Method and system for evaluating cardiac ischemia with heart rate feedback

• US 20020151811A1
• Filed: 12/26/2001
• Published: 10/17/2002
• Est. Priority Date: 06/26/2000
• Status: Active Grant

• Current Assignee: Mediwave Star Technology Incorporated
• Original Assignee: Mediwave Star Technology Incorporated
• Inventors: Starobin, Joseph M., Chernyak, Yuri B.
• Granted Patent: US 6,768,919 B2
• Time in Patent Office: Days
• US Class Current: 600/520
• CPC Class Codes: A61B 5/02405 Determining heart rate variability
• CPC Class Codes: A61B 5/0245 by using sensing means generating electric signals, i.e. ECG signals
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/366 Detecting abnormal QRS complex, e.g. widening

Abstract

A method of assessing cardiac ischemia in a subject to provide a measure of cardiac or cardiovascular health in that subject is described herein. The method comprises the steps of: (a) collecting a first RR-interval data set from the subject during a stage of gradually increasing heart rate (e.g., a stage of gradually increasing exercise load); (b) collecting a second RR-interval data set from the subject during a stage of gradually decreasing heart rate (e.g., a stage of gradually decreasing exercise load); (c) comparing the first RR-interval data set to the second RR-interval data set to determine the difference between the data sets; and (d) generating from the comparison of step (c) a measure of cardiac ischemia during exercise in the subject. A greater difference between the first and second data sets indicates greater cardiac ischemia and lesser cardiac or cardiovascular health in the subject. Heart rate is gradually increased and gradually decreased in response to actual heart rate date collected from concurrent monitoring of the subject. The data sets are collected in such a manner that they reflect almost exclusively the conduction in the heart muscle and minimize the effect on the data sets of rapid transients due to autonomic nervous system and hormonal control.

Claims

1. A method of assessing cardiac ischemia in a subject to provide a measure of cardiac or cardiovascular health in that subject, said method comprising the steps of:

(a) collecting a first RR-interval data set from said subject during a stage of gradually increasing heart rate, said heart rate being gradually increased by increasing the exercise load of said subject in response to actual heart rate data collected from concurrent monitoring of said subject;

(b) collecting a second RR-interval data set from said subject during a stage of gradually decreasing heart rate, said heart rate being gradually decreased by decreasing the exercise load of said subject in response to actual heart rate data collected from concurrent monitoring of said subject;

(c) comparing said first RR-interval data set to said second RR-interval data set to determine the difference between said data sets; and

(d) generating from said comparison of step (c) a measure of cardiac ischemia during stimulation in said subject, wherein a greater difference between said first and second data sets indicates greater cardiac ischemia and lesser cardiac or cardiovascular health in said subject.

2. The method according to claim 1, wherein said first and second RR-interval data sets are collected without an intervening rest period.

3. The method according to claim 1, wherein said stage of gradually increasing heart rate and gradually decreasing heart rate are each at least 3 minutes in duration.

4. The method according to claim 1, wherein said stage of gradually increasing heart rate and said stage of gradually decreasing heart rate are together carried out for a total time of from 6 minutes to 40 minutes.

5. The method according to claim 1, wherein:

both said stage of gradually increasing heart rate and said stage of gradually decreasing heart rate are carried out between a peak rate and a minimum rate; and

said peak rates of both said stage of gradually increasing heart rate and said stage of gradually decreasing heart rate are substantially the same.

6. The method according to claim 5, wherein:

said minimum rates of both said stage of gradually increasing heart rate and said stage of gradually decreasing heart rate are the same.

7. The method according to claim 1, wherein said stage of gradually decreasing heart rate is carried out at at least three different heart-rate stimulation levels.

8. The method according to claim 7, wherein said stage of gradually increasing heart rate is carried out at at least three different heart-rate stimulation levels.

9. The method according to claim 1, wherein said stage of gradually increasing heart rate and said stage of gradually decreasing heart rate are carried out sequentially in time.

10. The method according to claim 1, wherein said stage of gradually increasing heart rate and said stage of gradually decreasing heart rate are carried out separately in time.

11. The method according to claim 1, wherein said generating step is carried out by generating curves from each of said data sets.

12. The method according to claim 1, wherein said heart rate during said stage of gradually increasing heart rate does not exceed more than 120 beats per minute.

13. The method according to claim 1, wherein said heart rate during said stage of gradually increasing heart rate exceeds 120 beats per minute.

14. The method according to claim 1, further comprising the step of:

(e) comparing said measure of cardiac ischemia during stimulation to at least one reference value; and

then

(f) generating from said comparison of step (e) a quantitative indicium of cardiac or cardiovascular health for said subject.

15. The method according to claim 1, further comprising the step of assessing from said quantitative indicium the likelihood that said subject is at risk to experience a future ischemia-related cardiac incident.

16. The method according to claim 1, wherein:

said first RR-interval data set comprises a first QT- and RR-interval data set; and

said second RR-interval data set comprises a second QT and RR-interval data set.

18. The apparatus according to claim 17, wherein:

said first RR-interval data set comprises a first QT- and RR-interval data set; and

said second RR-interval data set comprises a second QT and RR-interval data set.

19. The apparatus according to claim 17, further comprising:

(f) means for comparing said first RR-interval data set to said second RR-interval data set to determine the difference between said data sets; and

(g) means for generating from said comparison of step f a measure of cardiac ischemia during stimulation in said subject, wherein a greater difference between said first and second data sets indicates greater cardiac ischemia and lesser cardiac or cardiovascular health in said subject.

20. The apparatus according to claim 19, wherein said generating is carried out by generating curves from each of said data sets.

21. The apparatus according to claim 20, wherein said generating is carried out by comparing the shapes of said curves from said data sets.

22. The apparatus according to claim 20, wherein said generating is carried out by determining a measure of the domain between said curves.

23. The apparatus according to claim 20, wherein said generating is carried out by both comparing the shapes of said curves from said data sets and determining a measure of the domain between said curves.

24. The apparatus according to claim 20, wherein said exercise apparatus is a treadmill.

25. The apparatus according to claim 20, wherein said exercise apparatus is a stationary cycle.

17. An apparatus for assessing cardiac ischemia in a subject to provide a measure of cardiac or cardiovascular health in that subject, said apparatus comprising:

(a) an exercise apparatus;

(b) a heart rate monitor for providing heart rate data from said subject;

(c) a controller operatively associated with said exercise apparatus and said heart rate monitor, with said controller configured to (i) gradually increase the load of said exercise apparatus in response to heart rate data from said subject to produce a stage of gradually increasing heart rate in said subject, and then (ii) gradually decrease the load of said exercise apparatus in response to heart rate data from said subject to produce a stage of gradually decreasing heart rate in said subject;

(d) means for collecting a first RR-interval data set from said subject during said stage of gradually increasing heart rate; and

(e) means for collecting a second RR-interval data set from said subject during said stage of gradually decreasing heart rate.