Tet system for implanted medical device

• US 20100063347A1
• Filed: 09/10/2009
• Published: 03/11/2010
• Est. Priority Date: 09/10/2008
• Status: Active Grant

• Current Assignee: Heartware,Inc. (Medtronic Plc)
• Original Assignee: Heartware,Inc. (Medtronic Plc)
• Inventors: Batty, John Robert, Yomtov, Barry
• Granted Patent: US 8,608,635 B2
• Time in Patent Office: Days
• US Class Current: 600/17
• CPC Class Codes: A61M 2205/8243 by induction
• CPC Class Codes: A61M 60/148 in line with a blood vessel using resection or like techniques, e.g. permanent endovascular heart assist devices
• CPC Class Codes: A61M 60/178 drawing blood from a ventricle and returning the blood to the arterial system via a cannula external to the ventricle, e.g. left or right ventricular assist devices
• CPC Class Codes: A61M 60/216 including a rotating member acting on the blood, e.g. impeller
• CPC Class Codes: A61M 60/508 Electronic control means, e.g. for feedback regulation
• CPC Class Codes: A61M 60/538 Regulation using real-time blood pump operational parameter data, e.g. motor current
• CPC Class Codes: A61M 60/873 specially adapted for wireless or transcutaneous energy transfer [TET], e.g. inductive charging
• CPC Class Codes: A61M 60/875 specially adapted for optimising alignment of external and implantable coils
• CPC Class Codes: A61M 60/876 Implantable batteries
• CPC Class Codes: H02J 13/00022 using wireless data transmission
• CPC Class Codes: H02J 2310/23 The load being a medical device, a medical implant, or a life supporting device
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02J 7/00034 Charger exchanging data with an electronic device, i.e. telephone, whose internal battery is under charge
• CPC Class Codes: H02J 7/0068 Battery or charger load switching, e.g. concurrent charging and load supply H02J7/0013 takes precedence

Abstract

A TET system is provided which is operable to vary an amount of power transmitted from an external power supply to an implantable power unit in accordance with a monitored condition of the implantable power unit. In such way, the amount of power supplied to the implantable power unit for operating a pump, for example, can be varied in accordance with a cardiac cycle, so as to maintain the monitored condition in the power circuit within a desired range throughout the cardiac cycle.

Claims

1. A circulatory assist device comprising:

(a) a pump having an electric motor, the pump having a power demand which varies with the cardiac cycle of a patient in which the pump is implanted;

(b) an implantable power unit adapted for mounting within the body of the patient, the supply having a secondary coil, a power circuit connected to the secondary coil for supplying power to the pump so that power applied to the secondary coil can be transmitted to the pump, and a monitoring circuit operable to monitor a condition of the power circuit and send a transcutaneous telemetry signal representing the monitored condition,

(c) an external power supply having a primary coil adapted for transcutaneous inductive coupling with the secondary coil, a drive circuit operable to apply an alternating current to the primary coil, and a control circuit operable to receive the telemetry signal and adjust the alternating current in the primary coil at least in part in response to the telemetry signal,

the monitoring circuit and control circuit being operable to monitor the condition of the power circuit and adjust the alternating current in the primary coil in accordance therewith so as to vary the alternating current in the primary coil substantially in accordance with the cardiac cycle.

3. A device as claimed in claim 1 or claim 2, wherein the monitoring and control circuit are operable to monitor the condition of the power circuit in response to a change in coupling between the primary and secondary coils and adjust the alternating current in the primary coil so as to vary the alternating current in the primary coil substantially in accordance with the change in coupling and maintain the power circuit within the desired range despite the change in coupling.

4. A device as claimed in claim 1 or claim 2, wherein the monitoring circuit is arranged to monitor the condition of the power circuit and send the telemetry signal at least 50 times per second.

5. A device as claimed in claim 1 or claim 2, wherein the monitored condition includes a voltage supplied by the secondary coil.

6. A device as claimed in claim 1 or claim 2, wherein the power circuit includes a rectifier having an input and an output and the monitored condition includes a voltage at the output of the rectifier.

7. A device as claimed in claim 6, further comprising a non-ferromagnetic ceramic housing containing the rectifier.

8. A device as claimed in claim 6, wherein the rectifier is a Schottky diode bridge rectifier.

9. A device as claimed in claim 6, wherein the power circuit of the implantable unit further includes an overvoltage protection element operable to connect a shunt across the input of the rectifier if the voltage at the output of the rectifier exceeds the overvoltage value, the overvoltage protection element being operable to disable the power circuit if the voltage at the output of the rectifier exceeds a predetermined overvoltage value and re-enable the power circuit if the voltage at the output of the rectifier drops below a restoration value less than the overvoltage value.

10. A device as claimed in claim 1 or claim 2, wherein the power circuit further includes a battery and a routing circuit arranged to route power from the secondary coil to the motor, to the battery or both when power is received through the secondary coil and from the battery to the motor when power is not received by the secondary coil, and wherein the monitoring circuit and control circuit are operable to vary the current in the primary coil so as to maintain the condition within the desired range during the charging operation and during operation when the battery is fully charged.

11. A device as claimed in claim 1 or claim 2, wherein the monitoring circuit further includes a temperature sensor operable to detect a temperature within the implantable power unit.

12. A device as claimed in claim 11, wherein the monitoring circuit is arranged to reduce a supply of current by the power circuit to at least one of the pump or an implanted battery coupled to the implantable power unit when the detected temperature exceeds a threshold.

13. A device as claimed in claim 1 or claim 2, wherein the drive circuit is operable to apply the alternating current to the primary coil at a first frequency, and the monitoring circuit is operable to send the telemetry signal at a frequency different from the first frequency.

14. A device as claimed in claim 13, wherein the monitoring circuit includes a first transmitter and a second transmitter and is operable to send a first telemetry signal via the first transmitter and is operable to send a second telemetry signal via the second transmitter when there is a problem in transmitting the first telemetry signal.

15. A device as claimed in claim 13, wherein the control circuit is operable to automatically adjust the first frequency to adjust a resonance between the primary and secondary coils for efficient and stable transmission of power between the primary and secondary coils.

16. A device as claimed in claim 15, wherein the control circuit is operable to receive the telemetry signal and adjust the alternating current in the primary coil at a sufficient rate such that the implantable power unit can operate without an implanted battery for supplying power to the pump.

2. A circulatory assist device comprising:

(a) an implantable pump adapted for mounting within the body of the patient, the pump having an electric motor with a time-varying power demand;

(b) an implantable power unit adapted for mounting within the body of the patient, the supply having a secondary coil, a power circuit connected to the secondary coil for supplying power to the pump so that power applied to the secondary coil can be transmitted to the pump, and a monitoring circuit operable to monitor a condition of the power circuit and send a transcutaneous telemetry signal representing the monitored condition,

(c) an external power supply having a primary coil adapted for transcutaneous inductive coupling with the secondary coil, a drive circuit operable to apply an alternating current to the primary coil, and a control circuit operable to receive the telemetry signal and adjust the alternating current in the primary coil at least in part in response to the telemetry signal,

wherein the control circuit is operable to adjust the alternating current in the primary coil in response to the telemetry signal so as to vary the alternating current in the primary coil substantially in accordance with the monitored condition and maintain the monitored condition in the power circuit within a desired range.

17. A system, comprising:

(a) an implantable electrical device adapted for mounting within the body of the patient;

(b) an implantable power unit adapted for mounting within the body of the patient, the power unit having a receiving coil, a power circuit connected to the receiving coil so that power applied to the receiving coil can be transmitted to the implantable device;

(c) an external power supply having a transmitting coil adapted for transcutaneous inductive coupling with the receiving coil to define a system having a resonant frequency varying in relation to a distance between the transmitting and receiving coils, a drive circuit operable to apply an alternating current to the transmitting coil at a variable drive pulse width, and a control circuit operable to (i) monitor a parameter related to mutual inductance between the transmitting and receiving coils; and

(ii) adjust the variable transmission frequency to a value having a predetermined difference from the resonant frequency, so as to maintain the transmission frequency with a predetermined difference from the resonant frequency.

18. A system as claimed in claim 17, wherein the control circuit is operable to maintain the transmission frequency below the resonant frequency.

19. A system as claimed in claim 18, wherein the predetermined difference is a percentage difference from the resonant frequency.

20. A system as claimed in claim 17, wherein the control circuit is operable to adjust the variable transmission frequency from a current value to a new value different from the current value when the difference between the new and current values is greater than a threshold.

21. A system as claimed in claim 20, wherein the control circuit includes a table storing a plurality of frequency values corresponding to different values of the monitored parameter, wherein the control circuit is operable to use the monitored parameter to look up the new value from the table.

22. A system as claimed in claim 17, wherein the monitored parameter includes an estimate of the distance between the transmitting and receiving coils.

23. A system as claimed in claim 22, wherein the control circuit is operable to estimate the distance using at least a measurement of a voltage across the transmitting coil.

24. A system as claimed in claim 23, wherein the control circuit is operable to estimate the distance by also using a measurement of current supplied to the transmitting coil.

25. A system as claimed in claim 17, wherein the implantable device is a circulatory assist pump having an electric motor with a time-varying power demand.

26. A circulatory assist device comprising:

(a) a pump having an electric motor with a power demand varying substantially in accordance with a cardiac cycle of a patient in which the pump is implanted;

(b) an implantable power unit adapted for mounting within the body of the patient, the implantable unit having a secondary coil, a power circuit connected to the secondary coil for supplying power to the pump so that power applied to the secondary coil can be transmitted to the pump, and a monitoring circuit operable to monitor a condition of the power circuit and send a transcutaneous telemetry signal representing the monitored condition at periodic intervals,

(c) an external power supply having a primary coil adapted for transcutaneous inductive coupling with the secondary coil, a drive circuit operable to apply an alternating current to the primary coil, a receiver operable to receive the telemetry signal, a prediction circuit operable to generate a predictive signal estimating an instantaneous power demand of the pump based upon the received telemetry signal and a signal representing at least the heartbeat of the patient, a control circuit operable to adjust the alternating current in the primary coil at least in part in response to the received telemetry signal and the predictive signal.