Implantable device for delivering cardiac drug therapy

• US 7,072,711 B2
• Filed: 11/12/2002
• Issued: 07/04/2006
• Est. Priority Date: 11/12/2002
• Status: Expired due to Fees

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Girouard, Steven D., Zhu, Qingsheng
• Primary Examiner(s): Pezzuto, Robert E.
• Assistant Examiner(s): DROESCH, KRISTEN L
• Application Number:
  US10/293,907
• Publication Number:
  US 20040093034A1
• Time in Patent Office: 1,330 Days
• Field of Search: 600508-510, 600/513, 600515-517, 607 1- 4, 607/9, 607/17, 607/25, 607/26
• US Class Current: 607/3
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/358 Detecting ST segments
• CPC Class Codes: A61M 2230/04 Heartbeat characteristics, e.g. ECG, blood pressure modulation
• CPC Class Codes: A61M 5/14276 specially adapted for implantation
• CPC Class Codes: A61M 5/1723 using feedback of body parameters, e.g. blood-sugar, pressure measurement of body parameters A61B5/00
• CPC Class Codes: A61N 1/3622 comprising two or more electrodes co-operating with different heart regions
• CPC Class Codes: A61N 1/36507 controlled by gradient or slope of the heart potential
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters
• CPC Class Codes: A61N 1/36592 controlled by the heart rate variability

Abstract

An implantable medical device in which an electrogram is recorded and analyzed in order to detect changes indicative of cardiac ischemia. Cardiac ischemia may be detected by recording an electrogram from a sensing channel of the device and comparing the recorded electrogram with a reference electrogram. If cardiac ischemia is detected, a cardiac drug such as a thrombolytic agent is delivered.

Claims

1. A method for operating a cardiac device implanted in a patient, comprising:

sensing intrinsic cardiac activity;

recording an electrogram from the sensed cardiac activity in order to detect a change indicative of cardiac ischemia;

analyzing a spectrum of intervals between heartbeats and computing an LF/HF ratio;

delivering a quantity of a cardiac drug to the patient when an ischemic condition is detected from the recorded electrogram and the LF/HF ratio exceeds a specified threshold value; and

,

wherein a change in the recorded electrogram indicative of cardiac ischemia is detected by comparing the recorded electrogram with a reference electrogram and looking for an increased current of injury in the recorded electrogram.

2. The method of claim 1 further comprising looking for an increased current of injury by cross-correlating the recorded electrogram with the reference electrogram.

3. The method of claim 1 further comprising looking for an increased current of injury by locating starting and end points of an ST segment using first and second derivatives of the recorded electrogram.

4. The method of claim 1 further comprising looking for an increased current of injury by comparing the slope of an ST segment in the recorded electrogram with an ST segment slope of the reference electrogram.

5. The method of claim 1 further comprising looking for an increased current of injury by comparing the amplitude of an ST segment with an ST segment amplitude of the reference electrogram.

6. The method of claim 1 further comprising quantifying the degree of ischemia and delivering a cardiac drug only when the degree of ischemia is above a programmable threshold value.

7. The method of claim 1 wherein the cardiac drug is a thrombolytic drug.

8. The method of claim 1 further comprising:

measuring the patient'"'"'s respiratory rate; and

,

delivering a cardiac drug only when an ischemic condition is detected from the recorded electrogram and the respiratory rate is above a specified threshold value.

9. The method of claim 1 further comprising:

measuring the patient'"'"'s activity level; and

,

delivering a cardiac drug only when an ischemic condition is detected from the recorded electrogram and the measured activity level is below a specified threshold value.

11. The device of claim 1 wherein the circuitry to detect a change in the recorded electrogram cross-correlates the recorded electrogram with the reference electrogram.

12. The device of claim 1 the circuitry to detect a change in the recorded electrogram locates starting and end points of an ST segment using first and second derivatives of the recorded electrogram.

13. The device of claim 1 wherein the circuitry to detect a change in the recorded electrogram compares the slope of an ST segment in the recorded electrogram with an ST segment slope of the reference electrogram.

14. The device of claim 1 wherein the circuitry to detect a change in the recorded electrogram compares the amplitude of an ST segment with an ST segment amplitude of the reference electrogram.

15. The device of claim 1 wherein the circuitry to detect a change in the recorded electrogram quantifies the degree of ischemia and further wherein the circuitry to actuate the drug delivery apparatus does so only when the degree of ischemia is above a programmable threshold value.

16. The device of claim 1 wherein the cardiac drug is a thrombolytic drug.

17. The device of claim 1 further comprising a minute ventilation sensor to measure a patient'"'"'s respiratory rate and wherein the circuitry to actuate the drug delivery apparatus does so only when an ischemic condition is detected from the recorded electrogram and the respiratory rate is above a specified threshold value.

18. The device of claim 1 further comprising an accelerometer to measure a patient'"'"'s activity level and wherein the circuitry to actuate the drug delivery apparatus does so only when an ischemic condition is detected from the recorded electrogram and the measured activity level is below a specified threshold value.

10. An implantable cardiac device, comprising:

a sensing channel to sense cardiac activity;

a pacing channel to deliver pacing pulses;

circuitry to record an electrogram from the sensing channel of an evoked response to a pace and to detect a change in the recorded electrogram indicative of cardiac ischemia by comparing the recorded electrogram with a reference electrogram;

circuitry to analyze a spectrum of intervals between heartbeats detected by the sensing channel and to compute an LF/HF ratio;

a drug delivery apparatus to deliver a quantity of a cardiac drug; and

,

circuitry to actuate the drug delivery apparatus upon detection of a change in the recorded electrogram indicative of cardiac ischemia and when the LF/HF ratio exceeds a specified threshold value.

19. An implantable cardiac device, comprising:

means for sensing intrinsic cardiac activity;

means for recording an electrogram from the sensed cardiac activity in order to detect a change indicative of cardiac ischemia;

means for analyzing a spectrum of intervals between heartbeats and computing an LF/HF

means for delivering a quantity of a cardiac drug to the patient when an ischemic condition is detected from the recorded electrogram and the LF/HF ratio exceeds a specified threshold value; and

,

means for detecting a change in the recorded electrogram indicative of cardiac ischemia by comparing the recorded electrogram with a reference electrogram representative of cardiac ischemia.

20. The device of claim 19 further comprising means for cross-correlating the recorded electrogram with the reference electrogram.

21. The device of claim 19 further comprising means for locating starting and end points of an ST segment using first and second derivatives of the recorded electrogram.

22. The device of claim 19 further comprising means for comparing the slope of an ST segment in the recorded electrogram with an ST segment slope of the reference electrogram.

23. The device of claim 19 further comprising means for comparing the amplitude of an ST segment with an ST segment amplitude of the reference electrogram.

24. The device of claim 19 further comprising means for quantifying the degree of ischemia and delivering a cardiac drug only when the degree of ischemia is above a programmable threshold value.

25. The device of claim 19 wherein the cardiac drug is a thrombolytic drug.

26. The device of claim 19 further comprising:

means for measuring the patient'"'"'s respiratory rate; and

,

means for delivering a cardiac drug only when an ischemic condition is detected from the recorded electrogram and the respiratory rate is above a specified threshold value.

27. The device of claim 19 further comprising:

means for measuring the patient'"'"'s activity level; and

,

means for delivering a cardiac drug only when an ischemic condition is detected from the recorded electrogram and the measured activity level is below a specified threshold value.