Ischemia detection based on cardiac conduction time

• US 20040088017A1
• Filed: 10/31/2002
• Published: 05/06/2004
• Est. Priority Date: 10/31/2002
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Sharma, Vinod, Olson, Walter H.
• Granted Patent: US 7,415,307 B2
• Time in Patent Office: Days
• US Class Current: 607/25
• CPC Class Codes: A61B 5/05 Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves impedance plethysmography A61B5/0295; measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61N 1/3629 in combination with non-electric therapy

Abstract

Methods and process for detection of myocardial ischemia involve detection and analysis of changes in electrical conduction velocity within the heart to monitor changes in the condition of the cardiac muscle and indicate possible ischemia. Conduction velocity slows considerably when oxygen supply to the heart is reduced. Analysis of electrical conduction velocity can be used to verify the occurrence of myocardial ischemia in a more reliable manner. Changes in conduction velocity may be monitored based on conduction time between electrodes positioned in the left and right ventricles of the heart. The electrodes may be endocardial or epicardial electrodes. In general, the techniques may involve launching a stimulation waveform at one electrode and sensing a local cardiac depolarization at another electrode to assess conduction time.

Claims

1. A method comprising:

detecting cardiac conduction time; and

indicating myocardial ischemia based on the detected conduction time.

2. The method of claim 1, further comprising:

launching a stimulation wave front from a first electrode positioned proximate a first ventricular chamber; and

sensing a local cardiac depolarization at a second electrode positioned proximate a second ventricular chamber,

wherein detecting cardiac conduction time includes detecting a time between launching the wave front and sensing the local cardiac depolarization.

3. The method of claim 2, wherein the first electrode includes an endocardial electrode positioned within the first ventricular chamber, and the second electrode includes an epicardial electrode positioned on a surface of the second ventricular chamber.

4. The method of claim 2, wherein the first electrode includes an endocardial electrode positioned within the first ventricular chamber, and the second electrode includes an endocardial electrode positioned within the second ventricular chamber.

5. The method of claim 2, wherein the first electrode includes an epicardial electrode positioned on a surface of the first ventricular chamber, and the second electrode includes an epicardial electrode positioned on a surface of the second ventricular chamber.

6. The method of claim 2, wherein the first ventricular chamber is the right ventricular chamber and the second ventricular chamber is the left ventricular chamber.

7. The method of claim 2, wherein the first ventricular chamber is the left ventricular chamber and the second ventricular chamber is the right ventricular chamber.

8. The method of claim 1, wherein indicating myocardial ischemia includes:

comparing the detected conduction time to a threshold conduction time; and

indicating ischemia when the detected conduction time exceeds the threshold conduction time.

9. The method of claim 8, further comprising adjusting the threshold conduction time based on a rate of change of the conduction time.

10. The method of claim 1, wherein detecting myocardial ischemia includes:

comparing the detected conduction time to a threshold conduction time;

comparing a rate of change of the detected conduction time to a range of change; and

indicating ischemia when the detected conduction time exceeds the threshold conduction time and the rate of change of the detected conduction time is within the range of change.

11. The method of claim 1, wherein indicating myocardial ischemia includes:

determining a rate of change of the detected conduction time; and

indicating ischemia based on the rate of change.

12. The method of claim 1, further comprising detecting the conduction time using at least one lead associated with an implantable medical device.

13. The method of claim 1, further comprising, when myocardial ischemia is indicated, generating a signal for delivery of therapy to alleviate effects of the ischemia within the heart.

14. The method of claim 1, further comprising, when myocardial ischemia is indicated, storing information about the myocardial ischemia for review by a physician.

15. The method of claim 1, further comprising, when myocardial ischemia is indicated, notifying a patient.

16. The method of claim 1, further comprising, when myocardial ischemia is indicated, delivering therapy to alleviate effects of the ischemia within the heart.

17. The method of claim 16, wherein the therapy includes at least one of drug delivery, electrical stimulation, modification of ongoing electrical stimulation, and a combination of drug delivery and electrical stimulation.

18. The method of claim 1, further comprising quantifying a degree of ischemia based on the detected conduction time.

19. The method of claim 1, further comprising:

detecting ST deviation; and

indicating myocardial ischemia based on the detected conduction time and the detected ST deviation.

20. The method of claim 1, further comprising:

launching a stimulation wave front from a first electrode positioned proximate a first ventricular chamber;

sensing a local cardiac depolarization at a second electrode positioned proximate a second ventricular chamber; and

evaluating a morphology of a waveform associated with the sensed depolarization,

wherein detecting cardiac conduction time includes detecting a time between launching the wave front and sensing the local cardiac depolarization, and indicating myocardial ischemia includes indicating myocardial ischemia based on the detected conduction time and the morphology.

21. The method of claim 1, further comprising:

detecting an activity level of a patient; and

indicating myocardial ischemia based on the detected conduction time and the detected activity level.

22. A device comprising a detector to detect cardiac conduction time, and indicate myocardial ischemia based on the detected conduction time.

23. The device of claim 22, further comprising:

a first electrode positioned proximate a first ventricular chamber to launch a stimulation wave front; and

a second electrode positioned proximate a second ventricular chamber to sense a local cardiac depolarization,

wherein the detector detects the cardiac conduction time based on a time between launching the wave front and sensing the local cardiac depolarization.

24. The device of claim 23, wherein the first electrode includes an endocardial electrode positioned within the first ventricular chamber, and the second electrode includes an epicardial electrode positioned on a surface of the second ventricular chamber.

25. The device of claim 23, wherein the first electrode includes an endocardial electrode positioned within the first ventricular chamber, and the second electrode includes an endocardial electrode positioned within the second ventricular chamber.

26. The device of claim 23, wherein the first electrode includes an epicardial electrode positioned on a surface of the first ventricular chamber, and the second electrode includes an epicardial electrode positioned on a surface of the second ventricular chamber.

27. The device of claim 23, wherein the first ventricular chamber is the right ventricular chamber and the second ventricular chamber is the left ventricular chamber.

28. The device of claim 23, wherein the first ventricular chamber is the left ventricular chamber and the second ventricular chamber is the right ventricular chamber.

29. The device of claim 22, wherein the detector compares the detected conduction time to a threshold conduction time, and indicates ischemia when the detected conduction time exceeds the threshold conduction time.

30. The device of claim 29, wherein the detector adjusts the threshold conduction time based on a rate of change of the conduction time.

31. The device of claim 22, wherein the detector:

compares the detected conduction time to a threshold conduction time;

compares a rate of change of the detected conduction time to a threshold rate of change; and

indicates ischemia when the detected conduction time exceeds the threshold conduction time and the rate of change of the detected conduction time is less than the threshold rate of change.

32. The device of claim 22, wherein the detector senses the conduction time using at least one lead associated with an implantable medical device.

33. The device of claim 22, wherein the detector generates a signal for delivery of therapy to alleviate effects of the ischemia within the heart when myocardial ischemia is indicated.

34. The device of claim 22, further comprising a memory to store information about the myocardial ischemia for review by a physician.

35. The device of claim 22, further comprising an alarm to notify a patient when myocardial ischemia is indicated.

36. The device of claim 22, further comprising a device to deliver therapy to alleviate effects of the ischemia within the heart when myocardial ischemia is indicated.

37. The device of claim 36, wherein the therapy includes at least one of drug delivery, electrical stimulation, modification of ongoing electrical stimulation, and a combination of drug delivery and electrical stimulation.

38. The device of claim 22, wherein the detector quantifies a degree of ischemia based on the detected conduction time.

39. The device of claim 32, wherein the detector detects ST deviation, and indicates myocardial ischemia based on the detected conduction time and the detected ST deviation.

40. The device of claim 22, further comprising:

a first electrode positioned proximate a first ventricular chamber to launch a stimulation wave front; and

a second electrode positioned proximate a second ventricular chamber to sense a local cardiac depolarization,

wherein the detector evaluates a morphology of a waveform associated with the sensed depolarization, detects the cardiac conduction time based on a time between launching the wave front and sensing the local cardiac depolarization, and indicates myocardial ischemia based on the detected conduction time and the morphology.

41. The device of claim 22, further comprising an activity level sensor to detect an activity level of a patient, wherein the detector indicates myocardial ischemia based on the detected conduction time and the detected activity level

42. A device comprising:

means for detecting cardiac conduction time; and

means for indicating myocardial ischemia based on the detected conduction time.

43. The device of claim 42, further comprising:

a first electrode for launching a stimulation wave front from a first electrode positioned proximate a first ventricular chamber; and

a second electrode for sensing a local cardiac depolarization at a second electrode positioned proximate a second ventricular chamber,

wherein the detecting means detects a time between launching the wave front and sensing the local cardiac depolarization.

44. The device of claim 43, wherein the first electrode includes an endocardial electrode positioned within the first ventricular chamber, and the second electrode includes an epicardial electrode positioned on a surface of the second ventricular chamber.

45. The device of claim 43, wherein the first electrode includes an endocardial electrode positioned within the first ventricular chamber, and the second electrode includes an endocardial electrode positioned within the second ventricular chamber.

46. The device of claim 43, wherein the first ventricular chamber is the right ventricular chamber and the second ventricular chamber is the left ventricular chamber.

47. The device of claim 43, wherein the first ventricular chamber is the left ventricular chamber and the second ventricular chamber is the right ventricular chamber.

48. The device of claim 42, wherein the detecting means compares the detected conduction time to a threshold conduction time, and indicates ischemia when the detected conduction time exceeds the threshold conduction time.

49. The device of claim 42, wherein the detecting means adjusts the threshold conduction time based on a rate of change of the conduction time.

50. A method comprising:

launching a first stimulation wave front from a first ventricular chamber;

sensing a first local cardiac depolarization in a second ventricular chamber;

detecting a first time between launching the first wave front and sensing the first local cardiac depolarization;

launching a second stimulation wave front from the second ventricular chamber;

sensing a second local cardiac depolarization in the first ventricular chamber;

detecting a second time between launching the second wave front and sensing the second local cardiac depolarization; and

indicating myocardial ischemia based on the first time and the second time.

51. The method of claim 50, further comprising indicating myocardial ischemia based on a difference between the first time and second time.

52. A device comprising:

means for launching a first stimulation wave front from a first ventricular chamber;

means for sensing a first local cardiac depolarization in a second ventricular chamber;

means for detecting a first time between launching the first wave front and sensing the first local cardiac depolarization;

means for launching a second stimulation wave front from the second ventricular chamber;

means for sensing a second local cardiac depolarization in the first ventricular chamber;

means for detecting a second time between launching the second wave front and sensing the second local cardiac depolarization; and

means for indicating myocardial ischemia based on the first time and the second time.

53. The device of claim 52, further comprising means for indicating myocardial ischemia based on a difference between the first time and second time.