Switched safety protection circuit for an AIMD system during exposure to high power electromagnetic fields

1. An implantable medical device (AIMD), comprising:

a) a hermetically sealed and thermally or electrically conductive AIMD housing containing tissue-stimulating or biological-sensing circuits for the AIMD;

b) a hermetic feedthrough terminal supported by the AIMD housing, wherein the feedthrough comprises

at least one first conductive leadwire comprising a first conductive path, the at least one first leadwire having a distal first leadwire portion that is connectable to at least one conductor of an implantable lead and electrically isolated from the AIMD housing by an insulator, and wherein the at least one first leadwire has a proximal first leadwire end located inside the AIMD housing;

c) a single or multi-pole double throw switch residing inside the AIMD housing and being electrically couplable in series with and uncouplable from the at least one first leadwire of the first conductive path, the switch comprising a first throw end, a second throw end, and a switch pole end, wherein the switch pole end is permanently electrically coupled to the tissue-stimulating or biological-sensing circuits, and the first throw end is at and electrically connected to the proximal first leadwire end; and

d) a second conductive path permanently electrically coupled between the second throw end of the switch and the conductive AIMD housing; and

e) wherein the switch is configured to be selectively actuatable in response to a programmable telemetry signal to either electrically connect the switch pole end to the first throw end or connect the switch pole end to the second throw end.

2. The implantable medical device of claim 1 including a static magnetic field sensor, wherein the AIMD is automatically configured:

i) in a first or normal operating mode to electrically connect the switch pole end to the first throw end; and

ii) in a second or MRI operating mode when in the presence of an MRI main static field to electrically disconnect the switch pole end from the first throw end and electrically connect the switch pole end to the AIMD housing through the second throw end of the second conductive path.

3. The implantable medical device of claim 1 , including a third conductive path coupled at a first end anywhere along the first conductive path between the feedthrough terminal and the first throw end of the switch, wherein the third conductive path is coupled at a second end to the conductive AIMD housing, and wherein a frequency variable diverter element is coupled in series along the third conductive path.

4. The implantable medical device of claim 3 , wherein the frequency variable diverter element is selected from the group consisting of a low pass filter, a capacitor, a feedthrough capacitor, an LC trap filter, a Pi filter, a T filter, an LL filter, and an “n” element filter.

5. The implantable medical device of claim 3 , wherein the frequency variable diverter element comprises a high pass filter.

6. The implantable medical device of claim 5 , wherein the high pass filter comprises a capacitor or a resistor in series with a capacitor.

7. The implantable medical device of claim 3 , wherein the frequency variable diverter element comprises a plurality of LC trap filters, each LC trap filter being resonant at a different MRI RF pulsed frequency.

8. The implantable medical device of claim 3 including an EMI shield conductively coupled to the conductive AIMD housing and coaxially extending about and along the third conductive path in non-conductive relation thereto.

9. The implantable medical device of claim 1 , wherein the single or multi-pole double throw switch is selected from the group consisting of a MEMS switch, a mechanical switch, a reed switch, an electronic switch, a programmable switch, an automatically actuated switch, a Hall Effect switch, a field effect transistor (FET) switch, and a PIN diode.

10. The implantable medical device of claim 1 , wherein the tissue-stimulating or biological-sensing circuits are selected from the group consisting of non-linear circuit elements, over-voltage circuit elements, transient voltage suppression diodes, Transorbs, AIMD sensing circuits, and active implantable medical device therapy delivery circuits.

11. The implantable medical device of claim 1 , wherein the implantable medical device is selected from the group consisting of an implantable hearing device, a neurostimulator, a brain stimulator, a cardiac pacemaker, a left ventricular assist device, an artificial heart, a drug pump, a bone growth stimulator, a urinary incontinence device, a spinal cord stimulator, an anti-tremor stimulator, an implantable cardioverter defibrillator, a congestive heart failure device, a probe, a catheter, and a cardio resynchronization therapy device.

12. An implantable medical device (AIMD), comprising:

a) a hermetically sealed and thermally or electrically conductive AIMD housing containing tissue-stimulating or biological-sensing circuits for the AIMD;

b) a hermetic feedthrough terminal supported by the AIMD housing, wherein the feedthrough comprises

at least one first conductive leadwire comprising a first conductive path, the first leadwire having a distal first leadwire portion that is connectable to at least one conductor of an implantable lead and electrically isolated from the AIMD housing by an insulator, and wherein the at least one first leadwire has a proximal first leadwire end located inside the AIMD housing;

c) a single or multi-pole double throw switch residing inside the AIMD housing and being electrically couplable in series with and uncouplable from the at least one first leadwire of the first conductive path, the switch comprising a first throw end, a second throw end, and a switch pole end, wherein the switch pole end is permanently electrically coupled to the tissue-stimulating or biological-sensing circuits, and the first throw end is at and electrically connected to the proximal first leadwire end; and

d) a second conductive path permanently electrically coupled between the second throw end of the switch and the conductive AIMD housing;

e) wherein the switch is configured to be selectively actuatable in response to a programmable telemetry signal to either connect the switch pole end to the first throw end in a first or normal operating mode or connect the switch pole end to the second throw end in a second or MRI mode.

13. The implantable medical device of claim 12 including a third conductive path coupled at a first end anywhere along the first conductive path between the feedthrough terminal and the first throw end of the switch, wherein the third conductive path is coupled at a second end to the conductive AIMD housing, and wherein a frequency variable diverter element is coupled in series along the third conductive path.

14. The implantable medical device of claim 12 wherein the frequency variable diverter element is selected from the group consisting of a low pass filter, a capacitor, a feedthrough capacitor, an LC trap filter, a Pi filter, a T filter, an LL filter, and an “n” element filter.

15. The implantable medical device of claim 12 wherein the single or multi-pole double throw switch is selected from the group consisting of a HEMS switch, a mechanical switch, a reed switch, an electronic switch, a programmable switch, an automatically actuated switch, a Hall Effect switch, a field effect transistor (FET) switch, and a PIN diode.

16. The implantable medical device of claim 12 wherein the tissue-stimulating or biological-sensing circuits are selected from the group consisting of non-linear circuit elements, over-voltage circuit elements, transient voltage suppression diodes, Transorbs, AIMD sensing circuits, and active implantable medical device therapy delivery circuits.

17. An implantable medical device (AIMD), comprising:

a) a hermetically sealed and thermally or electrically conductive AIMD housing containing tissue-stimulating or biological-sensing circuits for the AIMD;

b) a hermetic feedthrough terminal supported by the AIMD housing, wherein the feedthrough comprises

at least one first conductive leadwire comprising a first conductive path, the at least one first leadwire having a distal first leadwire portion that is connectable to at least one conductor of an implantable lead and electrically isolated from the AIMD housing by an insulator, and wherein the at least one leadwire has a proximal first leadwire end located inside the AIMD housing;

c) a single or multi-pole double throw switch residing inside the AIMD housing and being electrically couplable in series with and uncouplable from the at least one first leadwire of the first conductive path, the switch comprising a first throw end, a second throw end, and a switch pole end, wherein the switch pole end is permanently electrically coupled to the tissue-stimulating or biological-sensing circuits, and the first throw end is at and electrically connected to the proximal first leadwire end; and

d) a second conductive path permanently electrically coupled between the second throw end of the switch and the conductive AIMD housing;

e) wherein the switch is configured to he automatically actuatable in response to a magnetic resonance B 0 field sensor that, in the absence of a static magnetic field, electrically connects the switch pole end to the first throw end, and in the presence of a static magnetic field, disconnects the switch pole end from the first throw end and electrically connects the switch pole end to the second throw end.

18. The implantable medical device of claim 17 including a third conductive path coupled at a first end anywhere along the first conductive path between the feedthrough terminal and the first throw end of the switch, wherein the third conductive path is coupled at a second end to the conductive AIMD housing, and wherein a frequency variable diverter element is coupled in series along the third conductive path.

19. The implantable medical device of claim 18 wherein the frequency variable diverter element is selected from the group consisting of a low pass filter, a capacitor, a feedthrough capacitor, an LC trap filter, a Pi filter, a T filter, an LL filter, and an “n” element filter.

20. The implantable medical device of claim 17 wherein the single or multi-pole double throw switch is selected from the group consisting of a MEMS switch, a mechanical switch, a reed switch, an electronic switch, a programmable switch, an automatically actuated switch, a Hall Effect switch, a field effect transistor (FET) switch, and a PIN diode.

21. The implantable medical device of claim 17 wherein the tissue-stimulating or biological-sensing circuits are selected from the group consisting of non-linear circuit elements, over-voltage circuit elements, transient voltage suppression diodes, Transorbs, AIMD sensing circuits, and active implantable medical device therapy delivery circuits.