METHOD AND APPARATUS FOR DETECTING ARRHYTHMIAS IN A SUBCUTANEOUS MEDICAL DEVICE

• US 20070233196A1
• Filed: 03/16/2007
• Published: 10/04/2007
• Est. Priority Date: 03/29/2006
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Ghanem, Raja N., Stadler, Robert W., Zhang, Xusheng
• Granted Patent: US 7,894,894 B2
• Time in Patent Office: Days
• US Class Current: 607/4
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61N 1/3621 for treating or preventing abnormally high heart rate
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion

Abstract

A method and apparatus for detecting a cardiac event in a medical device that includes sensing cardiac signals from a plurality of electrodes, the plurality of electrodes forming a first sensing vector and a second sensing vector different from the first sensing vector, determining a characteristic associated with cardiac signals sensed along the first sensing vector during a predetermined sensing window, determining the characteristic associated with cardiac signals sensed along the second sensing vector during the predetermined sensing window; comparing the determined characteristic associated with cardiac signals sensed along the first sensing vector and the determined characteristic associated with cardiac signals sensed along the second sensing vector, and delivering a therapy in response to the comparing.

Claims

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

sensing cardiac signals from a plurality of electrodes, the plurality of electrodes forming a first sensing vector and a second sensing vector different from the first sensing vector;

determining a characteristic associated with cardiac signals sensed along the first sensing vector during a predetermined sensing window;

determining the characteristic associated with cardiac signals sensed along the second sensing vector during the predetermined sensing window;

comparing the determined characteristic associated with cardiac signals sensed along the first sensing vector and the determined characteristic associated with cardiac signals sensed along the second sensing vector; and

delivering a therapy in response to the comparing.

2. The method of claim 1, wherein the characteristic is one of an amplitude of the sensed cardiac signals and a range of the sensed cardiac signals.

3. The method of claim 2, wherein the amplitude corresponds to a normalized mean rectified amplitude and the range corresponds to a spectral width.

4. The method of claim 1, wherein the predetermined sensing window is between approximately 0.5 and 10 seconds.

5. The method of claim 1, wherein the plurality of electrodes are positioned non-transvenously.

6. The method of claim 1, wherein the comparing comprises determining one of a maximum of the determined characteristic associated with cardiac signals sensed along the first sensing vector and the determined characteristic associated with cardiac signals sensed along the second sensing vector, and a minimum of the determined characteristic associated with cardiac signals sensed along the first sensing vector and the determined characteristic associated with cardiac signals sensed along the second sensing vector.

7. A medical device for detecting a cardiac event and delivering a corresponding therapy, the device comprising:

a plurality of electrodes sensing cardiac signals, the plurality of electrodes forming a first sensing vector and a second sensing vector;

an energy storage device to store energy associated with delivery of a therapy via the plurality of electrodes; and

a control unit to compare a characteristic associated with cardiac signals sensed along the first sensing vector and along the second sensing vector during a predetermined sensing window, and to deliver the therapy in response to the comparing.

8. The device of claim 7, wherein the characteristic is one of an amplitude of the sensed cardiac signals and a range of the sensed cardiac signals.

9. The device of claim 8, wherein the amplitude corresponds to a normalized mean rectified amplitude and the range corresponds to a spectral width.

10. The device of claim 7, wherein the predetermined sensing window is between approximately 0.5 and 10 seconds.

11. The device of claim 7, wherein the plurality of electrodes are positioned non-transvenously.

12. The device of claim 7, wherein the control unit determines one of a maximum of the characteristic associated with cardiac signals sensed along the first sensing vector and the characteristic associated with cardiac signals sensed along the second sensing vector, and a minimum of the characteristic associated with cardiac signals sensed along the first sensing vector and the characteristic associated with cardiac signals sensed along the second sensing vector.

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

sensing cardiac signals from a plurality of electrodes, the plurality of electrodes forming a first sensing vector and a second sensing vector different from the first sensing vector;

determining a first characteristic associated with a morphology of the cardiac signals sensed along the first sensing vector and along the second sensing vector during a predetermined sensing window;

determining a second characteristic associated with a morphology of the cardiac signals sensed along the first sensing vector and along the second sensing vector during a predetermined sensing window;

determining a maximum of the first characteristic determined for the first sensing vector and the first characteristic determined for the second sensing vector;

determining a minimum of the second characteristic determined for the first sensing vector and the second characteristic determined for the second sensing vector; and

determining whether the sensed cardiac signals are associated with the cardiac event in response to the determined maximum and the determined minimum.

14. The method of claim 13, wherein the first characteristic is an amplitude of the sensed cardiac signals and the second characteristic is a range of the sensed cardiac signals.

15. The method of claim 14, wherein the amplitude corresponds to a normalized mean rectified amplitude and the range corresponds to a spectral width.

16. The method of claim 13, wherein the predetermined sensing window is between approximately 0.5 and 10 seconds.

17. The method of claim 13, wherein the plurality of electrodes are positioned non-transvenously.

18. The method of claim 13, further comprising:

generating a threshold in response to the determined maximum and the determined minimum; and

determining whether the maximum is greater than or equal to the threshold.

19. The method of claim 18, wherein the first characteristic corresponds to a normalized mean rectified amplitude, the second characteristic corresponds to a spectral width, and the threshold corresponds to the normalized rectified mean amplitude being equal to 0.3636×

spectral width−

15.

20. The method of claim 13, wherein the first characteristic is an amplitude of the sensed cardiac signals and the second characteristic is a range of the sensed cardiac signals.

21. The method of claim 20, wherein the amplitude corresponds to a normalized mean rectified amplitude and the range corresponds to a spectral width.

22. The method of claim 13, wherein the predetermined sensing window is between approximately 0.5 and 10 seconds.

23. The method of claim 13, wherein the plurality of electrodes are positioned non-transvenously.