Intracardiac communication providing direct timing information using ultrasound without an electrical interface

Abstract

To provide a system capable of using a communication pathway that does not compete with electrical activity within the heart tissue.SOLUTION: A medical system 1 contains a first implantable device 10 and a second implantable device 20. Each implantable device 10, 20 contains communication units 11, 21. The communication units 11, 21 are configured to transmit an ultrasonic signal to the communication units 21, 11 of another implantable devices 20, 10 of the medical system 1.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to medical systems, and more particularly to pacemaker systems comprising at least first and second implantable leadless pacemakers. [Background technology]

[0002] A leadless pacemaker system requires at least one implanted leadless pacemaker for each chamber in which pacing is to occur. One role of a two- (or even three-) chamber pacemaker system is to correct broken intrinsic timing connections between the chambers. Another role is to control the rate at which pacing occurs, and thereby the timing of the entire cardiac cycle in a manner that meets the patient's cardiac needs.

[0003] Because the leadless pacemakers in such systems do not have wires to carry information from one chamber to another, some form of communication between the chambers is required to allow the rate and timing synchronization necessary to meet these requirements.

[0004] Communication of event timing information is time critical: an event in one chamber can immediately trigger a corresponding behavior in another chamber. Communication of other types of information may not be time critical. For example, if a pacing rate is calculated in one chamber, it may be useful for a leadless pacemaker in another chamber to share this information, but the timing of the information exchange does not convey any additional information needed. Another type of data communication can be done to allow one leadless pacemaker to configure the behavior of another leadless pacemaker to provide coordinated system behavior. Configuration information is typically not time critical, although it may be necessary to use synchronization signals to allow both devices to switch settings simultaneously.

[0005] In particular, US 2015 / 0224320 A1 discloses a leadless pacemaker system comprising a first leadless cardiac pacemaker that can be implanted at a first cardiac site and a second leadless cardiac pacemaker that can be implanted at a second cardiac site, the first pacemaker configured to communicate information related to cardiac events sensed by the first pacemaker at the first cardiac site to the second pacemaker.

[0006] Moreover, document U.S. Patent No. 9,623,251 B2 describes a leadless cardiac pacemaker system comprising a first leadless cardiac pacemaker configured for implantation in a ventricular site and a second leadless cardiac pacemaker configured for implantation in an atrial site, the second pacemaker configured to sense atrial contractions, the first pacemaker and second pacemaker configured to be communicatively coupled such that the second pacemaker can communicate sensed atrial contractions to the first pacemaker.

[0007] Furthermore, the publication US 2015 / 0335894A1 discloses a distributed leadless implantable system comprising first and second leadless implantable medical devices configured to be generally implanted within first and second chambers of a heart, each of the first and second devices comprising a housing having a proximal end configured to engage a local tissue of interest in the local chamber, electrodes located along the housing, cardiac sensing circuitry configured to detect intrinsic and paced cardiac events occurring in a near-field associated with the local chamber, and detecting events of interest occurring in the local chamber based on analysis of the intrinsic and paced events. and a pulse sensing circuit configured to detect at least one of a paced event or an initiation pulse occurring in the far field, the paced event or initiation pulse occurring in a far chamber different from a corresponding local chamber, the initiation pulse having a predetermined pattern configured to indicate that an event of interest has occurred in the far chamber, and the controller configured to recognize at least one of the paced event or the initiation pulse indicative of an occurrence of an event of interest in the far chamber and, in response, to initiate an associated action in the local chamber.

[0008] Typically in two implanted systems such as the one described above, some information exchanges in the systems are time-critical and, in some cases, directly triggered by intrinsic cardiac events, so messages may occur simultaneously, resulting in collisions in which some information may be lost.

[0009] In particular, when the pathway for information exchange is via modulated electrical pulses conducted within cardiac tissue, the inherent electrical activity in the tissue can interfere with data transmission. A typical solution is to only send data during the refractory period, but this prevents the sending of time-critical event flags. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] US Patent Application Publication No. 2015 / 0224320A1 [Patent Document 2] U.S. Patent No. 9,623,251B2 [Patent Document 3] U.S. Patent Application Publication No. 2015 / 0335894A1 Summary of the Invention [Problem to be solved by the invention]

[0011] Based on the above, it is an object of the present invention to provide a system that is capable of using communication paths that do not compete with electrical activity in the cardiac tissue.

[0012] It would further be desirable to classify communication between devices in different cardiac chambers into time-critical and non-time-critical messages, and to provide a collision avoidance mechanism for sending non-time-critical information. [Means for solving the problem]

[0013] There is provided a medical system according to claim 1 and a medical system according to claim 13. Further embodiments are subject matter of the dependent claims.

[0014] In one aspect, a medical system is disclosed, the medical system comprising at least a first implantable device and a second implantable device, each implantable device comprising a communication unit configured to transmit ultrasonic signals (e.g., modulated ultrasonic pressure waves) to communication units of other implantable devices of the medical system.

[0015] According to an embodiment of the medical system, each communication unit comprises a piezoelectric transducer.

[0016] Moreover, according to an embodiment of the medical system, each communication unit is configured to receive ultrasonic signals (eg, modulated ultrasonic pressure waves) from the other communication units.

[0017] In particular, a piezoelectric-based ultrasound transducer in each implantable device can be electrically stimulated to produce modulated pressure waves that can carry information to other devices. The same transducer generates proportional electrical signals in response to the incoming modulated pressure waves. In particular, these signals can be filtered and amplified before being demodulated to recover the transmitted information.

[0018] Further, according to embodiments, each transducer is isolated from biological tissue by being sealed within a housing, and the housing also serves to isolate the battery and / or electronics of each implantable device (e.g., an implantable leadless pacemaker) from the patient's tissue. In particular, the mechanical interface between each transducer and the housing is designed to allow mechanical coupling between the pressure waves of the biological environment and the transducer.

[0019] Moreover, in accordance with an embodiment of the medical system, the first implantable device is a first implantable leadless pacemaker configured for implantation in an atrium (e.g., the right atrium) of the patient's heart and the second implantable device is a second implantable leadless pacemaker configured for implantation in a ventricle (e.g., on the same side as the atrium, e.g., the right ventricle) of the patient's heart.

[0020] In particular, each implantable leadless pacemaker comprises a pacing electrode disposed in a pacemaker housing, the housing configured to be secured to a heart wall in an atrium or ventricle.

[0021] Implantable devices for implantation within the atria of a patient's heart need to be very small and have a very long service life because of the small size of the atrium. Industry expectations are that degraded implantable leadless pacemakers need to be deactivated and discarded because removing a long-term implant from the heart is risky. While this becomes unavoidable, with devices implanted in the atria, it should be avoided for as long as possible because it may not be possible to fit a replacement device into the same atrial chamber as the degraded implant that is being discarded. By relieving the implantable atrial device of the burden of having a CPU and / or pacemaker timer circuitry, the implantable atrial device can be smaller and consume less battery capacity at a given time, increasing the usable service life.

[0022] Further, according to an embodiment of the medical system, the first implantable device is configured to detect a cardiac event in the atrium (e.g., an atrial contraction) and transmit a corresponding ultrasound signal (also referred to as a sensing marker) through its communication unit to the second implantable device, the ultrasound signal being indicative of the detected cardiac event.

[0023] Further, according to an embodiment of the medical system, the second implantable device is configured to transmit an ultrasonic command signal to the first implantable device, and the first implantable device is configured to generate and apply a pacing pulse to the atrium upon receiving the ultrasonic command signal.

[0024] Further, according to an embodiment of the medical system, the second implantable device comprises an antenna (e.g., an electromagnetic coil) for receiving a programming signal from an external programming device of the medical system, and the first implantable device is configured to be programmed via the second implantable device. For example, the second implantable device may be configured to transfer a programming signal in the form of an ultrasound programming signal generated by the programming device, or a portion of said programming signal, to the first implantable device.

[0025] Because the first implantable device may be programmed by the ventricular device, the first implantable device does not require the relatively large coil that would be required to enable inductive communication with an external programming device. In particular, according to an embodiment, the second implantable device may be configured to use events reported from other devices, such as the first implantable device, to include a pacemaker timer for the overall medical system.

[0026] Further, according to an embodiment of the medical system, the medical system includes a third implantable device configured to transmit ultrasound signals to the first and / or second implantable device and / or configured to receive ultrasound signals from the first and / or second implantable device. Such a third implantable device (e.g., in the form of a subcutaneous device) may be used, for example, to provide capture confirmation when pacing occurs as an input to a pacemaker timer.

[0027] Even when there are only two implantable devices in a medical (e.g., cardiac) system, communication collisions may occur unless the protocol explicitly avoids when communication collisions may occur. In particular, in an embodiment of a medical system, the system comprises three or more implantable devices. For example, a subcutaneous device may be used to monitor the status of a body area network and provide the possibility of RF (radio frequency)-based communication from a deep implant to a home monitoring system. Furthermore, replacement scenarios often require coordination between devices to ensure proper operation of the replacement device before shutting down the degraded device.

[0028] A communication protocol that allows master / slave coordination messages to be exchanged between implanted devices must handle time-critical messages such as sensing markers, pace commands, and configuration synchronization commands, as well as less time-critical messages such as those used to query statistics from the devices and configure them. Time-critical messages must be sent as the environment dictates. Therefore, it is inherently more difficult to prevent collisions of time-critical messages. An analysis of the time-critical messages required in a simple pacemaker system reveals that only one particular concentration of events can cause such collisions.

[0029] This is the case when the pacemaker timer determines that an atrial pace should be delivered at the same moment that an intrinsic atrial sense occurs. In this case, the pacemaker timer is reset the same whether the event is a pace or a sense, the delivery of an atrial pace simultaneously with an intrinsic cardiac depolarization will not affect the heart, and therefore the pacemaker system will be in a safe and correct state whether or not either message is successfully delivered to the other implant. When two ultrasound messages are transmitted simultaneously by different implants, the most likely outcome is that neither message is properly received. Loss of one of the non-time-critical messages may result in a less correct state for the system, for example, a configuration change is ignored or a statistical item is not reported. Thus, according to an embodiment, a time-critical atrial event is used as a time reference that allows prioritization of other messages between implantable devices in the medical / pacemaker system.

[0030] Further, according to an embodiment of the medical system, the first implantable device is configured to apply a pacing pulse to the atrium or sense an (atrial) cardiac event every cardiac cycle, and the first implantable device is configured to send, after a predetermined period of time after said cardiac event or pacing pulse, using the communication unit of the first implantable device, a broadcast message in the form of an ultrasound signal to at least the second implantable device (or to all other implantable devices in the medical system), wherein the broadcast message indicates whether a cardiac event or a pacing pulse has occurred.

[0031] In particular, the predetermined period may range from 5 seconds to 90 seconds, in particular from 5 seconds to 50 seconds, preferably from 5 seconds to 20 seconds. A period of 5 to 20 seconds allows to wait long enough for any disturbance from an event to end, but also leaves plenty of refractory period available for messages to intervene.

[0032] Further, according to an embodiment of the medical system, each implantable device is configured to start a timer upon receiving a broadcast message indicating that a cardiac event has occurred or a pacing pulse has occurred, and the timer in each implantable device is configured to expire for a duration before terminating due to a time-out, each duration being a unique duration different from the durations of other implantable devices in the system.

[0033] In particular, according to an embodiment, every message generated by each embedded device comprises an address identifier indicating to which target (e.g. the first or second embedded device) the message is being sent, and in particular one of the address identifiers is a broadcast address identifier indicating that the respective message is being sent to all devices in the system (e.g. the second and especially the third embedded device).

[0034] Moreover, according to an embodiment, the duration of the timer of each embedded device depends on the address identifier of the embedded device, in particular the shorter the duration the higher the priority of the embedded device for being able to send messages.

[0035] More specifically, the communication unit (e.g., its message decoder) in each embedded device in the system is configured to decode all messages at least until the address identifier is determined. If the respective communication unit (e.g., decoder) determines that it is the target of the message, i.e., the received address identifier matches its own predefined address identifier, then the remainder of the message is decoded as well. More specifically, messages targeted to a broadcast address are fully decoded by all embedded devices in the system.

[0036] Further, according to an embodiment of the medical system, each implantable device comprises a control unit configured to schedule the transmission of messages through a communication unit of each implantable device, and each implantable device is configured to store a message to be sent as a pending message in its communication unit and to set a flag indicating the pending message.

[0037] Further, according to an embodiment of the medical system, the communication unit of each implantable device is configured to determine, upon timeout of a timer in the implantable device, whether the receiving circuitry of the implantable device is in the process of receiving an incoming message, and if so, no message is sent by the communication unit until at least the next timeout, and if no message is being received and said flag is set, the communication unit is configured to send a pending message, which effectively inhibits other implants from sending lower priority, non-time critical messages while it is being sent.

[0038] A further aspect of the invention relates to a medical system comprising at least a first implantable device and a second implantable device, each implantable device comprising a communication unit configured to transmit a message (e.g. in the form of a modulated ultrasonic pressure wave) to the communication units of the other implantable devices, the first implantable device configured to periodically transmit a broadcast message to at least the second implantable device (in particular to all implantable devices of the system) using the communication unit of the first implantable device, the broadcast message indicating that an event has occurred, the first implantable device configured to transmit the broadcast message a predetermined period after the event, each implantable device configured to start a timer upon receiving the broadcast message indicating the occurrence of the event, the timer of each implantable device configured to allow a duration to elapse before terminating due to a time-out, each duration being a unique duration different from durations given to other devices of the medical system.

[0039] As mentioned above, according to an embodiment, the first implantable device can be a first implantable leadless pacemaker configured to be implanted in an atrium (e.g., the right atrium) of the patient's heart and the second implantable device can be a second implantable leadless pacemaker configured to be implanted in a ventricle (e.g., on the same side as the atrium, e.g., the right ventricle) of the patient's heart. In particular, the event can be an (atrial) cardiac event detected by the first implantable device or a pacing pulse applied to the atrium by the first implantable device. More particularly, the predetermined period of time can have the values ​​already mentioned above.

[0040] In particular, according to an embodiment, here too, all messages generated by the communication unit of the respective embedded device may comprise an address identifier indicating to which target (e.g. the first or the second embedded device) the message is being sent, in particular one of the address identifiers is a broadcast address identifier indicating that the respective message is being sent to all embedded devices of the system (e.g. the second and in particular the third embedded device).

[0041] Moreover, according to an embodiment, again the duration of the timer of each embedded device may depend on the address identifier of the embedded device, in particular, as explained above, the shorter the duration, the higher the priority of the embedded device for being able to send messages.

[0042] More particularly, the communication unit (e.g., its message decoder) of each embedded device in the system is configured to decode all messages, at least until the address identifier is determined. Once the respective communication unit (e.g., decoder) determines that it is the target of the message, i.e., the received address identifier matches its own predefined address identifier, it decodes the remainder of the message as well. In particular, messages targeted to a broadcast address are fully decoded by all embedded devices in the system.

[0043] Further, according to an embodiment of the medical system, each implantable device comprises a control unit configured to schedule the transmission of messages through a communication unit of the implantable device, and each implantable device is configured to store a message to be sent as a pending message in its communication unit and to set a flag indicating the pending message.

[0044] Further, according to an embodiment of the medical system, the communication unit of each implantable device is configured to determine, at the timeout of a timer of each implantable device, whether the receiving circuitry of each implantable device is in the process of receiving an incoming message, and if a message is in the process of being received, no message will be sent by the communication unit until at least the next timeout, and if a message is not being received and the flag is set, the communication unit is configured to send a pending message.

[0045] In the following examples, the features and advantages of the present invention are explained with reference to the drawings. [Brief description of the drawings]

[0046] [Figure 1] 1 illustrates a schematic diagram of an embodiment of a medical system. [Diagram 2] 1 illustrates a schematic diagram of a first embodiment of an intracardiac pacing device. [Diagram 3] FIG. 2 illustrates a schematic diagram of a second embodiment of an intracardiac pacing device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] FIG. 1 illustrates an example of a medical system 1 comprising a first implantable device 10 and a second implantable device 20, each of the implantable devices 10, 20 comprising a communication unit 11, 21 configured to transmit ultrasound signals to a communication unit 21, 11 of another implantable device 20, 10 of the medical system 1.

[0048] Here, illustratively, the first and second implantable devices 10, 20 are formed by implantable leadless pacemakers 10, 20, where the first implantable leadless pacemaker 10 is implanted in an atrium (e.g., right atrium) 2a of a patient's heart 2 and the second implantable leadless pacemaker 20 is implanted in a ventricle 2b of the heart 2. For cardiac pacing of the heart 2, it is very important to maintain, in particular, atrioventricular (AV) synchrony. AV synchrony means that in the (normal) activation sequence of the heart, the atrium contracts first and then the ventricle contracts after a proper delay, called the atrioventricular (AV) delay. If the timing between the two chambers becomes out of sync, less blood is delivered with each beat and cardiovascular output is reduced. Therefore, proper communication should be achieved between the devices 10, 20 to be able to provide proper pacing.

[0049] For this purpose, each chamber 2a, 2b of the heart 2 that needs to be paced is preferably equipped with a leadless pacemaker 10, 20 capable of sensing cardiac events in that chamber (e.g., atrial or ventricular contractions, respectively) and pacing the heart in that chamber 2a, 2b. According to an embodiment, each device 10, 20 has a piezoelectric transducer 12, 22 capable of transmitting modulated ultrasonic pressure waves that can propagate through the cardiac tissue to the device 10, 20 in the other chamber 2a, 2b. In particular, the same transducer 11, 12 can also convert the received modulated pressure waves into an electrical signal that can be demodulated to recover the originally transmitted signal.

[0050] In particular, according to an embodiment, the communication units 11, 21 of each device 10, 20 are equipped with a hardware-based state machine implementing a protocol whereby for time-sensitive messages, messages are sent immediately or for non-time-sensitive messages, messages are delayed until a specific time slot.

[0051] Even if there are only two implantable devices 10, 20 in the system 1, communication collisions may occur unless the protocol explicitly avoids times when communication collisions may occur. Preferably, in an embodiment, the system 1 may also include three or more implantable devices 10, 20. For example, as also shown in FIG. 1, a subcutaneous device (third implantable device) 40 may be used to monitor the status of the body area network and provide the possibility of radio frequency based communication from deep implants to the home monitoring system.

[0052] In particular, in a medical system 1 such as a pacemaker system including the first and second implantable leadless pacemakers 10, 20 as depicted in FIGURE 1, time critical messages can be: an atrial sense marker (i.e., a message indicating an atrial cardiac event) preferably broadcast from the first device to all other devices 20 in the system 1; a "Sync After Pace" related message preferably sent from the first device 10 to all other devices 20 in the system; a "Sync After Sense" related message preferably sent from the first device 10 to all other devices 20 in the system; a command message or signal sent from the second device 20 to the first device 10 causing the first device 10 to apply a pacing pulse to the atrium 2a; and a "Do Cross Channel Blanking" related message sent from the second device 20 to the first device 10. "Sync After Pace" indicates that a pacing pulse has occurred. "Synchronize after sense" indicates that a cardiac event has occurred. Thus, the broadcast message indicates whether a cardiac event or a pacing pulse has occurred. If the pacemaker in one chamber is going to pace, the sense detection circuits in the other chambers should be blanked (prohibited from sensing) during the pacing period to avoid false sense detection due to pacing effects in the other chambers. The blanking period can be predefined, so that only the start of this blanking period needs to be communicated to the chambers that are not going to pace. This is done by the message "Perform cross-channel blanking". This is a time-critical message, since it tells the receiving device when it needs to do something (starting immediately).

[0053] On the other hand, messages that require lower priority and are not time critical may relate to messages sent from a second device to a first device to initiate one of the following: Write to Register, Read from Register, Activate Program on next sync, Disable Permanently, or may relate to messages sent from a first device to a second device to initiate, for example, a Read from Register Response. Registers are memory locations in a device that configure how the device should behave. Writing to a register is done to change the settings. Reading a register is used to tell how the device was previously configured. Registers may also be used to pass status information about something that has occurred. Program activation is used to tell the device that it should use a predefined collection of registers to change its own settings at a particular point in time, specifically at some point in the next cardiac interval. A permanent deactivation is a command for a device to completely and permanently shut itself down as it is being replaced by a new device. When a message requests some information from another device (i.e. a command to read from a register), the addressed device sends a response message that specifies that it is a response to a previous request.

[0054] Preferably, every cardiac cycle, a first device 10 in the atrium 2a either paces or detects an atrial intrinsic sense (a cardiac event in the atrium 2a). After a defined period of time, which may be, for example, about 10 seconds, from this event, the atrial device 10 sends out a broadcast message indicating that it has paced or sensed. This message serves as a reference point for the time slot of non-time-critical messages.

[0055] To this end, each implantable device 10, 20 is preferably configured to start a timer upon receiving a broadcast message indicating the occurrence of a cardiac event or a pacing pulse, and the timer of each implantable device 10, 20 is configured to expire for a duration before terminating due to a time-out, each duration being a unique duration different from the durations of the other implantable devices 20, 10 in the system 1.

[0056] In particular, every message generated by each embedded device 10, 20 comprises an address identifier indicating to which target (e.g. the first or second embedded device 10, 20) the message is being sent. In particular, one of the address identifiers is a broadcast address identifier indicating that the respective message is being sent to all devices in the system (e.g. the second embedded device 20).

[0057] In particular, the duration of the timer of each embedded device 10, 20 depends on the address identifier of the respective embedded device 10, 20. The shorter the duration, the higher the priority of the embedded device 10, 20 for being able to send messages.

[0058] Moreover, in particular, the communication unit (e.g., its message decoder) 11, 21 in each embedded device 10, 20 in the system 1 is configured to decode all messages, at least until the address identifier is determined. If the respective communication unit (e.g., decoder) 11, 21 determines that it is the target of the message, i.e., the received address identifier matches its own predefined address identifier, then the remainder of the message is decoded as well. In particular, messages targeted to a broadcast address are fully decoded by all embedded devices 10, 20 in the medical system 1.

[0059] In particular, as shown in Fig. 1, each embedded device 10, 20 preferably comprises a control unit 14, 24 configured to schedule the transmission of messages through the communication unit 11, 21 of the respective embedded device 10, 20, each embedded device 10, 20 being configured to store messages to be sent as pending messages in its communication unit 11, 21 and to set a flag indicating a pending message. Furthermore, the communication unit 11, 21 of each embedded device 10, 20 is configured to determine, at the timeout of a timer of the corresponding embedded device 10, 20, whether the receiving circuit of the respective embedded device 10, 20 is in the process of receiving an incoming message. If so, no message will be sent by the respective communication unit 11, 21 until at least the next timeout, and if no message is being received and said flag is set, the corresponding communication unit 11, 21 is configured to send a pending message. While it is being sent, this message effectively prohibits the sending of lower priority, non-time-critical messages by other implants. In particular, when two ultrasound messages are transmitted simultaneously by different implantable devices of system 1, the most likely outcome is that neither message will be properly received. Only when collisions of time-critical messages are likely are all possible communication outcomes resistant. Time-critical messages must be sent at the same time that an event occurs or is being triggered. The system may attempt to trigger atrial pacing at the same time that an atrial sense occurs. In this case, the triggering message and the sense detection message may corrupt each other, but the system will be in a valid state even if one, the other, or both of the messages are not properly received. No other simultaneous pairs of time-critical messages are anticipated.

[0060] In other words, each implantable device 10, 20 has a unique predefined delay (duration of the corresponding timer) after which it can start sending a waiting message. The state machine of the communication unit 11, 21 handling the sending of messages always checks for the presence of an ultrasound carrier frequency before starting the transmission. Every message packet always starts with an active start bit. The protocol prohibits the start of a message when an active message is already in progress. The priority of the devices results from whichever device 10, 20 has the shortest delay (i.e. the duration of the respective timer) after the time slot reference point indicated by the respective broadcast message related to an atrial pacing event or a detected atrial cardiac event.

[0061] Preferably, the packet definition of the protocol includes a bit indicating the address of the message recipient. One address is reserved to indicate that the message is broadcast to all recipients. The receiving state machine of each communication unit 11, 21 detects if an incoming message is targeted to its device and processes only those messages that it is meant to receive. Preferably, the addresses are configurable to allow for the steady replacement of an almost degraded device 10, 20 with a new one. The old device address is changed to something different from the factory address so that the new factory device can be controlled separately in the system 1 until it has passed clinical testing. At this point, the old device can be deactivated while the new device is fully operational.

[0062] The medical system 1 illustrated in FIG. 1 is simplified by having a single pacemaker timer subsystem in the second device 20. This pacemaker timer can command pacing in other devices (e.g., in the first device 10) using targeted pace commands (time-sensitive messages). Senses in the other devices 10 can be communicated by the pacemaker timer to the second device 20 using sense flag broadcast messages (also time-sensitive messages).

[0063] If electrical noise interferes with sensing detection in a conventional pacemaker, the pacemaker transitions to noise mode. In this mode, sensing cannot be reliably detected, so the pacemaker paces asynchronously to ensure that cardiac support is provided whether or not adequate intrinsic cardiac activity is present. When noise mode is active, some pacemaker features change their behavior. This type of information can be shared among leadless devices in all chambers using "Start Noise" and "End Noise" broadcast markers.

[0064] Furthermore, one device 10, 20 may send configuration messages to another device 20, 10 in the form of Write commands to specific registers of the destination device (see above). These registers may use double buffering to delay activation of the new settings until a Transfer Registers command is sent to change all registers to the new settings simultaneously. Write commands are non-time sensitive messages. Transfer Registers commands may be time sensitive commands that support configuration changes with intrinsic cardiac timing.

[0065] The invention avoids the need for far-field sensing from another chamber in a multi-device medical system such as a leadless pacemaker system. Thanks to the ultrasonic communication, the footprint of the atrial device may be reduced. This also reduces the battery capacity required at a given time due to the fact that the burden of the atrial device to have a CPU and / or pacemaker timer circuitry is relieved. Since the atrial device 10 may be programmed by the ventricular device 20 (which may use simultaneous inductive communication to the external programming device 30), the atrial device 10 does not require the relatively large coils required to enable inductive communication with the external programming device 30. In particular, the ventricular device 20 may include a pacemaker timer for the overall system 1 and may use events reported from other devices such as the atrial device 10 as inputs to the timing logic. Furthermore, a subcutaneously implanted third device 40 may also be used to provide capture confirmation when pacing occurs (see FIG. 1). Furthermore, the invention allows for a steady replacement scheme for degraded devices. Finally, the present invention provides a general mechanism for exchanging information between devices without conflicting or interfering with the electrical signals resulting from cardiac events.

[0066] 2 illustrates a schematic diagram of an intracardiac pacing device (also called an implantable leadless pacemaker). The device comprises a housing 100 enclosing an energy storage 102 (e.g., a battery), an electrode module 103, a first communication unit 104, and a second communication unit 107. The housing 100 can include or be made of titanium.

[0067] A first electrode 106 (also referred to as a pacing / sensing electrode) is located at the distal end of the housing 100. A second electrode 101 (also referred to as a return electrode) is disposed at a proximal region of the housing 100. The second electrode 101 may be formed as a ring electrode.

[0068] The device may be secured to the cardiac tissue by fixation elements 105. The fixation elements may be formed as tines. The fixation elements may include or be made of Nitinol. In one embodiment, four tines 105 made of Nitinol may be formed at the distal end of the housing 100.

[0069] The energy store 102 may be configured to provide electrical energy to the components of the device, in particular the electronic module 103, the first communication unit 104, the second communication unit 107 and the first electrode 106.

[0070] The electronic module 103 may be configured to perform the functions of a pacemaker, including sensing cardiac events and delivering pacing pulses. The electronic module 103 may include a processor, memory, and / or state machine logic.

[0071] The first communication unit 104 may be configured for communication with an external device (e.g., a programmer). The first communication unit may be formed as a coil for inductive communication.

[0072] The second communication unit 107 may be configured for transmitting and / or receiving ultrasound waves. It may be a piezoelectric transducer.

[0073] 3 illustrates another embodiment of an intracardiac pacing device, which has the same components as in FIG. 2 except for the first communication unit. Thus, this other device can only communicate via ultrasound. By omitting the first communication unit, this other device can have a smaller form factor than the device according to FIG. 2.

[0074] In light of the above teachings, it will be apparent to one of ordinary skill in the art that many modifications and variations of the described examples and embodiments are possible. The disclosed examples and embodiments are presented for illustrative purposes only. Other alternative embodiments may include some or all of the features disclosed herein. It is therefore intended to cover all such modifications and alternative embodiments that may fall within the true scope of the present invention.

Claims

1. A medical system (1) comprising at least a first implantable device (10) and a second implantable device (20), each implantable device (10, 20) comprising a communication unit (11, 21) configured to transmit an ultrasound signal to the communication unit (21, 11) of another implantable device (20, 10) of the medical system (1), the first implantable device (10) comprises an electronic module (103) and is configured to apply a pacing pulse to the atrium (2a) or to sense a cardiac event by means of said electronic module (103) every cardiac cycle, the first implantable device (10) being configured to transmit, after a predetermined period of time following said cardiac event or a pacing pulse, a broadcast message in the form of an ultrasound signal to at least the second implantable device (20) using said communication unit (11) of said first implantable device (10), said broadcast message indicating whether a cardiac event or a pacing pulse has occurred in said atrium (2a); Each of the implantable devices (10, 20) is configured to start a timer upon receiving a broadcast message indicating the occurrence of a cardiac event or the occurrence of a pacing pulse, the timer of each implantable device (10, 20) being configured to allow a duration to elapse before terminating due to a time-out, each of the durations being a duration specific to the implantable device (10, 20); A medical system (1), wherein the shorter the intrinsic duration of the implantable device (10, 20), the higher the priority of the implantable device (10, 20) for being able to perform cardiac pacing or send a message after the broadcast message related to the detected cardiac event.

2. The medical system of claim 1, wherein each of the communication units (11, 21) comprises a piezoelectric transducer (12, 22).

3. 3. The medical system according to claim 1 or 2, wherein each communication unit (11, 21) is configured to receive an ultrasound signal from another communication unit (21, 11) of the medical system (1).

4. 4. The medical system of claim 1, wherein the first implantable device (10) is a first implantable leadless pacemaker (10) and the second implantable device (20) is a second implantable leadless pacemaker (20).

5. 2. The medical system of claim 1, wherein the second implantable device (20) is configured to transmit an ultrasonic command signal to the first implantable device (10) through its communication unit (21), and the first implantable device (10) is configured, upon receiving the ultrasonic command signal, to generate and apply a pacing pulse to the atrium (2a) through its electronic module (103).

6. 6. The medical system of claim 1, wherein the second implantable device comprises an antenna (23) for receiving a programming signal from an external programming device (30), and the first implantable device (10) is configured to be programmed via the communication unit (21) of the second implantable device (20).

7. The medical system (1) according to any one of claims 1 to 6, further comprising a third implantable device (40) configured to transmit an ultrasound signal to the first and / or the second implantable device (10, 20) and / or to receive an ultrasound signal from the first and / or the second implantable device (10, 20).

8. Each of the embedded devices (10, 20) comprises a control unit (14, 24) configured to schedule the transmission of messages through the communication unit (11, 21) of each of the embedded devices (10, 20) to avoid collisions with messages from each of the other embedded devices (10, 20), each of the embedded devices (10, 20) being configured to store the messages to be sent in its communication unit (11, 21) as pending messages and to set a flag indicating a pending message, and each of the embedded devices (10, 20) is ...

8. The medical system according to claim 1, wherein at a timeout of the timer of each of the implantable devices (10, 20), a receiving circuit of the communication unit (11, 21) of each of the implantable devices (10, 20) is configured to determine whether an incoming message is being processed by the receiving circuit of the communication unit (11, 21) of each of the implantable devices (10, 20), and if a message is being processed, no message is sent by the communication unit (10, 20) until at least a next timeout, and if a message is not being received and the flag is set, the communication unit (10, 20) is configured to send the pending message.

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