Patent Description:
Various types of implantable devices are utilized today for monitoring physiologic activity and potentially delivering therapy. Some types of implantable medical devices are "leadless" and instead include electrodes directly on the housing to sense and deliver therapy. One example of an implantable medical device (IMD), that does not provide therapy, is an implantable cardiac monitor or implantable cardiac monitoring (ICM) device, which is very small in size as compared to other implantable medical devices such as pacemakers, implantable cardioverter defibrillators, cardiac rhythm management devices and the like. The ICM device includes a header that holds an antenna for wireless communications (e.g., an RF or Bluetooth Low Energy antenna). The header also houses a sensing electrode to monitor physiologic activity of the patient. The header may be pre-formed and then attached to an end of a housing or case of the ICM device.

However, an opportunity remains to improve upon conventional ICM device designs. For example, the small size enables the ICM device to move, such as rotate, within a subcutaneous pocket of the patient, which changes the position of the sensing electrode within the header relative to the body of the patient. Shifts in the position and/or orientation of the ICM device relative to the patient body can affect the sensitivity of the sensing electrode to cardiac signals. Cardiac monitoring performance may suffer if the sensitivity changes, and the ICM device may require recalibration. Furthermore, the movement may cause the header electrode to at least periodically separate from patient tissue with which the header electrode was in persistent contact, and the loss of contact may significantly diminish cardiac sensing capability. The ICM device may falsely interpret the lack of cardiac signals, when the electrode is separated from the tissue, as a period of no intrinsic heartbeat in the patient. Even if such false pause episode does not occur, the diminished sensing capability could reduce the quality of the sensing data generated by the ICM device, such as the quality of R wave sensing in an electrogram (EGM).

A need remains for an implantable medical device that affords reliable cardiac sensing and sensitivity even as the posture of the patient changes and the implantable medical device moves in the subcutaneous pocket within the patient.

<CIT> discloses a method and medical monitoring device for determining the occurrence of a premature ventricular contraction that includes sensing a cardiac signal and determining R-waves in response to the sensed cardiac signal, determining RR intervals between the determined R-waves, determining whether a first interval criteria is satisfied in response to the determined intervals, determining a correlation between the determined R-waves, determining whether a first correlation criteria is satisfied in response to the determined correlation, and determining the premature ventricular contraction is occurring in response to the first interval criteria and the first correlation criteria being satisfied.

Further embodiments of the invention are defined in the dependent claims.

In one or more embodiments, an implantable medical device is provided that includes a header configured to be mounted to an end of a device housing that contains an electronics module therein. The header includes an antenna, a sensing electrode, and a header body that at least partially surrounds the antenna and the sensing electrode. The sensing electrode includes a first body portion, a second body portion, and a bridge portion that mechanically and electrically connects the first and second body portions. The first body portion is at least partially exposed to an external environment along a first side of the header, and the second body portion is at least partially exposed to the external environment along a second side of the header that is different from the first side. The first side of the header is defined in part by the header body and in part by the first body portion of the sensing electrode. The part of the first side defined by the first body portion protrudes outward relative to the part defined by the header body.

Optionally, the first side of the header is opposite the second side of the header. Optionally, the first body portion has a planar outer surface that is exposed to the external environment, and the second body portion has a planar outer surface that is exposed to the external environment. The planar outer surfaces of the first and second body portions may extend in parallel planes. Optionally, the header includes a curved distal surface extending along a thickness of the header from the first side to the second side. Respective distal edges of the first body portion and the second body portion may be arcuate and may conform to a shape of the curved distal surface.

Optionally, the header body comprises a dielectric material in which the antenna and the sensing electrode are embedded. Optionally, each of the first body portion and the second body portion has a respective flange and a platform that is raised relative to the flange. The header body may envelop the flange and an outer surface of the platform may project from the header body. Perimeter edges of the platform may be beveled or rounded. Optionally, each of the first body portion and the second body portion has bent tabs projecting into an interior of the header. The bent tabs may be encased within the header body to secure the first and second body portions in place within the header. Optionally, the header body defines a suture opening that extends through an entire thickness of the header body.

Optionally, the implantable medical device also includes a feedthrough assembly that abuts a mounting end of the header at an interface and attaches to the end of the device housing. The header body may comprise a dielectric material that covers the interface and surrounds at least a segment of the feedthrough assembly. Optionally, the bridge portion of the sensing electrode is mechanically attached to a conductor to electrically connect the conductor to the sensing electrode. The conductor may project from a mounding end of the header through the end of the device housing to the electronics module. Optionally, the sensing electrode is a monolithic structure, and the first and second body portions are integrally connected to different ends of the bridge portion.

In one or more embodiments, a method to provide an implantable medical device is presented. The method includes providing a header by inserting a sensing electrode and an antenna within a mold. The sensing electrode includes a first body portion, a second body portion, and a bridge portion that mechanically and electrically connects the first and second body portions. The header is also provided by flowing a dielectric material into the mold to at least partially surround the sensing electrode and the antenna and form a header body of the header upon solidification of the dielectric material. The sensing electrode is inserted in the mold, and the dielectric material is flowed into the mold such that the first body portion is at least partially exposed to an external environment along a first side of the header, and the second body portion is at least partially exposed to the external environment along a second side of the header that is different from the first side. The first side of the header is defined in part by the header body and in part by the first body portion of the sensing electrode. The part of the first side defined by the first body portion protrudes outward relative to the part defined by the header body. The header is also provided by removing the header body with the sensing electrode and the antenna from the mold. The method also includes mounting the header to an end of a device housing that contains an electronics module therein.

Optionally, providing the header includes mechanically securing conductors of a feedthrough assembly to the bridge portion of the sensing electrode and the antenna, and inserting a base of the feedthrough assembly at least partially into the mold prior to flowing the dielectric material into the mold. The dielectric material may be flowed into the mold to at least partially surround the base of the feedthrough assembly for forming the header body in-situ on the base.

Optionally, each of the first body portion and the second body portion has a respective flange and a platform that is raised relative to the flange. The dielectric material may be flowed into the mold to envelop the flange without enveloping the platform such that an outer surface of the platform projects from the header body.

It will be readily understood that the components of the embodiments as generally described and illustrated in the Figures herein, may be arranged and designed in a wide variety of different configurations in addition to the described example embodiments. Thus, the following more detailed description of the example embodiments, as represented in the Figures, is not intended to limit the scope of the embodiments, as claimed, but is merely representative of example embodiments.

Reference throughout this specification to "one embodiment" or "an embodiment" (or the like) means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" or the like in various places throughout this specification are not necessarily all referring to the same embodiment.

In the following description, numerous specific details are provided to give a thorough understanding of embodiments. One skilled in the relevant art will recognize, however, that the various embodiments can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obfuscation. The following description is intended only by way of example, and simply illustrates certain example embodiments.

Embodiments may be implemented in connection with one or more implantable medical devices (IMDs). Non-limiting examples of IMDs include one or more of neurostimulator devices, implantable leadless monitoring and/or therapy devices, and/or alternative implantable medical devices. For example, the IMD may represent a cardiac monitoring device, leadless pacemaker, cardioverter, cardiac rhythm management device, defibrillator, neurostimulator, and the like. For example, the IMD may include one or more structural and/or functional aspects of the device(s) described in <CIT> "Neurostimulation Method And System To Treat Apnea" and <CIT> "System And Methods For Providing A Distributed Virtual Stimulation Cathode For Use With An Implantable Neurostimulation System". Additionally or alternatively, the IMD may include one or more structural and/or functional aspects of the device(s) described in <CIT> "Leadless Implantable Medical Device Having Removable And Fixed Components" and <CIT> "Leadless Neurostimulation Device And Method Including The Same" Additionally or alternatively, the IMD may include one or more structural and/or functional aspects of the device(s) described in <CIT> "Method And System For Identifying A Potential Lead Failure In An Implantable Medical Device" and <CIT> "System And Method For Selectively Communicating With An Implantable Medical Device".

<FIG> illustrates an implantable medical device (IMD) <NUM> intended for subcutaneous implantation at a site near the heart. The IMD <NUM> may provide comprehensive safe diagnostic data reports including a summary of heart rate, in order to assist physicians in diagnosis and treatment of patient conditions. By way of example, reports may include episodal diagnostics for auto trigger events, episode duration, episode count, episode date/time stamp and heart rate histograms. The IMD <NUM> may be configured to be relatively small (e.g., between <NUM>-<NUM> cc in volume) which may, among other things, reduce risk of infection during implant procedure, afford the use of a small incision, afford the use of a smaller subcutaneous pocket and the like. The small footprint may also reduce implant time and introduce less change in body image for patients.

The IMD <NUM> provides a data storage option that is simple to configure to enable physicians to prioritize data based on individual patient conditions, to capture significant events and reduce risk that unexpected events are missed. The IMD <NUM> may have programmable pre- and post-trigger event storage. For example, the IMD <NUM> may be automatically activated to store <NUM>-<NUM> seconds of activity data prior to an event of interest and/or to store <NUM>-<NUM> seconds of post event activity. Optionally, the IMD <NUM> may afford patient triggered activation in which pre-event activity data is stored, as well as post event activity data (e.g., pre-event storage of <NUM>-<NUM> minutes and post-event storage of <NUM>-<NUM> seconds). Optionally, the IMD <NUM> may afford manual (patient triggered) or automatic activation for EGM storage. Optionally, the IMD <NUM> may afford additional programming options (e.g., asystole duration, bradycardia rate, tachycardia rate, tachycardia cycle count). The amount of EGM storage may vary based upon the size of the memory.

The IMD <NUM> includes a housing <NUM> that is joined to a header <NUM>. At least one electrode <NUM> and an antenna <NUM> are provided in the header <NUM> as explained hereafter in accordance with embodiments herein. In accordance with embodiments herein, a header configuration is provided which includes a multi-sided electrode <NUM>. Multi-sided in this case refers to a single electrode <NUM> with multiple portions that extend along multiple different sides of the header <NUM> and are exposed to the tissue of the patient along each the sides. In a non-limiting example, a single electrode <NUM> may have a first body portion exposed to the tissue of the patient along a first side of the header <NUM> and a second body portion exposed to the patient tissue along a second side of the header <NUM> that is opposite the first side, such that the electrode <NUM> is effectively dual-sided with respect to the header <NUM>. The multi-sided electrode header configuration is provided to enhance and increase the contact surface area of the electrode <NUM> with tissue, relative to electrodes that are only exposed to tissue along one side. Increase the amount of surface area of the electrode <NUM> in contact with the tissue reduces the likelihood of the electrode <NUM> losing contact with the tissue and makes the IMD <NUM> less sensitive to postural changes of the patient. In effect, the IMD <NUM> becomes more robust and reliable, and the data generated is less variable.

The housing <NUM> includes one or more electrodes <NUM> that are provided on the housing <NUM> distal from the header <NUM>. The electrode(s) <NUM> may be located in various locations on the housing <NUM>. For example, when separate housing portions are provide for the electronics module and the battery, one or more electrodes may be located on the battery (e.g., the battery housing). Numerous configurations of electrode arrangements are possible.

The housing <NUM> includes various other components such as sensing electronics for receiving signals from the electrodes, a microprocessor for processing the signals in accordance with algorithms (e.g., an atrial fibrillation (AF) detection algorithm), a memory for temporary storage of electrograms, a device memory for long-term storage of electrograms upon certain triggering events, such as AF detection, sensors for detecting patient activity and a battery for powering components.

The IMD device <NUM> senses far field, subcutaneous electrograms, processes the electrograms to detect arrhythmias and automatically records the electrograms in memory for subsequent transmission through the antenna <NUM> to an external device <NUM>. Electrogram processing and arrhythmia detection is provided for, at least in part, by algorithms embodied in the microprocessor. In one configuration, the monitoring device is operative to detect AF.

<FIG> shows a block diagram of an exemplary IMD <NUM> that is configured to be implanted into the patient. The IMD <NUM> may be implemented to monitor ventricular activity alone, or both ventricular and atrial activity through sensing circuitry. The IMD <NUM> has a device housing <NUM> to hold the electronic/computing components. The housing <NUM> (which is often referred to as the "can", "case", "encasing", or "case electrode") may be programmable to act as an electrode for certain sensing modes. The housing <NUM> further includes a connector (not shown) with at least one terminal <NUM> and preferably a second terminal <NUM>. The terminals <NUM>, <NUM> may be coupled to sensing electrodes that are provided upon or immediately adjacent the housing <NUM>. For example, the terminal <NUM> may be coupled to the sensing electrode <NUM> in the header <NUM> (shown in <FIG>). The other terminal <NUM> may be coupled to a sensing electrode integrated into the device housing <NUM> or may be coupled to the housing itself which can operate as an electrode when formed of an electrically conductive material, such as a metal or metal alloy. Optionally, more than two terminals <NUM>, <NUM> may be provided in order to support more than two sensing electrodes to support a true bipolar sensing scheme using the housing as a reference electrode.

In at least some embodiments, the IMD <NUM> is configured to be placed subcutaneously utilizing a minimally invasive approach. Subcutaneous electrodes are provided on the IMD <NUM> to simplify the implant procedure and eliminate a need for a transvenous lead system. For example, the IMD <NUM> may be leadless, such that the header <NUM> does not have any ports for connecting to leads. The sensing electrodes may be located on opposite sides of the device and designed to provide robust episode detection through consistent contact at a sensor - tissue interface. The IMD <NUM> may be configured to be activated by the patient or automatically activated, in connection with recording subcutaneous ECG signals.

The IMD <NUM> includes a programmable microcontroller <NUM> that controls various operations of the IMD <NUM>, including cardiac monitoring. Microcontroller <NUM> includes a microprocessor (or equivalent control circuitry), RAM and/or ROM memory, logic and timing circuitry, state machine circuitry, and I/O circuitry. The microcontroller <NUM> also performs the operations described herein in connection with collecting cardiac activity data and analyzing the cardiac activity data to identify episodes.

A switch <NUM> is optionally provided to allow selection of different electrode configurations under the control of the microcontroller <NUM>. The electrode configuration switch <NUM> may include multiple switches for connecting the desired electrodes to the appropriate I/O circuits, thereby facilitating electrode programmability. For example, the switch <NUM> may be utilized to select between electrodes <NUM> provided on opposite sides of the housing <NUM>, such as based upon the orientation of the IMD <NUM> relative to a physiologic area of interest. The switch <NUM> is controlled by a control signal <NUM> from the microcontroller <NUM>. Optionally, the switch <NUM> may be omitted and the I/O circuits directly connected to the housing electrode and a second electrode.

Microcontroller <NUM> includes an arrhythmia detector <NUM>. The arrhythmia detector <NUM> is configured to analyze cardiac activity data to identify potential AF episodes as well as other arrhythmias (e.g., Tachcardias, Bradycardias, Asystole, etc.). By way of example, the arrhythmia detector <NUM> may implement an AF detection algorithm as described in <CIT> "Device And Method For Detecting Atrial Fibrillation". In accordance with at least some embodiments, when a potential AF episode is detected, the detector is utilized to determine whether the episode is in fact an AF episode or instead another episode. Although not shown, the microcontroller <NUM> may further include other dedicated circuitry and/or firmware/software components that assist in monitoring various conditions of the patient's heart and managing pacing therapies.

The IMD <NUM> is further equipped with a communication modem (modulator/demodulator) <NUM> to enable wireless communication. In one implementation, the communication modem <NUM> uses high frequency modulation, for example using RF, Bluetooth, Bluetooth Low Energy and other telemetry protocols. The signals are transmitted in a high frequency range and will travel through the body tissue in fluids without stimulating the heart or being felt by the patient. The communication modem <NUM> may be implemented in hardware as part of the microcontroller <NUM>, or as software/firmware instructions programmed into and executed by the microcontroller <NUM>. Alternatively, the modem <NUM> may reside separately from the microcontroller as a standalone component. The modem <NUM> facilitates data retrieval from a remote monitoring network. The modem <NUM> enables timely and accurate data transfer directly from the patient to an electronic device utilized by a physician.

The IMD <NUM> further includes an analog-to-digital A/D data acquisition system (DAS) <NUM> coupled to one or more electrodes via the switch <NUM> to sample cardiac signals across any pair of desired electrodes. The DAS <NUM> is configured to acquire cardiac electrogram (EGM) 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 <NUM> (e.g., a programmer, local transceiver, or a diagnostic system analyzer). The DAS <NUM> is controlled by a control signal <NUM> from the microcontroller <NUM>. The EGM signals are utilized as the cardiac activity data that is analyzed for potential episodes.

By way of example, the external device <NUM> may represent a portable smartphone, tablet device, bedside monitor installed in a patient's home and the like. The external device <NUM> is utilized to communicate with the IMD <NUM> while the patient is at work, home, in bed or asleep. The external device <NUM> may be a programmer used in the clinic to interrogate the device, retrieve data and program detection criteria and other features. The external device <NUM> may be a device that can be coupled over a network (e.g., the Internet) to a remote monitoring service, medical network and the like. The external device <NUM> facilitates access by physicians to patient data as well as permitting the physician to review real-time ECG signals while being collected by the IMD <NUM>.

The IMD <NUM> includes sensing circuitry <NUM> selectively coupled to one or more electrodes <NUM> that perform sensing operations, through the switch <NUM> to detect cardiac activity data indicative of cardiac activity. The sensing circuitry <NUM> 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. In one embodiment, switch <NUM> may be used to determine the sensing polarity of the cardiac signal by selectively closing the appropriate switches.

The output of the sensing circuitry <NUM> is connected to the microcontroller <NUM> which, in turn, determines when to store the cardiac activity data (digitized by the A/D data acquisition system <NUM>) in the memory <NUM>. For example, the microcontroller <NUM> may only store the cardiac activity data (from the A/D data acquisition system <NUM>) in the memory <NUM> when a potential AF episode is detected. The sensing circuitry <NUM> receives a control signal <NUM> from the microcontroller <NUM> 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 example of <FIG>, a single sensing circuit <NUM> is illustrated. Optionally, the IMD <NUM> may include multiple sensing circuits, similar to sensing circuit <NUM>, where each sensing circuit is coupled to two or more electrodes and controlled by the microcontroller <NUM> to sense electrical activity detected at the corresponding two or more electrodes. The sensing circuit <NUM> may operate in a unipolar sensing configuration (e.g., housing <NUM> to electrode) or in a bipolar sensing configuration (e.g., between electrodes referenced to the housing electrode). Optionally, the sensing circuit <NUM> may be removed entirely and the microcontroller <NUM> perform the operations described herein based upon the EGM signals from the A/D data acquisition system <NUM> directly coupled to the electrodes <NUM>.

The microcontroller <NUM> is coupled to a memory <NUM> by a suitable data/address bus <NUM>. The programmable operating parameters used by the microcontroller <NUM> are stored in memory <NUM> and used to customize the operation of the IMD <NUM> to suit the needs of a particular patient. Such operating parameters define, for example, detection rate thresholds, sensitivity, automatic features, arrhythmia detection criteria, activity sensing or other physiological sensors, and electrode polarity, etc..

In addition, the memory <NUM> stores the cardiac activity data, as well as the markers and other data content associated with detection of episodes. The operating parameters of the IMD <NUM> may be non-invasively programmed into the memory <NUM> through a telemetry circuit <NUM> in telemetric communication via communication link <NUM> with the external device <NUM>. The telemetry circuit <NUM> allows intracardiac electrograms and status information relating to the operation of the IMD <NUM> (as contained in the microcontroller <NUM> or memory <NUM>) to be sent to the external device <NUM> through the established communication link <NUM>. In accordance with embodiments herein, the telemetry circuit <NUM> conveys the cardiac activity data, markers and other information related to AF episodes.

The IMD <NUM> may further include magnet detection circuitry (not shown), coupled to the microcontroller <NUM>, to detect when a magnet is placed over the IMD. A magnet may be used by a clinician to perform various test functions of the IMD <NUM><NUM> and/or to signal the microcontroller <NUM> that the external device <NUM> is in place to receive or transmit data to the microcontroller <NUM> through the telemetry circuits <NUM>.

The IMD <NUM> can further include one or more physiologic sensors <NUM>. Such sensors are commonly referred to (in the pacemaker arts) as "rateresponsive" or "exercise" sensors. The physiological sensor <NUM> may further be used to detect changes in the physiological condition of the heart, or diurnal changes in activity (e.g., detecting sleep and wake states). Signals generated by the physiological sensors <NUM> are passed to the microcontroller <NUM> for analysis and optional storage in the memory <NUM> in connection with the cardiac activity data, markers, episode information and the like. While shown as being included within the IMD <NUM>, the physiologic sensor(s) <NUM> may be external to the IMD <NUM>, yet still be implanted within or carried by the patient. Examples of physiologic sensors might include sensors that, for example, activity, temperature, sense respiration rate, pH of blood, ventricular gradient, activity, position/posture, minute ventilation (MV), and so forth.

A battery <NUM> provides operating power to all of the components in the IMD <NUM>. The battery <NUM> is capable of operating at low current drains for long periods of time. The battery <NUM> also desirably has a predictable discharge characteristic so that elective replacement time can be detected. As one example, the unit <NUM> employs lithium/silver vanadium oxide batteries. The battery <NUM> may afford various periods of longevity (e.g., three years or more of device monitoring). In alternate embodiments, the battery <NUM> could be a secondary battery (e.g., rechargeable). See for example, <CIT> "Cardiac Event Microrecorder And Method For Implanting Same".

<FIG> illustrates a plan view of the IMD <NUM> according to an embodiment. The header <NUM> is mounted to an end (e.g., a header end) <NUM> of the device housing <NUM> via a feedthrough assembly <NUM>. The IMD <NUM> has a small form factor with an elongated shape. The IMD <NUM> has curved ends and rounded or beveled edges to avoid snagging during implantation or damaging tissue when disposed within the sub-cutaneous pocket of the patient.

The device housing <NUM> may include top and bottom case portions, or shells, that join with one another to enclose a battery <NUM> and an electronics module <NUM> (also referred to as a hybrid circuit). One of the case portions may be omitted in <FIG> to show the battery <NUM> and the electronics module <NUM> within an internal cavity of the device housing <NUM>. The battery <NUM> may be the battery <NUM> shown in <FIG>, and the electronics module <NUM> may include the components described above in connection with <FIG>, and/or as described in any of the patents or published applications cited herein. For example, the electronics module <NUM> includes sensing circuitry that receives EGM signals from the electrodes of the IMD <NUM>, such as the sensing electrode <NUM> on the header <NUM>. The sensing circuitry may analyze and process the EGM signals, and may generate messages to communicate the EGM signals, or data based on the EGM signals, via the antenna <NUM> (shown in <FIG>) to the external device <NUM>. In the illustrated embodiment, the antenna <NUM> is disposed within an interior volume of a header body <NUM> of the header <NUM>. The header body <NUM> represents a solid (non-hollow) body formed of a generally homogeneous dielectric (e.g., electrically insulative) material.

The header <NUM> has a mounting end <NUM> configured to be mounted to the feedthrough assembly <NUM>. The sensing electrode <NUM> and the antenna <NUM> of the header <NUM> are electrically connected to the electronics module <NUM> via electrically conductive elements such as wires, traces, pins, receptacle connectors, plug connectors, and/or the like that project across the mounting end <NUM>. At least some of the conductive elements traverse the feedthrough assembly <NUM> at the interface between the header <NUM> and the device housing <NUM>. In an alternative embodiment, the IMD <NUM> does not have a feedthrough assembly, and the mounting end <NUM> of the header <NUM> mounts directly to the end <NUM> of the housing <NUM>.

The assembly of the IMD <NUM> generally may include electrically connecting the battery <NUM> to the electronics module <NUM> to power the electronics module <NUM>. The battery <NUM> and the electronics module <NUM> may be loaded into one of the housing case portions or shells. The conductive elements held by the feedthrough assembly <NUM>, such as wires, pins, or connectors, may be electrically connected to the electronics module <NUM> as well. The header <NUM> is mounted to the feedthrough assembly <NUM> in a way that includes electrically connecting the sensing electrode <NUM> and the antenna <NUM> to the conductive elements of the feedthrough assembly <NUM>. The two case portions of the housing <NUM> may be coupled together to enclose the battery <NUM> and the electronics module <NUM>. The order of these previous steps may be modified. Once the IMD device <NUM> is coupled together, the interfaces between the case portions of the housing <NUM> and the interface between the header <NUM> and the housing <NUM> at the feedthrough assembly <NUM> are sealed. For example, at least one of the interfaces may be welded, filled with a sealant, bonded, or the like to hermetically seal the interior components of the IMD <NUM> from the organic tissues and fluids of the patient that form the external environment.

<FIG> is a perspective view of the header <NUM> according to a first embodiment. The header <NUM> includes the sensing electrode <NUM>, the antenna <NUM>, and the header body <NUM>. In the illustrated embodiment, the header <NUM> also includes a backfill or potting material <NUM>. The backfill material <NUM> is applied after the electrode <NUM> and the antenna <NUM> are electrically connected to corresponding conductive elements of the feedthrough assembly <NUM> or device housing <NUM> to fill in the open cavity within the header body <NUM> in which the electrical components are connected. The header body <NUM> at least partially surrounds the sensing electrode <NUM> and the antenna <NUM>. The header body <NUM> is shown in phantom in <FIG> to show the components within the interior volume of the header body <NUM>.

The header <NUM> has multiple sides including a first face <NUM>, a second face <NUM>, and a curved distal surface <NUM> that extends along a thickness of the header <NUM> from the first face <NUM> to the second face <NUM>. The header <NUM> extends from a mounting end <NUM> of the header <NUM> to the curved distal surface <NUM>. For example, both the first face <NUM> and the second face <NUM> extend from the mounting end <NUM> to the curved distal surface <NUM>. The first face <NUM> is opposite the second face <NUM>. The first face <NUM>, the second face <NUM>, and the distal surface <NUM> represent first, second, and third sides of the header <NUM>. The mounting end <NUM> represents a fourth side of the header <NUM>. The header <NUM> may have additional sides depending on the contour of the curved distal surface <NUM>. For example, fifth and sixth sides of the header <NUM> may be surfaces located between the first and second faces <NUM>, <NUM> and extending from the mounting end <NUM> to the curved distal surface <NUM>. The multiple sides of the header <NUM> merge with one another along beveled or rounded edges to form a smooth overall contour for the header <NUM>.

<FIG> is a first elevation view of the header <NUM> in <FIG> showing the first side or face <NUM>. <FIG> is a second elevation view of the header <NUM> in <FIG> showing the second side or face <NUM>. <FIG> is a third elevation view of the header <NUM> in <FIG> in profile showing the curved distal surface <NUM>. In <FIG>, the components within the header body <NUM>, such as the antenna <NUM> and the sensing electrode <NUM> are shown in phantom.

The header <NUM> in the illustrated embodiment has a semicircular or D-shaped perimeter around the faces <NUM>, <NUM>. The perimeter is defined by the mounting end <NUM> and the curved distal surface <NUM>. The shape provides a smooth contour along the end of the IMD <NUM>. <FIG> shows that the header <NUM> has a generally rectangular shape when viewed in profile. The header <NUM> may have other shapes in other embodiments.

The sensing electrode <NUM> according to the embodiments disclosed herein is designed to have exposed sections along multiple different sides of the header <NUM>. For this reason, the electrode <NUM> is referred to as a multi-sided header electrode. By positioning the electrode <NUM> along multiple sides of the header <NUM>, the overall surface area of the electrode <NUM> that is able to contact the tissue of the patient can be increased relative to positioning the electrode <NUM> only along one side of the header <NUM>. The increased tissue-electrode contact surface area can provide more robust and accurate cardiac sensing, with reduced sensitivity to movements of the IMD <NUM> due to postural changes or the like. Furthermore, if the IMD <NUM> does rotate in the sub-cutaneous pocket due to patient movement such that one portion of the electrode <NUM> along one side of the header <NUM> loses contact with the tissue, another portion of the electrode <NUM> along a different side of the header <NUM> would likely sustain contact with the tissue, thereby reducing the risk of missing EGM signals and diagnosing a false pause episode.

With reference to <FIG>, the sensing electrode <NUM> includes at least a first body portion <NUM>, a second body portion <NUM>, and a bridge portion <NUM>. The bridge portion <NUM> mechanically and electrically connects the first and second body portions <NUM>, <NUM>. The first and second body portions <NUM>, <NUM> are spaced apart from each other and extend along different sides of the header <NUM>. Each of the body portions <NUM>, <NUM> is at least partially surrounded by and/or embedded in the header body <NUM>, and also has a surface that is exposed to the external environment surrounding the IMD <NUM>. For example, when implanted, the external environment includes organic tissues, such as fat and muscle, and fluids of the patient surrounding the IMD <NUM>. The body portions <NUM>, <NUM> are exposed to the external environment such that at least one surface of the respective body portion <NUM>, <NUM> is not coated by the material of the header body <NUM> or otherwise encapsulated within the header <NUM>, enabling the exposed surfaces to experience direct physical contact with the organic tissue of the patient to establish persistent electrode-tissue contact.

In the illustrated embodiment, the first body portion <NUM> is located along the first face <NUM> of the header <NUM>, and the second body portion is located along the second face <NUM> of the header <NUM>. As such, the two body portions <NUM>, <NUM> of the electrode <NUM> are disposed along opposite sides of the header <NUM>. A benefit of locating the body portions <NUM>, <NUM> of the electrode <NUM> along both faces <NUM>, <NUM> of the header <NUM> is that in the event of the IMD <NUM> rotating within the patient, one of the body portions <NUM>, <NUM> will still generally face the patient's heart. For example, if the first body portion <NUM> was previously facing the heart, the IMD <NUM> may be calibrated to primarily use the first body portion <NUM> to monitor EGM signals from the heart. In the event that the IMD <NUM> rotates such that the first body portion <NUM> now faces away from the heart, the second body portion <NUM> may be pointed towards the heart. The controller in the electronics module <NUM> (<FIG>) can then calibrate the IMD <NUM> to primarily use the second body portion <NUM> to monitor the EGM signals. If the electrode was only exposed along one side, if that side moves and faces away from the heart, the sensing capability and quality of the IMD <NUM> may suffer.

The bridge portion <NUM> is mechanically and electrically connected to both body portions <NUM>, <NUM>. The bridge portion <NUM> extends through an interior volume of the header body <NUM> from the first body portion <NUM> to the second body portion <NUM>. In the illustrated embodiment, the bridge portion <NUM> snakes along a non-linear path between the body portions <NUM>, <NUM>. In an alternative embodiment, the bridge portion <NUM> may be linear or non-linear but more direct than the illustrated embodiment.

As shown in <FIG>, the first body portion <NUM> includes a platform <NUM> and a flange <NUM> that extends from a perimeter of the platform <NUM>. The flange <NUM> optionally may surround the entire perimeter of the platform <NUM>. The platform <NUM> has an outer surface <NUM> that faces away from the header <NUM> (e.g., away from the antenna <NUM>, the second body portion <NUM>, and the bridge portion <NUM>). The platform <NUM> protrudes outward relative to the header body <NUM>, and the outer surface <NUM> is exposed to the external environment. The outer surface <NUM> may be planar. The plane of the outer surface <NUM> may be parallel to the first face <NUM> of the header <NUM>, as defined by the header body <NUM>. In an alternative embodiment, the outer surface <NUM>, or at least a portion thereof, may be convex to bulge outward.

As shown in <FIG>, the platform <NUM> may have a D-shaped or semicircular structure as defined by edges <NUM> of the outer surface <NUM>. The size and shape of the first body portion <NUM> may be determined or selected based on available space along the header first face <NUM>. For example, larger sizes may be preferrable if available to increase the surface area of the exposed outer surface <NUM>. In an embodiment, the surface area of the outer surface <NUM> may represent at least <NUM>% of a total surface area of the first face <NUM> of the header <NUM>, such as at least <NUM>% of the total surface area. The D or semicircular shape of the platform <NUM> conforms to the shape of the header <NUM>. For example, the edges <NUM> include arcuate distal edges 154a that are disposed proximate to, and conform with, the curved distal surface <NUM> of the header <NUM>. The distal edges 154a are slightly spaced apart from the curved distal surface <NUM> in the illustrated embodiment, but may extend to the edge of the curved distal surface <NUM> or along the curved distal surface <NUM> in another embodiment, as described herein. The edges <NUM> are beveled or rounded to avoid sharp angles that could damage or snag on patient tissue.

The second body portion <NUM> is structured similar to the first body portion <NUM> with a platform <NUM> and a flange <NUM> that extends from a perimeter of the platform <NUM>. The platform <NUM> has an outer surface <NUM> that faces away from the header <NUM> (e.g., away from the antenna <NUM>, the first body portion <NUM>, and the bridge portion <NUM>). The platform <NUM> protrudes outward relative to the header body <NUM>, and the outer surface <NUM> is exposed to the external environment. The outer surface <NUM> may be planar. The plane of the outer surface <NUM> may be parallel to the second face <NUM> of the header <NUM>, as defined by the header body <NUM>. In the illustrated embodiment, the planar outer surface <NUM> of the first body portion <NUM> is parallel to the planar outer surface <NUM> of the second body portion <NUM>, as shown in <FIG>. In an alternative embodiment, the outer surface <NUM>, or at least a portion thereof, may be convex to bulge outward.

As shown in <FIG>, the platform <NUM> has a distal edge 164a that is similar in length and location proximate to the curved distal surface <NUM> as compared to the distal edge 154a of the platform <NUM>. The distal edge 164a conforms to the shape of the curved distal surface <NUM>. In the illustrated embodiment, the second body portion <NUM>, and the platform <NUM> thereof, is smaller in total surface area than the first body portion <NUM>. The smaller size may be due to space constraints. As shown in <FIG>, the second face <NUM> of the header <NUM> may have an opening to provide a cavity <NUM> in which the sensing electrode <NUM> and the antenna <NUM> are interconnected to corresponding conductive elements, such as wires <NUM>. In an alternative embodiment in which the space constraint is not present, the second body portion <NUM> may be the same size as the first body portion <NUM>.

As shown in <FIG>, the first face <NUM> of the header <NUM> is defined in part by the platform <NUM> of the first body portion <NUM> and in part by the header body <NUM>. The platform <NUM> projects or protrudes beyond the header body <NUM> such that the outer surface <NUM> is stepped or raised relative to the surface of the header body <NUM> along the first face <NUM> surrounding the platform <NUM>. The second face <NUM> of the header <NUM> is similarly defined in part by the platform <NUM> and the header body <NUM>, and the platform <NUM> similarly projects or protrudes outward relative to the header body <NUM>. In the illustrated arrangement, the first and second body portions <NUM>, <NUM> define raised electrode contact surfaces that at least partially project into the tissue of the patient when the header <NUM> abuts against the tissue. The raised platforms <NUM>, <NUM> reduce the likelihood of the electrode <NUM> losing contact with the patient tissue, relative to electrode surfaces that are flush with the side of the header or recessed relative to the side of the header. In an alternative embodiment, the outer surfaces <NUM>, <NUM> may be substantially flush with the first and second faces <NUM>, <NUM> instead of raised and protruding outward from the faces <NUM>, <NUM>.

The antenna <NUM> according to at least one embodiment is fully contained or encapsulated within an interior volume of the header body <NUM> and the backfill material <NUM> that fills the cavity <NUM>. For example, no portion of the antenna <NUM> is exposed to the external environment. The antenna <NUM> is disposed proximate to the curved distal surface <NUM>. The antenna <NUM> may have an arcuate shape that generally conforms to the curved distal surface <NUM>. The antenna <NUM> may be located between the first and second body portions <NUM>, <NUM> of the sensing electrode <NUM>, as shown in <FIG>. The antenna <NUM> is electrically isolated from the components of the sensing electrode <NUM> via the material of the header body <NUM> to avoid interference and short circuits. Thus, although the antenna <NUM> appears to contact the bridge portion <NUM> in <FIG>, the antenna <NUM> is actually discrete and spaced apart from the bridge portion <NUM>. The size, shape, and placement of the antenna <NUM> in the header body <NUM> may vary according to design preferences. In an alternative embodiment, the antenna <NUM> may be exposed to the external environment along the curved outer surface <NUM> of the header body <NUM>.

In at least one embodiment, the sensing electrode <NUM> and the antenna <NUM> are embedded within the material of the header body <NUM> by overmolding the electrode <NUM> and the antenna <NUM>. The header body <NUM> may be composed of a dielectric material, such as a thermoplastic elastomer, an epoxy, a silicone, or the like. The dielectric material provides electrical insulation between the electrically conductive antenna <NUM> and sensing electrode <NUM>. The dielectric material of the header body <NUM> is also selected to be biocompatible with the organic tissue of the patient.

An example assembly process for the header <NUM> includes inserting the sensing electrode <NUM> and the antenna <NUM> into a mold, and then pouring the dielectric material of the header body <NUM> in a heated, flowable (e.g., liquid or quasi-liquid) state into the mold to surround and contact the surfaces of the components. As the dielectric material cools and solidifies, the header body <NUM> forms. The interior volume of the header body <NUM> conforms to the shapes of the conductive components to embed the components. Once the dielectric material solidifies to form the header body <NUM>, a preassembled header <NUM> is produced. The preassembled header <NUM> can be mounted to the device housing <NUM> to form the IMD <NUM> by first electrically connecting the antenna <NUM> and the sensing electrode <NUM> to the electronics module <NUM>, optionally via the feedthrough assembly <NUM>. Then, after the electrical connections are made, the backfill or potting material <NUM> is applied to fill in the cavity <NUM> of the header body <NUM>. The final steps may include securing the header <NUM> to the device housing <NUM> and sealing the interface between the header <NUM> and the device housing <NUM> to provide a hermetic seal.

<FIG> is a cross-sectional view of a portion of the header <NUM> showing the first body portion <NUM> of the sensing electrode <NUM>. The cross-section may bisect the first body portion <NUM>. In an embodiment, the first body portion <NUM> is embedded in the dielectric material of the header body <NUM> such that the dielectric material envelops the flange <NUM>. For example, the dielectric material of the header body <NUM> engages both an inner surface <NUM> and an outer surface <NUM> of the flange <NUM>, as well as a perimeter end <NUM> of the flange <NUM>. Upon solidifying, the head body <NUM> secures the first body portion <NUM> in a fixed position. The dielectric material may also contact an inner surface <NUM> of the platform <NUM> that is opposite the outer surface <NUM>. The platform <NUM> projects beyond the portion of the first face <NUM> defined by the header body <NUM>, and the outer surface <NUM> is exposed to the external environment to establish sustained contact with patient tissue.

<FIG> is a first perspective view of the sensing electrode <NUM> according to the embodiment shown in <FIG>. <FIG> is a second perspective view of the sensing electrode <NUM> shown in <FIG>. The sensing electrode <NUM> may be a monolithic (e.g., one-piece) structure such that the first body portion <NUM> and the second body portion <NUM> are integrally connected to the bridge portion <NUM>. The first body portion <NUM> is seamlessly connected to a first end <NUM> of the bridge portion <NUM>, and the second body portion <NUM> is seamlessly connected to a second end <NUM> of the bridge portion <NUM>. In an embodiment, the second electrode <NUM> is a stamped and formed metal element. For example, the first and second body portions <NUM>, <NUM> and the bridge portion <NUM> may be stamped out of a metal sheet and then bent and formed into the shape shown in <FIG> without separating the components <NUM>, <NUM>, <NUM>. The second electrode <NUM> is electrically conductive, and the bridge portion <NUM> electrically and mechanically connects the first body portion <NUM> to the second body portion <NUM>. As such, the sensing electrode <NUM> is a single electrode with multiple, spaced-apart tissue contacting surfaces, as opposed to two discrete electrodes. For example, the first and second body portions <NUM>, <NUM> are not merely two different electrodes that are at the same electrical potential, but rather are two portions of a monolithic structure.

In an embodiment, a segment of the bridge portion <NUM> is utilized as an interconnect panel <NUM> for electrically connecting the sensing electrode <NUM> to a conductive element that projects through the mounting end <NUM> of the header <NUM> to electrically connect the sensing electrode <NUM> to the electronics module <NUM>. For example, as shown in <FIG>, a wire <NUM> may be welded, crimped, bonded, or otherwise secured to the interconnect panel <NUM> of the bridge portion <NUM>.

Optionally, the first and second body portions <NUM>, <NUM> of the sensing electrode <NUM> include bent tabs <NUM> along respective perimeters thereof. The bent tabs <NUM> may be flared. The tabs <NUM> are bent out of the plane of the outer surfaces <NUM>, <NUM>, as shown in <FIG>, and project into an interior of the header <NUM>. <FIG> shows the tabs <NUM> prior to being bent out of plane. The tabs <NUM> are used to anchor the sensing electrode <NUM> in place relative to the header body <NUM>. For example, the tabs <NUM> may be encased within the dielectric material of the header body <NUM> during an overmold process.

<FIG> is a perspective view of the antenna <NUM> of the header <NUM> according to an embodiment. The antenna <NUM> has a monolithic structure that extends from an interconnect panel <NUM> to a distal end <NUM>. The interconnect panel <NUM> is configured to secure to a conductor that projects from the mounting end <NUM> of the header <NUM> into the device housing <NUM>. The antenna <NUM> may have various sizes and shapes in different embodiments.

<FIG> illustrates a profile view of the IMD <NUM> shown in <FIG> in operation. The IMD <NUM> may utilize sensing vectors <NUM> between multiple electrodes to monitor the electrical activity of the heart. For example, the sensing electrode <NUM> in the header <NUM> represents a first electrode. The device housing <NUM> includes or represents a housing electrode <NUM>. For example, the device housing <NUM> may have an electrically conductive case or shell that functions as the housing electrode <NUM>, or the device housing <NUM> may include a discrete electrode mounted to or along an exterior surface of the housing <NUM>. The sensing electrode <NUM> may be a positive electrode, or cathode, and the housing electrode <NUM> may be a negative electrode, or anode. Alternatively, the sensing electrode <NUM> may function as an anode, and the housing electrode <NUM> may function as a cathode. The sensing vectors <NUM> are emitted from one of the electrodes <NUM>, <NUM> and travel through the patient tissue and/or fluid in the external environment before returning to the other electrode <NUM>, <NUM>. The electronics module <NUM> analyses the received sensing vectors <NUM> to detect modifications in the sensing vectors <NUM> attributable to cardiac activity. Because the sensing electrode <NUM> is multi-sided, the sensing vectors <NUM> can extend from the IMD <NUM> along multiple directions, resulting in more robust cardiac sensing.

<FIG> is a perspective view of the header <NUM> of the IMD <NUM> according to a second embodiment. <FIG> is an elevation view of the header <NUM> in <FIG> showing the first face <NUM>. <FIG> is an elevation view of the header <NUM> in <FIG> showing the second face <NUM>. In the illustrated embodiment, the header <NUM> is shown mounted to the feedthrough assembly <NUM>. For example, the feedthrough assembly <NUM> has a base <NUM> that abuts the mounting end <NUM> of the header <NUM> at an interface <NUM>. A segment of the base <NUM> outside of the header <NUM> is configured to attach to the end <NUM> of the device housing <NUM>. <FIG> and <FIG> show multiple conductors <NUM> that extend through the base <NUM> of the feedthrough assembly <NUM> into the header <NUM> to electrically connect to the sensing electrode <NUM> and the antenna <NUM>.

The header <NUM> in <FIG> differs from the header <NUM> shown in <FIG> because the header body <NUM> defines a suture opening <NUM>. The suture opening <NUM> extends through an entire thickness of the header body <NUM> from the first face <NUM> to the second face <NUM>. The suture opening <NUM> is provided to enable anchoring the IMD <NUM>, via the header <NUM>, to the patient tissue. For example, a suture may be provided through the suture opening <NUM> into a piece of tissue to tether the IMD <NUM> to that tissue. In the illustrated embodiment, the first body portion <NUM> of the sensing electrode <NUM> is narrowed or truncated to provide space for the suture opening <NUM>.

<FIG> illustrates a profile view of the header <NUM> according to another embodiment of the present disclosure. In <FIG>, the header <NUM> lacks the backfill or potting material <NUM> shown in <FIG>. For example, the header <NUM> includes the sensing electrode <NUM>, the antenna <NUM>, and the header body <NUM>. In the illustrated embodiment, the header body <NUM> is overmolded in-situ on the base <NUM> of the feedthrough assembly <NUM>. An exemplary assembly process may include electrically connecting the antenna <NUM> and the sensing electrode <NUM> to corresponding conductors <NUM> of the feedthrough assembly <NUM>. The antenna <NUM>, sensing electrode <NUM>, and even a portion of the base <NUM> are then inserted into a mold, and the dielectric material is flowed into the mold to form around the components. The dielectric material solidifies to form the header body <NUM>, as described above. In this example, the dielectric material surrounds at least a portion of the base <NUM>, so the header body <NUM> when formed effectively covers the interface <NUM> between the header <NUM> and the feedthrough assembly <NUM>. In essence, the header <NUM> forms in-situ on the feedthrough assembly <NUM>.

In this embodiment, there is no need to define an interconnect cavity or opening for later backfilling, so there is space to increase the electrode surface area. For example, in <FIG> the second body portion <NUM> of the sensing electrode <NUM> is larger than the second body portion <NUM> in previously described embodiments. The second body portion <NUM> in <FIG> may have the same size and shape as the first body portion <NUM>. Furthermore, the bridge portion <NUM> may extend linearly across the thickness of the header body <NUM> between the first and second body portions <NUM>, <NUM>. Increasing the exposed surface area of the sensing electrode <NUM> can increase the robustness, reliability, and sensing accuracy of the IMD <NUM> relative to having less exposed electrode surface area.

<FIG> illustrates a profile view of the header <NUM> according to another embodiment of the present disclosure. <FIG> is similar to the embodiment in <FIG>, except that the first body portion <NUM> and the second body portion <NUM> each extend at least partially along the curved distal surface <NUM> of the header <NUM>. For example, the first body portion <NUM> extends along the first face <NUM> and also extends along a portion of the curved distal surface <NUM>. Similarly, the second body portion <NUM> extends along both the second face <NUM> and the curved distal surface <NUM>. Neither of the body portions <NUM>, <NUM> extends directly above the antenna <NUM>, so may not interfere with communications transmitted or received by the antenna <NUM>. Extending the sensing electrode <NUM> over the edge along the curved distal surface <NUM> enables the sensing electrode <NUM> to increase the total amount of exposed surface area for contacting the patient tissue, and also enables the sensing electrode <NUM> to face in a direction that is generally orthogonal to the directions faced by the body portions <NUM>, <NUM> along the first and second faces <NUM>, <NUM>.

<FIG> illustrates a profile view of the header <NUM> according to yet another embodiment of the present disclosure. In <FIG>, the sensing electrode <NUM> includes the first body portion <NUM> exposed along the first face <NUM>, the second body portion <NUM> exposed along the second face <NUM>, as previously described, and also includes a third body portion <NUM> exposed along the curved distal surface <NUM>. The third body portion <NUM> is mechanically and electrically connected to the bridge portion <NUM>. The third body portion <NUM> is spaced apart from the antenna <NUM> to avoid interfering with the communications of the antenna <NUM>. The sensing electrode <NUM> in the illustrated embodiment is tri-sided with exposed segments of the electrode <NUM> located along three different sides of the header <NUM>. The sensing electrode <NUM> may include more than three body portions in other embodiments.

In one or more embodiments, an implantable medical device <NUM> is provided that includes a header <NUM> configured to be mounted to an end <NUM> of a device housing <NUM> that contains an electronics module <NUM> therein. The header <NUM> includes an antenna <NUM>, a sensing electrode, <NUM> and a header body <NUM>. The sensing electrode <NUM> includes a first body portion <NUM>, a second body portion <NUM>, and a bridge portion <NUM> that mechanically and electrically connects the first and second body portions <NUM>, <NUM>. The bridge portion <NUM> is disposed within an interior of the header body <NUM>. Each of the first body portion <NUM> and the second body portion <NUM> has a respective flange <NUM>, <NUM> and a respective platform <NUM>, <NUM> that is raised relative to the flange <NUM>, <NUM>. The header body <NUM> envelops the flanges <NUM>, <NUM> of both the first and second body portions <NUM>, <NUM>. The platform <NUM> of the first body portion <NUM> protrudes outward beyond the header body <NUM> along a first side <NUM> of the header <NUM>, and an outer surface <NUM> of the platform <NUM> of the first body portion <NUM> is exposed to an external environment. The platform <NUM> of the second body portion <NUM> protrudes outward beyond the header body <NUM> along a second side <NUM> of the header <NUM>, and an outer surface <NUM> of the platform <NUM> of the second body portion <NUM> is exposed to the external environment.

Optionally, the first side <NUM> of the header <NUM> is opposite the second side <NUM>.

Optionally, the sensing electrode <NUM> is a monolithic structure, and the first body portion <NUM> and the second body portion <NUM> are integrally connected to different ends <NUM>, <NUM> of the bridge portion <NUM>.

In an example, the implantable medical device <NUM> also includes a feedthrough assembly <NUM> that abuts a mounting end <NUM> of the header <NUM> at an interface <NUM> and attaches to the end <NUM> of the device housing <NUM>. The header body <NUM> may comprise a dielectric material that covers the interface <NUM> and surrounds at least a segment <NUM> of the feedthrough assembly <NUM>.

It should be clearly understood that the various arrangements and processes broadly described and illustrated with respect to the Figures, and/or one or more individual components or elements of such arrangements and/or one or more process operations associated of such processes, can be employed independently from or together with one or more other components, elements and/or process operations described and illustrated herein. Accordingly, while various arrangements and processes are broadly contemplated, described and illustrated herein, it should be understood that they are provided merely in illustrative and non-restrictive fashion, and furthermore can be regarded as but mere examples of possible working environments in which one or more arrangements or processes may function or operate.

As will be appreciated by one skilled in the art, various aspects may be embodied as a system, method or computer (device) program product. Accordingly, aspects may take the form of an entirely hardware embodiment or an embodiment including hardware and software that may all generally be referred to herein as a "circuit," "module" or "system. " Furthermore, aspects may take the form of a computer (device) program product embodied in one or more computer (device) readable storage medium(s) having computer (device) readable program code embodied thereon.

Aspects are described herein with reference to the Figures, which illustrate example methods, devices and program products according to various example embodiments. These program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing device or information handling device to produce a machine, such that the instructions, which execute via a processor of the device implement the functions/acts specified. The program instructions may also be stored in a device readable medium that can direct a device to function in a particular manner, such that the instructions stored in the device readable medium produce an article of manufacture including instructions which implement the function/act specified. The program instructions may also be loaded onto a device to cause a series of operational steps to be performed on the device to produce a device implemented process such that the instructions which execute on the device provide processes for implementing the functions/acts specified.

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.

Claim 1:
An implantable medical device (<NUM>) comprising:
a header (<NUM>) configured to be mounted to an end (<NUM>) of a device housing (<NUM>) that contains an electronics module (<NUM>) therein, the header (<NUM>) comprising an antenna (<NUM>), a sensing electrode (<NUM>), and a header body (<NUM>) that at least partially surrounds the antenna (<NUM>) and the sensing electrode (<NUM>),
wherein the sensing electrode (<NUM>) comprises a first body portion (<NUM>), a second body portion (<NUM>), and a bridge portion (<NUM>) that mechanically and electrically connects the first and second body portions (<NUM>, <NUM>), the first body portion (<NUM>) at least partially exposed to an external environment along a first side (<NUM>) of the header (<NUM>) and the second body portion (<NUM>) at least partially exposed to the external environment along a second side (<NUM>) of the header (<NUM>) that is different from the first side (<NUM>), wherein the first side (<NUM>) of the header (<NUM>) is defined in part by the header body (<NUM>) and in part by the first body portion (<NUM>) of the sensing electrode (<NUM>), characterized in that the part of the first side (<NUM>) defined by the first body portion (<NUM>) protrudes outward relative to the part defined by the header body (<NUM>).