SYSTEM AND METHOD FOR ISCHEMIA CLASSIFICATION WITH IMPLANTABLE MEDICAL DEVICE

• US 20080183087A1
• Filed: 01/31/2007
• Published: 07/31/2008
• Est. Priority Date: 01/31/2007
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Lu, Steven N., Song, Zhendong
• Granted Patent: US 8,798,723 B2
• Time in Patent Office: Days
• US Class Current: 600/508
• CPC Class Codes: A61B 5/0006 ECG or EEG signals
• 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: A61B 5/364 Detecting abnormal ECG interval, e.g. extrasystoles, ectopic heartbeats
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00
• 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 1/36542 controlled by body motion, e.g. acceleration

Abstract

An implantable medical device monitors ST segment data collected from EGM. ST trends are established and monitored over time. The IMD is able to discern whether the data indicate supply ischemia, demand ischemia, or other physiological causes. The IMD is then able to provide appropriate information and alerts.

Claims

1. A method comprising:

obtaining an electrogram representing cardiac data from an implantable medical device for a plurality of cardiac cycles;

determining an ST segment data point for each of the cardiac cycles;

evaluating the ST segment data points;

determining whether the evaluated ST segment data points indicate supply ischemia; and

evaluating a secondary indicator to confirm the determination.

2. The method of claim 1, wherein the secondary indicator is heart rate.

3. The method of claim 2, wherein supply ischemia is not indicated if the evaluated ST segment data points track the heart rate.

4. The method of claim 3, wherein a determination of demand ischemia is made if the ST segment data points track the heart rate.

5. The method of claim 1, wherein the secondary indicator includes a respiration rate and an activity sensor.

6. The method of claim 5, wherein supply ischemia is indicated if indicated by the ST segment data points and an increased respiration rate is sensed without a corresponding sensed increase in activity.

7. The method of claim 1, wherein the secondary indicator is a position sensor that provides postural position data.

8. The method of claim 7, wherein supply ischemia is not indicated if an abrupt postural change corresponds in time with the indication of the ST data segments.

9. The method of claim 1, wherein determining an ST segment data point further comprises:

identifying a peak of an R wave;

adding a predetermined time interval to the identified peak; and

identifying a recorded value at a time identified by the predetermined time interval after the R wave as the ST segment data point.

10. The method of claim 9, further comprising:

determining a PR isoelectric baseline value;

subtracting the PR isoelectric baseline value from the recorded value to identify the ST segment data point.

11. The method of claim 1, wherein evaluating the ST segment data points further comprises:

monitoring the ST segment data point values; and

initiating an a timer interval if a given ST segment data point value exceeds a threshold value, wherein determining whether the evaluated ST segment data points indicate supply ischemia occurs based upon data collected during the timer.

12. The method of claim 11, further comprising:

determining a maximum ST segment data point value during the timer;

determining a first time interval from initiation of the timer until the maximum ST segment data point value occurs; and

determining that the evaluated ST segment data points do not indicate supply ischemia if the first time interval is less than a first short value or greater than a first long value.

13. The method of claim 12, further comprising:

determining that the evaluated ST segment data points do not indicate supply ischemia if less than a predetermined percentage of the ST segment data point occurring during the timer interval exceed the threshold value.

14. The method of claim 12, further comprising:

determining that the evaluated ST segment data points do not indicate supply ischemia if an ST segment data point occurring at a termination of the timer interval is less than a predetermined percentage of the maximum ST segment data value.

15. The method of claim 12, further comprising:

calculating a slope of the ST segment data points prior to the maximum ST segment data point; and

determining that the evaluated ST segment data points do not indicate supply ischemia if the slope is less than a first slope value.

16. An apparatus comprising:

means for obtaining an electrogram representing cardiac data from an implantable medical device for a plurality of cardiac cycles;

means for determining an ST segment data point for each of the cardiac cycles;

means for evaluating the ST segment data points; and

means for determining whether the evaluated ST segment data points indicate supply ischemia; and

means for evaluating a secondary indicator to confirm the determination.

17. The apparatus of claim 16, further comprising:

means for sensing a heart rate as the secondary indicator; and

means for determining if the heart rate tracks the ST segment data points and identifying demand ischemia if the heart rate does tract the ST segment data points.

18. The apparatus of claim 16, further comprising:

means for sensing respiration;

means for sensing activity;

means for evaluating the sensed activity and sensed respiration as the secondary indicator and determining supply ischemia if indicated by the ST segment data points and an increase respiration rate does not correlate with the sensed activity level.

19. The apparatus of claim 16, further comprising means for monitoring patient posture and determining that supply ischemia is not present if a variation in the ST segment data points correlates with an abrupt change in posture.