Isolation Circuitry and Method for Gradient Field Safety in an Implantable Medical Device

• US 20070255332A1
• Filed: 04/26/2006
• Published: 11/01/2007
• Est. Priority Date: 04/26/2006
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Manahan, David, Cabelka, Lonny, Wahlstrand, John, Pape, Forrest
• Granted Patent: US 7,729,770 B2
• Time in Patent Office: Days
• US Class Current: 607/37
• CPC Class Codes: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents
• CPC Class Codes: A61N 1/3752 Details of casing-lead connections

Abstract

An implantable medical device is provided for isolating an elongated medical lead from internal device circuitry in the presence of a gradient magnetic or electrical field. The device includes an isolation circuit adapted to operatively connect an internal circuit to the medical lead in a first operative state and to electrically isolate the medical lead from the internal circuit in a second operative state.

Claims

1. An implantable medical device, comprising:

an internal circuit adapted to be electrically coupled to an elongated medical lead implanted in a patient'"'"'s body;

an isolation circuit adapted to operatively connect the internal circuit to the medical lead in a first operative state and to electrically isolate the internal circuit from the medical lead in a second operative state;

a control module for determining a device operating mode as one of a normal operating mode and a gradient field operating mode and for controlling the operative state of the isolation circuit in the first operative state in response to determining the normal operating mode, in the second operative state in response to determining the gradient field operating mode, and transiently switching the isolation circuit from the second operative state to the first operative state during the gradient field operating mode.

2. The implantable medical device of claim 1 wherein the internal circuit includes a pulse generating circuit and wherein the control module transiently switches the isolation circuit from the second operative state to the first operative state in response to generation of a stimulation pulse by the pulse generating circuit.

3. The implantable medical device of claim 1 wherein the isolation circuit includes one of an electro-mechanical relay, a semiconductor device, and a MEMS relay.

4. The implantable medical device of claim 1 further comprising a gradient field sensor and wherein the control module determines the gradient field operating mode in response to the gradient field sensor.

5. The implantable medical device of claim 1 further comprising a telemetry circuit for receiving commands from an external programming device and wherein the control module determines the gradient field operating mode in response to a command received by the telemetry circuit.

6. The implantable medical device of claim 1 further comprising a switching element for controlling a device function and wherein the control module controls the operative state of the isolation circuit by controlling the switching element.

7. The implantable medical device of claim 6 wherein the device function includes protecting the internal circuit from external high-voltage shocks applied to a patient.

8. A method for use in an implantable medical device, comprising:

coupling an elongated medical lead to an internal circuit by way of an isolation circuit,

determining a device operating mode as one of a normal operating mode and a gradient field operating mode;

controlling the operative state of the isolation circuit in a first operative state in response to determining the normal operating mode and in a second operative state in response to determining the gradient field operating mode; and

transiently switching the isolation circuit from the second operative state to the first operative state during the gradient field operating mode.

9. The method of claim 8 further comprising generating therapeutic stimulation pulses and transiently switching the isolation circuit from the second operative state to the first operative state in response to generating a stimulation pulse.

10. The method of claim 8 further comprising automatically detecting a gradient field and wherein the gradient field mode is determined in response to the detected gradient field.

11. The method of claim 8 further comprising receiving an externally generated command and wherein the gradient field mode is determined in response to the command.

12. The method of claim 8 further comprising controlling a switching element state for controlling a device function and wherein controlling the operative state of the isolation circuit includes controlling the switching element state.

13. The method of claim 12 wherein the device function includes protecting of an internal circuit from external high-voltage shocks applied to a patient.

16. The implantable medical device system of claim 13 wherein the connecting and isolating means includes any of an electro-mechanical relay, a semiconductor device, and a MEMS relay.

17. The implantable medical device system of claim 13 further comprising means for automatically detecting a gradient field.

18. The implantable medical device system of claim 13 further comprising means for receiving an externally generated gradient field operating mode command.

19. The implantable medical device system of claim 13 further comprising means for switchably controlling a device function and wherein the connecting and isolating means includes the means for switchably controlling the device function.

20. The implantable medical device of claim 18 wherein the device function includes protecting the internal circuit from external defibrillation shocks applied to a patient.

14. An implantable medical device system, comprising:

means for operatively connecting an elongated medical lead to an implantable medical device internal circuit in a first operative state and for electrically isolating the medical lead from the internal circuit in a second operative state;

means for determining a device operating mode as one of a normal operating mode or a gradient field operating mode; and

means for controlling the operative state of the means for operatively connecting and electrically isolating in the first operative state in response to determining the normal operating mode, in the second operative state in response to determining the gradient field operating mode, and transiently switching from the second operative state to the first operative state during the gradient field operating mode.

15. The implantable medical device system of claim 14 further comprising means for generating therapeutic electrical pulses and wherein the controlling means transiently switches the connecting and isolating means from the second operative state to the first operative state in response to the generation of electrical pulses by the pulse generating means.