Communication system and method for implantable medical devices

Abstract

The present invention is directed to a communication system 10 for wireless message transfer between an implantable medical device IMD 40 and an external device 60, the IMD 40 being configured to monitor a health status of a patient and / or deliver a therapy signal to the patient, the IMD 40 comprising a processor, a memory module, and a transceiver module configured to bidirectionally transmit messages to and receive messages from the external device 60. To provide a communication system and method that supports communication with multiple IMDs and enables a low overhead means for facilitating interaction specific to a target IMD as part of the IMD assembly and in-clinic use, the external device 60 is configured to send a predefined wake-up signal 100 to the transceiver module of the IMD combined with an ID request message 200 following the wake-up signal within a predefined first time interval T1A.

Description

Technical Field

[0001] The present invention is directed to a communication system for wireless message transfer between an implantable medical device (IMD) and an external device, where the IMD is configured to monitor a patient's health status and / or to deliver therapy signals to the patient. The external device is at least partially located outside the body. The present invention further relates to respective methods for wireless message transfer, respective computer program products, and respective computer-readable data carriers. The computer program product may be, for example, software routines associated with hardware support means within the IMD and / or within the external device.

Background Art

[0002] Active and passive implantable medical devices (IMDs), such as pacemakers (with leads), BioMonitors, implantable leadless pacers (ILPs), implantable leadless pressure sensors (ILPSs), implantable cardiac defibrillators (ICDs), or subcutaneous implantable cardiac defibrillators (i.e., S-ICDs), house sensors that collect physiological signals to monitor a patient's health status and transmit these signals as data to a physician's or patient's device, or to a remote server, using external equipment. Data collected from these various sensors, or from any of such sensors, may include, but are not limited to, ECG, impedance, activity, posture, heart sounds, pressure, respiration, and other data. Active IMDs (e.g., pacemakers, ILPs, ICDs, or S-ICDs) can provide patients with therapeutic outputs such as electrical stimulation within the cardiac chambers (e.g., atria or ventricles).

[0003] Typically, such an IMD consists of a processor for data processing and a transceiver module configured to exchange messages bidirectionally with an external device, for example, when implanted in a patient's body. In some cases, an external device using its own transceiver is configured to exchange messages bidirectionally with the IMD's transceiver module. The external device may be a separate device connected to a computer (called a programmer in some cases) or a module integrated within a remote device such as a computer. The external device sends messages to the IMD's transceiver, for example, in the form of requests to receive data from the IMD regarding the patient's health status or IMD status, or to program (to configure the IMD to apply appropriate therapy to the patient).

[0004] In modern IMDs, such as leaded cardiac rhythm management (CRM) implants, communication with external devices (e.g., connected to a programmer) has typically progressed without requiring the system to have knowledge of or interact with more than one IMD at a time. This long-standing convenience has unfortunately proven incompatible with use cases in leadless IMDs, particularly the needs at the end of service. In leadless situations, a communication scheme is needed to support the phased retirement and introduction of therapy support from "old" and "new" IMDs, as a common set of leads cannot be exchanged between two separate IMDs by rapid header connection swapping to deliver "new" therapy as a replacement for "old" IMDs placed in the exact same location within the patient's organ (e.g., the patient's heart). Furthermore, if the system is to support communication with more than one leadless IMD (even serially), it must be the case that no single such IMD interferes with external devices in a manner that prevents it from exchanging data with any other IMD or any other external device.

[0005] In cases where a conventional active IMD is always within the communication range of an external device, when such a conventional active IMD receives a "wake-up" signal (often via a high-energy pulse, i.e., HEP), depending on the protocol involved, it may be forced to transition to a state where the conventional active IMD immediately begins transmitting a response output. Such interaction can effectively negate any ability to communicate with multiple IMDs by creating a constant "spit-out" of data to the external device, which refuses to provide support for other devices to be recognized. Preceding CRM implant systems did not consider situations where another implant might need to communicate with an external device, and therefore there were little to no incentives to prevent any single device from completely occupying the acceptable range of the communication link. This type of interaction is particularly problematic in cases where the carrier rate is designed to be sufficiently low (e.g., 32 kHz) to facilitate signal transmission through the patient's anatomical tissue, because slower data rates encourage longer transmit-receive interactions, creating larger targets during the problematic temporal overlap of competing transmissions, any range of which may originate from other implants.

[0006] It should also be noted that some IMD communication support schemes common to the CRM market have historically used higher frequency carriers (e.g., 200 kHz) to enable faster data exchange. While such strategies, in an adapted form, may potentially allow more IMDs to interact non-competitively with external devices (assuming proper system design), attenuation of higher frequency signaling becomes increasingly problematic depending on the greater physical distance between the implant and the external device. In leadless IMDs (which are essentially placed deeper within the patient's anatomical tissue), the adoption of higher frequency communication strategies unfortunately necessitates drawing power that the implant does not adequately support, directly challenging the longevity of IMDs in this newly emerging type of product. [Overview of the project] [Problems that the invention aims to solve]

[0007] Accordingly, it is desirable to provide communication systems and methods that enable low-overhead means to support communication with multiple IMDs and facilitate target IMD-specific interactions as part of both IMD assembly and clinical use. [Means for solving the problem]

[0008] The above problem is solved by a communication system for wireless message transfer between an IMD and an external device having the features of claim 1, by each communication method having the features of claim 10, by a computer program product having the features of claim 14, and by a computer-readable data carrier having the features of claim 15. The computer program product may be a software routine and / or associated hardware support means for the IMD and the external device.

[0009] In detail, the problem is solved by a communication system for wireless message transfer between the IMD and the external device, including the IMD and the external device, the IMD being configured to monitor the patient's health status and / or to deliver therapeutic signals to the patient. The IMD comprises a processor, a memory module, and a transceiver module configured to exchange messages bidirectionally with the external device. The external device is configured to send a predefined wake-up signal to the transceiver module of the IMD, combined with an ID request message followed by a wake-up signal within a predefined first time interval, the ID request message containing one of a predefined set of different request specifications. The processor of the IMD is configured to generate an ID response message for the previously received ID request message and to send this ID response message from the transceiver module to the external device within a time slot after the receipt of the ID request message. The ID response message contains ID information read from a memory cell section at a predefined memory address of the memory module, the memory cell section being determined by the processor based on the request specification sent by a previously received ID request message, and the time slot being determined by the processor based on the ID information read from the determined section of the memory cell. The request specification may also be called an ID request command. Furthermore, the memory cell may also be called memory (without the cell designation).

[0010] Alternatively, or additionally, the IMD processor is configured to generate an ID response message in response to a previously received ID request message, and to send this ID response message from the transceiver module to an external device within a time slot after the receipt of the ID request message, wherein the ID response message contains ID information read from a predefined memory address of the memory module, the section of memory is determined by the processor based on the request specification sent by the previously received ID request message, and the time slot is determined by the processor based on the ID information read from the determined section of memory.

[0011] An IMD is an implantable medical device, as defined above, configured to monitor a patient's health status and / or to deliver therapeutic signals to a patient, such as an ILP, ILPS, or ICD.

[0012] An IMD comprises a processor for data processing and a transceiver module (e.g., an antenna or coil connected to appropriate communication management capabilities) for receiving messages (i.e., communication signals) from and sending messages to external devices. A request message is an instruction or command request sent to the IMD by an external device. Messages sent to external devices by the IMD's transceiver module function as response messages. Generally, a message is a sequence of bits embedded in a syntactic and semantic system defined as part of a communication protocol, represented and interpreted in clearly defined algorithms and data structures. Request messages received by the IMD's transceiver module are relayed to the processor for data processing. Similarly, the processor generates the content of a signal / message, which is then relayed to the transceiver module for sending as a response message to an external device.

[0013] The IMD may further include modules such as memory for storing data, a power supply unit including battery support and other components, at least one sensor for acquiring physiological signals from the patient, and / or a signal generator for generating and administering, for example, electrotherapy signals or electromagnetic therapy signals. The transceiver module, memory module, power supply unit, at least one sensor, and / or signal generator may be electrically connected to the processor.

[0014] IMD memory modules may include any volatile, non-volatile, magnetic, electrical, or other media, such as random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other memory storage type.

[0015] External devices are located at least partially outside the body and may be separate modules having a processor, and may be connected wirelessly or by wire to a computer (e.g., a physician's instrument, a remote server, a programmer). Alternatively, the external devices may form an integrated unit of such a computer, for example, an integrated unit of a programmer. For bidirectional communication, the external devices may include transceivers for messages (signals), for example, coils connected to a communication module. The communication module may include a processor, or, especially if it is a module located away from the computer, it may interface with a processor.

[0016] Wireless communication between external devices and the IMD includes wireless communication (wireless). Communication may use inductive magnetic means, acoustic methods (e.g., ultrasound), and / or acoustic waves, optical waves, and / or electromagnetic waves, such as Bluetooth, WLAN, ZigBee, NFC, Wibree, or WiMAX in the radio frequency domain, or infrared or IrDA or free-space optical (FSO) communication in the optical frequency domain.

[0017] In relation to the present invention, each processor is considered a functional unit of an IMD, external device, and / or computer that interprets and executes instructions, comprising an instruction control unit and an arithmetic logic unit. A (remote) computer or external device is a functional unit that can perform substantial calculations, including numerous arithmetic and logical operations, without human intervention, and is, for example, a personal mobile device (PMD), a desktop computer, a server computer, a cluster / warehouse-scale computer, or an embedded system.

[0018] In one embodiment, the IMD processor employs at least a predefined sleep state and a predefined active state. In the active state, the processor controls or takes measures to collect, aggregate, or (in one or more responses) outbound data, or to collect measurements, or execute routines, for example, for therapeutic application. Accordingly, in the active state, the processor operates to respond to external requests and / or to process data according to internal program sequences. Hereinafter, the active state may correspond to a “busy condition” that intentionally works to complete lengthy routines related to requests from external devices before signaling to the system that the IMD is ready to process any further command requests. However, in the sleep state, the processor is minimally involved in supporting communication through simple maintenance of the IMD (thus saving power), in situations where it can be invoked for further active state interaction. The IMD can only facilitate message / data exchange with further targets when transitioning to a higher-power active state condition. In one embodiment, the receiver circuit must demonstrate that it can communicate with the device whenever the healthcare provider (HCP) attempts to interact via an external device; therefore, the receiver circuit is running continuously during the IMD's service hours.

[0019] According to the present invention, at the start of communication with the IMD from an external device, the IMD's processor is initially in a sleep state, the external device sends a predefined wake-up signal to the IMD's transceiver module, the wake-up signal is combined with an ID request message that follows the wake-up signal within a predefined first time interval, the ID request message contains one of a distinct request command from a predefined set.

[0020] In one embodiment, the external device is configured to send a plurality of predefined wake-up signals to the IMD's transceiver module, each paired with an ID request message following a wake-up signal within a predefined first time interval, wherein a second such predefined wake-up signal follows the first such predefined wake-up signal within a predefined second time interval, the second time interval being longer than the first time interval. The first wake-up signal paired with the ID request message may be treated similarly to a known HEP ​​(i.e., noise-free). The first wake-up signal may be evaluated by the IMD to assist in adjusting gain settings within the system to support further communication, and the IMD may further initiate a process to confirm that the observed signaling is indeed a HEP input from the external device. In the next clustering grouping of wake-up signals and ID request messages, the IMD can verify that the signals are indeed valid wake-up inputs and then proceed to initiate the communication clock support and phase-locked loop (PLL) elements necessary to decode the baseline binary phase-shift keying (BPSK) communication signaling. By the time the third grouping of wake-up signals and ID request messages reaches the implant, the IMD's transceivers may be activated and ready for further communication.

[0021] In one embodiment, the wake-up signal is an initial 8-cycle pulse output train and a later 8-cycle pulse output train separated by an 8-cycle gap, resulting in an output with a 24-cycle gap. Other wake-up signals may also be used, for example, including a known 2-cycle high-energy clock pulse output (HEP) at 32.768 Hz, as used in the communication schemes of conventional products. According to the embodiment first mentioned, the HEP implementation of known conventional products has been modified to enable low-power wake-up for leadless support through the inclusion of a larger clock cycle count and an internal gap signature for identification. The increased cycle count and gap features make it easier to avoid susceptibility to noise input, thus improving wake-up support for deep implants without compromising the service time of the device by allowing the IMD to consume less power when recognizing an incoming HEP. The wake-up signal described above has the ability to be verified by a predefined pattern known to the IMD's processor or transceiver circuit (i.e., matching active pulses and gaps to a template), which may be used to ensure that the processor wake-up (i.e., transition from sleep state to active state) occurs only when intended, and also improves noise immunity. This revised HEP wake-up approach for deep implants further maintains the ability to similarly awaken conventional IMDs. In one embodiment, the pulse amplitude of the initial 8-cycle pulse output train may differ from the pulse amplitude of the later 8-cycle pulse output train. This multi-level segmentation of the output in the HEP sequence gives the IMD additional flexibility to determine which gain setting is best for subsequent baseline communication and to provide external equipment with feedback on the output amplitude to be used during said subsequent baseline communication.

[0022] Alternatively, or additionally, the wake-up signal may consist of a pulse output train that can be segmented into an initial segment and a later segment separated by an intervening gap, for example, where the pulse amplitude of the initial segment of the pulse output train is the same as or different from the pulse amplitude of the later segment of the pulse output train when compared.

[0023] According to the present invention, the ID request message following the wake-up signal represents one of a distinct ID request command from a predefined set, which may be randomly selected in the initiation of baseline communication and provisioning of time-multiplexed IMD responses, or may be selected according to rule-based selection as part of the process involved. The ID request message contains information for the IMD processor to read a memory address in the memory module, which is essential for properly handling the ID request message. For proper data exchange, the IMD must be within the communication range of external devices. Based on the sent request specification, the IMD processor reads information stored in the command-related section of the memory module. This information is called "ID information". In one embodiment, the memory address is the memory address of the IMD's serial number. In this embodiment, the ID information is a section of the IMD's serial number, and the ID request command determines which section of the IMD's serial number needs to be read, or should be read, by the IMD processor.

[0024] In one embodiment, an external device randomly or via rule-based criteria selects one of eight ID request commands from a set, each request command instructing the IMD's processor to select a different section of memory, for example, a 3-bit section of memory. Rule-based selection could include, for example, selecting the next ID request command in the family each time, which has a binary index value one greater or one less than the last used value, or selecting any second-largest or second-smallest value. If the maximum or minimum value is reached, the selection continues at the minimum or maximum value, respectively, i.e., by wrapping around. Other rules may also be applied.

[0025] Alternatively, or as an addition, an external device may be configured to randomly or according to a rule-based scheme select one of several ID request commands from a set, with each ID request command allowing the IMD processor to select a different section of memory.

[0026] The ID information may be a certain value, for example, a section of the serial number of the IMD. According to the present invention, based on the read ID information, the time slot in which the ID response message needs to be sent back to the external device is determined by the processor. In the case of two different IMDs (for example, each having a different serial number), there is a high probability that two different ID information values will be derived from their respective memory modules. Accordingly, the ID response messages of both IMDs will be sent by their transceivers using different time slots. This scheme is known as time-multiplexed response management. Thereby, the external device can distinguish between different IMDs. In the application of the discovery phase, such a time-multiplexing scheme enables multiple wireless IMDs to respond to an ID request message with a defined delay to support communication with the external device. Additionally, by recognizing any one of the IMDs within the communication range of the external device, it is guaranteed that it will not interfere with the system's ability to interact with other IMDs or, worse still, negate the visibility of the IMD to the communication infrastructure. The start of each time slot can represent a unique fixed delay relative to the end of the ID request message and can have a fixed length. Each time slot can have the same or a different length compared to other time slots.

[0027] In one embodiment, the processor selects one of eight different time slots based on the ID information (e.g., a 3-bit code) read from a determined section of the IMD's memory. The ID response message of the IMD can contain all or part of the IMD's serial number. Also, more or fewer than eight different time slots may be selected by the processor.

[0028] Alternatively, or in addition, the processor is configured to select one of a plurality of time slots for sending an ID response message by the transceiver module based on ID information read from a determined section of the memory.

[0029] As outlined above, when an IMD is discovered, the communication system can initiate a subsequent process of pairing the discovered IMD with a short unique reference address. The pairing process provided by an external device can involve, for example, taking in a serial number (e.g., a 4-byte binary value) read for any discovered IMD and assigning a shorter (e.g., 3-bit binary value) unique reference address to the IMD. Such an approach means that when a message is sent to one of a number of in-range IMDs, the process can continue with just the shorter reference address included, without including the overhead of the longer target address based on the serial number in the message and response packets. This approach leaves more margin for a limited data throughput communication scheme used for wireless support to pass meaningful payload content across the communication link. This approach also enables improved clinical support and the replacement of the IMD, which is essential at the end of the service, and effectively provides a communication-based means for switching therapy output from one IMD to another. The system and method of the present invention enable wireless communication focused on data exchange, programming, and others by each IMD discovered within the range of an external device. Here, the communication is not (necessarily) restricted to a specific time or location and may be provided at any time. Further, the communication is adapted to the specific energy requirements of small deep implant wireless IMDs. The method and IMD of the present invention further eliminate the need to separate individual IMDs from each other during manufacture as part of the need for factory shipment program setting installation, debugging, calibration, and other data relay needs.

[0030] According to the present invention, both external devices and IMDs, which are components of a communication system and have the features described above, solve the above problems in the same way.

[0031] Similarly, the above problem is solved by a communication method for wireless message transfer between an implantable medical device (IMD) and an external device, wherein the IMD monitors the patient's health status and / or delivers therapeutic signals to the patient, and the IMD comprises a processor, a memory module, and a transceiver module for bidirectional message exchange with the external device, and the method is as follows: - A step of sending a predefined wake-up signal, combined with an ID request message following a wake-up signal, to the IMD transceiver module by an external device within a predefined first time interval, wherein the ID request message contains one of the ID request commands from a predefined set. - A step in which the IMD processor generates an ID response message for a previously received ID request message in order to send an ID response message from the transceiver module to an external device within a time slot after the reception of the ID request message, wherein the ID response message includes ID information read from a predefined memory address of the memory module, the section of memory is determined by the processor based on the previously received ID request message, and the time slot is determined by the processor based on the ID information read from the determined section of memory. Includes.

[0032] Alternatively, or additionally, the ID response message may include ID information read from a memory cell section at a predefined memory address of the memory module, the memory section being determined by the processor based on the ID request command sent by the previously received ID request message, and the time slot being determined by the processor based on the ID information read from the determined memory section.

[0033] An ID request command may also be called a request specification. A memory cell may also be called memory (without the cell name).

[0034] The method of the present invention provides a means for retrieving minimal IMD status information (i.e., ID information) from any range (i.e., discovered) of leadless IMDs to assist in user selection of a specific target IMD for further inquiries / tests, etc.

[0035] In one embodiment of this method, one of eight ID request commands from a set is selected by an external device either randomly or through a rule-based methodology, and each ID request command allows the IMD processor to select a different section of memory.

[0036] Alternatively, or as an addition, one of a number of ID request commands may be selected by an external device, either randomly or according to a rule-based scheme, and each ID request command may allow the IMD processor to select a different section of memory.

[0037] Furthermore, in one embodiment, one of eight different time slots for sending an ID response message is selected by the processor based on ID information read from a determined section of memory.

[0038] Alternatively, or as an addition, one of several different time slots for sending an ID response message—for example, one of eight different time slots—is selected by the processor based on ID information read from a determined section of memory.

[0039] Furthermore, in one embodiment, a plurality of predefined wake-up signals, each combined with an ID request message following a wake-up signal within a predefined first time interval, are sent to the IMD's transceiver module by an external device, and a second such predefined wake-up signal follows the first such predefined wake-up signal within a predefined second time interval, the second time interval being longer than the first time interval.

[0040] The above methods are implemented, for example, as computer programs (to be executed in or within external devices and / or IMDs, particularly using their processors), where a computer program is a combination of (computer) instructions and data definitions specified above and below, enabling computer hardware or communication systems to perform computational or control functions and / or calculations, or a syntactic unit consisting of declarations and statements or instructions required for the functions, tasks, or problem-solving specified above and below, in accordance with the rules of a particular programming language.

[0041] Furthermore, a computer program product is disclosed that, when executed by a processor, includes instructions causing the processor to perform the steps of the method defined above. Accordingly, a computer-readable data carrier for storing such a computer program product is described.

[0042] The present invention will now be described in more detail with reference to the accompanying schematic diagrams. [Brief explanation of the drawing]

[0043] [Figure 1] This figure shows one embodiment of the communication system of the present invention, including an implantable leadless pacemaker (ILP) and external equipment, with the ILP shown in a cross-section of a patient's heart. [Figure 2] This figure shows one representation of a wake-up signal provided by an external device shown in Figure 1. [Figure 3] This diagram shows an overview of the communication method between the external device shown in Figure 1 and the ILP, as presented on the timeline. [Figure 4] This figure shows a detailed arrangement of one embodiment of time slots for a wake-up signal, an ID request message, and an ID response message, presented on a timeline. [Figure 5] Figure 1 shows an example of a graphical user interface for a computer connected to an external device for pairing ILPs within the discovered range. [Modes for carrying out the invention]

[0044] Figure 1 shows an exemplary communication system 10 and the heart 20 of a patient 30 (including the right ventricle 21 and right atrium 22). The system 10 includes a leadless ventricular pacemaker device 40 (hereinafter "ILP40") as an example of an IMD and an external device 60. The ILP40 may be configured to be implanted in the right ventricle 21 of the heart 20 (as shown in Figure 1) and to pace this ventricle, sense intrinsic ventricular depolarization and suppress ventricular pacing in response to said depolarization. The ILP40 may further include an accelerometer sensor to measure the posture of the patient 30. A programmer (not shown) may be used to program the ILP40 using the external device 60. The external device 60 is positioned outside the body and adapted to communicate bidirectionally with the ILP40.

[0045] The ILP40 may comprise modules such as a processor, a data memory module, a signal generator unit for providing therapeutic signals (e.g., pacing signals), a measurement unit including an ECG measurement unit, a DC impedance sensor and an accelerometer sensor, a transceiver for sending and receiving messages to and from an external device 60, and a power supply, each of which is electrically connected in some way within the IMD. The power supply may include a battery (e.g., a rechargeable or non-rechargeable battery). The data memory module may include any of the memory types mentioned above. The processor of the ILP40 may employ at least the sleep state and the active state described above.

[0046] External device 60 comprises a processor 61 and a transceiver 62 for exchanging messages with ILP 40, which are electrically connected to each other. Furthermore, external device 60 can exchange data with other external devices and / or remote servers (not shown). External device 60 may also be a programmer. Bidirectional message exchange with ILP 40 is symbolized by double arrows 50. Leadless communication between external device 60 and ILP 40 may be, for example, inductive magnetic communication, conducted communication, and acoustic communication.

[0047] In the following, the operation of one embodiment of this communication system and method will be described with reference to Figures 2 to 5.

[0048] To enable practical communication with multiple ILP40s and to account for the deeper implantation depth of such ILP40s, a wake-up signal 100 is provided with a sufficient clock cycle count (compared to previous sequence designs), as well as an internal gap signature for identification. Figure 2 shows an example of such a wake-up signal 100 consisting of two 8-cycle pulse output trains 101, 103 (i.e., one initial pulse train 101 and one later pulse train 103) separated by an 8-cycle gap 102. Naturally, signals 100 with more or fewer cycles, or cycle gaps, e.g., 6, 7, 9, or 10 cycles, or cycle gaps are also possible. The signal 100 with a 24-cycle gap shown in Figure 2 helps to reduce the sensitivity required for the in-ILP receiver to recognize the wake-up signal 100. The wake-up signal 100 is repeated after a time interval T2 (e.g., T2 = 333 ms). The wake-up signal 100 has a length T1 (for example, T1 = 732 μs).

[0049] The wake-up signal described above, while detecting deep leadless implants, still retains the ability to awaken the latest products for programmer intervention. The wake-up signal above will simply be ignored or terminated regardless of the implant type when such implant types require higher signal energy.

[0050] Figures 3 and 4 contain schematic representations of the wake-up signal 100, illustrating how the wake-up signal used for leadless communication is paired with an ID request message to identify multiple leadless implants. For clarity, Figure 3 focuses on the startup of communication with only one ILP 40, the ILP 40's processor initially in the sleep state described above. After a short delay of time interval T1A (see Figure 2; e.g., T1A = 488 μs) following each wake-up signal 100, the external device 60 sends an ID request message 200 to the ILP 40, which will be described in detail below. Assuming the ILP40 has detected the initial wake-up signal 100, the ILP may evaluate the gain conditions associated with the receiver configuration for further communication support, and the ILP40 processor initiates a process to confirm that the observed signaling is indeed the wake-up signal 100 (i.e., not noise), which is the step represented by arrow 401. In the next clustering grouping of the wake-up signal (after a time interval T2 of 333 ms in the illustrated embodiment), the transceiver of the ILP40 confirms that the wake-up signal 100, including its pulse trains 101, 103 and their gap 102, is indeed a valid wake-up signal (see the step symbolized by arrow 402), and then proceeds to initiate the communication clock support and phase-locked loop (PLL) elements necessary to decode the baseline binary phase-shift keying (BPSK) communication signaling (the step represented by arrow 403). By the time the third wake-up signal 100 reaches the ILP, the ILP's processor becomes active (active state as described above, represented by arrow 404) and prepares for further communication. After a time interval T3 related to the start of the first wake-up signal (T3 = 3 × T2 = 1 s), a fourth wake-up signal may be initiated by the communication unit.

[0051] To support the initiation of baseline communication, after each wake-up signal 100, the external device 60 sends out an ID request message 200. When received by the ILP, this message requests the processor of the ILP 40 to refer to the location of the data memory module where the ILP's serial number is stored, using the request specification value contained in the ID request message 200. A small number of bit (e.g., 3 bits) memory cell sections are used to determine the specific time slots S1, S2, S3, S4, S5, S6, S7, S8 (see Figure 4) in which the ILP will subsequently send its ID response message 300 to the ID request command 200 (as shown in Figure 3, 405). Each time slot S1, S2, S3, S4, S5, S6, S7, S8 represents a specific delay for the ID request message 200, where the ILP 40 responds using its transceiver module to inform the external device 60 of its presence and to carry its serial number (or a section thereof). In Figure 3, a single ILP 40 is within range of the external device 60, and the ILP 40 responds in a dedicated time slot simply labeled as a gray box tagged with reference number 300 (for example, in time slot S5). After the discovery of a single ILP 40, individual communications with the external device 60 may start, for example, by sending the actual status to the ILP 40. The start of baseline communication can begin after the time indicated by arrow 405 in Figure 3. The table below further outlines the use of the request specification for the ID request message 200. For such messages, there are multiple request specifications or ID request commands (eight in the specific examples shown; see the first column of the table below). Each determines bits from the serial number of the range ILP stored in the data memory module of the respective ILP40. The corresponding bits for each request specification are listed in the second column of the table below.A value stored in a defined bit of the serial number of any ILP within the range of external device 60 (referred to above as ID information) encodes a specific time slot. As in this embodiment, the three bits can have ID information between 0 (binary: 000) and 8 (binary: 111), and as a result, eight different time slots can be encoded as listed in the last column of the table below. Each time slot S1 to S8 is shown in Figure 4 as a separate green box. The first time slot S1 begins with a time interval T5 after the end of the ID request message 200, where T5 may be, for example, 23.4 ms. The ID request command 200 may also have a length T4 of 23.4 ms. The gap between each time slot may have a length T7 = 488 μs. [Table 1] Each time slot S1 through S8 represents a fixed, inherent delay for the completion of the ID request message 200. The delay has a length of T5, and several lengths T6 for each time slot, and T7, where, for example, T6 = 35.5 ms. The delay for time slot S1 is T5, while the delay for time slot S2 is T5 + T6 + T7, or T5 + the length of S1 + a small gap. For time slot S3, the delay is consequently T5 + 2 × T6 + 2 × T7, etc., or T5 + the length of S1 + a small gap + the length of S2 + a small gap. Each range ILP then waits for the calculated time length corresponding to the time slot, and then reports its serial number as part of the ID response message 300. This scheme does not guarantee that all ILPs 40 within the range of external equipment 60 will respond to a given ID request message 200 in different time slots. In such cases, overlapping responses from more than one ILP in the shared time slots S1 through S8 are expected to confuse response recognition by the external device 60. It is likely that, upon encountering this type of collision, one or both ILPs may not be discovered. However, each time the external device 60 sends an ID request message 200 following the wake-up signal 100, a different request specification (from eight in the shown embodiment) is selected and sent along with the ID request message 200. The selection of the request specification may be performed randomly or according to specific rules stored in the external device 60. Using a new ID request command effectively "shuffles the deck," selecting a different section of the serial numbers of the ranged ILPs to assign to the time slots. This selection of ID request commands for encoding new time slots statistically, and ultimately, allows a large number of ILPs to reach separate, distinct time slots, facilitating ILP recognition by the external device 60.

[0052] The time-multiplexed scheme for external devices to recognize individual ILPs within a defined time slot, as mentioned above, is a process that can be described as "discovery." It is the only "frame-based" part of the communication system (i.e., the part in which a defined regularity of message output is organized in time to provide tolerance for responses within an expected interval). As can be derived from Figure 4, the scheme also allows a conventional IMD to respond by having a short delay of length T5 (e.g., 23.4 ms) between the ID request message 200 and the first time slot S1. In such a case, since the conventional IMD was not designed to account for the possibility of having more than one range IMD, the IMD would be expected to simply initiate communication and, within this setup, disable any attempts by the system to engage with a leadless IMD, and the programmer software infrastructure would likely generate an interface specific to such a known conventional product. Accordingly, the approach of the present invention can support communication with conventional IMDs. Even if the ILP could be within the communication range of an external device, if the conventional implant is also within that range, the ILP would likely be "invisible" to the external device. To ensure that communication with the ILP is possible, it is prudent to keep the conventional device outside the communication range of the external device unless necessary.

[0053] As outlined above, once an ILP is discovered, the system can begin the subsequent process of pairing the found ILP with a short address. The pairing process involves capturing the found serial number (e.g., a 4-byte binary value) for any discovered ILP and assigning a shorter but unique reference address (e.g., a 3-bit binary value) to the ILP. Such an approach means that whenever a message is sent to one of several range ILPs, the process can proceed without including the overhead of the longer target address based on the serial number in the command and response packets. This approach allows meaningful payload content to be passed throughout the communication system, leaving more leeway for communication schemes with limited data throughput used for leadless support.

[0054] If the external device 60 requests that additional information be reported for any ILP paired with a short address by the system, a status / type query may then be performed. This type of basic information may include, among other considerations, whether the device is in factory / shelf condition, what condition the device's battery is presenting, and / or reporting the ILP implantation date. In a preferred embodiment, rather than using a separate command-based interaction to poll for this status / type query information, the content relayed by the IMD as part of the response to the ID request command may carry such information, the latter embodiment provides a lower overhead means of quickly providing critical device information to the system / user. Rendering such details does not represent what is conventionally known as a complete device query routine, but rather a lighter touch of retrieving a target value from a ranged ILP. Such interaction makes it possible to generate a user interface on the graphical user interface (GUI) of the external device 60, which can help the healthcare provider select the appropriate one from several ILPs found within the range of the external device 60. An exemplary interface of this type is illustrated in Figure 5, which shows a list 501 of different ILP types within the range of external device 60 and their corresponding serial numbers (see list 502). Lists 501 and 503 contain examples of the light-touch status information types mentioned above. Following the user selection of a specific ILP via GUI interaction, the communication system can enter into a formal query process with the selected ILP (in response to user commands, for example, by interface through field 504 shown) and dedicated baseline communication.

Claims

1. A communication system (10) for wireless message transfer between an implantable medical device (IMD, 40) and an external device (60), the IMD (40) and the external device (60), The IMD (40) is configured to monitor the health status of a patient (30) and / or to deliver therapeutic signals to the patient, and the IMD (40) comprises a processor, a memory module, and a transceiver module configured to exchange messages bidirectionally with the external device (60), the external device (60) is configured to send the predefined wake-up signal (100) to the transceiver module of the IMD (40) in combination with an ID request message (200) following a wake-up signal within a predefined first time interval (T1A), the ID request message containing one of a predefined set of different predefined ID request specifications. The processor of the IMD (40) is configured to generate an ID response message (300) for an ID request message received earlier, and to send the ID response message from the transceiver module to the external device (60) within a time slot after the reception of the ID request message, wherein the ID response message includes ID information read from a section of the memory of the memory module, the section of the memory is determined by the processor based on the ID request specification sent by the previously received ID request message, and the time slots (S1, S2, S3, S4, S5, S6, S7, S8) are determined by the processor based on the ID information read from the section of the memory. Communication system (10).

2. The communication system according to claim 1, wherein the section of the memory includes the memory address of the serial number of the IMD(40).

3. The communication system according to claim 1 or 2, wherein the external device (60) is configured to randomly or according to a rule-based scheme to select one of the predefined sets of predefined different ID request specifications, and each ID request specification allows the processor of the IMD (40) to select a different section of the memory.

4. The communication system according to claim 1 or 2, wherein the processor is configured to select one of a plurality of time slots (S1, S2, S3, S4, S5, S6, S7, S8) for the transceiver module to send the ID response message (300) based on the ID information read from the section of the memory.

5. The communication system according to claim 1 or 2, wherein the external device (60) is configured to send a plurality of predefined wake-up signals (100), each combined with an ID request message (200) following the wake-up signal, to the transceiver module of the IMD (40) within the predefined first time interval (T1A), the second of the predefined wake-up signals within the predefined second time interval (T2) follows the first of the predefined wake-up signals, and the second time interval is longer than the first time interval.

6. The communication system according to claim 1 or 2, wherein the wake-up signal (100) comprises a pulse output train that can be segmented into an initial segment (101) and a later segment (103) separated by an intervening gap (102), and the pulse amplitude of the initial segment of the pulse output train is the same as or different when compared with the pulse amplitude of the later segment of the pulse output train.

7. The communication system according to claim 1 or 2, wherein the external device (60) is configured to assign a unique reference address to each IMD (40) found within the range of the external device (60).

8. External equipment (60) for the communication system (10) as described in claim 1 or 2.

9. IMD (40) of the communication system (10) according to claim 1 or 2.

10. A communication method for wireless message transfer between an implantable medical device (IMD, 40) and an external device (60), wherein the IMD (40) monitors the health status of a patient (30) and / or delivers therapeutic signals to the patient, and the IMD (40) comprises a processor, a memory module, and a transceiver module for bidirectional message exchange with the external device (60), and the method is The steps include sending a predefined wake-up signal (100) combined with an ID request message (200) following a wake-up signal to the transceiver module of the IMD (40) by the external device (60) within a predefined first time interval (T1A), wherein the ID request message contains one of a predefined set of different predefined ID request specifications; A step of generating an ID response message (300) for an ID request message received earlier by the processor of the IMD (40) in order to send an ID response message from the transceiver module to the external device (60) within a time slot after the reception of the ID request message, wherein the ID response message includes ID information read from a section of the memory of the memory module, the section of the memory is determined by the processor based on the ID request specification sent by the previously received ID request message, and the time slots (S1, S2, S3, S4, S5, S6, S7, S8) are determined by the processor based on the ID information read from the section of the memory. A communication method that includes this.

11. The communication method according to claim 10, wherein the external device (60) randomly or according to a rule-based scheme, one of the predefined sets of different predefined ID request specifications is selected, and each ID request specification allows the processor of the IMD (40) to select a different section of the memory.

12. The communication method according to any one of claims 10 to 11, wherein the processor selects one of a number of different time slots (S1, S2, S3, S4, S5, S6, S7, S8) for sending the ID response message (300) based on the ID information read from the section of the memory.

13. The communication method according to any one of claims 10 to 11, wherein the external device (60) sends a plurality of predefined wake-up signals (100), each combined with an ID request message (200) following the wake-up signal, within a predefined first time interval (T1A), to the transceiver module of the IMD (40), and within a predefined second time interval (T2), the second signal of the predefined wake-up signals follows the first signal of the predefined wake-up signals, and the second time interval is longer than the first time interval.

14. A computer program product that, when executed by a processor, includes instructions causing the processor to perform a step of the method according to any one of claims 10 to 11.

15. A computer-readable data carrier for storing the computer program product described in claim 14.

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