Patent Application
20240350812
Embodiments described herein generally relate to methods, devices, and systems for providing and improving communication between implantable medical devices, one or more of which may be a leadless pacemaker.
Implantable medical devices (IMDs) and systems often rely on proper communication to operate correctly. For example, in a dual chamber leadless pacemaker system, implant-to-implant (i2i) communication between two or more leadless pacemakers (LPs) is critical for proper synchronization and operation of the system. The LPs can communicate with one another using conductive communication, or using i2i radio frequency (RF) communication. Conductive communication involves transmitting and receiving communication signals through patient tissue, typically using the same electrodes that are used for cardiac pacing and sensing, wherein the transmitted communication signals include pulses that can be produced using the same pulse generator that is used to produce pacing pulses. RF communication, by contrast, involves using an antenna for transmitting and receiving RF communication signals. Conductive communication, which is also known as conducted communication, or galvanic communication, is much more energy efficient than RF communication. Accordingly, the longevity of a dual chamber LP system that utilizes conducted communication for i2i communication is greater than the longevity of a dual chamber LP system that utilizes RF communication for i2i communication. However, one potential problem with relying on conducted communication for i2i communication between LPs, between an LP and another type of implantable medical device (IMD), or more generally between IMDs, is that conducted communication may be adversely affected by noise from a magnetic resonance imaging (MRI) system, or some other noise source. Accordingly, it is sometimes the case the LPs and/or other IMDs are switched into an MRI safe-mode when exposed to an MRI system, during which the LPs and/or other IMDs no longer communicate with one another. For example, a dual chamber LP system may switch from a DOO mode to a VOO mode if it is known that the LPs are about to be exposed to an MRI scan, or in response to a noise reversion trigger.
Certain embodiments of the present technology are related to methods for use with a system including a first implantable medical device (IMD) and a second IMD that are remotely located relative to one another and are capable of communicating with one another using conductive communication. Such a method can include the first IMD using normal conductive communication to transmit one or more messages intended for the second IMD, during a first period of time that a first trigger event is not detected. The method can also include the first IMD detecting the first trigger event, and in response thereto, the first IMD starting a timer or counter and transitioning to using boosted conductive communication to transmit one or more messages intended for the second IMD during a second period of time. The method can further include the first IMD either detecting a second trigger event, or detecting based on the timer or counter that a specified amount of time or cardiac cycles elapsed since the timer or counter was started, and in response thereto the first IMD transitioning back to using normal conductive communication to transmit one or more messages intended for the second IMD during a third period of time. In the method summarized above, individual conductive communication pulses included in the one or more messages transmitted using boosted conductive communication during the second period of time have greater energy than respective individual conductive communication pulses including in the one or more messages transmitted using normal conductive communication during the first and the third periods of time.
In accordance with certain embodiments, the method further includes the first IMD decoding, during the second period of time, at least a threshold number of invalid messages within a same cardiac cycle, and in response thereto, the first IMD at least one of disabling transmitting of messages to the second IMD or disabling monitoring for messages from the second IMD for a further specified amount of time or cardiac cycles.
In accordance with certain embodiments, the method further includes, after the at least one of disabling transmitting of messages to the second IMD or disabling monitoring for messages from the second IMD for the further specified amount of time or cardiac cycles, the first IMD returning to using the boosted conductive communication to transmit one or more messages intended for the second IMD during the second period of time, until either detecting the second trigger event or detecting based on the timer or counter that the further specified amount of time or cardiac cycles elapsed since the first IMD started the timer or counter.
In accordance with certain embodiments, the first IMD detecting the first trigger event comprises the first IMD decoding at least a threshold number of invalid messages within a same cardiac cycle during the first period of time, and in response thereto, the first IMD starting the timer or counter and transitioning to using the boosted conductive communication to transmit one or more messages intended for the second IMD during the second period of time.
In accordance with certain embodiments, the first trigger event comprises at least one of an arrhythmia being detected or arrhythmia therapy being delivered; and the second trigger event comprises at least one of the arrhythmia no longer being detected or the arrhythmia therapy being completed.
In accordance with certain embodiments, the first trigger event comprises the first IMD determining that the second IMD did not successfully receive one or more of the messages, intended for the second IMD, that the first IMD transmitted using conductive communication.
In accordance with certain embodiments, the system with which the method is for use further comprises a third IMD, and the method further includes the first IMD storing, and dynamically updating over time, information that specifies for each IMD of the first, second and third IMDs whether normal conductive communication or boosted conductive communication is being used by the IMD for transmitting messages to other ones of the IMDs. Alternatively, the method includes each IMD of the first, second, and third IMDs separately storing and dynamically updating over time its own respective information that specifies for itself and for the other IMDs whether normal conductive communication or boosted conductive communication is being used for transmitting messages to other ones of the IMDs.
Certain embodiments of the present technology are directed to an IMD configured to communicate with another IMD that is remotely located relative to the IMD, wherein the IMD comprises at least two electrodes, a conductive communication transceiver coupled to the at least two electrodes and configured to selectively transmit conductive communication messages that are intended for the other IMD, and configured to receive conductive communication messages from the other IMD. Additionally, the IMD includes a controller configured to control the conductive communication transceiver to use normal conductive communication to transmit one or more messages intended for the other IMD, during a first period of time that a first trigger event is not detected. The controller is also configured to detect the first trigger event, and in response thereto, start a timer or counter and control the conductive communication transceiver to transition to using boosted conductive communication to transmit one or more messages intended for the other IMD during a second period of time. Additionally, the controller is configured to detect a second trigger event, or detect based on the timer or counter that a specified amount of time or cardiac cycles elapsed since the timer or counter was started, and in response thereto control the conductive communication transceiver to transition back to using normal conductive communication to transmit one or more messages intended for the other IMD during a third period of time. Individual conductive communication pulses included in the one or more messages transmitted using boosted conductive communication during the second period of time have greater energy than respective individual conductive communication pulses including in the one or more messages transmitted using normal conductive communication during the first and the third periods of time.
In accordance with certain embodiments, the controller is further configured to decode, during the second period of time, at least a threshold number of invalid messages within a same cardiac cycle, and in response thereto, disable the conductive communication transceiver for a further specified amount of time or cardiac cycles.
In accordance with certain embodiments, the controller is further configured to, after the conductive communication transceiver has been disabled for the further specified amount of time or cardiac cycles, control the conductive communication transceiver to return to using the boosted conductive communication to transmit one or more messages intended for the other IMD during the second period of time, until either the second trigger event is detected or the timer or counter is used to detect that the further specified amount of time or cardiac cycles elapsed since the IMD started the timer or counter.
In accordance with certain embodiments, the first trigger event comprises the IMD decoding at least a threshold number of invalid messages within a same cardiac cycle during the first period of time, and in response thereto, the controller is configured to start the timer or counter and transition to using the boosted conductive communication to transmit one or more messages intended for the other IMD during the second period of time.
In accordance with certain embodiments, the first trigger event comprises at least one of an arrhythmia being detected or arrhythmia therapy being delivered; and the second trigger event comprises at least one of the arrhythmia no longer being detected or the arrhythmia therapy being completed.
In accordance with certain embodiments, the first trigger event comprises the IMD determining that the other IMD did not successfully receive one or more of the messages, intended for the other IMD, that the IMD transmitted using conductive communication.
In accordance with certain embodiments, the IMD is configured to communicate with a plurality of other IMDs, and the controller of the IMD is further configured to store in memory of the IMD, and dynamically update over time, information that separately specifies for the IMD and each of the other IMDs whether normal conductive communication or boosted conductive communication is being used for transmitting messages.
Certain embodiments of the present technology are directed to methods for use with a system including a first IMD and a second IMD that are remotely located relative to one another and are capable of communicating with one another using conductive communication and RF communication. Such a method can includes the first IMD using normal conductive communication to transmit one or more messages intended for the second IMD, during a first period of time that a first trigger event is not detected. The method can also include the first IMD detecting the first trigger event, and in response thereto, the first IMD starting a timer or counter and transitioning to using boosted conductive communication to transmit one or more messages intended for the second IMD during a second period of time. Additionally, the method can include the first IMD detecting based on the timer or counter that a specified amount of time or cardiac cycles elapsed since the timer or counter was started without a second trigger event being detected, and in response thereto the first IMD using RF communication to transmit one or more messages intended for the second IMD during a third period of time.
In accordance with certain embodiments, the method further includes the first IMD also using boosted conductive communication to transmit one or more messages intended for the second IMD during the second period of time, such that during the second period of time both RF communication and boosted conductive communication are used by the first IMD.
In accordance with certain embodiments, the method further includes after the first IMD started using RF communication to transmit one or more messages intended for the second IMD, the first IMD detecting the second trigger event and in response thereto stopping using RF communication and transitioning to using one of the normal conductive communication or the boosted conductive communication to transmit one or more messages intended for the second IMD during a fourth period of time.
In accordance with certain embodiments, the method further includes, after the first IMD started using RF communication to transmit one or more messages intended for the second IMD, the first IMD detecting the second trigger event and in response thereto stopping using RF communication and transitioning to using one of the normal conductive communication or the boosted conductive communication to transmit one or more messages intended for the second IMD during a fourth period of time.
In accordance with certain embodiments, the system with which the method is for use further comprises a third IMD, and the method further includes the first IMD storing and dynamically updating information that specifies, for each IMD of the first, second and third IMDs, whether the normal conductive communication, the boosted conductive communication, or the RF communication is being used for transmitting messages. Alternatively, each IMD of the first, second, and third IMDs storing and dynamically updating its own respective information that specifies for itself and for the other IMDs whether the normal conductive communication, the boosted conductive communication, or the RF communication is being used for transmitting messages.
Certain embodiments of the present technology are directed to an IMD configured to communicate with another IMD that is remotely located relative to the IMD, wherein the IMD includes at least two electrodes and a conductive communication transceiver coupled to the at least two electrodes and configured to selectively transmit conductive communication messages that are intended for the other IMD, and configured to receive conductive communication messages from the other IMD. The IMD also includes an antenna and an RF communication transceiver coupled to the antenna and configured to selectively transmit RF communication messages that are intended for the other IMD, and configured to receive RF communication messages from the other IMD. The IMD also includes a controller configured to control the conductive communication transceiver to use normal conductive communication to transmit one or more messages intended for the other IMD, during a first period of time that a first trigger event is not detected. The controller of the IMD is also configured to detect the first trigger event, and in response thereto, start a timer or counter and control the conductive communication transceiver to transition to using boosted conductive communication to transmit one or more messages intended for the other IMD during a second period of time. Additionally, the controller of the IMD is configured to detect based on the timer or counter that a specified amount of time or cardiac cycles elapsed since the timer or counter was started without a second trigger event being detected, and in response thereto control the RF communication transceiver to transmit one or more RF communication messages intended for the other IMD during a third period of time.
In accordance with certain embodiments, the controller is also configured to control the conductive communication transceiver to also use boosted conductive communication to transmit one or more messages intended for the other IMD during the second period of time, such that during the second period of time both the RF communication and the boosted conductive communication are used by the IMD.
In accordance with certain embodiments, after the controller controls the RF communication transceiver to transmit one or more RF communication messages intended for the other IMD, the controller is also configured to detect the second trigger event and in response thereto disable the RF communication transceiver and control the conductive communication transceiver to use one of the normal conductive communication or the boosted conductive communication to transmit one or more messages intended for the other IMD during a fourth period of time.
In accordance with certain embodiments, the IMD is configured to communicate with a plurality of other IMDs, and the controller of the IMD is further configured to store in memory of the IMD, and dynamically update over time, information that separately specifies for the IMD and each of the other IMDs whether the normal conductive communication, the boosted conductive communication, or the RF communication is being used for transmitting messages.
This summary is not intended to be a complete description of the embodiments of the present technology. Other features and advantages of the embodiments of the present technology will appear from the following description in which the preferred embodiments have been set forth in detail, in conjunction with the accompanying drawings and claims.
Embodiments of the present technology relating to both structure and method of operation may best be understood by referring to the following description and accompanying drawings, in which similar reference characters denote similar elements throughout the several views:
Certain embodiments of the present technology related to implantable medical devices (IMDs), and methods for use therewith, that improve implant-to-implant (i2i) communication between the IMDs, one or more of which may be a leadless pacemaker (LP). Before providing additional details of the specific embodiments of the present technology mentioned above, an example system in which embodiments of the present technology can be used will first be described with reference to
In certain embodiments, LPs 102a and 102b communicate with one another, and/or with an ICD 106, by conductive communication through the same electrodes that are used for sensing and/or delivery of pacing therapy. The LPs 102a and 102b may also be able to use conductive communication to communicate with an external device, e.g., a programmer 109, having electrodes placed on the skin of a patient within with the LPs 102a and 102b are implanted. The LPs 102a and 102b can each also include an antenna that would enable them to communicate with one another, the ICD 106 and/or an external device using RF communication. While only two LPs are shown in
In some embodiments, one or more LP 102 can be co-implanted with the ICD 106. 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 cardiac chamber, for bidirectional conductive communication with one another, with the programmer 109, and the ICD 106.
While the methods, devices and systems described herein include examples primarily in the context of LPs, it is understood that the methods, devices and systems described herein may be utilized with various other types of IMDs. In other words, the methods, devices and systems may be used to improve communication between various IMDs implanted in a human, not just LPs. For examples, such embodiments can be used to improve communications between at least two LPs, between an LP and an NV-ICD, between an LP and an ICM, between an ICM and an S-ICD, but are not limited thereto. It should also be understood that the embodiments described herein can be used to improve communication between more than two IMDs, and are not limited to communication between just first and second IMDs. The methods, devices and systems may also be used to improve communication between two or more IMDs implanted within the same cardiac chamber that may be the same type of IMD or may be different types of IMDs. The methods, devices and systems may also be used to improve communication between two or more IMDs in a system including at least one IMD that is not implanted within a cardiac chamber, but rather, is implanted epicardially, transmurally, intravascularly (e.g., coronary sinus), or subcutaneously (e.g., S-ICD), etc.
Referring to
In
The receivers 120 and 122 can also be referred to, respectively, as a low frequency (LF) receiver 120 and a high frequency (HF) receiver 122, because the receiver 120 is configured to monitor for one or more signals within a relatively low frequency range (e.g., below 100 KHz) and the receiver 122 is configured to monitor for one or more signals within a relatively high frequency range (e.g., above 100 KHz). In certain embodiments, the receiver 120 (and more specifically, at least a portion thereof) is always enabled and monitoring for a wakeup notice, which can simply be a wakeup pulse, within a specific low frequency range (e.g., between 1 KHz and 100 KHz); and the receiver 122 is selectively enabled by the receiver 120. The receiver 120 is configured to consume less power than the receiver 122 when both the first and second receivers are enabled. Accordingly, the receiver 120 can also be referred to as a low power receiver 120, and the receiver 122 can also be referred to as a high power receiver 122. The low power receiver 120 is incapable of receiving signals within the relatively high frequency range (e.g., above 100 KHz), but consumes significantly less power than the high power receiver 122. This way the low power receiver 120 is capable of always monitoring for a wakeup notice without significantly depleting the battery (e.g., 114) of the LP. In accordance with certain embodiments, the high power receiver 122 is selectively enabled by the low power receiver 120, in response to the low power receiver 120 receiving a wakeup notice, so that the high power receiver 122 can receive the higher frequency signals, and thereby handle higher data throughput needed for effective i2i communication without unnecessarily and rapidly depleting the battery of the LP (which the high power receiver 122 may do if it were always enabled).
Since the receivers 120, 122 are used to receive conductive communication messages, the receivers 120, 122 can also be referred to as conductive communication receivers. In certain embodiments, each of the LPs 102 includes only a single conductive communication receiver.
In accordance with certain embodiments, when one of the LPs 102a and 102b senses an intrinsic event or delivers a paced event, the corresponding LP 102a, 102b transmits an implant event message to the other LP 102a, 102b. For example, when an atrial LP 102a senses/paces an atrial event, the atrial LP 102a transmits an implant event message including an event marker indicative of a nature of the event (e.g., intrinsic/sensed atrial event, paced atrial event). When a ventricular LP 102b senses/paces a ventricular event, the ventricular LP 102b transmits an implant event message including an event marker indicative of a nature of the event (e.g., intrinsic/sensed ventricular event, paced ventricular event). In certain embodiments, each LP 102a, 102b transmits an implant event message to the other LP 102a, 102b preceding the actual pace pulse so that the remote LP can blank its sense inputs in anticipation of that remote pace pulse (to prevent inappropriate crosstalk sensing). The above describe implant event messages are examples of i2i messages.
The implant event messages may be formatted in various manners. As one example, each event message may include a leading trigger pulse (also referred to as an LP wakeup notice, wakeup pulse or wakeup signal) followed by an event marker. The notice trigger pulse (also referred to as the wakeup notice, wakeup pulse or wakeup signal) is transmitted over a first channel (e.g., with a pulse duration of approximately 10 us to approximately 1 ms and/or within a fundamental frequency range of approximately 1 KHz to approximately 100 KHz). The notice trigger pulse indicates that an event marker is about to be transmitted over a second channel (e.g., within a higher frequency range). The event marker can then be transmitted over the second channel.
The event markers may include data indicative of one or more events (e.g., a sensed intrinsic atrial activation for an atrial located LP, a sensed intrinsic ventricular activation for a ventricular located LP). The event markers may include different markers for intrinsic and paced events. The event markers may also indicate start or end times for timers (e.g., an AV interval, a blanking interval, etc.). Optionally, the implant event message may include a message segment that includes additional/secondary information.
Optionally, the LP (or other IMD) that receives any i2i communication message from another LP (or other IMD) or from an external device may transmit a receive acknowledgement indicating that the receiving LP (or other IMD) received the i2i communication message. In certain embodiments, where an IMD expects to receive an i2i communication message within a window, and fails to receive the i2i communication message within the window, the IMD may transmit a failure-to-receive acknowledgement indicating that the receiving IMD failed to receive the i2i communication message. In other words, an LP can receive a message from another LP that includes an indicator (e.g., an error code) in its payload, or header, that indicates to the LP that the other LP failed to receive an expected message from the LP. Other variations are also possible and within the scope of the embodiments described herein.
The event messages enable the LPs 102a, 102b to deliver synchronized therapy and additional supportive features (e.g., measurements, etc.). To maintain synchronous therapy, each of the LPs 102a and 102b is made aware (through the event messages) when an event occurs in the chamber containing the other LP 102a, 102b. Some embodiments described herein provide efficient and reliable processes to maintain synchronization between LPs 102a and 102b without maintaining continuous communication between LPs 102a and 102b. In accordance with certain embodiments herein, low power event messages/signaling may be maintained between LPs 102a and 102b synchronously or asynchronously.
For synchronous event signaling, LPs 102a and 102b may maintain synchronization and regularly communicate at a specific interval. Synchronous event signaling allows the transmitter and receivers in each LP 102a, 102b to use limited (or minimal) power as each LP 102a, 102b is only powered for a small fraction of the time in connection with transmission and reception. For example, LP 102a, 102b may transmit/receive (Tx/Rx) communication messages in time slots having duration of 10-20 μs, where the Tx/Rx time slots occur periodically (e.g., every 10-20 ms).
LPs 102a and 102b may lose synchronization, even in a synchronous event signaling scheme. As explained herein, features may be included in LPs 102a and 102b to maintain device synchronization, and when synchronization is lost, LPs 102a and 102b undergo operations to recover synchronization. Also, synchronous event messages/signaling may introduce a delay between transmissions which causes a reaction lag at the receiving LP 102a, 102b. Accordingly, features may be implemented to account for the reaction lag.
During asynchronous event signaling, LPs 102a and 102b do not maintain communication synchronization. During asynchronous event signaling, one or more of receivers 120 and 122 of LPs 102a and 102b may be “always on” (always awake) to search for incoming transmissions. However, maintaining LP receivers 120, 122 in an “always on” (always awake) state presents challenges as the received signal level often is low due to high channel attenuation caused by the patient's anatomy. Further, maintaining the receivers awake will deplete the battery 114 more quickly than may be desirable.
The asynchronous event signaling methods avoid risks associated with losing synchronization between devices. However, the asynchronous event signaling methods utilize additional receiver current between transmissions. For purposes of illustration only, a non-limiting example is described hereafter. For example, the channel attenuation may be estimated to have a gain of 1/500 to 1/10000. A gain factor may be 1/1000th. Transmit current is a design factor in addition to receiver current. As an example, the system may allocate one-half of the implant communication current budget to the transmitter (e.g., 0.5 μA for each transmitter). When LP 102a, 102b maintains a transmitter in a continuous on-state and the electrode load is 500 ohms, a transmitted voltage may be 2.5V. When an event signal is transmitted at 2.5V, the event signal is attenuated as it propagates and would appear at LP 102a, 102b receiver as an amplitude of approximately 0.25 mV.
To overcome the foregoing receive power limit, a pulsed transmission scheme may be utilized in which communication transmissions occur correlated with an event. By way of example, the pulsed transmission scheme may be simplified such that each transmission constitutes a single pulse of a select amplitude and width.
In accordance with certain embodiments herein, LPs 102a and 102b may utilize multi-stage receivers that implement a staged receiver wakeup scheme in order to improve reliability yet remain power efficient. Each of LPs 102a and 102b may include first and second receivers 120 and 122 that operate with different first and second activation protocols and different first and second receive channels. For example, first receiver 120 may be assigned a first activation protocol that is “always on” (also referred to as always awake) and that listens over a first receive channel that has a lower fundamental frequency range/pulse duration (e.g., 1 KHz to 100 KHz/10 μs to approximately 1 ms) as compared to the fundamental frequency range (e.g., greater than 100 KHz/less than 10 μs per pulse) assigned to the second receive channel.
In accordance with certain embodiments, the first receiver 120 may maintain the first channel active (awake) at all times (including when the second channel is inactive (asleep)) in order to listen for messages from a remote LP. The second receiver 122 may be assigned a second activation protocol that is a triggered protocol, in which the second receiver 122 becomes active (awake) in response to detection of trigger events over the first receive channel (e.g., when the incoming signal corresponds to the LP wakeup notice, activating the second channel at the local LP). The terms active, turned on, awake and enabled are used interchangeably herein.
Still referring to
The controller 112 and the pulse generator 116 may be configured to transmit event messages, via the electrodes 108, in a manner that does not inadvertently capture the heart in the chamber where LP 102a, 102b is located, such as when the associated chamber is not in a refractory state. In addition, an LP 102a, 102b that receives an event message may enter an “event refractory” state (or event blanking state) following receipt of the event message. The event refractory/blanking state may be set to extend for a determined period of time after receipt of an event message in order to avoid the receiving LP 102a, 102b from inadvertently sensing another signal as an event message that might otherwise cause retriggering. For example, the receiving LP 102a, 102b may detect a measurement pulse from another LP 102a, 102b or the programmer 109.
Since the conductive communication receivers 120, 122 (or alternatively, just a single conductive communication receiver) and the pulse generator 116 are used to perform conductive communication, these components can be considered parts of a conductive communication transceiver 124. The conductive communication transceiver 124 can alternatively include alternative and/or additional components that enable an LP, or other type of IMD, to transmit and receive conductive communication messages with another IMD and/or with an external device, such as the programmer 109. For an example, while the same pulse generator 116 can be used to produce pacing pulses (for use in pacing a patient's heart) and conductive communication pulses (for use in communicating with another IMD or an external device), it would also be possible that the conductive communication transceiver 124 can include its own dedicated pulse generator. For another example, as noted above, it would also be possible for the conductive communication transceiver 124 to include only a single receiver, rather than both receivers 120, 122. Other variations are also possible and within the scope of the embodiments described herein.
Still referring to
The RF communication transceiver 134 consumes more battery power than the conductive communication transceiver 124. More generally, it is more power efficient from an LP 102 (or other type of IMD) to use conductive communication than to use RF communication to communicate with another LP 102 (or other type of IMD). Accordingly, in accordance with certain embodiments of the present technology, the LP 102 (or other type of IMD) is configured to primarily transmit and receive messages using conductive communication, and RF communication is used as a backup or auxiliary type of communication that can be used when conductive communication is deactivated (aka turned off) or is unsuccessful or otherwise deficient, as will be described in additional detail below.
In accordance with certain embodiments herein, the programmer 109 may communicate over a programmer-to-LP channel, with LP 102a, 102b utilizing the same communication scheme. The external programmer 109 may listen to the event message transmitted between LP 102a, 102b and synchronize programmer to implant communication such that programmer 109 does not transmit communication messages 113 until after an i2i messaging sequence is completed.
In accordance with certain embodiments, LP 102a, 102b may combine transmit operations with therapy. The transmit event marker may be configured to have similar characteristics in amplitude and pulse-width to a pacing pulse and LP 102a, 102b may use the energy in the event messages to help capture the heart. For example, a pacing pulse may normally be delivered with pacing parameters of 2.5V amplitude, 500 ohm impedance, 60 bpm pacing rate, 0.4 ms pulse-width. The foregoing pacing parameters correspond to a current draw of about 1.9 μA. The same LP 102a, 102b may implement an event message utilizing event signaling parameters for amplitude, pulse-width, pulse rate, etc. that correspond to a current draw of approximately 0.5 μA for transmit.
LP 102a, 102b may combine the event message transmissions with pacing pulses. For example, LP 102a, 102b may use a 50 μs wakeup transmit pulse having an amplitude of 2.5V which would draw 250 nC (nano Coulombs) for an electrode load of 500 ohm. The pulses of the transmit event message may be followed by an event message encoded with a sequence of short duration pulses (for example 16, 2 μs on/off bits) which would draw an additional 80 nC. The event message pulse would then be followed by the remaining pulse-width needed to reach an equivalent charge of a nominal 0.4 ms pace pulse. In this case, the current necessary to transmit the marker is essentially free as it was used to achieve the necessary pace capture anyhow. With this method, the savings in transmit current could be budgeted for the receiver or would allow for additional longevity.
When LP 102a or 102b senses an intrinsic event, it can send a qualitatively similar event pulse sequence (but indicative of a sensed event) without adding the pace pulse remainder. As LP 102a, 102b longevity calculations are designed based on the assumption that LP 102a, 102b will deliver pacing therapy 100% of the time, transmitting an intrinsic event marker to another LP 102a, 102b will not impact the nominal calculated LP longevity.
In some embodiments, LP 102a, 102b may deliver pacing pulses at relatively low amplitude. When low amplitude pacing pulses are used, the power budget for event messages may be modified to be a larger portion of the overall device energy budget. As the pacing pulse amplitude is lowered closer to amplitude of event messages, LP 102a, 102b increases an extent to which LP 102a, 102b uses the event messages as part of the pacing therapy (also referred to as sharing “capture charge” and “transmit charge”). As an example, if the nominal pacing voltage can be lowered to <1.25 V, then a “supply halving” pacing charge circuit could reduce the battery current draw by approximately 50%. A 1.25V pace pulse would save 1.5 μA of pacing current budget. With lower pulse amplitudes, LP 102a, 102b may use larger pulse-widths.
By combining event messages and low power pacing, LP 102a, 102b may realize additional longevity. Today longevity standards provide that the longevity to be specified based on a therapy that utilizes 2.5V amplitude, 0.4 ms pulses at 100% pacing. Optionally, a new standard may be established based on pacing pulses that deliver lower amplitude and/or shorter pacing pulses.
While not shown, a communication capacitor can be provided in LP 102a, 102b. The communication capacitor may be used to transmit event signals having higher voltage for the event message pulses to improve communication, such as when the LPs 102a and 102b experience difficulty sensing event messages. The high voltage event signaling may be used for implants with high signal attenuation or in the case of a retry for an ARQ (automatic repeat request) handshaking scheme.
In some embodiments, each individual LP 102 can comprise a hermetic housing 110 configured for placement on or attachment to the inside or outside of a cardiac chamber and at least two leadless electrodes 108 proximal to the housing 110 and configured for bidirectional communication with at least one other device (e.g., an NV-ICD 106) within or outside the body.
The electrodes 108 can be configured to communicate bidirectionally among the multiple leadless cardiac pacemakers and/or the implanted ICD 106 to coordinate pacing pulse delivery and optionally other therapeutic or diagnostic features using messages that identify an event at an individual pacemaker originating the message and a pacemaker receiving the message react as directed by the message depending on the origin of the message. An LP 102a, 102b that receives the event message reacts as directed by the event message depending on the message origin or location. In some embodiments or conditions, the two or more leadless electrodes 108 can be configured to communicate bidirectionally among the one or more leadless cardiac pacemakers 102 and/or the ICD 106 and transmit data including designated codes for events detected or created by an individual pacemaker. Individual pacemakers can be configured to issue a unique code corresponding to an event type and a location of the sending pacemaker.
In some embodiments, an individual LP 102a, 102b can be configured to deliver a pacing pulse with an event message encoded therein, with a code assigned according to pacemaker location and configured to transmit a message to one or more other leadless cardiac pacemakers via the event message coded pacing pulse. The pacemaker or pacemakers receiving the message are adapted to respond to the message in a predetermined manner depending on type and location of the event.
Moreover, information communicated on the incoming channel can also include an event message from another leadless cardiac pacemaker signifying that the other leadless cardiac pacemaker has sensed a heartbeat or has delivered a pacing pulse, and identifies the location of the other pacemaker. For example, LP 102b may receive and relay an event message from LP 102a to the programmer. Similarly, information communicated on the outgoing channel can also include a message to another leadless cardiac pacemaker or pacemakers, or to the ICD, that the sending leadless cardiac pacemaker has sensed a heartbeat or has delivered a pacing pulse at the location of the sending pacemaker.
Referring again to
In a further embodiment, a cardiac pacing system 100 comprises at least one LP 102a, 102b configured for implantation in electrical contact with a cardiac chamber and configured to perform cardiac pacing functions in combination with the co-implanted ICD 106. Each LP 102 comprise at least two leadless electrodes 108 configured for delivering cardiac pacing pulses, sensing evoked and/or natural cardiac electrical signals, and transmitting information to the co-implanted ICD 106.
As shown in the illustrative embodiments, an LP 102a, 102b can comprise two or more leadless electrodes 108 configured for delivering cardiac pacing pulses, sensing evoked and/or natural cardiac electrical signals, and bidirectionally communicating with the co-implanted ICD 106.
Each LP 102a, 102b can be configured for operation in a respective particular location and to have a respective particular functionality at manufacture and/or by programming by an external programmer. Bidirectional communication among the multiple leadless cardiac pacemakers can be arranged to communicate notification of a sensed heartbeat or delivered pacing pulse event and encoding type and location of the event to another implanted pacemaker or pacemakers. The LP 102a, 102b receiving the communication decode the information and respond depending on location of the receiving pacemaker and predetermined system functionality.
In some embodiments, the LPs 102a and 102b are configured to be implantable in any chamber of the heart, namely either atrium (RA, LA) or either ventricle (RV, LV). Furthermore, for dual-chamber configurations, multiple LPs may be co-implanted (e.g., one in the RA and one in the RV, one in the RV and one in the coronary sinus proximate the LV). Certain pacemaker parameters and functions depend on (or assume) knowledge of the chamber in which the pacemaker is implanted (and thus with which the LP is interacting; e.g., pacing and/or sensing). Some non-limiting examples include sensing sensitivity, an evoked response algorithm, use of AF suppression in a local chamber, blanking & refractory periods, etc. Accordingly, each LP needs to know an identity of the chamber in (or on) which the LP is implanted, and processes may be implemented to automatically identify a local chamber associated with each LP.
Processes for chamber identification may also be applied to subcutaneous pacemakers, ICDs, with leads and the like. A device with one or more implanted leads, identification and/or confirmation of the chamber into which the lead was implanted could be useful in several pertinent scenarios. For example, for a DR or CRT device, automatic identification and confirmation could mitigate against the possibility of the clinician inadvertently placing the V lead into the A port of the implantable medical device, and vice-versa. As another example, for an SR device, automatic identification of implanted chamber could enable the device and/or programmer to select and present the proper subset of pacing modes (e.g., AAI or VVI), and for the IPG to utilize the proper set of settings and algorithms (e.g., V-AutoCapture vs ACap-Confirm, sensing sensitivities, etc.).
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Instead of, or in addition to, using the magnetic field sensor 156 to detect a magnetic field for the purpose of determining when the LP 102 (or other type of IMD) is likely being exposed to an MRI system, another type of sensor can be used to detect a surrogate of a magnetic field that is produced by an MRI system. Such a surrogate of a magnetic field that is produced by an MRI system can be a secondary acoustic and/or vibratory effect of an MRI system. More specifically, the accelerometer 143 (or some other sensor configured to detect acceleration, sound and/or vibration), while not capable of actually detecting the magnetic field from an MRI system, can detect secondary acoustic and/or vibratory effects of an MRI system. That is, while an intended purpose of an MRI system is to generate time-varying gradient magnetic fields, unintended but inevitable results of generating the time-varying gradient magnetic fields are relatively loud noises and vibrations, which are surrogates of the magnetic field generated by the MRI system. Certain embodiments of the present technology take advantage of such unintended but inevitable secondary acoustic and/or vibratory effects of an MRI system.
In various embodiments, LP 102a, 102b can manage power consumption to draw limited power from the battery, thereby reducing 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 constant power from the battery.
In some embodiments, the controller 112 in an LP 102 can access signals on the electrodes 108 and can examine output pulse duration from another LP 102 for usage as a signature for determining triggering information validity and, for a signature arriving within predetermined limits, activating delivery of a pacing pulse following a predetermined delay of zero or more milliseconds. The predetermined delay can be preset at manufacture, programmed via an external programmer, or determined by adaptive monitoring to facilitate recognition of the triggering signal and discriminating the triggering signal from noise. In some embodiments or in some conditions, the controller 112 can examine output pulse waveform from another leadless cardiac pacemaker for usage as a signature for determining triggering information validity and, for a signature arriving within predetermined limits, activating delivery of a pacing pulse following a predetermined delay of zero or more milliseconds.
The housing can also include an electronics compartment 210 within the housing that contains the electronic components necessary for operation of the pacemaker, including, e.g., a pulse generator, transceiver, a battery, and a processor for operation. The hermetic housing 202 can be adapted to be implanted on or in a human heart, and can be cylindrically shaped, rectangular, spherical, or any other appropriate shapes, for example.
The housing can comprise a conductive, biocompatible, inert, and anodically safe material such as titanium, 316L stainless steel, or other similar materials. The housing can further comprise an insulator disposed on the conductive material to separate electrodes 108a and 108b. The insulator can be an insulative coating on a portion of the housing between the electrodes, and can comprise materials such as silicone, polyurethane, parylene, or another biocompatible electrical insulator commonly used for implantable medical devices. In the embodiment of
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The electrodes 108a and 108b can comprise pace/sense electrodes, or return electrodes. A low-polarization coating can be applied to the electrodes, such as sintered platinum, platinum-iridium, iridium, iridium-oxide, titanium-nitride, carbon, or other materials commonly used to reduce polarization effects, for example. In
Several techniques and structures can be used for attaching the housing 202 to the interior or exterior wall of the heart. A helical fixation mechanism 205, can enable insertion of the device endocardially or epicardially through a guiding catheter. A torqueable catheter can be used to rotate the housing and force the fixation device into heart tissue, thus affixing the fixation device (and also the electrode 108a in
LPs 102a and 102b can utilize implant-to-implant (i2i) communication through event messages to coordinate operation with one another in various manners. The terms i2i communication, i2i event messages, and i2i event markers are used interchangeably herein to refer to event related messages and IMD/IMD operation related messages transmitted from an implanted device and directed to another implanted device (although external devices, e.g., a programmer, may also receive i2i event messages). In certain embodiments, LP 102a and LP 102b operate as two independent leadless pacers maintaining beat-to-beat dual-chamber functionality via a “Master/Slave” operational configuration. For descriptive purposes, the ventricular LP 102b shall often be referred to as “vLP” and the atrial LP 102a shall often be referred to as “aLP”. The LP 102 that is designated as the master device (e.g., vLP) may implement all or most dual-chamber diagnostic and therapy determination algorithms. For purposes of the following illustration, it is assumed that the vLP is a “master” device, while the aLP is a “slave” device. Alternatively, the aLP may be designated as the master device, while the vLP may be designated as the slave device. The master device orchestrates most or all decision-making and timing determinations (including, for example, rate-response changes).
In accordance with certain embodiments, methods are provided for coordinating operation between first and second leadless pacemakers (LPs) configured to be implanted entirely within first and second chambers of the heart. A method transmits an event marker through conductive communication through electrodes located along a housing of the first LP, the event marker indicative of one of a local paced or sensed event. The method detects, over a sensing channel, the event marker at the second LP. The method identifies the event marker at the second LP based on a predetermined pattern configured to indicate that an event of interest has occurred in a remote chamber. In response to the identifying operation, the method initiates a related action in the second LP. In certain embodiments, event messages and/or other types of i2i messages can be alternatively, or additionally, transmitted using RF communication, as will be described in more detail below.
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As with i2i transmission 402, i2i transmission 506 may include an envelope that may include one or more individual pulses. For example, similar to envelope 406, the envelope of i2i transmission 506 may include a low frequency pulse followed by a high frequency pulse train. In certain embodiments, the i2i transmission 506 is transmitted during a refractory period that follows the sensed event.
Optionally, wherein the first LP is located in an atrium and the second LP is located in a ventricle, the first LP produces an AS/AP event marker to indicate that an atrial sensed (AS) event or atrial paced (AP) event has occurred or will occur in the immediate future. For example, the AS and AP event markers may be transmitted following the corresponding AS or AP event. Alternatively, the first LP may transmit the AP event marker slightly prior to delivering an atrial pacing pulse. Alternatively, wherein the first LP is located in an atrium and the second LP is located in a ventricle, the second LP initiates an atrioventricular (AV) interval after receiving an AS or AP event marker from the first LP; and initiates a post atrial ventricular blanking (PAVB) interval after receiving an AP event marker from the first LP.
Optionally, the first and second LPs may operate in a “pure” master/slave relation, where the master LP delivers “command” markers in addition to or in place of “event” markers. A command marker directs the slave LP to perform an action such as to deliver a pacing pulse and the like. For example, when a slave LP is located in an atrium and a master LP is located in a ventricle, in a pure master/slave relation, the slave LP delivers an immediate pacing pulse to the atrium when receiving an AP command marker from the master LP.
In accordance with some embodiments, communication and synchronization between the aLP and vLP is implemented via conducted communication of markers/commands in the event messages (per i2i communication protocol). As explained above, conducted communication represents event messages transmitted from the sensing/pacing electrodes at frequencies outside the RF (e.g., Wi-Fi or BLE) frequency range. Alternatively, the event messages may be conveyed over communication channels operating in the RF frequency range. The figures and corresponding description below illustrate non-limiting examples of markers that may be transmitted in event messages. The figures and corresponding description below also include the description of the markers and examples of results that occur in the LP that receives the event message. Table 1 represents example event markers sent from the aLP to the vLP, while Table 2 represents example event markers sent from the vLP to the aLP. In the master/slave configuration, AS event markers are sent from the aLP each time that an atrial event is sensed outside of the post ventricular atrial blanking (PVAB) interval or some other alternatively-defined atrial blanking period. The AP event markers are sent from the aLP each time that the aLP delivers a pacing pulse in the atrium. The aLP may restrict transmission of AS markers, whereby the aLP transmits AS event markers when atrial events are sensed both outside of the PVAB interval and outside the post ventricular atrial refractory period (PVARP) or some other alternatively-defined atrial refractory period. Alternatively, the aLP may not restrict transmission of AS event markers based on the PVARP, but instead transmit the AS event marker every time an atrial event is sensed.
As shown in Table 1, when an aLP transmits an event message that includes an AS event marker (indicating that the aLP sensed an intrinsic atrial event), the vLP initiates an AV interval timer. If the aLP transmits an AS event marker for all sensed events, then the vLP would preferably first determine that a PVAB or PVARP interval is not active before initiating an AV interval timer. If however the aLP transmits an AS event marker only when an intrinsic signal is sensed outside of a PVAB or PVARP interval, then the vLP could initiate the AV interval timer upon receiving an AS event marker without first checking the PVAB or PVARP status. When the aLP transmits an AP event marker (indicating that the aLP delivered or is about to deliver a pace pulse to the atrium), the vLP initiates a PVAB timer and an AV interval time, provided that a PVARP interval is not active. The vLP may also blank its sense amplifiers to prevent possible crosstalk sensing of the remote pace pulse delivered by the aLP.
As shown in Table 2, when the vLP senses a ventricular event, the vLP transmits an event message including a VS event marker, in response to which the aLP may initiate a PVARP interval timer. When the vLP delivers or is about to deliver a pace pulse in the ventricle, the vLP transmits VP event marker. When the aLP receives the VP event marker, the aLP initiates the PVAB interval timer and also the PVARP interval timer. The aLP may also blank its sense amplifiers to prevent possible crosstalk sensing of the remote pace pulse delivered by the vLP. The vLP may also transmit an event message containing an AP command marker to command the aLP to deliver an immediate pacing pulse in the atrium upon receipt of the command without delay.
The foregoing event markers are examples of a subset of markers that may be used to enable the aLP and vLP to maintain full dual chamber functionality. In one embodiment, the vLP may perform all dual-chamber algorithms, while the aLP may perform atrial-based hardware-related functions, such as PVAB, implemented locally within the aLP. In this embodiment, the aLP is effectively treated as a remote ‘wireless’ atrial pace/sense electrode. In another embodiment, the vLP may perform most but not all dual-chamber algorithms, while the aLP may perform a subset of diagnostic and therapeutic algorithms. In an alternative embodiment, vLP and aLP may equally perform diagnostic and therapeutic algorithms. In certain embodiments, decision responsibilities may be partitioned separately to one of the aLP or vLP. In other embodiments, decision responsibilities may involve joint inputs and responsibilities.
Messages that are transmitted between LPs (e.g., the aLP and the vLP) can be referred to herein generally as i2i messages, since they are implant-to-implant messages. As noted above, such messages can include event markers that enable one LP to inform the other LP of a paced event or a sensed event. For example, in certain embodiments, whenever the aLP 102a senses an atrial event or paces the right atrium, the aLP will transmit an i2i message to the vLP 102b to inform the vLP of the sensed or paced event in the atrium. In response to receiving such an i2i message, the vLP 102b may start one or more timers that enable the vLP to sense or pace in the right ventricle. Similarly, the vLP may transmit an i2i message to the aLP 102a whenever the vLP senses a ventricular event or paces the right ventricle.
The i2i messages that are sent between LPs may be relatively short messages that simply allow a first LP to inform a second LP of an event that was sensed by the first LP or caused (paced) by the first LP, and vice versa. Such i2i messages can be referred to herein as event marker i2i messages, or more succinctly as event i2i messages. The i2i messages that are sent between LPs, in certain instances, can be extended i2i messages that include (in addition to an event marker) an extension. In certain embodiments, an extended i2i message includes an event marker (e.g., 9 bits), followed by an extension indicator (e.g., 2 bits), followed by an extended message payload portion (e.g., 17 bits), followed by a cyclic redundancy check (CRC) code (e.g., 6 bits) or some other type of error detection and correction code.
In certain embodiments, whenever an i2i message is sent by an LP (or other type of IMD, such as a S-ICD), the i2i message will include an extension indicator so that the receiving LP knows whether or not the i2i message it receives includes an extension portion. In such embodiments, even a relatively short event i2i message will include an extension indicator. The extension indicator (e.g., 2 bits) is used by the LP (or other IMD) sending the i2i message to indicate, to the LP receiving the i2i message, whether or not the i2i message is an extended i2i message. In certain embodiments, if the LP receiving an i2i message determines based on the extension indicator bits that the received i2i message is not an extended i2i message, then the LP receiving the i2i message can ignore any bits that follow the extension bits. In such a case, the LP receiving the i2i message only decodes the event marker. On the other hand, if the LP receiving an i2i message determines based on the extension indicator bits that the received i2i message is an extended i2i message, then the LP receiving the i2i message will also decode the bits that follow the extension bits, and determine based on a CRC code (or other type of error detection and correction code), whether the i2i message is a valid message. If the extended i2i message is a valid i2i message, then the LP receiving the extended i2i message will as appropriate modify its operation, update parameters, and/or the like, based on information included in the extended i2i message. In certain embodiments, event i2i messages that are not extended i2i messages do not include any error detection and correction code.
In an extended i2i message, the event marker bits and the extension indicator bits are located, respectively, in an event marker field and an extension indicator field of an i2i message packet. In certain embodiments, the extended portion (that follows the event marker bits and the extension indicator bits) includes message bits (in a message field) and rate indicator bits (in a rate indicator field), which are parts of the payload. The payload can alternatively, or additionally, include other types of fields, such as an acknowledgement field that is used in certain situations for one LP to acknowledge reception of an i2i message from another LP of certain (e.g., critical) types of message.
More generally, various different types of information may be included within the payload of an extended i2i message. For one example, the payload can include a pacing rate indicator that enables one LP to inform another LP of a pacing rate. For example, assume that an LP system provides rate responsive pacing, wherein a pacing rate is adjusted in dependence on a patient's physical activity as detected, e.g., using an accelerometer, temperature sensor, and/or other type of sensor of an LP. In such an LP system, the vLP may inform the aLP of the rate at which the patient's heart should be paced so that the aLP and vLP can perform synchronized pacing. To achieve this, the vLP can send a pacing rate indicator to the aLP in the payload of an extended i2i message. The pacing rate indicator can, e.g., be a value indicating a pacing rate value (e.g., 80 bpm), a code that the aLP that can look up (e.g., in a stored look up table) and corresponds to a pacing rate value, or a value that the aLP feeds into an equation to determine the pacing rate, but is not limited thereto. Alternatively, the pacing rate indicator can be beat-to-beat interval value (e.g., 0.75 seconds), a code that the aLP can look up and corresponds to a beat-to-beat interval value, or a value that the aLP feeds into an equation to determine the beat-to-beat interval, but is not limited thereto. Other variations are also possible and within the scope of the embodiments described herein.
As noted above, implantable medical devices and systems often rely on proper i2i communication to operate correctly. For example, in a dual leadless pacemaker system, such as the one described above with reference to
Because the frequencies used for RF communication are above the frequencies produced by an MRI system, IMDs can communicate with one another using RF communication even when the IMDs are subjected to an MRI scan. However, a detriment of IMDs only utilizing RF communication to communicate with one another is that RF communication is much less power efficient than conductive communication, rendering the lifespan of such IMDs relatively short of the IMD only used RF communication to communicate with another IMD, which is undesirable.
In accordance with certain embodiments of the present technology, IMDs (e.g., such as two LPs of a dual chamber LP system) are configured to communicate with one another primarily and by default using conductive communication, which is energy efficient, and the IMDs are configured to use RF communication (which is less energy efficient) as a backup up and/or auxiliary type of communication. With such embodiments, the lifespan of the IMDs can be relatively long, potentially up to seven years or more, which is desirable. There are various different ways that such embodiments can be achieved, as will be described below. However, in order for these embodiments to be implemented, the IMDs should be capable of performing both conductive communication and RF communication. The LPs 102, described above with reference to
In accordance with certain embodiments, IMDs (e.g., LPs 102) are configured to normally communicate with one another using conductive communication (and more specifically, by sending conductive communication messages to one another), while an MRI mode of the IMD is deactivated (aka turned off), and the IMDs are configured to communicate with one another using RF communication (and more specifically, by sending RF communication messages to one another) when the MRI mode of the IMD is activated (aka turned on). This is beneficial because the IMDs will normally communicate using energy efficient conductive communication, and the IMDs will still be able to communicate with one another (albeit less energy efficiently) using RF communication when the IMDs are subjected to an MRI scan. In certain such embodiments, the MRI mode of the IMDs can be selectively activated (i.e., turned on) using a non-implanted device, such as, but not limited to, an external programmer (e.g., 109) that wirelessly communicates with the IMD. Once the MRI mode of the IMDs is activated, the MRI mode of the IMDs can be deactivated (e.g., after an MRI scan is completed) by the same non-implanted device, or another non-implanted device. It would also be possible for the MRI mode to be deactivated (i.e., turned off) after a specified amount of time has elapsed since the MRI mode was turned on. In other words, a controller 112 and/or timer of an IMD can be used to determine whether an MRI timeout period (e.g., 6 hours) has expired, and the IMD can be autonomously deactivate (i.e., turn off) that MRI mode once the MRI timeout period expires. This way, if a clinician forgets to use a programmer (or some other type of non-implanted device) to turn off the MRI mode of an IMD, the IMD will not be stuck in the MRI mode indefinitely. It is noted that the terms active, enable, and turn on, are often used interchangeably herein. Similarly, the terms deactivate, disable, and turn off, or often used interchangeably herein.
Depending upon the specific implementation, the MRI mode of an IMD can cause the IMD to send messages using RF communication instead or, or in addition to, sending messages using conductive communication. In other words, when an IMD is in its IMD mode, the IMD can transmit just RF communication messages to another IMD, or the IMD can transmit both RF communication messages and conductive communication messages. In accordance with certain embodiments, the RF communication transceiver (e.g., 134) of an IMD (e.g., LP 102) is disabled when the MRI mode is deactivated, and the RF communication transceiver is enabled when the MRI mode is activated. In certain embodiments, at least a portion of the conductive communication transceiver (e.g., 124) is disabled when the RF communication transceiver (e.g., 134) is enabled. For example, the receiver(s) (e.g., 120, 124) of the conductive communication transceiver can be disabled while the RF communication transceiver is enabled. In other embodiments, the conductive communication transceiver (e.g., 124) remains enabled while the RF communication transceiver (e.g., 134) is enabled, so that a controller (e.g., 112) of the IMD can determine when a conductive communication capability has been restored, in response to which, the RF communication transceiver (e.g., 134) can be disabled.
There can be additional components and/or capabilities of an IMD (e.g., LP 102) that can be selectively enabled and disabled based on whether or not the IMD is in its MRI mode. However, in certain embodiments, the components and/or capabilities of an IMD that are selectively enabled and disabled, based on whether or not the IMD is in its MRI mode, only involve communication components and capabilities of the IMD. More specifically, in certain embodiments conductive communication capabilities are enabled and RF communication capabilities are disabled when the MRI mode is turned off, and RF communication capabilities are enabled when the MRI mode is turned on. In certain such embodiments, when the MRI mode is turned on, the conductive communication capabilities are disabled. In other embodiments, when the MRI mode is turned on, the conductive communication capabilities remain enabled, such that when the MRI mode it turned on, both the RF communication and the conductive communication capabilities of the IMD are enabled.
In certain embodiments, rather than relying on a clinician to use a non-implanted device (e.g., a programmer 109) to activate and deactivate an MRI mode of IMDs (e.g., LPs 102), the IMDs can themselves detect when the IMDs are likely being exposed to an MRI scan, and the IMDs themselves can selectively activate their MRI mode. More specifically, a sensor of an IMD can detect a magnetic field, or a surrogate thereof, that is likely generated by an MRI system, and in response thereto, the IMD (or more specifically, the controller thereof) can activate the MRI mode of the IMD. For example, referring back to
Certain embodiments of the present technology, where are described below, related to systems, methods, and devices for improving communication between first and second IMDs, wherein such IMDs are remotely located relative to one another and are capable of communicating with one another using both conductive communication and RF communication. Referring briefly back to
Referring to
For more specific examples, where the first IMD is the aLP 102a and the second IMD is the vLP 102b, at step 602 the messages that are sent by the aLP 102a to the vLP 102b μsing conductive communication can be or include an atrial sensed (AS) event marker, or an atrial paced (AP) event marker, or can include some other type of message, such as a command message, or an acknowledgement (ACK) message that the aLP 102a uses to acknowledge that it received a message from the vLP 102b. Where the first IMD is the vLP 102b and the second IMD is the aLP 102a, the messages that are sent by the vLP 102b to the aLP 102a can be or include a ventricular sensed (VS) event marker, or a ventricular paced (VP) event marker, or can include some other type of message, such as a command message, or an acknowledgement (ACK) message that the vLP 102b uses to acknowledge that it received a message from the aLP 102a. These are just a few examples of the types of messages that can be sent from a first IMD to a second IMD, and vice versa, which are not intended to be all encompassing. Indeed, as explained above, one or both the IMDs need not be an LP. However, for the remainder of this discussion, it is often assumed that the first and second IMDs are LPs.
Still referring to
If the answer to the determination at step 606 is No (i.e., if the first trigger event is not detected), then flow returns to step 602 and the first IMD continues to use conductive communication (without using RF communication) to transmit message(s) to the second IMD. In other words, steps 602, 604, and 606 will continue in a loop until the answer to the determination at step 606 is Yes. The period of time during which the first IMD transmits messages to the second IMD using conductive communication, without using RF communication, can be referred to herein as a first period of time.
If the answer to the determination at step 606 is Yes (i.e., if the first trigger event is detected), then flow goes to step 608a and the first IMD starts using RF communication (without using conductive communication) to transmit message(s) to the second IMD.
Still referring to
If the answer to the determination at step 612 is No (i.e., if the second trigger event is not detected), then flow returns to step 608a and the first IMD continues to use RF communication (without using conductive communication) to transmit message(s) to the second IMD. In other words, steps 608a, 610, and 612 will continue in a loop until the answer to the determination at step 612 is Yes. The period of time during which the first IMD transmits messages to the second IMD using RF communication, can be referred to herein as a second period of time.
If the answer to the determination at step 612 is Yes (i.e., if the second trigger event is detected), then flow goes to back to step 602 and the first IMD starts using conductive communication (without using RF communication) to transmit message(s) to the second IMD.
The messages that the first IMD transmits to the second IMD at instances of steps 602 and 604 can also be referred to as messages intended for the second IMD, since the second IMD is the intended recipient of the messages, but there is no guarantee that the messages will actually be received by the second IMD. In accordance with certain embodiments, the one or more messages intended for the second IMD, that are transmitted by the first IMD using conductive communication at one or more instances of step 602 during the first period of time, are transmitted within a first frequency range. By contrast, the one or more messages intended for the second IMD, that are transmitted by the first IMD using RF communication during the second period of time, are transmitted within a second frequency range that is above the first frequency range. For example, the frequency range that is used for performing conductive communication at instances of step 602 can be, e.g., within the range of about 1 KHz to about 250 KHz. By contrast, the frequency range that is used for RF communication at instances of step 608a is significantly higher, depending upon which type of RF communication is used. For example, if Bluetooth Low Energy (BLE) is used for RF communication at instance of step 608a, then the frequency range is within the range of about 2.40 GHz to about 2.48 GHz. For another example, if the Medical Device Radiocommunications Service (MedRadio) is used for RF communication at instances of step 608a, then the frequency range is within the range of about 400 MHz to about 406 MHz. It would also be possible to use one of the WiFi frequency bands for RF communication.
In accordance with certain embodiments, the first trigger event that is monitored for (at steps 604 and/or 606) comprises a magnetic resonance imaging (MRI) mode of the first IMD being activated, and the second trigger event that is monitored for (at steps 610 and/or 612) comprises the MRI mode of the first IMD being deactivated. Accordingly, with such embodiments, the first IMD can communication with the second IMD using RF communication during a period of time (e.g., the second period of time) that a patient (in which the first and second IMDs are implanted) is being scanned using an MRI system, thereby enabling the first and second IMDs to continuously synchronously pace the patient even when the MRI system prevents the use of conductive communication.
The MRI mode of the first IMD can be manually or automatically activated and deactivated, depending upon the embodiment and implementation. For example, in certain embodiments, the MRI mode of the first IMD is activated using an external programmer (e.g., 109), or some other types of non-implanted device. In such embodiments, the MRI mode of the first IMD can be deactivated using an external programmer that can be the same as or different than the external programmer that activated the MRI mode. For example, when a patient (within which the first and second IMDs are implanted) visits a radiology clinic, a hospital, or the like, for the purpose of having an MRI scan, a clinician can use an external programmer (e.g., 109) to activate the MRI mode of the IMDs. Then, after the MRI scan has been completed, the clinician can use the external programmer (e.g., 109) to deactivate the MRI mode. It would also be possible for the MRI mode to be deactivated in response to an MRI timeout period expiring. More specifically, an amount of time since the MRI mode was initially activated can be monitored using a timer, or a controller (e.g., 112), to determine whether an MRI timeout period has elapsed. The MRI timeout period can, for example, be in the range of 1 hour to 10 hours, and in a specific example can be 6 hours. The MRI timeout period can be pre-programmed to a default value (e.g., 6 hours), but may be reprogrammed by a clinician. A benefit of having the IMD automatically deactivate the MRI mode, after the MRI time out period expires, is that the IMD will soon transition back to using conductive communication to send messages to the second IMD, even if a clinician forgets to deactivate the MRI mode after the MRI scan has been completed.
In accordance with certain embodiments, the MRI mode of the first IMD is automatically activated in response to a sensor of the first IMD detecting a magnetic field, or a surrogate thereof, that is likely generated by an MRI system. For example, a magnetic field sensor (e.g., 156 in
Instead of, or in addition to, using a magnetic field sensor (e.g., 156) to detect a magnetic field for the purpose of determining when the LP 102 (or other type of IMD) is likely being exposed to an MRI system, and thus, that a first trigger event is detected, another type of sensor can be used to detect a surrogate of a magnetic field that is likely produced by an MRI system, which in response to be detected, causes an MRI mode of the IMD to be activated. Such a surrogate of a magnetic field that is produced by an MRI system can be a secondary acoustic and/or vibratory effect of an MRI system. More specifically, the accelerometer (e.g., 143 in
One or more alternative and/or additional type(s) of trigger events can be monitored for at instances of steps 604 and/or 606, and at instances of steps 610 and/or 612. For example, in certain embodiments, the first trigger event that is monitored for at step 604 and/or 606 comprises the first IMD determining that the second IMD did not successfully receive one or more of the messages, intended for the second IMD, that the first IMD transmitted using conductive communication. There are various different ways in which the first IMD can determine that the second IMD did not successfully receive one or more of the messages, intended for the second IMD, that the first IMD transmitted using conductive communication. In an embodiment, the first IMD can make this determination based on the first IMD not receiving an expected acknowledgement (ACK) message from the second IMD. In another embodiment, the first IMD can make this determination based on the first IMD receiving a message from second IMD that informs the first IMD that the second IMD failed to receive a message that the second IMD expected to receive from the first IMD. This can involve, for example, the second IMD sending to the first IMD a message that includes an indicator (e.g., an error code) in its payload, or header, that indicates to the first IMD that the second IMD failed to receive an expected message from the first IMD. For example, where the first IMD is the aLP 102a and the second IMD is the vLP 102b, the vLP 102b may expect to receive an AS or an AP event type of conductive communication message once every cardia cycle from aLP 102a, and if the vLP 102b does not receive such a message, the vLP 102b can send an error code (or other type of indicator) to the aLP 102a, which informs the aLP 102a that the vLP 102b failed to receive an expected AS or AP event message from the aLP 102a. For another example, where the first IMD is the vLP 102b and the second IMD is the aLP 102a, the aLP 102a may expect to receive a VS or an VP event type of conductive communication message once every cardia cycle from vLP 102b, and if the aLP 102a does not receive such a message, the aLP 102a can send an error code (or other type of indicator) to the vLP 102b, which informs the vLP 102b that the aLP 102a failed to receive an expected VS or VP event message from the vLP 102b. In certain such embodiments, where messages at instances of steps 608a are only transmitted using RF communication (but not using conductive communication), then the second trigger event that is monitored for at instances of steps 610 and/or 612 can be a specified amount of time elapsing since the first IMD transitioned to using RF communication (instead of conductive communication) in response to the first trigger event being detected at an instance of step 604 and/or 606. Other variations are also possible, and within the scope of the embodiments described herein.
Gradient noise from an MRI system is just one example of a type of noise that may adversely affect conductive communication, without adversely affecting RF communication. Accordingly, the first trigger event that is monitored for at instances of steps 604 and/or 606 can more generally be a level of noise (e.g., within the frequency range that is used for performing conductive communication) exceeding a first noise threshold, and the second trigger event that is monitored for at instances of steps 610 and/or 612 can be the level of noise being below a second noise threshold, which can be the same as or different than the first noise threshold. Examples of such other types of noise include, but are not limited to, electromagnetic interference (EMI), or noise from an Electronic Article Surveillance (EAS) gate, a power transformer, a wireless charging device, and/or the like. In accordance with certain embodiments, the first IMD can detect that the level of noise exceeds the first noise threshold when the first IMD decodes at least a threshold number of invalid messages within a same cardiac cycle. In other words, in certain embodiments the first trigger event can be an IMD decoding at least a threshold number of invalid messages within a same cardiac cycle.
Conductive i2i communication, as with any communication modality, is susceptible to disruptions due to extrinsic interference (aka extrinsic noise). In an implantable system that includes multiple IMDs capable of communicating with one another using conductive communication (e.g., a dual chamber LP system), whenever an IMD receives pulses that could potentially be a conductive i2i communication message (and more specifically, a packet), the IMD that receives the potential (aka possible) conductive i2i communication packet attempts to decode the possible packet and determines whether it is a valid packet. A received packet is determined to be valid if the packet as decoded includes a valid code (sequence of bits), that can be one of one or more (e.g., four) predetermined codes that is recognizable to the IMD that received the packet. Otherwise the received packet is determined to be invalid, and is ignored. When an IMD detects an invalid message, it could be said that the IMD detects an i2i Null. If the received packet is determined to be valid it can be used by the IMD that received the packet, e.g., to time when to perform pacing or other therapy, to perform a command included in the received packet, and/or the like. The above described operation that an IMD performs can be referred to herein as packet validation. In accordance with certain embodiments, an IMD performs this packet validation operation each time the IMD receives what appears to be a wakeup pulse of an conductive i2i communication packet transmitted by another IMD. When extrinsic interference is not present or is relatively low, an IMD will typically only receive one conductive i2i communication packet, and thus typically only one wakeup pulse, from another IMD per cardiac cycle. However, when extrinsic interference is relatively high, an IMD may receive numerous pulses that appear to be a wakeup pulse but are actually just noise. Accordingly, when intrinsic interference is relatively high, an IMD may perform the above described packet validation operation numerous times per cardiac cycle, because the packet validation operation is performed in response to each received pulse that appears to be a wakeup pulse.
As another layer of protection on top of the aforementioned packet validation that an IMD performs on each received conductive i2i communication packet, and more specifically in response to each received pulse that appears to be a wakeup pulse, each IMD can also be configured to identify the presence of persistent interference (aka persistent noise) within the passband of its one or more conductive i2i communication receiver(s). If such persistent i2i interference is detected, the receiving IMD can be configured to temporarily disable its reception and transmission of i2i communications for a disable period (e.g., a specified duration of time, or a specified number of cardiac cycles) before again checking to determine whether the i2i interference is still present. This mitigation feature within an implantable system with multiple IMDs (e.g., an implantable dual chamber LP system) that utilizes conductive i2i communication can be referred to as “i2i Noise Reversion” and is intended to further reduce the possibility of inadvertent false-positive or false-negative errors occurring during i2i packet validation. While an IMD that is an LP is in its i2i Noise Reversion mode, which can also be referred to as a Noise State, the IMD can operate in a safe pacing mode (e.g., VVI or VOO) that does not depend on i2i communication. More specifically, an LP may transition to its i2i Noise Reversion Mode (aka Noise State) if a threshold number N of invalid messages are received within a single cardiac cycle (or within a specified number of consecutive cardiac cycles), where the threshold number N can be programmable within a specified range (e.g., from 1 to 30 cardiac cycles), and may have a default value (e.g., 10 or 15). Explained another way, an LP transitions to its i2i Noise Reversion Mode (aka Noise State) if a threshold number N of i2i Nulls are detected within a single cardiac cycle, or a specified number of consecutive cardiac cycles. As mentioned above, once an LP (or other type of IMD) enters is its i2i Noise Reversion Mode (aka Noise State) the LP (or other type of IMD) remains in that state for a disable period, during which it may operate in a safe pacing mode. The disable period is programmable, e.g., can be within a specified range (e.g., from 1 to 255 cardiac cycles), and may have a default value (e.g., 64). At the end of the disable period, the IMD enables its reception and transmission of i2i communications, to determine whether there is a continued presence of i2 interference. If so, then the IMD will reenter its i2i Noise Reversion Mode (aka Noise State) for another disable period, before checking again to determine whether there is a continued presence of i2 interference. Once the presence of i2i interference is no longer detected, the LP will keep its reception and transmission of i2i communications enabled. While an LP is in the i2i Noise Reversion Mode, beat-to-beat AV synchrony may not be maintained because the aLP and the vLP are not communicating with one another on a beat-by-beat basis.
In accordance with certain embodiments, the first trigger event that is monitored for at instances of steps 604 and/or 606 can be an IMD detecting a threshold number N of invalid messages (aka i2i nulls) being received within a single cardiac cycle, and the second trigger event that is monitored for at instances of steps 610 and/or 612 can be an IMD detecting less than the threshold number N of invalid messages (aka i2i nulls) being received within a single cardiac cycle.
In accordance with certain embodiments, the first trigger event that is monitored for at instances of steps 604 and/or 606 can be an arrhythmia being detected or arrhythmia therapy being delivered, and the second trigger event that is monitored for at instances of steps 610 and/or 612 can be the arrhythmia no longer being detected or the arrhythmia therapy being completed. For example, if an LP detects ventricular fibrillation (VF), the LP can turn on its RF communication capability to more quickly and reliably communication with an NV-ICD to instruct the ICD to deliver a defibrillation shock. This may be beneficial because RF communication is typically faster and more reliable than conductive communication, and delivery of a defibrillation shock may adversely affect conductive communication. The first trigger event can be the detection of any type of arrhythmia or arrhythmia therapy, or just specific types of arrhythmias or arrhythmia therapies.
In the embodiments described above with reference to
A comparison between
In the embodiments described above with reference to
In accordance with certain embodiments, boosted conductive communication is achieved by increasing the amplitude (e.g., peak-to-peak amplitude) of each of the pulses included in a conductive communication message. In other words, the amplitude of the boosted conductive communication pulses is greater than the amplitude of the normal conductive communication pulses. Such an increase in the amplitude can be, e.g., in the range of a 20 percent increase to a 100 percent increase, with a 100 percent increase meaning the amplitude is doubled compared to the normal amplitude. It would alternatively be possible to achieve boosted conductive communication by increasing the duty cycle or pulse width of conductive communication pulses included in a conductive communication, since the energy of individual conductive communication pulses depends at least in part on the amplitude and the pulse width of the pulses. In still another embodiment, boosted conductive communication can be achieved by increasing both the amplitude and the pulse width or duty cycle of pulses included in a conductive communication message. In specific embodiments, during boosted conductive communication both the pulse amplitude and the pulse width of each wakeup pulse transmitted from one IMD to another IMD is increased, but only the amplitude of the pulses in the remainer of a packet (that follows each wakeup pulse) is increased. A reason for transitioning from normal conductive communication to boosted conductive communication is that increasing the amplitude (or more generally the energy) of conductive communication pulses increases a probability that the pulses will be capable of being received in the presence of extrinsic noise, e.g., by raising the energy of the pulses above the noise floor.
Referring now to
At step 607 a boosted conductive communication (BBC) timer or counter is initialized and started, and boosted conductive communication starts (i.e., begins) being used as indicated at step 609. Where a BCC timer us used, the BCC timer can be configured to count up or down to a certain value (corresponding to a programmed specified period of time), at which point the BCC timer times out. Such a programmed specified period of time could be, e.g., within the range of 20 to 120 seconds, but is not limited thereto. Where a BCC counter is used, the BCC counter can be configured to be incremented or decremented each cardiac cycle and to time out in response the BCC counter counting a specified number of cardiac cycles. Such a programmed specified number of cardiac cycles could be, e.g., within the range of 20 to 120 cardiac cycles, but is not limited thereto. More generally, a timer or counter can be used to determine whether a specified amount of time or cardiac cycles elapsed since the timer or counter was started. Referring briefly back to
Referring again to
If the answer to the determination at step 612 is No (i.e., if the second trigger event is not detected), then flow goes to step 613. At step 613 there is a determination of whether the BCC timer expired or the BCC counter reached a specified counter value. More generally, at step 613 there is a determination of whether a specified amount of time or cardiac cycles elapsed since the BCC timer or counter was started. If the answer to the determination at step 613 is No, then flow returns to step 609 and the first IMD continues to use boosted conductive communication to transmit message(s) to the second IMD. In other words, steps 609, 610, 612, and 613 will continue in a loop until the answer to the determination at step 612 is Yes or the answer to the determination at step 613 is Yes. The period of time during which the first IMD transmits i2i messages to the second IMD using boosted conductive communication, can be referred to herein as a second period of time.
If the answer to the determination at step 612 is Yes (i.e., if the second trigger event is detected), then flow goes to back to step 602 and the first IMD starts using normal conductive communication to transmit message(s) to the second IMD, in order to conserve energy since the IMD consumes more power using boosted conductive communication than using normal conductive communication. If the answer to the determination at step 612 is No, then flow goes to step 613, as noted above. At step 613 there is a determination of whether the BCC timer has expired (or the BCC counter has reached the specified count value). Explained another way, at step 613 there is a determination of whether boosted conductive communication has been performed for the programmed specified duration such that the IMD should try to return to using normal conductive communication instead of using boosted communication to send i2i message(s) to the second IMD, because normal conductive communication is more energy efficient than boosted conductive communication. After the answer to the determination at one of steps 612 or 613 is Yes, and flow returns to step 602 and the first IMD returns to using normal conductive communication, it is possible that a first trigger event can be detected at the next instances of steps 604, 606, and the first IMD may return to using boosted conductive communication very quickly. However, in many cases, after the first IMD returns to using normal conductive communication it can continue using normal conductive communication for a relatively long period of time before eventually returning to using boosted conductive communication in response to detecting another instance of the first trigger event.
In accordance with certain embodiments of the present technology, if there is sufficient persistent noise that prevents the first IMD from being able to communicate within second IMD, and likely vice versa, using implant-to-implant (i2i) conductive communication, the first IMD (and likely also the second IMD) can enter the i2i Noise Reversion Mode (which can also be referred to herein as a Noise State) described above, during which IMDs may mode switch to operating in a safe pacing mode (e.g., VVI or VOO) that does not depend on i2i communication, and the IMDs may disable their i2i communication capabilities. Once in the i2i noise reversion mode, an IMD may remain in that mode (and temporarily stop attempting to communicate within another IMD) for a programmed specified duration of time (e.g., 60 seconds) or a programmed specified number of cardiac cycles (e.g., 60 cardiac cycles), at the end of which the IMD can enable its reception and transmission of i2i communications, to determine whether there is a continued presence of i2 interference. If so, then the IMD will reenter its i2i Noise Reversion Mode (aka Noise State) for another disable period, before checking again to determine whether there is a continued presence of noise that adversely affects i2i conductive communication. Once the presence of noise that adversely affects i2i conductive communication is no longer detected, the IMD will keep its reception and transmission of i2i communications enabled. It should be appreciated that while boosted conductive communication should improve the probability of IMDs being able to perform i2i communication with one another in the presence of some noise (at the expense of increasing energy consumption), extrinsic persistent noise may be present that will prevent IMDs from communicating with one another using conductive communication regardless of the energy level of the conductive communication pulses being transmitted.
The embodiments described above with reference to
Referring now to
In the flow diagram of
The i2i messages that the first IMD transmits to the second IMD at instances of steps 602, 609, and 618a can also be referred to as messages intended for the second IMD, since the second IMD is the intended recipient of the messages, but there is no guarantee that the messages will actually be received by the second IMD. In accordance with certain embodiments, the one or more i2i messages intended for the second IMD, that are transmitted by the first IMD using normal conductive communication at one or more instances of step 602 during the first period of time, and are transmitted by the first IMD using boosted conductive communication at one or more instances of step 609 during the second period of time, are transmitted within a first frequency range. By contrast, the one or more messages intended for the second IMD, that are transmitted by the first IMD using RF communication during a third period of time, are transmitted within a second frequency range that is above the first frequency range. For example, the frequency range that is used for performing normal conductive communication at instances of step 602 and boosted conductive communication at instances of step 609 can be, e.g., within the range of about 1 KHz to about 250 KHz. By contrast, the frequency range that is used for RF communication at instances of step 618a is significantly higher, depending upon which type of RF communication is used. For example, if BLE is used for RF communication at instance of step 618a, then the frequency range is within the range of about 2.40 GHz to about 2.48 GHz. For another example, if the Medical Device Radiocommunications Service (MedRadio) is used for RF communication at instances of step 618a, then the frequency range is within the range of about 400 MHz to about 406 MHz. It would also be possible to use one of the WiFi frequency bands for RF communication.
In the embodiments described above with reference to
A comparison between
It is noted where one of the embodiments described with reference to
Referring to
Returning to step 704, if the answer to the determination at step 704 is No (i.e., if the IMD did not receive an i2i message from the other IMD using conductive communication), then at step 708 an RF communication capability of the IMD is turned on. Then at step 710, the next time the IMD is to send an i2i message to the other IMD, the IMD sends the i2i message to the other IMD using both RF communication and conductive communication, wherein the i2i message includes a communication error indicator that informs the other IMD (e.g., the second IMD) that the IMD (e.g., the first IMD) failed to successfully receive the previous expected i2i message from the other IMD (e.g., the second IMD) using conductive communication. Such an indicator (e.g., an error code) can be included, e.g., in a payload, or a header, of the i2i message that is sent by the IMD to the other IMD using both RF communication and conductive communication. It is noted that the terms send and transmit are often used interchangeably herein, as are the terms sent and transmitted.
At step 712 the IMD monitors for an i2i message from the other IMD using both RF communication and conductive communication. At step 714 there is a determination of whether the IMD received an i2i message from the other IMD using conductive communication. If the answer to the determination at step 714 is No, then flow returns to step 710. The loop that includes steps 710, 712, and 714 will continue until the IMD receives an i2i message from the other IMD using conductive communication. For the sake of this discussion, it is assumed that the IMD is successfully receiving i2i messages from the other IMD using RF communication during a period of time that the loop including 710, 712, and 714 may be repeated. Where an i2i message is received using conductive communication, it can be said that an IMD receives an i2i message over a conductive communication channel. Where an i2i message is received using RF communication, it can be said that the IMD receives an i2i message over an RF communication channel. Because the frequency range that is used for RF communication is above the frequency range that is used for conductive communication, as explained above, it can be said that the frequency of the RF communication channel is above the frequency of the conducive communication channel.
If the answer to the determination at step 714 is Yes, then flow goes to step 716. At step 716 the RF communication capability of the IMD is turned off. After step 716, flow goes to step 706. As noted above, at step 706 there is a determination of whether the received i2i message included a communication error indicator, which indicated that the other IMD (e.g., the second IMD) did not successfully receive a conductive communication message from the IMD (e.g., the first IMD), e.g., within its own message reception window. If the answer to step 706 is No, then flow returns to step 702. However, if the answer to step 706 is Yes, (i.e., if there is an indicator, e.g., an error code) in the i2i message received from the other IMD using conductive communication (which indicated that the other IMD did not successfully receive an expected i2i message using conductive communication), then flow goes to step 718.
At step 718 the RF communication capability of the IMD is turned on. Then at step 720, the next time the IMD is to send an i2i message to the other IMD, the IMD sends the i2i message to the other IMD using both RF communication and conductive communication, wherein the i2i message does not include a communication error indicator that informs the other IMD (e.g., the second IMD) that the IMD (e.g., the first IMD) failed to successfully receive the previous expected i2i message from the other IMD (e.g., the second IMD) using conductive communication.
At step 722 the IMD monitors for an i2i message from the other IMD using both RF communication and conductive communication. At step 724 there is a determination of whether the IMD received an i2i message from the other IMD using conductive communication. If the answer to the determination at step 724 is No, then flow returns to step 710. If the answer to the determination at step 724 is Yes, then flow goes to step 716. At step 716 the RF communication capability of the IMD is turned off. After step 716, flow goes to step 706, which was already explained above.
Since steps 722 and 724 are identical, respectively, to step 712 and 714, it would also be possible to eliminate steps 722 and 724, and that flow goes directly from step 720 to step 712.
In another variation, flow can go directly from step 714 to step 706 (and/or directly from step 724 to step 706), and the RF communication capability can instead be turned off whenever the answer to the determination at step 706 is No. In other words, the flow diagram can be modified such that step 716 is performed between instances of step 706 and 702, whenever the answer to the determination at step 706 is No (i.e., whenever the i2i message that the IMD receives from the other IMD does not include an indicator specifying that the other IMD failed to receive an expected i2i message using conductive communication). Other variations are also possible and within the scope of the embodiments described herein.
As alluded to above, a reason it is better to use conductive communication, than to use RF communication, for sending and receiving i2i messages between IMDs, is that conductive communication is more energy efficient than RF communication, thereby providing for greater IMD longevity. However, there are situations where conductive communication will fail (e.g., during an MRI scan), but RF communication can be successfully used. Accordingly, certain embodiments of the present technology described herein primarily and by default using conductive communication for sending and receiving i2i messages between IMDs, which is energy efficient, and use RF communication as a backup or auxiliary way for sending and receiving i2i messages when needed. A feasibility analysis was performed to determine how much the selective use of RF communication (for sending and receiving i2i messages between IMDs) would affect the longevity of an IMD. Results of the feasibility analysis were that the selective use of RF communication would reduce the battery longevity of an IMD (and thus, the longevity of the IMD) by less than two weeks, compared to if only conductive communication was used for sending messages between the IMDs. Accordingly, where the battery longevity of an IMD is expected to be about 7 years (i.e., about 364 weeks), the selective use of RF communication in an IMD that primarily and by default uses conductive communication, would likely reduce the battery longevity from about 364 weeks to about 362 weeks, which is a reduction in longevity of only about 0.5%. This slight reduction in longevity is believed to be worth the improvement in i2i communication reliability. In other words, it would be worth needing to replace IMDs about 2 weeks early, where the IMDs are expected to last about 7 years, and the IMDs are able to better communicate with one another and provide for synchronous operation (e.g., synchronous pacing) during the slightly shortened lifespan of the IMDs.
Referring again to
In accordance with certain embodiments of the present technology, where multiple IMDs are capable of communicating with one another using two or more different types (aka modes) of i2i communication, such as normal conductive communication, boosted conductive communication, and/or RF communication, one or more of the IMDs stores information in its memory to keep track (e.g., in a table that is dynamically updated) of the types of i2i communication being used by the various IMDs. In certain such embodiments, a primary-secondary architecture (aka a master-slave architecture, or aka a parent-child architecture) is implemented where a primary IMD (aka master IMD, or aka parent IMD) maintains information (e.g., in a table that is stored in memory and is dynamically updated over time) about the type (aka mode) of i2i communication that it expects each of the slave IMD(s) (aka second IMD(s), or aka child IMD(s)) to use to transmit and receive i2i messages at any given time. This way if the primary IMD knows that a specific secondary IMD is using boosted conductive communication to communicate with the primary IMD, the primary IMD will also use boosted conductive communication to communication with the specific secondary IMD; or if the primary IMD knows that the specific secondary IMD is using RF communication to communicate with the primary IMD, the primary IMD will also use RF conductive communication to communication with the specific secondary IMD. In certain implementations of the primary-secondary architecture, the primary IMD can instruct each of the secondary IMDs when to change to a different type (aka mode) of i2i communication. In such embodiments, it is the primary IMD that controls how the secondary IMDs perform i2i communication. Further, in certain embodiments of the primary-secondary architecture, the primary IMD can communicate with each of the secondary IMDs, and the secondary IMDs can communication with the primary IMD, but the secondary IMDs do not communicate directly with one another. The table (or other data structure for storing such information) that is stored by the primary IMD in its memory can also include additional information, such as the pulse width and/or pulse amplitude to be used for normal conductive communication and the pulse width and/or pulse amplitude to be used for boosted conductive communication.
In other embodiments, a decentralized architecture is implemented where each IMD maintains in its own memory its own information (e.g., its own table that is dynamically updated over time) about the type (aka mode) of i2i communication that it expects each of the other IMD(s) to use to transmit and receive i2i messages. Further, in the decentralized architecture, each of the IMDs can communicate directly with each of the other IMDs. Additionally, in the decentralized architecture each of the IMDs can make its own decision when to transition from one mode of i2i communication to another. The table (or other data structure for storing such information) that is stored by each of the IMDs in its memory can also include additional information, such as the pulse width and/or pulse amplitude to be used for normal conductive communication and the pulse width and/or pulse amplitude to be used for boosted conductive communication.
While many of the embodiments of the present technology described above have been described as being for use with LP type IMDs, embodiments of the present technology, can also be used with other types of IMDs besides an LP. Accordingly, unless specifically limited to use with an LP, the claims should not be limited to use with LP type IMDs.
IMD 801 has a housing 800 to hold the electronic/computing components. Housing 800 (which is often referred to as the “can”, “case”, “encasing”, or “case electrode”) may be programmably selected to act as the return electrode for certain stimulus modes. Housing 800 may further include a connector (not shown) with a plurality of terminals 802, 804, 806, 808, and 810. The terminals may be connected to electrodes that are located in various locations on housing 800 or elsewhere within and about the heart. IMD 801 includes a programmable microcontroller 820 that controls various operations of IMD 801, including cardiac monitoring and stimulation therapy. Microcontroller 820 includes a microprocessor (or equivalent control circuitry), RAM and/or ROM memory, logic and timing circuitry, state machine circuitry, and I/O circuitry.
IMD 801 further includes a first pulse generator 822 that generates stimulation pulses for delivery by one or more electrodes coupled thereto. Pulse generator 822 is controlled by microcontroller 820 via control signal 824. Pulse generator 822 may be coupled to the select electrode(s) via an electrode configuration switch 826, which includes multiple switches for connecting the desired electrodes to the appropriate I/O circuits, thereby facilitating electrode programmability. Switch 826 is controlled by a control signal 828 from microcontroller 820.
In the embodiment of
Microcontroller 820 is illustrated as including timing control circuitry 832 to control the timing of the stimulation pulses (e.g., pacing rate, atrio-ventricular (AV) delay, atrial interconduction (A-A) delay, or ventricular interconduction (V-V) delay, etc.). Timing control circuitry 832 may also be used for the timing of refractory periods, blanking intervals, noise detection windows, evoked response windows, alert intervals, marker channel timing, and so on. Timing control circuitry 832 can also include the BCC timer or counter described above, e.g., with reference to steps 607 and 613 in
IMD 801 is further equipped with a communication modem (modulator/demodulator) 840 to enable wireless communication with the remote slave pacing unit. Modem 840 may include one or more transmitters and two or more receivers as discussed herein in connection with
IMD 801 includes a sensing circuit 844 selectively coupled to one or more electrodes, that perform sensing operations, through switch 826 to detect the presence of cardiac activity in the right chambers of the heart. Sensing circuit 844 may include dedicated sense amplifiers, multiplexed amplifiers, or shared amplifiers. It may further employ one or more low power, precision amplifiers with programmable gain and/or automatic gain control, bandpass filtering, and threshold detection circuit to selectively sense the cardiac signal of interest. The automatic gain control enables the unit to sense low amplitude signal characteristics of atrial fibrillation. Switch 826 determines the sensing polarity of the cardiac signal by selectively closing the appropriate switches. In this way, the clinician may program the sensing polarity independent of the stimulation polarity.
The output of sensing circuit 844 is connected to microcontroller 820 which, in turn, triggers or inhibits the pulse generator 822 in response to the presence or absence of cardiac activity. Sensing circuit 844 receives a control signal 846 from microcontroller 820 for purposes of controlling the gain, threshold, polarization charge removal circuitry (not shown), and the timing of any blocking circuitry (not shown) coupled to the inputs of the sensing circuitry.
In the embodiment of
IMD 801 further includes an analog-to-digital (A/D) data acquisition system (DAS) 850 coupled to one or more electrodes via switch 826 to sample cardiac signals across any pair of desired electrodes. Data acquisition system 850 is configured to acquire intracardiac electrogram signals, convert the raw analog data into digital data, and store the digital data for later processing and/or telemetric transmission to an external device 854 (e.g., a programmer, local transceiver, or a diagnostic system analyzer). Data acquisition system 850 is controlled by a control signal 856 from the microcontroller 820.
Microcontroller 820 is coupled to a memory 860 by a suitable data/address bus. The programmable operating parameters used by microcontroller 820 are stored in memory 860 and used to customize the operation of IMD 801 to suit the needs of a particular patient. Such operating parameters define, for example, pacing pulse amplitude, pulse duration, electrode polarity, rate, sensitivity, automatic features, arrhythmia detection criteria, and the amplitude, waveshape and vector of each shocking pulse to be delivered to the patient's heart within each respective tier of therapy.
The operating parameters of IMD 801 may be non-invasively programmed into memory 860 through a telemetry circuit 864 in telemetric communication via communication link 866 with external device 854. Telemetry circuit 864 allows intracardiac electrograms and status information relating to the operation of IMD 801 (as contained in microcontroller 820 or memory 860) to be sent to external device 854 through communication link 866. Memory 860 may also store a table or other data structure that is dynamically updated over time to keep track of the types of i2i communication being used by the IMD 801 and/or other IMDs with which IMD 801 communicates.
IMD 801 can further include magnet detection circuitry (not shown), coupled to microcontroller 820, to detect when a magnet is placed over the unit. A magnet may be used by a clinician to perform various test functions of IMD 801 and/or to signal microcontroller 820 that external device 854 is in place to receive or transmit data to microcontroller 820 through telemetry circuits 864.
IMD 801 can further include one or more physiological sensors 870. Such sensors are commonly referred to as “rate-responsive” sensors because they are typically used to adjust pacing stimulation rates according to the exercise state of the patient. However, physiological sensor 870 may further be used to detect changes in cardiac output, changes in the physiological condition of the heart, or diurnal changes in activity (e.g., detecting sleep and wake states). Signals generated by physiological sensors 870 are passed to microcontroller 820 for analysis. Microcontroller 820 responds by adjusting the various pacing parameters (such as rate, AV Delay, V-V Delay, etc.) at which the atrial and ventricular pacing pulses are administered. While shown as being included within IMD 801, physiological sensor(s) 870 may be external to IMD 801, yet still be implanted within or carried by the patient. Examples of physiologic sensors might include sensors that, for example, sense respiration rate, pH of blood, ventricular gradient, activity, position/posture, minute ventilation (MV), and so forth.
A battery 872 provides operating power to all of the components in IMD 801. Battery 872 is capable of operating at low current drains for long periods of time, and is capable of providing high-current pulses (for capacitor charging) when the patient requires a shock pulse (e.g., in excess of 2 A, at voltages above 2 V, for periods of 10 seconds or more). Battery 872 also desirably has a predictable discharge characteristic so that elective replacement time can be detected. As one example, IMD 801 employs lithium/silver vanadium oxide batteries.
IMD 801 further includes an impedance measuring circuit 874, which can be used for many things, including: lead impedance surveillance during the acute and chronic phases for proper lead positioning or dislodgement; detecting operable electrodes and automatically switching to an operable pair if dislodgement occurs; measuring respiration or minute ventilation; measuring thoracic impedance for determining shock thresholds; detecting when the device has been implanted; measuring stroke volume; and detecting the opening of heart valves; and so forth. Impedance measuring circuit 874 is coupled to switch 826 so that any desired electrode may be used. In this embodiment IMD 801 further includes a shocking circuit 880 coupled to microcontroller 820 by a data/address bus 882.
It is to be understood that the subject matter described herein is not limited in its application to the details of construction and the arrangement of components set forth in the description herein or illustrated in the drawings hereof. The subject matter described herein is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Further, it is noted that the term “based on” as used herein, unless stated otherwise, should be interpreted as meaning based at least in part on, meaning there can be one or more additional factors upon which a decision or the like is made. For example, if a decision is based on the results of a comparison, that decision can also be based on one or more other factors in addition to being based on results of the comparison.
It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described 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 of the present technology without departing from its scope. While the dimensions, types of materials and coatings described herein are intended to define the parameters of the embodiments of the present technology, they are by no means limiting and are example embodiments. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the embodiments of the present technology should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted based on 35 U.S.C. § 112 (f), unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.
This application is a continuation-in-part (CIP) of U.S. patent application Ser. No. 17/684,969, filed Mar. 2, 2022, which claims priority to U.S. Provisional Patent Application No. 63/191,854, titled IMPROVED IMPLANT TO IMPLANT COMMUNICATION FOR USE WITH IMPLANTABLE MEDICAL DEVICES, filed May 21, 2021. Priority is claimed to each of the above applications, and each of the above applications is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63191854 | May 2021 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 17684969 | Mar 2022 | US |
| Child | 18742962 | US |
