METHOD AND APPARATUS FOR DETECTING ARRHYTHMIAS IN A SUBCUTANEOUS MEDICAL DEVICE

• US 20070232944A1
• Filed: 07/31/2006
• 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 7,991,471 B2
• Time in Patent Office: Days
• US Class Current: 600/509
• 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 forming a first sensing vector and a second sensing vector, advancing from a first state to a second state in response to processing of an interval associated with a cardiac cycle of the sensed cardiac signals, and advancing from the second state in response to processing of a cardiac signal sensed during a predetermined sensing window.

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;

advancing from a first state to a second state in response to processing of an interval associated with a cardiac cycle of the sensed cardiac signals; and

advancing from the second state in response to processing of a cardiac signal sensed during a predetermined sensing window.

2. The method of claim 1, wherein the processing of the cardiac signal sensed during a predetermined sensing window comprises determining whether a morphology of the cardiac signal sensed during the predetermined sensing window is associated with the cardiac event.

3. The method of claim 1, further comprising:

determining, while in the first state, a first heart rate corresponding to the first sensing vector and a second heart rate corresponding to the second sensing vector in response to the interval associated with a cardiac cycle of the sensed cardiac signals;

advancing from the first state to the second state in response to both the first heart rate and the second heart rate being greater than a predetermined threshold.

4. The method of claim 3, further comprising:

advancing from the second state to the first state in response to a morphology of the cardiac signal sensed during the predetermined sensing window not being associated with the cardiac event; and

advancing from the second state to a third state in response to the morphology of the cardiac signal sensed during the predetermined sensing window being associated with the cardiac event.

5. The method of claim 4, further comprising remaining in the second state in response to the morphology of the cardiac signal sensed during the predetermined sensing window not being associated with the cardiac event and the first heart rate and the second heart rate being greater than the predetermined threshold subsequent to the advancing from the first state to the second state.

6. The method of claim 3, further comprising:

determining, while in the second state, a third heart rate corresponding to the first sensing vector and a fourth heart rate corresponding to the second sensing vector in response to an interval, associated with a cardiac cycle of the sensed cardiac signals, occurring subsequent to the predetermined sensing window.

7. The method of claim 3, further comprising:

determining, while in the second state, a third heart rate corresponding to the first sensing vector and a fourth heart rate corresponding to the second sensing vector in response to an interval, associated with a cardiac cycle of the sensed cardiac signals, timed with an end of the predetermined sensing window.

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

9. The method of claim 1, wherein the interval associated with a cardiac cycle of the sensed cardiac signals is an R-R interval.

10. 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;

advancing from a first state to a second state in response to an interval associated with cardiac signals sensed along the first sensing vector and along the second sensing vector;

determining, while in the second state, whether a cardiac signal sensed during a plurality of predetermined sensing windows corresponds to the cardiac event; and

advancing from the second state in response a predetermined number of the plurality of predetermined sensing windows corresponding to the cardiac event.

11. The method of claim 10, wherein the predetermined number of the plurality of predetermined sensing windows corresponding to the cardiac event is one of two predetermined sensing windows and two out of three predetermined sensing windows for both the first sensing vector and the second sensing vector.

12. The method of claim 10, wherein the determining while in the second state comprises determining whether a morphology of the cardiac signals sensed during the plurality of predetermined sensing window is associated with the cardiac event.

13. The method of claim 10, further comprising:

determining, while in the first state, a first heart rate corresponding to the first sensing vector and a second heart rate corresponding to the second sensing vector in response to an interval associated with a cardiac cycle of the sensed cardiac signals;

advancing from the first state to the second state in response to both the first heart rate and the second heart rate being greater than a predetermined threshold.

14. The method of claim 13, further comprising:

advancing from the second state to the first state in response to the predetermined number of the plurality of predetermined sensing windows not corresponding to the cardiac event;

advancing from the second state to a third state in response to the predetermined number of the plurality of predetermined sensing windows corresponding to the cardiac event; and

remaining in the second state in response to the predetermined number of the plurality of predetermined sensing windows not corresponding to the cardiac event and the first heart rate and the second heart rate being greater than the predetermined threshold subsequent to the advancing from the first state to the second state.

15. The method of claim 13, further comprising:

determining, while in the second state, a third heart rate corresponding to the first sensing vector and a fourth heart rate corresponding to the second sensing vector in response to an interval associated with cardiac signals sensed along the first sensing vector and along the second sensing vector subsequent to the predetermined sensing window.

16. The method of claim 13, further comprising:

determining, while in the second state, a third heart rate corresponding to the first sensing vector and a fourth heart rate corresponding to the second sensing vector in response to an interval associated with cardiac signals sensed along the first sensing vector and along the second sensing vector timed with an end of the predetermined sensing window.

17. The method of claim 10, wherein the plurality of predetermined sensing window are between 0.5 and 10 seconds.

18. The method of claim 10, wherein the interval associated with cardiac signals is an R-R interval.

27. The method of claim 10, wherein the interval associated with a cardiac cycle of the sensed cardiac signals is an R-R interval.

19. An implantable medical device, comprising:

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

a processor processing an interval associated with a cardiac cycle of the sensed cardiac signals; and

a control unit controlling the device to advance from a first state to a second state in response to an interval associated with a cardiac cycle of the sensed cardiac signals and to advance from the second state in response to processing of a cardiac signal sensed during a predetermined sensing window.

20. The device of claim 19, wherein the device is positioned non-transvenously.

21. The device of claim 19, wherein the processor determines, while the device is in the second state, whether a cardiac signal sensed during a plurality of predetermined sensing windows corresponds to the cardiac event, and the control unit causes the device to advance from the second state in response the processor determining that a predetermined number of the plurality of predetermined sensing windows correspond to the cardiac event.

22. The device of claim 19, wherein the processor determines, while the device is in the first state, a first heart rate corresponding to the first sensing vector and a second heart rate corresponding to the second sensing vector in response to an interval associated with a cardiac cycle of the sensed cardiac signals, and the control unit causes the device to advance from the first state to the second state in response to both the first heart rate and the second heart rate being greater than a predetermined threshold.

23. The device of claim 22, wherein the control unit causes the device to advance from the second state to the first state in response to the predetermined number of the plurality of predetermined sensing windows not corresponding to the cardiac event, from the second state to a third state in response to the predetermined number of the plurality of predetermined sensing windows corresponding to the cardiac event, remain in the second state in response to the predetermined number of the plurality of predetermined sensing windows not corresponding to the cardiac event and the first heart rate and the second heart rate being greater than the predetermined threshold subsequent to the advancing from the first state to the second state.

24. The device of claim 22, wherein the processor determines, while in the second state, a third heart rate corresponding to the first sensing vector and a fourth heart rate corresponding to the second sensing vector in response to an interval associated with cardiac signals sensed along the first sensing vector and along the second sensing vector subsequent to the predetermined sensing window.

25. The device of claim 22, wherein the processor determines, while in the second state, a third heart rate corresponding to the first sensing vector and a fourth heart rate corresponding to the second sensing vector in response to an interval associated with cardiac signals sensed along the first sensing vector and along the second sensing vector timed with an end of the predetermined sensing window.

26. The device of claim 21, wherein the predetermined sensing window is between 0.5 and 10 seconds.

28. A computer readable medium having computer executable instructions for performing a method comprising:

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

advancing from a first state to a second state in response to processing of an interval associated with a cardiac cycle of the sensed cardiac signals; and

advancing from the second state in response to processing of a cardiac signal sensed during a predetermined sensing window.