Devices, systems, and methods for improving conducted communication between devices

Abstract

Embodiments disclosed herein may be used to enable and / or improve conductive communication between an external device and one or more implantable medical devices (IMDs) in a time, cost, and / or energy efficient manner. Certain embodiments relate to specifying an appropriate edge detection threshold for use in performing conducted communications. Certain embodiments relate to using an edge detection threshold to generate edge detection and to decode a received conducted communication signal. Other embodiments relate to a hierarchical search of an advertisement sequence sent by an IMD by an external device to enable the external device to detect the presence of the IMD and establish an active conducted telemetry session with the IMD. Yet other embodiments relate to a first segment, a second segment, and a third segment of a frame, including a corresponding first CRC code, a second CRC code, and a third CRC code. Additional embodiments of the present technology are also disclosed herein.

Description

[0001] Related Applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 626,698, filed on January 30, 2024, and U.S. Non - Provisional Patent Application No. 19 / 005,402, filed on December 30, 2024, each of which is incorporated herein by reference in its entirety as if set forth herein in full. Technical Field

[0003] The embodiments described herein generally relate to devices, systems, and methods that enable an external device (such as an external programmer or a remote monitor) to perform conductive communication with one or more implantable medical devices (such as one or more leadless pacemakers) implanted in a patient using external electrodes in contact with the patient. Certain embodiments may also be used to enable communication between multiple implantable medical devices. Background Art

[0004] Non - implant devices need to communicate with implantable medical devices (IMDs), such as leadless pacemakers (LPs), from time to time so that the non - implant device can, for example, program the IMD, interrogate the IMD, and / or obtain notifications and / or other types of diagnostic information from the IMD. Such non - implant devices (which may also be referred to as external devices or external medical devices (EMDs)) can be, for example, external programmers or remote monitors, but are not limited thereto.

[0005] Communication between an external device and one or more IMDs (e.g., one or more LPs) can be facilitated through conductive communication via a patient's tissue, whereby two or more skin electrodes (which are part of or communicatively coupled to the external device) are attached to or otherwise placed in contact with the skin of a patient in whom one or more IMDs are implanted, and the two or more skin electrodes are used to send information to and / or receive information from the IMD via conduction through the patient's body tissue. In other words, the two or more skin electrodes can be used by the external device to send conductive communication signals to and receive conductive communication signals from one or more individual IMDs. The conductive communication signals transmitted to the IMD (or vice versa) to effect conductive communication may be referred to herein as conductive communication signals. Skin electrodes are examples of external electrodes (i.e., non-implanted electrodes). In some embodiments, the skin electrodes are dry electrodes, which are electrodes that do not utilize an electrolyte gel at the interface between the electrode and the patient's skin. Conductive communication may equivalently be referred to as conducted communication or tissue conductance communication (TCC).

[0006] One potential problem with using conductive communication signals to perform communication between an external device and one or more IMDs is that the orientation of the IMDs may cause fading, which can adversely affect the quality of conductive communication. Additionally, the position of the skin electrodes (which partially defines the communication vector for the external device) may affect the quality of conductive communication between the external device and one or more IMDs. Further, noise that may vary over time may adversely affect the quality of conductive communication. These problems may be exacerbated when communication between the external device and multiple (i.e., two or more) IMDs (such as multiple LPs) is desired or required. Summary of the Invention

[0007] According to certain embodiments, a medical device includes a sensing circuitry, a controller, and a comparator circuitry. The sensing circuitry is configured to generate a sensing signal using a sensing vector that includes at least two electrodes configured to contact the patient. The controller is configured to determine a noise baseline of the sensing signal, the sensing signal being sensed using the sensing vector that includes at least two electrodes configured to contact the patient. The controller is further configured to determine an edge detection threshold based on the noise baseline such that the edge detection threshold is higher than the noise baseline. The comparator circuitry is configured to generate an edge detection by comparing an additional sensing signal or an additional portion of the sensing signal with the edge detection threshold such that a corresponding one of the edge detections in the edge detection is generated when an amplitude of the additional sensing signal or the additional portion of the sensing signal transitions from being lower than the edge detection threshold to being higher than the edge detection threshold, the additional sensing signal or the additional portion of the sensing signal being sensed using the sensing vector that includes at least two electrodes in contact with the patient. According to certain embodiments, the controller is further configured to decode a message encoded in the additional sensing signal or the additional portion of the sensing signal based on the edge detection.

[0008] According to certain embodiments, the sensing circuitry is configured to amplify and filter the sensing signal before the controller measures the noise baseline of the sensing signal, and the controller is configured to determine the noise baseline of the sensing signal by: obtaining a plurality of amplitude values of the sensing signal after the sensing signal has been amplified and filtered, and determining the noise baseline based on the plurality of amplitude values.

[0009] According to certain embodiments, the controller is configured to determine the noise baseline based on the plurality of amplitude values by determining that the noise baseline is equal to or based on an average of the plurality of amplitude values. Alternatively, the controller is configured to determine the noise baseline based on the plurality of amplitude values by determining that the noise baseline is equal to or based on a peak of the plurality of amplitude values. According to certain embodiments, the controller is configured to cause the amplitude values on which the noise baseline is determined to be generated during one or more time periods when the sensing signal includes neither an advertisement sequence nor a frame. According to certain embodiments, the controller is configured to determine the noise baseline when the medical device and another medical device are participating in an active conductive telemetry session with each other by: causing the amplitude values on which the noise baseline is determined to be generated during one or more time periods when no frame is being conductively communicated between the medical device and the other medical device.

[0010] According to some embodiments, the controller is configured to use the same equation to determine an edge detection threshold based on a noise baseline, regardless of the value of the noise baseline. Alternatively, the controller is configured to use a first equation to determine an edge detection threshold based on the noise baseline when the noise baseline is within a first value range, and to use a second equation to determine an edge detection threshold based on the noise baseline when the noise baseline is within a second value range.

[0011] Some embodiments of the present technology relate to a method used by a medical device that communicates with another medical device using conductive communication, wherein at least one of the medical device or the other medical device is implanted in a patient. According to some embodiments, such a method includes the medical device determining a noise baseline of a sensed signal, the sensed signal being sensed using a sensing vector that includes at least two electrodes in contact with the patient. The method further includes determining an edge detection threshold based on the noise baseline such that the edge detection threshold is higher than the noise baseline. The method further includes: generating an edge detection by comparing an additional sensed signal or an additional portion of the sensed signal with the edge detection threshold, such that a corresponding one of the edge detections in the edge detection is generated when the amplitude of the additional sensed signal or the additional portion of the sensed signal transitions from being below the edge detection threshold to being above the edge detection threshold, the additional sensed signal or the additional portion of the sensed signal being sensed using a sensing vector that includes at least two electrodes in contact with the patient. According to some embodiments, the method further includes the medical device decoding a message encoded in the additional sensed signal or in the additional portion of the sensed signal based on the edge detection. According to some embodiments, the medical device is outside the patient, the other medical device is implanted in the patient, and the at least two electrodes in contact with the patient include dry electrodes in contact with the patient's skin.

[0012] According to some embodiments, prior to determining the noise baseline of the sensed signal, the sensed signal is amplified and filtered, and determining the noise baseline of the sensed signal includes: after the sensed signal has been amplified and filtered, generating a plurality of amplitude values of the sensed signal, and determining the noise baseline based on the plurality of amplitude values. In some such embodiments, determining the noise baseline based on the plurality of amplitude values includes: determining that the noise baseline is equal to or based on the average of the plurality of amplitude values. Alternatively, determining the noise baseline based on the plurality of amplitude values includes: determining that the noise baseline is equal to or based on the peak of the plurality of amplitude values. In some embodiments, the amplitude values based on which the noise baseline is determined are generated during one or more time periods when the sensed signal includes neither a notification sequence nor a frame. In some embodiments, the determination of the noise baseline is performed while the medical device and another medical device (e.g., an external medical device (EMD) and an implantable medical device (IMD)) are participating in an active conductive telemetry session with each other, and the amplitude values based on which the noise baseline is determined are generated during one or more time periods when no frame is being conductively communicated between the medical device and the other medical device.

[0013] According to certain embodiments, determining an edge detection threshold based on a noise baseline includes using the same equation to determine the edge detection threshold based on the noise baseline regardless of the value of the noise baseline. Alternatively, determining the edge detection threshold based on the noise baseline includes: when the noise baseline is within a first value range, using a first equation to determine the edge detection threshold based on the noise baseline, and when the noise baseline is within a second value range, using a second equation to determine the edge detection threshold based on the noise baseline.

[0014] Certain embodiments of the present technology relate to a method used by an external device that includes or is communicatively coupled to two or more external electrodes that contact the skin of a patient in which an implantable medical device (IMD) is implanted. The method includes the external device searching for a known message preamble in a first time window in a sensed signal, the sensed signal being sensed using a sensing vector that includes at least two of the two or more electrodes that contact the patient. The method further includes: in response to not detecting the known message preamble in the first time window, restarting the search for the known message preamble in the sensed signal one or more times until the known message preamble is detected, wherein each time the search for the known message preamble in the sensed signal is restarted, a different instance of the first time window is searched. The method further includes in response to detecting the known message preamble, searching for additional known message portions in a second time window after the first time window in which the preamble was detected. In response to not detecting the additional known message portions in the second time window of the sensed signal after the first time window in which the preamble was detected, the method includes restarting the search for the known message preamble in the sensed signal. The method further includes: in response to detecting the known message preamble and detecting the additional known message portions in consecutive instances of the first time window and the second time window, respectively, sending a command to the IMD. According to certain embodiments, the command sent from the external device to the IMD in response to detecting the known message preamble includes one of the following types of commands: an open link command, a keep link active command, a read type command, a write type command, or a close link command. According to certain embodiments, the IMD includes a leadless pacemaker. According to certain embodiments, the external device and the IMD are configured to communicate with each other using conductive communication.

[0015] According to certain embodiments, the known message preamble is a known byte. According to certain embodiments, the additional known message portions searched for in the second time window of the sensed signal include any one of a plurality of known IMD addresses.

[0016] According to certain embodiments, searching for a known message preamble in a first time window in a sensed signal includes: searching for a known first portion of the known message preamble in a first portion of the first time window. Responsive to not detecting the known first portion of the known message preamble in the first portion of the first time window, restarting the search for the known first portion of the known message preamble in the first portion of the first time window, wherein each time the search for the known first portion of the message preamble is restarted, a different instance of the first portion of the first time window is searched. Responsive to detecting the known first portion of the known message preamble, searching for a known second portion of the known message preamble in a second portion of the first time window. Responsive to not detecting the known second portion of the known message preamble in the second portion of the first time window, restarting the search for the known first portion of the known message preamble in the first portion of the first time window. Responsive to detecting the known first and second portions of the known message preamble in successive instances of the first and second portions of the first time window, the known message preamble is detected. According to certain embodiments, the known message preamble is a known byte, and the known first portion of the message preamble is a known first nibble of the known byte, and the known second portion of the message preamble is a known second nibble of the known byte. According to certain embodiments, searching for additional known message portions in a second time window of the sensed signal includes any one of a plurality of known IMD addresses.

[0017] According to certain embodiments, the known message preamble and the additional known message portions are part of an announcement sequence that is periodically transmitted by the IMD using conductive communication when the external device and the IMD are not in an active conductive telemetry session. Alternatively, the known message preamble and the additional known message portions are part of the header of a frame transmitted by the IMD during an active conductive telemetry session between the external device and the IMD.

[0018] Certain embodiments of the present technology relate to an external device configured to communicate with an IMD implanted in a patient, where the external device includes two or more external electrodes configured to be placed in contact with the skin of the patient in whom the IMD is implanted, a conductive communication receiver communicatively coupled (directly or through a switch) to the two or more external electrodes, a conductive communication transmitter communicatively coupled (directly or through a switch) to the two or more external electrodes, and a controller communicatively coupled to the conductive communication receiver and the conductive communication transmitter. The controller is configured to use the conductive communication receiver to sense a signal using a sensing vector, and search the sensed signal for a known message preamble within a first time window, the sensing vector including at least two of the two or more external electrodes that are in contact with the skin of the patient in whom the IMD is implanted. Responsive to not detecting the known message preamble within the first time window, the controller is configured to restart the search for the known message preamble one or more times on the sensed signal until the known message preamble is detected, where each time the search for the known message preamble on the sensed signal is restarted, a different instance of the first time window is searched. Responsive to detecting the known message preamble, the controller is configured to search the sensed signal for additional known message portions within a second time window that follows the first time window in which the known preamble was detected. Responsive to not detecting the additional known message portions within the second time window of the sensed signal after the first time window in which the preamble was detected, the controller is configured to restart the search for the known message preamble. The controller is also configured to use the conductive communication transmitter to send a command to the IMD in response to detecting the known message preamble and detecting the additional known message portions within consecutive instances of the first time window and the second time window, respectively.

[0019] According to certain embodiments, the known message preamble is a known byte. According to certain embodiments, the additional known message portions searched for within the second time window of the sensed signal include any one of a plurality of known IMD addresses.

[0020] According to certain embodiments, to search for a known message preamble in a first time window in a sensed signal, the controller is configured to search for a known first portion of the known message preamble in a first portion of the first time window using a conductive communication receiver. In response to not detecting the known first portion of the known message preamble in the first portion of the first time window, the controller is configured to restart searching for the known first portion of the known message preamble in the first portion of the first time window, wherein each time the search for the known first portion of the known message preamble is restarted, a different instance of the first portion of the first time window is searched. In response to detecting the known first portion of the known message preamble, the controller is configured to search for a known second portion of the known message preamble in a second portion of the first time window. In response to not detecting the known second portion of the known message preamble in the second portion of the first time window, the controller is configured to restart searching for the known first portion of the known message preamble in the first portion of the first time window. Additionally, the controller is configured to detect the known message preamble in response to detecting the known first portion and the known second portion of the known message preamble in consecutive instances of the first portion and the second portion of the first time window, respectively.

[0021] Certain embodiments of the present technology relate to a method for using frames to provide communication between an external medical device (EMD) and an implantable medical device (IMD), where the frame includes a header and a body. The method includes: the EMD includes a command generated by the EMD and a first cyclic redundancy check (CRC) code within a first segment of the body of the frame, and the EMD transmits the first segment of the body of the frame. The method further includes: the IMD includes cardiac event data generated by the IMD and a second CRC code within a second segment of the body of the frame, and the IMD transmits the second segment of the body of the frame. The method further includes: one of the EMD and the IMD includes payload data generated by one of the EMD and the IMD and a third CRC code within a third segment of the body of the frame, and one of the EMD and the IMD transmits the payload data and the third CRC code. Additionally, the method includes the IMD receiving the first segment of the body of the frame and determining whether there is an error in the first segment of the body of the frame based on the first CRC code, and the IMD accepting the command included in the first segment in response to determining that the first segment does not include an error, or rejecting the command included in the first segment in response to determining that the first segment includes an error. The method further includes: the EMD receiving the second segment of the body of the frame, and the EMD determining whether there is an error in the second segment of the frame body according to the second CRC code, and the EMD accepting the cardiac event data included in the second segment in response to determining that the second segment does not include an error, or rejecting the cardiac event data included in the second segment in response to determining that the second segment includes an error. The method further includes the other of the IMD or the EMD (which does not include the third CRC code in the third segment) receiving the third segment of the body of the frame and determining whether there is an error in the third segment of the body of the frame based on the third CRC code, and accepting the payload data included in the third segment in response to determining that the third segment does not include an error, or rejecting the payload data included in the third segment in response to determining that the third segment includes an error.

[0022] According to certain embodiments, the header is generated by the IMD and includes a preamble and a device address.

[0023] According to certain embodiments, when the command included in the frame is a write-type command, the frame further includes one of an acknowledgement (ACK) or a negative acknowledgement (NACK), which respectively specify whether the payload data being written to the memory of the IMD is valid, as determined based on the third CRC code.

[0024] According to certain embodiments, in response to the IMD determining that there are no errors in the first paragraph, the IMD accepts and executes the command regardless of whether there are errors in at least one of the second or third paragraphs of the body of the frame. Additionally, in response to the EMD determining that there are no errors in the second paragraph, the EMD accepts the cardiac event data regardless of whether there are errors in at least one of the first or third paragraphs. In certain embodiments, in response to determining that there are no errors in the third paragraph, one of the IMD or EMD that did not generate the third CRC code accepts the payload data regardless of whether there are errors in at least one of the first or second paragraphs of the body of the frame.

[0025] According to certain embodiments, the EMD and the IMD are configured to communicate with each other using conductive communication.

[0026] Certain embodiments of the present technology relate to a system including an EMD and an IMD, the EMD and the IMD being configured to communicate with each other using frames. Each of the EMD and the IMD includes a respective transmitter, a receiver, and a controller that controls the transmitter and the receiver. The controller of the EMD is configured to include a command generated by the EMD and a first CRC code within a first paragraph of the body of the frame, and is configured to control the transmitter of the EMD to transmit the first paragraph of the body of the frame. The controller of the IMD is configured to include heart event data generated by the IMD and a second CRC code within a second paragraph of the body of the frame, and is configured to control the transmitter of the IMD to transmit the second paragraph of the body of the frame. Additionally, the controller of one of the EMD and the IMD is configured to include payload data generated by one of the EMD and the IMD and a third CRC code within a third paragraph of the body of the frame, and is configured to control the transmitter of one of the EMD and the IMD to transmit the third paragraph of the body of the frame. The controller of the IMD is further configured to control the receiver of the IMD to receive the first paragraph of the body of the frame, and is configured to determine whether an error exists in the first paragraph of the body of the frame based on the first CRC code, and is configured to accept the command included in the first paragraph in response to determining that the first paragraph does not include an error, or to reject the command included in the first paragraph in response to determining that the first paragraph includes an error. The controller of the EMD is further configured to control the receiver of the EMD to receive the second paragraph of the body of the frame, and to determine whether an error exists in the second paragraph of the body of the frame based on the second CRC code, and is configured to accept the heart event data included in the second paragraph in response to determining that the second paragraph does not include an error, or to reject the heart event data included in the second paragraph in response to determining that the second paragraph includes an error. The controller of the other of the IMD or the EMD is configured to control the receiver of the other of the IMD or the EMD to receive the third paragraph of the body of the frame, and to determine whether an error exists in the third paragraph of the body of the frame based on the third CRC code, and to accept the payload data included in the third paragraph in response to determining that the third paragraph does not include an error, or to reject the payload data included in the third paragraph in response to determining that the third paragraph includes an error.

[0027] According to certain embodiments, the controller of the IMD is configured to generate a header that includes a preamble and a device address. According to certain embodiments, the controller of the IMD is further configured to include one of an acknowledgement (ACK) or a negative acknowledgement (NACK) that respectively specify whether the payload data being written to the memory of the IMD is valid as determined based on the third CRC code.

[0028] According to certain embodiments, the controller of the IMD is configured to accept and execute a command in response to determining that there is no error in the first paragraph, regardless of whether there is an error in at least one of the second or third paragraphs of the body of the frame. Additionally, the controller of the EMD is configured to accept cardiac event data in response to determining that there is no error in the second paragraph, regardless of whether there is an error in at least one of the first or third paragraphs. According to certain embodiments, the controller of one of the IMD or EMD that does not include a third CRC code in the third paragraph is configured to accept payload data in response to determining that there is no error in the third paragraph of the body of the frame, regardless of whether there is an error in at least one of the first or second paragraphs of the body of the frame.

[0029] According to certain embodiments, the EMD and the IMD are configured to communicate with each other using conductive communication, the respective receivers of each of the EMD and the IMD include respective conductive communication receivers, and the respective transmitters of each of the EMD and the IMD include respective conductive communication transmitters.

[0030] This summary is not intended to be a complete description of the embodiments of the technology. Combining the drawings and the claims, other features and advantages of the embodiments of the technology will become apparent from the following description in which the preferred embodiments have been elaborated in detail. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Embodiments of the technology related to the structure and method of operation can be better understood by reference to the following description and the drawings, in which like reference numerals represent like elements in several views:

[0032] Figure 1 A system is shown that includes a plurality of IMDs implanted in a patient and an external device that can be used to program the IMDs and / or otherwise communicate with the IMDs.

[0033] Figure 2 is a high-level block diagram of an example LP.

[0034] Figure 3 An example form factor of the LP is shown.

[0035] Figure 4 An example configuration involving an external device and two endocardial LPs is depicted.

[0036] Figure 5 A sample configuration involving an external device and two epicardial (on the external surface of the heart) LPs is depicted.

[0037] Figure 6 An example of an external device communicatively coupled to three electrodes in contact with the patient's chest is depicted.

[0038] Figure 7is a high - level block diagram showing example details of an external device configured to communicate with one or more IMDs implanted in a patient using conductive communication, where the external device includes or is communicatively coupled to at least three external electrodes that contact the patient.

[0039] Figure 8A Shows an example format of an announcement sequence sent by the IMD that enables the external device to detect the presence of the IMD and establish an active conductive telemetry session with the IMD.

[0040] Figure 8B Shows an example format of a frame according to an embodiment of the present technology, which is used to support conductive communication between the external device and the IMD during an active conductive telemetry session between the external device and the IMD.

[0041] Figure 8C is for outlining a method of providing communication between an external device and an IMD using frames (such as Figure 8B the frames introduced in

[0042] Figure 9A Shows an example conductive communication signature for representing a "1" bit value and a "0" bit value in different time windows.

[0043] Figure 9B Shows a conductive communication signal after the conductive communication signal has been sent by the IMD through patient tissue, received by the external device, and amplified and filtered by the external device, including Figure 9A an instance of the signature represented in

[0044] Figure 9C Shows an interrupt blanking period triggered in response to an initial edge detection within a time window, where the initial edge detection is used to determine whether the time window includes a bit value of "1" or a bit value of "0" according to certain embodiments of the present technology.

[0045] Figure 10 is a high - level block diagram according to an embodiment of the present technology for describing how an edge detection threshold can be determined by an external device for performing conductive communication with an IMD.

[0046] Figure 11A is a high - level flowchart for outlining a method for determining an edge detection threshold used during conductive communication according to certain embodiments of the present technology.

[0047] Figure 11B is a high - level flowchart for outlining a method for using an edge detection threshold to generate edge detection and decode a received conductive communication signal according to certain embodiments of the present technology.

[0048] Figure 12A is a high - level flowchart for outlining a method for performing a hierarchical search on an announcement sequence sent by an IMD, such that an external device can detect the presence of the IMD and establish an active conductive telemetry session with the IMD, according to an embodiment of the present technology.

[0049] Figure 12B is a high - level flowchart for outlining a method for performing a hierarchical search on an announcement sequence sent by an IMD, such that an external device can detect the presence of the IMD and establish an active conductive telemetry session with the IMD, according to another embodiment of the present technology.

[0050] Figure 13A and Figure 13B and Figure 13C and Figure 13D show a front view, a rear view, a right - hand side view, and a left - hand side view of the form factor of an external device, respectively, according to an embodiment of the present technology.

[0051] Figure 14 is a high - level flowchart for outlining how various embodiments of the present technology can optionally be used in combination with each other. Detailed Description

[0052] Embodiments of the present technology can be used to implement and / or improve conductive communication between an external device and one or more implantable medical devices (IMDs) in a time, cost, and / or energy - efficient manner. For example, certain embodiments of the present technology relate to specifying an appropriate edge - detection threshold to be used when performing conductive communication. Certain embodiments relate to using the edge - detection threshold to generate edge detection and decode the received conductive communication signal. Other embodiments of the present technology relate to a hierarchical search by an external device for an announcement sequence sent by an IMD, such that the external device can detect the presence of the IMD and establish an active conductive telemetry session with the IMD. Other embodiments relate to using at least three different cyclic redundancy check (CRC) codes within the same frame, which enables one or more segments of a frame that do not include errors (as determined based on their respective CRCs) to be accepted, while one or more other segments of a frame that include errors (as determined based on their respective CRCs) are rejected. Each of the foregoing embodiments can be used alone or in combination with one or more other embodiments. Another embodiment of the present technology is also disclosed herein. However, before providing additional details of specific embodiments of the present technology, an example environment in which embodiments of the present technology can be useful will first be referred to Figures 1 to 3 and described.

[0053] More specifically, Figures 1 to 3This will be used to describe an example cardiac pacing system in which pacing and sensing operations can be performed by multiple IMDs. Such a system can include one or more leadless pacemakers (LPs), implantable cardioverter defibrillators (ICDs) (such as non-vascular ICDs (NV-ICDs)), insertable cardiac monitors (ICMs), and / or external devices. In cases where the system includes an ICD, the system is also capable of performing defibrillation. In cases where the only IMD is an ICM, the system may only be capable of performing monitoring without performing any treatment. External devices can also be referred to herein as external medical devices (EMDs).

[0054] Figure 1 Shown is a system 100 configured to be at least partially implanted in the heart 101. The system 100 includes LPs 102a and 102b located in different chambers of the heart 101. LP 102a is located in the right atrium, while LP 102b is located in the right ventricle. LPs 102a and 102b can communicate with each other to notify each other of various local physiological activities, such as local intrinsic events, local pacing events, etc. LPs 102a and 102b can be constructed in a similar manner but operate differently based on which chamber LP 102a or 102b is located in. LPs 102a and 102b can sometimes be collectively referred to herein as LP 102, or individually as LP 102.

[0055] In certain embodiments, LPs 102a and 102b communicate with each other, and / or with ICM 104, and / or with ICD 106 via conductive communication through the same electrodes used for sensing and / or delivering pacing therapy. LPs 102a and 102b also use conductive communication to communicate with a non-implant device 109 that has at least two electrodes 115a and 115b placed on or against the patient's skin, with LPs 102a and 102b implanted within the patient's skin. The non-implant device 109 (which can also be referred to as external device 109 or external medical device (EMD) 109) can be an external programmer capable of programming LPs 102, ICM 104, and / or ICD 106. The external device 109 can alternatively be an external monitor, such as a bedside monitor or a patient link monitor (PLM), that is not capable of programming LPs 102, ICM 104, and / or ICD 106.

[0056] Although not shown (and not preferred as it would increase the size and power consumption of LPs 102a and 102b), LPs 102a and 102b can potentially include an antenna and / or a telemetry coil that would enable them to communicate with each other, with ICD 106, and / or with the non-implant device using RF and / or inductive communication. AlthoughFigure 1 Only two LPs 102 are shown, but more than two LPs can be implanted in a patient. For example, to provide biventricular pacing and / or cardiac resynchronization therapy (CRT), in addition to implanting LPs in the right atrium (RA) chamber and the right ventricle (RV) chamber or on the right atrium chamber and the right ventricle chamber, additional LPs can be implanted in or on the left ventricle chamber. A single LP can also be implanted in a patient, such as in the RV chamber, the RA chamber, or the LV chamber, or on the RV chamber, the RA chamber, or the LV chamber, but not limited thereto. More than one LP can also be implanted in or on the same heart chamber.

[0057] In some embodiments, one or more of the LPs 102a, 102b can be co-implanted with the ICM 104 and / or the ICD 106. In such embodiments, the ICM 104 and / or the ICD 106 are examples of other types of IMDs that may need to communicate with an external device (such as an external programmer) from time to time. The ICM 104 and / or the ICD 106 can communicate with the LP 102 and with the external device using conductive communication. Alternatively or additionally, the ICM 104 and / or the ICD 106 can communicate with the external device using radio frequency (RF) communication and / or inductive communication, depending on the specific implementation and the capabilities of the external device.

[0058] Each LP 102 uses two or more electrodes located within, on, or within a few centimeters of the housing of the pacemaker for pacing and sensing at the heart chamber and for two-way conductive communication with the external device 109, the ICD 106, and / or the ICM 104. Such an ICM 104 can be intended for subcutaneous implantation at a site near the heart 101. The ICM 104 can include, for example, a pair of spaced-apart sensing electrodes positioned relative to the housing, where the sensing electrodes provide detection of far-field EGM signals and can also be used for conductive communication with one or more other implanted devices (such as the LPs 102a and / or 102b and / or the ICD 106), and / or can be used for conductive communication with the external device 109. Such an ICM can also include an antenna configured to wirelessly communicate with the external device using one or more wireless communication protocols (e.g., Bluetooth, Bluetooth Low Energy, Wi-Fi, etc.). The housing of the ICM 104 can include various other components, such as: sensing electronics for receiving signals from the electrodes, a microprocessor for processing the signals according to an algorithm, a cyclic memory for temporarily storing cardiac activity (CA) data, a device memory for long-term storage of CA data in certain trigger events, a sensor for detecting patient activity, and a battery for powering the components.

[0059] Each LP 102 and / or other types of IMDs may from time to time use at least two electrodes of the IMD (e.g., the LP) to transmit an announcement sequence such that an external device having external electrodes or an external device communicatively coupled to the external electrodes in contact with a patient (where the LP and / or other IMDs are implanted within the patient) (e.g., an external programmer or a remote monitor) can detect the presence of the IMD and optionally establish an active conductive telemetry session (which may also be referred to as an active conductive communication session) with one or more IMDs. For a more specific example, the LP (or other type of IMD) may transmit an announcement sequence once every specified number of cardiac cycles (e.g., once every eight cardiac cycles), or once every specified time period (e.g., once every 5 seconds), but is not limited thereto. As will be described below with reference to Figure 8A According to certain embodiments of the present technology, each announcement sequence includes a preamble followed by a device address, where the preamble is a known bit sequence (e.g., a known byte), regardless of which IMD transmits the announcement sequence, and the device address is one of a plurality (e.g., four) of possible device addresses corresponding to the type of the IMD transmitting the announcement sequence and / or the location of the IMD. To reduce the probability that announcement sequences transmitted by different IMDs will conflict with each other (i.e., be transmitted by different IMDs at overlapping times such that it is difficult or impossible for an external device to receive them), different IMDs will transmit their respective announcement sequences at different rates or periodicities. For example, a first IMD may transmit its announcement sequence (which includes a preamble and a first device address) once every seven cardiac cycles, a second IMD may transmit its announcement sequence (which includes a preamble and a second device address) once every eight cardiac cycles, a third IMD may transmit its announcement sequence (which includes a preamble and a third device address) once every nine cardiac cycles, and so on. For another example, a first IMD may transmit its announcement sequence (which includes a preamble and a first device address) once every seven seconds, a second IMD may transmit its announcement sequence (which includes a preamble and a second device address) once every eight seconds, a third IMD may transmit its announcement sequence (which includes a preamble and a third device address) once every nine seconds, and so on.

[0060] According to certain embodiments, the announcement sequence is a predetermined sequence that indicates to an external device (e.g., an external programmer or a remote monitor) that the LP (or other type of IMD) is implanted within a patient. The announcement sequence may also be referred to as a sniff sequence, or more simply as a sniff. In other words, the terms announcement sequence, sniff sequence, and sniff are used interchangeably herein.

[0061] In some embodiments, each sniffing sequence (aka advertisement sequence) sent by the LP (or another type of IMD) is sent during the cardiac refractory period following an intrinsic or paced cardiac activation (aka depolarization). When the LP is implanted in or on a ventricular heart chamber, the refractory period associated with that LP follows an intrinsic or paced ventricular depolarization. When the LP is implanted in or on an atrial heart chamber, the refractory period associated with that LP follows an intrinsic or paced atrial depolarization. The length of the refractory period can be programmed and can be, for example, in the range of 100 milliseconds to 500 milliseconds long. The refractory period may also be rate-dependent and / or depend on one other factor that may vary over time.

[0062] In some embodiments described below, each sniffing sequence (aka advertisement sequence) sent by the LP 102 (or another type of IMD) includes a specified preamble and the address of the LP 102 (or other type of IMD).

[0063] In some embodiments, the external device 109 can use the sniffing sequence to initiate an active conduction telemetry session (aka active conduction communication session) with the LP 102 (or another type of IMD), as will be described in further detail below.

[0064] In some embodiments, the external device 109 can use the sniffing sequence to identify which one of a plurality of possible conduction communication vectors is the preferred conduction communication vector for communicating with the LP 102 (or other type of IMD) that sent the sniffing sequence. For example, where the external device 109 has three external electrodes or is communicatively coupled to three external electrodes, namely, a first external electrode, a second external electrode, and a third external electrode (e.g., Figure 6 and Figure 7 115a, 115b, 115c in Figure 6 and Figure 7 ), the external device 109 can test and select among a first subset, a second subset, and a third subset of the external electrodes, where the first subset includes the first external electrode and the second external electrode (e.g., Figure 6 and Figure 7 115a and 115b in Figure 6 and Figure 7 ), the second subset includes the first external electrode and the third external electrode (e.g., Figure 6 and Figure 7 115a and 115c in Figure 6 and Figure 7 ), and the third subset includes the second external electrode and the third external electrode (e.g., Figure 6 and Figure 7 115b and 115c in

[0065] Reference Figure 2, The block diagram shows an example embodiment of portions of the electronic devices within LP 102a, 102b, which are configured to provide conductive communication through the same electrodes for cardiac pacing and / or sensing. Each of LP 102a, 102b includes at least two leadless electrodes configured for delivering cardiac pacing pulses, sensing induced and / or natural cardiac electrical signals, and unidirectional and / or bidirectional communication. In Figure 2 (and Figure 3 ), two of the electrodes shown therein are labeled 108a and 108b. Such electrodes may be collectively referred to as electrode 108, or individually as electrode 108. LP 102 or other types of IMDs may include more than two electrodes, depending on the implementation.

[0066] In Figure 2 , each of LP 102a, 102b is shown as including a conductive communication receiver 120 coupled to electrode 108 and configured to receive conductive communication signals from another LP 102, ICM 104, and / or ICD 106, but not limited thereto. Conductive communication receiver 120 and electrode 108 may also be used to receive conductive communication signals from external device 109. Although one receiver 120 is depicted in Figure 2 , in other embodiments, each of LP 102a, 102b may also include one or more additional receivers. As will be described in further detail below, pulse generator 116 may be used as a transmitter for sending conductive communication signals using electrode 108 under the control of controller 112. In certain embodiments, LP 102a, 102b may communicate not only through first communication channel 105 and second communication channel 107. In certain embodiments, LP102a, 102b may communicate through a common communication channel 105. More specifically, LP 102a and 102b may conductively communicate on a common physical channel via the same electrode 108 that is also used for delivering pacing pulses. Using electrode 108 for conductive communication enables one or more of LP 102a, 102b to perform antenna-less and induction-coil-less communication. In the case where multiple implantable devices (such as LP 102a and 102b) communicate with each other using conductive communication, such conductive communication may be referred to as implant-to-implant (i2i) conductive communication, or more simply as i2i conductive communication.

[0067] Optionally, an LP (or other IMD) that receives any conducted communication signal from another LP (or other IMD) or from a non-implanted device (also referred to as an external device) can send a receive confirmation indicating that the receiving LP (or other IMD or external device) has received the conducted communication signal. In some embodiments, in the case where an IMD expects to receive a conducted communication signal within a window and fails to receive the conducted communication signal within the window, the IMD can send a failure to receive confirmation indicating that the receiving IMD has failed to receive the conducted communication signal. The failure to receive confirmation may also be referred to herein as a negative acknowledgement (NACK). Other variations are possible and are within the scope of the embodiments described herein. Each conducted communication signal can include one or more sequences of conducted communication pulses. According to some embodiments, the conducted communication pulses are delivered during a cardiac refractory period identified or detected by the LP and / or other IMD and / or from a non-implanted device (also referred to as an external device). According to some embodiments, the conducted communication pulses are sub-threshold, i.e., they are below the capture threshold of the patient. According to some embodiments, the conducted communication receiver 120 includes a message amplifier and / or filter 122 and an edge detection comparator 124. The message amplifier and / or filter 122 is configured to amplify and / or filter the conducted communication signal received by the LP from another LP, another type of IMD, and / or an external device (e.g., 109). The edge detection comparator 124 is configured to compare the received conducted communication signal with an edge detection threshold that can be determined according to embodiments of the present technology, as will be described below. The edge detection comparator 124 may also be referred to herein as an edge detector 124 or a comparator circuit system 124. The output of the edge detection comparator 124 can be provided to the controller 112, which can be used to implement a message decoder that decodes the conducted communication signal received from another LP, another type of IMD, and / or an external device into a format that the controller 112 can understand. The message amplifier and / or filter 122 can be implemented in the same or a similar manner as the message amplifier and / or filter 740 described below with reference to Figure 7 and Figure 10 but is not limited thereto. The edge detection comparator 124 can be implemented in the same or a similar manner as the edge detection comparator 1008 described below with reference to Figure 10 but is not limited thereto.

[0068] The LPs 102a, 102b can exchange event messages within the i2i conducted communication signal to implement synchronous therapy and additional support features (e.g., measurements, etc.). To maintain synchronous therapy, each of the LPs 102a, 102b (via event messages) is made aware of when an event occurs in the chamber containing the other LP 102a, 102b. As will be described in further detail below, with reference to Figure 5, LP 102a can be located on the outer surface of the RA chamber instead of being located within the RA chamber. Additionally or alternatively, LP 102b can be located on the outer surface of the RV chamber instead of being located within the RV chamber.

[0069] For synchronous event signaling, LP 102a and 102b can maintain synchronization and communicate periodically at a specific interval. Synchronous event signaling allows the transmitters and receivers in each of LP 102a, 102b to use limited (or minimum) power because each of LP 102a, 102b is powered only for a small fraction of the time related to transmission and reception. For example, LP 102a, 102b can send / receive (Tx / Rx) communication messages in time slots having a duration of 10 - 20 µs, where the Tx / Rx time slots occur periodically (e.g., every 10 - 20 ms). Such time slots can also be referred to as windows.

[0070] Still referring to Figure 2 , each of LP 102a, 102b is shown to include a controller 112 and a pulse generator 116. The controller 112 can include, for example, a microprocessor (or equivalent control circuitry), logic and timing circuitry, state machine circuitry, and I / O circuitry, but is not limited thereto. The controller 112 can include a random access memory (RAM) and / or a read-only memory (ROM), and / or the controller 112 can be coupled to a memory 118. More generally, the memory 118 that can include RAM and / or ROM can be within the controller 112 and / or external to the controller 112 and coupled to the controller 112. The controller 112 can also include, for example, timing control circuitry to control the timing of the stimulation pulses (e.g., pacing rate, atrioventricular (AV) delay, atrial-atrial (A-A) delay, or ventriculo-ventricular (V-V) delay, etc.). Such timing control circuitry can also be used for the timing of the following, including: refractory period, blanking interval, noise detection window, evoked response window, alert interval, marker channel timing, etc. The controller 112 can also include other dedicated circuitry and / or firmware / software components that help monitor various conditions of the patient's heart and manage the pacing therapy.

[0071] The controller 112 and the pulse generator 116 can be configured to send event messages via the electrode 108 in a manner that does not inadvertently capture the heart in the chamber where LP102a, 102b are located (such as when the associated chamber is not in a refractory state). Additionally, the received LP 102a, 102b can enter an "event refractory" state (or event blanking state) after receiving the event message. The event refractory / blanking state can be set to extend for a determined period of time after receiving the event message so as to prevent the received LP 102 from inadvertently sensing another signal as an event message that could otherwise cause re-triggering. For example, the received LP 102 can detect a measurement pulse from another LP 102 or an external device 109. Although only one pulse generator 116 is shown in Figure 2 , the LP 102 can include two pulse generators 116, where one pulse generator is for generating pacing pulses and the other pulse generator is for generating conduction communication pulses. Alternatively, the same pulse generator 116 can be used for generating both pacing pulses and conduction communication pulses.

[0072] According to certain embodiments herein, the external device 109 can communicate with the LPs 102a, 102b using the same communication scheme via an external device to LP channel. The external device 109 can listen for event messages transmitted between the LPs 102a, 102b, where the event messages are of the type of i2i message sequence, and the external device can synchronize the external device to implant communication such that the external device 109 does not send the communication signal 113 until after the i2i message sequence is complete.

[0073] In some embodiments, an individual LP 102 can include an airtight housing 110 and at least two leadless electrodes 108, the airtight housing 110 being configured to be placed on or attached to the inside or outside of a heart chamber, the at least two leadless electrodes 108 being close to the housing 110 and being configured to conduct communication with at least one other device inside or outside the body. Depending on the specific implementation and / or the other devices with which the LP communicates, the conduction communication can be unidirectional or bidirectional.

[0074] Figure 2Shows the functional elements of the LP 102 substantially enclosed within an airtight housing 110. The LP 102 has at least two electrodes 108 located within, on, or near the housing 110 for delivering pacing pulses to the muscle of a heart chamber and sensing the electrical activity from the muscle of the heart chamber, and for conducting communication with at least one other device inside or outside the body. The hermetic feedthroughs 130, 131 conduct electrode signals through the housing 110. The housing 110 contains a primary battery 114 for supplying power for pacing, sensing, and communication. The housing 110 also contains a circuit 132 for sensing heart activity from the electrodes 108, a receiver 120 for receiving information from at least one other device via the electrodes 108, a pulse generator 116 for generating pacing pulses for delivery via the electrodes 108, and for sending information to at least one other device via the electrodes 108. The housing 110 may also contain circuits for monitoring the health of the device, such as an optional battery current monitor 136 and an optional battery voltage monitor 138, and may include circuits for controlling the operation in a predetermined manner.

[0075] The electrodes 108 may be configured for two-way communication between multiple leadless cardiac pacemakers, implanted ICDs 106, and / or implanted ICMs 104 to use messages to coordinate pacing pulse delivery and optional other therapeutic or diagnostic features, to react as directed by the message depending on the message source, the message identifying events at the individual pacemaker where the message originated and at the pacemaker receiving the message. The LPs 102a, 102b receiving event messages react as directed by the event message depending on the message source or location. In some embodiments or scenarios, two or more leadless electrodes 108 may be configured for two-way communication between one or more LPs, ICDs 106, and / or ICMs 104 and send data including a specified code of an event detected or created by an individual pacemaker. The individual pacemaker may be configured to emit a unique code corresponding to the event type and the location of the transmitting pacemaker. The electrodes 108 may also be used to send conduction communication signals to and / or receive conduction communication signals from an external device 109.

[0076] Similarly, as Figure 2As shown, the primary battery 114 has a positive terminal 140 and a negative terminal 142. Current from the positive terminal 140 of the primary battery 114 flows through an optional shunt 144 to an optional regulator circuit 146 to create a positive voltage source 148 suitable for powering the remainder of the circuitry of the pacemaker 102. The shunt 144 enables the battery current monitor 136 to provide an indication of battery current consumption to the controller 112 and indirectly an indication of device health. An exemplary power source can be the primary battery 114. The LP is also shown as including a temperature sensor 152 and an accelerometer 154, but can include only one of the temperature sensor 152 and the accelerometer 154, but not the other, or neither.

[0077] In various embodiments, each LP 102a, 102b can manage power consumption to draw limited power from the battery, thereby reducing the device volume. Each circuit in the system can be designed to avoid large peak currents. For example, cardiac pacing can be achieved by discharging a tank capacitor (not shown) across the pacing electrodes. Recharging of the tank capacitor is typically controlled by a charge pump circuit. In a particular embodiment, the charge pump circuit is throttled to recharge the tank capacitor at a constant power from the battery.

[0078] In some embodiments, the controller 112 in one LP 102 can access the signals on the electrode 108 and can examine the output pulse amplitude, duration, etc. from another LP to be used as a signature for determining the validity of the trigger information, and for a signature that reaches within a predetermined limit, activate the delivery of the pacing pulse after a predetermined delay of zero milliseconds or more milliseconds. The predetermined delay can be preset at the time of manufacture, programmed via an external programmer, or determined by adaptive monitoring to facilitate identification of the trigger signal and distinguish the trigger signal from noise. In some embodiments or in some cases, the controller 112 can examine the output pulse waveform from another leadless cardiac pacemaker to be used as a signature for determining the validity of the trigger information, and for a signature that reaches within a predetermined limit, activate the delivery of the pacing pulse after a predetermined delay of zero milliseconds or more milliseconds.

[0079] Figure 3 An example form factor of the LPs 102a, 102b is shown. The LP can include a hermetic housing 202 (110) on which electrodes 108a and 108b are disposed. As shown, the electrode 108a can be separated from but partially surrounded by the fixation mechanism 205, and the electrode 108b can be disposed on the housing 202. The fixation mechanism 205 can be a fixation screw, a plurality of hooks, barbs, or other attachment features configured to attach the pacemaker to tissue such as heart tissue. The electrodes 108a and 108b are as referenced above Figure 2An example of the electrode 108 shown and discussed. The housing may also include an electronics compartment 210 within the housing that contains the electronic components required for the operation of the pacemaker, such as including a pulse generator, a receiver, a battery, and a processor for operation. The hermetic housing 202 may be adapted to be implanted on or in a human heart and may be, for example, cylindrical, rectangular, spherical, or any other suitable shape. The housing may include conductive, biocompatible, inert, and anodic-safe materials, such as titanium, 316L stainless steel, or other similar materials. The housing 202 may also include an insulator disposed on the conductive material to separate the electrodes 108a and 108b. The insulator may be an insulating coating on a portion of the housing between the electrodes and may include materials such as silicone, polyurethane, parylene, or another biocompatible electrical insulator commonly used in implantable medical devices. In Figure 3 an embodiment, a single insulator 208 is disposed along a portion of the housing between the electrodes 108a and 108b. In some embodiments, the housing itself may include an insulator instead of a conductor, such as alumina ceramic or other similar materials, and the electrodes may be disposed on the housing.

[0080] As Figure 3 shown, the pacemaker may also include a header assembly 212 to isolate the electrodes 108a and 108b. The header assembly 212 may be made of PEEK, tecothane, or another biocompatible plastic and may contain ceramic-to-metal feedthroughs, glass-to-metal feedthroughs, or other suitable feedthrough insulators known in the art. As used herein, the term metal also encompasses conductive alloys. The electrodes 108a and 108b may include pacing / sensing electrodes or return electrodes. A low polarization coating may be applied to the electrodes, for example, such as sintered platinum, platinum-iridium, iridium, iridium oxide, titanium nitride, carbon, or other materials commonly used to reduce polarization effects. In Figure 3 an embodiment, the electrode 108a may be a pacing / sensing electrode, and the electrode 108b may be a return electrode. The electrode 108b may be a part of the conductive housing 202 that does not include the insulator 208.

[0081] Several techniques and structures may be used to attach the housing 202 to the inner or outer wall of the heart. The screw fixation mechanism 205 may enable endocardial or epicardial insertion of the device through a guiding catheter. A twistable catheter may be used to rotate the housing and force the fixation device into the heart tissue, thereby attaching the fixation device (and Figure 2 the electrode 108a therein) in contact with the stimulable tissue. The electrode 108b may be used as a neutral electrode for sensing and pacing. The fixation mechanism may be partially or fully coated for electrical insulation, and a steroid-eluting matrix may be included on or near the device to minimize the fibrotic response, as known in conventional pacing electrode leads.

[0082] Figure 4 and Figure 5 is a schematic diagram view depicting how an external device 109 coupled to two electrodes 115a, 115b can communicate with LP 102a and / or LP 102b via conductive communication (which may also be interchangeably referred to herein as conductive communication). Such communication can occur via a two-way communication path that includes a receiving path that decodes information encoded on pulses generated by one or more of LP 102a or 102b and conducts the receiving path through body tissue to the external device 109. According to an illustrative arrangement, the two-way communication path can be configured to communicate with multiple LP 102a and 102b via two or more electrodes and conduct through body tissue. Although the external device 109 is shown coupled to Figure 4 and Figure 5 (and Figure 1 ) of the two electrodes 115a, 115b, the external device 109 can also be coupled to one or more additional external electrodes (e.g., Figure 6 and Figure 7 115c in).

[0083] The external device 109 is connected by a communication transmission channel and has transmitting and receiving functional elements for two-way exchange of information with one or more IMDs (such as LP102a and / or LP 102b). The communication channel includes two (or more) external electrodes 115a and 115b that can be attached or fixed to the skin surface. From the point on the skin, the communication transmission channel is wireless, includes the ionic medium of intracellular and extracellular body fluids, and enables electrolytic current coupling between the external electrodes (which may also be referred to as surface electrodes) and the LP (or more generally, IMD). The two-way communication path can also include a transmitting path that transfers information from the external device 109 to one or more of LP 102a and / or LP 102b via direct conduction through body tissue by modulation using a modulation signal in the range of approximately 10 kHz to 100 kHz or higher frequencies to avoid skeletal muscle stimulation.

[0084] Information sent from the external device 109 to the implanted LP 102 can be conveyed via a modulated signal. The signal is transmitted through direct conduction via a communication transmission channel. The modulated signal in this frequency range has a high enough frequency to avoid any depolarization in vivo that would cause activation of skeletal muscle and discomfort to the patient. The frequency is also low enough to avoid problems of radiation, crosstalk, and excessive attenuation of body tissue. Thus, information can be transmitted at any time, regardless of the cardiac cycle or other body processes. However, to minimize the probability that the conductive communication signal may cause capture of cardiac tissue, in certain embodiments of the present technology, the conductive communication signal can be sent during the refractory period. It should also be noted that the use of other frequency ranges is possible and within the scope of the embodiments described herein.

[0085] Figure 4 An example configuration involving the external device 109 and two endocardial implanted LPs 102a and 102b is depicted. The external device 109 is physically connected to the skin surface via two external electrodes 115a and 115b (also referred to as surface electrodes or skin electrodes), and the external electrodes 115a and 115b can serve three functions. The external electrodes 115a and 115b can be individually referred to as the external electrode 115 (or surface electrode 115 or skin electrode 115), or collectively referred to as the external electrodes 115 (or surface electrodes 115 or skin electrodes 115). First, the electrodes 115 can be used to send encoded information from the external device 109 to the LP 102 or other IMDs using a modulated signal. Second, the external electrodes 115 can be used to receive encoded information from the individual LP 102 or other IMDs. Third, the external electrodes 115 can receive or sense a surface electrocardiogram (ECG) for display, recording, and / or analysis by the external device 109. Although only two external electrodes 115 are shown in Figure 4 , more than two (e.g., three or more) external electrodes 115 can also be placed in contact with the patient to enable selection of various different communication vectors, as will be further explained in detail below, for example, with reference to Figure 6 and Figure 7 Further detailed explanation.

[0086] In Figure 4 , the LP 102 is endocardially implanted within the heart 101. Alternatively, as shown in Figure 5 , the LP 102 can be implanted by attaching to the outer surface of the heart 101. Whether the LP 102 is endocardially implanted (on the external heart surface) or epicardially implanted, the external electrodes 115 and the external device 109 are in Figure 4 and Figure 5function similarly in the arrangement shown. There is no restriction that forces all of the LPs to be implanted entirely inside the heart or entirely outside the heart. One or more LPs can be implanted endocardially together with one or more other LPs implanted on the outer surface of the heart.

[0087] Reference Figure 6 , the external device 109 is shown communicatively coupled to three external electrodes 115a, 115b, and 115c, which may be collectively referred to as external electrodes 115 or individually as external electrode 115. In Figure 6 , the external electrodes 115 are shown in contact with the patient's chest; however, this is not necessarily the case. Alternatively, one or more of the external electrodes 115 can be in contact with the patient's back, and / or with the patient's limbs or fingers, but not limited thereto. The external electrodes 115 can be physically separated from each other such that each of the electrodes can be independently placed in contact with the patient's skin at any desired location. Alternatively, the external electrodes 115 can be physically attached to the same patch or substrate while being electrically isolated from each other, such as a triangular or Y-shaped patch, etc., which can be configured to be placed on the patient's chest or back, but not limited thereto. The external device 109 can alternatively include (or be communicatively coupled to) one or more external electrodes 115 configured to be grasped by the patient's left hand, one or more external electrodes 115 configured to be grasped by the patient's right hand, and one or more electrodes 115 configured to be placed against one of the patient's thighs or ankles. Other variations are possible and within the scope of the embodiments described herein. The external device 109 can optionally be communicatively coupled to a remote patient care network, e.g., via one or more wired and / or wireless communication networks. Details of an example of the external device 109 are described below with reference to Figure 7 .

[0088] Reference Figure 7 , which shows an example block diagram of an external device 109 (e.g., an external programmer, a remote monitor, or a patient link monitor) configured to communicate with one or more IMDs (e.g., LP 102) implanted in a patient using conductive communication, where the external device 109 includes or is communicatively coupled to at least three external electrodes 115 in contact with the patient.

[0089] When the external device 109 is an external programmer, the external device can program one or more IMDs, such as one or more LPs 102, ICMs 104, and / or ICDs 106. The external device 109 can also be used to obtain diagnostic information from one or more IMDs. When the external device 109 is a remote monitor, it may not be able to program any IMDs. The external device 109 is shown as including a controller 712, a display 716, a user interface 718, a network interface 720, and a battery / power regulator 726. The battery and / or power regulator 726 provides one or more constant voltages to the various components of the external device 109 during normal operation. The external device 109 is also shown as including an ECG amplifier and / or filter 714, a conductive communication receiver (RX) 742, and a conductive communication transmitter (TX) 732. In this example embodiment, the receiver 742 is shown as including a message amplifier and / or filter 740 and a message decoder 738, and is configured to receive a conductive communication signal from one or more LPs (e.g., 102a and / or 102b). The message decoder 738 can also be implemented by or within the controller 712. The controller 712 for controlling the operation of the external device 702 can include, for example, one or more processors (or equivalent control circuitry), logic and timing circuitry, state machine circuitry, and / or I / O circuitry, but is not limited thereto. The controller 712 can include a random access memory (RAM) and / or a read only memory (ROM), and / or can be coupled to a memory 722. More generally, the memory 722, which can include RAM and / or ROM, can be within and / or external to the controller 712 and coupled to the controller 712. The controller 712 can also include a clock circuit, or a separate clock circuit (not shown) can provide a clock signal to the controller 712.

[0090] When Figure 7In the illustrated embodiment, the external device 109 is shown connected to three external electrodes 115a, 115b, and 115c, which may be collectively referred to as electrode 115 or individually as electrode 115. The electrode 115 is shown connected to a switch 713, which is shown including a first switch set 713a, a second switch set 713b, and a third switch set 713c. The external electrode 115 may be located on the housing of the external device 109 or may be separated from such housing (i.e., remote from such housing). In the case where the electrode 115 is separated from the housing of the external device 109, each electrode 115 may be attached to a separate respective wire, or the electrode 115 may be attached to an additional housing that is communicatively coupled to the external device 109 via one or more wires or via a wireless connection (e.g., using Bluetooth or WiFi, but not limited thereto). Other variations are possible and are within the scope of the embodiments described herein. As will be described in more detail below, the external electrode 115 may be used to transmit and receive conductive communication signals to / from one or more LPs and / or one or more other types of IMDs and may optionally also be used to sense ECG.

[0091] The external electrode 115 is intended to contact the patient's skin. For example, the external electrode 115 can be a skin electrode configured to be attached to the patient's torso (e.g., chest and / or back) via an adhesive and / or gel. For another example, the external electrode 115 can be configured to be touched by one or more fingers on each hand of the patient, or to contact the patient's wrist, the patient's limb, or the patient's chest, but is not limited thereto. A set of switches 713a is connected between the electrode 115 and the ECG amplifier and / or filter 714, a set of switches 713b is connected between the electrode 115 and the receiver 742, and an additional set of switches 713c is connected between the electrode 115 and the transmitter 732. The sets of switches 713a, 713b, 713c can be collectively referred to as the switch set 713 or the switch 713. Each switch set 713 is controlled by the controller 712. In some embodiments, the amplifiers and / or filters 714, 740, and 736 are each differential circuits intended to be connected to a pair of electrodes 115 via the switch 713 under the control of the controller 712. For example, the switch 713b can be controlled to connect any pair of electrodes 115a, 115b, 115c to the message amplifier and / or filter 740 (which can also be referred to as the message amplifier / filter 740). For a more specific example, the switch 713b can connect the electrode 115a to the first input of the message amplifier / filter 740, and connect the electrode 115b to the second input of the message amplifier / filter 740, and not connect the electrode 115c to any input of the message amplifier / filter 740. The switch can also directly connect two electrodes 115 to each other. For example, the switch 713b can connect the electrode 115a to the first input of the message amplifier / filter 740, and connect the electrodes 115b and 115c to each other and to the second input of the message amplifier / filter 740. Advantageously, connecting two or more electrodes (e.g., 115b and 115c) together to the same node (e.g., to the same input node of the message amplifier / filter 740) can effectively average or create a virtual vector between two or more electrode positions, which enables sensing a signal that is actually the average of the signals detected at two separate electrodes. This is an example where the combination of three electrodes 115a, 115b, and 115c includes all three electrodes, where the electrode 115a is separated from the other electrodes, and the electrodes 115b and 115c are electrically coupled to each other. Including three (or more) external electrodes 115 enables sensing the ECG at multiple vectors and / or enables selection from multiple vectors for conductive communication with one or more implanted LPs, such that the conductive communication quality can be improved or maximized.

[0092] As described above, the conductive communication receiver 742, shown as including a message amplifier and / or filter 740 and a message decoder 738, is configured to receive a conductive communication signal from one or more LPs (e.g., 102a and / or 102b). The message amplifier and / or filter 740 is configured to amplify and / or filter the conductive communication signal received from the LP (e.g., 102a and / or 102b). The amplifier portion can be used to increase the relatively small amplitude of such a conductive communication signal. The filter portion can be a high-pass filter or a band-pass filter adapted to separate the ECG signal from the conductive communication signal. The message amplifier and / or filter 740 is an example of a sensing circuit system configured to use a sensing vector to generate a sensing signal, the sensing vector including at least two electrodes configured to contact the patient.

[0093] The message decoder 738 can be configured to decode the conductive communication signal received from the LP into a format that can be understood by the controller 712. The particular type of decoding performed by the message decoder 738 depends on the particular encoding of the conductive communication signal received from the LP, such as on-off keying, frequency shift keying, frequency modulation, or amplitude shift keying, but is not limited thereto. The message decoder 738 can also be implemented within the controller 712, e.g., by a digital signal processor (DSP) of the controller 712.

[0094] The conductive communication transmitter 732 is configured to (under the control of the controller 712) transmit a conductive communication signal to one or more IMDs implanted in a patient. An example of a conductive communication signal that can be transmitted by an external device 109, such as an external programmer or a remote monitor, is an acknowledgment (ACK) sequence of conductive communication pulses that notifies one or more LPs that the external device 109 is in proximity to the LP and / or other types of IMDs and is capable of receiving data (encoded as conductive communication pulses) from the LP and / or other types of IMDs. The conductive communication signal can also be used for programming, interrogating, and / or obtaining notifications and / or other types of diagnostic information from one or more LPs and / or other types of IMDs.

[0095] In this exemplary embodiment, the transmitter 732 is shown as including a message encoder and / or modulator 730 and an amplifier 736. The message encoder and / or modulator 730 may be configured to encode and / or modulate the signal output from the controller 712 into a format understandable by an IMD (such as an LP). The specific type of encoding performed by the message encoder depends on the specific type of encoding understandable by the IMD, such as on-off keying, frequency shift keying, frequency modulation, or amplitude shift keying, but is not limited thereto. The amplifier 736 is coupled to the encoder / modulator 730 to increase the amplitude of the pulses included in the conducted communication signal to a level sufficient for one or more IMDs to receive the conducted communication signal from the external device 109. The message encoder and / or modulator 730 may also be implemented by the controller 712, for example, by the DSP of the controller 712.

[0096] The controller 712 may receive ECG data and optionally use the display 716 to display the ECG, and may also display information included in other data, such as battery voltage, sensed cardiac signal amplitude, and / or other system status information, which is obtained from the implanted IMDs acquired through the encoded pulses included in the conducted communication signal. The controller 712 may also accept input from the user via the user interface 718, which may include, for example, a keyboard and / or a touch screen, but is not limited thereto. In the case where the display 716 is a touch screen type display, the display 716 may also provide the user interface 718 or at least a part thereof. The controller 712 may also communicate with other data input or display units (such as a handheld computer or a laptop / desktop unit) via the network interface 720. The network interface 720 may be wired or wireless and may also enable communication with a local area network or the Internet for greater connectivity. More specifically, the network interface 720 can be used to transfer ECG data, diagnostic data, and other types of data collected from one or more IMDs to a patient care network associated with a medical group and / or facility. For a more specific example, the network interface may include a Bluetooth antenna, a WiFi antenna, and / or an Ethernet connection, but is not limited thereto.

[0097] The controller 712, which may include one or more processors, etc., may perform operations based on firmware stored in non-volatile memory (flash memory) (such as 118). The non-volatile memory may also be used to store parameters or values to be maintained when power is removed. The controller 712 may use volatile memory or random access memory (RAM) as a general memory for information such as ECG data, status information, swap memory, and other data.

[0098] The external device 109 may include or be coupled to more than three external electrodes 115. For example, the external device 109 may include or be coupled to four, five, six, or seven external electrodes 115, but is not limited thereto, wherein the greater the number of external electrodes, the greater the number of potential communication vectors to be tested and selected.

[0099] At least some of the external electrodes 115 of the external device 109 may be used to sense ECG signals, as well as to sense the conducted communication signals output by one or more IMDs. The external electrodes 115 of the external device 109 may also be used to receive intracardiac electrogram (EGM) signal data included in the conducted communication signals output by one or more IMDs, and the EGM signal data may be received by the external device 109 (using the external electrodes 115) and used to reproduce one or more EGM signals sensed by one or more IMDs, wherein the EGM signals may also be referred to as intracardiac electrograms (IEGM) signals. In addition to being able to communicate with one or more IMDs via conducted communication, the external device 109 may optionally have an antenna and RF communication capabilities that enable the external device 109 to wirelessly communicate with implantable devices, such as the ICM 104, via a wireless communication protocol, examples of which were discussed above. The external device 109 may also include an induction coil that enables the external device to perform inductive communication with an IMD having such capabilities.

[0100] The external device 109 may take many physical forms, but fundamentally, it should be able to establish a conducted communication vector with the patient such that it can detect the conducted communication transmissions of one or more IMDs, decrypt the communication protocol used by the IMDs, and upload any acquired subsequent information to a patient care network, such as the Merlin.net™ patient care network operated by Abbott Laboratories (Abbott Park commercial center, Abbott Park, Illinois).

[0101] For example, in a case where the external device 109 has or is communicatively coupled to three external electrodes 115a, 115b, and 115c (which may be referred to as the first external electrode, the second external electrode, and the third external electrode, respectively), the external device may test and select among a first subset, a second subset, and a third subset of the external electrodes, where the first subset includes the first external electrode and the second external electrode (i.e., 115a and 115b), the second subset includes the first external electrode and the third external electrode (i.e., 115a and 115c), and the third subset includes the second external electrode and the third external electrode (i.e., 115b and 115c). According to certain embodiments of the present technology, the external device 109 may identify which one of the multiple subsets, or more generally, which one of the multiple possible communication vectors, is the preferred communication vector for communicating with the IMD. In a case where multiple IMDs are implanted in a patient, the external device may determine that different communication vectors are preferred for different IMDs. However, the external device may also determine that the same communication vector is preferred for communicating with two or more different IMDs.

[0102] The external device 109 may be used to perform the various methods described herein. For example, the external device 109 may perform the steps of the methods described below with reference to Figure 8C which are described as being performed by the EMD. The external device 109 may additionally or alternatively be used to perform the methods described below with reference to Figure 11A which are described as being performed by the EMD. The external device 109 may additionally or alternatively be used to perform the methods described below with reference to Figure 11B which are described as being performed by the EMD. The external device 109 may additionally or alternatively be used to perform the methods described below with reference to Figure 12A which are described as being performed by the EMD or the methods described below with reference to Figure 12B which are described as being performed by the EMD. Although in Figure 7 the external device 109 is shown as including three external electrodes 115, the external device 109 may alternatively include as few as two external electrodes 115, or may alternatively include more than three external electrodes 115, depending on the particular implementation. For example, in the following discussion of Figures 13A to 13D the external device 109 is shown and described as including seven external electrodes 115.

[0103] Notification Sequence and Frame

[0104] According to certain embodiments of the present technology, when the LP is not in an active conductive telemetry session with the external device 109, the LP 102 uses at least two of two or more implantable electrodes of the LP to periodically output an advertisement sequence. When the IMD (e.g., LP 102) is not in an active conductive telemetry session with the external device, it can also be said that the IMD is in an inactive conductive telemetry session with the external device.

[0105] According to certain embodiments, the advertisement sequence is a predetermined sequence (or one of a plurality of predetermined sequences) of conductive communication bit signatures that indicates to the external device 109 that the LP 102 (or other type of IMD) is implanted in a patient, and that allows an active conductive telemetry session to be initiated and occur when an open-link command is sent from the external device 109 and received by the LP 102 (or other type of IMD). The advertisement sequence may also be referred to herein as a sniff sequence (or more simply as a sniff), an advertising sequence, an advertisement notification, or an advertising notice. Preferably, the sniff is sent relatively infrequently in order to conserve the battery of the LP 102. According to certain embodiments, when the LP is not in an active conductive telemetry session with the external device 109, the LP 102 sends a sniff once every M cardiac cycles during a refractory period, where M is an integer preferably greater than 1, e.g., M = 6, 7, or 8, but is not limited thereto.

[0106] Figure 8A An example format of the sniff sequence 802 is shown. As described above, the sniff sequence 802 may also be referred to as the sniff 802, the advertisement sequence 802, the advertising sequence 802, the advertisement notification 802, or the advertising notice 802. Refer to Figure 8A, the sniff 802 is shown as including a preamble 810, followed by a device address 818. In an embodiment, the preamble 810 is one byte (also referred to as an octet) that includes a first predetermined preamble portion 814 (also referred to as the first nibble of 4 bits) having a first predetermined hexadecimal value and a second predetermined preamble portion 816 (also referred to as the second nibble of 4 bits) having a second known hexadecimal value. The device address is one of a plurality (e.g., four) of possible device addresses corresponding to the type and / or location of the IMD. For example, the LP 102a configured to be implanted in or on the right atrial chamber may have a first device address, and the LP 102b configured to be implanted in or on the right ventricular chamber may have a second device address, both of which are known to the external device 109, such that the external device can determine the type and / or location of the IMD that sent the sniff 802 based on the device address 818 included in the sniff 802 received by the external device 109. The LP 102a may also have one of two possible addresses, depending on whether the LP 102a is a new device that still needs to be configured or an old device that has already been configured. Similarly, the LP 102b may also have one of two possible addresses, depending on whether the LP 102b is a new device that still needs to be configured or an old device that has already been configured.

[0107] In response to receiving the sniff 802 from the LP 102, the external device 109 may send an open link command to the LP 102 that sent the sniff 802 in order to establish an active telemetry session with the IMD. If the LP 102 successfully receives the open link command from the external device 109, an active telemetry session may be established between the external device 109 and the LP 102.

[0108] When an active conductive telemetry session is established between the external device 109 and the LP 102 (or other type of IMD), conductive telemetry frames are used to send commands, flags, and / or payload data between the external device 109 and the LP 102 (or other type of IMD). For most of the remainder of this discussion, it is assumed that the active conductive telemetry session under discussion is between the external device 109 and the LP 102. However, it should be understood that an active conductive telemetry session may alternatively or additionally be established between the external device 109 and another type of IMD (such as an ICM or ICD).

[0109] Once an active conductive telemetry session is established between the external device 109 and the LP 102, the active conductive telemetry session can continue until an end telemetry session command is sent by the external device 109 to the LP 102 and successfully received by the LP. When the LP receives and processes the close link command, the LP device will immediately stop all transmissions of frame segments and will resume sending sniffs periodically. If the external device 109 has established active conductive telemetry sessions with multiple LPs 102 during the same time period, the external device 109 can send the close link command to all LPs 102, or the external device 109 can selectively send the close link command to one or more LPs 102 without changing the existing telemetry sessions established with one or more other LPs 102. The active conductive telemetry session can also be terminated by the LP 102 without the LP receiving a close link command from the external device, for example, in response to the LP 102 not receiving a valid command from the external device within at least a specified time period (e.g., 6, 8, or 10 seconds, but not limited thereto) or within at least a specified number of cardiac cycles (e.g., 7, 8, 9, or 10 cardiac cycles, but not limited thereto). Example reasons why the LP 102 may not receive a valid command from the external device 109 within at least the specified time period or specified number of cardiac cycles can be because one or more of the external electrodes 115 are no longer in physical contact with the skin of the patient in which the LP 102 is implanted.

[0110] In the case of conducting a communication signal from an external device 109 to the LP 102 (or other type of IMD), the conducted communication signal may also be referred to as an external-to-implant (e2i) communication signal, or more simply as a conducted e2i signal. In the case where the external device 109 is a programmer, the conducted e2i signal sent from the external programmer to the LP 102 (or other type of IMD) may be more specifically referred to as a programmer-to-implant (p2i) communication signal, or more simply as a conducted p2i signal. In other words, a conducted p2i signal is a specific type of conducted e2i signal. In the case of conducting a communication signal from the LP 102 (or other type of IMD) to the external device 109, the conducted communication signal may also be referred to as an implant-to-external (i2e) communication signal, or more simply as a conducted i2e signal. In the case where the external device 109 is a programmer, the conducted i2e signal sent from the LP 102 (or other type of IMD) to the external programmer may be more specifically referred to as an implant-to-programmer (i2p) communication signal, or more simply as a conducted i2p signal. In other words, a conducted i2p signal is a specific type of conducted i2e signal. Conducted communication signals are sometimes also referred to as conducted communication signals, and these terms are generally used interchangeably.

[0111] Frames occur when the LP 102 is in an active conducted telemetry session with the external device 109. As can be understood from the following discussion, each frame may include an i2e signal and an e2i signal. Thus, a frame can be considered a period of time during which conducted communication pulses are sent in one or both directions between the LP 102 and the external device 109. During an active conducted telemetry session, multiple frames may occur during the same refractory period of the same cardiac cycle, and frames may occur during consecutive cardiac cycles (within consecutive refractory periods).

[0112] Figure 8BShows an example format of a frame 804 according to an embodiment of the present technology. The frame is shown as including a header 812, followed by a body 822. When a write command is included in the frame, an acknowledgment (ACK) or negative acknowledgment (NACK) 832 may follow the body 822, where the ACK or NACK may be used to indicate whether a cyclic redundancy check (CRC) code of data (written in response to a write command sent by an external device to an LP or other type of IMD) is valid. More specifically, an IMD that receives a write command from an external device may use the ACK to indicate that the payload data received from the external device is valid, as determined based on the associated CRC code, and may use the NACK to indicate that the payload data received from the external device is invalid, as determined based on the associated CRC code. It should thus be understood that not all frames will include an ACK or NACK 832. In some embodiments, when the IMD issues a NACK, it does not write the payload data to its memory (e.g., 118).

[0113] In some embodiments, the header 812 has the same format as the sniff 802 described above with reference to Figure 8A Accordingly, the header 812 includes a preamble 810, followed by an IMD address 818. The header 812 of the frame 804 may also have a different format from the sniff 802. However, when discussing the frame 804, unless otherwise stated, it is assumed that the header 812 has the same format as the sniff 802. In an embodiment, the preamble 810 is one byte (also referred to as an octet), which includes a first predetermined preamble portion 814 (also referred to as the first nibble of 4 bits) having a first predetermined hexadecimal value and a second predetermined preamble portion 816 (also referred to as the second nibble of 4 bits) having a second known hexadecimal value. The IMD address is one of a plurality (e.g., four) of possible addresses corresponding to the type of the IMD and / or the location of the IMD.

[0114] The body 822 of the frame 804 includes a plurality of segments 824, 826, and 828, which are also labeled as segment 1, segment 2, and segment 3 in Figure 8B The first segment 824 (i.e., segment 1) includes a command (optionally followed by one or more command arguments) and a first CRC code (i.e., CRC1). The second segment 826 (i.e., segment 2) includes marker data and a second CRC code (i.e., CRC2). The third segment 828 (i.e., segment 3) includes payload data and a third CRC code (CRC3).

[0115] Commands and arguments included in the first paragraph (i.e., paragraph 1) are sent by external device 109 to LP 102 (or other type of IMD) to cause the LP 102 (or other type of IMD) to which the command is sent to perform a specific operation specified by the command. Example types of commands include open link commands (also known as start telemetry session commands), close link commands (also known as end telemetry session commands), keep link active commands, read type commands, and write type commands, to name a few. Each command included within the first paragraph (i.e., paragraph 1) may also be followed by one or more arguments. The first CRC code (i.e., CRC1) included in the first paragraph (i.e., paragraph 1) is used by the LP 102 (or other type of IMD) that receives the command to determine whether the command included in the first paragraph (i.e., paragraph 1) has been correctly decoded by the LP 102 (or other type of IMD), and more generally, is used by the receiving LP 102 (or other type of IMD) to determine whether there are errors in the received and decoded command. If there are errors, the command is rejected and thus not run.

[0116] The marker data included in the second paragraph (i.e., paragraph 2) is used by the LP 102 (or other type of IMD) to notify the external device 109 of cardiac events detected by the LP 102 (or other type of IMD). For example, the marker can be used to notify the external device of R waves, P waves, tachycardia detection, atrial fibrillation detection, etc. Thus, the marker data may also be referred to herein as cardiac event data. The second CRC code (i.e., CRC2) included in the second paragraph (i.e., paragraph 2) is used by the external device 109 that receives the marker data (also referred to as cardiac event data) to determine whether the marker data included in the second paragraph (i.e., paragraph 2) has been correctly decoded by the external device 109, and more generally, is used by the external device 109 to determine whether there are errors in the received and decoded marker data. If there are errors, the marker data is rejected and thus not used.

[0117] The payload data included in the third paragraph (i.e., paragraph 3) can be, for example, data read by the external device 109 from the LP 102 (or other type of IMD), or data written by the external device 109 to the LP 102 (or other type of IMD), depending on whether the command included in paragraph 1 is a read type command or a write type command. The third CRC code (i.e., CRC3) included in the third paragraph (i.e., paragraph 3) is used by the external device 109 that receives the read data, or by the LP 102 (or other type of IMD) that writes the data, to determine whether there are errors in the read or written data, and thus, whether another frame should be used to reread or rewrite the data.

[0118] The advantage of each of the segments (segment 1, segment 2, and segment 3) of the body 822 (including its own respective CRC code) is that a device decoding the frame does not need to wait until the end of the frame to determine whether the decoded frame or a portion thereof is valid. Additionally, in the case where each segment (segment 1, segment 2, and segment 3) of the body 822 of the frame 804 includes its respective CRC code, if the external device 109 is only interested in certain segments of the frame and not in other segments, the external device 109 can utilize the valid segments it receives, even if there is an error in another segment of the same frame. For example, if the external device 109 is only interested in the payload data received from the LP in response to a read-type command and not in the tag data (or if the payload data is useful independently of the tag data), the external device 109 can determine whether the payload data is valid based on CRC3 alone and use that data, even if the tag data is found to be invalid based on CRC2. More generally, in the case where each segment (segment 1, segment 2, and segment 3) of the body 822 of the frame 804 includes its own respective CRC code, the external device 109 can use one or more valid segments, even if one or more other segments are invalid, as determined by the external device based on the CRC codes included in the respective segments.

[0119] Figure 8C is a high-level flowchart for outlining a method for providing communication between an external medical device (EMD) and an IMD using a frame (such as Figure 8B the frame 804 introduced therein), where the frame includes a header (e.g., 812) and a body (e.g., 822). In an embodiment, the EMD and IMD that execute the method outlined in Figure 8C can be the external device 109 and the LP 102, respectively, the example details of which are described above with reference to Figures 1 to 7 . The method outlined in Figure 8C can be executed during an active conductive telemetry session between the external device 109 and the LP 102 (or other types of IMDs). Refer to Figure 8C, step 842 involves the EMD including, within the first segment of the frame (e.g., 824), a command generated by the EMD and a first cyclic redundancy check (CRC) code, and the EMD transmitting the first segment of the body of the frame. Step 844 involves the IMD including, within the second segment of the frame (e.g., 826), cardiac event data (also known as marker data) generated by the IMD and a second CRC code, and the IMD transmitting the second segment of the body of the frame. Step 846 involves one of the EMD and the IMD including, within the third segment of the frame (e.g., 826), payload data and a third CRC code generated by one of the EMD and the IMD, and one of the EMD and the IMD transmitting the third segment of the body of the frame. Which particular one of the EMD or the IMD generates the payload data and the third CRC code to be included in the third segment of the body of the frame may depend on the command included in the first segment of the body of the frame (e.g., 824). For example, in the case where the command included in the first segment of the body of the frame is a read-type command used by the EMD to read data from the memory of the IMD (e.g., 118), the payload data will include the data read from the IMD, and thus, in response to the read-type command received from the EMD in the first segment of the body of the frame, the IMD will generate the payload data and the third CRC code. In contrast, in the case where the command included in the first segment of the body of the frame is a write-type command used by the EMD to write data to the memory of the IMD (e.g., 118), the payload will include the data written to the IMD by the EMD, and thus the payload data and the third CRC code will be generated by the EMD.

[0120] Still referring to Figure 8C , step 848 involves the IMD receiving the first segment of the body of the frame and determining, based on the first CRC code, whether an error exists in the first segment of the body of the frame. At step 850, it is determined whether an error exists in the first segment of the body of the frame. If the answer to the determination at step 850 is no, the process proceeds to step 852 and the IMD accepts the command. If the answer to the determination at step 850 is yes, the process proceeds to step 854, and the IMD rejects the command and thus does not execute the command. More generally, the IMD accepts the command included in the first segment in response to determining that the first segment does not include an error, or does not accept (also known as rejects) the command included in the first segment in response to determining that the first segment includes an error.

[0121] Step 856 relates to the second paragraph of the body of the EMD received frame, and the EMD determines whether there is an error in the second paragraph of the body of the frame based on the second CRC code. At step 858, it is determined whether there is an error in the second paragraph of the body of the frame. If the answer to the determination at step 858 is no, the process proceeds to step 860, and the EMD accepts the cardiac event data. If the answer to the determination at step 858 is yes, the process proceeds to step 862, and the EMD rejects the command and thus does not execute the command. More generally, the EMD accepts the cardiac event data included in the second paragraph in response to determining that the second paragraph does not include an error, or rejects the cardiac event data included in the second paragraph in response to determining that the second paragraph includes an error.

[0122] Step 864 relates to the other of the IMD or the EMD (i.e., the one that did not send the third paragraph) receiving the third paragraph of the body of the frame and determining whether there is an error in the third paragraph of the body of the frame based on the third CRC code. At step 866, it is determined whether there is an error in the third paragraph of the body of the frame. If the answer to the determination at step 866 is no, the process proceeds to step 868, and the other of the IMD or the EMD (i.e., the one that did not send the third paragraph) accepts the payload data. If the answer to the determination at step 866 is yes, the process proceeds to step 870, and the payload is rejected. More generally, the other of the IMD or the EMD accepts the payload data included in the third paragraph in response to determining that the third paragraph does not include an error, or rejects the payload data included in the third paragraph in response to determining that the third paragraph includes an error.

[0123] Briefly returning to the reference Figure 8B , in some embodiments, the header (e.g., 812) is always generated by the IMD and includes a preamble (e.g., 810) and the device address of the IMD that generated the header (e.g., 818). In some embodiments, the frame also includes one of an acknowledgement (ACK) or a negative acknowledgement (NACK), which respectively specify whether the payload data written to the memory of the IMD (e.g., 118) is valid as determined based on the third CRC code. This enables the EMD to know whether the EMD should re - send some payload data that it attempted to write to the memory of the IMD. In some embodiments, when the IMD issues a NACK, it does not write the payload data to its memory. Instead, when the IMD issues an ACK, it acknowledges that the IMD writes the payload data to its memory.

[0124] A benefit of using three different CRC codes is that portions of a frame can be used even if other portions include errors. For example, in response to the IMD determining that there are no errors in the first segment of the body of the frame, regardless of whether there are errors in the second and / or third segments of the body of the frame, the IMD accepts and executes the command. For another example, in response to the external device determining that there are no errors in the second segment of the body of the frame, regardless of whether there are errors in the first and / or third segments of the body of the frame, the external device accepts the cardiac event data. For another example, in response to determining that there are no errors in the third segment, one of the IMD or the external device (which does not include the third CRC code in the third segment) can accept the payload data, regardless of whether there are errors in the first and / or second segments of the body of the frame.

[0125] Reference again Figure 8C , the actual order of executing each step can be Figure 8C Therefore, the order shown in Figure 8C The outlined approach is not limited to Figure 8C For example, step 848 (or at least the receiving portion of step 848) may be performed between steps 842 and 844. For another example, step 856 (or at least the receiving portion of step 856) may be performed between steps 844 and 846. In addition, it should be understood that for ease of description, this document generally defines Figure 8C Therefore, it should be understood that Figure 8C As shown and referenced in Figure 8C Some of the steps described can be divided into multiple steps. For example, step 848 can be described as two separate steps, one of which includes receiving the first segment of the frame and the other includes determining whether there is an error in the first segment of the frame based on the first CRC code. For another example, step 856 can be described as two separate steps, one of which includes receiving the second segment of the frame and the other includes determining whether there is an error in the second segment of the frame based on the second CRC code. As another example, step 864 can be described as two separate steps, one of which includes receiving the third segment of the frame and the other includes determining whether there is an error in the third segment of the frame based on the third CRC code.

[0126] Briefly return to reference Figure 8A, assuming for example that the preamble 810 of the sniff 802 includes one byte (i.e., 8 bits), and the IMD address 818 includes another type (i.e., another 8 bits), then the sniff 802 will include a total of 2 bytes (i.e., 16 bits). In those embodiments where the sniff 802 and the header 812 of the frame 804 have the same format, this may also mean that the header 812 of the frame 804 also includes 2 bytes (i.e., 16 bits). The length of the device address 818 can also be a byte, for example. Each segment of the body 822 can include multiple bytes, for example, where the length of each CRC is a byte. Other variations are possible and within the scope of the embodiments described herein. For example, the preamble 810 can alternatively be greater than or less than one byte, and / or the IMD address 818 can alternatively be greater than or less than one byte. Each bit in the sniff 802 and the frame 804 is a binary bit that can have a bit value of '1' or '0'. A corresponding conductive communication signature can be used to transmit the '1' bit value within a time window, and another corresponding conductive communication signature can be used to transmit the '0' bit value within a time window. Each such time window has a specified duration, for example, about 30 microseconds (us), but is not limited thereto.

[0127] Figure 9A An example conductive communication signature 902 for representing a '1' bit value within each of the time windows 912 and 914 is shown, and an example conductive communication signature 904 for representing a '0' bit value within another time window 916 is shown, where each of the time windows 912, 914, and 916 is about 30 us, for example. In this example embodiment, the conductive communication signature 902 for representing a '1' bit value includes four biphasic pulses within the time window, and the conductive communication signature 902 for representing a '0' bit value does not include biphasic pulses within the time window. For the remainder of this specification, assume Figure 9A that these signatures 902 and 904 shown in are the signatures for representing a '1' bit value and a '0' bit value, respectively. However, it should be understood that the conductive communication signature 902 can also be used to represent a '0' bit value, and the conductive communication signature 904 can also be used to represent a '1' bit value, or completely different corresponding conductive communication signatures are used to represent a '1' bit value and / or completely different corresponding conductive communication signatures are used to represent a '0' bit value. Figure 9B An example of a conductive communication signal is shown that includes Figure 9A an instance of the signature represented in after the conductive communication signal has been transmitted by the IMD through the patient tissue, and has been received by the external device, and amplified and filtered by the external device. Figure 9B Alternatively, an example of a conductive communication signal can be shown that includes Figure 9A an instance of the signature represented in after the conductive communication signal has been transmitted by the external device through the patient tissue, and has been received by the IMD, and amplified and filtered by the IMD.Figure 9B Alternatively, a conducted communication signal including an instance of the signature represented in Figure 9A is shown after the conducted communication signal has been transmitted by the first IMD, received by the second IMD, and amplified and filtered by the second IMD.

[0128] In some embodiments, a device (receiving a conducted communication signal from another device) decodes the conducted communication signal in part by detecting an edge of the received conducted communication signal (i.e., by performing edge detection). More specifically, an edge is detected when the received conducted communication signal, after being amplified and filtered, exceeds an edge detection threshold (e.g., transitions from below the edge detection threshold to above the edge detection threshold). To accurately detect edge detection, the receiving device (e.g., external device 109) needs to use an appropriate edge detection threshold. This is because if the edge detection threshold is set too low, noise may cause inappropriate edge detection to be triggered. Conversely, if the edge detection threshold is set too high, edge detection may be missed when it should be triggered. In other words, an edge detection threshold set too low may result in false positive edge detection, and an edge detection threshold set too high may result in false negative edge detection. Such false positive edge detection and / or false negative edge detection may, for example, cause a device (e.g., an external device or an IMD) to fail to receive and decode a valid message. Certain embodiments of the present technology, described below with reference to Figure 10 and FIG. 11, are used to define and utilize an appropriate edge detection threshold.

[0129] Figure 10 is a high-level block diagram for describing how an edge detection threshold can be determined by an external device 109 for performing conducted communication with an LP 102 (or other type of IMD). Figure 10 Elements that are the same as those introduced in the previously described figures in Figure 10 are labeled the same in Figure 10, the external device 109 is shown as including a switch 713b that is operative to electrically connect a selected one of the external electrodes 115 to the differential inputs of a message amplifier / filter 740 of a conductive communication receiver (RX) 742. The message amplifier / filter 740 is shown as including an amplifier 1002, followed by a filter 1004, which is optionally followed by another amplifier 1006. The switch 713 can, for example, electrically connect the external electrodes 115a and 115b to the non-inverting (+) and inverting (-) inputs of the amplifier 1002, respectively. The amplifier 1002 amplifies the difference between the voltages sensed by the external electrodes 115a and 115b (or some other electrode sensing vector) and provides the amplified signal to the filter 1004. The filter 1004 can be, for example, a fourth-order bandpass filter, but is not limited thereto. The filtered signal output by the filter 1004 is then optionally amplified by another amplifier 1006, which can be used to compensate for the attenuation caused by the filter 1004. The amplifier 1002 can have a relatively high gain (e.g., 60x) to amplify the relatively low-amplitude signals received by the external device 109 from the LP 102 (or other type of IMD). In comparison to the gain of the amplifier 1002, the optional amplifier 1006 will likely have a relatively low gain (e.g., 4x). The signal 1007 output by the message amplifier / filter 740 can be referred to as the amplified and filtered received conductive communication signal 1007, or more simply as the received conductive communication signal. The received conductive communication signal 1007 is shown as being provided to an edge detection comparator 1008. The edge detection comparator 1008 compares the received conductive communication signal 1007 with an edge detection threshold determined in accordance with an embodiment of the present technique, as will be described below. The edge detection comparator 1008 can also be referred to herein as the comparator circuit 1008, which is configured to produce an edge detection.

[0130] Still referring to Figure 10, the received conducted communication signal 1007 is also provided to the amplitude detector 1010. In one embodiment, the amplitude detector 1010 is implemented using an analog-to-digital converter (ADC). The output of the amplitude detector 1010 is provided to the edge detection threshold determination module 1012, which can be implemented by the controller 712 using its hardware, firmware, and / or software, or alternatively can be implemented external to the controller 712. The edge detection threshold determination module 1012, or more generally, the controller 712 determines the noise baseline of the signal received by the RX 742 and sets the edge detection threshold at an appropriate level slightly above the noise baseline. The purpose of setting the edge detection threshold slightly above the noise baseline is to prevent noise from inappropriately triggering edge detection. However, as described above, the edge detection threshold should not be set too high, as doing so may cause edge detection to be missed when it should be triggered.

[0131] According to an embodiment, when such amplitude values are not samples of pulses included in a sniff or frame, the noise baseline is determined by determining the average of a plurality (e.g., 2, 3, 5, or 10) of amplitude values (e.g., ADC count values) output by the amplitude detector 1010. According to another embodiment, when such amplitude values are not samples of pulses included in a sniff or frame, the noise baseline is determined by determining the maximum value (aka peak) of a plurality (e.g., 2, 3, 5, or 10) of amplitude values (e.g., ADC count values) output by the amplitude detector 1010. According to an embodiment, in the case where the amplitude detector 1010 is implemented as an ADC, the count values output by the ADC can optionally be multiplied by a conversion factor to convert the count values to voltage amplitude values. Other variations are possible and are within the scope of the embodiments described herein.

[0132] One or more equations, look-up tables, etc. can be used to specify the edge detection threshold based on the noise baseline such that the edge detection threshold is higher than the noise baseline. In an embodiment, the equation edge detection threshold = scaling multiplier * noise baseline is used, where the noise baseline is determined based on the signal amplitude measurement generated by the amplitude detector 1010, which can be implemented as an ADC as described above, and the scaling multiplier is determined using empirical data and / or simulation. The same scaling multiplier can be used regardless of the noise baseline, or different scaling multipliers can be used for different ranges of the value of the noise baseline, e.g., a first scaling multiplier can be used when the noise baseline is in a first range and a second scaling multiplier can be used when the noise baseline is in a second range, etc., depending on how many ranges are defined.

[0133] In another embodiment, the equation Edge Detection Threshold = Noise Baseline + Offset is used, where the Noise Baseline is determined based on the signal amplitude measurement generated by the amplitude detector 1010, which can be implemented as an ADC as described above, and the Offset is determined using empirical data and / or simulation. Regardless of the Noise Baseline, the same Offset can be used, or different Offsets can be used for different ranges of values of the Noise Baseline. For example, a first Offset can be used when the Noise Baseline is in a first range, and a second Offset can be used when the Noise Baseline is in a second range, etc., depending on how many ranges are defined.

[0134] In an embodiment, the equation Edge Detection Threshold = Scaling Multiplier * Noise Baseline + Offset is used, where the Noise Baseline is determined based on the signal amplitude measurement generated by the amplitude detector 1010, which can be implemented as an ADC as described above, and the Scaling Multiplier and the Offset are determined using empirical data and / or simulation. Regardless of the Noise Baseline, the same Scaling Multiplier and Offset can be used, or different Scaling Multipliers and / or Offsets can be used for different ranges of values of the Noise Baseline. For example, a first Scaling Multiplier and a first Offset can be used when the Noise Baseline is in a first range, and a second Scaling Multiplier and a second Offset can be used when the Noise Baseline is in a second range, etc., depending on how many ranges are defined. Using different Scaling Multipliers and / or Offsets based on whether the Noise Baseline is within a first range, a second range, etc. is one way of using different equations depending on which range the Noise Baseline is in.

[0135] It should also be understood that, in addition to the equations described above, other equations can alternatively be used to determine the Edge Detection Threshold based on the determined Noise Baseline such that the Edge Detection Threshold is higher than the Noise Baseline while still being within the scope of the embodiments described herein. In other embodiments, one or more look up tables (LUTs) can be used instead of one or more equations to determine the Edge Detection Threshold based on the Noise Baseline such that the Edge Detection Threshold is higher than the Noise Baseline.

[0136] Once the controller 712 or its Edge Detection Threshold Determination Module 1012 determines the Edge Detection Threshold, the controller 712 can control the potentiometer 1014, etc. to set the Edge Detection Threshold used by the Edge Detection Comparator 1008. Other circuitry can also be used instead of the potentiometer 1014 to set the Edge Detection Threshold used by the Edge Detection Comparator 1008. For example, a digital-to-analog converter (DAC) can be used instead of the potentiometer 1014. Other variations are possible and within the scope of the embodiments of the present technology.

[0137] Still referring to Figure 10, the output of the amplitude detector 1010 is also shown as being provided to the signal strength determination module 1018, which may be implemented by the controller 712. The signal strength determination module 1018 can be used to monitor the conductive communication quality, which in turn can be used in various different ways, such as testing different combinations of electrodes 115 that can be used to receive conductive communication signals from the LP 102 (or other types of IMDs), and selecting a preferred combination of external electrodes 115 for receiving conductive communication signals from the LP 102 (or other types of IMDs).

[0138] The edge detection outputs generated by the edge detection comparator 1008 (which may also be referred to as edge detections or edge detection triggers) are provided to the message decoder 738, as Figure 10 shown. The message decoder 738 converts the edge detections (received from the edge detection comparator 1008) into bits, each of which can have a "1" bit value or a "0" bit value. Based on the decoded bits, the message decoder 738 can detect the sniff 802 or portions thereof, such as the preamble 810 and the device address 818, as described above with reference to Figure 8A above. Based on the decoded bits, the message decoder 738 can also detect portions of the frame 804 described above with reference to Figure 8B , such as the preamble 810, the device address 818, and one or more segments of the body 822 of the frame 804.

[0139] As described above, Figure 9A an example conductive communication signature 902 for representing a "1" bit value within each of the time windows 912 and 914, and an example conductive communication signature 904 for representing a "0" bit value within another time window 916 are shown, where each of the time windows 912, 914, and 916 has the same duration, such as approximately 30 microseconds, but is not limited thereto. In contrast, Figure 9B shown is the conductive communication signal after the conductive communication signal has been transmitted by the LP 102 through the patient tissue, received by the external device 109, and amplified and filtered by the external device (e.g., using the amplifier 1002, the filter 1004, and optionally also the amplifier 1006). In other words, Figure 9B the shown conductive communication signal shows an example of the conductive communication signal 1007 in Figure 10 , which is provided to the edge detection comparator 1008. Figure 9B Also shown in Figure 10 is an example of the edge detection threshold 922 determined by the controller 712 (or more specifically, its edge detection threshold determination module 1012), and provided to Figure 10The reference input of the edge detection comparator 1008 in

[0140] Now the reference Figure 11A and Figure 11B will be used to outline a method according to certain embodiments of the present technology. More specifically, Figure 11A is a high-level flowchart for outlining a method for determining an edge detection threshold to be used when performing conductive communication according to certain embodiments of the present technology. Figure 11B is a high-level flowchart for outlining a method for using an edge detection threshold to generate an edge detection and decode a received conductive communication signal according to certain embodiments of the present technology. For example, the external device 109 can use such a method to receive and decode a part of the sniff 802 or frame 804 sent by the LP 102 implanted in the patient, where the external device 109 includes or is communicatively coupled to two or more external electrodes 115 that contact the patient's skin. More generally, the external device 109 can use such a method to receive and decode i2e communication. It will also be possible for the LP 102 (or other types of IMDs) to use such a method during i2i communication. In embodiments where the IMD (e.g., 102, 104, 106) performs one or more of the following methods of reference Figure 11A and Figure 11B such an IMD can include a conductive communication receiver similar to the conductive communication receiver 742 described above with reference to Figure 10 and more specifically, can include a message amplifier / filter (similar to Figure 10 740 shown in Figure 10 ), an edge detector comparator (similar to Figure 10 1008 in Figure 10 ), an amplitude detector (similar to Figure 10 1010 in

[0141] Referring to Figure 11A , step 1102 involves measuring the noise baseline of the sensed signal sensed using a sensing vector that includes at least two electrodes (e.g., 115) in contact with the patient. Step 1104 involves determining an edge detection threshold based on the noise baseline measured at step 1102 such that the edge detection threshold is higher than the noise baseline. Briefly returning to the reference Figure 10, according to certain embodiments, the measurement of the noise baseline of the sensed signal at step 1102 can be performed by the controller 712. More specifically, the controller 712 can determine the average or maximum value (also known as the peak value) of a plurality of amplitude measurements (e.g., count values) of the sensed signal generated by the amplitude detector 1010. As described above, the amplitude detector 1010 can be implemented using an ADC. The sensing vector for sensing the sensed signal can be any combination of the external electrodes 115 selected using the switch 713b. In addition, as explained above, before measuring the noise baseline of the sensed signal at step 1102, the sensed signal can be amplified and filtered by the amplifier 1002 and the filter 1004 (and optionally also the amplifier 1006). In certain embodiments, the measurement of the noise baseline is achieved by providing the sensed signal to the ADC after the sensed signal has been amplified and filtered, thereby generating a plurality of ADC count values. Then, the noise baseline can be determined based on one or more of the ADC count values generated using the ADC.

[0142] Then, the controller 712 can perform step 1104 using one or more equations or one or more look-up tables to define an edge detection threshold that is higher than the noise baseline determined at step 1102. Examples of such equations have been described above and thus need not be described again. In an embodiment, the same equation is used to specify the edge detection threshold based on the noise baseline, regardless of the value of the noise baseline. In another embodiment, when the noise baseline is within a first value range, a first equation is used to specify the edge detection threshold based on the noise baseline, and when the noise baseline is within a second value range, a second equation is used to specify the edge detection threshold based on the noise baseline. One or more additional equations can also be used when the noise baseline is within one or more other value ranges, as explained above.

[0143] The noise baseline and the edge detection threshold determined to be greater than the noise baseline can be updated from time to time by the external device 109. In an embodiment, the noise baseline and the edge detection threshold determined to be greater than it are periodically determined by the external device 109 when the external device 109 is not in an active conductive telemetry session (e.g., once per second, once every N seconds, once per cardiac cycle, once every N cardiac cycles, or other time periods). In other words, when the external device 109 is not in an active conductive telemetry session with the LP 102 (or other type of IMD), as referred to above Figure 11AThe described method can be performed periodically by an external device. Additionally, when the external device 109 is in an active conductive telemetry session with the LP 102 (or other type of IMD), the noise baseline and the edge detection threshold determined to be greater than the noise baseline can be updated by the external device 109 after the end of each frame. In other words, when the external device 109 is in an active conductive telemetry session with the LP 102 (or other type of IMD), after the end of each frame (or after the end of every N frames, i.e., after every multiple frames) and before the start of the next frame, the method described above with reference to Figure 11A is performed.

[0144] Now referring to Figure 11B , steps 1106 and 1108 involve generating an edge detection by comparing a sensed signal sensed using a sensing vector with an edge detection threshold (determined at the most recent instance of step 1104), thereby generating a corresponding one of the edge detections when the amplitude of the sensed signal transitions from below the edge detection threshold to above the edge detection threshold. Step 1110 involves decoding a message encoded in the sensed signal based on the edge detection.

[0145] After the controller 712 controls the potentiometer 1014 (or some other circuit, such as a DAC) to provide the (most recently determined) edge detection threshold to the reference input of the edge detection comparator 1008, steps 1106 and 1108 can be performed by the edge detection comparator 1008. Then, the decoding at step 1108 can be performed by the message decoder 738, which can be implemented by the controller 712, as Figure 10 shown.

[0146] Briefly referring back to Figure 9B , the dashed line labeled 922 is an example of the edge detection threshold determined at step 1104 and is thereafter used at steps 1106 and 1108 to generate an edge detection, which is used at step 1110 to decode a message included in the sensed signal based on the edge detection. Still referring to Figure 9B, according to an embodiment, when there are at least a specified number N of edge detections within a time window, a "1" bit value is detected (also referred to as decoded). Examples of time windows are time windows 912, 914, and 916. The specified number N is an integer, which can be, for example, 4, but can alternatively be higher or lower, but at least 2 to prevent transient parasitic noise from being detected as a "1" bit value. In an embodiment, each time window is divided into two or more sub-windows, and when at least one edge is detected in at least two consecutive (or some other number of consecutive) sub-windows, a "1" bit value is detected (also referred to as decoded). For example, a 30 microsecond time window can be divided into up to fifteen 2 microsecond sub-windows, and when at least one edge detection exists in two consecutive 2 microsecond sub-windows, a "1" bit value is detected (also referred to as decoded). Optionally, each time window can be divided into more or fewer than fifteen sub-windows, for example, into five sub-windows, and depending on the specific implementation, when at least one edge detection exists in two (or some other specified number of) consecutive sub-windows, a "1" bit value can be detected.

[0147] In an embodiment, an interrupt is issued in response to a first edge detection within a time window (e.g., a 30 microsecond time window), and an interrupt blanking period is triggered in response to the first edge detection, where the interrupt blanking period has a duration shorter than the time window. For example, in the case where the duration of the time window is 30 microseconds, the interrupt blanking period can be approximately 25 microseconds, or more generally in the range of 18 to 26 microseconds, but not limited thereto. The interrupt generated in response to the first edge detection within the time window can start determining whether a conductive communication signature of a "1" bit value is detected. Thus, during the interrupt blanking period, edge detection is still triggered to determine whether a conductive communication signature of a "1" bit value is detected. The interrupt blanking period can time out, or it can terminate, for example, in response to determining that the first edge detection may be due to noise, etc. A blanking period timer, which can be implemented in hardware, firmware, and / or software, can be used to track the interrupt blanking period.

[0148] Figure 9C Four example time windows 932, 934, 936, and 938 are shown. The initial or first edge detections within each of the windows 932, 934, 936, and 938 are represented by upward-pointing arrows 942, 944, 946, and 948, respectively. Additionally, Figure 9CShows the interrupt blanking period 952 triggered by edge detection represented by arrow 942, the interrupt blanking period 954 triggered by edge detection represented by arrow 944, the interrupt blanking period 956 triggered by edge detection represented by arrow 946, and the interrupt blanking period 958 triggered by edge detection represented by arrow 948. During each interrupt blanking period, bit processing is performed to determine whether a "1" bit value or a "0" bit value is detected within the corresponding window including the interrupt blanking period.

[0149] When the external device 109 is not in an active conductive telemetry session with the LP 102 (i.e., in an inactive conductive telemetry session with the LP 102), but wants to enter an active conductive telemetry session with the LP 102, the external device can monitor (also referred to as search) the sniff 802. As described above, the sniff 802 can also be referred to as a sniff sequence, an advertisement sequence, an advertisement notice, or an advertisement notification. Briefly referring back Figure 8A , in the illustrated embodiment, the sniff 802 includes a preamble 810 known to the external device 109, followed by a device address 818, which can be any one of one or more device addresses known to the external device 109. Now, Figure 12A and Figure 12B The high-level flowcharts of Figure 12A will be used to describe how, according to certain embodiments of the present technology, the external device 109 can use a hierarchical search algorithm to search for the sniff 802. More specifically, Figure 12B is used to describe a first embodiment of the hierarchical search algorithm, and Figure 12B is used to describe a second embodiment of the hierarchical search algorithm. In cases where such algorithms are used to search for the sniff 802, they can be more specifically referred to as hierarchical sniff search algorithms. From the following discussion, it can be understood that such hierarchical sniff search algorithms can be used to check whether one or more initial parts of the sniff sequence are detected before continuing to process the sniff sequence. This allows for a quick restart of the search for a valid sniff sequence while terminating the processing of an invalid sniff sequence. The hierarchical search algorithm can also be used to search for the header 812 of the frame 804.

[0150] First referring to Figure 12A, Step 1202 involves searching for a preamble, where the preamble is a known bit sequence (e.g., a predetermined byte) and thus a known conduction communication signature sequence. For example, the preamble can be the 11001101 bit sequence, but is not limited thereto. At step 1206, it is determined whether the preamble is detected. If the answer to the determination at step 1206 is yes, the process proceeds to step 1210. If the answer to the determination at step 1206 is no, the process returns to step 1202, and the external device 109 restarts the search for the preamble. Assuming that each conduction communication signature corresponding to one bit is transmitted within a 30 microsecond window and the known preamble length is eight bits (i.e., one byte), the external device 109 will spend approximately 240 microseconds (i.e., 30 microseconds * 8 = 240 microseconds) to jointly execute an instance of steps 1202 and 1206. In other words, assuming that each conduction communication signature corresponding to one bit is transmitted within a 30 microsecond window and the known preamble length is 8 bits (i.e., one byte), the external device 109 will spend approximately 240 microseconds to determine whether it has received the preamble 810 of sniffing 802. Thus, continuing with this example, the external device 109 can repeatedly restart the search for sniffing 802 approximately every 240 microseconds until the external device 109 detects the preamble.

[0151] Still referring to Figure 12A , after detecting the preamble of sniffing 802, the external device 109 searches for one of a plurality of possible device addresses in another time window after the time window in which the preamble is detected. At step 1212, it is determined whether a valid device address (i.e., one of a plurality of known device addresses) is detected. If the answer to the determination at step 1212 is yes, the process advances to step 1214, where it is determined that a valid sniffing 802 has been detected. If the answer to the determination at step 1212 is no, the process returns to step 1202, and the external device 109 restarts the search for the preamble. Assuming that each conduction communication signature corresponding to one bit is transmitted within a 30 microsecond window and the length of each known device address is eight bits (i.e., one byte), the external device 109 will spend approximately an additional 240 microseconds to jointly execute an instance of steps 1210 and 1212. In other words, assuming that each conduction communication signature corresponding to one bit is transmitted within a 30 microsecond window and the known device address length is eight bits (i.e., one byte), the external device 109 will spend approximately an additional 240 microseconds to determine whether it has received a valid device address.

[0152] According to an embodiment, assuming that the external device 109 wants to start a conduction telemetry session, once the external device detects a valid sniffing sequence, the external device can send an open link command at step 1216, as Figure 12A shown. Briefly returning to refer to Figure 8B, such an open link command can be included in a segment 824 of the body 822 of a frame 804 that occurs after detecting a valid sniff 802 at an instance of step 1214.

[0153] Reference will now be made below to Figure 12B an alternative to the embodiment described above with reference to Figure 12A Reference Figure 12B , step 1201 involves searching for a first part (e.g., the first half) of a preamble, where the preamble (and thus, its first part) is a known bit sequence (e.g., a predetermined nibble), and thus is a known conductive communication signature sequence. For example, if the preamble is the 11001101 bit sequence, the known first half of the preamble is the 1100 bit sequence. At step 1203, it is determined whether the first part of the preamble has been detected. If the answer at step 1203 is yes, the process proceeds to step 1205. If the answer at step 1203 is no, the process returns to step 1201, and the external device 109 restarts searching for the first part (e.g., the first half) of the preamble. Again assuming that each conductive communication signature corresponding to one bit is transmitted within a 30 microsecond window, and the length of the known first part of the preamble is four bits (i.e., a nibble), the external device 109 will spend approximately 120 microseconds (i.e., 30 microseconds * 4 = 120 microseconds) to jointly execute an instance of steps 1201 and 1203. In other words, assuming that each conductive communication signature corresponding to one bit is transmitted within a 30 microsecond window, and the length of the known first half of the preamble is four bits (i.e., a nibble), the external device 109 will spend approximately 120 microseconds to determine whether it has received the first part of the preamble 810 of the sniff 802. Thus, continuing with this example, the external device 109 can repeatedly restart searching for the sniff 802 approximately every 120 microseconds until the external device 109 detects the preamble, which is half the time taken by the embodiment described above with reference to Figure 12A described.

[0154] Briefly returning to reference Figure 8A , the first part (e.g., the first half) of the preamble 810 is labeled 814, and the second part (e.g., the second half) of the preamble is labeled 816. Again referring to Figure 12B, once the first part (e.g., the first half) 814 of the preamble 810 is detected and the determined answer at step 1203 is yes, the process proceeds to step 1205. Step 1205 involves searching for the second part (e.g., the second half) of the preamble, which is a known sequence of the conductive communication signature. For example, if the preamble is an 11001101 bit sequence, the known second half of the preamble is the 1101 bit sequence. At step 1207, it is determined whether the second part of the preamble is detected. If the determined answer at step 1207 is yes, the process goes to step 1210. If the determined answer at step 1207 is no, the process returns to step 1201, and the external device 109 restarts searching for the first part (e.g., the first half) of the preamble. Steps 1210, 1212, 1214, and 1216 are the same as those in Figure 12A and thus need not be described again.

[0155] Once the external device 109 detects a valid sniff from the LP 102 (or another type of IMD) at an instance of step 1214, the external device 109 can send an open link command to the LP 102. Briefly referring back to Figure 8B , such an open link command is sent within segment 824 of frame 804, where frame 804 includes both header 812 and body 822 and is used for conductive communication between the external device (e.g., 109) and the IMD (e.g., LP 102). Once the open link command is sent by the external device 109 to the LP 102 (or other type of IMD) and received and acknowledged by the LP 102, an active conductive telemetry session is established between the external device 109 and the LP 102 (or other type of IMD). According to some embodiments, during the active telemetry session, it is the LP 102 (or other type of IMD) that sends the header 812, and it is the external device 109 that sends the commands within segment 824. If marker data (aka heart data) is transmitted within the frame, the LP 102 (or other type of IMD) sends the marker data within segment 826. Depending on the type of command included in segment 824, it can be the external device 109 that sends the payload data within segment 828 (e.g., if the command sent by the external device 109 is a write-type command), or the LP 102 (or other type of IMD) that sends the payload data within segment 828 (e.g., if the command sent by the external device 109 is a read-type command).

[0156] Referring to Figure 12A and Figure 12BThe described embodiments can also be used to search for the headers of frames in order to attempt to roughly synchronize or roughly lock the timing of the external device 109 to the timing of the LP 102 (or other types of IMDs). Once the external device 109 detects the header 812 of a frame, it can detect the device address 818 of the frame and then use the various techniques described above to transmit commands, receive marker data (also referred to as cardiac event data), and send or receive payload data at the appropriate time (i.e., within the appropriate time window).

[0157] Although only three external electrodes 115 are shown in many of the above figures, the external device 109 (also referred to as an external medical device (EMD)) can include and / or be communicatively coupled to more than three external electrodes 115. For example, in certain embodiments, the external device 109 includes or is communicatively coupled to seven external electrodes 115. In certain such embodiments, the seven external electrodes 115 are attached to the housing of the external device 109 and include a right front electrode, a right rear electrode, a left front electrode, a left rear electrode, a bottom upper electrode, a bottom middle electrode, and a bottom lower electrode. In Figure 13A , Figure 13B , Figure 13C and Figure 13D examples of the form factor of such an external device 109 are shown, which show a front view, a rear view, a right side view, and a left side view of the external device 109 according to embodiments, respectively. Figures 13A to 13D the external device 109 in Figure 13AAlso shown is a display 716, which is a touchscreen type display and can thus also provide a user interface 718 or at least a part thereof. In some such embodiments, the external device 109 is configured such that, when in use, the patient is supposed to hold the external device 109 by grasping the right front electrode 115a and the right rear electrode 115d with their right hand, grasping the left front electrode 115b and the left rear electrode 115e with their left hand, and resting the bottom of the external device on their lower torso or lower limbs (and more specifically, on the body area below the heart, such as one of their abdomen, their left thigh or right thigh, or one of their left ankle or right ankle), such that each of the bottom upper electrode 115c, the bottom lower electrode 115f, and the bottom middle electrode 115g is in simultaneous skin contact with the patient's lower torso / lower limbs. The right front electrode 115a, the left front electrode 115b, and the bottom upper electrode 115c are used for conductive communication transmission between the external device and one or more IMDs (e.g., one or more LPs). The right rear electrode 115d, the left rear electrode 115e, and the bottom lower electrode 115f are used for conductive communication reception from one or more IMDs (e.g., one or more LPs). The right rear electrode 115d and the left rear electrode 115e are also used for sensing a common mode rejection signal, and the bottom middle electrode 115g is used for injecting the common mode rejection signal into the patient's body. The right rear electrode 115d and the left rear electrode 115e of the external device are also used for sensing an electrocardiogram (ECG) signal. The bottom lower electrode 115f can additionally or alternatively be used, together with one or both of the right rear electrode 115d and the left rear electrode 115e, for sensing the ECG signal and / or sensing the common mode rejection signal. The specific uses of the various electrodes described above can be modified while still remaining within the scope of the embodiments of the present technology described herein. For example, alternatively, the right front electrode 115a, the left front electrode 115b, and the bottom upper electrode 115c can be used by the external device for conductive communication reception from one or more IMDs; and the right rear electrode 115d, the left rear electrode 115e, and the bottom lower electrode 115f can be used for conductive communication transmission between the external device and one or more IMDs. Other variations are possible and are within the scope of the embodiments described herein.

[0158] The right front electrode 115a and the right rear electrode 115d may be referred to herein as the right electrode pair, the left front electrode 115b and the left rear electrode 115e may be referred to herein as the left electrode pair, and the bottom upper electrode 115c and the bottom lower electrode 115f may be referred to herein as the bottom electrode pair. According to some embodiments, the external device 109 is configured to test different combinations of its external electrodes 115 to determine which electrode combination (also known as an electrode vector) provides the best conductive communication quality, and thereafter utilize the combination that provides the best conductive communication quality during a communication session with one or more IMDs (e.g., one or more LPs). For example, a first electrode vector may be between the left and right electrode pairs, a second electrode vector may be between the right and bottom electrode pairs, and a third electrode vector may be between the left and bottom electrode pairs. Continuing the above example, when the first electrode vector is being tested or otherwise used, the right front electrode 115a and the left front electrode 115b are used to send conductive communication pulses from the external device to one or more IMDs (e.g., one or more LPs), and the right rear electrode 115d and the left rear electrode 115e are used to receive conductive communication pulses from one or more IMDs. When the second electrode vector is being tested or otherwise used, the right front electrode 115a and the bottom upper electrode 115c are used to send conductive communication pulses from the external device to one or more IMDs, and the right rear electrode 115d and the bottom lower electrode 115f are used to receive conductive communication pulses from one or more IMDs. When the third electrode vector is being tested or otherwise used, the left front electrode 115b and the bottom upper electrode 115c are used to send conductive communication pulses from the external device to one or more IMDs (e.g., one or more LPs), and the left rear electrode 115e and the bottom lower electrode 115f are used to receive conductive communication pulses from one or more IMDs. (Compared to there being only one right electrode, one left electrode, and one bottom electrode,) the benefit of having the right, left, and bottom electrode pairs is that when a particular electrode vector is being tested or otherwise used, a subset of the external electrodes (e.g., the right front electrode 115a and the left front electrode 115b) can be connected to the conductive communication transmitter 732 via the switch 713, while another subset of the external electrodes (e.g., the right rear electrode 115d and the left rear electrode 115e) can be connected to the conductive communication receiver 742 via the switch 713. However, in alternative embodiments, there may be a single right electrode, a single left electrode, and a single bottom electrode, in which case the switch 713 may need to quickly switch between when a particular subset of electrodes (e.g., a single right electrode and a single left electrode) is connected to the conductive communication transmitter 732 and when the particular subset of electrodes is connected to the conductive communication receiver 742 during the same frame.

[0159] In the above embodiments, the external device may use different combinations of six external electrodes to perform conductive communication with one or more IMDs, where the six external electrodes include a right electrode pair, a left electrode pair, and a bottom electrode pair. Thus, in the above embodiments, three electrode pairs (also referred to as a first electrode pair, a second electrode pair, and a third electrode pair) can be used by the external device to perform conductive communication with one or more IMDs. Within each electrode pair, the external device may use one of these electrodes to send a conductive communication signal to the IMD, and the external device may use the other of these electrodes to receive a conductive communication signal from the IMD. Stated another way, in the above embodiments, the external device may use three external electrodes to send a conductive communication signal to the IMD, and another three external electrodes may be used to receive a conductive communication signal from the IMD. The combination of external electrodes that the external device uses at any given time to attempt to receive a conductive communication signal from the IMD may be referred to as a sensing vector. The combination of external electrodes 115 that the external device 109 uses at any given time to send a conductive communication signal to the IMD may be referred to as a transmission vector. The sensing vector and the transmission vector may generally be referred to as conductive communication vectors, or more simply as communication vectors.

[0160] According to certain embodiments, the exemplary external device 109 described with reference to Figures 13A to 13D may include one or more ports to which two wristbands and an ankle band may be electrically connected. One of the wristbands may be configured to be attached to the patient's right wrist and may include a pair of electrodes that may be used in the same or a similar manner as electrodes 115a and 115d; the other of the wristbands may be configured to be attached to the patient's left wrist and may include a pair of electrodes that may be used in the same or a similar manner as electrodes 115b and 115e; and the ankle band may be configured to be attached to either the patient's left ankle or right ankle and may include three electrodes that may be used in the same or a similar manner as electrodes 115c, 115f, and 115g. Other variations are possible and are within the scope of the embodiments described herein. For example, the wristbands may alternatively be armbands, and / or the ankle band may alternatively be a calf band or a thigh band.

[0161] According to certain embodiments, the exemplary external device 109 described with reference to Figures 13A to 13D may include the various circuits and other components described above with reference to Figure 7 and Figure 10 described.

[0162] One aspect of the technology described herein relates to a method for use by a medical device (e.g., one of 109, 102, 104, or 106) that communicates with another medical device (e.g., another of 109, 102, 104, or 106) using conducted communication, wherein at least one of the medical device or the other medical device is implanted in a patient. The method includes the medical device determining a noise baseline for a sensed signal sensed using a sensing vector including at least two electrodes (e.g., 108, 115) in contact with the patient, determining an edge detection threshold based on the noise baseline such that the edge detection threshold is above the noise baseline, and generating an edge detection by comparing a further sensed signal or a further portion of the sensed signal to the edge detection threshold, thereby generating a corresponding one of the edge detections when the amplitude of the further sensed signal or the further portion of the sensed signal transitions from below the edge detection threshold to above the edge detection threshold.

[0163] In one embodiment, the method further comprises the medical device decoding a message encoded in the further sensed signal or in a further portion of the sensed signal based on the edge detection.

[0164] In one embodiment, a medical device (e.g., 109) is external to the patient, another medical device (e.g., one of 102, 104, or 106) is implanted within the patient, and at least two electrodes (e.g., 115) in contact with the patient include dry electrodes in contact with the patient's skin.

[0165] In one embodiment, the sense signal is amplified and filtered (e.g., by amplifier and / or filter 740) before determining the noise baseline of the sense signal. In this embodiment, determining the noise baseline of the sense signal includes generating a plurality of amplitude values of the sense signal after the sense signal has been amplified and filtered, and determining the noise baseline based on the plurality of amplitude values.

[0166] In one embodiment, determining the noise baseline based on the plurality of amplitude values includes determining the noise baseline to be equal to or based on an average of the plurality of amplitude values.

[0167] In one embodiment, determining the noise floor based on the plurality of amplitude values includes determining the noise floor to be equal to or based on a peak value of the plurality of amplitude values.

[0168] In one embodiment, the amplitude values upon which the noise floor is determined are generated during one or more time periods when the sensed signal includes neither an announcement sequence nor a frame.

[0169] In one embodiment, determining a noise baseline is performed while a medical device and another medical device are participating in an active conductive telemetry session with each other, and the amplitude values on which the noise baseline is determined are generated during one or more time periods in which no conductive communication is taking place between the medical device and the other medical device.

[0170] In one embodiment, determining an edge detection threshold based on the noise baseline includes using the same equation to determine the edge detection threshold based on the noise baseline, regardless of the value of the noise baseline.

[0171] In one embodiment, determining an edge detection threshold based on the noise baseline includes: when the noise baseline is within a first value range, using a first equation to determine the edge detection threshold based on the noise baseline; and when the noise baseline is within a second value range, using a second equation to determine the edge detection threshold based on the noise baseline.

[0172] Another aspect of the technology described herein relates to a medical device (e.g., one of 109, 102, 104, or 106) configured to communicate with another medical device (e.g., another one of 109, 102, 104, or 106) using conductive communication, wherein at least one of the medical device and the other medical device is configured to be implanted in a patient. The medical device includes sensing circuitry (e.g., 120, 740), a controller (e.g., 112, 712), and comparator circuitry (e.g., 1008). The sensing circuitry is configured to generate a sensing signal using a sensing vector that includes at least two electrodes (e.g., 108, 105) configured to contact the patient. The controller is configured to determine a noise baseline of the sensing signal that is sensed using the sensing vector that includes at least two electrodes configured to contact the patient; determine an edge detection threshold based on the noise baseline such that the edge detection threshold is higher than the noise baseline. The comparator circuitry is configured to generate an edge detection by comparing an additional sensing signal or an additional portion of the sensing signal with the edge detection threshold, such that a corresponding one of the edge detections in the edge detection is generated when the amplitude of the additional sensing signal or the additional portion of the sensing signal transitions from being lower than the edge detection threshold to being higher than the edge detection threshold, and the additional sensing signal or the additional portion of the sensing signal is sensed using a sensing vector that includes at least two electrodes in contact with the patient.

[0173] In one embodiment, the controller (e.g., 112, 712) is further configured to decode a message encoded in another sensing signal or another portion of the sensing signal based on the edge detection.

[0174] In one embodiment, a medical device (e.g., 109) is configured to be outside the patient's body, another medical device (e.g., one of 102a, 102b, 104, or 106) is configured to be implanted in the patient's body, and at least two electrodes (e.g., 115) configured to contact the patient include dry electrodes configured to contact the patient's skin.

[0175] In one embodiment, the sensing circuitry is configured to amplify and filter the sensing signal before the controller measures the noise baseline of the sensing signal. In this embodiment, the controller is configured to determine the noise baseline of the sensing signal by: obtaining a plurality of amplitude values of the sensing signal after the sensing signal has been amplified and filtered to determine the noise baseline of the sensing signal, and determining the noise baseline based on the plurality of amplitude values.

[0176] In one embodiment, the controller is configured to determine the noise baseline based on the plurality of amplitude values by determining that the noise baseline is equal to or based on the average of the plurality of amplitude values.

[0177] In one embodiment, the controller is configured to determine the noise baseline based on the plurality of amplitude values by determining that the noise baseline is equal to or based on the peak of the plurality of amplitude values.

[0178] In one embodiment, the controller is configured to cause the amplitude values based on which the noise baseline is determined to be generated during one or more time periods when the sensing signal includes neither a notification sequence nor a frame.

[0179] In one embodiment, when the medical device and another medical device participate in an active conduction telemetry session with each other, the controller is configured to determine the noise baseline by: causing the amplitude values based on which the noise baseline is determined to be generated during one or more time periods when the sensing signal includes neither a notification sequence nor a frame.

[0180] In one embodiment, the controller is configured to use the same equation to determine the edge detection threshold based on the noise baseline, regardless of the value of the noise baseline.

[0181] In one embodiment, the controller is configured to use a first equation to determine the edge detection threshold based on the noise baseline when the noise baseline is within a first value range, and use a second equation to determine the edge detection threshold based on the noise baseline when the noise baseline is within a second value range.

[0182] Another aspect of the present technology described herein relates to a method used by an external device (e.g., 109) that includes or is communicatively coupled to two or more external electrodes (e.g., 115) that contact the skin of a patient in which an IMD (e.g., 102, 104, 106) is implanted. The method provides a hierarchical search of an announcement sequence sent by the IMD, including the external device searching for a known message preamble in a first time window for a sensed signal that is sensed using a sensing vector that includes at least two of the two or more electrodes that contact the patient. The method further includes: the external device, in response to not detecting a known message preamble in the first time window, restarting the search for the known message preamble one or more times until a known message preamble is detected, wherein each time the search for the known message preamble is restarted, a different instance of the first time window is searched. The method further includes the external device, in response to detecting a known message preamble, searching for additional known message portions in a second time window after the first time window in which the preamble was detected. The method further includes the external device, in response to not detecting additional known message portions in the second time window of the sensed signal after the first time window in which the preamble was detected, restarting the search for the known message preamble. Additionally, the method includes the external device sending a command to the IMD in response to detecting a known message preamble and detecting additional known message portions in consecutive instances of the first time window and the second time window, respectively.

[0183] In one embodiment, the known message preamble is a known byte.

[0184] In one embodiment, the additional known message portions searched for in the second time window of the sensed signal include any one of a plurality of known IMD addresses.

[0185] In one embodiment, searching for a known message preamble in a sensing signal within a first time window includes: searching for a known first portion of the known message preamble in a first portion of the first time window; in response to not detecting the known first portion of the known message preamble in the first portion of the first time window, restarting the search for the known first portion of the known message preamble in the first portion of the first time window, wherein each time the search for the known first portion of the message preamble is restarted, a different instance of the first portion of the first time window is searched; in response to detecting the known first portion of the known message preamble, searching for a known second portion of the known message preamble in a second portion of the first time window; in response to not detecting the known second portion of the known message preamble in the second portion of the first time window, restarting the search for the known first portion of the known message preamble in the first portion of the first time window; and in response to detecting the known first and second portions of the known message preamble in consecutive instances of the first and second portions of the first time window, detecting the known message preamble.

[0186] In one embodiment, the known message preamble is a known byte, and the known first portion of the message preamble is the known first nibble of the known byte, and the known second portion of the message preamble is the known second nibble of the known byte.

[0187] In one embodiment, searching for additional known message portions within a second time window of the sensing signal includes any one of a plurality of known IMD addresses.

[0188] In one embodiment, commands sent from an external device to the IMD in response to detecting the known message preamble include one of the following types of commands: an open link command; a keep link active command; a read type command; a write type command; or a close link command.

[0189] In one embodiment, the known message preamble and additional known message portions are part of an announcement sequence that is periodically sent by the IMD using conductive communication when the external device and the IMD are not in an active conductive telemetry session.

[0190] In one embodiment, the known message preamble and additional known message portions are part of the header of a frame sent by the IMD during an active conductive telemetry session between the external device and the IMD.

[0191] In one embodiment, the IMD includes a leadless pacemaker.

[0192] Another aspect of the technology described herein relates to an external device (e.g., 109) configured to communicate with an IMD (e.g., 102, 104, 106) implanted in a patient. The external device includes two or more external electrodes (e.g., 115), a conductive communication receiver (e.g., 742), a conductive communication transmitter (e.g., 732), and a controller (e.g., 712). The two or more external electrodes are configured to be placed in contact with the skin of the patient in which the IMD is implanted. The conductive communication receiver is communicatively coupled (either directly or through a switch) to the two or more external electrodes. The conductive communication transmitter is communicatively coupled to (either directly or through a switch (e.g., 713)) the two or more external electrodes. The controller is communicatively coupled to the conductive communication receiver and the conductive communication transmitter. The controller is configured to use the conductive communication receiver to sense a signal using a sensing vector that includes at least two of the two or more external electrodes, the two or more external electrodes being in contact with the skin of the patient in which the IMD is implanted; search the sensed signal for a known message preamble (e.g., 810) within a first time window; in response to not detecting the known message preamble within the first time window, restart the search for the known message preamble one or more times until the known message preamble is detected, wherein each time the search for the known message preamble is restarted, a different instance of the first time window is searched. The controller is configured to, in response to detecting the known message preamble, search the sensed signal for additional known message portions within a second time window that follows the first time window in which the known preamble was detected. The controller is configured to: in response to not detecting additional known message portions within the second time window of the sensed signal after the first time window in which the preamble was detected, restart the search for the known message preamble. Additionally, the controller is configured to, in response to detecting the known message preamble within consecutive instances of the first time window and detecting additional known message portions within the second time window, use the conductive communication transmitter to send a command (CMD) to the IMD.

[0193] In one embodiment, the known message preamble (e.g., 810) is a known byte.

[0194] In one embodiment, the additional known message portions (e.g., 818) searched for within the second time window of the sensed signal include any one of a plurality of known IMD addresses.

[0195] In one embodiment, to search for a known message preamble in a first time window in a sensed signal, the controller is configured to use a conductive communication receiver (e.g., 742) to: search for a known first part (e.g., 814) of the known message preamble in a first part of the first time window in the sensed signal; in response to not detecting the known first part of the known message preamble in the first part of the first time window, restart the search for the known first part of the known message preamble in the first part of the first time window, wherein each time the search for the known first part of the known message preamble is restarted, a different instance of the first part of the first time window is searched; in response to detecting the known first part (e.g., 814) of the known message preamble, search for a known second part (e.g., 816) of the known message preamble in a second part of the first time window; in response to not detecting the known second part of the known message preamble in the second part of the first time window, restart the search for the known first part of the known message preamble in the first part of the first time window; and detect the known message preamble in response to detecting the known first part and the known second part of the known message preamble in consecutive instances of the first part and the second part of the first time window.

[0196] In one embodiment, the known message preamble (e.g., 810) is a known byte, and the known first part (e.g., 814) of the message preamble is the known first nibble of the known byte, and the known second part (e.g., 816) of the message preamble is the known second nibble of the known byte.

[0197] In one embodiment, additional known message parts (e.g., 818) searched for in a second time window of the sensed signal include any one of a plurality of known IMD addresses.

[0198] In one embodiment, commands sent from an external device to the IMD in response to detecting a known message preamble include one of the following types of commands: open link command; keep link active command; read type command; write type command; or close link command.

[0199] In one embodiment, the known message preamble (e.g., 810) and additional known message parts (e.g., 818) are part of an advertisement sequence (e.g., 802) that is periodically sent by the IMD using conductive communication when the external device and the IMD are not in an active conductive telemetry session.

[0200] In one embodiment, a known message preamble (e.g., 810) and an additional known message portion (e.g., 818) are part of a header (e.g., 812) of a frame (e.g., 804) transmitted by an IMD during an active conductive telemetry session between an external device and the IMD.

[0201] In one embodiment, an IMD configured for communication with an external device includes a leadless pacemaker (e.g., 102).

[0202] Another aspect of the present technology described herein relates to a method for using a frame (e.g., 804) to provide communication between an EMD (e.g., 109) and IMDs (e.g., 102, 104, 106), where the frame includes a header (e.g., 812) and a body (e.g., 822). The method includes the EMD including a command generated by the EMD and a first cyclic redundancy check (CRC) code within a first segment (e.g., 824) of the body of the frame, and the EMD transmitting the first segment of the body of the frame. The method further includes the IMD including heart event data generated by the IMD and a second CRC code within a second segment (e.g., 826) of the body of the frame, and the IMD transmitting the second segment of the body of the frame. Additionally, the method includes one of the EMD and the IMD including payload data generated by one of the EMD and the IMD and a third CRC code within a third segment (e.g., 828) of the body of the frame, and one of the EMD and the IMD transmitting the payload data and the third CRC code. Further, the method includes the IMD receiving the first segment of the body of the frame and determining whether an error exists in the first segment of the body of the frame based on the first CRC code, and the IMD accepting the command included in the first segment in response to determining that the first segment does not include an error, or rejecting the command included in the first segment in response to determining that the first segment includes an error. Additionally, the method includes the EMD receiving the second segment of the body of the frame, and the EMD determining whether an error exists in the second segment of the frame body according to the second CRC code, and the EMD accepting the heart event data included in the second segment in response to determining that the second segment does not include an error, or rejecting the heart event data included in the second segment in response to determining that the second segment includes an error. The method further includes the other of the IMD or the EMD receiving the third segment of the body of the frame, and determining whether an error exists in the third segment of the body of the frame based on the third CRC code, and accepting the payload data included in the third segment in response to determining that the third segment does not include an error, or rejecting the payload data included in the third segment in response to determining that the third segment includes an error. The benefit of each of the first, second, and third segments of the body of the frame including its own respective CRC code is that a device decoding the frame does not need to wait until the end of the frame to determine whether the decoded frame or a portion thereof is valid. Additionally, in the case where each of the first, second, and third segments of the body of the frame includes its own respective CRC code, if an external device is only interested in certain segments of the frame and not in other segments, the external device can utilize the valid segments it receives, even if an error exists in another segment of the same frame.For example, if in response to a read type command, an external device is only interested in the payload data in the third paragraph of the body of the frame received from the IMD, but not in the marker data included in the second paragraph of the body of the frame (or if the payload data is useful independently of the marker data), the external device can separately determine whether the payload data included in the third paragraph is valid based on CRC3 and use the data even if the marker data included in the second paragraph is found to be invalid based on CRC2.

[0203] In one embodiment, the header is generated by the IMD and includes a preamble and a device address.

[0204] In one embodiment, the frame also includes one of ACK or NACK (e.g., 832), which respectively specify whether the payload data written to the IMD is valid as determined based on the third CRC code.

[0205] In one embodiment, in response to the IMD determining that there are no errors in the first paragraph, the IMD accepts and executes the command; and in response to the EMD determining that there are no errors in the second paragraph, the EMD accepts the cardiac event data.

[0206] In one embodiment, in response to determining that there are no errors in the third paragraph, one of the IMD or EMD that does not include the third CRC code in the third paragraph accepts the payload data.

[0207] Another aspect of the technology described herein relates to a system (e.g., 100) including an EMD (e.g., 109) and IMDs (e.g., 102, 104, 106), where the EMD and IMDs are configured to communicate with each other using a frame (e.g., 804) including a header (e.g., 812) and a body (e.g., 822). Each of the EMD and IMDs includes a respective transmitter (e.g., 732, 116), a receiver (e.g., 742, 120), and a controller (712, 112) that controls the transmitter and receiver. The controller of the EMD (e.g., 742) is configured to include a command generated by the EMD and a first CRC code within a first paragraph (e.g., 824) of the body of the frame, and is configured to control the transmitter of the EMD to transmit the first paragraph of the body of the frame. The controller of the IMD (e.g., 112) is configured to include heart event data generated by the IMD and a second CRC code within a second paragraph (e.g., 826) of the body of the frame, and is configured to control the transmitter of the IMD to transmit the second paragraph of the body of the frame. The controller of one of the EMD and IMDs is configured to include payload data generated by one of the EMD and IMDs and a third CRC code within a third paragraph (e.g., 828) of the body of the frame, and is configured to control the transmitter of one of the EMD and IMDs to transmit the third paragraph of the body of the frame. The controller of the IMD is configured to control the receiver of the IMD to receive the first paragraph of the body of the frame, and is configured to determine whether an error exists in the first paragraph of the body of the frame based on the first CRC code, and is configured to accept the command included in the first paragraph in response to determining that the first paragraph does not include an error, or reject the command included in the first paragraph in response to determining that the first paragraph includes an error. The controller of the EMD is configured to control the receiver of the EMD to receive the second paragraph of the body of the frame, and determine whether an error exists in the second paragraph of the body of the frame based on the second CRC code, and is configured to accept the heart event data included in the second paragraph in response to determining that the second paragraph does not include an error, or reject the heart event data included in the second paragraph in response to determining that the second paragraph includes an error. The controller of the other of the IMD or EMD is configured to control the receiver of the other of the IMD or EMD to receive the third paragraph of the body of the frame, and determine whether an error exists in the third paragraph of the body of the frame based on the third CRC code, and accept the payload data included in the third paragraph in response to determining that the third paragraph does not include an error, or reject the payload data included in the third paragraph in response to determining that the third paragraph includes an error.

[0208] In one embodiment, the controller of the IMD is configured to generate a header that includes a preamble and a device address.

[0209] In one embodiment, the controller of the IMD is further configured to include one of ACK or NACK (e.g., 832), which respectively specify whether the payload data written to the IMD is valid, as determined based on the third CRC code.

[0210] In one embodiment, the controller of the IMD is configured to accept and execute a command in response to determining that there are no errors in the first paragraph; and the controller of the EMD is configured to accept cardiac event data in response to determining that there are no errors in the second paragraph.

[0211] In one embodiment, the controller of one of the IMD or EMD that does not include the third CRC code in the third paragraph is configured to accept the payload data in response to determining that there are no errors in the third paragraph of the body of the frame.

[0212] In one embodiment, the EMD and the IMD are configured to communicate with each other using conductive communication. The respective receivers of each of the EMD and the IMD include respective conductive communication receivers, and the respective transmitters of each of the EMD and the IMD include respective conductive communication transmitters.

[0213] In one embodiment, the EMD and the IMD are configured to communicate with each other using conductive communication.

[0214] As referenced above Figure 12A and Figure 12B an external device (e.g., 109) that implements a hierarchical search of the announcement sequence sent by the IMD, as described above, may also optionally be used to implement one or other embodiments described herein, such as an embodiment involving determining an edge detection threshold based on a noise baseline such that the edge detection threshold is higher than the noise baseline, as referenced above Figure 11A and Figure 11B described. Such an external device (e.g., 109) may also additionally or alternatively be used to implement embodiments in which the first, second, and third paragraphs of the frame include respective first, second, and third CRC codes, as referenced above Figure 8B and Figure 8C described in more detail.

[0215] An external device (e.g., 109) that implements an embodiment involving determining an edge detection threshold based on a noise baseline such that the edge detection threshold is higher than the noise baseline, as referenced above Figure 11A and Figure 11B described, may also optionally be used to implement embodiments in which the first, second, and third paragraphs of the frame include respective first, second, and third CRC codes, as referenced above Figure 8B and Figure 8Cdescribed in more detail. Such an external device can also be used, additionally or alternatively, to implement a hierarchical search of the notification sequences sent by the IMD, as described above with reference to Figure 12A and Figure 12B .

[0216] As described above with reference to Figure 11A and Figure 11B the embodiments related to determining an edge detection threshold above a noise baseline can optionally be combined with a hierarchical search of the notification (also known as sniffing) sequences sent by the IMD, as described above with reference to Figure 12A and Figure 12B . For one example, an edge detection threshold determined based on the noise baseline (such that the edge detection threshold is above the noise baseline) can be used to detect notification sequences according to the hierarchical search embodiments described in reference Figure 12A and Figure 12B . A specific example of how such embodiments can be used in combination is shown in the flowchart of Figure 14 . Figure 14 Steps that are the same or similar to those already referenced above in Figure 11A , Figure 11B , Figure 12A and / or Figure 12B are numbered the same or similarly and need not be described in detail again. Referring to Figure 14 , step 1102 involves an external device (e.g., 109) measuring the noise baseline of a sensed signal that is sensed using a sensing vector that includes at least two electrodes (e.g., 115) in contact with the patient, and step 1104 involves the external device determining an edge detection threshold based on the noise baseline measured at step 1102 such that the edge detection threshold is above the noise baseline. In some embodiments, steps 1102 and 1104 are performed by the external device when it is not in an active conductive telemetry session with the IMD (e.g., LP 102). Still referring to Figure 14 , as part of performing a hierarchical search of the notification (also known as sniffing) sequences (using the embodiments of Figure 12A or Figure 12B ), step 1406 involves comparing the sensed signal (sensed using the sensing vector) with the edge detection threshold determined at step 1104 (the same or similar as done in step 1106 in Figure 11B ), and step 1408 involves generating an edge detection when attempting to establish an active conductive telemetry session with the IMD (e.g., LP102) when the amplitude of the sensed signal transitions from below the edge detection threshold to above the edge detection threshold (the same or similar as done in step 1108 in Figure 11B ). Still referring to Figure 14, step 1414 involves, as part of performing a hierarchical search on an announcement (also known as sniffing) sequence (using Figure 12A or Figure 12B embodiments), decoding messages in the sensed signal based on edge detection (as done in step 1110 in Figure 11B ) to detect a valid announcement (also known as sniffing) sequence (the same or similar to what is done in step 1214 in Figure 11B ). The external device (e.g., 109) then sends an open link command to the IMD at step 1216, thereby establishing an active conductive telemetry session with the IMD. Thereafter, when the external device and the IMD are participating in an active conductive telemetry session, as shown in step 1418, embodiments in which the first, second, and third segments of a frame include corresponding first, second, and third CRC codes can optionally be used, as described in more detail above with reference to Figure 8B and Figure 8C . More generally, embodiments related to determining an edge detection threshold above a noise baseline, as described above with reference to Figure 11A and Figure 11B , can optionally be used in combination with a hierarchical search of an announcement (also known as sniffing) sequence sent by the IMD, as described above with reference to Figure 12A and Figure 12B , and / or can optionally be used in combination with embodiments in which the first, second, and third segments of a frame include corresponding first, second, and third CRC codes, as described in more detail above with reference to Figure 8B and Figure 8C . The controller (e.g., 712) of the external device (e.g., 109) can be configured to perform such combined embodiments. For example, an external device (e.g., 109) implementing embodiments related to determining an edge detection threshold based on a noise baseline such that the edge detection threshold is above the noise baseline, as described above with reference to Figure 11A and Figure 11B , can also optionally be used to implement a hierarchical search of an announcement (also known as sniffing) sequence sent by the IMD, as described above with reference to Figure 12A and Figure 12B , and / or can also optionally be used to implement embodiments in which the first, second, and third segments of a frame include corresponding first, second, and third CRC codes, as described in more detail above with reference to Figure 8B and Figure 8C .

[0217] As described above with reference to Figure 11A and Figure 11BThe embodiments related to determining an edge detection threshold above a noise baseline may optionally be used in combination with embodiments in which a first segment, a second segment, and a third segment of a frame include a corresponding first CRC code, a second CRC code, and a third CRC code, as described in more detail above with reference to Figure 8B and Figure 8C For one example, an edge detection threshold determined based on the noise baseline (such that the edge detection threshold is above the noise baseline) may be used to detect the first segment, the second segment, and the third segment of a frame that includes a corresponding first CRC code, a second CRC code, and a third CRC code, as described in more detail above with reference to Figure 8B and Figure 8C wherein portions of the frame that are error - free may be used even if one or more other portions of the frame include errors. Referring to Figure 14 , in a specific example, such a combination of embodiments may include steps 1102 and 1104, followed by step 1418 (where steps 1406, 1408, 1414, and 1216 are not performed, or optionally are performed). A controller (e.g., 712) of an external device (e.g., 109) may be configured to perform such a combined embodiment. For example, an external device (e.g., 109) implementing an embodiment involving determining an edge detection threshold based on a noise baseline such that the edge detection threshold is above the noise baseline, as described in more detail above with reference to Figure 11A and Figure 11B may also optionally be used to implement embodiments in which a first segment, a second segment, and a third segment of a frame include a corresponding first CRC code, a second CRC code, and a third CRC code, as described in more detail above with reference to Figure 8B and Figure 8C More detailed description.

[0218] As described in more detail above with reference to Figure 12A and Figure 12B embodiments involving performing a hierarchical search on an advertisement (also referred to as sniffing) sequence sent by an IMD may also optionally be used in combination with embodiments in which a first segment, a second segment, and a third segment of a frame include a corresponding first CRC code, a second CRC code, and a third CRC code, as described in more detail above with reference to Figure 8B and Figure 8C For example, the hierarchical search described above with reference to Figure 12A and Figure 12B may be used to detect an advertisement (also referred to as sniffing) sequence, and thereafter when an active conductive telemetry session is established, a frame including a corresponding first CRC code, a second CRC code, and a third CRC code, as described in more detail above with reference to Figure 8B and Figure 8C may be used for conductive communication between an external device (e.g., 109) and an IMD (e.g., LP 102). Referring to Figure 14, in a specific example, this combination of embodiments may include steps 1406, 1408, 1414, 1216, and 1418 performed in that order (where steps 1102 and 1104 are not performed, or are optionally performed). A controller (e.g., 712) of an external device (e.g., 109) may be configured to perform such a combined embodiment. For example, as described above with reference to Figure 12A and Figure 12B , an external device (e.g., 109) implementing embodiments related to performing a hierarchical search on an announcement (also referred to as sniffing) sequence sent by an IMD may also optionally be used to implement embodiments in which the first, second, and third segments of a frame include respective first, second, and third CRC codes, as described in more detail above with reference to Figure 8B and Figure 8C .

[0219] More generally, the various embodiments of the present technology described herein may be used alone, or optionally in combination with one or more other embodiments of the present technology described herein.

[0220] It should be understood that the subject matter described herein is not limited in its application to the construction details and component arrangements set forth in the description herein or shown in its drawings. The subject matter described herein is capable of having other embodiments and of being practiced or carried out in various ways. Additionally, it should be understood that the language and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of "including", "comprising", or "having" and their variants herein is intended to cover the items listed thereafter and their equivalents as well as additional items. Further, it should be noted that unless otherwise stated, the term "based on" as used herein should be interpreted to mean at least in part based on, meaning that one or more additional factors may exist in making a decision, etc. For example, if a decision is based on the result of a comparison, then in addition to being based on the result of the comparison, the decision may also be based on one or more other factors.

[0221] The embodiments have been described above by means of functional building blocks that illustrate the performance of specified functions and their relationships. For ease of description, the boundaries of these functional building blocks are generally defined herein. Alternative boundaries may be defined as long as the specified functions and their relationships are appropriately performed. Accordingly, any such alternative boundaries are within the scope and spirit of the claimed invention. For example, some steps shown in the various flowcharts may be combined or separated. Also, only a subset of the steps shown in the various flowcharts may be performed. For another example, the boundaries of some block diagrams may be changed.

[0222] It should be understood that the above description is intended to be illustrative and not restrictive. For example, the above embodiments (and / or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the embodiments without departing from the scope of the present invention. Although the dimensions and types of the materials and coatings described herein are intended to define the parameters of the embodiments of the present technology, they are in no way restrictive but are exemplary embodiments. After reading the above description, many other embodiments will be apparent to those skilled in the art. Therefore, the scope of the embodiments of the present technology should be determined with reference to the appended claims and the full scope of equivalents given by those claims. In the appended claims, the terms "including" and "in which" are used as plain English equivalents of the corresponding terms "comprising" and "wherein". In addition, in the appended claims, the terms "first", "second", "third", etc. are used only as labels and are not intended to impose numerical requirements on their objects.

Claims

1. A medical device configured to communicate with another medical device using conductive communication, wherein, At least one of the medical device and the other medical device is configured to be implanted in a patient, and the medical device includes: A sensing circuit system configured to generate a sensing signal using a sensing vector, the sensing vector including at least two electrodes configured to contact the patient; A controller configured to: Determine a noise baseline of the sensing signal, the sensing signal being sensed using the sensing vector, the sensing vector including at least two electrodes configured to contact the patient; and Determine an edge detection threshold based on the noise baseline such that the edge detection threshold is higher than the noise baseline; and A comparator circuit system configured to generate an edge detection by comparing an additional sensing signal or an additional portion of the sensing signal with the edge detection threshold, thereby generating a corresponding one of the edge detections in the edge detection when the amplitude of the additional sensing signal or the additional portion of the sensing signal changes from being lower than the edge detection threshold to being higher than the edge detection threshold, the additional sensing signal or the additional portion of the sensing signal being sensed using the sensing vector including the at least two electrodes contacting the patient.

2. The medical device according to claim 1, wherein, The controller is further configured to decode a message encoded in the additional sensing signal or the additional portion of the sensing signal based on the edge detection.

3. The medical device according to claim 1, wherein: The medical device is configured to be outside the patient; The other medical device is configured to be implanted in the patient; And The at least two electrodes configured to contact the patient include dry electrodes configured to contact the skin of the patient.

4. The medical device according to any one of claims 1 to 3, wherein: The sensing circuit system is configured to amplify and filter the sensing signal before the controller measures the noise baseline of the sensing signal; And The controller is configured to determine the noise baseline of the sensing signal by: obtaining a plurality of amplitude values of the sensing signal after the sensing signal has been amplified and filtered, and determining the noise baseline based on the plurality of amplitude values.

5. The medical device according to claim 4, wherein, The controller is configured to determine the noise baseline based on the plurality of amplitude values by determining that the noise baseline is equal to or based on an average of the plurality of amplitude values.

6. The medical device according to claim 4, wherein, The controller is configured to determine the noise baseline based on the plurality of amplitude values by determining that the noise baseline is equal to or based on a peak of the plurality of amplitude values.

7. The medical device according to claim 4, wherein, The controller is configured to cause the amplitude values based on which the noise baseline is determined to be generated during one or more time periods when the sensing signal includes neither a notification sequence nor a frame.

8. The medical device according to claim 4, wherein, The controller is configured to determine the noise baseline as follows when the medical device and the other medical device are participating in an active conductive telemetry session with each other: such that the amplitude values on which the determination of the noise baseline is based are generated during one or more time periods when no conductive communication is taking place between the medical device and the other medical device.

9. The medical device according to any one of claims 1 to 3, wherein, The controller is configured to use the same equation to determine the edge detection threshold based on the noise baseline, regardless of the value of the noise baseline.

10. The medical device according to any one of claims 1 to 3, wherein, The controller is configured to, when the noise baseline is within a first value range, use a first equation to determine the edge detection threshold based on the noise baseline, and when the noise baseline is within a second value range, use a second equation to determine the edge detection threshold based on the noise baseline.

11. A method used by a medical device that communicates with another medical device using conductive communication, wherein, At least one of the medical device or the other medical device is configured to be implanted in a patient, and the method includes the medical device: Determining a noise baseline of a sensed signal, the sensed signal being sensed using a sensing vector that includes at least two electrodes in contact with the patient; Determining an edge detection threshold based on the noise baseline such that the edge detection threshold is higher than the noise baseline; and Generating an edge detection by comparing an additional sensed signal or an additional portion of the sensed signal with the edge detection threshold, such that a corresponding edge detection in the edge detection is generated when the amplitude of the additional sensed signal or the additional portion of the sensed signal transitions from being lower than the edge detection threshold to being higher than the edge detection threshold, the additional sensed signal or the additional portion of the sensed signal being sensed using the sensing vector that includes the at least two electrodes in contact with the patient.

12. The method according to claim 11, further including the medical device decoding a message encoded in the additional sensed signal or the additional portion of the sensed signal based on the edge detection.

13. The method according to claim 11, wherein: The medical device is configured to be outside the patient; The other medical device is configured to be implanted in the patient; and The at least two electrodes in contact with the patient include dry electrodes in contact with the patient's skin.

14. The method according to any one of claims 11 to 13, wherein: Before determining the noise baseline of the sensed signal, amplifying and filtering the sensed signal; and The determining the noise baseline of the sensed signal includes: after the sensed signal has been amplified and filtered, generating a plurality of amplitude values of the sensed signal and determining the noise baseline based on the plurality of amplitude values.

15. The method according to claim 14, wherein, The determining the noise baseline based on the plurality of amplitude values includes: determining that the noise baseline is equal to or based on the average of the plurality of amplitude values.

16. The method according to claim 14, wherein, The determining the noise baseline based on the plurality of amplitude values includes: determining that the noise baseline is equal to or based on the peak of the plurality of amplitude values.

17. The method according to claim 14, wherein: The amplitude value based on which the noise baseline is determined is generated during one or more time periods when the sensed signal includes neither an announcement sequence nor a frame.

18. The method according to claim 14, wherein: the determination of the noise baseline is performed while the medical device and the other medical device are participating in an active conduction telemetry session with each other; and the amplitude value based on which the noise baseline is determined is generated during one or more time periods when frame conduction communication is not being performed between the medical device and the other medical device.

19. The method according to any one of claims 11 to 13, wherein, Determining the edge detection threshold based on the noise baseline includes: using the same equation to determine the edge detection threshold based on the noise baseline, regardless of the value of the noise baseline.

20. The method according to any one of claims 11 to 13, wherein Determining the edge detection threshold based on the noise baseline includes: when the noise baseline is within a first value range, using a first equation to determine the edge detection threshold based on the noise baseline; and when the noise baseline is within a second value range, using a second equation to determine the edge detection threshold based on the noise baseline.

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