Dual-lumen leadless pacemaker system and method of use thereof

Abstract

In one embodiment, a dual chamber LP system includes an aLP and a vLP that collectively provide AAI + VVI operation, and selectively transitions from the AAI + VVI operation to collectively provide coordinated dual chamber operation (e.g., DDD operation, but not limited thereto), and vice versa. While providing the AAI operation, the aLP performs atrial pacing, performs atrial sensing, when an intrinsic atrial event is not detected within a specified AA interval, and inhibits atrial pacing when an intrinsic atrial event is detected within the specified AA interval. While providing VVI operations, the vLP performs ventricular pacing, performs ventricular sensing, when an intrinsic ventricular event is not detected within a specified VV interval, and inhibits ventricular pacing when an intrinsic ventricular event is detected within the specified VV interval.

Description

[0001] Priority declaration

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 587,508, filed on October 3, 2023, entitled “DUAL CHAMBER LEADLESS PACEMAKER SYSTEMS AND METHODS FOR USE THEREWITH,” and U.S. Non-Provisional Patent Application No. 18 / 819,947, filed on August 29, 2024, entitled “DUAL CHAMBER LEADLESS PACEMAKER SYSTEMS AND METHODSFOR USE THEREWITH,” which are incorporated herein by reference. Technical Field

[0003] Embodiments described herein generally relate to dual-chamber leadless pacemaker (LP) systems and methods used therewith. Background Art

[0004] Conventional pacemakers typically include a housing (also called a "can") that houses a controller (e.g., a processor) and one or more intravascular leads extending from the housing. Each of the leads includes one or more electrodes that can be used to sense cardiac electrical activity and to deliver pacing stimuli. Such conventional pacemakers can support single-chamber operating modes (e.g., VVI, AAI) and coordinated dual-chamber operating modes (e.g., DDD, VDD, DDI, VDI, or DOO), depending on how many leads are used and how the conventional pacemaker is programmed. It should be noted that when such a pacemaker supports an operating mode, it is equivalent to saying that the pacemaker is providing a type of operation. For example, saying that the pacemaker supports a VVI operating mode is the same as saying that the pacemaker provides VVI operation. It should also be noted that the terms operating mode and pacing mode are often used interchangeably. For example, saying that the pacemaker operates in a VVI pacing mode is the same as saying that the pacemaker provides VVI operation or saying that the pacemaker supports VVI operation.

[0005] In the past few years, physicians have begun implanting leadless pacemakers (LPs) in place of conventional pacemakers because LPs eliminate the need for implanted leads. This is beneficial because leads may fail and / or migrate more frequently than desired. Initially, LPs were implanted in only a single heart chamber (e.g., the right ventricle (RV) chamber) and could only be used to support a single-chamber mode of operation (e.g., VVI).

[0006] It is now desirable to begin implanting LPs in two heart chambers (e.g., in the RV chamber and in the right atrium (RA) chamber) to provide a dual-chamber LP system capable of supporting coordinated dual-chamber operating modes (e.g., DDD, VDD, DDI, VDI, or DOO). An LP implanted in (or on) the RV chamber or configured to be implanted in (or on) the RV chamber may be referred to herein as a ventricular LP or vLP. An LP implanted in (or on) the RA chamber or configured to be implanted in (or on) the RA chamber may be referred to herein as an atrial LP or aLP.

[0007] In order for a dual-chamber LP pacing system to provide coordinated dual-chamber operation (e.g., of the RV chamber and the RA chamber), the aLP and vLP can coordinate their activities via direct beat-to-beat implant-to-implant (i2i) communication with each other or via a third implantable medical device (IMD) that acts as a communication hub for the LP. Such beat-to-beat i2i communication between the aLP and the vLP can be achieved using conductive communication, where the same electrodes used by the LP to deliver pacing pulses are also used to send i2i communication pulses to the other LP, and to receive i2i communication pulses from the other LP. Such beat-to-beat i2i communication between the aLP and the vLP can alternatively be achieved using another type of communication other than conductive communication (such as radio frequency (RF) communication or inductive communication). Regardless of the type of i2i communication used, heartbeat-by-heartbeat i2i communication (i.e., i2i communication that occurs every cardiac cycle) consumes a significant amount of power and, therefore, reduces the lifespan of the aLP and vLP by depleting their respective power sources (e.g., batteries) more quickly than if i2i communication were not used at all or if i2i communication were used less frequently than every heartbeat. For example, where conducted i2i communication is used on a heartbeat-by-heartbeat basis, the overall lifespan of the LP may be significantly reduced compared to where the LP is not using conducted i2i communication. Summary of the invention

[0008] Certain embodiments of the present technology relate to a method for use with a dual-chamber leadless pacemaker (LP) system including an atrial leadless pacemaker (aLP) and a ventricular leadless pacemaker (vLP). The method includes the aLP providing an AAI operation during which the aLP performs atrial pacing, performs atrial sensing, and inhibits atrial pacing when an intrinsic atrial event is detected within a specified AA interval after a previous pace or an intrinsic atrial event. The method also includes the vLP providing a VVI operation during which the vLP performs ventricular pacing, performs ventricular sensing, and inhibits ventricular pacing when an intrinsic ventricular event is detected within a specified VV interval after a previous pace or an intrinsic ventricular event. In the method, the aLP providing the AAI operation and the vLP providing the VVI operation occur during the same first time period and are independent of each other. During this first time period, the aLP and vLP of the dual chamber LP system together provide an operation referred to herein as AAI+VVI operation.

[0009] According to certain embodiments, each of the aLP and the vLP includes a respective transmitter that enables the LP to send i2i messages (to another LP or to a third IMD acting as a communication hub for the LP), includes a respective receiver that enables the LP to receive i2i messages (from another LP or from a third IMD acting as a communication hub for the LP), and includes a respective power source (e.g., a battery) for powering the transmitter and receiver of the LP. In certain such embodiments, the method further includes: during the same first time period in which the aLP provides AAI operations and the vLP provides VVI operations independently of each other, the aLP abstains from sending any i2i messages intended for coordinating the operations of the vLP with the aLP, and the vLP abstains from sending any i2i messages intended for coordinating the operations of the aLP with the vLP. This saves power, thereby increasing the life of the LP.

[0010] According to certain embodiments, the designated AA interval is shorter than the designated VV interval such that the atrial rate of atrial pacing performed by the aLP is faster than the ventricular rate of ventricular pacing performed by the vLP.

[0011] According to certain embodiments, the aLP includes a sensor that enables the aLP to monitor the activity level of a patient in which the aLP and vLP are implanted. In certain such embodiments, when the aLP provides AAI operation and the vLP provides VVI operation, the aLP adjusts the atrial rate of atrial pacing performed by the aLP by adjusting a specified AA interval based on the patient's activity level detected using the sensor of the aLP, and the vLP does not adjust the ventricular rate of ventricular pacing performed by the vLP, wherein such embodiments may be more specifically referred to as AAIR+VVI operation. In other embodiments, when the aLP provides AAI operation and the vLP provides VVI operation, the aLP adjusts the atrial rate of atrial pacing performed by the aLP by adjusting a specified AA interval based on the patient's activity level detected using the sensor of the aLP, and the vLP adjusts the ventricular rate of ventricular pacing performed by the vLP by adjusting the VV interval based on the patient's activity level detected using the sensor of the vLP, wherein such embodiments may be more specifically referred to as AAIR+VVIR operation. In such embodiments, the vLP also includes a sensor that enables the vLP to monitor the patient's activity level.

[0012] According to certain embodiments, each of the aLP and the vLP includes a corresponding sense amplifier, wherein the sense amplifier of the aLP is configured to sense an atrial electrogram (aEGM) for detecting an intrinsic atrial event, and the sense amplifier of the vLP is configured to sense a ventricular electrogram (vEGM) for detecting an intrinsic ventricular event. In certain such embodiments, when the aLP provides AAI operation and the vLP provides VVI operation, the method further includes the aLP monitoring for possible crosstalk that may be caused by the vLP performing ventricular pacing, and in response to the aLP detecting the possible crosstalk that may be caused by the vLP performing ventricular pacing, initiating providing crosstalk protection within a first crosstalk protection period. Additionally or alternatively, the method may include the vLP monitoring for possible crosstalk that may be caused by the aLP performing atrial pacing, and in response to the vLP detecting the possible crosstalk that may be caused by the aLP performing atrial pacing, the vLP initiating providing crosstalk protection within a second crosstalk protection period. Depending on the implementation, the second crosstalk protection period may have the same duration as the first crosstalk protection period or a different duration.

[0013] According to some embodiments, the method further includes the vLP determining whether a first specified criterion is met, and during a first time period when the first specified criterion is not met, the vLP abandons using the vLP's transmitter to send any i2i messages intended for coordinating the operations of the aLP and the vLP. Although the vLP abandons using its transmitter to send any i2i messages intended for coordinating the operations of the aLP and the vLP, the vLP may also disable or at least partially disable its receiver to further save power. The method further includes the vLP sending a mode switching type i2i message to the aLP using the vLP's transmitter during a second time period that begins in response to meeting the first specified criterion, and if the mode switching type i2i message is successfully received and confirmed by the aLP, the aLP and the vLP are converted (from providing AAI operation and VVI operation respectively) to jointly providing coordinated dual-chamber operation (which may be any one of DDD, VDD, DDI, VDI and DOO operations). During this period, i2i messages are sent by the aLP and the vLP (to support coordinated dual-chamber operation). In certain embodiments, the coordinated dual-chamber operation is a DDD operation during which the aLP and vLP send i2i messages (e.g., on a beat-by-beat basis) to enable coordinated dual-chamber pacing, and during which the vLP performs ventricular pacing when an intrinsic ventricular event is not detected within a specified atrioventricular (AV) delay after a previous pace or intrinsic atrial event, performs ventricular sensing, and inhibits ventricular pacing when an intrinsic ventricular event is detected within a specified AV delay after a previous pace or intrinsic atrial event. According to other embodiments, the coordinated dual-chamber operation includes one of a VDD, DDI, VDI, or DOO operation.

[0014] According to certain embodiments, the method includes the aLP generally disabling at least a portion of a corresponding receiver of the aLP that enables the aLP to receive one or more i2i messages, thereby saving power of a power supply (e.g., a battery) of the aLP compared to a case where at least a portion of the corresponding receiver of the aLP is enabled. In certain such embodiments, the method also includes the aLP temporarily enabling at least a portion of a receiver of the aLP from time to time that enables the aLP to receive one or more i2i messages from the vLP (or a third IMD that acts as a communication hub for the LP), thereby enabling the aLP to monitor i2i messages of a mode switch type. The method also includes the aLP receiving an i2i message of a mode switch type from the vLP (or a third IMD that acts as a communication hub for the LP), and sending a mode switch confirmation message in response thereto, and jointly providing coordinated dual-chamber operation with the vLP, during which i2i messages are sent by the aLP and the vLP (to support the coordinated dual-chamber operation).

[0015] In some such embodiments, the method further includes the aLP refraining from using its transmitter to send any i2i messages intended to coordinate the operation of the vLP and the aLP until the aLP receives an i2i message of the mode-switch type.

[0016] According to some embodiments, the first specified criterion that the vLP determines whether is satisfied includes the vLP providing at least a first specified threshold amount of ventricular pacing within a first specified duration. The first specified threshold amount may be a first specified number or a first specified percentage, but is not limited thereto. The first specified criterion that the vLP determines whether is satisfied may also include the vLP delivering ventricular pacing during at least X of the Y most recent cardiac cycles, where X and Y are predetermined values and X < Y. Other variations are possible and are within the scope of the embodiments described herein.

[0017] According to some embodiments, the method further includes: after the vLP has switched from providing the VVI mode of operation to co-providing coordinated dual-chamber operation with the aLP, during which i2i messages are sent by the aLP and the vLP (to support the coordinated dual-chamber operation), the vLP determines whether a second specified criterion is satisfied. In some such embodiments, during a third time period that begins in response to the second specified criterion being satisfied, the vLP uses the vLP's transmitter to send an additional mode-switch type of i2i message, and if the aLP successfully receives and acknowledges the additional mode-switch type of i2i message, causes the aLP to switch from co-providing the coordinated dual-chamber mode of operation with the vLP to the aLP providing the AAI operation independently of the vLP again, and causes the vLP to switch from co-providing the coordinated dual-chamber mode of operation with the aLP to the vLP providing the VVI operation independently of the aLP again. In other words, it causes a transition back to the AAI+VVI operation from the coordinated dual-chamber operation when the second specified criterion is satisfied.

[0018] According to some embodiments, the second specified criterion that the vLP determines whether is satisfied includes the vLP providing less than a second specified threshold amount of ventricular pacing within a second specified duration. The second specified threshold amount may be a second specified number or a second specified percentage, but is not limited thereto. The second specified criterion that the vLP determines whether is satisfied may also include the vLP delivering ventricular pacing during fewer than A of the B most recent cardiac cycles, where A and B are predetermined values and A < B. Other variations are possible and are within the scope of the embodiments described herein.

[0019] According to certain embodiments of the present technology, when the aLP provides AAI operation and the vLP provides VVI operation, independently of each other, the aLP monitors a third specified criterion, which, when detected by the aLP, causes the aLP to send an i2i message to the vLP (or to a third IMD acting as a communication hub for the LP), wherein the i2i message instructs the vLP to change (e.g., increase) its basic pacing rate, or equivalently instructs the vLP to change (e.g., shorten) its basic VV interval. In order for the vLP to receive such i2i messages, the vLP should temporarily enable its receiver from time to time. The aLP may repeatedly send such messages until the aLP receives an ACK message that the vLP received the message. Thereafter, the aLP may monitor a fourth criterion, e.g., that the atrial rate has fallen below a specified threshold or some other specified threshold. In response to the aLP detecting the fourth criterion, the aLP sends an i2i message to the vLP (or to a third IMD acting as a communication hub for the LP) instructing the vLP to change (e.g., decrease) its basic pacing rate, or equivalently instructing the vLP to change (e.g., increase) its basic VV interval. The aLP may repeatedly send such an i2i message until the aLP receives an ACK message that the vLP received the message.

[0020] Certain embodiments of the present technology relate to a dual-chamber LP system comprising an atrial leadless pacemaker (aLP) and a ventricular leadless pacemaker (vLP). The aLP is configured to be implanted in or on an atrial heart chamber of a patient's heart. The vLP is configured to be implanted in or on a ventricular heart chamber of a patient's heart. During the same time period and independently of each other, the aLP is configured to provide AAI operation, and the vLP is configured to provide VVI operation. When the aLP provides AAI operation, the aLP performs atrial pacing, performs atrial sensing, and inhibits atrial pacing when an intrinsic atrial event is not detected within a specified AA interval after a previous pace or an intrinsic atrial event, when an intrinsic atrial event is detected within a specified AA interval after a previous pace or an intrinsic atrial event. When the vLP provides VVI operation, the vLP performs ventricular pacing when no intrinsic ventricular event is detected within a specified VV interval after a previous pace or an intrinsic ventricular event, performs ventricular sensing, and inhibits ventricular pacing when an intrinsic ventricular event is detected within a specified VV interval after a previous pace or an intrinsic ventricular event.

[0021] According to some embodiments, each of the aLP and the vLP includes a respective transmitter that enables the LP to send i2i messages, includes a respective receiver that enables the LP to receive i2i messages, and includes a respective power source (e.g., a battery) for powering the transmitter and the receiver of the LP. In some such embodiments, during the same first time period in which the aLP provides AAI operations and the vLP provides VVI operations independently of each other, the aLP is configured to abstain from sending any i2i messages intended for coordinating the operations of the vLP with the aLP, and the vLP is configured to abstain from sending any i2i messages intended for coordinating the operations of the aLP with the vLP.

[0022] According to certain embodiments, the designated AA interval is shorter than the designated VV interval such that the atrial rate of atrial pacing performed by the aLP is faster than the ventricular rate of ventricular pacing performed by the vLP.

[0023] According to certain embodiments, the aLP includes a sensor that enables the aLP to monitor the activity level of a patient in which the aLP and vLP are implanted. In addition, each LP in the aLP and vLP includes a corresponding controller. In certain such embodiments, the controller of the aLP is configured to adjust the atrial rate of atrial pacing performed by the aLP by adjusting a specified AA interval based on the patient's activity level detected by the sensor of the aLP when the aLP provides AAI operation. In addition, the controller of the vLP is configured not to adjust the ventricular rate of ventricular pacing performed by the vLP when the vLP provides VVI operation. In other embodiments, the controller of the aLP is configured to adjust the atrial rate of atrial pacing performed by the aLP by adjusting a specified AA interval based on the patient's activity level detected by the sensor of the aLP when the aLP provides AAI operation, and the controller of the vLP is configured to adjust the ventricular rate of ventricular pacing performed by the vLP by adjusting the VV interval based on the patient's activity level detected by the sensor of the vLP when the vLP provides VVI pacing, wherein such embodiments may be more specifically referred to as AAIR+VVIR operation. In such an embodiment, the vLP includes sensors that enable the vLP to monitor the patient's activity level.

[0024] According to certain embodiments, the aLP includes a sense amplifier configured to sense an atrial electrogram (aEGM) used by the aLP to detect intrinsic atrial events, and the vLP includes a sense amplifier configured to sense a ventricular electrogram (vEGM) used by the vLP to detect intrinsic ventricular events. Additionally, the aLP includes a controller communicatively coupled to the sense amplifier of the aLP, and the vLP includes a controller communicatively coupled to the sense amplifier of the vLP. In certain such embodiments, the controller of the vLP is configured to monitor for possible crosstalk that may be caused by atrial pacing performed by the aLP while the vLP provides VVI operation, and in response to the controller of the vLP detecting the possible crosstalk that may be caused by atrial pacing performed by the aLP, initiate providing crosstalk protection within a first crosstalk protection period. Additionally or alternatively, the controller of the aLP is configured to monitor possible crosstalk that may be caused by ventricular pacing performed by the vLP while the aLP provides AAI operation, and in response to the controller of the aLP detecting possible crosstalk that may be caused by ventricular pacing performed by the vLP, initiate providing crosstalk protection during a second crosstalk protection period.

[0025] According to certain embodiments, each of the aLP and the vLP includes a respective transmitter that enables the LP to send i2i messages to the other LP, includes a respective receiver that enables the LP to receive i2i messages from the other LP, and includes a respective battery for powering the transmitter and receiver of the LP. Additionally, the aLP includes a controller that is communicatively coupled to the transmitter and receiver of the aLP and powered by the battery of the aLP, and the vLP includes a controller that is communicatively coupled to the transmitter and receiver of the vLP and powered by the battery of the vLP. In certain such embodiments, the controller of the vLP is configured to determine whether a first specified criterion is met, to forgo using the transmitter of the vLP to send any i2i messages intended for coordinating operations of the aLP with the vLP during a first time period when the first specified criterion is not met, and to cause the transmitter of the vLP to send an i2i message of a mode switch type in response to the first specified criterion being met. If the i2i of the mode switch type message is successfully received and acknowledged by the aLP, the aLP and the vLP are caused to switch (from providing AAI operation and VVI operation independently of each other) to jointly providing coordinated dual-chamber operation during a second time period, during which i2i messages are sent by the aLP and the vLP (to support the coordinated dual-chamber operation). In some embodiments, jointly providing coordinated dual-chamber operation (during which i2i messages are sent by the aLP and the vLP) includes jointly providing DDD operation. In other words, in a specific embodiment, the coordinated dual-chamber operation is DDD operation. The aLP and the vLP jointly providing coordinated dual-chamber operation, during which i2i messages are sent by the aLP and the vLP (to support the coordinated dual-chamber operation), may alternatively include jointly providing VDD, DDI, VDI, or DOO operation.

[0026] According to certain embodiments, the controller of the aLP is configured to generally disable at least a portion of the aLP's receiver that enables the aLP to receive one or more i2i messages, thereby saving power of the aLP's power supply (e.g., a battery) compared to a case where at least a portion of the aLP's receiver is enabled. Additionally, the controller of the aLP is configured to temporarily enable at least a portion of the aLP's receiver that enables the aLP to receive one or more i2i messages from time to time, thereby enabling the aLP to monitor for a mode switching type of i2i message that causes the aLP to switch from providing an AAI operating mode to providing coordinated dual-chamber operation with the vLP, during which i2i messages are sent by the aLP and the vLP (to support coordinated dual-chamber operation). The controller of the aLP is also configured to cause the aLP to switch from providing an AAI operating mode to providing coordinated dual-chamber operation with the vLP in response to the aLP receiving and confirming the mode switching type of i2i message. In some such embodiments, the controller of the aLP causes the aLP to abstain from using its transmitter to send any i2i messages intended for coordinating the operation of the vLP with the aLP until the aLP receives an i2i message of a mode switch type from the vLP.

[0027] According to certain embodiments, the controller of the vLP is configured to determine whether the first specified criterion is satisfied including the vLP providing at least a first specified threshold amount of ventricular pacing for a first specified duration.

[0028] According to certain embodiments, the controller of the vLP is configured to determine whether a second specified criterion is met after the vLP has switched from providing a VVI operation mode to providing coordinated dual-chamber operation with the aLP. The controller of the vLP is also configured to use the transmitter of the vLP to send an additional mode switch type i2i message to the aLP during a third time period that begins in response to meeting the second specified criterion, and if the additional mode switch type i2i message is successfully received and confirmed by the aLP, the aLP is switched from the dual-chamber operation mode providing coordination with the vLP to the aLP again providing AAI operation independently of the vLP, and the vLP is switched from the dual-chamber operation mode providing coordination with the aLP to the vLP again providing VVI operation independently of the aLP. In other words, a transition from coordinated dual-chamber operation back to AAI+VVI operation is caused when the second specified criterion is met.

[0029] According to certain embodiments, the controller of the vLP is configured to determine whether the second specified criterion met includes the vLP providing less than a second specified threshold amount of ventricular pacing for a second specified duration.

[0030] Certain embodiments of the present technology relate to a method for use with a dual-chamber leadless pacemaker (LP) system including an atrial leadless pacemaker (aLP) and a ventricular leadless pacemaker (vLP). The method includes, during a same first time period, during which the aLP and the vLP abandon communication with each other, the aLP providing AAI operation and the vLP providing VVI operation independently of each other. The method also includes, during a second time period that begins in response to satisfying a first specified criterion, the vLP and the aLP communicating with each other and switching from aLP providing AAI operation and vLP providing VVI operation independently of each other to aLP and vLP jointly providing one of DDD, VDD, DDI, VDI, or DOO operations.

[0031] According to certain embodiments, the method further includes: during a third time period starting in response to satisfying a second specified criterion, aLP and vLP switch from jointly providing one of DDD, VDD, DDI, VDI or DOO operations back to vLP again providing VVI operation and vLP again providing VVI operation independently of each other.

[0032] According to certain embodiments, a first specified criterion is met when the vLP provides at least a first specified threshold amount of ventricular pacing for a first specified duration, and a second specified criterion is met when the vLP provides less than a second specified threshold amount of ventricular pacing for a second specified duration.

[0033] This summary is not intended to be a complete description of embodiments of the present technology. Other features and advantages of embodiments of the present technology will emerge from the following description, in which preferred embodiments have been described in detail in conjunction with the accompanying drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Embodiments of the present technology, both as to structure and method of operation, may best be understood by reference to the following description and drawings, wherein like reference numerals represent like elements throughout the several views:

[0035] Figure 1 A system formed according to certain embodiments herein is shown implanted in a heart.

[0036] Figure 2 is a block diagram of a single LP according to some embodiments herein.

[0037] Figure 3 An LP according to some embodiments herein is shown.

[0038] Figure 4 is a timing diagram illustrating one embodiment of i2i communication of pacing events.

[0039] Figure 5is a timing diagram illustrating one embodiment of i2i communication of sensed events.

[0040] Fig. 6A and 6B is a high-level flow chart summarizing a method according to certain embodiments of the present technology.

[0041] Figure 7 A block diagram is shown of one embodiment of an LP implanted in a patient as part of a dual chamber LP system according to some embodiments herein. DETAILED DESCRIPTION

[0042] As described above, in order for the dual-chamber LP pacing system to provide coordinated (also referred to as synchronized) dual-chamber operation, the aLP and vLP can coordinate their activities via heartbeat-by-heartbeat i2i communication. However, such heartbeat-by-heartbeat i2i communication (i.e., i2i communication that occurs every cardiac cycle) consumes a large amount of power and, therefore, reduces the lifespan of the aLP and vLP by depleting their respective power sources (e.g., batteries) more quickly than if i2i communication were not used at all or if i2i communication were used less frequently than every heartbeat.

[0043] A potential disadvantage of relying on beat-by-beat i2i communication to coordinate pacing of the RA and RV chambers in a dual-chamber LP system configured to jointly provide DDD operation is that such a system may be designed to inhibit atrial pacing when i2i communication from the vLP to the aLP is unsuccessful (for a single beat, or across multiple consecutive cardiac cycles), which has the effect of causing the dual-chamber LP system to jointly provide VDD operation rather than jointly provide programmed DDD operation. This behavior (jointly providing VDD operation when programmed DDD operation is not possible) is a design mitigator used to prevent the two LPs from potentially causing symptomatic harm to the patient by pacing at an asynchronous (also called uncoordinated) rhythm. While inhibiting atrial pacing may be acceptable for some patients, there are other patients for whom reliable atrial-based pacing is important and sometimes necessary. For example, for patients with sinus node dysfunction (SND), atrial-based pacing is the primary therapeutic support required. Furthermore, most patients with SND have an intact and fully functional atrioventricular (AV) node and therefore are able to naturally maintain AV synchrony via normal AV conduction followed by intrinsic ventricular activation with little or no need for ventricular pacing support.

[0044] Certain embodiments of the present technology relate to a new operating mode for a dual-chamber LP system, which new operating mode may be referred to herein as an AAI+VVI (AAI "plus" VVI) operating mode, or more succinctly as an AAI+VVI mode or AAI+VVI operation, or even more succinctly as AAI+VVI. The primary use case for utilizing this new AAI+VVI mode is patients with SND, who typically have intact AV nodal conduction and may rarely or occasionally require intermittent ventricular pacing support, for example, due to transient AV block, but not limited to such. In this case, when the dual-chamber LP system utilizes the new AAI+VVI operating mode, the primary role of the vLP is to provide backup ventricular safety pacing support, which optimally minimizes ventricular pacing only when required by the patient and when pacemaker-mediated atrioventricular (AV) synchronization is not clinically necessary. That is, when the new AAI+VVI operating mode is provided, the vLP is typically used to provide backup ventricular safety pacing support.

[0045] According to certain embodiments of the present technology, AAI+VVI operation is achieved by operating the aLP in AAI mode and operating the vLP in VVI mode without requiring the aLP and the vLP to perform heartbeat-by-heartbeat i2i communication (i.e., without requiring the aLP and the vLP to attempt to communicate with each other during each cardiac cycle). In other words, the AAI+VVI mode of operation is achieved by the aLP providing AAI operation and the vLP providing VVI operation during the same time period.

[0046] When the aLP provides AAI operation (also referred to as, when the aLP provides AAI mode pacing), the aLP performs atrial pacing in response to not detecting an intrinsic atrial event within a designated AA interval following a previous (e.g., immediately preceding) paced or intrinsic atrial event, performs atrial sensing (to sense an intrinsic atrial event before the end of the designated AA interval), and inhibits atrial pacing in response to detecting an intrinsic atrial event within a designated AA interval following a previous paced or intrinsic atrial event.

[0047] When the vLP provides VVI operation (also referred to as, when the vLP provides VVI mode pacing), the vLP performs ventricular pacing in response to not detecting an intrinsic ventricular event within a specified VV interval following a previous (e.g., immediately preceding) paced or intrinsic ventricular event, performs ventricular sensing (to sense an intrinsic ventricular event before the end of the specified VV interval), and inhibits ventricular pacing in response to detecting an intrinsic ventricular event within a specified VV interval following a previous paced or intrinsic ventricular event.

[0048] According to certain embodiments, the programmable pacing rate of the aLP is constrained to always be greater than the programmable pacing rate of the aLP. This constraint ensures that the aLP drives the overall cardiac electromechanical function, and that the vLP rate is mitigated from displacing the aLP rate, which could result in undesired reverse AV node conduction. According to certain embodiments, the constraint is implemented by programming the AA interval (used by the aLP) to be shorter than the VV interval (used by the vLP), which has the effect of making the atrial rate of atrial pacing performed by the aLP faster than the ventricular rate of ventricular pacing performed by the vLP. In certain such embodiments, the aLP provides rate-responsive pacing, i.e., AAI operation is provided by AAIR operation, while the vLP provides non-rate-responsive VVI pacing. More specifically, in certain embodiments, the ability to modulate the pacing rate using an activity (e.g., temperature or motion) sensor is limited to the aLP, e.g., by enabling rate-responsive pacing by the aLP, and is made unavailable to the vLP, e.g., by disabling rate-responsive pacing by the vLP. This constraint is consistent with the intended use case, where atrial-based pacing is the primary need and ventricular function is tracked intrinsically via intact AV nodal conduction, with ventricular pacing intended for backup safety support only when needed. In other embodiments, each of the aLP and vLP provides rate-responsive pacing, i.e., the aLP provides AAIR operation, and the vLP provides VVIR operation.

[0049] When referring to various types of operating schemes (also referred to as pacing modes or operations) in this article, three letters are generally used to refer to the type of operation. In other words, a three-digit pacemaker code is generally used, following the following nomenclature: the first digit refers to the cardiac chamber that is paced; the second digit refers to the cardiac chamber that is sensed; and the third digit refers to the response to the sensed event. In the first and second digits, the letter O represents none, the letter A represents the atrium, the letter V represents the ventricle, and the letter D represents double (i.e., A and V). In the third digit, the letter O represents none, the letter I represents inhibition, the letter T represents triggering (also referred to as tracking), and the letter D represents double (i.e., T+I). Table 1 below summarizes this pacemaker nomenclature. Wherein R is included in the fourth digit, which means that the pacing provided is rate responsive.

[0050] Position 1 Position 2 Location 3 (Ventricular Pacing) (Chamber Sensing) (Response to a sensed event) O = None O = None O = None A = Atria A = Atria I = Inhibition V = ventricle V = ventricle T = Trigger (also called Tracking) D=Dual (A+V) D=Dual (A+V) D=Dual (I+T)

[0051] Table 1

[0052] As is known in the art, DDD and DDDR operations provide synchronized dual-chamber pacing. More specifically, DDD operation provides atrial and ventricular pacing, atrial and ventricular sensing, and the ability to inhibit or trigger pacing after a sensed event. DDDR operation is a rate-responsive DDD operation, i.e., the pacing rate is adjusted based on the patient's activity level (e.g., as detected using a motion sensor and / or a temperature sensor). Unless otherwise stated, the term DDD operation as used herein also covers DDDR operation. Similarly, unless otherwise stated, the term AAI operation as used herein also includes AAIR operation; and unless otherwise stated, the term VVI operation as used herein also includes VVIR pacing mode.

[0053] Although neither the aLP nor the vLP can perform DDD operations individually, the aLP and the vLP can be configured to jointly provide DDD operations (including DDDR operations) when there is successful heartbeat-by-heartbeat bidirectional i2i communication (i.e., when the vLP successfully receives an i2i message from the aLP and the aLP successfully receives an i2i message from the vLP). In some embodiments, when the aLP and the vLP jointly provide DDD operations, they communicate with each other on each cardiac cycle, i.e., on a heartbeat-by-heartbeat basis.

[0054] However, due to various reasons, there may be periods of time when bidirectional i2i communication fails because the vLP fails to successfully receive one or more atrial-to-ventricular (a2v) i2i messages from the aLP, and / or the aLP fails to successfully receive one or more ventricle-to-atrial (v2a) i2i messages from the vLP. Such failures in i2i communication may occur, for example, due to noise, the relative orientation of the aLP and vLP, and / or the distance between the aLP and vLP (but not limited thereto).

[0055] The dual chamber LP system may have safeguards in place to reduce asynchronous pacing in the event of loss of i2i communication in one or both directions, as outlined in Table 2 below.

[0056]

[0057] Table 2

[0058] As can be understood from Table 2 above, in a dual-chamber LP system including an aLP and a vLP configured to jointly provide DDD operation, if v2a communication is lost (i.e., one or more v2a i2i messages sent by the vLP are not successfully received by the aLP), the aLP stops pacing and the dual-chamber LP system effectively provides VDD operation. If a2v i2i communication is lost (i.e., one or more of the a2v i2i messages sent by the aLP are not successfully received by the vLP), tracking is lost and the dual-chamber LP system effectively provides DDI operation. If i2i communication is lost in both directions simultaneously (i.e., the v2a i2i message sent by the vLP is not successfully received by the aLP, and the a2v i2i message sent by the aLP is not successfully received by the vLP), both mitigations are in effect and the dual-chamber LP system effectively provides VDI operation. These transmission and reception guarantees are used to guarantee RV pacing while maintaining RA tracking and RA pacing as much as possible. However, when the dual chamber LP system is actively providing VDD or VDI operation, there is no atrial pacing.

[0059] As described above, while inhibiting atrial pacing may be acceptable for some patients, there are other patients for whom reliable atrial-based pacing is important and sometimes necessary. For example, for patients with SND, atrial-based pacing is the primary therapeutic support required. As described above, certain embodiments of the present technology relate to a new AAI+VVI mode of operation. Additional details of such embodiments are provided herein. However, before providing additional details of specific embodiments of the present technology described above, reference will first be made to Figures 1 to 5 Describes exemplary systems in which or with which embodiments of the present technology may be used. More specifically, Figures 1 to 5 An example dual chamber LP system will be described that optionally also includes a non-vascular ICD (NV-ICD), such as a subcutaneous ICD (S-ICD), and a programmer.

[0060] Figure 1A system 100 configured to be implanted in a heart 101 is shown. The system 100 includes LPs 102a and 102b located in different chambers of the heart. LP 102a is located in the right atrium, and therefore may also be referred to herein as the atrial LP (aLP). LP 102b is located in the right ventricle, and therefore may also be referred to herein as the ventricular LP (vLP). aLP 102a and vLP 102b may be collectively referred to herein as LP 102, or individually referred to as LP 102. LPs 102a and 102b may communicate with each other to notify each other of various local physiological activities (such as local intrinsic events, local pacing events, etc.). LPs 102a and 102b may be constructed in a similar manner, but operate differently based on which chamber LP 102a or 102b is located.

[0061] In certain embodiments, LPs 102a and 102b communicate with each other and / or with the ICD 106 via conducted communication using the same electrodes used for sensing and / or delivering pacing therapy. LPs 102a and 102b may also be able to use conducted communication to communicate with an external device (e.g., a programmer 109) having electrodes placed on the skin of a patient in which LPs 102a and 102b are implanted. Alternatively or additionally, LPs 102a and 102b may each include an antenna that would enable them to communicate with each other, with the ICD 106, and / or with the external device using RF communications. Alternatively or additionally, LPs 102a, 102b may utilize another type of communication (such as inductive communication), in which case LPs 102a, 102b may each include a respective inductive communication coil. Although Figure 1 Only two LPs are shown, but more than two LPs may be implanted in a patient. For example, in order to provide biventricular pacing and / or cardiac resynchronization therapy (CRT), in addition to implanting LPs in the right atrial (RA) chamber and the right ventricular (RV) chamber, an additional LP may be implanted in the left ventricular (LV) chamber.

[0062] Each LP 102 uses two or more electrodes located within, on, or within a few centimeters of the pacemaker's housing for pacing and sensing at the heart chambers. Where the LP 102 communicates using conducted communication, the electrodes of the LP 102 can also be used for bidirectional conducted communication with each other and with the programmer 109 and ICD 106.

[0063] refer to Figure 2, a block diagram illustrating an embodiment of a portion of the electronics within the LP 102a, 102b configured to provide conducted communication via sensing / pacing electrodes. One or more of the LP 102a and 102b include at least two leadless electrodes configured for delivering cardiac pacing pulses, sensing induced and / or natural cardiac electrical signals, and unidirectional or bidirectional conducted communication. Figure 2 (and Figure 3 ), wherein the two electrodes shown are labeled 108a and 108b. Such electrodes may be collectively referred to as electrodes 108, or individually referred to as electrodes 108. Depending on the implementation, LP 102 or other types of implantable medical devices (IMDs) may include more than two electrodes 108.

[0064] exist Figure 2 , each of the LPs 102a, 102b is shown to include a first receiver 120 and a second receiver 122 that together define separate first and second conductive communication channels 105, 107 between the LPs 102a and 102b. Figure 1 ) (among other things). Although a first receiver 120 and a second receiver 122 are depicted, in other embodiments, each LP 102a, 102b may include only the first receiver 120, or more generally may include only a single receiver configured to receive conducted communication signals. The LP 102 may also include additional receivers in addition to the first and second receivers 120 and 122. As will be described in further detail below, the pulse generator 116 may function as a transmitter that transmits i2i communication signals using the electrodes 108. In some embodiments, the LPs 102a and 102b may communicate through more than just the first and second conducted communication channels 105, 107. In some embodiments, the LPs 102a and 102b may communicate through one common communication channel 105. More specifically, the LPs 102a and 102b may communicate conductively on a common physical channel via the same electrodes 108 that are also used to deliver pacing pulses.

[0065] The receivers 120 and 122 may also be referred to as a low frequency (LF) receiver 120 and a high frequency (HF) receiver 122, respectively, because the receiver 120 is configured to monitor one or more signals within a relatively low frequency range (e.g., below 100 kHz), and the receiver 122 is configured to monitor one or more signals within a relatively high frequency range (e.g., above 100 kHz). In some embodiments, the receiver 120 (and more specifically, at least a portion thereof) is always enabled and monitors for a wake-up notification, which may simply be a wake-up pulse within a specific low frequency range (e.g., between 1 kHz and 100 kHz); and the receiver 122 is selectively enabled by the receiver 120. The receiver 120 is configured to consume less power than the receiver 122 when both the first receiver and the second receiver are enabled. Therefore, the receiver 120 may also be referred to as a low power receiver 120, and the receiver 122 may also be referred to as a high power receiver 122. In some embodiments, when aLP and vLP jointly provide AAI+VVI operation, both the lower power receiver 120 and the high power receiver 120 of aLP are generally disabled, and the lower power receiver 120 is enabled from time to time to monitor the mode switching type i2i message from vLP. Alternatively, when aLP and vLP jointly provide AAI+VVI operation, aLP always powers its low power receiver 120 and only powers its high power receiver 122 in response to receiving a wake-up pulse from vLP, where the wake-up pulse can be part of an i2i message from vLP, which i2i message is a mode switching i2i message. Other variations are also possible and within the scope of the embodiments described herein. In some such embodiments, aLP abandons using its transmitter to send any i2i messages intended to coordinate the operation of vLP with aLP until aLP receives an i2i message of the mode switching type.

[0066] The low power receiver 120 is not capable of receiving signals within a relatively high frequency range (e.g., above 100 kHz), but consumes significantly less power than the high power receiver 122. In this way, the low power receiver 120 is able to always monitor for wake-up notifications without significantly draining the battery of the LP (e.g., 114). According to certain embodiments, in response to the low power receiver 120 receiving the wake-up notification, the high power receiver 122 is selectively enabled by the low power receiver 120 so that the high power receiver 122 can receive higher frequency signals, thereby handling the higher data throughput required for effective i2i communication, without unnecessarily and quickly draining the battery of the LP (as the high power receiver 122 might do if always enabled).

[0067] Because receivers 120, 122 are used to receive conducted communication messages, receivers 120, 122 may also be referred to as conducted communication receivers. In some embodiments, each of LPs 102 includes only a single conducted communication receiver.

[0068] According to certain embodiments, when one of the LPs 102a and 102b senses an intrinsic event or delivers a paced event, the corresponding LP 102a, 102b sends an implant event message to the other LP 102a, 102b. For example, when the atrial LP 102a senses / paces an atrial event, the atrial LP 102a sends an implant event message including an event marker indicating the nature of the event (e.g., intrinsic / sensed atrial event, paced atrial event). When the ventricular LP 102b senses / paces a ventricular event, the ventricular LP 102b sends an implant event message including an event marker indicating the nature of the event (e.g., intrinsic / sensed ventricular event, paced ventricular event). In some embodiments, each LP 102a, 102b sends an implant event message to the other LP 102a, 102b prior to the actual pacing pulse so that the remote LP can blank its sensing input (or provide some other type of crosstalk protection) in anticipation of the remote pacing pulse (to prevent inappropriate crosstalk sensing). The above-mentioned implant event messages are examples of i2i messages.

[0069] The implant event message can be formatted in various ways. As an example, each event message can include a leading trigger pulse (also referred to as an LP wake-up notification, wake-up pulse, or wake-up signal) following an event marker. The notification trigger pulse (also referred to as a wake-up notification, wake-up pulse, or wake-up signal) is sent on a first channel (e.g., with a pulse duration of about 10 μs to about 1 ms and / or in a base frequency range of about 1 kHz to about 100 kHz). The notification trigger pulse indicates that the event marker is about to be sent via a second channel (e.g., in a higher frequency range). The event marker can then be sent via the second channel.

[0070] The event markers may include data indicating one or more events (e.g., intrinsic atrial activation of a sensed LP located in the atrium, intrinsic ventricular activation of a sensed LP located in the ventricle). The event markers may include different markers for intrinsic events and pacing events. The event markers may also indicate the start or end time of a timer (e.g., AV interval, blanking interval, etc.). Optionally, the implant event message may include a message segment that includes additional / secondary information.

[0071] Optionally, an LP (or other IMD) that receives any i2i communication message from another LP (or other IMD) or from an external device may send a reception confirmation (ACK) indicating that the receiving LP (or other IMD) received the i2i communication message. In some embodiments, in the case where the IMD expects to receive an i2i communication message within a window but fails to receive the i2i communication message within the window, the IMD may send a reception failure (failure-to-receive) confirmation indicating that the receiving IMD failed to receive the i2i communication message. The reception failure confirmation message may also be referred to as a negative acknowledgement (NACK) message. The LP may receive a message from another LP, the message containing an indicator (e.g., an error code) in its payload or header, which indicates to the LP that the other LP failed to receive the expected message from the LP. Other variations are also possible and are within the scope of the embodiments described herein.

[0072] Event messages enable LP 102a, 102b to deliver synchronized therapy and additional supporting features (e.g., measurements, etc.). To maintain synchronized therapy, each of LP 102a and 102b is made aware (via event messages) when an event occurs in a chamber containing the other LP 102a, 102b. Some embodiments described herein provide an efficient and reliable process to maintain synchronization between LP 102a and 102b without the need to maintain continuous communication between LP 102a and 102b. According to certain embodiments herein, low power event messaging / signaling may be maintained synchronously or asynchronously between LP 102a and 102b.

[0073] For synchronous event signaling, LPs 102a and 102b may maintain synchronization and communicate periodically at specific intervals. Synchronous event signaling allows the transmitter and receiver in each LP 102a, 102b to use limited (or minimal) power because each LP 102a, 102b is powered only for a small portion of the time associated with transmission and reception. For example, LPs 102a, 102b may transmit / receive (Tx / Rx) communication messages in time slots having a duration of 10-20 μs, where the Tx / Rx time slots occur periodically (e.g., every 10-20 ms). For example, such synchronous event signaling may be used when LPs 102a and 102b jointly provide coordinated dual-chamber operation, during which i2i messages are sent by aLP and vLP (to support coordinated dual-chamber operation), but is not limited thereto.

[0074] Even in a synchronization event signaling scheme, LPs 102a and 102b may lose synchronization. As explained herein, features may be included in LPs 102a and 102b to keep devices synchronized, and when synchronization is lost, LPs 102a and 102b are operated to restore synchronization. Furthermore, synchronization event messages / signaling may introduce delays between transmissions, which results in a reaction lag at the receiving LPs 102a, 102b. Therefore, features may be implemented to account for the reaction lag.

[0075] During asynchronous event signaling, the LPs 102a and 102b do not maintain communication synchronization. During asynchronous event signaling, one or more of the receivers 120 and 122 of the LPs 102a and 102b may be "always on" (always awake) to search for incoming transmissions. However, there are challenges in keeping the LP receivers 120, 122 in an "always on" (always awake) state because the received signal levels are typically low due to high channel attenuation caused by the patient's anatomy. In addition, keeping the receivers awake will drain the battery 114 faster than might be desired.

[0076] According to some embodiments, the first receiver 120 may keep the first channel active (awake) at all times (including when the second channel is inactive (sleeping)) in order to listen for messages from the remote IP. The second receiver 122 may be assigned a second activation protocol as a trigger protocol, wherein the second receiver 122 becomes active (awake) in response to detecting a trigger event on the first receiving channel (e.g., activating the second channel at the local LP when the incoming signal corresponds to an LP wake-up notification). The terms active, on, awake, and enabled may be used interchangeably herein.

[0077] Still reference Figure 2 , each LP 102a, 102b is shown as including a controller 112 and a pulse generator 116. The controller 112 may include, for example, but is not limited to, a microprocessor (or equivalent control circuitry), RAM and / or ROM memory, logic and timing circuits, state machine circuits, and I / O circuits. The controller 112 may also include, for example, a timing control circuit for controlling the timing of stimulation pulses (e.g., pacing rate, atrioventricular (AV) delay, atrial conduction interval (AA) delay, or ventricular conduction interval (VV) delay, etc.). Such timing control circuitry may also be used for timing of refractory periods, blanking intervals, noise detection windows, induced response windows, alarm intervals, marker channel timing, and the like. The controller 112 may also include other dedicated circuits and / or firmware / software components that assist in monitoring various conditions of the patient's heart and managing pacing therapy. For example, the controller 112 may include an arrhythmia detector, which may be similar to the one described below with reference to FIG. Figure 7 Arrhythmia detector 734 discussed.

[0078] The controller 112 and the pulse generator 116 may be configured to send event messages via the electrodes 108 in a manner that does not inadvertently capture the heart in the chamber where the LP 102a, 102b is located (such as when the associated chamber is not in a refractory state). Additionally, the LP 102a, 102b receiving the event message may enter an "event refractory" state (or event blanked state) after receiving the event message. The event refractory / blanked state may be set to extend a determined time period after receiving the event message in order to avoid the receiving LP 102a, 102b from inadvertently sensing another signal as an event message that may otherwise result in a re-triggering. For example, the receiving LP 102a, 102b may detect a measurement pulse from another LP 102a, 102b or the programmer 109.

[0079] Because the conducted communications receivers 120, 122 (or alternatively, only a single conducted communications receiver) and the pulse generator 116 are used to perform conducted communications, these components may be considered part of the conducted communications transceiver 124. The conducted communications transceiver 124 may alternatively include alternative and / or additional components that enable an LP or other type of IMD to send and receive conducted communications messages with another IMD and / or with an external device (such as a programmer 109). For example, while the same pulse generator 116 may be used to generate pacing pulses (for pacing a patient's heart) and conducted communications pulses (for communicating with another IMD or an external device), the conducted communications transceiver 124 may also include its own dedicated pulse generator. For another example, as described above, the conducted communications transceiver 124 may also include only a single receiver, rather than two receivers 120, 122. Other variations are possible and are within the scope of the embodiments described herein.

[0080] Still reference Figure 2, LP 102 is also shown to include an antenna 118 coupled to a radio frequency (RF) communication transceiver 134, which is configured to send and receive RF communication messages using an RF communication protocol (such as a Bluetooth protocol, a WiFi protocol, a Bluetooth low energy (BLE) protocol, a medical device radio communication service (MedRadio) protocol, etc.). In some embodiments, the antenna 118 can be integrated into the fixing mechanism (e.g., 205) of the LP, in which case the antenna can be referred to as a fixed antenna. An example implementation of a fixed antenna is disclosed in U.S. Patent No. 10,583,300, entitled "Leadless implantable medical device with fixation antenna member," which is incorporated herein by reference. In other embodiments, the antenna 118 is separate and distinct from the fixing mechanism of the LP 102. The specific type, location, and form factor of the antenna can depend on the specific type and form factor of the IMD.

[0081] The RF communications transceiver 134 consumes more battery power than the conducted communications transceiver 124. More generally, it is more power efficient to use conducted communications from an LP 102 (or other type of IMD) than to use RF communications to communicate with another LP 102 (or other type of IMD). Thus, in accordance with certain embodiments of the present technology, an LP 102 (or other type of IMD) is configured to primarily use conducted communications to send and receive messages, and RF communications are used as a backup or secondary type of communication that can be used when conducted communications are disabled (also referred to as turned off) or are unsuccessful or otherwise defective, as will be described in more detail below.

[0082] LPs 102a, 102b may be capable of communicating with each other and / or other devices (such as programmer 109 and / or ICD 106) using only conducted communications, in which case antenna 118 and RF communications transceiver 134 may be omitted. It may also be the case that LPs 102a, 102b are only configured to communicate using RF communications and do not utilize conducted communications, in which case certain circuits (such as receivers 120, 122) may be omitted. Alternatively or additionally, LPs 102a, 102b may utilize another type of communication (such as inductive communications), in which case LPs 102a, 102b may each include a respective inductive communications coil.

[0083] According to some embodiments herein, programmer 109 may communicate with LP 102a, 102b via a programmer-to-LP channel utilizing the same communication scheme. External programmer 109 may listen to event messages sent between LP 102a, 102b and synchronize the programmer to implant communications such that programmer 109 does not send communication messages 17 until after the i2i messaging sequence is complete.

[0084] In some embodiments, each individual LP 102 can include an airtight housing 110 configured for placement on or attachment to the interior or exterior of a heart chamber and at least two leadless electrodes 108 proximate to the housing 110 and configured for bidirectional communication with at least one other device (e.g., an ICD 106) inside or outside the body.

[0085] Figure 2 A single LP 102 (e.g., LP 102a or 102b) is depicted, and the functional elements of the LP are shown to be substantially contained within an airtight housing 110. The LP 102 has at least two electrodes 108 located within, on, or near the housing 110 for delivering pacing pulses to the muscles of the heart chambers and sensing electrical activity from the muscles of the heart chambers, and for bidirectional communication with at least one other device inside or outside the body. Airtight feedthroughs 130, 131 conduct electrode signals through the housing 110. The housing 110 contains a primary battery 114 to provide power for pacing, sensing, and communication. The housing 110 also contains circuitry 132 for sensing cardiac activity from the electrodes 108, receivers 120, 122 for receiving information from at least one other device via the electrodes 108, and a pulse generator 116 for generating pacing pulses for delivery via the electrodes 108 and also for sending information to at least one other device via the electrodes 108. Housing 110 may also contain circuitry for monitoring device health, such as battery current monitor 136 and battery voltage monitor 138, and may contain circuitry for controlling operation in a predetermined manner.

[0086] The electrodes 108 can be configured to communicate bidirectionally between multiple leadless cardiac pacemakers and / or implantable ICDs 106 to coordinate pacing pulse delivery and optionally other therapeutic or diagnostic features using messages that identify events at individual pacemakers that initiate the messages, and the pacemakers that receive the messages react as indicated by the messages based on the source of the messages. The LPs 102a, 102b that receive the event messages react as indicated by the event messages based on the source or location of the messages. In some embodiments or conditions, two or more leadless electrodes 108 can be configured to communicate bidirectionally between one or more leadless cardiac pacemakers 102 and / or ICDs 106 and transmit data including designated codes for events detected or created by individual pacemakers. Individual pacemakers can be configured to emit unique codes corresponding to the type of event and the location of the transmitting pacemaker.

[0087] In some embodiments, the individual LPs 102a, 102b can be configured to deliver pacing pulses with event messages encoded therein, wherein codes are assigned based on pacemaker locations, and configured to send the messages to one or more other leadless cardiac pacemakers via the pacing pulses with the event messages encoded therein. The one or more pacemakers receiving the messages are adapted to respond to the messages in a predetermined manner based on the type and location of the event.

[0088] In addition, the information transmitted on the incoming channel can also include an event message from another leadless cardiac pacemaker, indicating that the other leadless cardiac pacemaker has sensed a heartbeat or has delivered a pacing pulse, and identifying the location of the other pacemaker. For example, LP 102b can receive the event message from LP 102a and relay it to the programmer. Similarly, the information transmitted on the outgoing channel can also include a message to another one or more leadless cardiac pacemakers or ICDs, that the sending leadless cardiac pacemaker has sensed a heartbeat or has delivered a pacing pulse at the location of the sending pacemaker.

[0089] Refer again Figure 1 and Figure 2 , the cardiac pacing system 100 may include an ICD 106 in addition to one or more LPs 102a, 102b, which are configured for implantation in electrical contact with a cardiac chamber and for performing cardiac rhythm management functions in combination with the implanted ICD 106. According to the embodiments discussed herein, the implanted ICD 106 and the one or more LPs 102a, 102b are configured for leadless mutual communication via information conduction through body tissue and / or wireless transmission between a transmitter and a receiver.

[0090] In further embodiments, the cardiac pacing system 100 includes at least one LP 102a, 102b configured for implantation in electrical contact with a cardiac chamber and configured to perform cardiac pacing functions in combination with a co-implanted ICD 106. Each LP 102 includes at least two leadless electrodes 108 configured for delivering cardiac pacing pulses, sensing induced and / or natural cardiac electrical signals, and sending information to the co-implanted ICD 106.

[0091] As shown in the illustrative embodiment, the LP 102a, 102b may include two or more leadless electrodes 108 configured for delivering cardiac pacing pulses, sensing induced and / or natural cardiac electrical signals, and communicating bidirectionally with a co-implanted ICD 106.

[0092] Each LP 102a, 102b can be configured to operate in a corresponding specific location and have a corresponding specific function at the time of manufacture and / or by programming by an external programmer. Bidirectional communication between multiple leadless cardiac pacemakers can be arranged to transmit notification of a sensed heartbeat or delivered pacing pulse event and the encoded type and location of the event to another one or more implanted pacemakers. The LP 102a, 102b receiving the communication decodes the information and responds according to the location of the receiving pacemaker and the predetermined system function.

[0093] In some embodiments, LPs 102a and 102b are configured to be implantable in any chamber of the heart, i.e., the atria (RA, LA) or the ventricles (RV, LV). In addition, for a dual-chamber configuration, multiple LPs may be co-implanted (e.g., one in the RA and one in the RV, one in the RV and one in the coronary sinus proximal to the LV). Certain pacemaker parameters and functions depend on (or assume) knowledge of the chamber in which the pacemaker is implanted (and therefore the LP interacts with, e.g., pacing and / or sensing). Some non-limiting examples include sensing sensitivity, induced response algorithms, use of AF suppression in local chambers, blanking and refractory periods, etc. Therefore, each LP needs to know the identity of the chamber in which (or on which) the LP is implanted, and a process may be implemented to automatically identify the local chamber associated with each LP.

[0094] The process for chamber identification may also be applied to subcutaneous pacemakers, ICDs with leads, etc. For devices with one or more implanted leads, identification and / or confirmation of the chamber in which the lead is implanted may be useful in a number of relevant scenarios. For example, for a DR or CRT device, automatic identification and confirmation may mitigate the possibility of a clinician inadvertently placing a V lead into an A port of an implantable medical device, or vice versa.

[0095] Also like Figure 2 As shown, the primary battery 114 has a positive terminal 140 and a negative terminal 142. Current from the positive terminal 140 of the primary battery 114 flows through a shunt 144 to a regulator circuit 146 to generate a positive voltage supply 148 suitable for powering the remaining circuits of the pacemaker 102. The shunt 144 enables the battery current monitor 136 to provide an indication of battery current drain and indirectly provide an indication of device health to the controller 112. An exemplary power source can be the primary battery 114.

[0096] Still reference Figure 2 , the LP is shown to include a temperature sensor 152. The temperature sensor may be any of a variety of different types of known temperature sensors, or may be a temperature sensor developed in the future. For example, the temperature sensor 152 may be a thermistor, a thermocouple, a resistance thermometer, or a silicon bandgap temperature sensor, but is not limited thereto. Regardless of how the temperature sensor 152 is implemented, preferably, the temperature sensed by the sensor is provided to the controller 112 as a digital signal indicating the blood temperature of the patient in which the LP is implanted. The temperature sensor 152 may be hermetically sealed within the housing 110, but this is not necessarily the case. The temperature sensor 152 may be used in a variety of ways. For example, the temperature sensor 152 may be used to detect the patient's activity level to adjust the pacing rate, i.e., for rate-responsive pacing. When a person begins to exercise, their core body temperature initially drops, and then after a long period of exercise, the person's core body temperature will eventually rise. Thereafter, when the person stops exercising, their core body temperature will return to their baseline. Thus, the controller 112 may be configured to detect the patient's activity level based on the core blood temperature measurement obtained using the temperature sensor 152.

[0097] refer to Figure 2, LP is also shown to include an accelerometer 154, which can be hermetically contained within the housing 110. The accelerometer 154 can be any of a variety of different types of known accelerometers, or can be an accelerometer developed in the future. For one example, the accelerometer 154 can be or include, for example, a MEMS (micro-electromechanical system) multi-axis accelerometer of the type utilizing capacitive or optical cantilever technology, or a piezoelectric accelerometer that uses the piezoelectric effect of certain materials to measure dynamic changes in mechanical variables. For example, the accelerometer 154 can be used to detect the patient's activity level to adjust the pacing rate, that is, for rate-responsive pacing. The output of both the accelerometer 154 and the temperature sensor 152 can also be used to monitor the patient's activity level. Alternatively or additionally, the patient's activity level can be monitored based on the patient's heart rate, as sensed from the IEGM sensed using the electrode 108, and / or using a plethysmographic sensor (not shown) or a heart sound sensor (not shown), but is not limited to this. One or more signals generated and output by the accelerometer 154 can be analyzed with respect to frequency content, energy, duration, amplitude and / or other characteristics. Such signals may be amplified and / or filtered or may not be amplified and / or filtered before being analyzed. For example, filtering may be performed using a low-pass, high-pass and / or band-pass filter. The signal output by the accelerometer 154 may be an analog signal, which may be analyzed in the analog domain, or may be converted to a digital signal (via an analog-to-digital converter) and analyzed in the digital domain. Alternatively, the signal output by the accelerometer 154 may already be in the digital domain. One or more signals output by the accelerometer 154 may be analyzed by the controller 112 and / or other circuits. In some embodiments, the accelerometer 154 is packaged with an integrated circuit (IC) that is designed to analyze the (one or more) signals it generates. In such an embodiment, one or more outputs of the packaged sensor / IC may be an indication of acceleration along one or more axes. In other embodiments, the accelerometer 154 can be packaged with an IC that performs signal conditioning (e.g., amplification and / or filtering), performs analog-to-digital conversion, and stores digital data (indicative of sensor output) in a memory (e.g., RAM, which may or may not be within the same package). In such embodiments, the controller 112 or other circuitry can read the digital data from the memory and analyze the digital data. Other variations are possible and within the scope of embodiments of the present technology. According to certain embodiments of the present technology described in additional detail below, the sensor signal generated by the accelerometer 154 of the LP implanted in or on a heart chamber can be used to detect mechanical heart activity associated with another heart chamber.

[0098] In various embodiments, the LP 102a, 102b can manage power consumption to draw limited power from the battery, thereby reducing the size of the device. Each circuit in the system can be designed to avoid large peak currents. For example, cardiac pacing can be achieved by discharging a tank capacitor (not shown) across the pacing electrodes. The recharging of the tank capacitor is typically controlled by a charge pump circuit. In a specific embodiment, the charge pump circuit is throttled to recharge the tank capacitor with constant power from the battery.

[0099] In some embodiments, a controller 112 in an LP 102 can access the signals on the electrodes 108 and can examine the output pulse duration from another LP 102 for use as a signature for determining the validity of the trigger information and, for a signature that is within predetermined limits, activate the delivery of a pacing pulse after a predetermined delay of zero or more milliseconds. The predetermined delay can be preset at the time of manufacture, programmed via an external programmer, or determined by adaptive monitoring to facilitate identification of the trigger signal and to distinguish the trigger signal from noise. In some embodiments or under some conditions, the controller 112 can examine the output pulse waveform from another leadless cardiac pacemaker for use as a signature for determining the validity of the trigger information and, for a signature that is within predetermined limits, activate the delivery of a pacing pulse after a predetermined delay of zero or more milliseconds.

[0100] Figure 3 Example form factors of LPs 102a, 102b are shown. Each LP may include a gas-tight housing 202 (e.g., Figure 2 110 in the figure). As shown, electrode 108a can be separated from but partially surrounded by fixation mechanism 205, and electrode 108b can be disposed on housing 202. Fixation mechanism 205 can be a fixation helix, a plurality of hooks, barbs, or other attachment features configured for attaching the pacemaker to tissue (such as cardiac tissue). As described above, the antenna (e.g., 118) can be at least partially implanted by the fixation mechanism or implanted as part of the fixation mechanism. Electrodes 108a and 108b are the above reference Figure 2 Examples of electrodes 108 are shown and discussed.

[0101] The housing may also include an electronics compartment 210 within the housing that contains electronic components necessary for operation of the pacemaker, including, for example, a pulse generator, a transceiver, a battery, and a processor for operation. The airtight housing 202 may be suitable for implantation on or in a human heart, and may be, for example, cylindrical, rectangular, spherical, or any other suitable shape.

[0102] The housing can include a conductive, biocompatible, inert, and anodically safe material, such as titanium, 316L stainless steel, or other similar material. The housing can also include an insulator disposed on the conductive material to separate electrodes 108a and 108b. The insulator can be an insulating coating on a portion of the housing between the electrodes and can include a material such as silicone, polyurethane, parylene, or another biocompatible electrical insulator commonly used in implantable medical devices. Figure 2 In an embodiment, a single insulator 208 is disposed between electrodes 108a and 108b along a portion of the housing. In some embodiments, the housing itself may include an insulator rather than a conductor, such as alumina ceramic or other similar material, and the electrodes may be disposed on the housing.

[0103] like Figure 3 As shown, the pacemaker may also include a header assembly 212 for isolating 108a and 108b. Head assembly 212 may be made of PEEK, tecothane, or another biocompatible plastic, and may include ceramic to metal feedthroughs, glass to metal feedthroughs, or other suitable feedthrough insulators known in the art.

[0104] Electrodes 108a and 108b may include pacing / sensing electrodes or return electrodes. A low polarization coating may be applied to the electrodes (such as sintered platinum, platinum iridium, iridium, iridium oxide, titanium nitride, carbon, or other materials commonly used to reduce polarization effects). Figure 2 In the embodiment of the present invention, electrode 108a can be a pacing / sensing electrode and electrode 108b can be a return electrode. Electrode 108b can be a portion of conductive housing 202 that does not include insulator 208.

[0105] The housing 202 may be attached to the inner or outer wall of the heart using a variety of techniques and structures. The helical fixation mechanism 205 may enable insertion of the device into the endocardium or epicardium via a guide catheter. A twistable catheter may be used to rotate the housing and force the fixation device into the heart tissue, thereby inserting the fixation device (and Figure 2 Electrode 108a) in the device is fixed in contact with the stimulable tissue. Electrode 108b can be used as an indifferent electrode for sensing and pacing. The fixing mechanism can be partially or completely coated for electrical insulation, and a steroid eluting matrix can be included on the device or near the device to minimize fibrotic response, as is known in conventional pacing electrode leads.

[0106] Implant-to-implant event messaging

[0107] LP 102a and 102b can coordinate operations with each other in various ways using implant-to-implant (i2i) communications via event messages. The terms i2i event messages and i2i event markers are used interchangeably herein to refer to event-related messages and IMD / IMD operation-related messages sent from an implanted device and directed to another implanted device (although an external device (e.g., a programmer) can also receive i2i event messages). In certain embodiments, LP 102a and LP 102b operate as two independent leadless pacemakers that maintain beat-to-beat dual-chamber function via a "master / slave" operating configuration. For purposes of description, the ventricular LP 102b should generally be referred to as a "vLP," and the atrial LP 102a should generally be referred to as an "aLP," as described above. An LP 102 designated as a master device (e.g., a vLP) can implement all or most dual-chamber diagnostic and treatment determination algorithms. For purposes of the following description, it is assumed that the vLP is the "master" device and the aLP is the "slave" device. Alternatively, the aLP may be designated as the master device and the vLP may be designated as the slave device.The master device coordinates most or all decisions and timing determinations (including, for example, rate response changes).

[0108] Figure 4 4 is a timing diagram 400 illustrating an example of i2i conducted communication of a pacing event. The i2i conducted communication may be sent, for example, from LP 102a to LP 102b. Figure 4 As shown, in this embodiment, an i2i transmission 402 is sent before a pacing pulse 404 is delivered by a transmitting LP (e.g., LP 102a). This enables a receiving LP (e.g., LP 102b) to prepare for remote delivery of a pacing pulse. The i2i transmission 402 includes an envelope 406, which may include one or more individual pulses. For example, in this embodiment, the envelope 406 includes a low frequency pulse 408 followed by a high frequency pulse train 410. The low frequency pulse 408 lasts for a period of time T i2iLF , and the high frequency pulse train 410 lasts for a period of time T i2iHF The end of the low frequency pulse 408 and the beginning of the high frequency pulse train 410 are separated by a gap period T i2igap In an alternative embodiment, instead of sending envelope 406 before pacing pulse 404, envelope 406 may be sent during a refractory period following delivery of a pacing pulse.

[0109] like Figure 4As shown, i2i transmission 402 lasts for a period Ti2iP, and pacing pulse 404 lasts for a period Tpace. The end of i2i transmission 402 and the beginning of pacing pulse 404 are separated by a delay period TdelayP. The delay period can be, for example, between about 0.0 and 10.0 milliseconds (ms), specifically between about 0.1 ms and 2.0 ms, and more specifically about 1.0 ms. As used herein, the term "about" means + / - 10% of a specified value.

[0110] Figure 5 5 is a timing diagram 500 showing an example of i2i communication of a sensed event. The i2i communication may be sent, for example, from LP 102a to LP 102b. Figure 5 As shown, in this embodiment, when the sensed intrinsic activation 502 crosses the sensing threshold 504, the transmitting LP (e.g., LP 102a) detects the sensed event. After detection, the transmitting LP transmits for a predetermined period of time T i2iS i2i transmission 506. The delay period may be, for example, between about 0.0 and 10.0 milliseconds (ms), specifically between about 0.1 ms and 2.0 ms, and more specifically about 1.0 ms.

[0111] As with i2i transmission 402, i2i transmission 506 may include an envelope that may include one or more individual pulses. For example, similar to envelope 406, the envelope of i2i transmission 506 may include a low frequency pulse followed by a high frequency pulse train. In some embodiments, i2i transmission 506 is sent during a refractory period following a sensed event.

[0112] Optionally, wherein the first LP is located in the atrium and the second LP is located in the ventricle, the first LP generates an AS / AP event marker to indicate that an atrial sensing (AS) event or an atrial pacing (AP) event has occurred or will occur in the near future. For example, the AS and AP event markers can be sent after the corresponding AS or AP events. Alternatively, the first LP can send the AP event marker slightly in advance of delivering the atrial pacing pulse. Alternatively, wherein the first LP is located in the atrium and the second LP is located in the ventricle, the second LP initiates an atrioventricular (AV) interval after receiving the AS or AP event marker from the first LP; and initiates a post atrial ventricular blanking (PAVB) interval after receiving the AP event marker from the first LP.

[0113] Alternatively, the first and second LPs may operate in a "pure" master / slave relationship, where the master LP delivers "command" markers in addition to or instead of "event" markers. The command markers instruct the slave LP to perform an action (such as delivering a pacing pulse, etc.). For example, when the slave LP is located in the atrium and the master LP is located in the ventricle, in a pure master / slave relationship, the slave LP delivers an immediate pacing pulse to the atrium upon receipt of an AP command marker from the master LP.

[0114] According to some embodiments, communication and synchronization between the aLP and the vLP is achieved via conducted communication of tags / commands in event messages (according to the i2i communication protocol). As described above, conducted communication refers to event messages sent from sensing / pacing electrodes at frequencies outside the RF (e.g., Wi-Fi or BLE) frequency range. Alternatively, the event messages may be transmitted via a communication channel operating within the RF frequency range. The following figures and corresponding descriptions illustrate non-limiting examples of tags that may be sent in event messages. The following figures and corresponding descriptions also include descriptions of examples of tags and results that occur in the LP receiving the event message. Table 3 represents example event tags sent from the aLP to the vLP, while Table 4 represents example event tags sent from the vLP to the aLP. In a master / slave configuration, an AS event tag is sent from the aLP whenever an atrial event is sensed outside the post-ventricular atrial blanking (PVAB) interval or some other alternatively defined atrial blanking period. An AP event tag is sent from the aLP whenever the aLP delivers a pacing pulse in the atrium. The aLP may limit the sending of AS markers, whereby the aLP sends an AS event marker when an atrial event is sensed both outside the PVAB interval and outside the post-ventricular atrial refractory period (PVARP) or some other alternatively defined atrial refractory period. Alternatively, the aLP may not limit the sending of AS event markers based on the PVARP, but instead send an AS event marker every time an atrial event is sensed.

[0115]

[0116] Table 3

[0117] As shown in Table 3, when aLP sends an event message including an AS event marker (indicating that aLP sensed an intrinsic atrial event), vLP initiates the AV interval timer. If aLP sends AS event markers for all sensed events, vLP will preferably first determine that the PVAB or PVARP interval is not active before initiating the AV interval timer. However, if aLP only sends AS event markers when it senses an intrinsic signal outside of the PVAB or PVARP intervals, vLP can initiate the AV interval timer upon receiving the AS event marker without first checking the PVAB or PVARP status. When aLP sends an AP event marker (indicating that aLP delivers or is about to deliver a pacing pulse to the atrium), vLP initiates the PVAB timer and the AV interval timer, provided that the PVARP interval is not active. vLP can also blank its sense amplifier to prevent possible crosstalk sensing of remote pacing pulses delivered by aLP.

[0118]

[0119] Table 4

[0120] As shown in Table 4, when the vLP senses a ventricular event, the vLP sends an event message including a VS event marker, in response to which the aLP may initiate a PVARP interval timer. When the vLP delivers or is about to deliver a pacing pulse in the ventricle, the vLP sends a VP event marker. When the aLP receives the VP event marker, the aLP initiates a PVAB interval timer as well as a PVARP interval timer. The aLP may also blank its sense amplifier to prevent possible crosstalk sensing of remote pacing pulses delivered by the vLP. The vLP may also send an event message containing an AP command marker to command the aLP to deliver an immediate pacing pulse in the atrium without delay upon receipt of the command.

[0121] The aforementioned event markers are examples of a subset of markers that can be used to enable the aLP and vLP to maintain full dual-chamber functionality. In one embodiment, the vLP can execute all dual-chamber algorithms, while the aLP can execute atrial-based hardware-related functions (such as PVAB) that are implemented locally within the aLP. In this embodiment, the aLP is effectively considered a remote "wireless" atrial pacing / sensing electrode. In another embodiment, the vLP can execute most but not all dual-chamber algorithms, while the aLP can execute a subset of diagnostic and therapeutic algorithms. In alternative embodiments, the vLP and aLP can execute diagnostic and therapeutic algorithms equally. In some embodiments, decision-making responsibility can be divided solely to one of the aLP or vLP. In other embodiments, decision-making responsibility may involve joint inputs and responsibilities.

[0122] Messages sent between LPs (e.g., aLP and vLP) may generally be referred to herein as i2i messages (because they are implant-to-implant messages). As described above, such messages may include event markers that enable one LP to notify another LP of a pacing event or sensed event. For example, in some embodiments, whenever aLP 102a senses an atrial event or paces the right atrium, aLP will send an i2i message to vLP 102b to notify vLP of the sensed or pacing event in the atrium. In response to receiving such an i2i message, vLP 102b may start one or more timers that enable the vLP to sense the right ventricle or pace in the right ventricle. Similarly, whenever vLP senses a ventricular event or paces the right ventricle, vLP may send an i2i message to aLP 102a.

[0123] The i2i messages sent between LPs can be relatively short messages that simply allow a first LP to notify a second LP of an event sensed by or caused (paced) by the first LP, and vice versa. Such i2i messages may be referred to herein as event marker i2i messages, or more succinctly as event i2i messages. In some instances, the i2i messages sent between LPs may be extended i2i messages that include (in addition to the event marker) an extension. In some embodiments, the extended i2i message includes an event marker (e.g., 9 bits), followed by an extension indicator (e.g., 2 bits), followed by an extended message payload portion (e.g., 17 bits), followed by a cyclic redundancy check (CRC) code (e.g., 6 bits) or some other type of error detection and correction code. Other variations are also possible.

[0124] AAI+VVI Operation

[0125] As explained above, certain embodiments of the present technology relate to a new AAI+VVI mode of operation used by a dual chamber LP system. Also as explained above, the primary use case for utilizing this new AAI+VVI operation is patients with SND, who typically have intact AV nodal conduction and may rarely or occasionally require intermittent ventricular pacing support, for example, due to transient AV block, but not limited thereto.

[0126] AAI+VVI operation is achieved by operating the aLP in AAI mode and the vLP in VVI mode without requiring the aLP and the vLP to perform i2i communication (i.e., without requiring the aLP and the vLP to attempt to communicate with each other every cardiac cycle, every other cardiac cycle, or even less frequently). In other words, the AAI+VVI mode of operation is achieved by the aLP providing AAI operation and the vLP independently providing VVI operation during the same time period.

[0127] When the aLP provides AAI operation, in response to not detecting an intrinsic atrial event within a designated AA interval following a previous (e.g., immediately preceding) paced or intrinsic atrial event, the aLP performs atrial pacing, performs atrial sensing (to sense an intrinsic atrial event before the end of the designated AA interval), and inhibits atrial pacing in response to detecting an intrinsic atrial event within the designated AA interval following a previous paced or intrinsic atrial event.

[0128] When the vLP provides VVI operation, in response to not detecting an intrinsic ventricular event within a specified VV interval following a previous (e.g., immediately preceding) paced or intrinsic ventricular event, the vLP performs ventricular pacing, performs ventricular sensing (to sense an intrinsic ventricular event before the end of the specified VV interval), and inhibits ventricular pacing in response to detecting an intrinsic ventricular event within a specified VV interval following a previous paced or intrinsic ventricular event.

[0129] According to certain embodiments, the programmable pacing rate of the aLP is constrained to always be greater than the programmable pacing rate of the vLP. This constraint ensures that the aLP drives the overall cardiac electromechanical functions, and wherein the vLP rate is mitigated from superseding the aLP rate, which could result in undesired reverse AV nodal conduction. According to certain embodiments, this constraint is achieved by programming the AA interval (used by the aLP) to be shorter than the VV interval (used by the vLP), which has the effect of making the atrial rate of atrial pacing performed by the aLP faster than the ventricular rate of ventricular pacing performed by the vLP. Additionally or alternatively, according to certain embodiments, the programmable pacing rate of the vLP is constrained to always be less than the programmable pacing rate of the aLP. This constraint similarly ensures that the aLP drives the overall cardiac electromechanical functions, and wherein the vLP rate is mitigated from superseding the aLP rate, which could result in undesired reverse AV nodal conduction. According to certain embodiments, this constraint is achieved by programming the VV interval (used by the vLP) to be longer than the AA interval (used by the aLP), which has the effect of making the ventricular rate of ventricular pacing performed by the vLP slower than the atrial rate of atrial pacing performed by the aLP.

[0130] According to certain embodiments, the aLP provides rate-responsive pacing, i.e., AAI operation is provided by AAIR operation, while the vLP provides non-rate-responsive VVI pacing. More specifically, the aLP can utilize its temperature sensor (e.g., 152) and / or its motion sensor (e.g., accelerometer 154) to detect patient activity and modulate its pacing rate based on the detected patient activity. In certain such embodiments, when the aLP provides rate-responsive AAI operation (i.e., AAIR operation), the vLP provides its VVI operation using a constant programmed ventricular rate. In other words, the VVI operation provided by the vLP is not rate-responsive. This may be because the vLP disables its temperature sensor (e.g., 152) and / or its motion sensor (e.g., accelerometer 154), ignores its output, or turns off its rate-responsive feature. Such one or more constraints are consistent with the intended use case, in which atrial-based pacing performed by the aLP is the primary need and ventricular function provided by the vLP is intrinsically tracked via intact AV node conduction, in which ventricular pacing performed by the vLP is intended for backup safety support only when needed. In other embodiments, when the aLP provides rate-responsive AAI operation (i.e., AAIR operation), the vLP provides rate-responsive VVI operation (i.e., VVIR operation), which may be more specifically referred to as AAIR+VVIR operation. In certain embodiments, when the dual-chamber LP system provides AAIR+VVIR operation, the sensitivity of the temperature sensor and / or motion sensor of the vLP is less than the sensitivity of the temperature sensor and / or motion sensor of the aLP, such that an increase in the atrial pacing rate provided by the aLP is greater than a corresponding increase in the ventricular pacing rate provided by the vLP. This configuration keeps the AA interval shorter than the VV interval, thereby keeping the atrial rate of atrial pacing performed by the aLP faster than the ventricular rate of ventricular pacing performed by the vLP.

[0131] The following references Fig. 6A and 6B A high-level flow chart of FIG. 1 is used to describe additional details of AAI+VVI operation according to certain embodiments of the present technology. Fig. 6A and 6B , the steps or operations performed by the aLP (e.g., 102a) are shown on the left, and the steps or operations performed by the vLP (e.g., 102b) are shown on the right. Fig. 6AAs with other embodiments, it is generally assumed that the aLP and vLP are able to communicate directly with each other using i2i messages sent from the aLP to the vLP and i2i messages sent from the vLP to the aLP. Note, however, that a third implantable medical device (IMD) may alternatively act as a communication hub for the aLP and the vLP, in which case the aLP may send i2i messages to the third IMD, and the third IMD may send i2i messages to the vLP, and the vLP may send additional i2i messages to the third IMD, and the third IMD may send additional i2i messages to the aLP. Such a third IMD may be, for example, an ICD 106, an insertable cardiac monitor (ICM), or an IMD that is used solely to support communication between other IMDs, but is not limited thereto.

[0132] refer to Fig. 6A , step 602 involves the aLP using its sense amplifier (e.g., 132) to sense an atrial electrogram (aEGM), which the aLP (and more specifically, its controller) uses to detect an intrinsic atrial event, such as a P wave. Step 604 involves the aLP providing an AAI operation, during which the aLP performs atrial pacing when an intrinsic atrial event is not detected within a specified AA interval following a previous pace or intrinsic atrial event, performs atrial sensing (e.g., to sense an intrinsic atrial event within the aEGM), and inhibits atrial pacing when an intrinsic atrial event is detected within a specified AA interval following a previous (e.g., immediately preceding) pace or intrinsic atrial event. Note that, depending on the particular implementation, the AAI operation provided at step 604 may be rate-responsive (i.e., may be an AAIR operation). Alternatively, the AAI operation provided at step 604 may not be rate-responsive.

[0133] Still reference Fig. 6A , step 632 involves the vLP using its sense amplifier (e.g., 132) to sense a ventricular electrogram (vEGM), which the vLP (and more specifically, its controller) uses to detect an intrinsic ventricular event, such as an R wave. Step 634 involves the vLP providing a VVI operation during which the vLP performs ventricular pacing when an intrinsic ventricular event is not detected within a specified VV interval following a previous pace or intrinsic ventricular event, performs ventricular sensing (e.g., to sense an intrinsic ventricular event within the vEGM), and inhibits ventricular pacing when an intrinsic ventricular event is detected within a specified VV interval following a previous (e.g., immediately preceding) pace or intrinsic ventricular event.

[0134] According to certain embodiments, steps 602 and 604 are performed by the aLP during the same time period as steps 632 and 634 are performed by the vLP. In certain such embodiments, to save power and thereby increase the lifetime of the aLP and the vLP, when the vLP provides VVI operation, the aLP forgoes sending any i2i messages intended for coordinating the operation of the vLP with the aLP, and when the aLP provides AAI operation, the vLP forgoes sending any i2i messages intended for coordinating the operation of the aLP with the vLP while performing steps 604 and 634. In other words, implementing AAI+VVI operation does not require any i2i messages to be sent from the aLP to the vLP (directly, or via a third IMD acting as a communication hub), or vice versa.

[0135] If the aLP and vLP communicate with each other using i2i messages, the vLP can notify the aLP via i2i messages of the pacing pulses to be delivered by the vLP, in response to which the aLP can blank its sense amplifier (e.g., 132) so that the aLP does not erroneously detect a paced ventricular event as an intrinsic atrial event. However, when the aLP and vLP forgo sending i2i messages to each other, this is not possible, which increases the likelihood that the aLP may erroneously detect a paced ventricular event as an intrinsic atrial event, which in turn will cause the aLP to inhibit atrial pacing for that cardiac cycle, which is undesirable. In order to reduce the probability that the aLP will erroneously detect a paced ventricular event as an intrinsic atrial event, at step 606, the aLP monitors for possible crosstalk that may be caused by ventricular pacing performed by the vLP. Therefore, according to certain embodiments, the aLP is configured to monitor for possible crosstalk that may be caused by ventricular pacing performed by the vLP. The following describes example additional details of how such an embodiment may be implemented.

[0136] For example, such possible crosstalk monitoring at step 606 may be performed using one of the techniques described in U.S. Patent No. 10,182,765, entitled “Systems and Methods for Classifying Signals of Interest in a Cardiac Rhythm Management Device,” which is incorporated herein by reference. Figure 2 , assuming that the sense amplifier 132 of LP ( Figure 2If the aLP (e.g., 102a) is used to pass signals within a first frequency passband that contains intrinsic cardiac activity (e.g., P waves and R waves), the sense amplifier 132 may also be referred to as an intrinsic activity sense amplifier 132 or an intrinsic activation sense circuit, etc. In order to monitor possible crosstalk at step 606, the aLP (e.g., 102a) may also include a separate crosstalk sensing circuit having a passband that is shifted to a significantly higher frequency than the passband of the intrinsic activity sense amplifier 132, so that the crosstalk sensing circuit can better distinguish the relatively fast rising and falling edges of the crosstalk caused by the pacing pulses generated by the vLP (e.g., 102b). Such a crosstalk sensing circuit may be implemented, for example, by the LF receiver 120, or may be implemented by Figure 2 6. The aLP and more specifically its controller (e.g., 112) can implement another sense amplifier not specifically shown in FIG. Using such a sense circuit, the aLP, and more specifically its controller (e.g., 112) can classify the sense signal being evaluated as a possible crosstalk, where the sense signal is delivered by the crosstalk sensing circuit. This is only one example of a circuit and technique that the aLP can use to perform possible crosstalk monitoring at step 606. Using other circuits and / or techniques to monitor possible crosstalk is also within the scope of the embodiments described herein.

[0137] Reference again Fig. 6A, at step 608, it is determined whether the aLP detects possible crosstalk that may be caused by the vLP performing ventricular pacing (more specifically, the vLP delivering pacing pulses). If the answer to the determination at step 608 is no, step 610 is skipped and the process proceeds to step 612. If the answer to the determination at step 608 is yes, the process proceeds to step 610. At step 610, the aLP initiates providing crosstalk protection during the crosstalk protection period to avoid crosstalk caused by ventricular pacing pulses from being erroneously detected as intrinsic atrial events. Such crosstalk protection can be performed in a variety of different ways. For example, the intrinsic activity sense amplifier 132 can be blanked by shorting its two inputs to each other or to ground so that there is a zero voltage difference between the voltages at the differential inputs. Alternatively or additionally, the output of the intrinsic activity sense amplifier 132 may not be provided to the controller 112 during the crosstalk protection period (e.g., by opening a switch). Alternatively or additionally, the output of the intrinsic activity sense amplifier 132 may be ignored by the controller 112 during a crosstalk protection period, i.e., the crosstalk protection period may be implemented by firmware and / or software of the controller 112. Other variations are possible and are within the scope of the embodiments described herein. Instead of performing blanking at step 610, the aLP (and more specifically, its controller) may ignore intrinsic atrial events detected during the crosstalk protection period, as it may be assumed that such detected intrinsic atrial events are actually crosstalk caused by ventricular pacing performed by the vLP. In some embodiments, crosstalk protection may involve, for example, blanking a sensing circuit for a period of time that the LP uses to monitor intrinsic events of the chamber in which (or on which) the LP is implanted. Alternatively or additionally, crosstalk protection (performed in response to detecting possible crosstalk) may involve ignoring any possible inherent depolarization detected by the sensing circuit of LP during the time period, disabling the sensing circuit of LP during the time period, ignoring any interrupt during the time period (generated in response to the sensing circuit being used to detect possible inherent depolarization), or disabling the generation of an interrupt during the time period (which may be generated in response to the sensing circuit detecting the inherent depolarization), but is not limited to the above. Such crosstalk protection may be performed under the assumption that any possible inherent depolarization detected when performing crosstalk protection is actually due to crosstalk. After step 608, the process proceeds to step 612. Corresponding to Fig. 6A The boxes of steps 606 , 608 , and 610 in are shown with dashed lines to show that these steps are optional, and that the flow may instead go directly from step 604 to step 612 .

[0138] As described above, in some embodiments, when steps 604 and 634 are performed to provide AAI+VVI operation, there is no i2i communication between aLP and vLP. In other words, AAI+VVI operation is achieved without any i2i message being sent from aLP to vLP (directly, or via a third IMD acting as a communication hub), and vice versa. Although i2i communication is not used by aLP and vLP, aLP may typically disable its (one or more) receivers (e.g., 120 and 122) and temporarily enable one or more of its receivers from time to time to sense possible crosstalk and / or determine whether a mode switching message is received from vLP. More specifically, at step 612, aLP determines whether it is time to temporarily enable its receiver 120 to monitor i2i messages of the mode switching type from vLP (or a third IMD acting as a communication hub). If the answer to the determination of step 612 is no, the process returns to step 604, and aLP continues to provide AAI operation. If the answer to the determination at step 612 is yes, then flow moves to step 614 and the aLP temporarily enables its receiver 120 to monitor for mode switch type i2i messages from the vLP (or third IMD).

[0139] For example, the aLP may temporarily enable its receiver 120 once per time period (e.g., once every 10 seconds, once every minute, once every 5 minutes, or once every 10 minutes, etc.) within a specified duration (e.g., 1 second, 2 seconds, 5 seconds, or 10 seconds, etc.) or a specified number of cardiac cycles (e.g., 1 cardiac cycle, 2 cardiac cycles, 5 cardiac cycles, or 10 cardiac cycles, etc.) at step 614. Alternatively, the aLP may temporarily enable its receiver 120 once per specified number of cardiac cycles (e.g., 10 cardiac cycles, 30 cardiac cycles, 60 cardiac cycles, or 120 cardiac cycles, etc.) within a specified duration (e.g., 1 second, 2 seconds, 5 seconds, or 10 seconds, etc.) or a specified number of cardiac cycles (e.g., 1 cardiac cycle, 2 cardiac cycles, 5 cardiac cycles, or 10 cardiac cycles, etc.). It is also possible that the low power receiver 120 of the aLP is always on, and the high power receiver 122 is selectively temporarily enabled in response to the low power receiver 120 receiving a wake-up pulse of an i2i mode switch message received from the vLP. If the low power receiver 120 of the aLP has been enabled to provide crosstalk protection (according to steps 606, 608, and 610), or is always on (also referred to as always enabled) and is in the process of providing crosstalk protection (by performing one of steps 606, 608, or 610), then at step 612, the aLP may be reconfigured to start listening for and processing possible i2i messages. This reconfiguration of the aLP may be achieved, for example, by updating low-level i2i communication hardware registers to enable the i2i hardware (e.g., the high power receiver 122) to receive i2i payloads, or it may be a logic reconfiguration, but is not limited thereto.

[0140] At step 616, it is determined whether the aLP receives an i2i message of a mode switch type from the vLP during the time period when the receiver of the aLP or a portion thereof is enabled. If the answer to the determination at step 616 is no, the process returns to step 604 and the aLP continues to provide AAI operation. If the answer to the determination at step 616 is yes, the process goes to step 618. In some embodiments, the aLP abstains from sending any i2i messages intended to coordinate the operation of the vLP with the aLP until the aLP receives an i2i message of a mode switch type from the vLP (or a third IMD).

[0141] At step 618, the aLP sends a mode switch acknowledgement (ACK) type i2i message to the vLP, and the aLP then changes its operation mode from providing AAI operation independently of the vLP to providing coordinated dual-chamber operation (e.g., DDD, VDD, DDI, VDI, or DOO operation) with the vLP, during which i2i messages are sent by the aLP and the vLP (to support the coordinated dual-chamber operation), as indicated by step 620. While jointly providing the coordinated dual-chamber operation, the aLP and the vLP send i2i messages to each other (e.g., on a heartbeat-by-heartbeat basis) or to a third IMD that acts as a communication hub for the aLP and the vLP.

[0142] At step 622, it is determined whether the aLP has received an additional mode switch type i2i message from the vLP. If the answer to the determination at step 622 is no, the flow returns to step 620, and the aLP continues to provide coordinated dual-chamber operation with the vLP, during which i2i messages are sent by the aLP and the vLP (to support coordinated dual-chamber operation). If the answer to the determination at step 622 is yes, the flow proceeds to step 624.

[0143] At step 624, the aLP sends another mode switch acknowledgement (ACK) type i2i message to the vLP, and the flow returns to step 604, and the aLP returns to providing AAI operation again. At this point, the aLP may return to generally disabling its receiver or a portion thereof, since there is no need to use heartbeat-by-heartbeat i2i communication during AAI+VVI operation.

[0144] Reference now Fig. 6A The steps shown on the right, as described above, at step 632, the vLP uses its sense amplifier (e.g., 132) to sense the vEGM, and the vLP (and more specifically, its controller) uses the vEGM to detect intrinsic ventricular events, such as R waves. Also as described above, step 634 involves the vLP providing VVI operation. Although the vLP provides VVI operation at step 634, and the aLP simultaneously provides AAI operation at step 604, but independently of each other, according to embodiments of the present technology, the dual chamber LP system (e.g., 100) provides AAI+VVI operation together.

[0145] In order to reduce the probability that the vLP will falsely detect a paced atrial event as an intrinsic ventricular event, at step 636, the vLP monitors for possible crosstalk that may be caused by atrial pacing performed by the aLP. For example, such possible crosstalk monitoring at step 636 may be performed using one of the techniques described in U.S. Pat. No. 10,182,765, which is incorporated herein by reference. At step 638, it is determined whether the vLP detects possible crosstalk that may be caused by atrial pacing performed by the aLP (more specifically, the aLP delivering pacing pulses). If the answer to the determination at step 638 is no, step 640 is skipped and the process proceeds to step 642. If the answer to the determination at step 638 is yes, the process proceeds to step 640. At step 640, the vLP initiates providing crosstalk protection during the crosstalk protection period to avoid crosstalk caused by atrial pacing pulses from being falsely detected as intrinsic ventricular events. Depending on the implementation, the crosstalk protection period utilized at the instance of step 640 may have the same duration or a different duration than the crosstalk protection period utilized at the instance of step 610. Such crosstalk protection may be performed in a variety of different ways, examples of which are discussed above with reference to step 610 and therefore need not be repeated. Instead of performing blanking at step 640, the vLP (and more specifically, its controller) may ignore intrinsic ventricular events detected during the crosstalk protection period, as it may be assumed that such detected intrinsic ventricular events are actually crosstalk caused by atrial pacing performed by the aLP. Fig. 6A The boxes of steps 636, 638, and 640 in FIG. 6 are shown with dashed lines to show that these steps are optional, and alternatively, the flow may go directly from step 634 to step 642. It is also possible that only one of the vLP and aLP monitors possible crosstalk from the other. More specifically, steps 636, 638, and 640 may be performed, but steps 606, 608, and 610 may not be performed. Alternatively, steps 606, 608, and 610 may not be performed, but steps 636, 638, and 640 may be performed.

[0146] Still reference Fig. 6AAt step 642, the vLP monitors a first specified criterion, which, if met, would indicate that there should be a mode switch from AAI+VVI operation to coordinated dual-chamber operation (e.g., one of DDD, VDD, DDI, VDI, or DOO operation). According to certain embodiments, the first specified criterion that the vLP determines whether is met includes the vLP providing at least a first specified threshold amount of ventricular pacing within a first specified duration. For example, the first specified criterion may be whether the vLP delivers ventricular pacing pulses during at least a specified percentage (e.g., 70% or some other percentage) of the most recent cardiac cycles, or whether the vLP delivers ventricular pacing pulses during at least a specified number N (e.g., N=7, or some other number) of cardiac cycles during the most recent number M (e.g., M=10, or some other number>N) of cardiac cycles, or whether the vLP delivers ventricular pacing pulses within a specified duration (e.g., 1 minute, 2 minutes, or 5 minutes, etc.). Other variations are possible and are within the scope of the embodiments described herein. In some embodiments, the vLP forgoes the use of its transmitter to send any i2i messages to the aLP (or to a third IMD acting as a communication hub for the LP) that are intended to be used by the aLP to coordinate pacing with the vLP when the vLP provides VVI operations. Although the vLP forgoes the use of its transmitter to send such i2i messages to the aLP, the vLP may also disable or at least partially disable its receiver to further save power.

[0147] At step 644, a determination is made as to whether the first specified criteria are met. If the answer to the determination at step 644 is no, the process returns to step 634 and the vLP continues to provide VVI operation. This also causes the aLP to continue to provide AAI operation. If the answer to the determination at step 644 is yes, the process proceeds to step 646. At step 646, the vLP sends a mode switch type i2i message to the aLP. As part of step 646, or just before step 646, the vLP may enable its transmitter (if the transmitter has been disabled to save power) to send i2i messages to the aLP, and the vLP may also enable one or more of its (one or more) receivers (if its receivers have previously been disabled to save power) to listen for mode switch ACK i2i messages that may be sent by the aLP. More generally, at step 644, a determination is made as to whether the dual-chamber LP system should switch from AAI+VVI operation to coordinated dual-chamber operation when the patient's need for ventricular pacing support becomes more than infrequent or intermittent.

[0148] At step 648, a determination is made by the vLP (more specifically, its controller) as to whether the vLP received a MODE SWITCH ACK i2i message from the aLP. If the answer to the determination at step 648 is no, the process returns to step 646 and the vLP sends another MODE SWITCH i2i message to the aLP. This may continue until the answer to the determination at step 648 is yes, or until there is some timeout. If the answer to the determination at step 648 is yes, the process proceeds to step 650. At step 650, the vLP changes its mode of operation from providing VVI operation to providing coordinated dual-chamber operation with the aLP, during which i2i messages are sent by the aLP and the vLP (to support coordinated dual-chamber operation). As described above, while jointly providing coordinated dual-chamber operation, the aLP and the vLP send i2i messages (e.g., on a beat-by-beat basis) to achieve coordinated dual-chamber therapy. The coordinated dual chamber operation provided by the aLP and vLP together at steps 620 and 650 may or may not be rate responsive, depending on how the dual chamber LP system is programmed.

[0149] Still reference Fig. 6A At step 652, the vLP monitors a second specified criterion, and if the second specified criterion is met, it will indicate that there should be a mode switch from coordinated dual chamber operation back to AAI+VVI operation. According to some embodiments, the second specified criterion that the vLP determines whether to be met includes the vLP providing less than a second specified threshold amount of ventricular pacing within a second specified duration. The second specified threshold used at step 652 can be the same as the first specified threshold used at step 642, or can be different from (e.g., less than) the first specified threshold used at step 642 to provide hysteresis. For example, the second specified criterion can be whether the vLP delivers ventricular pacing pulses during less than a specified percentage of the most recent cardiac cycles (e.g., 30% or some other percentage), or delivers ventricular pacing pulses during a specified number N (e.g., N=30, or some other number) of cardiac cycles during less than the most recent number M (e.g., M=100, or some other number>N), or delivers ventricular pacing pulses within a specified duration (e.g., 1 minute, 2 minutes, or 5 minutes, etc.).

[0150] At step 654, a determination is made as to whether a second specified criterion is met. If the answer to the determination at step 654 is no, the process returns to step 650 and the vLP continues to provide coordinated dual chamber operation in conjunction with the aLP. If the answer to the determination at step 654 is yes, the process passes to step 656. At step 656, the vLP sends another mode switch type i2i message to the aLP (or to a third IMD acting as a communication hub for the LP). More generally, at step 654, a determination is made as to whether the dual chamber LP system should switch from coordinated dual chamber operation back to AAI+VVI because the patient's need for ventricular pacing has returned to being relatively infrequent or intermittent.

[0151] At step 658, it is determined by the vLP (more specifically, its controller) whether the vLP has received an additional Mode Switch ACK i2i message from the aLP. If the answer to the determination at step 658 is no, the flow returns to step 656 and the vLP sends another additional Mode Switch i2i message to the aLP. This may continue until the answer to the determination at step 658 is yes, or until there is some timeout. If the answer to the determination at step 658 is yes, the flow returns to step 634 and the vLP returns to providing VVI operation. This also causes the aLP to return to providing AAI operation, and therefore causes the dual chamber LP system (e.g., 100) to return to providing the new AAI+VVI operation. In certain embodiments, to save power and thereby increase the lifespan of aLP and vLP, once the dual chamber LP system (e.g., 100) has returned to providing AAI+VVI operation, the aLP forgoes sending any i2i messages intended to coordinate the operation of the vLP with the aLP when the vLP provides VVI operation, and the vLP forgoes sending any i2i messages intended to coordinate the operation of the aLP with the vLP when the aLP provides AAI operation. In other words, once AAI+VVI operation is returned, AAI+VVI operation is provided without the need to send any i2i messages from the aLP to the vLP (directly, or via a third IMD acting as a communication hub), and vice versa.

[0152] Reference above Fig. 6A In the described embodiments, the aLP and vLP modes switch from providing AAI+VVI operation to jointly providing coordinated dual chamber operation, and vice versa. As described above, AAI operation may or may not be rate responsive, and VVI operation may or may not be rate responsive, depending on how the dual chamber LP system is programmed.

[0153] According to certain embodiments of the present technology, when the aLP provides AAI operation and the vLP provides VVI operation (the two are independent of each other), the aLP monitors for a specific criterion (referred to as a third designated criterion) that, when detected by the aLP, causes the aLP to send an i2i message to the vLP (or to a third IMD acting as a communication hub for the LP) indicating that the vLP has changed (e.g., increased) its basic pacing rate (e.g., from 40 ventricular beats per minute to 60 ventricular beats per minute, but not limited thereto), or equivalently, indicating that the vLP has changed (e.g., shortened) its basic VV interval. For example, the third designated criterion may be that the aLP has detected that the atrial rate exceeds a certain designated threshold (e.g., 170 atrial beats per minute, but not limited thereto). In order for the vLP to be able to receive such i2i messages, the vLP should temporarily enable its receiver from time to time in a manner similar to the manner in which the aLP does so at steps 612 and 614. The aLP may repeatedly send such a message until the aLP receives an ACK message that the vLP received the message, in a manner similar to what the vLP did at steps 646 and 648. Thereafter, the aLP may monitor for a fourth criterion, such as that the atrial rate has dropped below a specified threshold or some other specified threshold (e.g., 130 atrial beats per minute to provide hysteresis, but not limited thereto). In response to the aLP detecting the fourth criterion, the aLP sends an i2i message to the vLP (or to a third IMD acting as a communication hub for the LP) that instructs the vLP to change (e.g., reduce) its basic pacing rate (e.g., from 60 ventricular beats per minute back to 40 ventricular beats per minute, but not limited thereto), or equivalently instructs the vLP to change (e.g., increase) its basic VV interval. The aLP may repeatedly send such an i2i message until the aLP receives an ACK message that the vLP received the message. This is similar to the operations performed by the vLP at steps 652, 654, 656, and 658. The purpose of such an embodiment is to attempt to provide enhanced ventricular pacing support during atrial fibrillation (AF) and / or another type of atrial tachycardia without requiring beat-to-beat i2i communication during the atrial tachycardia.

[0154] In certain embodiments, the aLP and vLP jointly provide AAI+VVI operation without any mode switching to jointly provide coordinated dual-chamber operation. Figure 6BThe flowchart in shows how such a dual chamber LP system may operate. In such an embodiment, the aLP and vLP may completely forgo sending i2i messages to each other, or may send i2i messages to each other infrequently. As with the embodiment outlined above, AAI operation may or may not be rate responsive, and VVI operation may or may not be rate responsive, depending on how the dual chamber LP system is programmed. Figure 6B The boxes of steps 606, 608 and 610 in are shown with dashed lines to show that these steps are optional. Figure 6B The boxes of steps 636, 638, and 640 in FIG. 5 are shown with dashed lines to illustrate that these steps are optional.

[0155] Fig. 6A and Figure 6B The steps performed by the aLP in can be performed under the control of the aLP's controller (e.g., 112) by appropriately configuring the aLP using its firmware and / or software. Similarly, Fig. 6A and Figure 6B The steps performed by the vLP in may be performed under the control of a controller (eg, 112) of the vLP by appropriately configuring the vLP using its firmware and / or software.

[0156] Figure 7 A block diagram of one embodiment of an LP 701 (eg, 102a or 102b) implanted in a patient as part of an implantable cardiac system according to some embodiments herein is shown.

[0157] LP 701 has a housing 700 to hold the electronic / computing components. Housing 700 (which is often referred to as a "can," "housing," "encapsulation," or "housing electrode") can be programmably selected to be used as a return electrode for certain stimulation modes. LP is shown to include electrode terminals 702, 704, 706, 708, and 710, however, depending on how many electrodes the LP has, the LP will likely include only two or three electrode terminals.

[0158] The terminals may be connected to electrodes located at various locations on the housing 700 or elsewhere in and around the heart. LP 701 includes a programmable microcontroller 720 that controls various operations of LP 701, including cardiac monitoring and stimulation therapy. Microcontroller 720 includes a microprocessor (or equivalent control circuitry), RAM and / or ROM memory, logic and timing circuits, state machine circuits, and I / O circuits.

[0159] LP 701 also includes a pulse generator 722 that generates stimulation pulses and communication pulses for delivery by one or more electrodes coupled to the pulse generator 722. The pulse generator 722 is controlled by the microcontroller 720 via control signals 724. The pulse generator 722 can be coupled to select electrodes via electrode configuration switches 726, which include multiple switches for connecting the desired electrodes to the appropriate I / O circuits, thereby facilitating electrode programmability. The switches 726 are controlled by control signals 728 from the microcontroller 720.

[0160] exist Figure 7 In the embodiment of , a single pulse generator 722 is shown. Alternatively, the IMD may include multiple pulse generators similar to pulse generator 722, wherein each pulse generator is coupled to one or more electrodes and controlled by microcontroller 720 to deliver (multiple) selected stimulation pulses to the corresponding one or more electrodes.

[0161] The microcontroller 720 is shown to include a timing control circuit 732 for controlling the timing of stimulation pulses (e.g., pacing rate, atrioventricular (AV) delay, interatrial conduction (AA) delay, or interventricular conduction (VV) delay, etc.). AA delay may also be referred to as AA interval, and VV delay may also be referred to as VV interval. The timing control circuit 732 may also be used for timing of refractory period, blanking interval, noise detection window, induced response window, alarm interval, flag channel timing, etc. The microcontroller 720 also has an arrhythmia detector 734 for detecting arrhythmia conditions. The microcontroller 720 also has an AV synchronization detector 736, which may be configured to determine an AV synchronization metric according to an embodiment of the present technology described herein. Although not shown, the microcontroller 720 may also include other dedicated circuits and / or firmware / software components to assist in monitoring various conditions of the patient's heart and managing pacing therapy. The microcontroller may include a processor. The microcontroller and / or its processor may be used to perform the methods of the present technology described herein.

[0162] LP 701 is also equipped with a communication modem (modulator / demodulator) 740 to enable wireless communication with a remote slave pacing unit. Modem 740 may include one or more transmitters and two or more receivers, as described herein. Figure 1As discussed. In one embodiment, the modem 740 can use low frequency or high frequency modulation. As an example, the modem 740 can send i2i messages and other signals through conductive communication between electrode pairs. The modem 740 can be implemented in hardware as part of the microcontroller 720, or as software / firmware instructions programmed into and executed by the microcontroller 720. Alternatively, the modem 740 can reside separately from the microcontroller as an independent component.

[0163] LP 701 includes a sensing circuit 744 that is selectively coupled to one or more electrodes that perform sensing operations through switch 726 to detect the presence of cardiac activity in the right chamber of the heart. Sensing circuit 744 may include a dedicated sensing amplifier, a multiplexed amplifier, or a shared amplifier. It may also employ one or more low-power precision amplifiers, bandpass filtering, and threshold detection circuits with programmable gain and / or automatic gain control to selectively sense cardiac signals of interest. Automatic gain control enables the unit to sense low amplitude signals characteristic of atrial fibrillation. Switch 726 determines the sensing polarity of the cardiac signal by selectively closing the appropriate switch. In this way, the clinician can program the sensing polarity independently of the stimulation polarity.

[0164] The output of the sensing circuit 744 is connected to the microcontroller 720, which in turn triggers or inhibits the pulse generator 722 in response to the presence or absence of cardiac activity. The sensing circuit 744 receives a control signal 746 from the microcontroller 720 for controlling the gain, threshold, polarization charge removal circuit (not shown), and the timing of any blocking circuit (not shown) coupled to the input of the sensing circuit.

[0165] exist Figure 7 In the embodiment of FIG. 7 , a single sensing circuit 744 is shown. Alternatively, the IMD may include multiple sensing circuits similar to sensing circuit 744, wherein each sensing circuit is coupled to one or more electrodes and controlled by microcontroller 720 to sense electrical activity detected at the corresponding one or more electrodes. Sensing circuit 744 may operate in a unipolar sensing configuration or in a bipolar sensing configuration.

[0166] LP 701 also includes an analog-to-digital (A / D) data acquisition system (DAS) 750 coupled to one or more electrodes via switch 726 to sample cardiac signals on any desired electrode pair. Data acquisition system 750 is configured to acquire intracardiac electrogram signals, convert raw analog data to digital data, and store the digital data for later processing and / or telemetry transmission to an external system 754 (e.g., a programmer, a local transceiver, or a diagnostic system analyzer). Data acquisition system 750 is controlled by control signals 756 from microcontroller 720.

[0167] The microcontroller 720 is coupled to the memory 760 via a suitable data / address bus. Programmable operating parameters used by the microcontroller 720 are stored in the memory 760 and are used to customize the operation of the LP 701 to suit the needs of a particular patient. Such operating parameters define, for example, pacing pulse amplitude, pulse duration, electrode polarity, rate, sensitivity, automatic features, arrhythmia detection criteria, and the amplitude, waveform, and vector of each stimulation pulse to be delivered to the patient's heart. The memory 760 may also store programmable parameters used to perform the above reference. Fig. 6A and 6B Instructions for at least some of the steps in the described method.

[0168] The operating parameters of LP 701 can be non-invasively programmed into memory 760 by telemetry circuit 764, which is in telemetric communication with external system 754 via communication link 766. Telemetry circuit 764 allows intracardiac electrograms and status information related to the operation of LP 701 (such as contained in microcontroller 720 or memory 760) to be sent to external system 754 via communication link 766.

[0169] LP 701 may also include a magnet detection circuit (not shown) coupled to microcontroller 720 to detect when a magnet is placed on the unit. The clinician may use the magnet to perform various test functions of LP 701 and / or signal to microcontroller 720 that external system 754 is in place to receive data or send data to microcontroller 720 via telemetry circuit 764.

[0170] LP 701 may also include one or more physiological sensors 770. Such sensors are often referred to as "rate-responsive" sensors because they are often used to adjust the pacing stimulation rate based on the patient's exercise state. However, physiological sensors 770 may also be used to detect changes in cardiac output, changes in the physiological condition of the heart, or diurnal changes in activity (e.g., detecting sleep and wake states). Signals generated by physiological sensors 770 are transmitted to microcontroller 720 for analysis. Microcontroller 720 responds by adjusting various pacing parameters (such as rate, AV delay, VV delay, etc.) for applying atrial and ventricular pacing pulses. Although shown as being included within LP 701, (one or more) physiological sensors 770 may be external to LP 701, but still implanted in the patient or carried by the patient. Examples of physiological sensors may include, for example, sensors that sense respiratory rate, blood pH, ventricular gradient, activity, position / posture, minute ventilation (MV), etc.

[0171] Battery 772 provides operating power to all components in LP 701. Battery 772 is capable of operating for long periods of time at low current consumption. Battery 772 also desirably has predictable discharge characteristics so that selective replacement time can be detected. As an example, LP 701 employs lithium / silver vanadium oxide batteries.

[0172] LP 701 also includes impedance measurement circuitry 774, which can be used for many things, including: lead impedance monitoring during acute and chronic phases for proper lead positioning or displacement; detecting operable electrodes and automatically switching to operable electrode pairs if displacement occurs; measuring respiration or minute ventilation; detecting when the device is implanted; measuring stroke volume; and detecting the opening of heart valves; etc. Impedance measurement circuitry 774 is coupled to switch 726 so that any desired electrodes can be used.

[0173] It should be understood that the subject matter described herein is not limited in its application to the details of the construction and arrangement of the components set forth in the description herein or shown in the drawings thereof. The subject matter described herein can have other embodiments and can be practiced or executed in various ways. In addition, it should be understood that the wording and terminology used herein are for the purpose of description and should not be considered as limiting. The use of "including", "comprising" or "having" and its variations herein is intended to cover the items listed thereafter and their equivalents and additional items. In addition, it should be noted that, unless otherwise stated, the term "based on" as used herein should be interpreted as meaning at least partially based on, meaning that there may be one or more additional factors for making a decision, etc. For example, if the decision is based on the result of a comparison, then in addition to being based on the result of the comparison, the decision can also be based on one or more other factors.

[0174] Embodiments of the present technology have been described above with the aid of functional building blocks that illustrate the execution of specified functions and their relationships. For ease of description, the boundaries of these functional building blocks are generally defined herein. Alternative boundaries may be defined, as long as the specified functions and their relationships are appropriately provided. Therefore, any such alternative boundaries are within the scope and spirit of the claimed invention. For example, the embodiments of the present invention may be combined or separated. Fig. 6A and 6B Some of the steps shown in . Fig. 6A and 6B For another example, you can change Figure 2 and Figure 7 Boundaries of some of the blocks shown in .

[0175] It should be understood that the above description is intended to be illustrative rather than restrictive. For example, the above embodiments (and / or aspects thereof) can be used in combination with each other. In addition, without departing from the scope of the present technology, many modifications can be made to adapt specific situations or materials to the teachings of the embodiments of the present technology. Although the size and type of the materials and coatings described herein are intended to limit the parameters of the embodiments of the present technology, they are by no means restrictive, but exemplary embodiments. After reading the above description, many other embodiments will be apparent to those skilled in the art. Therefore, the scope of the embodiments of the present technology should be determined with reference to the appended claims and the full scope of the equivalents given by these claims. In the appended claims, the terms "including" and "wherein (in which)" are used as the plain English equivalents of the corresponding terms "including" and "wherein (wherein)". In addition, in the appended claims, the terms "first", "second" and "third" etc. are used only as labels and are not intended to impose numerical requirements on their objects. Furthermore, the appended claim limitations are not written in a means-plus-function format and are not intended to be interpreted based on 35 U.S.C. §112(f) unless and until such claim limitations expressly use the phrase “means for…” followed by a recitation of functionality without further structure.

Claims

1. A method for use with a dual-chamber leadless pacemaker LP system, the dual-chamber leadless pacemaker LP system comprising an atrial leadless pacemaker aLP and a ventricular leadless pacemaker vLP, the method comprising: The aLP provides an AAI operation during which the aLP performs atrial pacing when an intrinsic atrial event is not detected within a designated AA interval following a prior pace or intrinsic atrial event, performs atrial sensing, and inhibits the atrial pacing when an intrinsic atrial event is detected within the designated AA interval following the prior pace or intrinsic atrial event; and The vLP provides a VVI operation during which the vLP performs ventricular pacing when an intrinsic ventricular event is not detected within a designated VV interval following a prior pace or intrinsic ventricular event, performs ventricular sensing, and inhibits the ventricular pacing when an intrinsic ventricular event is detected within the designated VV interval following the prior pace or intrinsic ventricular event; The aLP providing the AAI operation and the vLP providing the VVI operation occur during the same first time period and are independent of each other.

2. The method according to claim 1, wherein: Each leadless pacemaker LP of the aLP and the vLP comprises a respective transmitter enabling the LP to send implant-to-implant i2i messages, comprises a respective receiver enabling the LP to receive i2i messages, and comprises a respective power supply for powering the transmitter and the receiver of the LP, the method further comprising: During the same first time period in which the aLP provides the AAI operation and the vLP provides the VVI operation, the aLP waives sending any i2i messages intended to coordinate the operation of the vLP with the aLP, and the vLP waives sending any i2i messages intended to coordinate the operation of the aLP with the vLP.

3. The method according to claim 1, wherein: The designated AA interval is shorter than the designated VV interval so that the atrial rate of the atrial pacing performed by the aLP is faster than the ventricular rate of the ventricular pacing performed by the vLP.

4. The method according to claim 1, wherein: The aLP includes a sensor that enables the aLP to monitor the activity level of a patient in whom the aLP and the vLP are implanted; and When the aLP provides the AAI operation and the vLP provides the VVI operation, the aLP adjusts the atrial rate of the atrial pacing performed by the aLP by adjusting the designated AA interval based on the activity level of the patient detected by the sensor using the aLP, and the vLP does not adjust the ventricular rate of the ventricular pacing performed by the vLP.

5. The method according to claim 1, wherein Each leadless pacemaker LP in the aLP and the vLP comprises a corresponding sense amplifier, The sense amplifier of the aLP is configured to sense an atrial electrogram aEGM for detecting intrinsic atrial events, The sense amplifier of the vLP is configured to sense a ventricular electrogram vEGM for detecting intrinsic ventricular events; and When the aLP provides the AAI operation and the vLP provides the VVI operation, the method further includes at least one of the following: The aLP monitors for possible crosstalk that may be caused by the vLP performing the ventricular pacing, and in response to the aLP detecting the possible crosstalk that may be caused by the vLP performing the ventricular pacing, the aLP initiates performing crosstalk protection for a first crosstalk protection duration; or The vLP monitors for possible crosstalk that may be caused by the aLP performing the atrial pacing, and in response to the vLP detecting the possible crosstalk that may be caused by the aLP performing the atrial pacing, the vLP initiates performing crosstalk protection for a second crosstalk protection duration.

6. The method according to any one of claims 1 to 5, wherein each leadless pacemaker LP of the aLP and the vLP comprises a respective transmitter enabling the LP to send implant-to-implant i2i messages, comprises a respective receiver enabling the LP to receive i2i messages, and comprises a respective power supply for powering the transmitter and the receiver of the LP, and The method further comprises: The vLP determines whether a first specified criterion is met; During a first time period in which the first specified criterion is not met, the vLP abstains from using the transmitter of the vLP to send any i2i messages intended for coordinating operation of the aLP with the vLP; as well as During a second time period commencing in response to satisfying the first specified criterion, the vLP uses the transmitter of the vLP to send a mode switch type i2i message which, if successfully received and acknowledged by the aLP, causes the aLP and the vLP to jointly provide coordinated dual chamber operation.

7. The method according to claim 6, further comprising: the aLP typically disabling at least a portion of the corresponding receiver of the aLP that enables the aLP to receive one or more i2i messages, thereby conserving power from the power supply of the aLP as compared to a situation where the at least a portion of the corresponding receiver of the aLP is enabled; as well as the aLP temporarily enabling, from time to time, the at least a portion of the receiver of the aLP enabling the aLP to receive one or more i2i messages, thereby enabling the aLP to monitor the i2i messages of the mode switch type; as well as The aLP receives the mode switch type i2i message and in response sends a mode switch confirmation message and together with the vLP provides the coordinated dual chamber operation.

8. The method according to claim 6, wherein: The vLP determines whether a first specified criterion is satisfied includes the vLP providing at least a first specified threshold amount of ventricular pacing for a first specified duration.

9. The method according to claim 6, further comprising: After the vLP has switched from providing the VVI mode of operation to co-providing the coordinated dual chamber operation with the aLP, the vLP determines whether a second specified criterion is satisfied; and During a third time period beginning in response to satisfying the second specified criterion, the vLP sends an additional mode switch type i2i message using the transmitter of the vLP, and if the additional mode switch type i2i message is successfully received and confirmed by the aLP, the aLP is switched from the dual-chamber operation mode of providing the coordination together with the vLP to the aLP again providing the AAI operation independently of the vLP, and the vLP is switched from the dual-chamber operation mode of providing the coordination together with the aLP to the vLP again providing the VVI operation independently of the aLP.

10. The method according to claim 9, wherein: The second specified criterion that the vLP determines to be satisfied includes the vLP providing less than a second specified threshold amount of ventricular pacing within the second specified duration.

11. The method according to claim 6, wherein: The coordinated dual chamber operation includes DDD operation.

12. The method according to claim 6, wherein: The coordinated dual chamber operation includes one of VDD, DDI, VDI or DOO operation.

13. A dual-chamber leadless pacemaker LP system, comprising: an atrial leadless pacemaker aLP configured to be implanted in or on an atrial heart chamber of a patient's heart; as well as a ventricular leadless pacemaker vLP configured to be implanted in or on a ventricular heart chamber of a patient's heart; wherein, during the same time period and independently of each other, the aLP is configured to provide AAI operations and the vLP is configured to provide VVI operations; wherein when the aLP provides the AAI operation, when an intrinsic atrial event is not detected within a specified AA interval after a previous pace or an intrinsic atrial event, the aLP performs atrial pacing, performs atrial sensing, and when the intrinsic atrial event is detected within the specified AA interval after the previous pace or the intrinsic atrial event, inhibits the atrial pacing; and Wherein, when the vLP provides the VVI operation, when an intrinsic ventricular event is not detected within a specified VV interval after a previous pacing or an intrinsic ventricular event, the vLP performs ventricular pacing, performs ventricular sensing, and when the intrinsic ventricular event is detected within the specified VV interval after the previous pacing or the intrinsic ventricular event, inhibits the ventricular pacing.

14. The system of claim 13, wherein: each leadless pacemaker LP in the aLP and the vLP comprises a respective transmitter enabling the LP to send implant-to-implant i2i messages, comprises a respective receiver enabling the LP to receive i2i messages, and comprises a respective power supply for powering the transmitter and the receiver of the LP; and During the same first time period in which the aLP provides the AAI operation and the vLP provides the VVI operation independently of each other, the aLP is configured to abandon sending any i2i messages intended to coordinate the operations of the vLP with the aLP, and the vLP is configured to abandon sending any i2i messages intended to coordinate the operations of the aLP with the vLP.

15. The system of claim 13, wherein: The designated AA interval is shorter than the designated VV interval so that the atrial rate of the atrial pacing performed by the aLP is faster than the ventricular rate of the ventricular pacing performed by the vLP.

16. The system of claim 13, wherein: The aLP includes a sensor that enables the aLP to monitor the activity level of a patient in whom the aLP and the vLP are implanted; Each LP in the aLP and the vLP includes a corresponding controller; the controller of the aLP being configured to adjust the atrial rate of the atrial pacing performed by the aLP by adjusting the designated AA interval based on the activity level of the patient detected using the sensor of the aLP while the aLP is providing the AAI operation; and The controller of the vLP is configured to not adjust a ventricular rate of the ventricular pacing performed by the vLP while the vLP provides the VVI operation.

17. The system of claim 13, wherein: The aLP includes a sense amplifier configured to sense an atrial electrogram aEGM used by the aLP to detect intrinsic atrial events; The vLP includes a sense amplifier configured to sense a ventricular electrogram vEGM used by the vLP to detect intrinsic ventricular events; The aLP includes a controller communicatively coupled to the sense amplifier of the aLP; The vLP includes a controller communicatively coupled to the sense amplifier of the vLP; as well as the controller of the vLP being configured to monitor for possible crosstalk that may be caused by the aLP performing the atrial pacing while the vLP is providing the VVI operation, and in response to detecting the possible crosstalk that may be caused by the aLP performing the atrial pacing, initiate providing crosstalk protection for a first crosstalk protection period; The controller of the aLP is configured to monitor possible crosstalk that may be caused by the vLP performing the ventricular pacing while the aLP provides the AAI operation, and in response to detecting the possible crosstalk that may be caused by the vLP performing the ventricular pacing, initiate providing crosstalk protection within a second crosstalk protection period.

18. A system according to any one of claims 13 to 17, wherein: each leadless pacemaker LP of the aLP and the vLP comprises a respective transmitter enabling the LP to send implant-to-implant i2i messages, comprises a respective receiver enabling the LP to receive i2i messages, and comprises a respective battery for powering the transmitter and the receiver of the LP; The aLP includes a controller communicatively coupled to the transmitter and the receiver of the aLP and powered by the battery of the aLP; The vLP includes a controller communicatively coupled to the transmitter and the receiver of the vLP and powered by the battery of the vLP; the controller of the vLP being configured to determine whether a first specified criterion is satisfied, to abstain from using the transmitter of the vLP to send any i2i messages intended for use by the aLP to coordinate operation with the vLP during a first time period when the first specified criterion is not satisfied, and to cause the transmitter of the vLP to send an i2i message of a mode switch type in response to the first specified criterion being satisfied; as well as If the mode switch type i2i message is successfully received and acknowledged by the aLP, the aLP and the vLP are enabled to jointly provide coordinated dual-chamber operation.

19. The system of claim 18, wherein: The controller of the aLP is configured to: normally disabling at least a portion of the receiver of the aLP that enables the aLP to receive one or more i2i messages from the vLP, thereby conserving power of the battery of the aLP compared to a situation where the at least a portion of the receiver of the aLP is enabled; temporarily enabling at least a portion of the receiver of the aLP from time to time that enables the aLP to receive one or more i2i messages from the vLP, thereby enabling the aLP to monitor for mode switch type i2i messages that cause the aLP to switch from providing the AAI operating mode to jointly providing the coordinated dual chamber operation with the vLP; as well as In response to the aLP receiving and confirming the mode switch type i2i message from the vLP, the aLP is switched from providing the AAI operation mode to jointly providing the coordinated dual-chamber operation with the vLP.

20. The system of claim 18, wherein: The controller of the vLP is configured to determine whether a first specified criterion that is satisfied includes the vLP providing at least a first specified threshold amount of ventricular pacing for a first specified duration.

21. The system of claim 18, wherein: The vLP controller is configured to: determining whether a second specified criterion is satisfied after the vLP has switched from providing the VVI mode of operation to co-providing the coordinated dual chamber operation with the aLP; and During a third time period beginning in response to satisfying the second specified criterion, the transmitter using the vLP sends an additional mode switch type i2i message to the aLP, and if the additional mode switch type i2i message is successfully received and acknowledged by the aLP, the aLP is switched from the dual-chamber operation mode in which the coordination is provided jointly with the vLP to the aLP again providing the AAI operation independently of the vLP, and the vLP is switched from the dual-chamber operation mode in which the coordination is provided jointly with the aLP to the vLP again providing the VVI operation independently of the aLP.

22. The system of claim 21, wherein: The controller of the vLP is configured to determine whether a second specified criterion that is satisfied includes the vLP providing less than a second specified threshold amount of ventricular pacing for a second specified duration.

23. The system of claim 18, wherein: The coordinated dual chamber operation includes DDD operation.

24. The system of claim 18, wherein: The coordinated dual chamber operation includes one of VDD, DDI, VDI or DOO operation.

25. A method for use with a dual-chamber leadless pacemaker (LP) system comprising an atrial leadless pacemaker aLP and a ventricular leadless pacemaker vLP, the method comprising: During the same first time period in which the aLP and the vLP give up communicating with each other, the aLP provides AAI operations and the vLP provides VVI operations independently of each other; and During a second time period that begins in response to satisfying a first specified criterion, the vLP and the aLP communicate with each other and switch from a mode in which the aLP provides AAI operations and the vLP provides VVI operations independently of each other to a mode in which the aLP and the vLP jointly provide one of DDD, VDD, DDI, VDI or DOO operations.

26. The method according to claim 25, further comprising: During a third time period beginning in response to satisfying a second specified criterion, the aLP and the vLP switch from jointly providing one of DDD, VDD, DDI, VDI or DOO operations back to the vLP again providing the VVI operation and the vLP again providing the VVI operation independently of each other.

27. The method of claim 26, wherein: The first specified criterion is satisfied when the vLP provides at least a first specified threshold amount of ventricular pacing for a first specified duration; and The second specified criterion is met when the vLP provides ventricular pacing less than a second specified threshold amount for a second specified duration.

Images