EMI detection for implantable medical devices

• US 7,231,251 B2
• Filed: 08/14/2003
• Issued: 06/12/2007
• Est. Priority Date: 08/14/2003
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Babler, Luke, Yonce, David J.
• Primary Examiner(s): Evanisko; George R.
• Application Number:
  US10/642,068
• Publication Number:
  US 20050038482A1
• Time in Patent Office: 1,398 Days
• Field of Search: 607/27, 607/32, 607/60
• US Class Current: 607/27
• CPC Class Codes: A61N 1/37 Monitoring; Protecting
• CPC Class Codes: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents

Abstract

A method and system for the detection of electromagnetic interference is disclosed in which a telemetry coil or other magnetic sensor is used to detect a magnetic signal. If a magnetic signal is determined to be a non-telemetry signal and is time-correlated with the onset of an increase in heart rate, electromagnetic interference is assumed to be present.

Claims

1. A method for operating an implantable cardiac device in order to detect the presence of electromagnetic interference (EMI), comprising:

monitoring a heart rate via a sensing channel which incorporates an implanted lead;

monitoring for the presence of a magnetic signal with a magnetic sensor;

determining whether a detected magnetic signal is a magnetic noise signal or a valid telemetry signal; and

,

detecting the presence of EMI if detection of the magnetic noise signal is time-correlated with an increase in the monitored heart rate.

2. The method of claim 1 wherein the presence of EMI is detected only if the monitored heart rate increases by a specified amount and for a specified duration and if the onset of the increase is nearly simultaneous with detection of a magnetic noise signal.

3. The method of claim 1 further comprising entering a noise reversion mode upon detection of EMI.

4. The method of claim 3 wherein the noise reversion mode includes asynchronous pacing.

5. The method of claim 4 further comprising determining a detected magnetic signal to be a sync pulse if detection of the magnetic signal occurs within a specified interval with respect to an immediately previous detection of a magnetic signal.

6. The method of claim 1 wherein a magnetic signal is determined to be a telemetry signal if the magnetic signal is recognized as either a valid telemetry command or a sync pulse.

7. The method of claim 1 further comprising detecting EMI only if no valid telemetry command has been received with a specified time interval.

8. The method of claim 1 wherein the magnetic sensor is a telemetry coil.

9. The method of claim 1 wherein the magnetic sensor is used by the device to detect a static magnetic field.

10. The method of claim 9 further comprising detecting a magnetic signal only if alternating detections occur within a specified time period, indicating a time varying magnetic field.

11. An implantable cardiac device configured to detect the presence of electromagnetic interference (EMI), comprising:

means for monitoring a heart rate;

a magnetic sensor for monitoring for the presence of a magnetic signal;

means for determining whether a detected magnetic signal is a magnetic noise signal or a valid telemetry signal; and

,

means for detecting the presence of EMI if detection of the magnetic noise signal is time-correlated with an increase in the monitored heart rate.

12. The device of claim 11 wherein the presence of EMI is detected only if the monitored heart rate increases by a specified amount and for a specified duration and if the onset of the increase is nearly simultaneous with detection of a magnetic noise signal.

13. The device of claim 11 further comprising means for entering a noise reversion mode upon detection of EMI.

14. The device of claim 13 wherein the noise reversion mode includes asynchronous pacing.

15. The device of claim 14 further comprising means for determining the detected magnetic signal to be a sync pulse if detection of the magnetic signal occurs within a specified interval with respect to an immediately previous detection of a magnetic signal.

16. The device of claim 11 further comprising means for determining the magnetic signal to be a telemetry signal if the magnetic signal is recognized as either a valid telemetry command or a sync pulse.

17. The device of claim 11 further comprising means for detecting EMI only if no valid telemetry command has been received with a specified time interval.

18. The device of claim 11 wherein the magnetic sensor is a telemetry coil.

19. The device of claim 11 wherein the magnetic sensor is used by the device to detect a static magnetic field.

20. The device of claim 19 further comprising means for detecting a magnetic signal only if alternating detections occur within a specified time period, indicating a time varying magnetic field.