METHOD AND APPARATUS FOR REDUCING NOISE IN A MEDICAL DEVICE

• US 20120108990A1
• Filed: 10/29/2010
• Published: 05/03/2012
• Est. Priority Date: 10/29/2010
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Stadler, Robert W., Houben, Richard P.M., Jongen, Tim Dirk Jan
• Granted Patent: US 9,480,844 B2
• Time in Patent Office: Days
• US Class Current: 600/509
• CPC Class Codes: A61N 1/3621 for treating or preventing abnormally high heart rate
• CPC Class Codes: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371

Abstract

A method and apparatus for detecting a cardiac event in a medical device that includes sensing a cardiac signal, detecting a cardiac event in response to the sensed signal, determining whether an interval associated with the cardiac signal is less than an interval threshold, determining a noise metric in response to an interval associated with the cardiac signal being less than the interval threshold, determining whether the noise metric is greater than a noise metric threshold, and determining whether to inhibit detecting in response to determining whether an interval associated with the cardiac signal is less than the interval threshold and determining whether the noise metric is greater than the noise metric threshold.

Claims

1. A method of detecting a cardiac event in a medical device, comprising:

sensing a cardiac signal;

detecting a cardiac event in response to the sensed signal;

determining whether an interval associated with the cardiac signal is less than an interval threshold;

determining a noise metric in response to an interval associated with the cardiac signal being less than the interval threshold;

determining whether the noise metric is greater than a noise metric threshold; and

determining whether to inhibit the detecting in response to determining whether an interval associated with the cardiac signal is less than the interval threshold and determining whether the noise metric is greater than the noise metric threshold.

2. The method of claim 1, wherein determining a noise metric comprises determining, in response to an interval associated with the detected event being less than the interval threshold, the number of signal inflections associated with the cardiac signal during a predetermined noise metric window.

3. The method of claim 2, wherein determining the number of signal inflections comprises determining only change from positive signal slope to negative signal slope.

4. The method of claim 3, wherein the interval threshold corresponds to an indication of oversensing occurring during the detecting.

5. The method of claim 1, wherein determining whether to inhibit the detecting comprises:

aborting determining a noise metric and not inhibiting detecting in response to an interval associated with the cardiac signal not being less than the interval threshold;

not inhibiting detecting in response to an interval associated with the cardiac signal being less than the interval threshold and the noise metric not being greater than the noise metric threshold; and

inhibiting detecting in response to an interval associated with the cardiac signal being less than the interval threshold and the noise metric being greater than the noise metric threshold.

6. The method of claim 5, wherein inhibiting detection comprises:

inhibiting detection for a predetermined period of time; and

resuming detection in response to expiration of the predetermined time period.

7. The method of claim 5, wherein determining whether to inhibit detection further comprises:

determining whether a predetermined change in the determined noise metric has occurred; and

continuing detection in response to the predetermined change.

8. The method of claim 7, wherein the predetermined change corresponds to a reduction in the noise metric.

9. The method of claim 5, wherein determining whether to inhibit detection further comprises:

determining, during inhibiting of detection, whether an interval associated with the sensed cardiac signal is less than the interval threshold; and

resuming detection in response to an interval associated with the sensed cardiac signal being less than the interval threshold.

10. The method of claim 1, wherein the interval threshold corresponds to an indication of oversensing occurring during the detecting.

11. A medical device to detect a cardiac event, comprising:

a plurality of electrodes to sense a cardiac signal; and

a processor configured to detect the cardiac event in response to the sensed cardiac signal, determine whether an interval associated with the cardiac signal is less than an interval threshold, determine a noise metric in response to an interval associated with the cardiac signal being less than the interval threshold, determine whether the noise metric is greater than a noise metric threshold, and determine whether to inhibit detecting in response to determining whether an interval associated with the cardiac signal is less than the interval threshold and determining whether the noise metric is greater than the noise metric threshold.

12. The device of claim 11, wherein the processor is further configured to determine, in response to an interval associated with the detected event being less than the interval threshold, the number of signal inflections associated with the cardiac signal during a predetermined noise metric window.

13. The device of claim 12, wherein determining the number of signal inflections comprises determining only change from positive signal slope to negative signal slope.

14. The device of claim 13, wherein the interval threshold corresponds to an indication of oversensing occurring during the detecting.

15. The device of claim 11, wherein the processor is further configured to abort determining the noise metric and not inhibit detecting in response to an interval associated with the cardiac signal not being less than the interval threshold, not inhibit detecting in response to an interval associated with the cardiac signal being less than the interval threshold and the noise metric not being greater than the noise metric threshold, and inhibiting the detecting in response to an interval associated with the cardiac signal being less than the interval threshold and the noise metric being greater than the noise metric threshold.

16. The device of claim 15, wherein the processor is further configured to inhibit detection for a predetermined period of time, and resume detection in response to expiration of the predetermined time period.

17. The device of claim 15, wherein the processor is further configured to determine whether a predetermined change in the determined noise metric has occurred, and continue detection in response to the predetermined change.

18. The device of claim 17, wherein the predetermined change corresponds to a reduction in the noise metric.

19. The device of claim 15, wherein the processor is further configured to determine, during inhibiting of detection, whether an interval associated with the sensed cardiac signal is less than the interval threshold, and resume detection in response to an interval associated with the sensed cardiac signal being less than the interval threshold.

20. The device of claim 11, wherein the interval threshold corresponds to an indication of oversensing occurring during the detecting.

21. A computer readable medium having computer executable instructions for performing a method, the method comprising:

sensing a cardiac signal;

detecting a cardiac event in response to the sensed signal;

determining whether an interval associated with the cardiac signal is less than an interval threshold;

determining a noise metric in response to an interval associated with the cardiac signal being less than the interval threshold;

determining whether the noise metric is greater than a noise metric threshold; and

determining whether to inhibit detecting in response to determining whether an interval associated with the cardiac signal is less than the interval threshold and determining whether the noise metric is greater than the noise metric threshold.