Implantable stimulation device with isolating system for minimizing magnetic induction

• US 20040088012A1
• Filed: 10/30/2002
• Published: 05/06/2004
• Est. Priority Date: 10/30/2002
• Status: Active Grant

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Inventors: Kroll, Mark W., Cox, Timothy J., Salys, Scott, Schimke, Kerwyn
• Granted Patent: US 7,164,950 B2
• Time in Patent Office: Days
• US Class Current: 607/9
• CPC Class Codes: A61N 1/368 comprising more than one electrode co-operating with different heart regions A61N1/3622, A61N1/3627 take precedence
• CPC Class Codes: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents

Abstract

An implantable cardiac stimulation device is equipped with an isolation system capable of attenuating or eliminating induction currents flowing through the stimulation device by eliminating induction loops. The isolation system comprises a magnetic insulator configured to shield selected components of the stimulation device from external magnetic fields or radio-frequency (RF) signals. The magnetic insulator comprises a plurality of sensors that are configured to detect the intensity of the external magnetic fields and/or RF signals, and a switch bank that electrically isolates certain components of the stimulation device to eliminate the induction loops. The isolation system further comprises an attenuation system comprised of at least one magnetoresistor disposed along potential induction loops to attenuate induction currents when subjected to undesirable external magnetic fields and/or RF signals.

Claims

1. An implantable cardiac device comprising:

internal circuitry;

a housing that encases the internal circuitry;

a conductor connected to the internal circuitry;

an isolation system comprising;

a sensor unit that detects a presence of a magnetic field;

at least one non-filtered feedthrough that prevents a current induction loop from forming between the conductor and the housing;

at least one filtered feedthrough disposed within the housing and that protects the internal circuitry; and

a switch bank disposed inside the housing, between the non-filtered feedthrough and the filtered feedthrough, and connected to the sensor unit, to selectively disconnect an electrical conduction path from the conductor to the internal circuitry, upon sensing the presence of a predetermined magnetic field by the sensor unit.

2. The implantable cardiac device of claim 1, further comprising a controller disposed within the housing, that is coupled to the sensor unit, and that operatively controls the switch bank.

3. The implantable cardiac device of claim 2, wherein the sensor unit comprises a magnetic field sensor.

4. The implantable cardiac device of claim 3, wherein the sensor unit further comprises a radio frequency sensor that further detect the presence of a radio frequency signal.

5. The implantable cardiac device of claim 4, wherein the switch bank selectively disconnects the conduction path upon sensing the presence of the radio frequency signal by the radio frequency sensor.

6. The implantable cardiac device of claim 2, wherein the sensor unit further comprises a first radio sensor and a second radio frequency sensor;

wherein the magnetic field sensor and the first radio frequency sensor are disposed within the sealed compartment; and

wherein the second frequency sensor is disposed within the header.

7. The implantable cardiac device of claim 4, wherein the sensor unit detects the presence of any of the magnetic field or the radio frequency signal continuously.

8. The implantable cardiac device of claim 7, wherein the sensor unit detects the presence of any of the magnetic field or the radio frequency signal periodically.

9. The implantable cardiac device of claim 7, wherein the sensor unit detects the presence of any of the magnetic field or the radio frequency signal upon the controller receiving a command signal.

10. The implantable cardiac device of claim 4, wherein the switch bank comprises a switch;

and

wherein the controller causes the switch to open upon sensing the presence of the magnetic field.

11. The implantable cardiac device of claim 4, wherein the switch bank comprises a switch;

and

wherein the controller causes the switch to open upon sensing the presence of the radio frequency signal.

12. The implantable cardiac device of claim 1, wherein the conductor comprises a first conductor and a second conductor;

wherein the switch bank comprises a first switch and a second switch; and

wherein the first conductor is connected to the first switch and the second conductor is connected to the second switch.

13. The implantable cardiac device of claim 12, wherein the at least one non-filtered feedthrough comprises a first feedthrough and a second feedthrough;

and

wherein the first non-filtered feedthrough seals the first conductor, and the second non-filtered feedthrough seals the second conductor.

14. The implantable cardiac device of claim 12, wherein the at least one non-filtered feedthrough comprises a first non-feedthrough and a second non-feedthrough;

and

wherein the first non-filtered feedthrough seals the first conductor, and the second non-filtered feedthrough seals the second conductor.

15. The implantable cardiac device of claim 1, wherein the magnetic field is an external magnetic field generated by magnetic resonance imaging.

16. The implantable cardiac device of claim 4, wherein the radio frequency signal is an external radio frequency signal generated by electromagnetic interference.

17. The implantable cardiac device of claim 1, wherein the internal circuitry comprises a pulse generator;

and

further comprising an insulation coating that encapsulates the housing, at least in part, to attenuate the intensity of a sensed induction current to the pulse generator.

18. The implantable cardiac device of claim 4, wherein the sensor unit comprises a tunable radio frequency sensor.

19. The implantable cardiac device of claim 1, further comprising a timing circuitry that prevents excessive duration of induction loop interruption.

20. The implantable cardiac device of claim 1, wherein the isolation system further comprises an attenuation system disposed in series with a non-filtered feedthrough.

21. The implantable cardiac device of claim 20, wherein the attenuation system comprises at least one magnetoresistor.

22. The implantable cardiac device of claim 4, wherein the radio frequency sensor is capable of detecting electromagnetic interference in three dimensions.

23. An implantable cardiac device comprising:

internal circuitry;

a housing that encases the internal circuitry;

a conductor connected to the internal circuitry;

an isolation system comprising;

a sensor unit that detects a presence of a radio frequency signal;

at least one non-filtered feedthrough that prevents a current induction loop from forming between the conductor and the housing;

at least one filtered feedthrough disposed within the housing, that protects the internal circuitry; and

a switch bank disposed inside the housing, between the non-filtered feedthrough and the filtered feedthrough, and connected to the sensor unit to selectively disconnect an electrical conduction path from the conductor to the internal circuitry, upon sensing the presence of the radio frequency signal by the sensor unit.

24. The implantable cardiac device of claim 23, further comprising a controller disposed within the housing, that is coupled to the sensor unit, and that operatively controls the switch bank.

25. The implantable cardiac device of claim 24, wherein the switch bank selectively disconnects the conduction path upon sensing the presence of the radio frequency signal by the radio frequency sensor.

26. The implantable cardiac device of claim 25, wherein the switch bank comprises a switch;

and

wherein the controller causes the switch to open upon sensing the presence of the magnetic field.

27. The implantable cardiac device of claim 23, wherein the conductor comprises a first conductor and a second conductor;

wherein the switch bank comprises a first switch and a second switch; and

wherein the first conductor is connected to the first switch and the second conductor is connected to the second switch.

28. The implantable cardiac device of claim 27, wherein the at least one non-filtered feedthrough comprises a first feedthrough and a second feedthrough;

and

wherein the first non-filtered feedthrough seals the first conductor, and the second non-filtered feedthrough seals the second conductor.

29. The implantable cardiac device of claim 27, wherein the at least one non-filtered feedthrough comprises a first non-feedthrough and a second non-feedthrough;

and

wherein the first non-filtered feedthrough seals the first conductor, and the second non-filtered feedthrough seals the second conductor.

30. The implantable cardiac device of claim 23, wherein the sensor unit comprises a tunable radio frequency sensor.

31. An implantable cardiac device comprising:

a sealed compartment that contains an internal circuitry;

means for defining an electrical conduction path to the internal circuitry; and

means for attenuating a formation of a current induction loop, comprising;

sensing means for detecting the presence of a radio frequency signal;

means for preventing a current induction loop from forming between the means for defining and the sealed compartment;

means for protecting the internal circuitry; and

switching means for selectively disconnecting the electrical conduction path from the means for defining to the internal circuitry, upon sensing the presence of the radio frequency signal by the sensing means.

32. The implantable cardiac device of claim 31, further comprising a controller means for operatively controlling the switching means.

33. The implantable cardiac device of claim 32, wherein the switching means selectively disconnects the conduction path upon sensing the presence of the radio frequency signal by the sensing means.

34. The implantable cardiac device of claim 33, wherein the switching means comprises a switch;

and

wherein the controller means causes the switch to open upon sensing the presence of the radio frequency signal.

35. The implantable cardiac device of claim 31, wherein the means for protecting the internal circuitry comprises two capacitively filtered feedthroughs.

36. In an implantable cardiac device comprising a housing, internal circuitry within the housing, and at least one conductor connected to the circuitry, a method comprising:

preventing an induction loop from forming between the conductor and housing via a non-filtered feedthrough;

protecting the internal circuitry via a filtered feedthrough;

sensing a presence of a predetermined external field; and

disconnecting a conduction path from the conductor to the internal circuitry upon sensing the predetermined external field.