Patent Description:
Powering implantable medical devices is one aspect of helping ensure the proper function of the medical devices after being implanted. One option to power such medical devices is to use percutaneous wires directly attached to these medical devices to provide power; however, such a configuration is susceptible to infection and reduces patient mobility. Transcutaneous energy transfer systems (TETS) are being developed to provide such power to implantable medical devices such as ventricular assist devices where power can be wirelessly transmitted over a range of skin and/or tissue thicknesses. <CIT> relates to a mechanical gauge for estimating inductance changes in resonant power transfer systems with flexible coils for use with implanted medical devices. <CIT> relates to a method od improving a battery recharge efficiency by statistical analysis. <CIT> relates to transmission of information from an implantable medical device. <CIT> relates to an implantable medical device and system.

The techniques of this disclosure generally relate to Transcutaneous Energy Transfer Systems (TETS) for wireless transfer of power from an external energy transfer coil to an implantable energy transfer coil. When the application of the power transfer is critical to maintain a life-sustaining therapy such as a fully implanted LVAD system, the ability to detect or predict performance and reliability issues may be important to mitigation against safety hazards. One or more embodiments described herein may be used to monitor the performance integrity of an implanted TET system. One or more embodiments provide one or more of the following:.

According to one aspect of the invention, a system is provided. The system includes a power device implantable within a patient for powering an implantable medical device. The power device includes a first coil configured to receive wireless power signals for powering the implantable medical device. The power device further includes processing circuitry configured to determine at least one measurable electrical characteristic in a plurality of electrical pathways in the power device including an electrical pathway to the first coil, and detect reduced performance in receiving wireless power signals based at least in part on the determined at least one measurable electrical characteristic.

According to one or more embodiment of this aspect, an external device is positioned outside of the patient for providing power to the implantable medical device. The external device includes a second coil for transmitting power signals, and processing circuitry configured to receive an indication of power received by the power device and determine a wireless power transfer efficiency over a predetermined period of time based at least in part on the received indication of the power received by the power device. According to one or more embodiment of this aspect, the wireless power transfer efficiency over the predetermined period of time corresponds to a long term moving average. According to one or more embodiment of this aspect, the long term moving average indicates whether performance is degrading due to at least one non-alignment factor between the first coil and the second coil.

According to one or more embodiment of this aspect, the at least one non-alignment factor includes at least one of increased fat thickness of a person in which the power device is implanted and degradation of at least one material characteristic of the power device. According to one or more embodiment of this aspect, the processing circuitry is further configured to trigger a notification if the long term moving average meets a predefined threshold. According to one or more embodiment of this aspect, the processing circuitry is further configured to receive an indication of the determined at least one measurable electrical characteristic, and determine a long term moving average based at least in part on the determined at least one measurable electrical characteristic.

According to one or more embodiment of this aspect, the plurality of electrical pathways includes feedthrough cables, connectors and coil windings. According to one or more embodiment of this aspect, the processing circuitry is further configured to trigger a notification if any one of the at least one measurable electrical characteristic is one of below and above a predefined threshold. According to one or more embodiment of this aspect, the power device is positioned one of proximate and within the medical device.

According to an example, a method (not claimed) for a system including a power device implantable within a patient for powering an implantable medical device is provided. The power device includes a first coil configured to receive wireless power signals for powering the implantable medical device. At least one measurable electrical characteristic in a plurality of electrical pathways in the power device including an electrical pathway to the first coil is determined. Reduced performance in receiving wireless power signals is detected based at least in part on the determined at least one measurable electrical characteristic.

According to an example , the system further includes an external device positioned outside of the patient for providing power to the implantable medical device where the external device includes a second coil for transmitting power signals. An indication of power received by the power device is received. A wireless power transfer efficiency over a predetermined period of time is determined based at least in part on the received indication of the power received by the power device.

According to an example , the wireless power transfer efficiency over the predetermined period of time corresponds to a long term moving average. According to one or more embodiment of this aspect, the long term moving average indicates whether performance is degrading due to at least one non-alignment factor between the first coil and the second coil. According to one or more embodiment of this aspect, the at least one non-alignment factor includes at least one of increased fat thickness of a person in which the power device is implanted and degradation of at least one material characteristic of the power device.

According to an example, a notification is triggered if the long term moving average meets a predefined threshold. According to one or more embodiment of this aspect, an indication of the determined at least one measurable electrical characteristic is received. A long term moving average is determined based at least in part on the determined at least one measurable electrical characteristic.

According to an example , the plurality of electrical pathways includes a feedthrough cables, connectors and coil windings. According to one or more embodiment of this aspect, a notification is triggered if any one of the at least one measurable electrical characteristic is one of below and above a predefined threshold. According to one or more embodiment of this aspect, the power device is positioned one of proximate and within the medical device.

Before describing in detail exemplary embodiments, it is noted that the embodiments reside primarily in combinations of device components and processing steps related to TETS for wireless transfer of power from an external energy transfer coil to an implantable energy transfer coil. Accordingly, components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

Referring now to the drawing figures, in which like elements are referred to by like reference numerals, there is shown in <FIG> a schematic diagram of a system <NUM>, according to one or more embodiments. System <NUM> includes one or more medical devices <NUM> in electrical communication with one or more power devices <NUM> such as via one or more wired connection, for example. System <NUM> includes one or more external devices <NUM> in electrical communication with the power device <NUM> such as using wireless signals and/or wireless communication. System <NUM> may optionally include a host device <NUM> in communication with external device <NUM>.

Medical device <NUM> may correspond to any medical device that is implantable within a patient <NUM> and that may use power received from an external power source to perform at least one function. For example, medical device <NUM> may be a left ventricular assist device (LVAD), other assist devices, devices with rechargeable batteries, among other devices known in the art. Power device <NUM> includes one or more coils for receiving wireless power signals where the power signals may be electrically converted to power that is usable by medical device <NUM> as is known in the art. Power device <NUM> includes monitoring unit <NUM> that is configured to perform one or more power device <NUM> functions as described herein such as with respect to detecting a reduction in performance in receiving wireless power signals as described herein.

External device <NUM> includes coils <NUM> for providing wireless power signals to power device <NUM> as is known in the art. In one or more embodiments, external device <NUM> includes analysis unit <NUM> that is configured to perform one or more determinations based at least in part on information/data received from power device <NUM> and/or medical device <NUM>, and other data that that may be determined by external device <NUM>, as described herein. In particular, external device <NUM> may be in data communication with one or more of power device <NUM>, medical device <NUM>, host device <NUM>, etc., via one or more wireless communication protocols. In one or more embodiments, the wireless power signals communicated between coils <NUM> and <NUM> may transfer data between power device <NUM> and external device <NUM>. Alternatively, the wireless power signals may be used solely for providing power such that these signals do not carry data.

External device <NUM> and/or power device <NUM> and/or medical device <NUM> may be in data communication with host device <NUM> where host device <NUM> may be configured to display one or more notifications, communicate with other devices with one or more networks, etc. An example implementation, in accordance with one or more embodiments, of medical device <NUM>, power device <NUM> and external device <NUM> discussed in the preceding paragraphs will now be described with reference to <FIG>. System <NUM> includes power device <NUM> that includes hardware <NUM>. The hardware <NUM> may include a communication interface <NUM> for setting up and maintaining a wired or wireless connection with an interface of a different communication device of the system <NUM> such as with one or more of medical device <NUM>, external device <NUM> and host device <NUM>.

In the embodiment shown, the hardware <NUM> of the power device <NUM> further includes processing circuitry <NUM>.

Thus, the power device further has software <NUM> stored internally in, for example, memory <NUM>, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the power device <NUM> via an external connection. The processing circuitry <NUM> may be configured to control any of the methods and/or processes described herein and/or to cause such methods, and/or processes to be performed, e.g., by power device <NUM>. Processor <NUM> corresponds to one or more processors <NUM> for performing power device <NUM> functions described herein. The memory <NUM> is configured to store data, programmatic software code and/or other information described herein. In some embodiments, the software <NUM> may include instructions that, when executed by the processor <NUM> and/or processing circuitry <NUM>, causes the processor <NUM> and/or processing circuitry <NUM> to perform the processes described herein with respect to power device <NUM>. For example, processing circuitry <NUM> of the power device <NUM> may include monitoring unit <NUM> configured to perform one or more power device <NUM> functions as described herein such as with respect to TETS for wireless transfer of power from an external energy transfer coil to an implantable energy transfer coil, as described herein.

System <NUM> also includes external device <NUM> that may be configured to be positioned external of patient <NUM>. External device <NUM> includes hardware <NUM>. The hardware <NUM> may include a communication interface <NUM> for setting up and maintaining a wired or wireless connection with an interface of a different communication device of the system <NUM> such as with one or more of medical device <NUM>, power device <NUM> and host device <NUM>. For example, communication interface <NUM> may receive one or more of an indication of at least one determined measurable electrical characteristic, and indication of power received by the power device <NUM>, among other data and/or indications.

In the embodiment shown, the hardware <NUM> of the external device <NUM> further includes processing circuitry <NUM>.

Thus, the external device <NUM> further has software <NUM> stored internally in, for example, memory <NUM>, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the external device <NUM> via an external connection. The processing circuitry <NUM> may be configured to control any of the methods and/or processes described herein and/or to cause such methods, and/or processes to be performed, e.g., by external device <NUM>. Processor <NUM> corresponds to one or more processors <NUM> for performing external device <NUM> functions described herein. The memory <NUM> is configured to store data, programmatic software code and/or other information described herein. In some embodiments, the software <NUM> may include instructions that, when executed by the processor <NUM> and/or processing circuitry <NUM>, causes the processor <NUM> and/or processing circuitry <NUM> to perform the processes described herein with respect to power device <NUM>. For example, in one or more embodiments, processing circuitry <NUM> of the external device <NUM> may include analysis unit <NUM> configured to perform one or more external device <NUM> function such as with respect to analysis of measurement data and/or other data, as described herein. For example, external device <NUM> may determine one or more of a wireless power transfer efficiency, long term moving average of at least one measurable electrical characteristic, among other determinations, as described herein. In one or more embodiments, analysis unit <NUM> may be configured to perform similar functions of monitoring unit <NUM> but with respect to external device <NUM>. For example, analysis unit <NUM> may perform Blocks S100 and S102, described below, but with respect to a plurality of pathways in the external device <NUM>.

<FIG> is a flowchart illustrating an exemplary process of power device <NUM> according to some embodiments of the present disclosure. One or more Blocks and/or functions performed by power device <NUM> may be performed by one or more elements of power device <NUM> such as by monitoring unit <NUM> in processing circuitry <NUM>, processor <NUM>, etc. In one or more embodiments, power device <NUM> such as via one or more of processing circuitry <NUM>, processor <NUM>, monitoring unit <NUM>, communication interface <NUM>, etc. is configured to determine (Block S <NUM>) at least one measurable electrical characteristic in a plurality of electrical pathways in the power device <NUM> including an electrical pathway to the first coil, as described herein.

In one or more embodiments, power device <NUM> such as via one or more of processing circuitry <NUM>, processor <NUM>, monitoring unit <NUM>, communication interface <NUM>, etc. is configured to detect (Block S102) reduced performance in receiving wireless power signals based at least in part on the determined at least one measurable electrical characteristic, as described herein.

Alternatively or in addition to detecting reduced performed in receiving wireless power signals, processing circuitry <NUM> may detect reduced performance in using the wireless power signals and/or reduced performance in another measurable performance characteristic related to communicating wireless power signals and/or using the wireless power signals to power the medical device <NUM>.

According to one or more embodiments, the plurality of electrical pathways includes a feedthrough cables, connectors and coil windings. According to one or more embodiments, the processing circuitry <NUM> is further configured to trigger a notification if any one of the at least one measurable electrical characteristic is one of below and above a predefined threshold, or meets a predefined criterion. According to one or more embodiments, the power device <NUM> is positioned one of proximate and within the medical device <NUM>.

For example, the detection of reduced performance may be based at least on one of periodic/aperiodic monitoring and/or determining of at least one measurable electrical characteristic such as impedance/continuity checks of connections (i.e., at least one impedance value), etc..

<FIG> is a flowchart illustrating an exemplary process of external device <NUM> according to some embodiments of the present disclosure. One or more Blocks and/or functions performed by external device <NUM> may be performed by one or more elements of external device <NUM> such as by analysis unit <NUM> in processing circuitry <NUM>, processor <NUM>, etc. In one or more embodiments, external device <NUM> such as via one or more of processing circuitry <NUM>, processor <NUM>, analysis unit <NUM>, communication interface <NUM>, etc. is configured to receive (Block S104) an indication of power received by the power device <NUM>, as described herein. In one or more embodiments, external device <NUM> such as via one or more of processing circuitry <NUM>, processor <NUM>, analysis unit <NUM>, communication interface <NUM>, etc. is configured to determine (Block S106) a wireless power transfer efficiency over a predetermined period of time based at least in part on the received indication of the power received by the power device <NUM>, as described herein.

According to one or more embodiments, the wireless power transfer efficiency over the predetermined period of time corresponds to a long term moving average. According to one or more embodiments, the long term moving average indicates whether performance is degrading due to at least one non-alignment factor between the first coil <NUM> and second coil <NUM>. According to one or more embodiments, the at least one non-alignment factor includes at least one of increased fat thickness of a person in which the implantable power device <NUM> is implanted and degradation of at least one material characteristic of the implantable power device <NUM>. For example, increased fat thickness of a person may be caused by an increase in fatty tissue or subcutaneous fluid accumulation where the increased fat thickness may result in increased distance between the implanted coil and the skin surface. According to one or more embodiments, the at least one non-alignment factor includes at least one characteristic of a person that causes the distance between the implanted coil and the skin surface (or external coil) to increase. According to one or more embodiments, the processing circuitry <NUM> is further configured to trigger a notification indicating if the long term moving average meets a predefined threshold.

According to one or more embodiments, the processing circuitry <NUM> is further configured to receive an indication of the determined at least one measurable electrical characteristic, and determine a long term moving average based at least in part on the determined at least one measurable electrical characteristic. According to one or more embodiments, the processing circuitry <NUM> is further configured to determine one or more of a quality factor (Q) assessment, power transmitted assessment of power transfer efficiency versus measured temperature, long term efficiency trending (i.e., wireless power transfer efficiency) based at least in part on data and/or indications received from power device <NUM> and/or medical device <NUM>.

In one or more embodiments, the external device <NUM> may determine at least one measurable electrical characteristic associated with the external device <NUM>. For example, the at least one measurable electrical characteristic may include at least one characteristic of one or more of coil <NUM>, cable(s) of external device <NUM>, interconnects of external device <NUM>, etc. In one or more embodiments, the at least one measurable electrical characteristic is determined/measured by the external device <NUM> during one or more predefined/predetermined time periods. For example, one or more measurable electrical characteristics may be measured when there is no wireless power transfer between the power device <NUM> and external device <NUM> and/or during times when there is no wireless power being transmitted from the external device <NUM>. In one or more embodiments, the external device <NUM> may target specific predefined times to perform the measurements and/or may perform periodic measurements when wireless power transfer is not occurring. The measurements may be processed by external device <NUM> to determine whether to keep the measurements.

In one or more embodiments, the external device <NUM> may determine that there is no a metal object proximate the external device <NUM> by at least in part perform and storing measurements when the coil <NUM> is moving (e.g., the external device <NUM> may move such as based on sensor data associated with the external device <NUM> such accelerometer data), which may imply that the external device <NUM> is not positioned on an object that may be metal.

While the efficiency of energy transfer over a short time scale (i.e., a time scale below a predefined threshold) can be influenced by the alignment of the external device <NUM> and the implanted coils <NUM>, a long term average of the efficiency may be used to indicate and/or detect degrading performance. In one or more embodiments, the long term efficiency is determined by external device <NUM> based at least in part on received data and/or indications from, for example, power device <NUM>. Degrading performance could be a result of increasing fat thickness of patient <NUM> between internal/implanted coils <NUM> and external coils <NUM> or due to gradual worsening of material characteristics such as conductivity. To detect these types of degradation, the system <NUM> and/or one or more devices in system <NUM> may periodically measure and store efficiency values of the energy transfer between coils <NUM> and <NUM> that may be based at least in part on received power values reported by power device <NUM>. A long-term moving average could be compared with an average value captured near the time of implant of power device <NUM> and/or medical device <NUM>.

When the long term average crosses a threshold (either expressed as an absolute limit or a delta compared to the baseline), an automatic indication of degraded performance may be presented to the patient or clinician (via a wireless link and/or host device <NUM>). Alternatively, the long term trend of efficiency over time could be presented in a periodic programmer or CareLink report to allow the clinician (or MDT) to make more subjective assessments of degrading performance.

Power device <NUM> (i.e., implanted controller or iController) may periodically measure at least one measurable electrical characteristic such as the impedance and continuity of one or more electrical pathways that traverse through one or more of feedthroughs, connectors, header on power device <NUM> through connector, cable, coil windings of coils <NUM>. These measurements may be used to detect both sudden loss of continuity below and/or above some threshold value, or the gradual worsening of measured electrical characteristic(s). In one or more embodiments described herein, the sudden loss of continuity may correspond to an increase in impedance by at least a predefined amount and/or impedance exceeding a predefined threshold.

Further, in one or more embodiments, external device <NUM> such as via analysis unit <NUM> may be configured to periodically measure at least one measurable electrical characteristic such as the impedance and continuity of one or more electrical pathways that traverse through one or more of feedthroughs, connectors, header on external device <NUM> through connector, cable, coil windings of coils <NUM>. These measurements may be used to detect both sudden loss of continuity below and/or above some threshold value, or the gradual worsening of measured electrical characteristic(s). In one or more embodiments described herein, the sudden loss of continuity may correspond to an increase in impedance by at least a predefined amount and/or impedance exceeding a predefined threshold.

A quality factor (Q) of a coil such as external coil <NUM> may be determined by external device <NUM> based on the following: <MAT>.

A1 and A1 are illustrated in <FIG>. Q may be measured when not charging by stopping the driving of the coil and measuring ringdown, for example. Q that does not follow a normal distribution with finite range may be used to detect failure modes for power device <NUM> and/or external device <NUM>. In one or more embodiments, Q may be modeled for comparison to measured Q and/or for detecting a failure. In one or more embodiments, Q may be determined by power device <NUM> with respect to coil <NUM> as described above.

Instead of, or in addition to, having the power device <NUM> monitoring the TETS system integrity, the external system (e.g., external device <NUM>, host device <NUM>, etc.) could be used to evaluate performance degradation by monitoring efficiency and component temperature levels. For example, if the efficiency monitored by external device <NUM> is getting worse but the temperature level(s) of one or more components at power device <NUM> and/or external device <NUM> remain the same or within a predefined temperature range, then processing circuitry <NUM> may determine that the reduced efficiency is not caused by the one or more components of power device <NUM> or external device <NUM> and/or is caused by misalignment of the power device <NUM> with the external device <NUM>. In another example, if the monitored efficiency is getting worse and the temperature level(s) of one or more components are increasing and/or are outside a predefined temperature range, then processing circuitry <NUM> may determine that the reduced efficiency is caused by the one or more components of power device <NUM> and/or one or more components of external device <NUM>.

<FIG> are diagrams of coil alignment performance over various time periods in accordance with one or more embodiments of the invention. In particular, the long term alignment tracking provided by monitoring unit <NUM> and/or analysis unit <NUM> logs data related to TETS coil alignment. While not shown in <FIG>, an indicator of historical maximum achieved efficiency (and a timestamp of when that occurred) may be used to allow a longer term comparison of the current and historical efficiency. For example, data logging related to TETS coil alignment performance may occur every <NUM> minutes where the following data points are logged:.

The long term alignment trend information may be communicated to host device <NUM> and/or other device for display to a user. The display may allow for selection of views of various time periods such as <NUM> hours, <NUM> hours, <NUM> day, <NUM> days, <NUM> days, <NUM> days, <NUM> days similar to other <NUM>-minute log data such as power, speed flow, pulsitility of a device such as medical device <NUM>. If a remote monitoring transmission to CareLink has occurred, the trend is visible on the CareLink Quicklook screen as a view of the last <NUM> days; however, no data points may be logged while in Free mode (i.e., from the initial press of "intent to enter Free mode" until TETS power is reestablished for more than <NUM> minute, for example). In one or more embodiments, free mode may correspond to a time period where the power device <NUM> is utilizing implanted battery power rather than TETS power from the external device <NUM>. The log data may be stored temporarily a power device <NUM> such as via memory <NUM> until the next connection (e.g., BLUETOOTH connection) with external device <NUM> (e.g., iController), during which the log data is transmitted to external device <NUM> for long term storage.

Therefore, including one or more of the features described herein into an implanted LVAD system may provide significant hazard mitigation supporting the safety/efficacy profile of the system, increase patient/clinician confidence in the system <NUM>, among other advantages.

Firmware may correspond to software that is stored in read-only memory.

Claim 1:
A system (<NUM>), comprising:
a power device (<NUM>) implantable within a patient (<NUM>) for powering an implantable medical device (<NUM>), the power device including:
a first coil (<NUM>) configured to receive wireless power signals for powering the implantable medical device (<NUM>);
processing circuitry (<NUM>) configured to:
determine at least one measurable electrical characteristic in a plurality of electrical pathways in the power device (<NUM>) including an electrical pathway to the first coil (<NUM>); and
detect reduced performance in receiving wireless power signals based at least in part on the determined at least one measurable electrical characteristic.