DISTINGUISHING BETWEEN TREATABLE AND NON-TREATABLE HEART RHYTHMS

• US 20100274148A1
• Filed: 04/27/2009
• Published: 10/28/2010
• Est. Priority Date: 04/27/2009
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Gillberg, Jeffrey M., Stadler, Robert W., Zhang, Xusheng
• Granted Patent: US 8,855,755 B2
• Time in Patent Office: Days
• US Class Current: 600/518
• CPC Class Codes: A61B 5/35 by template matching
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/726 using Wavelet transforms
• 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 1/3621 for treating or preventing abnormally high heart rate
• CPC Class Codes: A61N 1/36507 controlled by gradient or slope of the heart potential
• CPC Class Codes: A61N 1/39622 Pacing therapy
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

Techniques are described for distinguishing between treatable and non-treatable heart rhythms. A medical device that operates in accordance with the techniques analyzes characteristics over several cardiac event intervals to detect initiation of a sudden rate onset. After detection of the initiation of the sudden rate onset, the IMD analyzes a morphology of an EGM associated with a selected cardiac event within the first several beats after the initiation of sudden rate onset. In one example, the IMD analyzes the morphology of the EGM associated with the first cardiac event immediately subsequent to the initiation of the sudden rate onset. If the morphology of the EGM of the selected cardiac event is abnormal compared to template EGM, the rhythm is classified as treatable. Otherwise, the rhythm is classified as non-treatable.

Claims

1. An implantable medical device (IMD) comprising:

a sensing module configured to acquire signals associated with cardiac events of a heart of a patient via at least one sensor; and

a processor configured to detect initiation of rate onset of a rhythm of the heart based on the acquired signals, obtain an electrogram (EGM) associated with one of the cardiac events after a location of the initiation of the rate onset, analyze a morphology of the EGM associated with the cardiac event after the location of the initiation of the rate onset, and determine whether the rhythm is indicative of a treatable rhythm based on the analysis of the morphology of the EGM.

2. The device of claim 1, wherein the processor is configured to obtain an EGM associated with a first cardiac event after the location of the initiation of the rate onset.

3. The device of claim 2, wherein the processor is configured to identify the location of the initiation of the rate onset.

4. The device of claim 1, wherein the processor is configured to detect the initiation of the rate onset of the rhythm by:

determining a plurality of cardiac event intervals;

determining a variability among a first portion of the plurality of cardiac event intervals;

determining a relative change of the first portion of the plurality of cardiac event intervals with respect to a second portion of the plurality of cardiac event intervals, wherein the first portion of the plurality of cardiac event intervals occurred more recently in time than the second portion of the plurality of cardiac event intervals; and

detecting initiation of rate onset when the computed variability is less than a variability threshold value and the computed relative change is greater than a relative change threshold value.

5. The device of claim 4, wherein the processor is configured to obtain an EGM associated with an oldest cardiac event of the first portion of the cardiac event intervals.

6. The device of claim 4, wherein the processor is configured to monitor for rate offset after detecting the initiation of the rate onset.

7. The device of claim 4, wherein the plurality of cardiac event intervals are R-R intervals corresponding to amount of time between successive R-waves.

8. The device of claim 1, wherein the processor is configured to:

compute one or more morphology parameters of the EGM associated with the cardiac event after the location of the initiation of the rate onset;

determine the rhythm is indicative of a treatable rhythm when the one or more morphology parameters have changed by threshold amounts compared to respective morphology parameters of a template EGM, and

determine the rhythm is indicative of a non-treatable rhythm when the one or more morphology parameters have not changed by threshold amounts compared to respective morphology parameters of the template EGM.

9. The device of claim 8, wherein the treatable rhythm comprises one of a ventricular tachycardia (VT) or a ventricular fibrillation (VF) and the non-treatable rhythm comprises a supra-ventricular tachycardia (SVT).

10. The device of claim 8, wherein the template EGM comprises one of an EGM of a cardiac event during normal sinus rhythm, an EGM of a cardiac event just prior to the initiation of the rate onset, or an EGM of another cardiac event after the initiation of the rate onset.

11. The device claim 8, wherein the one or more morphology parameters associated with the EGM include one or more of a matching metric, an R-wave symmetry index (RSI), a R-wave width (RW), a Q-R index (QRI), a R-wave polarity code (RPC) and a slope peak shift (SPS).

12. A method comprising:

detecting initiation of rate onset of a rhythm of a heart of a patient;

obtaining an electrogram (EGM) associated with a cardiac event after a location of the initiation of the rate onset;

analyzing a morphology of the EGM associated with the cardiac event after the location of the initiation of the rate onset; and

determining whether the rhythm is indicative of a treatable rhythm based on the analysis of the morphology of the EGM.

13. The method of claim 12, wherein obtaining the EGM associated with the cardiac event comprises obtaining an EGM associated with a first cardiac event after the location of the initiation of the rate onset.

14. The method of claim 13, further comprising identifying the location of the initiation of the rate onset.

15. The method of claim 12, wherein detecting the initiation of the rate onset of the rhythm comprises:

determining a plurality of cardiac event intervals;

determining a variability among a first portion of the plurality of cardiac event intervals;

determining a relative change of the first portion of the plurality of cardiac event intervals with respect to a second portion of the plurality of cardiac event intervals, wherein the first portion of the plurality of cardiac event intervals occurred more recently in time than the second portion of the plurality of cardiac event intervals; and

detecting initiation of rate onset when the computed variability is less than a variability threshold value and the computed relative change is greater than a relative change threshold value.

16. The method of claim 15, wherein obtaining the EGM associated with the cardiac event comprises obtaining an EGM associated with an oldest cardiac event used in determining the first portion of the cardiac event intervals.

17. The method of claim 15, further comprising monitoring for rate offset after detecting the initiation of the rate onset.

18. The method of claim 15, wherein the plurality of cardiac event intervals are R-R intervals corresponding to amount of time between successive R-waves.

19. The method of claim 12, wherein analyzing the morphology of the EGM comprises computing one or more morphology parameters of the EGM associated with the cardiac event after the location of the initiation of the rate onset;

and

determining whether the rhythm is indicative of a treatable rhythm comprises;

determining the rhythm is indicative of a treatable rhythm when the one or more morphology parameters have changed by threshold amounts compared to respective morphology parameters of a template EGM, and

determining the rhythm is indicative of a non-treatable rhythm when the one or more morphology parameters have not changed by threshold amounts compared to respective morphology parameters of the template EGM.

20. The method of claim 19, wherein:

determining that the rhythm is treatable comprises determining that the rhythm is indicative of one of a ventricular tachycardia (VT) or a ventricular fibrillation (VF); and

determining that the rhythm is non-treatable comprises determining that the rhythm is indicative of a supra-ventricular tachycardia (SVT).

21. The method of claim 19, wherein the template EGM comprises one of an EGM of a cardiac event during normal sinus rhythm, an EGM of a cardiac event just prior to the initiation of the rate onset, or an EGM of another cardiac event after the initiation of the rate onset.

22. The method claim 19, wherein the one or more morphology parameters associated with the EGM include one or more of a matching metric, an R-wave symmetry index (RSI), a R-wave width (RW), a Q-R index (QRI), a R-wave polarity code (RPC) and a slope peak shift (SPS).

23. A computer-readable storage medium comprising instructions that, when executed by a processor in an implantable medical device, cause the processor to:

detect initiation of rate onset of a rhythm of a heart of a patient;

obtain an electrogram (EGM) associated with a cardiac event after a location of the initiation of the rate onset;

analyze a morphology of the EGM associated with the cardiac event after the location of the initiation of the rate onset; and

determine whether the rhythm is indicative of a treatable rhythm based on the analysis of the morphology of the EGM.

24. The computer-readable storage medium of claim 23, wherein instructions to obtain the EGM associated with the cardiac event comprises instructions to obtain an EGM associated with a first cardiac event after the location of the initiation of the rate onset.

25. The computer-readable storage medium of claim 23, wherein instructions to detect the initiation of the rate onset of the rhythm comprise instructions that, when executed, cause the processor to:

determine a plurality of cardiac event intervals;

determine a variability among a first portion of the plurality of cardiac event intervals;

determine a relative change of the first portion of the plurality of cardiac event intervals with respect to a second portion of the plurality of cardiac event intervals, wherein the first portion of the plurality of cardiac event intervals occurred more recently in time than the second portion of the plurality of cardiac event intervals; and

detect initiation of rate onset when the computed variability is less than a variability threshold value and the computed relative change is greater than a relative change threshold value.

26. The computer-readable storage medium of claim 25, wherein instructions to obtain the EGM associated with the cardiac event comprise instructions to obtain an EGM associated with an oldest cardiac event used in determining the first portion of the cardiac event intervals.

27. The computer-readable storage medium of claim 23, wherein

instructions analyze the morphology of the EGM comprise instructions to compute one or more morphology parameters of the EGM associated with the cardiac event after the location of the initiation of the rate onset;

and

instructions to determine whether the rhythm is indicative of a treatable rhythm comprise instructions to;

determine the rhythm is indicative of a treatable rhythm when the one or more morphology parameters have changed by threshold amounts compared to respective morphology parameters of a template EGM, and

determine the rhythm is indicative of a non-treatable rhythm when the one or more morphology parameters have not changed by threshold amounts compared to respective morphology parameters of the template EGM.