Patent Description:
Implantable medical devices are commonly used today to monitor physiological or other parameters of a patient and/or deliver therapy to a patient. For example, to help patients with heart related conditions, various medical devices (e.g., pacemakers, defibrillators, etc.) can be implanted in a patient's body. Such devices may monitor and in some cases provide electrical stimulation (e.g. pacing, defibrillation, etc.) to the heart to help the heart operate in a more normal, efficient and/or safe manner. In another example, neuro stimulators can be used to stimulate tissue of a patient to help alleviate pain and/or other condition. In yet another example, an implantable medical device may simply be an implantable monitor that monitors one or more physiological or other parameters of the patient, and communicates the sensed parameters to another device such as another implanted medical device or an external device. In some cases, two or more devices cooperate to monitor and/or to provide therapy. In many of these examples, there is a desire to have such devices communicate with other devices when needed. Document <CIT> Al discloses a leadless dual-chamber pacing system.

The present disclosure pertains to medical devices, and more particularly to wireless intra-body communication between medical devices. The medical devices may include implantable medical devices (IMD), such as but not limited to leadless cardiac pacemakers (LCP), implantable cardioverter defibrillators (ICD), subcutaneous implantable cardioverter defibrillators (SICD), extracardiac implantable cardioverter defibrillators, transvenous implantable cardioverter defibrillators, neuro-stimulators (NS), implantable monitors (IM), and/or the like. In some cases, the medical devices may include one or more external medical devices such as device programmers, wearable defibrillators and/or other external medical devices.

In one example, an implantable medical device (IMD) may be configured to pace a patient's heart and to be disposable within a chamber of the patient's heart. The IMD may include a housing and a plurality of electrodes. A controller may be housed by the housing and may be operably coupled to the plurality of electrodes. In some cases, the controller may be configured to generate and deliver pacing pulses via a pair of the plurality of electrodes, to receive messages transmitted by conducted communication from a remote implantable medical device (IMD) via a pair of the plurality of electrodes, and to receive cardiac signals via a pair of the plurality of electrodes. The controller may also be configured to receive at least one of a plurality of transmissions of the same message transmitted by conducted communication by the remote IMD during a cardiac cycle, and when more than one of the plurality of transmissions of the same message are received by the controller during the cardiac cycle, the controller may be configured to treat the more than one transmissions of the same messages as communication of one message.

Alternatively or additionally to any of the embodiments above, the controller may be configured to institute a blanking period during the cardiac cycle during which received cardiac signals are ignored by the controller.

Alternatively or additionally to any of the embodiments above, the controller may be configured to receive at least one of a plurality of transmissions of the same message during the blanking period.

Alternatively or additionally to any of the embodiments above, the controller may be configured to institute the blanking period at a predetermined time following a detected R-wave in the received cardiac signal.

Alternatively or additionally to any of the embodiments above, the blanking period may be configured to extend over at least <NUM> percent of a cardiac cycle, but less than an entire cardiac cycle.

Alternatively or additionally to any of the embodiments above, the plurality of transmissions of the same message are received over a time duration that allows for physiological changes in the patient that result in differing communication vectors.

Alternatively or additionally to any of the embodiments above, the time duration may be selected to accommodate physiological changes in the patient resulting from the patient's heart beating.

Alternatively or additionally to any of the embodiments above, the time duration may be selected to accommodate physiological changes in the patient resulting from the patient breathing.

Alternatively or additionally to any of the embodiments above, the time duration may be shorter than a cardiac cycle.

Alternatively or additionally to any of the embodiments above, the time duration may span more than one cardiac cycle.

Alternatively or additionally to any of the embodiments above, the controller may be configured to institute a blanking period in response to receiving a message.

Alternatively or additionally to any of the embodiments above, the controller may be configured to generate and deliver pacing pulses via a first pair of the plurality of electrodes, to receive messages transmitted from the remote IMD via a second pair of the plurality of electrodes and to receive cardiac signals via a third pair of the plurality of electrodes, where the first pair of electrodes, the second pair of electrodes and the third pair of electrodes correspond to the same pair of electrodes.

Alternatively or additionally to any of the embodiments above, the message may be a command.

Alternatively or additionally to any of the embodiments above, the command may be an ATP command that instructs the controller to deliver Anti-Tachycardia Pacing (ATP) therapy to the patient's heart via a pair of the plurality of electrodes.

In another example, an implantable medical device (IMD) may be configured to sense electrical cardiac activity of a patient's heart and to deliver therapy to the patient's heart. The IMD may include a housing, a plurality of electrodes, and a controller that is housed by the housing and operably coupled to the plurality of electrodes. The controller may be configured to sense cardiac electrical activity via two or more of the plurality of electrodes and to deliver therapy via two or more of the plurality of electrodes. In some cases, the controller may be configured to analyze the sensed cardiac electrical activity and to make a determination as to whether to provide a message to a remote implantable medical device (IMD) secured to the patient's heart. When the controller makes a determination to provide a message to the remote IMD, the controller may be configured to transmit a plurality of transmissions of the message by conducted communication during a cardiac cycle of the patient's heart.

Alternatively or additionally to any of the embodiments above, the controller may be configured to add a tracking number to each of the plurality of transmissions of the message.

Alternatively or additionally to any of the embodiments above, the IMD may be incapable of receiving a conducted communication messages from the remote IMD.

Alternatively or additionally to any of the embodiments above, each of the plurality of redundant transmissions of the message may include a command to the remote IMD to deliver one or more pacing pulses, and the controller of the IMD may be configured to monitor cardiac electrical activity for an indication that the remote IMD delivered the one or more pacing pulses.

Alternatively or additionally to any of the embodiments above, after the controller makes a determination to provide a message to the remote IMD, the controller may be configured to transmit the plurality of redundant transmissions of the message within a communication time period, wherein the communication time period has a time duration is sufficiently long to allows the remote IMD to change orientations relative to the IMD as a result of physiological changes in the patient to result in a substantially different signal strength at the remote IMD.

In another example, a medical system for sensing and regulating cardiac activity of a patient may include an implantable cardioverter defibrillator (ICD) that is configured to sense electrical cardiac activity of a patient's heart and to deliver therapy to the patient's heart, and a leadless cardiac pacemaker (LCP) that is configured to pace a patient's heart. The ICD may include a housing, a plurality of electrodes and an ICD controller that is housed by the housing of the ICD and operably coupled to the plurality of electrodes of the ICD. The ICD controller may be configured to sense cardiac electrical activity via two or more of the plurality of electrodes of the ICD and to deliver therapy via two or more of the plurality of electrodes of the ICD. In some cases, the ICD controller may be further configured to analyze the sensed cardiac electrical activity and to make a determination as to whether to instruct a leadless cardiac pacemaker (LCP) to provide therapy to the patient's heart. When the ICD controller makes a determination to instruct the LCP to provide therapy to the patient's heart, the ICD controller may be configured to transmit a plurality of transmissions of an instruction during a single cardiac cycle of the patient's heart.

The LCP may include a housing, a plurality of electrodes that are exposed external to the housing of the LCP, and an LCP controller that is housed by the housing of the LCP and is operably coupled to the plurality of electrodes of the LCP. In some cases, the LCP controller may be configured to generate and deliver pacing pulses via two or more of the plurality of electrodes of the LCP, receive messages transmitted via two or more of the plurality of electrodes of the LCP, and receive cardiac signals via two or more of the plurality of electrodes of the LCP. The LCP controller may be further configured to receive at least one of the plurality of redundant transmissions of the instruction transmitted by the SICD during the single cardiac cycle, and when more than one of the plurality of redundant transmissions of the instruction are received by the LCP controller during the single cardiac cycle, the LCP controller may be configured to treat the more than one redundant transmissions of the instruction as one instruction, and only executes the one instruction and not each of the plurality of redundant transmissions of the instruction.

The above summary of some illustrative embodiments is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The Figures, and Detailed Description, which follow, more particularly exemplify some of these embodiments.

On the contrary, the intention is to cover all modifications, equivalents, and alternatives.

The following detailed description should be read with reference to the drawings in which similar structures in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the disclosure. While the present disclosure is applicable to any suitable implantable medical device (IMD), the description below often uses pacemakers and more particularly leadless cardiac pacemakers (LCP) as particular examples.

<FIG> is a schematic diagram showing an illustrative system <NUM> that may be used to sense and/or pace a heart H. In some cases, the system <NUM> may also be configured to shock the heart H. The heart H includes a right atrium RA and a right ventricle RV. The heart H also includes a left atrium LA and a left ventricle LV. In some cases, the system <NUM> may include a medical device that provides anti-arrhythmic therapy to the heart H. In some cases, the system <NUM> may include a first medical device <NUM> and a second medical device <NUM>. In some instances, the first medical device <NUM> may be implantable within the patient at a position near or even within the heart H. In some cases, the second medical device <NUM> may be implanted within the patient but at a location that is exterior to the heart H. For example, in some cases, the second medical device <NUM> may be implanted at a subcutaneous position within the patient's chest. In some cases, the second medical device <NUM> may be exterior to the patient.

In some cases, the second medical device <NUM> may be configured to maintain and/or trend pace settings and capture data for the first medical device <NUM> for the purposes of long-term optimization of pace settings. In some cases, the second medical device <NUM> may utilize additional inputs, such as posture, time of day, intrinsic heart rate, and the like, as inputs to a capture algorithm. The second medical device <NUM> may, for example, be configured to correlate changes in a pace threshold resulting from the other inputs, and proactively adjust pace settings. In some cases, the second medical device may be utilized to optimize the AV delay utilized by the first medical device <NUM>. For example, the second medical device <NUM> may be able to monitor ECG morphology and/or acceleration data, such as RV or LV pace timing.

If the second medical device is implanted prior to implanting the first medical device <NUM>, the second medical device <NUM> may be used to guide optimal placement of the first medical device <NUM> by, for example, monitoring the QRS width, morphology, Heart Rate Variability (HRV), accelerometer signals, etc. In some cases, the second medical device <NUM> could provide feedback of the attempted first medical device <NUM>'s location prior to fixation or untethering of the first medical device <NUM>. Minimizing QRS width, HRV and/or certain morphological parameters would be a possible goal of the clinician to obtain such an optimal implantation site, for example. In some cases, the second medical device <NUM> may be able to monitor the impedance and or heart sounds to possibly detect myocardial functional improvements as indicated by hypertrophy, or dilated cardiomyopathy. For example, these diseases generally have increased left ventricles, thus possibly lower impedance and/or contraction changes. These are just examples.

<FIG> is a schematic diagram showing an illustrative system <NUM> that may be used to sense and/or pace a heart H. In some cases, the system <NUM> may be considered as being an example of the system <NUM> shown in <FIG>. In some cases, the system <NUM> may include a leadless cardiac pacemaker (LCP) <NUM> and an implantable cardioverter defibrillator (ICD) <NUM>. In some cases, the ICD <NUM> may be a subcutaneous implantable cardioverter defibrillator (SICD), an extracardiac implantable cardioverter defibrillator and/or a transvenous implantable cardioverter defibrillator. In some cases, as illustrated, the ICD <NUM> may be an SICD. The LCP <NUM> may be considered as being an illustrative but non-limiting example of the first medical device <NUM> and the ICD <NUM> may be considered as being an illustrative but non-limiting example of the second medical device <NUM> described with respect to <FIG>.

In some cases, the LCP <NUM> may be intracardially implanted. While a single LCP <NUM> is shown in <FIG>, it will be appreciated that two or more LCPs <NUM> may be implanted in or on the heart H. The LCP <NUM> may be implanted into any chamber of the heart, such as the right atrium RA, the left atrium LA, the right ventricle RV and the left ventricle LV. When more than one LCP is provided, each LCP may be implanted in a different chamber. In some cases, multiple LCP's may be implanted within a single chamber of the heart H.

In some cases, the ICD <NUM> may be extracardially implanted. While not shown in <FIG>, in some cases the ICD <NUM> may include a lead/electrode that may be configured to be placed subcutaneously and outside of a patient's sternum. In other cases, the lead/electrode may extend around or through the sternum and may be fixed adjacent an inner surface of the sternum. In both cases, the lead/electrode is positioned extracardially (outside of the patient's heart). The ICD <NUM> may be configured to sense electrical activity generated by the heart H as well as provide electrical energy to the heart H in order to shock the heart H from an undesired heart rhythm to a desired heart rhythm.

In some cases, the LCP <NUM> and the ICD <NUM> may be implanted at the same time. In some instances, depending on the cardiac deficiencies of a particular patient, the ICD <NUM> may be implanted first, and one or more LCPs <NUM> may be implanted at a later date if/when the patient develops indications for receiving cardiac resynchronization therapy and/or it becomes necessary to pace the heart H. In some cases, it is contemplated that one or more LCPs <NUM> may be implanted first, in order to sense and pace the heart H. When a need for possible defibrillation becomes evident, the ICD <NUM> may subsequently be implanted. Regardless of implantation order or sequence, it will be appreciated that the LCP <NUM> and the ICD <NUM> may communicate with each other using any desired communications modality, such as conducted communication, inductive communication, acoustic communication, RF communication, optical communication and/or using any other suitable communication modality.

In some cases, the LCP <NUM> and the ICD <NUM> may work together in delivering therapy to the heart H. For example, in some cases, the ICD <NUM> may sense cardiac electrical activity of the heart H and may analyze the sensed cardiac electrical activity in order to determine whether the ICD <NUM> itself should deliver therapy such as shocking therapy to the heart H or if it would be appropriate for the ICD <NUM> to instruct the LCP <NUM> to deliver pacing therapy to the heart H. In some cases, the pacing therapy may be anti-tachycardia pacing (ATP) therapy, but this is just an example. When the ICD <NUM> determines that it would be appropriate to have the LCP <NUM> deliver pacing therapy, the ICD <NUM> may transmit a message to the LCP <NUM> instructing the LCP <NUM> to delivery pacing therapy.

In some cases, it will be appreciated that communication vectors between the ICD <NUM> and the LCP <NUM> may be at least somewhat time-dependent, particularly as the LCP <NUM> may be moving as a result of physiological changes in the patient, such as but not limited to the heart H beating and/or the patient breathing. For example, as the heart H beats, it will be appreciated that an LCP <NUM>, if anchored at its distal end to a heart wall of the heart H, can change orientation in response to the heart wall moving, blood flowing through the heart, and the like. In some cases, communication from the ICD <NUM> to the LCP <NUM> may be one-way communication, wherein the ICD <NUM> is not able to receive confirmation messages from the LCP <NUM>, and/or the LCP <NUM> is not able to transmit confirmation messages back to the ICD <NUM>, either as a result of hardware limitations or poor communication vectors, for example.

In some instances, and to help improve the robustness and/or reliability of the one-way communication channel, the ICD <NUM> may transmit a plurality of redundant transmissions of an instruction or other message to the LCP <NUM>. As a non-limiting example, the ICD <NUM> may be configured to transmit the same instruction three times. As long as at least one of the three redundant messages is successfully received by the LCP <NUM>, the LCP <NUM> is able to carry out the instruction received from the ICD <NUM>. In some cases, the plurality of redundant transmissions from the ICD <NUM> may be transmitted within a single cardiac cycle. Since the orientation of the LCP <NUM> relative to the ICD <NUM> may change over the course of a heartbeat, the communication vector between the LCP <NUM> and the ICD <NUM> may change over the course of a heartbeat. By transmitting redundant messages, the chance that the LCP <NUM> is not located along a null of the transmission field generated by the ICD <NUM> is increased for at least one of the messages, thereby potentially increasing the robustness and/or reliability of the communication channel. In some cases, the plurality of redundant transmissions from the ICD <NUM> are transmitted within a portion of a single cardiac cycle, such as in <NUM> percent, <NUM> percent, <NUM> percent, <NUM> percent, <NUM> percent, or more or less.

Similarly, the LCP <NUM> may be configured to receive one or more of the redundant messages transmitted by the ICD <NUM> and to recognize that any of the received messages are in fact redundant and represent repetition of a single instruction and/or message, rather than multiple instructions and/or messages. Accordingly, the LCP <NUM> may be configured to treat the more than one redundant instruction, if the LCP <NUM> successfully receives more than one redundant instruction, as a single instruction. As a result, the LCP <NUM> may only execute one instruction, and not each of the received redundant instructions. In some cases, particularly if the LCP <NUM> is not able to confirm receipt of instructions, or the ICD <NUM> is not able to receive such confirmatory or acknowledgement messages, the ICD <NUM> may monitor cardiac electrical activity for indications that the LCP <NUM> carried out the desired instruction(s). For example, the ICD <NUM> may monitor cardiac electrical activity for indications of an Anti-Tachycardia Pacing (ATP) therapy if the ICD <NUM> instructed the LCP <NUM> to carry out an ATP therapy.

<FIG> is a schematic diagram of an illustrative leadless cardiac pacemaker (LCP) <NUM> that may be considered as being an example of the LCP <NUM> (<FIG>). In some cases, the LCP <NUM> may include a housing <NUM> and a plurality of electrodes that are exposed external to the housing <NUM>. As illustrated, the LCP <NUM> includes a pair of electrodes <NUM>, <NUM> that are secured relative to the housing <NUM>. While two electrodes <NUM>, <NUM> are illustrated, it will be appreciated that in some cases the LCP <NUM> may include three or more electrodes. A controller <NUM> is disposed within the housing <NUM> and may be operably coupled to the pair of electrodes <NUM>, <NUM> via electrical connectors <NUM> and <NUM>, respectively. A power supply <NUM> is operably coupled to the controller <NUM> and provides power for operation of the controller <NUM> as well as providing power for generating pacing pulses that can be delivered via the pair of electrodes <NUM>, <NUM> via the controller <NUM>. In some cases, the controller <NUM> may be considered as being configured to generate and deliver a plurality of pacing pulses via the pair of electrodes <NUM>, <NUM>. In some cases, the LCP <NUM> may include one or more other sensors such as an accelerometer or a gyro, for example.

In some cases, the LCP <NUM> may include a communications module <NUM> that is operably coupled to the controller <NUM> and may be configured to receive messages from other devices, and in some cases send messages to other devices. In some cases, the communications module <NUM> may enable the LCP <NUM> to receive messages from another implanted device, such as but not limited to an SICD such as the ICD <NUM> (<FIG>). In some cases, the controller <NUM> may be configured to receive, via the communications module <NUM>, messages communicated via conducted communication that may be picked up by the electrodes <NUM>, <NUM>. In some cases, the messages received by the LCP <NUM> may represent a command from a remote device such as the ICD <NUM>. In some instances, the command may be an ATP command that instructs the controller <NUM> to deliver Anti-Tachycardia Pacing (ATP) therapy to the patient's heart H via a pair of the plurality of electrodes.

In some cases, the controller <NUM> may be configured to receive at least one of a plurality of redundant transmissions of the same message transmitted by conducted communication by a remote device such as the ICD <NUM> during a cardiac cycle. When more than one of the plurality of redundant transmissions of the same message are received by the controller <NUM> during the cardiac cycle, the controller <NUM> may be configured to treat the more than one redundant transmissions of the same messages as one message. In some cases, the controller <NUM> may be configured to institute a blanking period during the cardiac cycle during which cardiac signals sensed by the electrodes <NUM> and <NUM> are ignored by the controller <NUM>, meaning that the controller <NUM> is only listening for transmitted messages, and is ignoring cardiac electrical activity during the blanking period. In some cases, the controller <NUM> may be configured to institute a blanking period in response to receiving a message, possibly to see if additional messages are to be transmitted, for example. In some cases, the controller <NUM> may be configured to receive at least one of a plurality of redundant transmissions of the same message during the blanking period, and in some cases, may receive two or more of the plurality of redundant transmissions. In some cases, the controller <NUM> may be configured to institute a blanking period at a predetermined time following a detected R-wave in the received cardiac signal.

In some cases, the plurality of redundant transmissions of the same message may be received over a time duration that allows for physiological changes in the patient that result in differing communication vectors for each of the redundant messages. When a blanking period is provided, this time duration may correspond to the blanking period, or may lie at least partially outside the blanking period. In some cases, the time duration may be selected to accommodate physiological changes in the patient resulting from the patient's heart beating. In some cases, the time duration may be selected to accommodate physiological changes in the patient resulting from the patient breathing. In some instances, the time duration may be shorter than a cardiac cycle. In some cases, the time duration may span more than one cardiac cycle.

In some cases, the controller <NUM> of the LCP <NUM> may be configured to generate and deliver pacing pulses via a first pair of the plurality of electrodes, to receive messages transmitted from the implantable medical device (IMD) remote from the LCP via a second pair of the plurality of electrodes, and to receive cardiac signals via a third pair of the plurality of electrodes. In some cases, the first pair of electrodes, the second pair of electrodes and the third pair of electrodes correspond to the same pair of electrodes, while in others, different electrodes may be used.

<FIG> is a schematic diagram of an illustrative subcutaneous implantable cardioverter defibrillator (SICD) <NUM> that may, for example, be considered as being an example of the ICD <NUM> (<FIG>). The illustrative SICD <NUM> includes a housing <NUM> and an electrode support <NUM> that is operably coupled to the housing <NUM>. In some cases, the electrode support <NUM> may be configured to place one or more electrodes in a position, such as subcutaneous or sub-sternal, that enables the one or more electrodes to detect cardiac electrical activity as well as to deliver electrical shocks to the heart H when appropriate. In the example shown, the housing <NUM> may house a controller <NUM>, a power supply <NUM> and a communications module <NUM>. As illustrated, the electrode support <NUM> includes a first electrode <NUM>, a second electrode <NUM> and a third electrode <NUM>. In some cases, the electrode support <NUM> may include fewer or more electrodes. In some cases, the SICD <NUM> may include one or more other sensors such as an accelerometer or a gyro, for example.

In some cases, the controller <NUM> may be configured to analyze cardiac electrical activity sensed by two or more of the electrodes <NUM>, <NUM>, <NUM> and to make a determination as to whether to provide a message and/or instruction to a leadless cardiac pacemaker (LCP), such as but not limited to the LCP <NUM>, <NUM> implanted remote from the SICD <NUM> and secured to the patient's heart H. In some cases, when the controller <NUM> makes a determination to provide a message and/or instruction to the LCP <NUM>, <NUM>, the controller <NUM> may be configured to transmit a plurality of redundant transmissions of the message and/or instruction by conducted communication during a cardiac cycle of the patient's heart. In some cases, the controller <NUM> may be configured to add a tracking number to each of the plurality of redundant transmissions of the message and/or instruction. For example, the tracking number could be as simple as "<NUM> of <NUM>", "<NUM> of <NUM>" and "<NUM> of <NUM>" of three sequentially transmitted redundant messages. When such tracking numbers are added, the receiving LCP <NUM>, <NUM> may more easily recognize the messages as being repeated or redundant copies of the same message In other cases, the LCP <NUM>, <NUM> may simply treat all messages received during a predetermined time period (e.g. during a blanking period) as redundant messages of the same message.

In some cases, the ICD <NUM>, <NUM> may not be capable of receiving acknowledge messages such as but not limited to conducted communication messages from the LCP <NUM>, <NUM>, due to either hardware limitations or poor communication vectors. In some cases, each of the plurality of redundant transmissions of a message may include a command or instruction to the LCP <NUM>, <NUM> to deliver one or more pacing pulses, and the controller <NUM> of the SICD <NUM> may be configured to monitor cardiac electrical activity for an indication that the LCP <NUM>, <NUM> delivered the one or more pacing pulses. In some instances, after the controller <NUM> makes a determination to provide a message to the LCP <NUM>, <NUM>, the controller <NUM> may be configured to transmit the plurality of redundant transmissions of the message within a communication time period having a time duration that is sufficiently long to allows the LCP <NUM>, <NUM> to change orientations relative to the SICD <NUM> as a result of physiological changes in the patient to result in a substantially different vector and/or signal strength at the LCP <NUM>, <NUM>.

As noted, a blanking period may correspond to a portion of a cardiac cycle or may even extend over more than one cardiac cycle. <FIG> shows an illustrative electrocardiogram (ECG) <NUM> with several blanking periods indicated thereon. In the example shown, a first blanking period <NUM> follows an R-wave <NUM>. A second blanking period <NUM> follows an R-wave <NUM>. A third blanking period <NUM> follows an R-wave <NUM>. Each of the first blanking period <NUM>, the second blanking period <NUM> and the third blanking period <NUM> are illustrated as being shorter than one cardiac cycle, with a cardiac cycle being defined as a time period between successive R-waves. In some instances, it is contemplated that the duration of a particular blanking period may be adjusted. In some cases, each blanking period <NUM>, <NUM>, <NUM> may have the same time duration. In some cases, for example, the blanking period <NUM>, <NUM>, <NUM> may each extend over at least <NUM> percent of a cardiac cycle, but less than an entire cardiac cycle. Each of the blanking period <NUM>, <NUM>, <NUM> may extend over at least <NUM> percent of a cardiac cycle, but less than an entire cardiac cycle. Each of the blanking period <NUM>, <NUM>, <NUM> may extend over at least <NUM> percent, <NUM> percent, <NUM> percent or more or less of a cardiac cycle. In some cases, as illustrated in <FIG>, a blanking period <NUM> follows the R-wave <NUM> and extends to a point beyond the next successive R-wave <NUM>.

<FIG> provides a schematic illustration of a redundant message that may be transmitted to the LCP <NUM>, <NUM> by the ICD <NUM>, <NUM>. In the example shown, a R-wave <NUM> indicates a start of an LCP blanking period <NUM>. The duration of the LCP blanking period <NUM> may fall within a portion of a cardiac cycle or may extend over more than one cardiac cycle. The SICD may be seen as providing a redundant transmission <NUM> of a message and/or instruction to the LCP. The redundant transmission <NUM> may be seen as having a first message <NUM> and a second message <NUM> separated by a pause <NUM>. As illustrated, each of the first message <NUM> and the second message <NUM> include a series of pulses, pings, or chirps defining a short time frame, a long time frame, a short time frame therebetween. It will be appreciated that this is merely illustrative, as the message may include any number of pulses, pings or chirps, defining any number of short, long or other time frames therebetween. As can be seen, the second message <NUM> is the same as the first message <NUM>, and has the same pattern of pulses, pings or chirps. That is, the second message <NUM> is redundant to the first message <NUM>.

In some cases, and as shown in <FIG>, the same message(s) may be rebroadcast during each of two (or more) heat beats. This may help increase the time between redundant messages, and thus may allow for physiological changes that occur over longer time periods than just one heartbeat.

<FIG> depicts another illustrative leadless cardiac pacemaker (LCP) that may be implanted into a patient and may operate to deliver appropriate therapy to the heart, such as to deliver anti-tachycardia pacing (ATP) therapy, cardiac resynchronization therapy (CRT), bradycardia therapy, and/or the like. As can be seen in <FIG>, the LCP <NUM> may be a compact device with all components housed within the or directly on a housing <NUM>. In some cases, the LCP <NUM> may be considered as being an example of the LCP <NUM> (<FIG>) or the LCP <NUM> (<FIG>). In the example shown in <FIG>, the LCP <NUM> may include a communication module <NUM>, a pulse generator module <NUM>, an electrical sensing module <NUM>, a mechanical sensing module <NUM>, a processing module <NUM>, a battery <NUM>, and an electrode arrangement <NUM>. The LCP <NUM> may include more or less modules, depending on the application.

The communication module <NUM> may be configured to communicate with devices such as sensors, other medical devices such as an SICD, and/or the like, that are located externally to the LCP <NUM>. Such devices may be located either external or internal to the patient's body. Irrespective of the location, external devices (i.e. external to the LCP <NUM> but not necessarily external to the patient's body) can communicate with the LCP <NUM> via communication module <NUM> to accomplish one or more desired functions. For example, the LCP <NUM> may communicate information, such as sensed electrical signals, data, instructions, messages, R-wave detection markers, etc., to an external medical device (e.g. SICD and/or programmer) through the communication module <NUM>. The external medical device may use the communicated signals, data, instructions, messages, R-wave detection markers, etc., to perform various functions, such as determining occurrences of arrhythmias, delivering electrical stimulation therapy, storing received data, and/or performing any other suitable function. The LCP <NUM> may additionally receive information such as signals, data, instructions and/or messages from the external medical device through the communication module <NUM>, and the LCP <NUM> may use the received signals, data, instructions and/or messages to perform various functions, such as determining occurrences of arrhythmias, delivering electrical stimulation therapy, storing received data, and/or performing any other suitable function. The communication module <NUM> may be configured to use one or more methods for communicating with external devices For example, the communication module <NUM> may communicate via radiofrequency (RF) signals, inductive coupling, optical signals, acoustic signals, conducted communication signals, and/or any other signals suitable for communication.

In the example shown in <FIG>, the pulse generator module <NUM> may be electrically connected to the electrodes <NUM>. In some examples, the LCP <NUM> may additionally include electrodes <NUM>'. In such examples, the pulse generator <NUM> may also be electrically connected to the electrodes <NUM>'. The pulse generator module <NUM> may be configured to generate electrical stimulation signals. For example, the pulse generator module <NUM> may generate and deliver electrical stimulation signals by using energy stored in the battery <NUM> within the LCP <NUM> and deliver the generated electrical stimulation signals via the electrodes <NUM> and/or <NUM>'. Alternatively, or additionally, the pulse generator <NUM> may include one or more capacitors, and the pulse generator <NUM> may charge the one or more capacitors by drawing energy from the battery <NUM>. The pulse generator <NUM> may then use the energy of the one or more capacitors to deliver the generated electrical stimulation signals via the electrodes <NUM> and/or <NUM>'. In at least some examples, the pulse generator <NUM> of the LCP <NUM> may include switching circuitry to selectively connect one or more of the electrodes <NUM> and/or <NUM>' to the pulse generator <NUM> in order to select which of the electrodes <NUM>/<NUM>' (and/or other electrodes) the pulse generator <NUM> delivers the electrical stimulation therapy. The pulse generator module <NUM> may generate and deliver electrical stimulation signals with particular features or in particular sequences in order to provide one or multiple of a number of different stimulation therapies. For example, the pulse generator module <NUM> may be configured to generate electrical stimulation signals to provide electrical stimulation therapy to combat bradycardia, tachycardia, cardiac synchronization, bradycardia arrhythmias, tachycardia arrhythmias, fibrillation arrhythmias, cardiac synchronization arrhythmias and/or to produce any other suitable electrical stimulation therapy. Some more common electrical stimulation therapies include anti-tachycardia pacing (ATP) therapy, cardiac resynchronization therapy (CRT), and cardioversion/defibrillation therapy. In some cases, the pulse generator <NUM> may provide a controllable pulse energy. In some cases, the pulse generator <NUM> may allow the controller to control the pulse voltage, pulse width, pulse shape or morphology, and/or any other suitable pulse characteristic.

In some examples, the LCP <NUM> may include an electrical sensing module <NUM>, and in some cases, a mechanical sensing module <NUM>. The electrical sensing module <NUM> may be configured to sense the cardiac electrical activity of the heart. For example, the electrical sensing module <NUM> may be connected to the electrodes <NUM>/<NUM>', and the electrical sensing module <NUM> may be configured to receive cardiac electrical signals conducted through the electrodes <NUM>/<NUM>'. The cardiac electrical signals may represent local information from the chamber in which the LCP <NUM> is implanted. For instance, if the LCP <NUM> is implanted within a ventricle of the heart (e.g. RV, LV), cardiac electrical signals sensed by the LCP <NUM> through the electrodes <NUM>/<NUM>' may represent ventricular cardiac electrical signals. In some cases, the LCP <NUM> may be configured to detect cardiac electrical signals from other chambers (e.g. far field), such as the P-wave from the atrium.

The mechanical sensing module <NUM> may include one or more sensors, such as an accelerometer, a pressure sensor, a heart sound sensor, a blood-oxygen sensor, a chemical sensor, a temperature sensor, a flow sensor and/or any other suitable sensors that are configured to measure one or more mechanical/chemical parameters of the patient. Both the electrical sensing module <NUM> and the mechanical sensing module <NUM> may be connected to a processing module <NUM>, which may provide signals representative of the sensed mechanical parameters. Although described with respect to <FIG> as separate sensing modules, in some cases, the electrical sensing module <NUM> and the mechanical sensing module <NUM> may be combined into a single sensing module, as desired.

The electrodes <NUM>/<NUM>' can be secured relative to the housing <NUM> but exposed to the tissue and/or blood surrounding the LCP <NUM>. In some cases, the electrodes <NUM> may be generally disposed on either end of the LCP <NUM> and may be in electrical communication with one or more of the modules <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. The electrodes <NUM>/<NUM>' may be supported by the housing <NUM>, although in some examples, the electrodes <NUM>/<NUM>' may be connected to the housing <NUM> through short connecting wires such that the electrodes <NUM>/<NUM>' are not directly secured relative to the housing <NUM>. In examples where the LCP <NUM> includes one or more electrodes <NUM>', the electrodes <NUM>' may in some cases be disposed on the sides of the LCP <NUM>, which may increase the number of electrodes by which the LCP <NUM> may sense cardiac electrical activity, deliver electrical stimulation and/or communicate with an external medical device. The electrodes <NUM>/<NUM>' can be made up of one or more biocompatible conductive materials such as various metals or alloys that are known to be safe for implantation within a human body. In some instances, the electrodes <NUM>/<NUM>' connected to the LCP <NUM> may have an insulative portion that electrically isolates the electrodes <NUM>/<NUM>' from adjacent electrodes, the housing <NUM>, and/or other parts of the LCP <NUM>. In some cases, one or more of the electrodes <NUM>/<NUM>' may be provided on a tail (not shown) that extends away from the housing <NUM>.

The processing module <NUM> can be configured to control the operation of the LCP <NUM>. For example, the processing module <NUM> may be configured to receive electrical signals from the electrical sensing module <NUM> and/or the mechanical sensing module <NUM>. Based on the received signals, the processing module <NUM> may determine, for example, abnormalities in the operation of the heart H. Based on any determined abnormalities, the processing module <NUM> may control the pulse generator module <NUM> to generate and deliver electrical stimulation in accordance with one or more therapies to treat the determined abnormalities. The processing module <NUM> may further receive information from the communication module <NUM>. In some examples, the processing module <NUM> may use such received information to help determine whether an abnormality is occurring, determine a type of abnormality, and/or to take particular action in response to the information. The processing module <NUM> may additionally control the communication module <NUM> to send/receive information to/from other devices.

In some examples, the processing module <NUM> may include a pre-programmed chip, such as a very-large-scale integration ("VLSI) chip and/or an application specific integrated circuit (ASIC). In such embodiments, the chip may be pre-programmed with control logic in order to control the operation of the LCP <NUM>. By using a pre-programmed chip, the processing module <NUM> may use less power than other programmable circuits (e.g. general purpose programmable microprocessors) while still being able to maintain basic functionality, thereby potentially increasing the battery life of the LCP <NUM>. In other examples, the processing module <NUM> may include a programmable microprocessor. Such a programmable microprocessor may allow a user to modify the control logic of the LCP <NUM> even after implantation, thereby allowing for greater flexibility of the LCP <NUM> than when using a pre-programmed ASIC. In some examples, the processing module <NUM> may further include a memory, and the processing module <NUM> may store information on and read information from the memory. In other examples, the LCP <NUM> may include a separate memory (not shown) that is in communication with the processing module <NUM>, such that the processing module <NUM> may read and write information to and from the separate memory.

The battery <NUM> may provide power to the LCP <NUM> for its operations. In some examples, the battery <NUM> may be a non-rechargeable lithium-based battery. In other examples, a non-rechargeable battery may be made from other suitable materials, as desired. Because the LCP <NUM> is an implantable device, access to the LCP <NUM> may be limited after implantation. Accordingly, it is desirable to have sufficient battery capacity to deliver therapy over a period of treatment such as days, weeks, months, years or even decades. In some instances, the battery <NUM> may a rechargeable battery, which may help increase the useable lifespan of the LCP <NUM>. In still other examples, the battery <NUM> may be some other type of power source, as desired.

To implant the LCP <NUM> inside a patient's body, an operator (e.g., a physician, clinician, etc.), may fix the LCP <NUM> to the cardiac tissue of the patient's heart. To facilitate fixation, the LCP <NUM> may include one or more anchors <NUM>. The anchor <NUM> may include any one of a number of fixation or anchoring mechanisms. For example, the anchor <NUM> may include one or more pins, staples, threads, screws, helix, tines, and/or the like. In some examples, although not shown, the anchor <NUM> may include threads on its external surface that may run along at least a partial length of the anchor <NUM>. The threads may provide friction between the cardiac tissue and the anchor to help fix the anchor <NUM> within the cardiac tissue. In other examples, the anchor <NUM> may include other structures such as barbs, spikes, or the like to facilitate engagement with the surrounding cardiac tissue.

<FIG> depicts an example of another or second medical device (MD) <NUM>, which may be used in conjunction with the LCP <NUM> (<FIG>) in order to detect and/or treat cardiac abnormalities. In some cases, the MD <NUM> may be considered as an example of the ICD <NUM> (<FIG>) or the SICD <NUM> (<FIG>). In the example shown, the MD <NUM> may include a communication module <NUM>, a pulse generator module <NUM>, an electrical sensing module <NUM>, a mechanical sensing module <NUM>, a processing module <NUM>, and a battery <NUM>. Each of these modules may be similar to the modules <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> of LCP <NUM>. Additionally, the battery <NUM> may be similar to the battery <NUM> of the LCP <NUM>. In some examples, however, the MD <NUM> may have a larger volume within the housing <NUM>. In such examples, the MD <NUM> may include a larger battery and/or a larger processing module <NUM> capable of handling more complex operations than the processing module <NUM> of the LCP <NUM>.

While it is contemplated that the MD <NUM> may be another leadless device such as shown in <FIG>, in some instances the MD <NUM> may include leads such as leads <NUM>. The leads <NUM> may include electrical wires that conduct electrical signals between the electrodes <NUM> and one or more modules located within the housing <NUM>. In some cases, the leads <NUM> may be connected to and extend away from the housing <NUM> of the MD <NUM>. In some examples, the leads <NUM> are implanted on, within, or adjacent to a heart of a patient. The leads <NUM> may contain one or more electrodes <NUM> positioned at various locations on the leads <NUM>, and in some cases at various distances from the housing <NUM>. Some leads <NUM> may only include a single electrode <NUM>, while other leads <NUM> may include multiple electrodes <NUM>. Generally, the electrodes <NUM> are positioned on the leads <NUM> such that when the leads <NUM> are implanted within the patient, one or more of the electrodes <NUM> are positioned to perform a desired function. In some cases, the one or more of the electrodes <NUM> may be in contact with the patient's cardiac tissue. In some cases, the one or more of the electrodes <NUM> may be positioned subcutaneously and outside of the patient's heart. In some cases, the electrodes <NUM> may conduct intrinsically generated electrical signals to the leads <NUM>, e.g. signals representative of intrinsic cardiac electrical activity. The leads <NUM> may, in turn, conduct the received electrical signals to one or more of the modules <NUM>, <NUM>, <NUM>, and <NUM> of the MD <NUM>. In some cases, the MD <NUM> may generate electrical stimulation signals, and the leads <NUM> may conduct the generated electrical stimulation signals to the electrodes <NUM>. The electrodes <NUM> may then conduct the electrical signals and delivery the signals to the patient's heart (either directly or indirectly).

The mechanical sensing module <NUM>, as with the mechanical sensing module <NUM>, may contain or be electrically connected to one or more sensors, such as accelerometers, acoustic sensors, blood pressure sensors, heart sound sensors, blood-oxygen sensors, and/or other sensors which are configured to measure one or more mechanical/chemical parameters of the heart and/or patient. In some examples, one or more of the sensors may be located on the leads <NUM>, but this is not required. In some examples, one or more of the sensors may be located in the housing <NUM>.

While not required, in some examples, the MD <NUM> may be an implantable medical device. In such examples, the housing <NUM> of the MD <NUM> may be implanted in, for example, a transthoracic region of the patient. The housing <NUM> may generally include any of a number of known materials that are safe for implantation in a human body and may, when implanted, hermetically seal the various components of the MD <NUM> from fluids and tissues of the patient's body.

In some cases, the MD <NUM> may be an implantable cardiac pacemaker (TCP). In this example, the MD <NUM> may have one or more leads, for example the leads <NUM>, which are implanted on or within the patient's heart. The one or more leads <NUM> may include one or more electrodes <NUM> that are in contact with cardiac tissue and/or blood of the patient's heart. The MD <NUM> may be configured to sense intrinsically generated cardiac electrical signals and determine, for example, one or more cardiac arrhythmias based on analysis of the sensed signals. The MD <NUM> may be configured to deliver CRT, ATP therapy, bradycardia therapy, and/or other therapy types via the leads <NUM> implanted within the heart. In some examples, the MD <NUM> may additionally be configured provide defibrillation therapy.

In some instances, the MD <NUM> may be an implantable cardioverter-defibrillator (ICD). In such examples, the MD <NUM> may include one or more leads implanted within a patient's heart. "The MD <NUM> may also be configured to sense cardiac electrical signals, determine occurrences of tachyarrhythmias based on the sensed signals, and may be configured to deliver defibrillation therapy in response to determining an occurrence of a tachyarrhythmia. In other examples, the MD <NUM> may be a subcutaneous implantable cardioverter-defibrillator (S-ICD). In examples where the MD <NUM> is an S-ICD, one of the leads <NUM> may be a subcutaneously implanted lead. In at least some examples where the MD <NUM> is an S-ICD, the MD <NUM> may include only a single lead which is implanted subcutaneously, but this is not required. In some instances, the lead(s) may have one or more electrodes that are placed subcutaneously and outside of the chest cavity. In other examples, the lead(s) may have one or more electrodes that are placed inside of the chest cavity, such as just interior of the sternum but outside of the heart H.

In some examples, the MD <NUM> may not be an implantable medical device. Rather, the MD <NUM> may be a device external to the patient's body, and may include skin-electrodes that are placed on a patient's body. In such examples, the MD <NUM> may be able to sense surface electrical signals (e.g. cardiac electrical signals that are generated by the heart or electrical signals generated by a device implanted within a patient's body and conducted through the body to the skin). In such examples, the MD <NUM> may be configured to deliver various types of electrical stimulation therapy, including, for example, defibrillation therapy.

<FIG> illustrates an example of a medical device system and a communication pathway through which multiple medical devices <NUM>, <NUM>, <NUM>, and/or <NUM> may communicate. In the example shown, the medical device system <NUM> may include LCPs <NUM> and <NUM>, external medical device <NUM>, and other sensors/devices <NUM>. The external device <NUM> may be any of the devices described previously with respect to the MD <NUM>. Other sensors/devices <NUM> may also be any of the devices described previously with respect to the MD <NUM>. In some instances, other sensors/devices <NUM> may include a sensor, such as an accelerometer, an acoustic sensor, a blood pressure sensor, or the like. In some cases, other sensors/devices <NUM> may include an external programmer device that may be used to program one or more devices of the system <NUM>.

Various devices of the system <NUM> may communicate via communication pathway <NUM>. The communication pathway <NUM> may include one or a number of different communication paths and/or a number of different communication modes. The communication pathway <NUM> may also include one or more distinct communication vectors. In some cases, for example, the LCPs <NUM> and/or <NUM> may sense intrinsic cardiac electrical signals and may communicate such signals to one or more other devices <NUM>/<NUM>, <NUM>, and <NUM> of the system <NUM> via communication pathway <NUM>. In one example, one or more of the devices <NUM>/<NUM> may receive such signals and, based on the received signals, determine an occurrence of an arrhythmia. In some cases, the device or devices <NUM>/<NUM> may communicate such determinations to one or more other devices <NUM> and <NUM> of the system <NUM>. In some cases, one or more of the devices <NUM>/<NUM>, <NUM>, and <NUM> of the system <NUM> may take action based on the communicated determination of an arrhythmia, such as by delivering a suitable electrical stimulation to the heart of the patient. It is contemplated that the communication pathway <NUM> may communicate using RF signals, inductive coupling, optical signals, acoustic signals, or any other signals suitable for communication. Additionally, in at least some examples, device communication pathway <NUM> may include multiple signal types. For instance, other sensors/device <NUM> may communicate with the external device <NUM> using a first signal type (e.g. RF communication) but communicate with the LCPs <NUM>/<NUM> using a second signal type (e.g. conducted communication). Further, in some examples, communication between devices may be limited. For instance, as described above, in some examples, the LCPs <NUM>/<NUM> may communicate with the external device <NUM> only through other sensors/devices <NUM>, where the LCPs <NUM>/<NUM> send signals to other sensors/devices <NUM>, and other sensors/devices <NUM> relay the received signals to the external device <NUM>.

In some cases, the communication pathway <NUM> may include conducted communication. Accordingly, devices of the system <NUM> may have components that allow for such conducted communication. For instance, the devices of system <NUM> may be configured to transmit conducted communication signals (e.g. current and/or voltage pulses) into the patient's body via one or more electrodes of a transmitting device, and may receive the conducted communication signals (e.g. pulses) via one or more electrodes of a receiving device. The patient's body may "conduct" the conducted communication signals (e.g. pulses) from the one or more electrodes of the transmitting device to the electrodes of the receiving device in the system <NUM>. In such examples, the delivered conducted communication signals (e.g. pulses) may differ from pacing or other therapy signals. For example, the devices of the system <NUM> may deliver electrical communication pulses at an amplitude /pulse width that is sub-capture threshold to the heart. Although, in some cases, the amplitude/pulse width of the delivered electrical communication pulses may be above the capture threshold of the heart, but may be delivered during a blanking period of the heart (e.g. refractory period) and/or may be incorporated in or modulated onto a pacing pulse, if desired.

Delivered electrical communication pulses may be modulated in any suitable manner to encode communicated information. In some cases, the communication pulses may be pulse width modulated or amplitude modulated. Alternatively, or in addition, the time between pulses may be modulated to encode desired information. In some cases, conducted communication pulses may be voltage pulses, current pulses, biphasic voltage pulses, biphasic current pulses, or any other suitable electrical pulse as desired.

<FIG> shows an illustrative medical device system. In <FIG>, an LCP <NUM> is shown fixed to the interior of the left ventricle of the heart <NUM>, and a pulse generator <NUM> is shown coupled to a lead <NUM> having one or more electrodes 408a-408c. In some cases, the pulse generator <NUM> may be part of a subcutaneous implantable cardioverter-defibrillator (S-ICD), and the one or more electrodes 408a-408c may be positioned subcutaneously. In some cases, the one or more electrodes 408a-408c may be placed inside of the chest cavity but outside of the heart, such as just interior of the sternum. In some cases, the LCP <NUM> may communicate with the subcutaneous implantable cardioverter-defibrillator (S-ICD). In some cases, the lead <NUM> and/or pulse generator <NUM> may include an accelerometer <NUM> that may, for example, be configured to sense vibrations that may be indicative of heart sounds.

In some cases, the LCP <NUM> may be in the right ventricle, right atrium, left ventricle or left atrium of the heart, as desired. In some cases, more than one LCP <NUM> may be implanted. For example, one LCP may be implanted in the right ventricle and another may be implanted in the right atrium. In another example, one LCP may be implanted in the right ventricle and another may be implanted in the left ventricle. In yet another example, one LCP may be implanted in each of the chambers of the heart.

Claim 1:
An implantable medical device, hereinafter IMD, configured to pace a patient's heart, the IMD disposable within a chamber of the patient's heart, the IMD comprising:
a housing (<NUM>);
a plurality of electrodes (<NUM>, <NUM>);
a controller (<NUM>) housed by the housing (<NUM>) and operably coupled to the plurality of electrodes (<NUM>, <NUM>), the controller (<NUM>) configured to:
generate and deliver electrical pulses via a pair of the plurality of electrodes (<NUM>, <NUM>);
receive messages transmitted by conducted communication from a remote implantable medical device , hereinafter remote IMD, via a pair of the plurality of electrodes (<NUM>, <NUM>);
receive cardiac signals via a pair of the plurality of electrodes (<NUM>, <NUM>); and
the controller (<NUM>) is configured to receive at least one of a plurality of transmissions of the same message transmitted by conducted communication by the remote IMD during a cardiac cycle, and
characterised in that
when more than one of the plurality of transmissions of the same message are successfully received by the controller (<NUM>) during the cardiac cycle, the controller (<NUM>) is configured to treat the more than one successfully received transmissions of the same message as one message by only executing the instruction of one of the successfully received messages.