WO2025078897A1

WO2025078897A1 - Medical device communication for controlling a medical device system function

Info

Publication number: WO2025078897A1
Application number: PCT/IB2024/059024
Authority: WO
Inventors: Eric A. Schilling; Kristen J. Cattin; Eric R. Williams; Yanina GRINBERG
Original assignee: Medtronic Inc
Current assignee: Medtronic Inc
Priority date: 2023-10-13
Filing date: 2024-09-17
Publication date: 2025-04-17
Anticipated expiration: 2026-04-13

Abstract

A medical device system includes a first medical device having circuitry configured to perform a medical device system function, a communication circuit, and a control circuit configured to detect a condition for disabling performing the medical device system function by the first circuitry. The control circuit may, in response to detecting the condition, transmit via the communication circuit a communication signal to a second medical device capable of performing the medical device system function. The control circuit may disable the performing of the medical device system function by the circuitry.

Description

MEDICAL DEVICE COMMUNICATION FOR CONTROLLING A MEDICAL DEVICE SYSTEM FUNCTION

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63/590,369, filed October 13, 2023, the entire content of which is incorporated herein by reference.

TECHNICAL FIELD

[0002] The disclosure relates generally to medical devices, systems and methods for performing inter-device communication for controlling a medical device system function.

BACKGROUND

[0003] A wide variety of medical devices for delivering a therapy to and/or monitoring a physiological condition of a patient have been used clinically or proposed for clinical use in patients. Examples include implantable medical devices (IMDs) that deliver therapy to and/or monitor conditions associated with the heart, muscle, nerve, brain, stomach or other tissue. Some therapies include the delivery of electrical stimulation to such tissues. Some IMDs may employ electrodes for the delivery of therapeutic electrical signals to such organs or tissues, electrodes for sensing intrinsic physiological electrical signals within the patient, which may be propagated by such organs or tissue, and/or other sensors for sensing physiological signals of a patient.

[0004] Implantable cardioverter defibrillators (ICDs), for example, may be used to deliver high energy cardioversion or defibrillation (CV/DF) shocks to a patient's heart when ventricular tachyarrhythmia, e.g., tachycardia or fibrillation, is detected. An ICD may detect a tachyarrhythmia based on an analysis of a cardiac electrogram (EGM) or electrocardiogram (ECG) sensed via electrodes, and may deliver anti-tachyarrhythmia shocks, e.g., defibrillation shocks and/or cardioversion shocks, via electrodes. An ICD or an implantable cardiac pacemaker, as another example, may provide cardiac pacing therapy to the heart when the natural pacemaker and/or conduction system of the heart fails to provide synchronized atrial and ventricular contractions at rates and intervals sufficient to sustain healthy patient function. ICDs and cardiac pacemakers may also provide overdrive cardiac pacing, referred to as anti-tachycardia pacing (ATP), to suppress or convert detected tachyarrhythmias in an effort to avoid cardioversion/defibrillation shocks. [0005] In some situations, two or more medical devices can be implanted within and/or worn by a single patient. Each of the two or more medical devices may operate individually to perform a monitoring function and/or deliver a therapy to the patient.

SUMMARY

[0006] The techniques of this disclosure generally relate to techniques performed by a medical device system for controlling a medical device system function. A first medical device of the medical device system may be configured to perform a medical device system function and have priority for performing the function. The first medical device may determine a condition for disabling the function in the first medical device. The first medical device may transmit a signal to a second medical device of the medical device system in response to determining the condition for disabling the function in the first medical device. The second medical device may transmit a reply signal to the first medical device. In some examples, the second medical device may assume control of the first medical device function by enabling the medical device function to be performed by the second medical device.

[0007] In one example, the disclosure provides a medical device system comprising a first medical device including circuitry configured to perform a medical device system function, a communication circuit, and a control circuit configured to detect a condition for disabling performing the medical device system function by the circuitry. In response to detecting the condition, transmit via the communication circuit, a communication signal to a second medical device capable of performing the medical device system function and disable the performing of the medical device system function by the circuitry. The first medical device may include a power source configured to provide power to the circuitry, the communication circuit and the control circuit.

[0008] In another example, the disclosure provides a method including performing a medical device system function by a first medical device, detecting a condition for disabling performing the medical device system function by the first medical device and, in response to detecting the condition, transmitting a communication signal to a second medical device capable of performing the medical device system function. The method may include disabling the performing of the medical device system function by the first medical device. [0009] In another example, the disclosure provides a non-transitory computer-readable medium comprising a set of instructions that, when executed by processing circuitry of a medical device system, cause the medical device system to perform a medical device system function by a first medical device of the medical device system, detect a condition for disabling performing the medical device system function by the first medical device and, in response to detecting the condition, transmit a communication signal to a second medical device capable of performing the medical device system function. The instructions may further cause the medical device system to disable the performing of the medical device system function by the first circuitry.

[0010] In another example the disclosure provides a medical device system comprising a first medical device including first circuitry configured to perform a medical device system function, a first communication circuit and a first control circuit. The first control circuit may be configured to detect a condition for disabling performing the medical device system function by the first circuitry and, in response to detecting the condition, transmit via the first communication circuit a communication signal. The first control circuit may be further configured to disable the performing of the medical device system function by the first circuitry. The medical device system further includes the second medical device. The second medical device includes second circuitry configured to perform the medical device system function, a second communication circuit configured to receive the communication signal and a second control circuit configured to enable the second circuitry to perform the medical device system function in response to receiving the communication signal via the second communication circuit.

[0011] The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

[0012] FIG. 1 is a conceptual diagram of a medical device system 1 including at least two medical devices 4 and 6. [0013] FIG. 2 is a conceptual diagram of a medical device system including multiple IMDs in operative contact with a patient and capable of intrabody communication according to one example.

[0014] FIG. 3 is a conceptual diagram of a pacemaker that may be included in the medical device system of FIG. 2 according to some examples.

[0015] FIG. 4 is a conceptual diagram of a medical device that may be included in a medical device system and capable of performing intrabody communication with another member medical device of the medical device system.

[0016] FIG. 5 is a flow chart of a method that may be performed by a medical device system for controlling automatic adjustment of a control parameter by a member medical device of the medical device system according to some examples.

[0017] FIG. 6 is a flow chart of a method for controlling adjustment of a control parameter in conjunction with performing a test algorithm by a medical device according to some examples.

[0018] FIG. 7 is a flow chart of a method for controlling adjustment of a control parameter in conjunction with performing a test algorithm by a medical device according to another example.

[0019] FIG. 8 is a flow chart of a method for controlling an adjustment of a control parameter of a medical device using intrabody communication according to another example.

DETAILED DESCRIPTION

[0020] FIG. 1 is a conceptual diagram of a medical device system 1 including at least two medical devices 4 and 6, which may also be referred to herein as “members” of the medical device system 1. The members of the medical device system are each implanted in or otherwise operatively coupled to a patient for each performing a physiological signal monitoring and/or therapy delivery according to various control parameters and protocols or algorithms that are programmed into the respective medical devices 4 and 6. At least one of the medical devices 4 and/or 6 is configured to automatically adjust a control parameter used by the respective medical device for controlling a medical device function. As used herein, the term “control parameter” refers to a parameter that is used by a medical device to control a medical device function performed by the respective medical device. Multiple control parameters may be used by circuitry of the medical device for controlling a given function. An “adjustable control parameter” is a control parameter that can be adjusted between two or more values to change how the medical device function is performed or to turn on (enable) or turn off (disable) a given medical device function. [0021] The automatic adjustment of a control parameter may be performed during execution of a test protocol that the medical device may be configured to perform on command or on a scheduled or triggered basis. The automatic adjustment of the control parameter may additionally or alternatively be performed based on a result of a measurement or test protocol performed by the medical device. The method for adjusting a control parameter by a medical device system member can include inter-device communication between the medical device, e.g., medical device 4, and a second medical device, e.g., medical device 6, operating in or on the same patient. The inter-device communication may be performed to transmit a request signal 5 to alert the second medical device that the automatic adjustment is to be performed and/or request approval to perform the automatic adjustment. The second medical device may respond to the request by transmitting a reply signal 7, which may be an approval signal or a disapproval signal. In some instances, the disapproval signal may be a delay signal requesting that the first medical device 4 delay adjustment of the control parameter. In other instances, the disapproval signal may be a cancel signal requesting that the first medical device4 cancel the pending adjustment of the control parameter. In some examples, the second medical device 6 may temporarily alter one or more of its own functions to allow the first medical device to perform a test protocol without interference due to functions performed by the second medical device.

[0022] In FIG. 1, two medical devices 4 and 6 are shown, although the techniques disclosed herein may be adapted for operating in a medical device system that include more than two devices operating in or on a patient. While illustrative examples described herein generally refer to a medical device system including two or more IMDs coimplanted in the same patient, in some examples one or both of medical devices 4 and/or 6 may be external or transcutaneous devices, which may be wearable in some instances, which are operatively coupled to the patient for performing one or more patient monitoring and/or therapy delivery functions. Examples of medical devices that may be included in a multi-device system operating in or on a patient include, but are not limited to, cardiac monitors, cardiac pacemakers, implantable cardioverter defibrillators (ICDs), drug pumps, neurostimulators (e.g., spinal cord stimulators, deep brain stimulators, or other electrical stimulation devices configured to deliver electrical pulses to excitable tissue, e.g., nervous tissue or muscle tissue), glucose monitors, blood pressure monitors, blood pumps such as ventricular assist devices, fall detectors, or the like.

[0023] Medical devices 4 and 6 (or medical electrical leads carrying electrodes and/or other sensors extending from medical device 4 or medical device 6) can be operatively positioned for delivering a therapy to a patient and/or monitoring one or more physiological signals from the patient for detecting a physiological condition or event. While not shown explicitly in FIG. 1, electrodes and/or other sensors may be carried on the housing of medical device 4 and/or medical device 6 to facilitate performing various functions attributed to the respective medical device 4 or 6. In other examples, electrodes or other sensors may be carried by medical electrical leads extending from the medical device 4 or 6.

[0024] Medical devices 4 and 6 may be IMDs that are configured to communicate via an intrabody communication method. In other examples, however, one or both of medical devices 4 and/or 6 may be external devices, which may or may not be wearable devices but can be operatively coupled to the patient, e.g., using one or more cutaneous or transcutaneous sensors, electrodes, catheters, patches or the like, for performing one or more patient monitoring and/or therapy delivery functions. When both medical devices 4 and 6 are implanted in or otherwise operatively coupled to the patient, the two medical devices 4 and 6 may transmit and receive communication signals to/from each other for controlling an automatic adjustment of a control parameter by one of the two medical devices according to the techniques disclosed herein.

[0025] Medical devices 4 and 6 may perform independent functions, e.g., physiological signal monitoring and/or therapy delivery functions. For example, each medical device 4 and 6 may be fully functional without requiring the second device present in the patient in order to perform its intended physiological monitoring and/or therapy delivery functions. At least one medical device 4 or 6, however, may be configured to adjust at least one control parameter that could result in undesirable device interactions or conflicts when both devices 4 and 6 are present and operating in/on the patient. As such, the two medical devices 4 and 6 may be configured to transmit and receive communication signals to and from each other in order to control automatic adjustment of at least one control parameter by at least one of the medical devices 4 or 6. An undesired output of the medical device system 1 as a whole could result when one medical device 4 or 6 adjusts a control parameter without verifying compatibility of the adjustment with the second medical device 6 or 4 prior to adjustment. For example, a therapy delivered by the first medical device 4 according to adjusted control parameter may cause interference with a therapy being delivered, a physiological signal being sensed, or a measurement or test protocol or algorithm being performed by the second medical device 6.

[0026] As such, prior to performing adjustment of a control parameter, medical device 4 may be configured to transmit an intrabody signal to medical device 6 to confirm that adjustment is not expected to result in an undesired interaction with the second medical device 6. As used herein, “intrabody communication” refers to the transmitting and receiving of signals through at least a portion of the patient’s body. The term “intrabody communication” may refer to the transmission and reception of communication signals wholly or entirely within a patient’s body, e.g., between two IMDs. In some cases, the intrabody communication includes transmitting and receiving communication signals via electrodes, antennas, light emitting diodes (LED), microphones, or other transmitting/receiving devices of the intrabody communication system that are implanted in the patient’s body and/or positioned cutaneously on the patient’s skin. As such, in some examples, intrabody communication could include transmission and/or reception of signals at the surface of the patient’s skin.

[0027] Medical devices 4 and 6 may be configured to perform intrabody communication via radiofrequency (RF) signals, infrared (IR) signals, acoustical signals, tissue conductance communication (TCC) signals or other communication protocol signals. The methods disclosed herein for controlling automatic adjustment of a control parameter by a medical device are not limited to practice in conjunction with a particular form or type of intrabody or inter-device communication. Rather, the intrabody, inter-device communication that is performed can conform to any communication method that the medical devices, e.g., medical devices 4 and 6, are configured to perform.

[0028] In accordance with the techniques disclosed herein, a first medical device 4 may determine that a control parameter adjustment is needed, e.g., by determining that a test protocol or performing a measurement from a physiological signal is to be performed or determining that criteria for adjusting a control parameter have been met. In some instances, a single control parameter is to be adjusted from a current setting or value to a new pending setting or value. In other instances, multiple control parameter adjustments may be pending in order to perform a test protocol or measurement from a physiological signal. For example, executing a test protocol may involve one or more adjustments to one or more control parameters. One example of a test protocol that may involve multiple control parameter adjustments is a cardiac pacing capture test. A pacing capture test may be a capture verification test that applies a pacing pulse and verifies that an evoked response signal is sensed following the pacing pulse at the current pacing output settings (e.g., pacing pulse amplitude and pacing pulse width). However in order to ensure that the pacing pulse is delivered prior to an intrinsic depolarization, a pacing interval may be shortened to deliver the pacing pulse earlier in the cardiac cycle than an expected intrinsic depolarization, sometimes referred to as overdrive cardiac pacing. The pacing interval that is shortened may be a lower rate interval or an atrioventricular (AV) pacing interval. [0029] In other instances, a pacing capture test may be a capture threshold test performed to determine the lowest pacing pulse output at which pacing capture is detected. During the capture threshold test, a pacing interval (e.g., an AV pacing interval or a lower rate pacing interval) may be shortened to promote delivery of the test pacing pulses prior to an intrinsic depolarization. Additionally, the pacing pulse output, e.g., the pacing pulse amplitude, may be adjusted to one or more settings to test what pacing pulse amplitudes result in capture of the heart. In some cases, the pacing pulse output may be adjusted by additionally or alternatively adjusting the pacing pulse width to one or more settings during the pacing capture threshold test. Other examples of test protocols that may be performed by a medical device that requires adjustment of control parameter preceded by intrabody communication between the medical device performing the adjusting and a second medical device are described below.

[0030] Prior to adjusting the control parameter(s), which may be adjusted in conjunction with executing a test protocol, the first medical device 4 may transmit a request signal 5 to the second medical device 6. The request signal 5 may include an indication of the control parameter to be adjusted, the current value of the control parameter, the new or pending value of the control parameter and/or a test to be performed by the first medical device 4. The request signal 5 can be transmitted by the first medical device 4 to obtain a reply signal 7 from the second medical device 6 indicating whether or not the first medical device 4 may proceed with the automatic adjustment of the control parameter. The request signal 5 may include only data relating to the control parameter adjustment, e.g., the identity of the control parameter, the current or pending value(s) of the control parameter and or the test protocol to be performed. The request signal 5 may not include any other data derived from functions performed by the medical device 4, such as data derived from a physiological signal sensed by the medical device 4 or data relating to therapy that is or has been delivered by the medical device 4. The control parameter and its current or pending values, however, may be used by the medical device 4 to control such functions. Furthermore, the request signal 5 may not be a request for the second medical device 6 to modify its function based on the pending control parameter adjustment.

[0031] The second medical device 6 is configured to receive the request signal 5, determine a response to the request signal 5 and transmit the reply signal 7 back to the first medical device 4. The reply signal 7 may be an approval signal, indicating that the automatic adjustment may proceed. The second medical device 6 may determine to transmit an approval signal by determining that the automatic adjustment of the control parameter (or the execution of a test protocol that involves one or more automatic adjustments of one or more control parameters) is not expected to interfere with the function of the second medical device. For example, the second medical device 6 may determine that now tests or measurements or other operations are being performed that would likely result in interference of either of the first or second medical device functions. [0032] In some instances, the second medical device 6 may determine to transmit the approval signal by determining that a temporary suspension of a function of the second medical device 6 or a temporary adjustment of a control parameter used by the second medical device 6 to control a function of the second medical device may be performed so that the first medical device 4 may proceed with performing a test protocol without interference from the second medical device functions. The second medical device 6 may reverse a temporary suspension or adjustment after a specified period of time or until a test completion signal is received from the first medical device 4. In other instances, the second medical device 6 may automatically adjust one or more of its own control parameters so that the first medical device 4 may proceed with implementing the new control parameter setting for controlling a function of the first medical device 4 without interference from functions performed by the second medical device 6. As described below in conjunction with FIG. 8, in some examples, the first medical device 4 may determine that a control parameter is being adjusted from an on or enabled setting to an off or disabled setting so that a function currently being performed by medical device 4 is to be disabled. In order to preserve that function within the medical device system 1 as a whole, the request signal 5 may be a notification that the function is to be disabled in medical device 4. The second medical device 6 may reply with an approval signal and enable the function to be performed by medical device 6 (if not already enabled) so that the medical device system 1 as whole continues to perform the function. In still other examples, the second medical device 6 does not modify its own control parameters or functions in any way and either transmits an approval signal or a disapproval signal based on an evaluation of whether a medical device system conflict between functions of the two medical devices 4 and 6 could result if the control parameter is changed in the first medical device 4. A medical device system conflict may be an unintended or undesired medical device system output or failure to perform a desired function as intended.

[0033] When the second medical device determines a medical device system conflict (e.g., interference between the function of the first medical device 4 and a function of the second medical device 6) due to the pending control parameter adjustment, the second medical device 6 may transmit the reply signal 7 as a disapproval signal. In some instances, the disapproval signal is a delay request. The second medical device 6 may be executing a test protocol or performing a measurement that requires sensing of physiological signals, impedance signals or other signals and may require generating electrical signals (e.g., cardiac pacing pulses, impedance drive signal, etc.) to perform the test protocol or measurement. In this case, the second medical device function may be interfered with if the first medical device 4 performs the automatic adjustment of the control parameter of the first medical device at the time that the second medical device is performing a test protocol or measurement. As such, the second medical device 6 may transmit a disapproval signal with a delay request as the reply signal 7. The first medical device 4 may withhold the automatic adjustment of the control parameter by delaying the adjustment for a specified period of time or repeat the request signal 5 at a later time, e.g., after a specified time period or a next scheduled time for performing a protocol that involves automatic adjustment of the control parameter. [0034] In still other examples, the second medical device 6 may transmit the reply signal 7 as disapproval signal that is a denial signal. The second medical device 6 may determine the reply signal 7 to be a denial signal by determining that the requested adjustment of the control parameter (or associated test protocol) to be performed by the first medical device 4 would interfere with a function of the second medical device 6. The first medical device 4 may withhold the adjustment of the control parameter by cancelling the automatic adjustment of the control parameter (or the test protocol) for an indefinite period of time. In some cases, the first medical device 4 may repeat the request signal 5 at a subsequent time point if the first medical device 4 again determines that the control parameter adjustment is needed.

[0035] FIG. 2 is a conceptual diagram of a medical device system 10 including multiple IMDs in operative contact with a patient and capable of intrabody communication according to one example. Medical device system 10 is provided as an illustrative example of two IMDs 14 and 114 that may be co-implanted in a patient. In this example, medical device system 10 includes an ICD 14 and a pacemaker 114. ICD 14 and pacemaker 114 are configured to communicate wirelessly in this example although in some instances two or more devices may be coupled via communication cables or wires for conducting intrabody communication signals between medical devices. In some examples, ICD 14 and pacemaker 114 are configured to communicate via TCC to exchange request and reply signals as generally described above in conjunction with FIG. 1. Examples of medical devices and methods for performing TCC that may be adapted for performing the techniques disclosed herein are generally disclosed in U.S. Patent No. 9,636,511 (Carney, et al., filed January 23, 2015) and U.S. Patent No. 9,808,632 (Reinke, et al., filed January 23, 2015), the entire content of both incorporated herein by reference. In other examples, ICD 14 and pacemaker 114 may be configured to communicate via an RF communication protocol, e.g., BLUETOOTH® Low Energy (BLE), Wi-Fi, an IEEE standard, Medical Implant Communication Service (MICS) or other communication protocol.

[0036] Medical device system 10 including ICD 14 and pacemaker 114 may be capable of sensing cardiac electrical signals produced by the patient’s heart 8 and delivering CV/DF shocks and/or cardiac pacing pulses to the patient’s heart 8. The cardiac signal sensing and the delivery of cardiac electrical stimulation pulses performed by ICD 14 or pacemaker 114 can be controlled by respective control circuitry included in the respective, individual ICD 14 or pacemaker 114 according to operating control parameters. At least some of the control parameters utilized by ICD 14 and/or pacemaker 14 can be programmable by an external programming device 50.

[0037] ICD 14 includes a housing 15 that forms a hermetic seal that protects internal components of ICD 14. The housing 15 of ICD 14 may be formed of a conductive material, such as titanium or titanium alloy. The housing 15 may function as an electrode (sometimes referred to as a “can” electrode). In other instances, the housing 15 of ICD 14 may include a plurality of electrodes on an outer portion of the housing. The outer portion(s) of the housing 15 functioning as an electrode(s) may be coated with a material, such as titanium nitride for reducing post-stimulation polarization artifact. Housing 15 may be used as an active can electrode for use in delivering CV/DF shocks or other high voltage pulses delivered using a high voltage therapy circuit. In other examples, housing 15 may be available for use in delivering relatively lower voltage cardiac pacing pulses and/or for sensing cardiac electrical signals in combination with electrodes carried by lead 16. In any of these examples, housing 15 may sometimes be used in a transmitting and/or receiving electrode vector for transmitting and/or receiving TCC signals according to the intrabody communication techniques performed for controlling automatic adjustment of one or more control parameters by at least one of ICD 14 or pacemaker 114 as disclosed herein.

[0038] ICD 14 is shown coupled to a medical electrical lead 16 (referred to hereafter as “lead” 16) carrying one or more electrodes positioned in operative proximity to the patient’s heart 8. ICD 14 includes a connector assembly 17 (also referred to as a connector block or header) that includes electrical feedthroughs crossing housing 15 to provide electrical connections between conductors extending within the lead body 18 of lead 16 and electronic components included within the housing 15 of ICD 14. As will be described in further detail herein, housing 15 may house one or more processors, memories, transceivers, cardiac electrical signal sensing circuitry, therapy delivery circuitry, communication circuitry, power sources, other optional sensors and/or other components for sensing cardiac electrical signals, detecting a heart rhythm, and controlling and delivering electrical stimulation pulses to treat an abnormal heart rhythm.

[0039] In this example lead 16 includes an elongated lead body 18 having a proximal end 27 that includes a lead connector (not shown) configured to be connected to ICD connector assembly 17 and a distal portion 25 that includes one or more electrodes. The distal portion 25 of lead body 18 may include defibrillation electrodes 24 and 26 and pace/sense electrodes 28 and 30. In some cases, defibrillation electrodes 24 and 26 may together form a defibrillation electrode in that they may be configured to be activated concurrently. Alternatively, defibrillation electrodes 24 and 26 may form separate defibrillation electrodes in which case each of the electrodes 24 and 26 may be selectively activated independently.

[0040] Electrodes 24 and 26 (and in some examples housing 15) are referred to herein as defibrillation electrodes because they can be utilized, individually or collectively, for delivering high voltage stimulation therapy (e.g., cardioversion or defibrillation shocks). Electrodes 24 and 26 may be elongated coil electrodes and generally have a relatively high surface area for delivering high voltage electrical stimulation pulses compared to pacing and sensing electrodes 28 and 30. However, electrodes 24 and 26 and housing 15 may also be utilized to provide pacing functionality, sensing functionality, and/or TCC signal transmitting and receiving in addition to or instead of high voltage stimulation therapy. In this sense, the use of the term “defibrillation electrode” herein should not be considered as limiting the electrodes 24 and 26 for use in only high voltage cardioversion/defibrillation shock therapy applications. For example, electrodes 24 and 26 may be used in a sensing vector used to sense cardiac electrical signals and detect and discriminate tachyarrhythmias. Electrodes 24 and 26 may be used in a TCC signal transmitting electrode vector in combination with each other, collectively with housing 15, or individually with housing 15. When ICD 14 operates in a receiving mode for receiving TCC signals from pacemaker 114, electrodes 24, 26 and/or housing 15 may be used in a TCC receiving electrode vector. The TCC transmitting and receiving electrode vectors may be the same or different vectors.

[0041] Electrodes 28 and 30 are relatively smaller surface area electrodes which can be available for use in sensing electrode vectors for sensing cardiac electrical signals and may be used for delivering relatively low voltage pacing pulses in some configurations. Electrodes 28 and 30 are referred to as pace/sense electrodes because they are generally configured for use in low voltage applications, e.g., delivery of relatively low voltage pacing pulses and/or sensing of cardiac electrical signals, as opposed to delivering high voltage CV/DF shocks. In some instances, electrodes 28 and 30 may provide only pacing functionality, only sensing functionality or both. Furthermore, one or both of electrodes 28 and 30 may be used for TCC signal transmission and/or receiving in some examples, together or in combination with any of electrodes 24, 26 and/or housing 15. In the example illustrated in FIG. 1, electrode 28 is located proximal to defibrillation electrode 24, and electrode 30 is located between defibrillation electrodes 24 and 26. Electrodes 28 and 30 may be ring electrodes, short coil electrodes, hemispherical electrodes, or the like. Electrodes 28 and 30 may be positioned at other locations along lead body 18 and are not limited to the positions shown. In other examples, lead 16 may include none, one or more pace/sense electrodes and/or one or more defibrillation electrodes.

[0042] ICD 14 may obtain cardiac electrical signals corresponding to electrical activity of heart 8 via a combination of sensing electrode vectors that include combinations of electrodes 24, 26, 28, 30 and/or housing 15. Various sensing electrode vectors utilizing combinations of electrodes 24, 26, 28, and 30 may be selected by sensing circuitry included in ICD 14 for receiving a cardiac electrical signal via one or more sensing electrode vectors.

[0043] A TCC transmitting/receiving electrode vector may be selected from the available electrodes, e.g., defibrillation electrodes 24, 26, 28, 30 and housing 15 of ICD 14. The TCC transmitting/receiving electrode vector may be used for transmitting TCC signals produced by a TCC transmitter included in ICD 14 and for receiving TCC signals from another device, e.g., pacemaker 114.

[0044] ICD 14 may include an RF antenna in connector assembly 17 for receiving and transmitting RF communication signals with an RF transceiver enclosed within housing 15. In some examples, when a control parameter adjustment by control circuitry of ICD 14 is pending, RF communication signals may be transmitted to and received from pacemaker 114. For example, when a control parameter adjustment is pending, ICD 14 may transmit a communication signal to pacemaker 114 requesting a response. The response may be an approval or a disapproval signal as examples. In some examples, communication circuitry included in ICD 14 may include an RF antenna and transceiver for bidirectional communication with external programming device 50 and TCC circuitry for transmitting and receiving intrabody TCC signals, e.g., via transmitting and receiving pairs of electrodes carried by lead 16 and/or housing 15, for communicating with pacemaker 114. TCC may be used for intrabody communication with pacemaker 114 and RF communication may be used for communication with external programming device 50. More generally, ICD 14 may include communication circuitry for communicating according to two different methods, e.g., two different protocols and/or two different communication circuits, for communicating with external programming device 50 and for communicating with pacemaker 14 in some examples. In other examples, ICD 14 and pacemaker 114 may be configured to communicate via the same circuitry and communication protocol as that used to communicate with external programming device 50.

[0045] In the example shown, lead 16 extends subcutaneously or submuscularly over the ribcage 32 medially from the connector assembly 27 of ICD 14 toward a center of the torso of patient 12, e.g., toward xiphoid process 20 of patient 12. At a location near xiphoid process 20, lead 16 bends or turns and extends superiorly, e.g., subcutaneously or submuscularly over the ribcage and/or sternum or substernally under the ribcage and/or sternum 22. Although illustrated in FIG. 2 as being offset laterally from and extending substantially parallel to sternum 22, the distal portion 25 of lead 16 may be implanted at other locations, such as over sternum 22, offset to the right or left of sternum 22, angled laterally from sternum 22 toward the left or the right, or the like. Alternatively, lead 16 may be placed along other subcutaneous, submuscular or substernal paths. The path of extra-cardiovascular lead 16 may depend on the location of ICD 14, the arrangement and position of electrodes carried by the lead body 18, and/or other factors.

[0046] ICD 14 is shown implanted subcutaneously on the left side of patient 12 along the ribcage 32. ICD 14 may, in some instances, be implanted between the left posterior axillary line and the left anterior axillary line of patient 12. ICD 14 may, however, be implanted at other subcutaneous or submuscular locations in patient 12. For example, ICD 14 may be implanted in a subcutaneous pocket in the pectoral region. In this case, lead 16 may extend subcutaneously or submuscularly from ICD 14 toward the manubrium of sternum 22 and bend or turn and extend inferiorly from the manubrium to the desired location subcutaneously or submuscularly. In yet another example, ICD 14 may be placed abdominally.

[0047] In other arrangements, extra-cardiovascular lead 16 of system 10 is implanted at least partially underneath sternum 22 of patient 12. Lead 16 may extend subcutaneously or submuscularly from ICD 14 toward xiphoid process 20 and at a location near xiphoid process 20 bend or turn and extend superiorly within the anterior mediastinum in a substemal position. The anterior mediastinum may be bounded laterally by the pleurae, posteriorly by the pericardium, and anteriorly by the sternum 22. The distal portion of lead 16 may extend along the posterior side of sternum 22 substantially within the loose connective tissue and/or substemal musculature of anterior mediastinum. A lead implanted such that the distal portion 25 is substantially within anterior mediastinum, may be referred to as a “substemal lead.”

[0048] As a substemal lead, lead 16 can located substantially centered under sternum 22. In other instances, however, lead 16 may be implanted such that it is offset laterally from the center of sternum 22. In some instances, lead 16 may extend laterally such that distal portion 25 of lead 16 is undemeath/below the ribcage 32 in addition to or instead of sternum 22. In other examples, the distal portion 25 of lead 16 may be implanted in other extra-cardiac, intra-thoracic locations, including in the pleural cavity or around the perimeter of and adjacent to the pericardium of heart 8.

[0049] The lead body 18 of lead 16 may be formed from a non-conductive material and shaped to form one or more lumens within which the one or more conductors extend. Lead body 18 may be a flexible lead body that conforms to an implant pathway. In other examples, lead body 18 may include one or more preformed curves. Electrical conductors (not illustrated) extend through one or more lumens of the elongated lead body 18 of lead 16 from the lead connector at the proximal lead end 27 to electrodes 24, 26, 28, and 30 located along the distal portion 25 of the lead body 18. The elongated electrical conductors contained within the lead body 18 are each electrically coupled with respective defibrillation electrodes 24 and 26 and pace/sense electrodes 28 and 30, which may be separate respective insulated conductors within the lead body 18. The respective conductors electrically couple the electrodes 24, 26, 28, and 30 to circuitry of ICD 14, such as a signal generator for therapy delivery and TCC signal transmission, when intrabody communication is performed via TCC, and/or a sensing circuit for sensing cardiac electrical signals and/or receiving TCC signals in some examples, via connections in the connector assembly 17, including associated electrical feedthroughs crossing housing 15.

[0050] The electrical conductors may transmit therapy from a therapy delivery circuit within ICD 14 to one or more of defibrillation electrodes 24 and 26 and/or pace/sense electrodes 28 and 30 and transmit sensed electrical signals from one or more of defibrillation electrodes 24 and 26 and/or pace/sense electrodes 28 and 30 to the sensing circuit within ICD 14. When ICD 14 and pacemaker 114 communicate via TCC, the electrical conductors also transmit TCC signals from a TCC transmitter to electrodes selected for transmitting the TCC signals. ICD 14 may receive TCC signals from pacemaker 114 conducted from a receiving pair of electrodes of ICD 14 to a TCC signal receiver enclosed by housing 15.

[0051] ICD 14 analyzes the cardiac electrical signals received from one or more sensing electrode vectors to monitor for abnormal rhythms, such as bradycardia, tachycardia or fibrillation. ICD 14 may analyze the heart rate and morphology of the cardiac electrical signals to monitor for tachyarrhythmia in accordance with any of a number of tachyarrhythmia detection techniques. ICD 14 generates and delivers electrical stimulation therapy in response to detecting a tachyarrhythmia, e.g., ventricular tachycardia (VT) or ventricular fibrillation (VF), using a therapy delivery electrode vector which may be selected from any of the available electrodes 24, 26, 28 30 and/or housing 15. ICD 14 may deliver ATP in response to VT detection, and in some cases may deliver ATP prior to a CV/DF shock or during high voltage capacitor charging in an attempt to avert the need for delivering a CV/DF shock. If ATP does not successfully terminate VT or when VF is detected, ICD 14 may deliver one or more CV/DF shocks via one or both of defibrillation electrodes 24 and 26 and/or housing 15. ICD 14 may generate and deliver other types of electrical stimulation pulses such as post-shock pacing pulses or bradycardia pacing pulses using a pacing electrode vector that includes any of electrodes 24, 26, 28, and 30 and/or the housing 15 of ICD 14. Bradycardia or post-shock pacing pulses may be delivered by ICD 14 to pace the ventricles of the patient’s heart when an R-wave is not sensed by ICD 14 before a pacing escape interval expires. The pacing escape interval may be a lower pacing rate interval corresponding to a programmed lower rate. The programmed lower rate may be used by ICD 14 for controlling the rate of delivered cardiac pacing pulses for maintaining a minimum heart rate of the patient.

[0052] In this illustrative example, ICD 14 is co-implanted with pacemaker 114, however, it is to be understood that the techniques disclosed herein may be implemented in conjunction with a medical device system including an ICD coupled to one or more transvenous leads and/or a non-transvenous leads, one or more leadless pacemakers, a pacemaker coupled to one or more transvenous leads carrying electrodes and/or other sensors, an ICD coupled to transvenous leads, a cardiac monitor, a blood pressure monitor, a fluid status monitor, an oxygen saturation monitor, or other monitor including one or more sensors, a drug pump, a neurostimulator, or other medical device or any combination thereof configured to perform intrabody communication with each other.

[0053] Pacemaker 114 is shown as a leadless intracardiac pacemaker configured to communicate with ICD 14. Pacemaker 114 may include one or more housing-based electrodes as described below in conjunction with FIG. 3 for sensing cardiac electrical signals and delivering cardiac pacing pulses. Pacemaker 114 may be delivered transvenously and anchored by a fixation member at an intracardiac pacing and sensing site. For example, pacemaker 114 may be implanted in an atrial or ventricular chamber of the patient’s heart. In other examples, pacemaker 114 may be attached to an external surface of heart 8 (e.g., in contact with the pericardium and/or epicardium) such that pacemaker 114 is disposed outside of heart 8.

[0054] Pacemaker 114 is configured to deliver cardiac pacing pulses via a pair of housingbased electrodes and may be configured to sense cardiac signals for determining the need and delivery time of a pacing pulse. For example, pacemaker 114 may deliver bradycardia pacing pulses, rate responsive pacing pulses, ATP, post-shock pacing pulses and/or other pacing therapies based on sensed cardiac signals. In some examples, pacemaker 114 may include an accelerometer or other motion sensor for sensing acceleration signals associated with mechanical activity of heart 8. For instance, pacemaker 114 may be configured to sense atrial event signals corresponding to atrial mechanical systole for triggering atrial synchronous ventricular pacing pulses delivered by pacemaker 114. In other examples, pacemaker 114 may sense atrial electrical signals for triggering atrial synchronous ventricular pacing pulses.

[0055] Pacemaker 114 may be implanted in the right atrium or the right ventricle of heart 8 to sense cardiac signals and deliver pacing therapy. Pacemaker 114 may be implanted in the right ventricle for sensing a ventricular electrogram (EGM) signal and deliver ventricular pacing pulses. Pacemaker 114 may be implanted at or near the ventricular apex in the right ventricle to pacing the ventricular myocardium. In other examples, pacemaker 114 may be implanted along the interventricular septum to provide pacing of the conduction system (e.g., via the left and/or right bundle branches) and/or septal myocardium.

[0056] In some examples, pacemaker 114 is implanted in the right atrium and configured for sensing a ventricular EGM signal and delivering ventricular pacing pulses from a right atrial position. For example, a distal tip electrode (shown in FIG. 3) may be advanced toward the His bundle from a location beneath the AV node and near the tricuspid valve annulus, generally in the Triangle of Koch, to position an electrode near the His bundle from a right atrial approach. Pacing pulses may be delivered to this location for capturing the ventricles via the native conduction system of the heart and/or ventricular myocardium. When implanted in the right atrium, pacemaker 114 may additionally or alternatively sense an atrial EGM signal and/or deliver atrial pacing pulses. Pacemaker 114 may operate in an atrial synchronous ventricular pacing mode, e.g., denoted as a VDD or DDD pacing mode. Ventricular pacing pulses may be delivered by pacemaker 114 at an atrioventricular pacing interval from a sensed P-wave or delivered atrial pacing pulse. At other times, pacemaker 114 may operate in a single chamber atrial pacing mode or a single chamber, asynchronous ventricular pacing mode, e.g., a VVI or VOO pacing mode.

[0057] External programming device 50 is shown configured for wireless telemetric communication with ICD 14, e.g., via a wireless communication link 42, and for wireless telemetric communication with pacemaker 114, e.g., via a wireless communication link 44. Communication link 42 or 44 may be established between ICD 14 or pacemaker 114, respectively, and external programming device 50 using any of the example communication techniques described above in conjunction with FIG. 1. While both communication links 42 and 44 are illustrated in FIG. 2, it is to be understood that external programmer 50 may be configured to communicate with ICD 14 or pacemaker 114 in separate, non-simultaneous communication sessions. In some examples, ICD 14 and/or pacemaker 114 may communicate with external programming device 50 using TCC, e.g., using TCC transmitting/receiving electrodes coupled to external programming device 50 and placed externally on patient 12.

[0058] External programming device 50 may be used to program operating parameters and algorithms in ICD 14 for controlling ICD functions and/or to program operating parameters and algorithms in pacemaker 114 for controlling pacemaker functions. External programming device 50 may be used to program cardiac signal sensing control parameters, cardiac rhythm detection control parameters and therapy delivery control parameters used by ICD 14 and by pacemaker 114 in respective programming sessions with the individual devices 14 and 114. Data stored or acquired by ICD 14 and/or pacemaker 114, including physiological signals or associated data derived therefrom, results of device diagnostics, and histories of detected rhythm episodes and delivered therapies, may be retrieved from ICD 14 and/or pacemaker 114 by external programming device 50 following an interrogation command.

[0059] External programming device 50 may include a processor 52, memory 53, display unit 54, user interface 56 and communication unit 58. Processor 52 controls external programming device operations and processes data and signals received from ICD 14 and/or pacemaker 114. Display unit 54, which may include a graphical user interface (GUI), displays data and other information to a user for reviewing medical device operation and programmed parameters as well as physiological signals retrieved from ICD 14 and/or pacemaker 114, for example. During an interrogation session with a respective medical device 14 or 114, processor 52 may receive data relating to sensed physiological signals or detected physiological events or conditions. During an interrogation session with a respective medical device 14 or 114, processor 52 may receive the values of control parameters currently in effect. Data received from the ICD 14 and/or pacemaker 114 during the interrogation session may be displayed by display unit 54 for review by a clinician.

[0060] Processor 52 may execute instructions stored in memory 53. Processor 52 may include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or analog logic circuitry. In some examples, processor 52 may include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functions attributed to processor 52 herein may be embodied as software, firmware, hardware or any combination thereof.

[0061] Memory 53 may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other digital or analog media. Memory 53 may be configured to store various medical device control parameters, e.g., physiological signal sensing control parameters, physiological event detection control parameters, and/or therapy delivery control parameters, and associated programmable settings for each of ICD 14 and pacemaker 114. [0062] User interface 56 may include a mouse, touch screen, keypad or the like to enable a user to interact with external programming device 50 to initiate a communication session with ICD 14 or pacemaker 114 for retrieving data from and/or transmitting data to the respective medical device. A user interacting with user interface 56 may cause communication unit 58 to send and receive commands during the communication session. User interface 56 may include one or more input devices and one or more output devices, which may include display unit 54. The input devices of user interface 56 may include a communication device such as a network interface, keyboard, pointing device, voice responsive system, video camera, biometric detection/response system, button, sensor, mobile device, control pad, microphone, presence- sensitive screen, touch- sensitive screen (which may be included in display unit 54), or any other type of device for detecting input from a human or machine.

[0063] The one or more output devices of user interface 56 may include a network interface, display, sound card, video graphics adapter card, speaker, presence-sensitive screen, one or more USB interfaces, video and/or audio output interfaces, or any other type of device capable of generating tactile, audio, video, or other output. Display unit 54 may function as an input and/or output device using technologies including liquid crystal displays (LCD), quantum dot display, dot matrix displays, light emitting diode (LED) displays, organic light-emitting diode (OLED) displays, cathode ray tube (CRT) displays, e-ink, or monochrome, color, or any other type of display capable of generating tactile, audio, and/or visual output. In other examples, user interface 56 may produce an output to a user in another fashion, such as via a sound card, video graphics adapter card, speaker, presence- sensitive screen, touch-sensitive screen, one or more USB interfaces, video and/or audio output interfaces, or any other type of device capable of generating tactile, audio, video, or other output. In some examples, display unit 54 is a presence- sensitive display that may serve as a user interface device that operates both as one or more input devices and one or more output devices. [0064] Communication unit 58 may include a transceiver and antenna configured for bidirectional communication with a communication circuit included in each of ICD 14 and/or pacemaker 114. Communication unit 58 is configured to operate in conjunction with processor 52 for sending and receiving data to and from one of ICD 14 or pacemaker 114 during a communication session. A bidirectional communication link, e.g., represented by arrows 42 and 44, may be established between external programming device 50 and the respective ICD 14 or pacemaker 44 using a radio frequency (RF) link such as BLUETOOTH®, Wi-Fi, Zigbee or other IEEE specification based communication protocol, Global System for Mobile Communication (GSM) or other mobile communication protocol, Medical Implant Communication Service (MICS) or other RF, cellular or infrared communication protocols as examples.

[0065] External programming device 50 may be configured for wireless communication to enable programming of ICD 14 and/or pacemaker 114 when the respective medical device is implanted inside a patient’s body. In some examples, external programming device 50 may include a programming head that can be placed proximate the ICD 14 or pacemaker 14 to establish and maintain a communication link with the respective medical device. In other examples, external programming device 50 may be configured to communicate using a distance telemetry algorithm and circuitry that does not require the use of a programming head and does not require user intervention to maintain a communication link, allowing for ambulatory and/or remote programming of ICD 14 and/or pacemaker 114.

[0066] External programming device 50 may be embodied as a programmer used in a hospital, clinic or physician’s office to retrieve data from and to program operating parameters and algorithms in medical devices for controlling medical device functions. External programming device 50 may alternatively be embodied as a home monitor or hand-held device, such as a smart phone, tablet or other hand-held device. Aspects of external programming device 50 may generally correspond to the external programming/monitoring unit disclosed in U.S. Pat. No. 5,507,782 (Kieval, et al.), hereby incorporated herein by reference in its entirety. An example programmer that may be configured to program IMDs in a medical device system configured to perform the techniques disclosed herein is the CARELINK® Programmer, commercially available from Medtronic, Inc., Dublin, Ireland. [0067] FIG. 3 is a conceptual diagram of pacemaker 114 that may be included in the medical device system of FIG. 2 according to some examples. Pacemaker 114 may be a leadless pacemaker configured to communicate with another medical device in operative contact with a patient, e.g., ICD 14 as shown in FIG. 2. Pacemaker 114 may be implanted in a ventricular heart chamber for sensing cardiac signals and delivering ventricular pacing pulses. However, in some examples pacemaker 114 may be configured for implantation in the right atrium for providing atrial pacing and/or ventricular pacing from a right atrial location.

[0068] As generally described in conjunction with FIG. 4 below, a medical device, such as pacemaker 114, that is included in a multi-device system operating according to the techniques disclosed herein may include processing and control circuitry, memory, pulse generating circuitry for generating therapeutic electrical stimulation pulses, sensing circuitry for sensing physiological signals, TCC circuitry and/or other communication circuitry for transmitting and receiving communication signals and a power source. In some examples, a pulse generator of pacemaker 114 used to generate cardiac pacing pulses may be controlled for generating TCC signals transmitted via electrodes 162, 164 and/or 165 for communicating with another medical device, e.g., ICD 14.

[0069] Pacemaker 114 may include a housing 150 carrying housing-based electrodes 162, 164 and 165. The type, number and location of housing based electrodes provided on pacemaker 114 may be adapted for a particular implant location and sensing/pacing application. Other features of a leadless pacemaker such as fixation members, size, etc. may be adapted as necessary for a particular pacing and sensing application. As such, pacemaker 114 shown in FIG. 3 is illustrative in nature of a leadless pacemaker that can be one type of device that may be included in a medical device system that performs intrabody communication for coordinating automatic adjustment of control parameters according to the techniques disclosed herein. The illustrative example of pacemaker 114 is not intended to be a limiting example of a pacemaker or more generally an IMD that may be included in a medical device system configured to operate according to the disclosed techniques, particularly with regard to a specific implant location or features adapted for that implant location. In other examples, pacemaker 114 may be configured to receive one or more leads, each carrying one or more electrodes, which may be advanced transvenously into the patient’s heart for sensing and/or cardiac electrical stimulation therapy delivery in one or more heart chambers.

[0070] In this example, pacemaker 114 includes a housing 150 having a distal end face 102 and a proximal end face 104. The lateral sidewall 170 of housing 150 extending from distal end face 102 to proximal end face 104 may be generally cylindrical to facilitate transvenous delivery, e.g., via a catheter, of pacemaker 114 to an implant site. Distal end face 102 is referred to as “distal” in that it is expected to be the leading end as pacemaker 114 is advanced through a delivery tool, such as a catheter, and placed against a targeted implant site. In other examples, housing 150 may have a generally prismatic shape. The housing 150 encloses the electronics and a power supply for sensing cardiac signals, producing pacing pulses and controlling therapy delivery and other functions of pacemaker 114 as described herein.

[0071] Pacemaker 114 may be configured for sensing cardiac electrical signals, e.g., R- waves and/or P-waves, attendant to intrinsic depolarizations of the myocardial tissue and delivering pacing pulses. Pacemaker 114 is shown including electrodes 162, 164 and 165 spaced apart along the housing 150 of pacemaker 114 for sensing cardiac electrical signals and delivering pacing pulses. Pacemaker 114 may have more than or fewer than three electrodes, however. In another example, pacemaker 114 may only include electrodes 162 and 165 or only electrodes 162 and 164 for instance. Electrodes 162, 164 and 165 may be, without limitation, titanium, platinum, iridium or alloys thereof and may include a low polarizing coating, such as titanium nitride, iridium oxide, ruthenium oxide, platinum black, among others.

[0072] Electrode 164, also referred to herein as “tip electrode” 164, is shown extending from distal end face 102 of housing 150. Tip electrode 164 is shown as a screw-in helical electrode which may provide fixation of pacemaker 114 at an implant site as well as serving as a pacing and sensing electrode. In some examples, pacemaker 114 may be implanted in the right atrium so that electrode 164 can be advanced from within the right atrial chamber to a ventricular pacing site, e.g., toward or into the interventricular septum, for delivering pacing to the His-Purkinje conduction system and/or for pacing of ventricular septal myocardial tissue. A proximal portion of tip electrode 164, nearest housing distal end face 102, may be provided with an electrically insulative coating. The more distal portion of tip electrode 164, positioned at a target pacing site, may be uninsulated to function as the electrically conductive portion of tip electrode 164 for pacing pulse delivery and for sensing cardiac electrical signals, e.g., a ventricular EGM signal. Examples of insulating coatings that may be provided on the proximal portion of tip electrode 164 include parylene, urethane, poly ether ether ketone (PEEK), or polyimide, among others.

[0073] In other examples, tip electrode 164 is not necessarily a tissue piercing electrode as shown in this example. Electrode 164 may be a dot, button, ring, hemispherical, segmented, fishhook, helical, or other type of electrode positioned on the distal end face 102 for positioning in operative proximity to or within tissue at a targeted pacing site. When implemented as a non-tissue piercing electrode, tip electrode 164 may be implanted in intimate proximity to myocardial tissue and held in a stable position via other fixation means, e.g., anchored in the atrium or the ventricle via fixation tines, for pacing atrial myocardium or ventricular myocardium respectively and/or the conduction system of the heart, e.g., the His bundle, left bundle branch, and/or right bundle branch. For example, pacemaker 114 is shown in FIG. 2 having a tip electrode 164’ in the form of a button electrode instead of the helical tip electrode 164 shown in FIG. 3. As shown in FIG. 2, pacemaker 114 may include fixation times 168 for anchoring tip electrode 164’ at an implant site instead of the helical fixation mechanism of tip electrode 164 shown here. An example of a leadless pacemaker, which may be implemented in a medical device system performing the techniques disclosed herein, having a button-type distal tip electrode and fixation tines is generally disclosed in U.S. Patent No. 9,775,982 (Grubac, et al., filed October 3, 2017), incorporated herein by reference in its entirety.

[0074] Electrode 165 is shown as a ring electrode along the lateral side wall 170 of housing 150. In other examples, electrode 165 may be a dot, button, ring, hemispherical, segmented or other type of electrode positioned on the distal end face 102 of housing 150 and/or along the lateral sidewall 170. Electrode 162 is shown as a ring electrode along the lateral sidewall 170 of housing 150 spaced proximally from electrode 165, toward proximal end face 104 of housing 150. In other examples, electrode 162 may be a dot, button, ring, hemispherical, segmented or other type of electrode positioned on the proximal end face 104 of housing 150 and/or along the lateral sidewall 170, spaced proximally and/or laterally from electrode 165. Electrodes 162 and 165 may both be ring electrodes circumscribing the lateral sidewall 170 in some examples, e.g., adjacent proximal end face 104 and adjacent distal end face 102, respectively. Other portions of housing 150 may be electrically insulated by an insulating coating.

[0075] Tip electrode 164 may serve as a cathode electrode with ring electrode 162 serving as a return anode for delivering ventricular pacing pulses, which may be delivered to capture of at least a portion of the His-Purkinje system and/or ventricular myocardium. Tip electrode 164 and ring electrode 162 may be used as a bipolar pair for ventricular pacing and for receiving a ventricular electrical signal from which R-waves can be sensed by sensing circuitry enclosed by housing 150. When pacemaker 114 is implanted in the right atrium, electrodes 165 and 162 may form a second cathode and return anode pair for bipolar atrial pacing and sensing an atrial electrical signal from which P-waves can be sensed by the sensing circuitry enclosed by housing 150. In some examples, any combination of electrodes 162, 164 and 165 may be used in a sensing electrode vector for sensing one or more cardiac electrical signals from which P-waves and/or R-waves may be sensed.

[0076] Electrodes 162, 164 and 165 may be positioned at locations along pacemaker 114 other than the locations shown. Furthermore, in some examples, pacemaker 114 includes a distal tip electrode 164 and one proximal electrode 162 or 165. Pacemaker 114 may include a TCC receiver for receiving and detecting a TCC signal transmitted by another medical device, e.g., ICD 14 or any of the other examples described herein. A voltage potential develops across an electrode pair, e.g., tip electrode 164 and ring electrode 162 or between ring electrodes 162 and 165, in response to current conducted via a tissue pathway during TCC signal transmission from another medical device, e.g., ICD 14. [0077] A TCC transmitting electrode pair and a TCC receiving electrode pair (which may or may not be the same electrode pair) may be selected from the available electrodes 162, 164 and 165 when pacemaker 114 is configured to perform intrabody communication via TCC signals. A sensing/pacing electrode pair and the TCC electrode pair carried by housing 150 may include no shared electrodes, one shared electrode or two shared electrodes in various examples. In some examples, at least one electrode pair may be carried by housing 150 for sensing cardiac signals and delivering cardiac pacing and another electrode pair may be carried by housing 150 as a TCC electrode pair. The sensing/pacing electrode pair and the TCC electrode pair may be dedicated electrode pairs or selectable from available electrodes carried by housing 150. [0078] Pacemaker 114 may be configured to communicate with another medical device implanted in or operatively coupled to the patient. For example, as shown in FIG. 2, pacemaker 114 may communicate with an ICD 14. Pacemaker 114 and ICD 14 may communicate via TCC or another communication protocol when one of pacemaker 114 or ICD 14 is scheduled or triggered to adjust a control parameter. In other examples, pacemaker 114 may be co-implanted with another leadless pacemaker (e.g., implanted in a different heart chamber), another pacemaker coupled to transvenous lead(s) carrying electrodes positioned for pacing and sensing at a different location than pacemaker 114, an ICD coupled to transvenous leads, a cardiac monitor such as the REVEAL LINQ™ Insertable Cardiac Monitor (available from Medtronic, Inc., Dublin, Ireland), a blood pressure monitor, a fluid status monitor, an oxygen saturation monitor, or other monitor including one or more sensors, a drug pump, a neurostimulator, or other medical device configured to perform intrabody communication with pacemaker 114.

[0079] Housing 150 is formed from a biocompatible material, such as a stainless steel or titanium alloy. In some examples, the housing 150 may include an insulating coating. Examples of insulating coatings include parylene, urethane, PEEK, or polyimide, among others. The entirety of the housing 150 may be insulated, but only electrodes 162, 164 and 165 uninsulated. Electrodes 162, 164 and 165 are electrically coupled to internal circuitry, e.g., a pacing pulse generator and cardiac electrical signal sensing circuitry, enclosed by housing 150. Electrodes 162 and 165 may be formed as a conductive portion of housing 150 defining respective electrodes that are electrically isolated from each other and from the other portions of the housing 150 as generally shown in FIG. 3.

[0080] Pacemaker 114 may include features for facilitating deployment to and fixation at an implant site. For example, pacemaker 114 may optionally include a delivery tool interface 158. Delivery tool interface 158 may be located at the proximal end 104 of pacemaker 114 and is configured to connect to a delivery device, such as a catheter, guidewire or other tool used to position pacemaker 114 at an implant location during an implantation procedure. The delivery tool interface 158 may enable a clinician to advance, retract and steer pacemaker 114 to an implant site and rotate pacemaker 114 to advance the helical tip electrode 164 into the cardiac tissue. Helical tip electrode 164 in this example provides fixation of pacemaker 114 at the implant site. In other examples, however, pacemaker 114 may include a set of fixation tines, hooks or other fixation members at or near distal end face 102 to secure pacemaker 114 to cardiac tissue. Numerous types of fixation members may be employed for anchoring or stabilizing pacemaker 114 in an implant position.

[0081] FIG. 4 is a conceptual diagram of a medical device 214 that may be included in a medical device system and capable of performing intrabody communication with another member medical device of the medical device system according to some examples. For the sake of convenience, the medical device 214 is referred to herein as an “implantable medical device” or IMD 214. In various examples, two medical devices configured to perform intrabody communication may be IMDs. As mentioned previously herein, however, a medical device performing intrabody communication may be an external device configured to perform intrabody communication with another medical device by receiving and passing communication signals through a patient’s body via electrodes, an antenna or other transmitting/receiving device that is positioned on the patient’s skin or positioned transcutaneously. For the sake of convenience, the IMD 214 of FIG. 4 is generally described as being a cardiac pacing device or ICD, e.g., ICD 14 or pacemaker 114 shown in FIG. 2, coupled to two or more electrodes 224, 226, 228, and 230. In some examples, the device housing 215 may serve as one of the at least two electrodes and is represented conceptually as an electrode in FIG. 4 because it can be available for sensing electrophysiological signals, delivering electrical stimulation pulses and, in some examples, used as a receiving and/or transmitting electrode during TCC.

[0082] It is to be understood, however, that the circuitry and components shown in FIG. 4 may generally correspond to physiological sensing circuitry and/or therapy delivery circuitry included in any of the example medical devices referred to herein and can be adapted for performing physiological signal sensing and/or therapy delivery functions according to a particular clinical application for signal monitoring and/or therapy delivery. The circuitry of IMD 214 is configured to perform a function according to an adjustable control parameter.

[0083] IMD 214 configured to perform intrabody communication in association with automatic adjustment of a control parameter value as disclosed herein may have more or fewer electrodes than the four electrodes 224, 226, 228 and 230 shown in FIG. 4 and may not include any electrodes at all when configured to perform functions that do not require an electrode for sensing electrophysiological signals, delivering electrical stimulation pulses, or performing intrabody communication. In some instances, at least two electrodes may be provided for performing TCC transmission and receiving functions when IMD 214 is configured to perform intrabody communication via TCC with another member of a medical device system. The TCC electrodes may be leadless, housing-based electrodes and/or carried by a lead extending away from the device housing.

[0084] IMD 214 may include a control circuit 80, memory 82, therapy delivery circuit 84, sensing circuit 86, sensors 87, communication circuit 88, TCC circuit 90 and power source 89. Power source 89 provides power to the circuitry of IMD 214, including each of the circuits 80, 82, 84, 86, 87, 88 and 90 as needed. Power source 89 may include one or more energy storage devices, such as one or more rechargeable or non-rechargeable batteries. The connections between power source 89 and each of the other circuits 80, 82, 84, 86, 87, 88 and 90 are to be understood from the general block diagram of FIG. 4 but are not shown for the sake of clarity. For example, power source 89 may be coupled to charging circuits included in therapy delivery circuit 84 for charging capacitors or other charge storage devices and activating output switching circuitry included in therapy delivery circuit 84 for producing electrical stimulation pulses such as cardiac electrical stimulation pulses (e.g., CV/DF shock pulses or pacing pulses) or neurostimulation pulses. Power source 89 may be coupled to an optional TCC circuit 90 for providing power for generating TCC signals by transmitter 91 and powering TCC receiver 92. Power source 89 provides power to processors and other components of control circuit 80, memory 82, amplifiers, analog-to-digital converters and other components of sensing circuit 86, any additional sensors 87 optionally included in IMD 214 and a transceiver of communication circuit 88, when included, as examples. Because each IMD of a medical device system may be configured to operate independently of any other IMD when not co-implanted with another IMD, each IMD may be provided with a power supply for powering the various circuits and components of the individual IMD.

[0085] Memory 82 may store computer-readable instructions that, when executed by a processor included in control circuit 80, cause IMD 214 to perform various functions attributed to IMD 214 (e.g., sensing physiological signals, communication with another device, and/or delivery of an electrical stimulation therapy). Memory 82 may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, or any other digital or analog media.

[0086] Control circuit 80 may communicate with therapy delivery circuit 84 and sensing circuit 86 for sensing physiological electrical activity (e.g., cardiac electrical signals), detecting physiological events (e.g., cardiac arrhythmias), and controlling delivery of electrical stimulation therapies in response to sensed physiological signals. The functional blocks shown in FIG. 4 represent functionality included in IMD 214 and may include any discrete and/or integrated electronic circuit components that implement analog and/or digital circuits capable of producing the functions attributed to IMD 214 herein. Providing software, hardware, and/or firmware to accomplish the described functionality in the context of any modem medical device system, given the disclosure herein, is within the abilities of one of skill in the art.

[0087] Sensing circuit 86 may be selectively coupled to electrodes 224, 226, 228, 230 and/or housing 215 in order to monitor electrical activity of the patient’s heart. Sensing circuit 86 may include switching circuitry for selecting which electrodes 224, 226, 228, 230 and housing 215 are coupled to sense amplifiers or other cardiac event detection circuitry included in event detector 85. Switching circuitry may include a switch array, switch matrix, multiplexer, or any other type of switching device suitable to selectively couple sense amplifiers to selected electrodes. The event detector 85 within sensing circuit 86 may include one or more sense amplifiers, filters, rectifiers, threshold detectors, comparators, analog-to-digital converters (ADCs), or other analog or digital components configured to detect a feature from a sensed physiological signal to enable processing circuitry of control circuit 80 to monitor cardiac electrical signals for detecting a heart rhythm. In the example of IMD 214 sensing one or more cardiac electrical signals (e.g., an ECG or EGM), cardiac electrical event signals attendant to myocardial depolarizations, e.g., P-waves attendant to atrial depolarizations and/or R- waves attendant to ventricular depolarizations, may be sensed by event detector 85 from a cardiac electrical signal received via a sensing electrode vector.

[0088] In some examples, sensing circuit 86 includes multiple sensing channels for acquiring cardiac electrical signals from multiple sensing electrode vectors selected from electrodes 224, 226, 228, 230 and housing 215. Each sensing channel may be configured to amplify, filter, digitize and rectify the cardiac electrical signal received from selected electrodes coupled to the respective sensing channel to improve the signal quality for sensing cardiac event signals, e.g., P-waves and/or R-waves. For example, each sensing channel in sensing circuit 86 may include an input or pre-filter and amplifier for receiving a cardiac electrical signal developed across a selected sensing electrode vector, an analog- to-digital converter, a post- amplifier and filter, and a rectifier to produce a filtered, digitized, rectified and amplified cardiac electrical signal. The event detector 85 may include a sense amplifier, comparator or other circuitry for comparing the rectified, filtered and amplified cardiac electrical signal to a cardiac event sensing threshold, such as a P- wave sensing threshold amplitude or an R-wave sensing threshold amplitude, which may be an auto-adjusting threshold. Event detector 85 may produce a sensed cardiac event signal in response to a sensing threshold crossing that is passed to control circuit 80. The sensed cardiac event signals corresponding to detected R-waves and/or P-waves can be used by control circuit 80 for determining a heart rate, detecting cardiac rhythms and determining a need for a pacing and/or CV/DF therapy.

[0089] Sensing circuit 86 may operate to sense cardiac event signals according to a number of sensing control parameters used to apply blanking periods, refractory periods and the cardiac event sensing threshold to the sensed cardiac electrical signal. The cardiac event sensing threshold may be controlled according to a programmed sensitivity that defines a “sensing floor” or the lowest amplitude signal that may be sensed as a cardiac event signal. The cardiac event sensing threshold may be controlled according to a programmed starting sensing threshold amplitude which may be set to a percentage of an immediately preceding sensed event maximum peak amplitude (e.g., sensed P-wave peak amplitude or sensed R-wave peak amplitude). The cardiac event sensing threshold (e.g., P- wave sensing threshold or R-wave sensing threshold) may be controlled to decrease from the starting sensing threshold amplitude to the programmed sensitivity until a cardiac event sensing threshold crossing occurs. The decrease from the starting sensing threshold amplitude to the programmed sensitivity may be controlled by sensing circuit 86, under the control of control circuit 80, according to one or more drop times, step decrements, decay times and/or decay rates. In some examples, IMD 214 may be configured to automatically adjust one or more of the sensing control parameters, e.g., one or more blanking periods, refractory periods and/or cardiac event sensing threshold control parameters. [0090] Control circuit 80 may include interval timers or counters, which may be reset upon receipt of a cardiac sensed event signal from sensing circuit 86. The value of the interval timer or counter when reset by a cardiac sensed event signal, for example, may be used by control circuit 80 to measure the cardiac cycle length or other cardiac event intervals, e.g., durations of R-R intervals, P-R intervals, or P-P intervals, which are measurements that may be stored in memory 82. Control circuit 80 may use the cardiac event intervals to detect an arrhythmia, e.g., bradycardia or tachyarrhythmias such as fibrillation or tachycardia. A measured P-R interval may be used to determine the AV conduction time which, in turn, may be used for adjusting one or more control parameters used in controlling cardiac pacing pulse delivery, e.g., the AV pacing interval, pacing mode and/or pacing electrode vector(s) used for delivering a pacing therapy, e.g., cardiac resynchronization therapy, a conduction system pacing therapy, or atrial synchronous ventricular pacing therapy.

[0091] The therapy delivery circuit 84 may include a pulse generator configured to generate cardiac electrical stimulation pulses, e.g., CV/DF shock pulses and cardiac pacing pulses for delivery to the patient’s heart via selected electrodes 224, 226, 228, 230 and/or 215. Therapy delivery circuit 84 may include one or more energy storage elements, such as one or more capacitors, configured to store the energy required for a therapeutic CV/DF shock or pacing pulse. In response to detecting a shockable tachyarrhythmia, control circuit 80 controls therapy delivery circuit 84 to charge the energy storage element(s) to prepare for delivering a CV/DF shock. Therapy delivery circuit 84 may include other pulse generating circuitry, such as a transformer, charge pump, charge storage capacitors and switches to couple the charge storage capacitors to electrode terminals via an output capacitor or other output circuitry such as an H-bridge to discharge and deliver the electrical stimulation pulses. Therapy delivery circuit 84 may include voltage levelshifting circuitry, switches, transistors, diodes, or other circuitry as needed for generating and delivering electrical stimulation pulses. In some examples, therapy delivery circuit 84 may include both a low voltage therapy circuit for generating and delivering relatively low voltage therapy pulses, such as cardiac pacing or neurostimulation pulses, and a high voltage therapy circuit for generating and delivering CV/DF shocks or other relatively higher voltage stimulation pulses which may include cardiac pacing pulses delivered via extra-cardiac electrodes as described in conjunction with FIG. 2. [0092] In some examples, IMD 214 can be configured to monitor the impedance of an electrode vector. For example, therapy delivery circuit 84 may apply a current (or voltage) drive signal to a pair of electrodes coupled to IMD 214. Sensing circuit 86 may detect the resulting voltage (or current) developed across a pair of recording electrodes. Impedance monitoring may be performed to monitor bioimpedance in a tissue volume, e.g., thoracic impedance or cardiac impedance, for monitoring a patient condition. For example, impedance monitoring may be performed for tracking a fluid status of the patient, e.g., correlated to lung wetness in patients with symptoms of congestive heart failure. A fluid status metric may be determined from impedance measurements by control circuit 80 and stored in memory 82 over time for detecting when the fluid status metric meets a threshold for detecting a pulmonary edema condition for example.

[0093] TCC circuit 90 may include a TCC transmitter 91 configured to generate TCC signals for transmission from a transmitting electrode vector selected from the electrodes 224, 226, 228, 230 and housing 215 via a conductive tissue pathway. TCC transmitter 91 is configured to generate and transmit a TCC signal to communicate with another IMD (or in some cases an external device coupled to the patient via skin electrodes or transcutaneous electrodes). In some examples, TCC circuit 90 may include a pulse generator for generating TCC signals and switching circuitry for selectively coupling TCC transmitter 91 to a selected transmitting electrode vector, e.g., using any two or more of electrodes 224, 226, 228, 230 and housing 215.

[0094] The TCC signal may be transmitted by TCC circuit 90 having a carrier signal, which may be an oscillating signal, having a peak-to-peak amplitude and carrier frequency selected to avoid stimulation of excitable tissue, e.g., nerve, smooth muscle, skeletal muscle or cardiac tissue, of the patient. In some examples, the carrier frequency of the TCC signal may be 100 kilohertz (kHz) or higher. A TCC signal emitted or received, for example by a TCC electrode pair, at a frequency of at least approximately 100 kHz may be less likely to stimulate nearby tissue, e.g., muscles or nerves, or cause pain or other sensation than lower frequency waveforms. Consequently, a TCC signal having a frequency of at least approximately 100 kHz can have a higher amplitude than a lower frequency signal without causing extraneous nerve or muscle stimulation. A relatively higher amplitude signal may increase the likelihood that another medical device successfully receives the TCC signal from IMD 214. The peak-to-peak amplitude of the TCC signal may be within a range from approximately 100 microamps to 10 milliamps (mA) or more, such as within a range from approximately 1 mA to approximately 10 mA. In some examples, the amplitude of the TCC signal may be approximately 3 mA. A TCC signal having a frequency of at least approximately 100 kHz and an amplitude no greater than approximately 10 mA may be unlikely to stimulate nearby tissue, e.g., muscles or nerves, or cause pain or other sensation. For a transmitting electrode vector having an impedance of 200 ohms injecting a current signal having an amplitude of 10 mA peak-to- peak, the voltage signal at the transmitting electrode vector may be 2 Volts peak-to-peak. The voltage developed at the receiving electrode vector may be in the range of 0.1 to 100 millivolts peak-to-peak, as illustrative examples. However, it is contemplated that other frequencies and amplitudes of TCC signals may be used in conjunction with the techniques disclosed herein.

[0095] The TCC circuit 90 may transmit a TCC signal as a modulated signal in some examples. Amplitude modulation (AM), frequency modulation (FM), or digital modulation (DM), such as frequency- shift keying (FSK) or phase-shift keying (PSK) may be performed by TCC circuit 90. In some examples, the modulation can be FM toggling between two frequencies, e.g., toggling between approximately 100-150 kHz and approximately 200-250 kHz. In some examples, the TCC signal has a frequency of 150- 200 kHz and is modulated using FSK modulation at 12.5 kbps. In other examples, a TCC signal having a carrier frequency of 100 kHz is modulated to encode data using binary phase shift keying (BPSK). Balanced pulses of opposite polarity may be used to shift the phase of the TCC signal, e.g., by 180 degrees positively or negatively, and balance the charge injected into the body tissue during the phase shift to minimize the likelihood of interfering with cardiac event sensing operations of sensing circuit 86. Techniques for BPSK modulation of the TCC carrier signal using charge balanced phase shifts are disclosed in U.S. Patent No. 11,110,279 (Roberts, et al.), incorporated herein by reference in its entirety.

[0096] The data carried by modulated or unmodulated TCC signals, e.g., being sent to or received from a second medical device, may include wake up signals, a request to approve an automatic adjustment of a control parameter being made by IMD 214, a confirmation signal following receipt of a reply signal from the second medical device, acknowledgment of a wake up signal transmitted from the second medical device, and a reply signal transmitted in response to a request from the second medical device to approve an adjustment of a control parameter by the second medical device, as examples. [0097] TCC circuit 90 includes TCC receiver 92 to facilitate “two-way” TCC between IMD 214 and a second medical device. A voltage signal that develops on a TCC receiving electrode pair when a TCC signal is transmitted by a second medical device may be received and demodulated by the TCC receiver 92 and decoded by processing circuitry included in control circuit 80. The TCC receiver 92 may include amplifiers, filters, analog- to-digital converters, rectifiers, comparators, counters, a phase locked loop and/or other circuitry configured to detect a signal from a transmitting device and detect and demodulate a modulated carrier signal, which may be transmitted in data packets including encoded data. For example, TCC receiver 92 may include a pre-amplifier and a high-Q filter tuned to the carrier frequency of a carrier signal that is used to transmit wake up signals and/or data signals during a TCC session between two medical devices implanted in or otherwise operatively coupled to the patient. The filter may be followed by another amplifier and a demodulator that converts the received signals to a binary signal representing coded data.

[0098] The circuitry of TCC receiver 92 may include circuitry shared with electrical signal sensing circuitry of sensing circuit 86 in some examples. The filters included in a TCC receiver and cardiac electrical signal sensing circuitry, however, are expected to operate at different passbands, for example, for detecting different signal frequencies. The TCC signals may be transmitted with a carrier frequency in the range of 33 to 250 kHz, in the range of 60 to 200 kHz, or at 100 kHz as examples. Cardiac electrical signals generated by heart 8 are generally less than 100 Hz.

[0099] IMD 214 may transmit a request from TCC transmitter 91 to another medical device when IMD 214 determines that a control parameter adjustment is needed or imminent. IMD 214 may receive a reply signal from the other medical device via TCC receiver 92. A modulated or non-modulated carrier signal may be received by TCC receiver 92 via TCC receiving electrodes (e.g., any of electrodes 224, 226, 228, 230 and/or housing 215) selectively coupled to TCC circuit 90. TCC receiver 92 may include an amplifier, filter and demodulator to pass the demodulated signal, e.g., as a stream of digital values, to control circuit 80 for decoding of the received signal and further processing as needed. [0100] In other examples, TCC receiver 92 may be included in or share sensing circuitry with sensing circuit 86. TCC transmitter 91 may be included in or share signal generating circuitry with therapy delivery circuit 84. In some examples, TCC circuit 90 or the functionality for performing TCC implemented in therapy delivery circuit 84 and sensing circuit 86 may be omitted if IMD 214 is configured to communicate with other medical devices by other means, e.g., using RF communication which may be conducted by a transceiver included in communication circuit 88.

[0101] Memory 82 may be configured to store a variety of control parameters, e.g., therapy control parameters and sensing and detection control parameters among others. Memory 82 may store sensed signals and/or data derived therefrom and any other information related to the monitoring of and therapy delivered to the patient by IMD 214. Memory 82 may store, for example, thresholds and other control parameters used in determining a need for therapy from a sensed physiological signal and control parameters used in controlling therapy delivery. Memory 82 may store communications transmitted to and/or received from another medical device. Memory 82 may store a list of automatic control parameter adjustments (or associated automatic test protocols) that require IMD 214 to transmit a request to another medical device coupled to or implanted in the patient before performing the control parameter adjustment (or associated test protocol).

[0102] IMD 214 may be equipped with one or more other physiological sensors 87 for sensing physiological signals, such as an accelerometer, pressure sensor, temperature sensor, oxygen saturation sensor, gyroscope, heart sound sensor or the like. In some examples, IMD 214 includes a single axis or multi-axis, e.g., three dimensional, accelerometer that may be used for sensing patient posture, sensing patient physical activity level, and/or sensing cardiac mechanical events, e.g., associated ventricular systole, ventricular diastole and/or atrial systole. Control circuit 80 may monitor one or more physiological signals received from sensors 87 for detecting a patient condition or physiological event. Control circuit 80 may generate a notification or alert, record data in memory 82 and/or control therapy delivery circuit 84 based on events or conditions detected from one or more physiological signals sensed by sensing circuit 86, sensors 87 and/or impedance measurements made by IMD 214.

[0103] IMD 214 may be provided with a communication circuit 88 including an antenna and transceiver for RF telemetry communication with another implanted or external device, e.g., with external programming device 50 shown in FIGs. 1 and 2. IMD 214 may perform intrabody communication with another medical device, which may be coimplanted with IMD 214, for exchanging requests and replies relating to an imminent or pending adjustment of a control parameter by IMD 214 (or by the second medical device). Communication circuit 88 may include an oscillator and/or other circuitry configured to generate a carrier signal at the desired frequency. Communication circuit 88 further includes circuitry configured to modulate data on the carrier signal for transmitting request and reply signals sent to another IMD prior to an automatic control parameter adjustment and/or for transmitting stored physiological data, therapy delivery data, and control parameter values to external programming device 50. The modulation of RF communication signals may be, as examples, AM, FM, or DM, such as FSK or PSK. [0104] In some examples, communication circuit 88 is configured to modulate the TCC signal for transmission by TCC transmitter 91. Although communication circuit 88 may be configured to modulate and/or demodulate both RF telemetry signals and TCC signals within the same frequency band, e.g., within a range from approximately 150 kHz to approximately 200 kHz, the modulation techniques for the two types of communication signals may be different. In other examples, TCC transmitter 91 may include a modulator for modulating TCC signals.

[0105] In some examples, communication circuit 88 may include communication circuitry for communicating with external programming device 50 according to a first communication protocol, e.g., BLUETOOTH®, and communication circuitry for communicating with a second medical device according to a second communication protocol, e.g., via MICS or another RF communication protocol operating at a different frequency than the first communication protocol. In still other examples, IMD 214 may communicate with external programming device 50 via first communication circuitry included in communication circuit 88 configured to operate according to an RF communication protocol. IMD 214 may communicate with a second IMD (or other device coupled to the patient) via second communication circuitry included in IMD 214 and configured to operate according to a different mode of communication than RF communication, e.g., using TCC, LEDs, acoustical communication, IR, modulated electrical stimulation pulses (e.g., modulated rate of pacing pulses), or other communication means. It is to be understood that transmission of data between IMD 214 and a second IMD may occur non-concurrently with the transmission of data between IMD 214 and external programming device 50 in some examples. Depending on the communication protocol(s) and communication circuitry used by IMD 214, in some examples, data transmission to and/or data reception from external programming device 50 may occur concurrently with data transmission to and/or data reception from the second medical device. Other examples of medical device communication methods that may be implemented in conjunction with the techniques disclosed herein are generally disclosed in U.S. Patent No. 5,113,859 (Funke), U.S. Patent No. 7,406,105 (DelMain, et al.), U.S. Patent No. 10,357,159 (Schmidt et al.).

[0106] FIG. 5 is a flow chart 300 of a method that may be performed by a medical device system for controlling automatic adjustment of a control parameter by a member of the medical device system according to some examples. For the sake of convenience, the process on the right side of the dashed vertical line of flow chart 300 is described with reference to IMD 214 of FIG. 4 as being the first medical device that is adjusting a control parameter. The process on the left side of the dashed vertical line of flow chart 300 may be performed by a second medical device configured to receive a request signal from the first medical device. With reference to the medical device system of FIG. 2, the first medical device performing the functions on the right side of the dashed vertical line may correspond to ICD 14 in some instances and may correspond to pacemaker 114 in other instances. The second medical device may then correspond to pacemaker 114 in some instance and may correspond to ICD 14 in other instances. In other examples, the first medical device making the control parameter adjustment and the second medical device receiving the request signal from the first medical device may correspond to other types of medical devices, e.g., any of the example medical devices listed herein with no limitation intended.

[0107] For example, the first medical device may be a leadless pacemaker implanted in the right atrium and the second medical device may be a leadless pacemaker implanted in the right ventricle or vice versa. In other examples, one (first or second) of the medical devices may be a cardiac monitor configured to sense ECG, EGM, blood pressure, heart sounds, heart motion, impedance and/or other cardiac signals and the other (second or first) medical device may be a pacemaker (leadless or coupled to one or more leads carrying electrodes) or an ICD (e.g., coupled to transvenous or extra-vascular leads) or vice versa. In still other examples, one or both of the medical devices could be non-cardiac devices, such as neurostimulators, patient monitors, etc.

[0108] With reference to IMD 214 for the sake of example, at block 302, control circuit 80 of IMD 214 determines that a control parameter adjustment is needed. The control parameter is a parameter that is used by control circuit 80 and/or other circuitry of IMD 214 to perform a device function, such as delivery of a therapy, sensing of a physiological signal, detecting physiological event signals (e.g., cardiac event signals), detecting a physiological condition from a sensed signal (e.g., tachyarrhythmia, pulmonary edema, asystole, bradycardia, AV conduction block, or other physiological conditions). In some instances, the control parameter is a parameter that is used and adjusted for performing a test protocol, e.g., for performing a capture test for confirming pacing capture or performing a pacing capture threshold test, measuring lead impedance, testing for atrioventricular (AV) conduction, or determining an impedance measurement as a few examples. The function performed by IMD 214 may be performed by circuitry of IMD 214 which may include any of the circuitry or components described in conjunction with FIG. 4 operating cooperatively to perform the function according to the control parameter. The function performed by circuitry of IMD 214 according to the adjustable control parameter may be performed independently of (e.g., not requiring the presence of) any other medical device implanted in or operating on the patient.

[0109] IMD 214 may be configured to automatically adjust any of a number of control parameters for optimizing the performance of IMD 214 in detecting patient conditions and/or delivering one or more types of therapy for achieving a desired clinical benefit. Various examples of automatically adjustable control parameters are described below. As used herein, an “adjustable control parameter” is a control parameter that can be adjusted by the medical device without necessarily receiving a programming command or instruction from another medical device to initiate the adjustment of the control parameter from a value that is currently in effect to a new, different value. It is recognized, however, that in some cases, IMD 214 may receive a command from external programming device 50 to initiate a test protocol which may involve automatic adjustment of one or more control parameters to multiple test settings to execute the test protocol.

[0110] At block 304, control circuit 80 may determine if a request signal is needed for transmission to a second medical device operating in or on the patient prior to performing the adjustment of the control parameter. One or more adjustable control parameters may be identified as being restricted control parameters that could cause a medical device system conflict if the restricted control parameter is adjusted without requesting approval from at least one other medical device operating in or on the patient. The medical device system conflict could be an unintended functional output of the combination of medical devices in the medical device system operating in or on the patient, e.g., multiple therapies being delivered simultaneously, delivery of a therapy by IMD 214 that causes interference with a sensing, testing or measurement function of a second medical device operating in or on the patient or vice versa, introducing an undesired redundancy of a medical device system function, or introducing a loss of an intended medical device system function.

[0111] In one illustrative example, ICD 14 may determine that a scheduled pacing capture threshold test is pending or imminent at block 302. The pacing capture threshold test can require adjustment of one or more pacing control parameters, e.g., the pacing pulse amplitude, pacing pulse width, a pacing interval (e.g., lower rate interval or AV pacing interval to promote overdrive pacing of the heart) and/or the pacing mode. Any of these pacing control parameters may be flagged in memory 82 as a restricted control parameter that requires a transmitted request signal at block 304 to obtain an approval from another medical device present in or on the patient, e.g., pacemaker 114 when IMD 214 corresponds to ICD 14 or vice versa, to avoid an undesired medical device system interaction or conflict. If pacemaker 114 is delivering ventricular pacing in an atrial synchronous pacing mode, for example, and does not sense pacing pulses delivered by ICD 14, high rate pacing of the ventricles due to both ICD 14 and pacemaker 114 delivering pacing pulses could be a medical device system conflict. In another example, if pacemaker 114 is scheduled to perform a pacing threshold test and a tachyarrhythmia detection is underway by ICD 14, the pacing threshold test could interfere with tachyarrhythmia detection by ICD 14 resulting in a premature detection of a tachyarrhythmia and/or a failed detection of a tachyarrhythmia as a medical device system conflict or undesired outcome.

[0112] Pacing rate interval, pacing mode, pacing pulse output (e.g., pulse amplitude and/or pulse width), AV pacing interval, and pacing electrode vector(s) are examples of therapy delivery control parameters that may be restricted control parameters that require intrabody communication between IMD 214 and one or more other medical devices of the medical device system prior to adjustment of the restricted control parameter by IMD 214. In some instances, the adjustment of a restricted control parameter is performed to execute a test protocol or diagnostic function. In other instances, an adjustment of a restricted control parameter may be performed based on a result of a test protocol, physiological signal analysis or measurement from an acquired signal that has recently or just been performed. In still other instances, an adjustment may be performed as part of an ongoing optimization of therapy delivery, e.g., to provide rate smoothing pacing rate intervals, rate response pacing, pacing mode switching in a patient that experiences intermittent AV block or long AV conduction times, pacing mode and pacing rate adjustments to control ventricular pacing during an atrial tachyarrhythmia, etc.

[0113] For instance, when IMD 214 is configured to deliver biventricular pacing for cardiac resynchronization therapy (CRT), IMD 214 may perform an AV conduction test to determine when AV conduction is intact. When AV block is present, single or biventricular pacing of one or both the right and left ventricles may be delivered. When AV conduction is present, ventricular pacing may be withheld or left ventricular pacing only may be delivered to achieve fusion with the intrinsically conducted right ventricular depolarization. As such, IMD 214 may be configured to adjust an AV pacing interval in accordance with a pacing therapy according to patient need. Based on the AV conduction test result, IMD 214 may switch between a biventricular and single ventricular chamber pacing mode, for example. The second medical device could be performing a test (such as a cardiac pacing capture threshold test, morphology matching analysis or cardiac rhythm analysis) or collecting physiological signal data at the time that IMD 214 is performing a control parameter adjustment according to CRT or another pacing therapy. For example, the second medical device could be collecting a cardiac signal episode for performing a signal morphology analysis for detection of the heart rhythm, establishing a morphology template, or other purposes. Changes in control parameters by IMD 214 could alter the heart rhythm when the second medical device is expecting a stable or unchanging heart rhythm for acquiring and storing a cardiac signal segment, for instance. As such, prior to any of these therapy control parameter adjustments, IMD 214 may determine that a request signal is needed at block 304.

[0114] In yet another example, IMD 214 may be configured to detect atrial tachyarrhythmia and switch the ventricular pacing mode from an atrial synchronous ventricular pacing mode to a non-atrial tracking (asynchronous) pacing mode. During the asynchronous ventricular pacing mode, control circuit 80 may adjust the ventricular pacing interval (increase or decrease) in order to achieve effective ventricular pacing pulse delivery that captures the ventricles to promote a regular ventricular rate during the atrial tachyarrhythmia. IMD 214 may be configured to determine that a request signal is needed prior to switching the pacing mode and/or prior to adjusting the ventricular pacing interval to achieve a relatively high percentage of effectively paced ventricular cycles during the atrial tachyarrhythmia. When the atrial tachyarrhythmia is no longer detected, control circuit 80 may switch back to an atrial synchronous ventricular pacing mode. If the second medical device is currently running a cardiac capture threshold test or capture management test or other test pacing algorithm that involves changing a pacing rate or pacing output, the second medical device function could interfere with the function of IMD 214, e.g., by delivering competing pacing pulses that may pace the heart ahead of IMD 214. Competing pacing rates may confound the results of the algorithms performed by one or both of IMD 214 and the second medical device. As such, control circuit 80 may determine that a request signal is needed prior to switching the pacing mode, adjusting the pacing interval, or adjusting another restricted therapy control parameter at block 304. [0115] Other electrical pulses may be generated by IMD 214 for use in measuring lead or electrode impedance, measuring impedance for monitoring the fluid status of the patient, delivering tachyarrhythmia therapies such as ATP or CV/DF shocks, or delivering tachyarrhythmia induction pulses. Any time that IMD 214 is adjusting a control parameter for delivering an electrical pulse, the control parameter may be identified as a restricted parameter because delivery of an electrical pulse that is either unexpected or delivered according to a different rate or output could interfere with sensing, detection, therapy delivery, or test protocols or diagnostics that may be in process or imminently scheduled to be performed by a second medical device of the medical device system.

[0116] When the second medical device performs critical, life-saving functions (e.g., ventricular pacing or CV/DF shock delivery, and the other medical device does not (e.g., atrial pacing or monitoring for atrial arrhythmias), the first medical device, e.g., an atrial pacemaker, may be configured to transmit a request signal to the second medical device, e.g., a ventricular pacemaker or ICD, prior to making any control parameter adjustment that could interfere with the life-saving function of the second medical device. The second, life-saving medical device may or may not be required to transmit a request signal to the first medical device when a control parameter is being adjusted because any function of the second medical device may be given priority. The second, life-saving medical device may transmit a notification to the first (non-life saving) medical device if a control parameter is being adjusted so that the second medical device has an opportunity to cancel or delay an operation, signal acquisition, test or other function that may be corrupted by a control parameter adjustment performed by the first medical device.

[0117] In still other examples, IMD 214 may determine that a restricted control parameter adjustment is needed at block 302 when IMD 214 determines that an alert signal is to be generated to alert the patient of another caregiver of a detected condition. IMD 214 may be configured to generate an alert signal in response to detecting a physiological condition (e.g., lung edema, atrial fibrillation or other tachyarrhythmia) or a device-related condition (e.g., a need for battery replacement, lead/electrode condition, circuit issue or other device related condition), which may warrant a prescribed action by the patient or a clinician follow-up. The alert signal may be generated by IMD 214 as an audible alert, a vibration or another signal that is perceptible by the patient. When the second medical device includes a sensor for sensing heart sounds, heart motion or other physiological signals, the second medical device sensor signal may be corrupted by an alert signal generated by IMD 214.

[0118] As such, IMD 214 may determine that generating an alert signal is a restricted control parameter that requires a request signal to the second medical device prior to generating the alert signal (e.g., when the alert signal is not due to detection of an urgent life-threatening condition). The request signal may indicate that the alert signal is to be transmitted. The second medical device may temporarily disable a sensor or suspend sensor signal analysis to avoid a system conflict and approve the alert signal generation by IMD 214. Alternatively, the second medical device may transmit a delay or denial signal (at block 356 as further described below) to enable the second medical device to complete a function that involves sensing and storing and/or analyzing a sensor signal that may be corrupted by an alert signal generated by IMD 214 prior to generation of the alert signal. In still other examples, the second medical device may be configured to detect or recognize the alert signal corruption present in the sensor signal so that when the corruption disappears, the second medical device can resume normal sensing and analysis using the sensor signal and ignore the alert signal corruption.

[0119] In some instances, IMD 214 may determine that a restricted control parameter adjustment is needed at block 302 when a functionality of IMD 214 is limited or compromised, e.g., due to remaining capacity of power source 89, remaining storage capacity allocated in memory 82, detection of a lead/electrode issue, or detection of a short circuit or other circuit issue. In order to avoid redundancy of medical device system functionalities, when multiple medical devices are operating in or on the patient, one medical device, e.g., IMD 214, may be enabled to perform a function that is disabled in a second medical device to conserve power and/or storage capacity in the second medical device, avoid redundant alert transmissions and/or avoid generating and transmitting redundant or conflicting data from two different medical devices of the medical device system, which could create confusion or undue burden on a clinician interpreting the data. However, if IMD 214 is enabled to perform a function that is disabled in a second medical device and IMD 214 is reaching end of life of power source 89, limited capacity of memory 82, detects a lead or electrode issue (e.g., a lead fracture or electrode dislodgment), detects a short circuit or other internal circuit issue, or detects another limitation or compromised functionality based on its own device diagnostics, IMD 214 may be configured to disable the function. Adjusting the function from being enabled to being disabled may be a restricted control parameter adjustment in order to avoid loss of an intended medical device system function. As such, IMD 214, may determine that a request signal transmission is needed at block 304 prior to disabling the function. The second medical device may be configured to enable the medical device function in response to the request signal transmission in some instances. Examples of medical device functions that may be disabled by the first medical device and enabled by the second medical device are further described below in conjunction with FIG. 8.

[0120] At block 304, control circuit 80 may determine if a request transmission is needed based on whether or not another medical device is operating in or on the patient and, if so, whether or not the control parameter that is going to be adjusted is a restricted control parameter based on the type or identity of the other medical device. A control parameter that is a restricted control parameter may be flagged in IMD memory 82. In some examples, external programming device 50 may store classifications or labels of control parameters that may be automatically adjusted by IMD 214 (e.g., without a programming command from external programming device 50) as being restricted parameters according to a particular combination of medical devices implanted in the patient (or otherwise operatively coupled to the patient). External programming device memory 53 may store multiple look up tables of restricted control parameters for different possible medical device combinations. For example, when ICD 14 is implanted with pacemaker 114, a table of adjustable control parameters for one or both of ICD 14 and/or pacemaker 114 may be stored in external programming device memory 53 indicating which adjustable control parameters are restricted control parameters for the respective device. When a second device is implanted in the same patient as IMD 214, or when a second medical device is already present in the patient when IMD 214 is being implanted, external programming device 50 may transmit data to IMD 214 notifying IMD 214 of the presence of the second medical device and flagging restricted control parameters for storage in IMD memory 82. [0121] In other examples, IMD 214 may store flags or labels in IMD memory 82 indicating which adjustable control parameters are restricted based on the identification of a co-implanted second device. When IMD 214 is implanted in a patient, IMD 214 may be enabled to communicate with another, previously implanted IMD to detect the presence of the second IMD. When IMD 214 is already present in a patient when a second IMD is implanted, a communication session may be established between the two IMDs so that each IMD can recognize each other and store, in a respective memory, labels or flags of restricted control parameters identified based on the other IMD type. In other examples, IMD 214 may transmit a communication signal to ping other devices that may be implanted or otherwise operatively coupled to the patient. A second medical device may respond to the ping so that IMD 214 can identify the second medical device. Based on the identity of the second medical device, IMD 214 may determine if an adjustable control parameter is a restricted control parameter or not. In some examples, IMD 214 may transmit the identity of the second medical device to external programming device 50 with a query requesting identification of restricted control parameters that may be adjusted by IMD 214.

[0122] When control circuit 80 determines that a control parameter adjustment is needed and the control parameter is not a restricted control parameter (or a second medical device is not presently operating in or on the patient), control circuit 80 may perform the control parameter value adjustment at block 312. In some instances, IMD 214 may have already recently or previously received information from the second medical device regarding programmed control parameter settings and/or relating to scheduled tests performed by the second medical device. The second medical device may transmit information to IMD 214 so that IMD 214 can determine if control parameter adjustment can be performed without requiring transmission of a request signal prior to the adjustment. For example, if IMD 214 has received a programmed schedule from the second medical device for performing a test, such as a capture threshold test schedule as one example, IMD 214 may determine that communication of a request signal is not needed. IMD 214 may delay adjustment of a restricted control parameter so as not to conflict with a scheduled time of a function of the second medical device.

[0123] When control circuit 80 determines that a control parameter adjustment is needed at block 302 and determines that the control parameter is a restricted control parameter at block 304, however, control circuit 80 may initiate communication with a second medical device at block 306. Control circuit 80 may control TCC circuit 90 or communication circuit 88 to transmit a request signal to the second medical device. The request signal may include the control parameter to be adjusted, the current control parameter value, and/or the pending new control parameter value(s) or may indicate a test protocol or measurement to be performed (e.g., pacing capture test, impedance measurement, AV conduction test, etc.) that is an indication to the second medical device of what control parameter adjustments may be involved.

[0124] The second medical device may receive the transmitted request from IMD 214 at block 350. It is to be understood that IMD 214 and the second medical device may be configured to communicate according to a protocol that includes transmitting a wake-up signal or a ping with a return acknowledgment signal to establish a communication session between the two medical devices followed by the transmission of the request signal data. The second medical device may transmit an acknowledgment signal to IMD 214 to confirm receipt of the transmitted request signal. In other examples, the request signal data may be transmitted by IMD 214 one or more times until a reply signal is received from the second medical device.

[0125] At block 352, the second medical device may determine if adjustment of the restricted control parameter is expected to result in an undesired medical device system output or other medical device system conflict. If the second medical device is not performing or about to perform a test or diagnostic that could be interfered with if the control parameter is adjusted by IMD 214, the second medical device may determine no system conflict at block 352. If the second medical device is not performing a sensing, detection or therapy delivery function that could be interfered with if the control parameter is adjusted by IMD 214, the second medical device may determine no system conflict at block 352.

[0126] In some instances, if the second medical device is performing a function that may result in a medical device system conflict, the second medical device may abort the function or adjust its own control parameters in a manner that avoids a medical device system conflict. For example, if the second medical device is performing or about to perform a test, measurement or device diagnostic protocol that could be interfered with when the first medical device adjusts the control parameter, the second medical device may reschedule or cancel the test, measurement or device diagnostic protocol to avoid a failed test or inaccurate measurement. The second medical device, upon rescheduling or canceling its own test, measurement or device diagnostic protocol based on the request signal data received from IMD 214, may subsequently determine no system conflict at block 352.

[0127] If the second medical device determines that a loss of medical device functionality could occur, e.g., if the transmitted request signal is to disable a function of IMD 214, the second medical device may enable the function and subsequently determine no system conflict at block 352. If the second medical device determines that a medical device system conflict could result from the control parameter adjustment, the second medical device may adjust a control parameter of its own to preclude a medical device system conflict. The second medical device may subsequently determine no system conflict at block 352.

[0128] For example, if pacemaker 114 is the second medical device and is operating in an atrial synchronous ventricular pacing mode and receives a request for control parameter adjustment associated with a pacing capture threshold test from ICD 14, pacemaker 114 may switch to a temporary asynchronous ventricular pacing mode (that would result in ventricular pacing inhibition if ICD 14 is pacing at a rate faster than the intrinsic ventricular rate) or temporarily suspend ventricular pacing. This control parameter adjustment by pacemaker 114 would allow ICD 14 to perform the pacing capture threshold test without interference due to pacing pulse delivery by pacemaker 114. Accordingly, in determining if a medical device system conflict would occur if the control parameter adjustment is made by IMD 214, the second medical device may make a control parameter adjustment of its own to preclude or avoid an undesired medical device system output or other conflict and thereby determine no system conflict at block 350.

[0129] When the second medical device determines no system conflict at block 352 (“no” branch), the second medical device may transmit an approval signal at block 354. When IMD 214 receives an approval signal at block 308 in response to the transmitted request, control circuit 80 may perform the control parameter adjustment at block 312. The circuitry of IMD 214 operates cooperatively to perform a function of IMD 214 according to the adjusted control parameter. Circuitry of IMD 214 involved in performing the IMD function according to the adjusted control parameter can include sensing circuitry (e.g., sensing circuit 86 and/or sensors 87, therapy delivery circuitry 84, communication circuitry (e.g., TCC circuit 90 and/or communication circuit 88, and IMD memory 82 operating under the control of control circuit 80.

[0130] In the illustrative examples described in conjunction with FIG. 5, the second medical device is described as being configured to determine if a medical device system conflict is expected to occur in response to the received request signal and the current operation and control parameters of the second medical device. The control circuit 80 of IMD 214 may determine an expected medical device system conflict based on the determination made by the second medical device and the communication signal approving or disapproving the adjustment of the restricted control parameter. However, it is contemplated that, in response to the request signal, the second medical device may transmit information relating to the operation and/or current control parameter settings of the second medical device. The control circuit 80 of IMD 214 may receive the information relating to the current operation and/or control parameter settings of the second medical device and determine if a medical device system conflict is expected to occur if the control parameter is adjusted in IMD 214.

[0131] The control parameter(s) may be adjusted by IMD 214 for controlling a medical device function for an indefinite period of time. The second medical device may or may not alter its own control parameters in order to approve the control parameter adjustment by IMD 214. As described in the above examples, in other instances, the control parameter adjustment made by IMD 214 may be made to control a temporary operation, e.g., to perform a test or diagnostic algorithm, and the second medical device may adjust its own operation temporarily to allow IMD 214 to perform the test without a system conflict. In this case, while not shown explicitly in FIG. 5, it is to be understood that IMD 214 may perform the temporary operation at block 314 and, upon completion, transmit a completion signal back to the second medical device. In this way, the second medical device may restore any control parameter values that were adjusted in the second medical device in order to avoid a system conflict while IMD 214 is performing the temporary operation.

[0132] Referring again to block 352, in some instances the second medical device may determine a medical device system conflict is expected if the requested control parameter adjustment is made by IMD 214. The second medical device may determine that a medical device system conflict will occur if the second medical device is performing a test or device diagnostic protocol that is in progress or takes precedence over the control parameter adjustment by IMD 214. For example, if pacemaker 114 is performing a pacing capture threshold test and receives a request for a pacing control parameter adjustment from ICD 14, pacemaker 114 may determine a system conflict at block 352. Pacemaker 114 may transmit a disapproval signal, e.g., a delay or denial signal, at block 356. IMD 214, which may be ICD 14 or a second leadless pacemaker implanted in the right atrium in this example, may withhold the control parameter adjustment by cancelling or delaying the requested control parameter adjustment at block 310 in response to not receiving an approval signal (“no” branch of block 308).

[0133] In some instances, the system conflict may be temporary if the second medical device is performing a test, measurement or device diagnostic protocol or other temporary operation. In this case, the second medical device may determine a system conflict at block 352 and transmit a disapproval signal as a delay signal at block 356. The delay signal may indicate a delay time after which IMD 214 may perform the requested control parameter adjustment. The delay time may allow the second medical device to complete the test, measurement or device diagnostic protocol or other temporary operation prior to the control parameter adjustment by the IMD 214. The delay time may be 10 seconds, 30 seconds, one minute, several minutes, one hour or other selected time, which may be a default, specified delay time in some examples. IMD 214 may receive the delay signal at block 308 and perform the control parameter adjustment after the specified delay time at block 310.

[0134] It is contemplated that IMD 214 may store a time stamp associated with approval, denial and/or delay signals in memory 82 and may “learn” times of day when the second medical device is likely to be performing a scheduled temporary operation that can be a system conflict associated with a control parameter adjustment made by IMD 214. In this way, at least for temporary operations performed by IMD 214 that involve a control parameter adjustment, control circuit 80 may identify a different time of day or adjust a scheduled time for performing temporary operations, such as capture threshold tests, impedance measurements or other tests, measurements or diagnostic protocols. In this way, control circuit 80 may be configured to learn times of day to avoid making control parameter adjustments to reduce the likelihood of receiving a denial or delay signal in response to a future request signal (and increase the likelihood of receiving an approval signal).

[0135] In some instances, the system conflict may be determined by the second medical device as an undesirable interference with a critical medical device system function being performed by the second medical device, such as sensing of cardiac event signals or detection of a cardiac arrhythmia or delivering a medically necessary, urgent or lifesaving therapy. For example, if the second medical device is in the process of detecting a tachyarrhythmia, the second medical device may transmit a denial signal at block 356. If the second medical device is in the process of delivering a tachyarrhythmia therapy, the second medical device may transmit a denial signal at block 356. If the second medical device is in the process of delivering ventricular pacing in a pacing dependent patient and the control parameter adjustment could disrupt or interfere with the ventricular pacing, the second medical device may transmit a disapproval signal as a denial signal at block 356. In response to a denial signal, IMD 214 may cancel the control parameter adjustment. When a denial signal is received at block 308 (“no” branch), IMD 214 may cancel the control parameter adjustment or reschedule the control parameter adjustment for a later time and transmit a new request signal at the later time.

[0136] At block 310, IMD 214 may store cancelled or delayed adjustments with a time stamp and associated denial or delay signal received from the second medical device. This information may be transmitted to an external device, e.g., external programming device 50, to inform the patient, clinician or other user of a timeline of approved, denied and/or delayed control parameter adjustments. In this way, a user can be made aware of control parameter adjustments that have not been made due to potential system conflicts, including any test algorithms or temporary operations that have not been performed by IMD 214 due to denial or delay signals received from the second medical device. In some cases, a user may reprogram a control parameter or test protocol as not being restricted to enable IMD 214 to perform an associated control parameter adjustment automatically without the restriction of gaining approval from a second medical device first. In other examples, a user may program IMD 214 to perform an automatic control parameter adjustment within a limited set of possible settings of the control parameter (e.g., limited pacing rate intervals, pacing pulse amplitudes, scheduled times of day for making the control parameter adjustments or other limited set of control parameter settings) that could avoid a system conflict and remove the restriction of requiring a request signal (at block 304) for gaining approval from the second medical device prior to an automatic control parameter adjustment.

[0137] FIG. 6 is a flow chart 400 of a method for controlling adjustment of a control parameter in conjunction with performing a test algorithm by a medical device according to some examples. IMD 214, as an example, may be configured to perform a variety of test protocols or procedures for monitoring a patient condition or for determining an updated value of a control parameter used by IMD 214 in performing a device function. At block 402, control circuit 80 may determine that it is time to perform a test algorithm. [0138] Test algorithms may be scheduled to be performed at specified times of day or at scheduled time intervals. For example, control circuit 80 may be configured to perform an impedance measurement (e.g., for monitoring a fluid status, monitoring respiration, and/or monitoring for lead/electrode impedance) each day at a specified time of day or at specified time intervals. Control circuit 80 may be configured to perform a pacing capture test (e.g., to verify capture and/or determine a pacing capture threshold) each day at a specified time of day or at specified time intervals. Control circuit 80 may be configured to perform a test for measuring the AV conduction time, ventricular synchrony (e.g., interventricular activation time difference or QRS width) or other cardiac rhythm tests or measurements at specified time intervals or times of day to enable control circuit 80 to adjust the pacing mode, pacing electrode vector(s), pacing rate, and/or AV pacing interval according to patient need. In some instances, control circuit 80 may acquire cardiac electrical signals for establishing a cardiac signal waveform morphology template and/or compare the morphology of an unknown sensed signal waveform to an established morphology template.

[0139] Test algorithms may be triggered in response to detecting a change in a sensed signal or in a response to a delivered therapy. For example, a pacing capture threshold test may be triggered in response to control circuit 80 detecting a loss of capture. Control circuit 80 may perform an AV conduction time measurement test in response to therapy delivery circuit 84 delivering a threshold number of ventricular pacing pulses. Accordingly, some tests or measurements may be performed by IMD 214 at times that may be unscheduled or unpredictable.

[0140] In some instances, a test algorithm may be triggered in response to receiving a command from an external device, e.g., external programming device 50. For example, IMD 214 may be configured to perform a pacing capture threshold test, an AV conduction test or ventricular synchrony test, a lead impedance test, an underlying (non-paced) rhythm test, electrophysiological tests that may involve inducing a tachyarrhythmia for verifying anti-tachyarrhythmia detection and successful therapy delivery by IMD 214 or determining defibrillation thresholds, or other tests in response to receiving a command from external programming device 50. In this case, control circuit 80 may determine that it is time to perform a test at block 402 in response to receiving a command from external programming device 50.

[0141] At block 404, in response to determining that a scheduled or triggered test is to be performed, control circuit 80 may control communication circuit 88 or TCC circuit 90 to transmit a request signal. As generally described above in conjunction with FIG. 5, a second medical device that is implanted or otherwise operatively coupled to the patient may receive the transmitted request signal, acknowledge the request signal, determine if a medical device system conflict could occur if the test is performed during the current operations being performed by the second medical device, and transmit a reply signal based on the determination. The second medical device may transmit an approval signal, a delay signal or a denial signal in various instances. In some examples, the second medical device may be configured to transmit an approval signal or a disapproval signal. [0142] At block 406, control circuit 80 of IMD 214 receives the reply signal from the second medical device, via communication circuit 88 or TCC circuit 90. When the reply signal is an approval signal, control circuit 80 performs the pending test at block 408. If the reply signal received at block 406 is not an approval signal, control circuit 80 may cancel or delay the test at block 410. In some instances, the test is cancelled and may be performed the next time the test is scheduled or triggered as determined at block 402. In other instances, the test may be delayed, e.g., by a specified time interval. When control circuit 80 delays the test, e.g., by one minute, five minutes, one hour or other specified time interval, control circuit 80 may return to block 402 after the specified time interval and repeat a request signal transmission to verify that performing the delayed test is approved by the second medical device signal.

[0143] It is contemplated that when the test is triggered in response to receiving a command from an external programming device 50, communication circuit 88 may transmit a notification signal to external programming device 50 notifying the external device 50 of the test status (e.g., approved, delayed or cancelled) and, if disapproved by the second medical device, of a potential system conflict. In some cases, a user may use the external programming device 50 to transmit an override signal that causes IMD 214 to perform the test without receiving approval from the second medical device or the user may change the programming of the second medical device to enable the test to proceed with an approval signal from the second medical device.

[0144] FIG. 7 is a flow chart 450 of a method for controlling adjustment of a control parameter in conjunction with performing a test algorithm by a medical device according to another example. Identically numbered blocks in FIG. 7 correspond to like-numbered blocks in the flow chart 400 of FIG. 6 that are described above. Depending on the test that is performed at block 408 by IMD 214, control circuit 80 may utilize the test result to automatically adjust a control parameter used for controlling IMD functions. For example, IMD 214, based on the test result, may adjust a control parameter for use in controlling a function of IMD 214 until the test is performed again. For instance, if the test is a pacing capture threshold test, control circuit 80 may determine the pacing capture threshold has changed since a previous pacing capture threshold test. Based on the newly determined pacing capture threshold, control circuit 80 may determine a new pacing pulse amplitude, e.g., a new pacing pulse amplitude or new pacing pulse width. In another example, if the test is an AV conduction test, control circuit 80 may determine that the intrinsic AV conduction time has changed since a previous AV conduction test. Control circuit 80 may determine that pacing mode switching criteria is met (e.g., to switch between an AV synchronous (e.g., DDD or VDD) pacing mode and an asynchronous (e.g., DDI or VDI) pacing mode). Control circuit 80 may determine that the AV pacing interval should be adjusted based on the new AV conduction time measurement and/or a sensed or paced heart rate. In other examples, based on an AV conduction test, ventricular synchrony test, a lead/electrode impedance test or a pacing capture threshold test, control circuit 80 may determine that a pacing therapy and/or pacing electrode vector configuration should be adjusted to a different pacing therapy and/or pacing electrode vector configuration.

[0145] After performing the test at block 408, control circuit 80 may determine that a control parameter adjustment is warranted based on the outcome of the test at block 412. In some examples, control circuit 80 may adjust a control parameter at block 418 based on the outcome of the test, e.g., based on a measurement performed during the test, and return to block 402 to wait for the next scheduled or triggered test time. The control parameter adjustment may be performed at block 418 without transmission of another request signal after receiving approval from the second medical device for performing the test. However, in some examples, the control parameter being adjusted may be a restricted control parameter. As such, control circuit 80 may determine if a request signal transmission is required at block 413 after determining that a control parameter adjustment is warranted based on the test performed.

[0146] For example, an adjustment of a therapy delivery control parameter (e.g., an electrical stimulation pulse amplitude, pulse width, pacing interval, pacing electrode vector(s) or pacing mode) may be required based on the results of the performed test. The therapy delivery control parameter that is determined to require an adjustment may be a restricted control parameter that requires transmission of a request signal. In other examples, a test interval used to schedule the next test may be adjusted based on the outcome of the test. For example, when an AV conduction test is performed and AV block is detected, the interval for scheduling the next AV conduction test may be increased, e.g., doubled, so that AV conduction tests are not performed repeatedly at relatively short intervals during AV conduction block. The time interval that is adjusted for scheduling the next test may not be a restricted control parameter. [0147] When the control parameter being adjusted is not a restricted control parameter, control circuit 80 may determine that transmission of a request signal is not required at block 413. Control circuit 80 may adjust the control parameter at block 418. Control circuit 80 may return to block 402 to wait for the next scheduled or triggered test and may operate according to the adjusted control parameter in the meantime.

[0148] When the control parameter being adjusted is a restricted control parameter, control circuit 80 may determine that a request signal transmission is required at block 413. Communication circuitry of IMD 214, e.g., communication circuit 88 or TCC circuit 90, may transmit the request signal at block 414. If an approval signal is received from a second medical device operating in/on the patient (“yes” branch of block 416), control circuit 80 may adjust the control parameter at block 418. If the reply signal received from the second medical device is not an approval signal, e.g., a denial or delay signal, control circuit 80 may cancel or delay control parameter adjustment at block 420.

[0149] In the example shown, the process of flow chart 450 returns to block 402 to wait for the next scheduled or triggered test to be performed after delaying or cancelling the control parameter adjustment at block 420. However it is to be understood that when control circuit 80 delays the control parameter adjustment at block 420, control circuit 80 may not wait for a subsequently scheduled or triggered test to be performed. Control circuit 80 may wait for a specified delay time interval, e.g., one minute, one hour, or one day, and return to block 414 to transmit the request signal again to determine if the control parameter adjustment is approved by the second medical device. When an approval signal is received after one or more delays in adjusting the control parameter, control circuit 80 may adjust the control parameter at block 418. It is further contemplated that when a test is cancelled or delayed, control circuit 80 may store a time stamp in memory 82 and/or transmit a notification to external programming device 50 to alert a clinician or other user of any delayed or cancelled tests.

[0150] FIG. 8 is a flow chart 500 of a method for controlling an adjustment of a control parameter of a medical device using intrabody communication according to another example. In some cases, two or more medical devices operating in a medical device system in or on a patient may each be capable of independently performing a common function, which may be related to monitoring for a patient condition, storing data, delivering a therapy, generating alerts or notifications, etc. When two or more devices co- implanted in a medical device system are each capable of performing a common function, one medical device of the medical device system may be programmed to have priority control over the common function. A second medical device of the medical device system may be available for backup control over the common function. The common function may be enabled in the first device and disabled in the second device to conserve power, processing requirements, memory requirements, and avoid redundant or conflicting data or redundant alert generations in the second medical device.

[0151] The medical device system of FIG. 2 is an example of a medical device system including at least two IMDs that may each be capable of performing a common function, e.g., a cardiac pacing capability. Pacemaker 114 may be programmed to have priority control over all or some cardiac pacing therapies for delivering bradycardia pacing, ATP, and/or in some instances post-shock pacing for example. ICD 14 may be programmed to have all pacing functions disabled and may operate to detect tachyarrhythmias and deliver high voltage CV/DF shocks but cedes priority to pacemaker 114 for providing pacing functionality in the medical device system. ICD 14 is available, however, for providing backup control of cardiac pacing if pacemaker 114 is near or reaches end of life of its power source or can no longer capture the heart due to electrode dislodgement or another electrode or circuit issue. Pacemaker 114 may determine that its own pacing capabilities may be limited or compromised and cede priority of pacing control to ICD 14 according to the method shown in FIG. 8, as further described below.

[0152] In another example, ICD 14 may have priority control over the detection of arrhythmias and storage of cardiac signal episodes in its own memory for later transmission to external programming device 50. Detected arrhythmias may include atrial and/or ventricular arrhythmias and may include bradycardia, a long pause or ventricular asystole as well as tachyarrhythmias such as atrial flutter, atrial fibrillation, ventricular tachycardia or ventricular fibrillation. Any of a number of arrhythmia detection methods may be implemented in ICD 14 and/or pacemaker 114 (or another medical device of the medical device system) based on sensed cardiac event intervals and/or signal morphology analysis for example. Pacemaker 114, being physically smaller, may have more limited processing power, memory capacity, power capacity and, being implanted deeper in the patient’s body, more limited communication with an external device for transmitting large amounts of data. [0153] Accordingly, ICD 14 may have priority control over storage of cardiac signal data and transmission of data relating to detected arrhythmia episodes when co-implanted with pacemaker 114. While pacemaker 114 may be sensing ventricular event signals (e.g., R- waves) for determining a need for pacing, pacemaker 114 may not be programmed to detect ventricular arrhythmias and/or store episodes of a sensed cardiac electrical signal in response to detecting a ventricular arrhythmia episode. In other examples, pacemaker 114 may be configured to detect a ventricular tachyarrhythmia episode to control when ATP is delivered, but storage of a cardiac electrical signal episode during the tachyarrhythmia detection may be programmed off (disabled) in pacemaker 114. If ICD 14 detects an issue (e.g., reaching a threshold capacity of its power source or a threshold storage capacity of allocated memory) that limits its capability in detecting an arrhythmia episode and/or storing an arrhythmia episode and/or transmitting data to an external device, ICD 14 could cede priority for the cardiac electrical signal episode storage function to pacemaker 114. When ICD 14 detects an issue that could impair or limit its ability to detect, store and/or transmit arrhythmia episodes, ICD 14 could cede priority control to pacemaker 114 for storing arrhythmia episodes for later transmission to an external device according to the methods of FIG. 8 as further described below. While cardiac signal episodes are given as examples here it is to be understood that signal episodes from any sensors included in the medical device system may be stored in a medical device memory for transmission to external programming device 50. Other examples of sensors and physiological signals include but are not limited to any of those listed herein.

[0154] In still other examples, one medical device may be implanted relatively deep in the patient’s body and one medical device more superficially in the patient’s body making communication with external programming device 50 more reliable and efficient. In the illustrative example of FIG. 2, ICD 14 may have a larger power supply, larger physical volume for containing communication circuitry, and/or be implanted more superficially than pacemaker 114 such that ICD 14 may have priority control over communication functions with an external device, e.g., external programming device 50. For instance, ICD 14 may have priority control over generating alerts or notifications that are transmitted to an external programing device 50. ICD 14 may have priority control over transmitting physiological data, therapy delivery data and/or device diagnostic data to external programming device 50. ICD 14 may function as a relay communication device between pacemaker 114 and external programming device 50. As such, data transmitted from ICD 14 to external programming device 50 may include data that ICD 14 receives from pacemaker 114. Data received by ICD 14 from external programming device 50 may be transmitted to pacemaker 114. In this way, the power required for pacemaker 114 to send data to and receive data from external programming device 50 may be reduced.

[0155] In some instances, a test algorithm may be performed by IMD 214 of FIG. 4 in response to receiving a command from an external device, e.g., external programming device 50. Upon receiving the test command, IMD 214 may determine that a function may need to be disabled in order to perform the test. In other instances, IMD 214 may receive a command from external programming device 50 to temporarily suspend a function or operate in a temporary operating mode that requires a function to be disabled. For example, a clinician may perform an in-office underlying rhythm test or other clinical evaluations that require temporarily suspending cardiac pacing, switching the pacing mode to another temporary pacing mode different than its permanent pacing mode, or setting the pacing rate to a minimum pacing rate. If IMD 214 has priority control over detecting arrhythmias and storing cardiac signal episodes, IMD 214 may suspend the episode storage during the test or temporary operating mode because a period of asystole or a long ventricular pause, for example, may be the result of the temporary operating mode. IMD 214 may transmit a request signal to a second medical device to inform the second medical device to ensure that the second medical device does not deliver backup pacing pulses in the absence of expected pacing delivered by IMD 214. If the second medical device has priority control over cardiac signal episode storage, IMD 214 may transmit a notice to the second medical device to temporarily suspend cardiac signal episode storage.

[0156] The flow chart 500 of FIG. 8 is described as being performed by IMD 214 (right side of the vertical dashed line in communication with a second medical device implanted in or otherwise operatively coupled to the patient. Functions that may be performed by the second medical device of the medical device system are shown on the left side of the vertical dashed line. In some instances, IMD 214 and the functions performed on the right side of the vertical dashed line may correspond to ICD 14 with the second medical device being pacemaker 114 or another medical device implanted in or otherwise operatively coupled to the patient. In other instances, IMD 214 and the functions performed on the right side of the vertical dashed line may correspond to pacemaker 114 with the second medical device being ICD 14 or another medical device implanted in or otherwise operatively coupled to the patient. In still other examples, IMD 214 and the second medical device may correspond to any of the example medical devices listed herein, with no limitation intended.

[0157] It is to be understood that the role of having priority control over a medical device system function and performing the operations on the right side of the dashed vertical line of FIG. 8 and the role of providing reserve or back up control over the medical device system function and performing the operations on the left side of the dashed vertical line of flow chart 500 may be reversed and may change back and forth between two medical devices of a medical device system at various times during the operational life of each device. The device having the role of priority control over a medical device system function may be programmed by a clinician and may be dependent on the particular combination of medical device members of the medical device system.

[0158] At block 502, IMD 214 may determine the need to disable a medical device system function that IMD 214 has priority control over. The medical device system function may be a therapy delivery function, signal analysis function, a data storage function, or an alert transmission function as examples and may be any of the example functions described herein or combinations thereof. IMD 214 may perform a device diagnostic protocol or other measurement to determine the need to disable the medical device system function. [0159] For example, IMD 214 may perform a diagnostic test for determining an estimated capacity of power source 89 and determine that the remaining estimated capacity of power source 89 has reached a threshold capacity. The threshold capacity may correspond to a specified voltage threshold, an elective replacement capacity or an estimated time to end of life of power source 89 that is less than a threshold time (e.g., days, weeks or months). The battery drain required to continue performing the medical device system function may prevent IMD 214 from performing other critical functions, e.g., therapy delivery functions, prior to reaching the power source end of life. Examples of methods for determining a remaining life or capacity of power source 89 that may be performed at block 502 for determining a need to disable a medical device system function are generally disclosed in U.S. Patent No. 6,671,552 (Merritt, et al., filed October 2, 2001) and in U.S. Patent Application Publication No. 2021/0187305 (Pender, filed December 4, 2020), the entire content of both of which incorporated herein by reference. [0160] In other examples, IMD 214 may perform a test algorithm that includes processing and analysis of sensed physiological signals for detecting a sensing issue, which may be undersensing of cardiac event signals, oversensing of cardiac event signals, or noise corruption of a sensed physiological signal. A sensing issue may be detected by analyzing a physiological signal, e.g., a cardiac electrical signal, for detecting sensed event intervals, signal amplitudes, signal morphology, or other features of the signal that are indicative of oversensing, undersensing, noise corruption or poor signal quality. A sensing issue may prevent IMD 214 from performing the medical device function effectively. Examples of methods for detecting a sensing issue due to oversensing of cardiac event signals that may be performed at block 502 for determining a need to disable a medical device system function are generally disclosed in U.S. Patent No. 9,597,525 (Cao, et al., filed May 6, 2015) and in U.S. Patent No. 11,135,441 (Zhang et al., filed June 24, 2019), the entire content of both incorporated herein by reference. Example methods for detecting noise corruption in a sensed physiological signal that may performed at block 502 for determining a need to disable a medical device system function are generally disclosed in U.S. Patent No. 8,386,024 (Gunderson, et al., filed June 2, 2009) and in U.S. Patent No. 10,750,970 (Stadler, et al., filed December 17, 2018), the entire content of both incorporated herein by reference. Examples of signal quality metrics that may be determined during a diagnostic test for detecting a sensing issue that may be performed at block 502 for determining a need to disable a medical device system function are generally disclosed in U.S. Patent No. 7,496,409 (Greenhut et al., filed February 24, 2009) and in U.S. Patent No. 7,904,153 (Greenhut, et al., filed March 8, 2011), the entire content of both incorporated herein by reference.

[0161] In other examples, IMD 214 may perform an electrical diagnostic test for detecting an internal circuit issue occurring in the circuitry enclosed by housing 215 or the connector block or header coupled to housing 215. An internal circuit issue may be detected by measuring an impedance, voltage or current for detecting a leakage current pathway due to a short circuit or insulation breach. An internal circuit issue may be detected by performing an impedance, voltage or current measurement for detecting open circuit, which may be due to a faulty electrical connection. A detected circuit issue may prevent IMD 214 from performing the medical device function effectively. Examples of methods for detecting a circuit issue that may be performed at block 502 for determining a need to disable a medical device system function are generally disclosed in U.S. Patent No. 10,220,204 (Stanslaski et al., filed March 5, 2019), the entire content incorporated herein by reference.

[0162] IMD 214 may determine that the function needs to be disabled within IMD 214 because of a remaining capacity of power source 89, a measured lead or electrode impedance, detection of a circuit issue, remaining storage capacity of memory 82, detection of noise in sensed physiological signals, suspected undersensing or oversensing of cardiac event signals, failed communication transmissions, or other detected limitation or impairment of the functionality of IMD 214. A variety of diagnostic tests, not limited to the examples given above, may be performed by IMD 214 for determining when a medical device system function needs to be disabled. In some cases, control circuit 80 may determine that a function needs to be disabled in response to receiving a signal from external programming device 50.

[0163] In response to determining the need to disable the function of IMD 214, control circuit 80 may determine if a request signal is needed at block 504. In some cases, the function may only be available in IMD 214 when other co-implanted devices are not capable of performing the same function. In other instances, the function may not be a critical function that requires a reserve or back up device to assume control of. If a request is not needed, control circuit 80 may disable the function at block 512. Control circuit 80 may generate an alert or notification to be transmitted by communication circuitry of IMD 214 to an external device, e.g., external programming device 50, to notify the clinician or other caregiver or technician that the function has been disabled.

[0164] When a second medical device that is capable of performing the medical device function is available, control circuit 80 may determine that request signal is needed at block 504. The communication circuitry of IMD 214, e.g., TCC circuit 90 or communication circuit 88, may transmit a request signal to the second medical device at block 506. It is to be understood that in some examples, the request may be transmitted to multiple medical devices operating in/on the patient when more than two medical devices are members of the medical device system. The second medical device may receive the request at block 550 and may transmit an acknowledgment signal. At block 552, the second medical device may determine if the function to be disabled by IMD 214 is available to be performed by the second medical device. If so, the second medical device may enable the function at block 556 to assume priority control of the medical device system function. The second medical device may transmit an approval/notice signal at block 558 to notify IMD 214 that the function has been enabled by the second medical device and can be disabled by IMD 214.

[0165] IMD 214 may receive the approval/notice signal at block 508, and control circuit 80 may disable the function in IMD 214 at block 512. In this way, the medical device system including IMD 214 and a second medical device may continue to perform the medical device system function seamlessly by handing off the function from IMD 214 to the second medical device when the ability to perform the function by IMD 214 may be compromised. In this way, the longevity of the medical device system function can be extended in a medical device system including multiple member devices each capable of independently performing the function by conserving the power source and memory capacity in a second medical device until a first medical device cedes priority control over the medical device system function.

[0166] In some circumstances, the second medical device may determine that the function being disabled by IMD 214 is either currently not available for performing by the second medical device or the second medical device is not capable of performing the function. The second medical device may be performing a test, in the process of detecting a tachyarrhythmia or other physiological condition, delivering a therapy that prevents the second medical device from immediately enabling the function in the second medical device. In other instances, the second medical device may be capable of performing the function but may be reaching end of life of its own power source, have limited memory storage capacity remaining or another detected limitation that prevents the second medical device from assuming priority control of the medical device system function. In some instances, therefore, the second medical device may transmit a denial signal at block 554 indicating that the function is not currently available in the second medical device.

[0167] IMD 214 may receive the denial signal at block 508. The response to the denial signal performed by IMD 214 may depend on the remaining power capacity, memory capacity, or other condition that IMD 214 detected as the cause for having to disable the function. The response to the denial signal may depend on what the function is that is being disabled. In some instances, IMD 214 may delay or cancel disabling the function at block 510 if the function is a critical function, e.g., a therapy delivery function, and the second medical device is not able to assume priority control. Control circuit 80 may generate an alert to be transmitted to an external device, e.g., external programming device 50, at block 514 to notify the patient, clinician or another caregiver that the medical device system function is continuing but may be terminated or imminently unavailable if a device replacement or other intervention is not performed. In some instances, the function may remain enabled in IMD 214, and IMD 214 may repeat the request signal transmission to determine if a second medical device is available for assuming priority control of the function at a later time point.

[0168] In other examples, IMD 214 may respond to the denial signal received at block 508 by disabling the function and generating an alert for transmission to external programming device 50 (or another external device) at block 514 to notify the patient, clinician or another caregiver or a technician that the medical device functionality is no longer being performed. IMD 214 may not have the ability to continue performing the medical device system function even when the second medical device is unable to assume control of the function. While IMD 214 is shown to transmit an alert at block 514 indicating the status of the medical device system function, it is to be understood that the communication circuitry of IMD 214 and/or the communication circuitry of the second medical device may be configured to transmit a notification relating to the medical device system function being disabled in the first medical device and/or enabled in the second medical device.

[0169] In the foregoing examples, the control circuit 80 of IMD 214 is described as determining a need to disable a medical device system function at block 502 that is currently being performed by IMD 214. In other examples, however, control circuit 80 may determine that the medical device system function that needs to be disabled is currently being performed by a second medical device of the medical device system. For instance, when IMD 214 receives a command from external programming device 50 to operate in a temporary mode, e.g., disable pacing or other functions, to enable an in-office underlying rhythm test or other electrophysiological testing to be performed, IMD 214 may determine that as a part of or in addition to its own temporary operation, a medical device system function, such as storing cardiac signal episodes, should be disabled. If IMD 214 does not currently have priority control over storage of cardiac signal episodes, control circuit 80 may determine that a request signal is needed at block 504 to disable the medical device system function. [0170] Control circuit 80 may transmit a request signal at block 506, in this case requesting that a medical device system function that the second medical device has priority control over be disabled. The second medical device may receive the transmitted request at block 550 as a notice that the medical device system function needs to be disabled. At block 552, the second medical device may determine that the function is currently enabled and, in this case, instead of enabling the function as shown in block 556 of FIG. 8, disable the medical device system function in response to the request signal received from IMD 214. The second medical device may transmit an approval at block 558 indicating that the function has been disabled.

[0171] At block 508, control circuit 80 may receive the approval signal and, in this case, may not need to take further action. In some examples, IMD 214 may transmit a notification to the external programming device 50 that the medical device system is ready for the test to proceed, that temporary operating modes are confirmed, and/or that the medical device system function has been disabled. The second medical device may disable the medical device system function for a specified time interval and then automatically reenable the medical device system function. In other examples, when the test is completed, IMD 214 may receive a command from external programming device 50 to restore its normal or permanent operation mode. Control circuit 80 may determine that the medical device system function can be restored and transmit a notification to the second medical device to re-enable the medical device system function and continue priority control over the system function.

[0172] Further disclosed herein is the subject matter of the following examples:

[0173] Example 1. A medical device system comprising a first medical device including first circuitry configured to perform a medical device system function, a first communication circuit and a first control circuit. The first control circuit being configured to detect a condition for disabling performing the medical device system function by the first circuitry, in response to detecting the condition, transmit via the first communication circuit a communication signal to a second medical device capable of performing the medical device system function, and disable the performing of the medical device system function by the first circuitry. The first medical device may include a power source configured to provide power to the first circuitry, the first communication circuit and the first control circuit. [0174] Example 2. The medical device system of example 1 wherein the first control circuit is further configured to detect the condition for disabling the medical device system function by determining an estimated capacity of the power source and determining that the estimated capacity of the power source has reached a threshold capacity.

[0175] Example 3. The medical device system of any one of examples 1 — 2 wherein the first medical device further comprises a memory for storing data relating to the medical device system function. The first control circuit being further configured to detect the condition for disabling the medical device system function by determining an available capacity of the memory for storing the data relating to the medical device function and determining that the available capacity of the memory has reached a threshold capacity. [0176] Example 4. The medical device system of any one of examples 1 — 3 wherein the first control circuit is further configured to detect the condition for disabling the medical device system function by performing an electrical diagnostic test and detecting the condition for disabling the medical device system function by detecting a circuit issue based on the electrical diagnostic test.

[0177] Example 5. The medical device system of any one of examples 1 — 4 wherein the first control circuit is further configured to detect the condition for disabling the medical device system function by performing an impedance measurement and detecting the condition for disabling the medical device system function based on the impedance measurement.

[0178] Example 6. The medical device system of any one of examples 1 — 5 wherein the first circuitry includes a sensing circuit configured to sense at least one physiological signal and a memory. The first circuitry being configured to perform the medical device system function by sensing the at least one physiological signal and storing an episode of the at least one physiological signal in the memory.

[0179] Example 7. The medical device system of any one of examples 1 — 6 wherein the first circuitry further comprises a sensing circuit configured to sense at least one physiological signal, a memory and processing circuitry configured to detect at least one physiological condition based on the at least one sensed physiological signal. The first circuitry being further configured to perform the medical device function by detecting the at least one physiological condition and storing data associated with detecting the at least one physiological signal in the memory. [0180] Example 8. The medical device system of any one of examples 1 — 7 wherein the first circuitry further comprises a therapy delivery circuit configured to perform the medical device system function by delivering a therapy.

[0181] Example 9. The medical device system of example 8 wherein the therapy delivery circuit is configured to deliver the therapy by delivering one or more cardiac electrical stimulation pulses.

[0182] Example 10. The medical device system of any one of examples 1 — 9 wherein the first circuitry configured to perform the medical device system function further comprises a second communication circuit configured to transmit data to an external medical device. [0183] Example 11. The medical device system of any one of examples 1 — 10 further comprising the second medical device. The second medical device including second circuitry configured to perform the medical device system function, a second communication circuit configured to receive the communication signal and a second control circuit configured to enable the second circuitry to perform the medical device system function in response to receiving the communication signal via the second communication circuit.

[0184] Example 12. The medical device system of example 11 wherein at least one of the first communication circuit or the second communication circuit is further configured to transmit a notification relating to the medical device system function being disabled in at least the first medical device.

[0185] Example 13. The medical device system of any one of examples 1 — 12 wherein the second control circuit is further configured to, in response to receiving the communication signal via the second communication circuit, determine that criteria are met for the second circuitry to perform the medical device system function. The second control circuit being configured to enable the second circuitry to perform the medical device system function in response to the criteria being met for the second circuitry to perform the medical device system function.

[0186] Example 14. The medical device system of any one of examples 1 — 10 further comprising the second medical device. The second medical device including second circuitry configured to perform the medical device system function, a second communication circuit configured to receive the communication signal and a second control circuit. The second control circuit being configured to, in response to receiving the communication signal via the second communication circuit, determine that criteria are not met for the second circuitry to perform the medical device system function. The second communication circuit being further configured to transmit a denial signal in response to the second control circuit determining that the criteria are not met for the second circuitry to perform the medical device system function.

[0187] Example 15. The medical device system of example 14 wherein the first communication circuit is further configured to receive the denial signal. The first control circuit being further configured to delay disabling the medical device system function being performed by the first circuitry in response to receiving the denial signal.

[0188] Example 16. The medical device system of any one of examples 1 — 15 wherein the first communication circuit comprises at least one of a tissue conductance communication circuit or a radio frequency communication circuit.

[0189] Example 17. A method including performing a medical device system function by a first medical device, detecting a condition for disabling performing the medical device system function by the first medical device and, in response to detecting the condition, transmitting a communication signal to a second medical device capable of performing the medical device system function. The method may further include disabling the performing of the medical device system function by the first medical device.

[0190] Example 18. The method of example 17 wherein detecting the condition for disabling the medical device system function comprises determining an estimated capacity of a power source of the first medical device and determining that the estimated capacity of the power source has reached a threshold capacity.

[0191] Example 19. The method of any one of examples 17 — 18 wherein performing the medical device function comprises storing data relating to the medical device system function in a memory of the first medical device. The method further including detecting the condition for disabling the medical device system function by determining an available capacity of the memory for storing the data relating to the medical device function and determining that the available capacity of the memory has reached a threshold capacity. [0192] Example 20. The method of any one of examples 17 — 19 wherein detecting the condition for disabling the medical device system function comprises performing an electrical diagnostic test and detecting the condition for disabling the medical device system function by detecting a circuit issue based on the electrical diagnostic test. [0193] Example 21. The method of any one of examples 17 — 20 wherein detecting the condition for disabling the medical device system function includes performing an impedance measurement and detecting the condition for disabling the medical device system function based on the impedance measurement.

[0194] Example 22. The method of any one of examples 17 — 21 wherein performing the medical device system function includes sensing at least one physiological signal and storing an episode of the at least one physiological signal a memory of the first medical device.

[0195] Example 23. The method of any one of examples 17 — 22 wherein performing the medical device system function comprises sensing at least one physiological signal, detecting at least one physiological condition based on the at least one sensed physiological signal and storing data associated with the at least one detected physiological signal in a memory of the first medical device.

[0196] Example 24. The method of any one of examples 17 — 23 wherein performing the medical device system function comprises delivering a therapy.

[0197] Example 25. The method of example 24 wherein delivering the therapy comprises delivering one or more cardiac electrical stimulation pulses.

[0198] Example 26. The method of any one of examples 17 — 25 wherein performing the medical device system function comprises transmitting data to an external medical device. [0199] Example 27. The method of any one of examples 17 — 26 further comprising receiving the communication signal by the second medical device and enabling performing the medical device system function by the second medical device in response to receiving the communication signal.

[0200] Example 28. The method of any one of examples 17 — 27 further comprising transmitting a notification of the medical device system function being disabled in at least the first medical device.

[0201] Example 29. The method of any one of examples 17 — 28 further comprising determining that criteria are met for the second medical device to perform the medical device system function and enabling performing the medical device system function by the second medical device in response to the criteria being met.

[0202] Example 30. The method of any one of examples 17 — 26 further including receiving the communication signal by the second medical device and, in response to receiving the communication signal, determining that criteria are not met for performing the medical device system function by the second medical device. The method further including transmitting a denial signal in response to determining that the criteria are not met for the performing the medical device system function by the second medical device. [0203] Example 31. The method of example 30 further including receiving the denial signal by the first medical device and delaying disabling the medical device system function being performed by the first medical device in response to receiving the denial signal.

[0204] Example 32. The method of any one of examples 17 — 31 further comprising transmitting the communication signal as one of a tissue conductance communication signal or a radio frequency communication signal.

[0205] Example 33. A non-transitory computer readable medium storing a set of instructions that, when executed by processing circuitry of a medical device system, cause the medical device system to perform a medical device system function by a first medical device of the medical device system, detect a condition for disabling performing the medical device system function by the first medical device and, in response to detecting the condition, transmit a communication signal to a second medical device capable of performing the medical device system function. The instructions may further cause the medical device system to disable the performing of the medical device system function by the first medical device.

[0206] Example 34. A medical device system including a first medical device and a second medical device. The first medical device including first circuitry configured to perform a medical device system function, a first communication circuit, and a first control circuit. The first control circuit being configured to detect a condition for disabling performing the medical device system function by the first circuitry and, in response to detecting the condition, transmit via the first communication circuit a communication signal. The first control circuit may be further configured to disable the performing of the medical device system function by the first circuitry. The second medical device may include second circuitry configured to perform the medical device system function, a second communication circuit configured to receive the communication signal and a second control circuit. The second control circuit being configured to enable the second circuitry to perform the medical device system function in response to receiving the communication signal via the second communication circuit.

[0207] Thus, various examples of a medical device system have been presented in the foregoing description with reference to illustrative diagrams and flow charts shown in the drawings. It should be understood that, depending on the example, certain acts or events of any of the methods described herein can be performed in a different sequence, may be added, merged, or left out altogether (e.g., not all described acts or events are necessary for the practice of the method). Moreover, in certain examples, acts or events may be performed concurrently, e.g., through multi-threaded processing, interrupt processing, or multiple processors, rather than sequentially. In addition, while certain aspects of this disclosure are described as being performed by a single device, circuit or component for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of devices, circuits or components associated with, for example, a medical device system and/or a single circuit or component may perform multiple functions that are represented as separate circuits or components in the accompanying drawings.

[0208] In one or more examples, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions or code on a computer-readable medium and executed by a hardware -based processing unit. Computer-readable media may include computer-readable storage media, which corresponds to a tangible medium such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other non- transitory computer-readable medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer).

[0209] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the terms “processor” and “processing circuitry” as used herein may refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein. Also, the techniques could be fully implemented in one or more circuits or logic elements. [0210] Thus, a medical device system has been presented in the foregoing description with reference to specific examples. It is to be understood that various aspects disclosed herein may be combined in different combinations than the specific combinations presented in the accompanying drawings. It is appreciated that various modifications to the referenced examples may be made without departing from the scope of the disclosure and the following claims.

Claims

WHAT IS CLAIMED IS:

1. A medical device system comprising a first medical device, wherein the first medical device comprises: first circuitry configured to perform a medical device system function; a first communication circuit; a first control circuit configured to: detect a condition for disabling performing the medical device system function by the first circuitry; in response to detecting the condition, transmit via the first communication circuit a communication signal to a second medical device capable of performing the medical device system function; and disable the performing of the medical device system function by the first circuitry; and a power source configured to provide power to the first circuitry, the first communication circuit and the first control circuit.

2. The medical device system of claim 1 wherein the first control circuit is further configured to detect the condition for disabling the performing of the medical device system function by the first circuitry by: determining an estimated capacity of the power source; and determining that the estimated capacity of the power source has reached a threshold capacity.

3. The medical device system of any one of claims 1 — 2 wherein the first medical device further comprises a memory for storing data relating to the medical device system function; and the first control circuit is further configured to detect the condition for disabling the performing of the medical device system function by the first circuitry by: determining an available capacity of the memory for storing the data relating to the medical device system function; and determining that the available capacity of the memory has reached a threshold capacity.

4. The medical device system of any one of claims 1 — 3 wherein the first control circuit is further configured to detect the condition for disabling the performing of the medical device system function by the first circuitry by: performing an electrical diagnostic test; and detecting a circuit issue based on the electrical diagnostic test.

5. The medical device system of any one of claims 1 — 4 wherein the first control circuit is further configured to detect the condition for disabling the performing of the medical device system function by the first circuitry by: performing an impedance measurement; and detecting the condition for disabling the performing of the medical device system function based on the impedance measurement.

6. The medical device system of any one of claims 1 — 5 wherein the first circuitry comprises: a sensing circuit configured to sense at least one physiological signal; and a memory; the first circuitry configured to perform the medical device system function by: sensing the at least one physiological signal; and storing an episode of the at least one physiological signal in the memory.

7. The medical device system of any one of claims 1 — 6 wherein the first circuitry further comprises: a sensing circuit configured to sense at least one physiological signal; a memory; and processing circuitry configured to detect at least one physiological condition based on the at least one sensed physiological signal, wherein the first circuitry is further configured to perform the medical device function by: detecting the at least one physiological condition; and storing data associated with detecting the at least one physiological signal in the memory.

8. The medical device system of any one of claims 1 — 7 wherein the first circuitry further comprises a therapy delivery circuit configured to perform the medical device system function by delivering a therapy.

9. The medical device system of claim 8 wherein the therapy delivery circuit is configured to deliver the therapy by delivering one or more cardiac electrical stimulation pulses.

10. The medical device system of any one of claims 1 — 9 wherein the first circuitry that is configured to perform the medical device system function further comprises a second communication circuit, the first circuitry further configured to perform the medical device system function by transmitting data to an external medical device.

11. The medical device system of any one of claims 1 — 10 further comprising the second medical device, the second medical device comprising: second circuitry configured to perform the medical device system function; a second communication circuit configured to receive the communication signal; and a second control circuit configured to enable the second circuitry to perform the medical device system function in response to receiving the communication signal via the second communication circuit.

12. The medical device system of claim 11 wherein at least one of the first communication circuit or the second communication circuit is further configured to transmit a notification relating to the medical device system function being disabled in at least the first medical device.

13. The medical device system of any one of claims 1 — 12 wherein the second control circuit is further configured to: in response to receiving the communication signal via the second communication circuit, determine that criteria are met for the second circuitry to perform the medical device system function; and enable the second circuitry to perform the medical device system function in response to the criteria being met for the second circuitry to perform the medical device system function.

14. The medical device system of any one of claims 1 — 10 further comprising the second medical device, the second medical device comprising: second circuitry configured to perform the medical device system function; a second communication circuit configured to receive the communication signal; and a second control circuit configured to, in response to receiving the communication signal via the second communication circuit, determine that criteria are not met for the second circuitry to perform the medical device system function; and the second communication circuit further configured to transmit a denial signal in response to the second control circuit determining that the criteria are not met for the second circuitry to perform the medical device system function.

15. The medical device system of claim 14 wherein: the first communication circuit is further configured to receive the denial signal; and the first control circuit is further configured to delay disabling of the medical device system function being performed by the first circuitry in response to receiving the denial signal.

16. The medical device system of any one of claims 1 — 15 wherein the first communication circuit comprises at least one of a tissue conductance communication circuit or a radio frequency communication circuit.