System and method for distinguishing among cardiac ischemia, hypoglycemia and hyperglycemia using an implantable medical device

• US 20060167518A1
• Filed: 01/25/2005
• Published: 07/27/2006
• Est. Priority Date: 01/25/2005
• Status: Active Grant

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Inventors: Benser, Michael, Boileau, Peter, Gill, Jong, Florio, Joseph J., Bharmi, Rupinder, Min, Xiaoyi, Bornzin, Gene A.
• Granted Patent: US 7,272,436 B2
• Time in Patent Office: Days
• US Class Current: 607/25
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• 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: A61N 1/3621 for treating or preventing abnormally high heart rate
• 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 1/36557 controlled by chemical substances in blood
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting
• CPC Class Codes: A61N 1/3962 in combination with another heart therapy
• CPC Class Codes: A61N 1/39622 Pacing therapy

Abstract

Techniques are described for detecting ischemia, hypoglycemia or hyperglycemia based on intracardiac electrogram (IEGM) signals. Ischemia is detected based on a shortening of the interval between the QRS complex and the end of a T-wave (QTmax), alone or in combination with a change in ST segment elevation. Alternatively, ischemia is detected based on a change in ST segment elevation combined with minimal change in the interval between the QRS complex and the end of the T-wave (QTend). Hypoglycemia is detected based on a change in ST segment elevation along with a lengthening of either QTmax or QTend. Hyperglycemia is detected based on a change in ST segment elevation along with minimal change in QTmax and in QTend. By exploiting QTmax and QTend in combination with ST segment elevation, changes in ST segment elevation caused by hypo/hyperglycemia can be properly distinguished from changes caused by ischemia.

Claims

1. A method for use with an implantable medical device for detecting hypoglycemia in a patient in which the device is implanted, the method comprising:

tracking repolarization-based intervals between depolarization events and corresponding repolarization events within electrical cardiac signals; and

detecting an episode of hypoglycemia based a lengthening of the repolarization-based intervals.

2. The method of claim 1 wherein the repolarization-based intervals include one or more of:

intervals between QRS-complexes and peaks of corresponding T-waves (QTmax intervals) and intervals between QRS-complexes and ends of corresponding T-waves (QTend intervals).

3. The method of claim 1 further comprising tracking patient heart rate and wherein the repolarization-based intervals are normalized based on heart rate.

4. The method of claim 1

wherein tracking repolarization-based intervals is performed to track baseline intervals based on moving averages;

and

wherein detecting an episode of hypoglycemia based on significant increases in the repolarization-based intervals is performed

to detect increases relative to the baseline intervals.

5. The method of claim 4 wherein detecting an episode of hypoglycemia based on significant lengthening of repolarization-based intervals is performed based on a plurality of heartbeats.

6. The method of claim 1 further comprising:

tracking elevations of segments of the cardiac signals between depolarization events and corresponding repolarization events; and

confirming detection of an episode of hypoglycemia based on a significant change in elevation of the ST segments.

7. The method of claim 6 wherein the segment elevations are representative of the elevations of segments of cardiac signals between QRS-complexes and corresponding T-waves (ST segments).

8. The method of claim 6

wherein tracking segment elevations is performed to track a baseline elevation based on a moving average;

and

wherein confirming detection of an episode of hypoglycemia based in part on significant changes in the segment elevation is performed to detect a change relative to the baseline elevation.

9. The method of claim 1 further comprising recording diagnostic information representative of the repolarization-based intervals.

10. The method of claim 1 further comprising controlling therapy in response to the detection of an episode of hypoglycemia.

11. The method of claim 10 wherein an implantable insulin pump is provided and wherein the step of controlling therapy in response to the detection of an episode of hypoglycemia comprises controlling insulin delivery to the patient using the insulin pump.

12. The method of claim 1 further comprising generating a warning signal in response to detection of an episode of hypoglycemia.

13. The method of claim 12 wherein an implantable warning device is provided and wherein generating a warning signal comprises delivering a perceptible warning signal to the patient via the implantable warning device.

14. The method of claim 13 for use with an external warning device and wherein generating a warning signal comprises transmitting control signals to the external warning device for controlling the external device to generate warning signals for warning the patient.

15. A system for use with an implantable medical device for detecting hypoglycemia in a patient in which the device is implanted comprising:

a timing unit operative to track repolarization-based intervals representative of intervals between depolarization events and ends of corresponding repolarization events within electrical cardiac signals; and

a hypoglycemia detection unit operative to detect an episode of hypoglycemia based on a significant increase in the duration of the repolarization end-based intervals.

16. A system for use with an implantable medical device for detecting hypoglycemia in a patient in which the device is implanted comprising:

a timing unit operative to track QTmax values representative of intervals between QRS-complexes and peaks of corresponding T-waves within electrical cardiac signals, to track QTend values representative of intervals between the QRS-complexes and ends of corresponding the T-waves, and to track ST segment elevation representative of elevations of segments of the cardiac signals between S-waves and corresponding T-waves;

a hypoglycemia detection unit operative to detect an episode of hypoglycemia based on a change in ST segment elevation combined with an increase in both QTend and QTmax intervals; and

a warning system operative to warn the patient in response to detection of hypoglycemia.

17. A system for use with an implantable medical device for detecting hypoglycemia in a patient in which the device is implanted comprising:

means for tracking repolarization-based intervals between depolarization events and corresponding repolarization events within electrical cardiac signals; and

means for detecting an episode of hypoglycemia based on a lengthening of the repolarization-based intervals.

18. A method for use with an implantable medical device for distinguishing between hypoglycemia and cardiac ischemia within a patient in which the device is implanted comprising the steps of:

tracking repolarization-based intervals between depolarization events and corresponding repolarization events within electrical cardiac signals; and

tracking elevations of segments of the cardiac signals between ends of depolarization events and corresponding repolarization events; and

distinguishing an episode of hypoglycemia from an episode of cardiac ischemia based on a change in the elevations of the segments in combination with changes, if any, in the repolarization-based intervals.