Ischemia detection

• US 20030158492A1
• Filed: 11/25/2002
• Published: 08/21/2003
• Est. Priority Date: 12/03/2001
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Sheldon, Todd J., Stadler, Robert W., Stylos, Lee, Nelson, Shannon D.
• Granted Patent: US 7,181,268 B2
• Time in Patent Office: Days
• US Class Current: 600/508
• CPC Class Codes: A61N 1/3627 for treating a mechanical deficiency of the heart, e.g. congestive heart failure or cardiomyopathy
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters
• CPC Class Codes: A61N 1/368 comprising more than one electrode co-operating with different heart regions A61N1/3622, A61N1/3627 take precedence

Abstract

Techniques for detection and treatment of myocardial ischemia are described that monitor both the electrical and dynamic mechanical activity of the heart to detect and verify the occurrence of myocardial ischemia in a more reliable manner. The occurrence of myocardial ischemia can be detected by monitoring changes in an electrical signal such as an ECG or EGM, and changes in dynamic mechanical activity of the heart that are sensed by an accelerometer sensor. The heart acceleration signal can be obtained from an single- or multiple-axis accelerometer and/or a pressure sensor deployed within or near the heart. The techniques correlate contractility changes detected by an accelerometer or pressure sensor with changes in the ST electrogram segment detected by the electrodes to increase the reliability of ischemia detection.

Claims

1. A method for detecting myocardial ischemia, the method characterized by:

obtaining a first signal indicative of dynamic mechanical activity of a heart;

obtaining a second signal indicative of electrical activity of the heart; and

detecting a myocardial ischemia condition based on both the first signal and the second signal.

2. A method according to claim 1, wherein obtaining the first signal includes obtaining a heart acceleration signal from an accelerometer deployed within the heart and wherein said heart acceleration signal is a peak endocardial acceleration value.

3. A method according to claim 2, further comprising the steps:

storing the peak endocardial acceleration value in a computer memory location;

after a predetermined time interval, obtaining at least one new peak endocardial acceleration value;

storing the at least one new peak endocardial acceleration signal; and

comparing the peak endocardial acceleration to the at least one new

4. A method according to claim 2, wherein the first signal and the second signal both satisfy criteria for indication of ischemia.

5. A method according to claim 4, wherein the criteria include a change in the first signal having a first predetermined relationship to a first threshold and a change in the second signal having second predetermined relationship to a second threshold.

6. A method according to claim 2, wherein said accelerometer is deployed spaced from an adjacent portion of endocardial tissue.

7. A method according to claim 6, wherein said adjacent portion of endocardial tissue is a one of the following:

a portion of transseptal tissue, a portion of right ventricle tissue, a portion of ventricular outflow tract tissue, a portion of left ventricle tissue.

8. The method of claim 2, further comprising, when myocardial ischemia is detected, generating a signal for delivery of therapy to alleviate effects of the ischemia within the heart.

9. A method according to claim 2, wherein said accelerometer is a multiple axis accelerometer.

10. A system for detecting myocardial ischemia, the system characterized by:

means for generating a first signal indicative of mechanical contractile activity of a heart from at least one implanted accelerometer disposed on, in or proximate a portion of cardiac tissue;

means for obtaining a second signal indicative of electrical activity of the heart; and

means for detecting myocardial ischemia based on both the first signal and the second signal.

11. The system of claim 10, further comprising means for controlling, when myocardial ischemia is indicated, delivery of therapy to alleviate effects of the ischemia within the heart.

12. The system of claim 10, wherein the therapy includes at least one of drug delivery, electrical stimulation, and a combination of drug delivery and electrical stimulation.

13. The system of claim 10, wherein the first signal is a heart acceleration signal sampled over a dynamic range of about 5 Hz to about 100 Hz.

14. A system according to claim 13, wherein said at least one implanted accelerometer is disposed within a chamber of the heart and said second signal comprises an ST segment signal and wherein said ST segment signal comprises either a peak-to-peak signal or a total amplitude signal.

15. A system according to claim 14, wherein said chamber of the heart is a ventricle and said at least one implanted accelerometer is coupled to a portion of the septal wall of said chamber of the heart.

16. A system according to claim 15, wherein one of said at least one implanted accelerometer is a one of the following:

a single axis accelerometer, a pair of single axis accelerometers disposed in spaced apart relation along substantially orthogonal axes, a multiple axis accelerometer.

17. A computer readable medium for storing computer implemented instructions, said instructions relating to a method for detecting myocardial ischemia, the method comprising:

a computer program instruction for obtaining a first signal indicative of dynamic mechanical activity of a heart from an accelerometer sensor;

a computer program instruction for obtaining a second signal indicative of electrical activity of the heart; and

a computer program instruction for detecting a myocardial ischemia condition based on both the first signal and the second signal.

18. A computer readable medium according to claim 17, wherein the computer program instruction for obtaining the first signal further comprises a computer program instruction for obtaining a heart acceleration signal from the accelerometer sensor and said accelerometer sensor is deployed within a chamber of the heart and wherein said heart acceleration signal is a peak endocardial acceleration value having a value over a dynamic range of about 5 Hz to about 100 Hz.

19. A computer readable medium according to claim 18, further comprising:

a computer program instruction for storing the peak endocardial acceleration value in a computer memory location;

a computer program instruction for, after a predetermined time interval, obtaining at least one new peak endocardial acceleration value;

a computer program instruction for storing the at least one new peak endocardial acceleration signal; and

a computer program instruction for comparing the peak endocardial acceleration to the at least one new peak endocardial acceleration value.

20. A computer readable medium according to claim 17, further comprising, when myocardial ischemia is detected, a computer program instruction for storing information about the myocardial ischemia in a computer memory storage location.

21. A computer readable medium according to claim 20, further comprising, when myocardial ischemia is detected, a computer program instruction for delivering therapy to a patient including at least one of:

a drug delivery therapy, an electrical stimulation therapy, a modification of ongoing electrical stimulation therapy, a combination of a drug delivery therapy and an electrical stimulation therapy.

22. A computer readable medium according to claim 18, wherein the computer program instruction for obtaining the first signal further comprises a computer program instructions for obtaining a heart acceleration signal from the accelerometer and said accelerometer sensor is integrated into an end portion of an implanted medical lead.

23. A computer readable medium according to claim 22, wherein the lead is a therapeutic lead coupled to an implanted medical device for delivery of electrical stimulation to the patient.

24. A computer readable medium of claim 22, wherein the lead is a diagnostic lead coupled to an implanted medical device for acquisition of diagnostic data.

25. A computer readable medium according to claim 18, further comprising a computer program instruction for obtaining the second signal from a subcutaneous electrode array.