , wherein the processing circuitry is configured to: determining that the posture assumed by the patient at the time when the respiratory volume of the lungs of the patient is at about the end-tidal volume or less is a target posture, and The therapy generating circuitry is controlled to deliver the anti-tachyarrhythmia shock to the heart of the patient at the time when the respiratory volume of the lungs of the patient is at the approximately end-tidal volume or less and the patient assumes the target posture.

10. The system of claim 1, wherein the processing circuitry is configured to: determining that the posture assumed by the patient at the time when the respiratory volume of the lungs of the patient is at the approximately end-tidal volume or less is not a target posture, and controlling the therapy generating circuit system to delay delivery of the anti-tachyarrhythmia shock to the patient's heart at the time when the respiratory volume of the patient's lungs is at approximately the end-tidal volume or less in response to determining that the patient's posture is not the target posture, until the patient assumes the target posture.

11. The system of claim 9 or 10, wherein the target posture of the patient is a lying down posture.

12. The system of claim 9 or 10, wherein the target posture of the patient is a supine posture.

13. The system of any one of claims 1 to 4, wherein identifying the time when the respiratory volume of the lungs of the patient is at about the end-tidal volume or less comprises identifying the time when the respiratory volume of the lungs of the patient is at about the end-tidal volume or less.

14. The system of any one of claims 1 to 4, wherein identifying the time when the respiratory volume of the lungs of the patient is at about the end-tidal volume or less comprises identifying the time when the respiratory volume of the lungs of the patient is at about the end-tidal volume.

15. The system of any one of claims 1 to 4, wherein identifying the time when the respiratory volume of the patient's lungs is at about the end-tidal volume or less comprises identifying the time when the respiratory volume of the patient's lungs is 50% or less of the tidal volume of the patient's lungs.

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