Distinguishing between treatable and non-treatable heart rhythms

• US 8,855,755 B2
• Filed: 04/27/2009
• Issued: 10/07/2014
• Est. Priority Date: 04/27/2009
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Zhang, Xusheng, Stadler, Robert W., Gillberg, Jeffrey M.
• Primary Examiner(s): Koharski, Christopher D
• Assistant Examiner(s): CAREY, MICHAEL JAMES
• Application Number:
  US12/430,301
• Publication Number:
  US 20100274148A1
• Time in Patent Office: 1,989 Days
• Field of Search: 600513-521, 607/14
• US Class Current: 600/516
• 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 a plurality of cardiac events cardiac events of a heart of a patient via at least one sensor; and

a processor configured to compute a plurality of cardiac event intervals, wherein each of the cardiac event intervals corresponds to an amount of time between successive ones of the plurality of cardiac events, detect rate onset of a rhythm of the heart of the patient based at least on one of relative changes and variations over the plurality of cardiac event intervals, identify a location of the initiation of rate onset among the plurality of cardiac events used to compute the plurality of cardiac event intervals used for detection of the rate onset, obtain an electrogram (EGM) of one of the cardiac events of the plurality of cardiac events used to compute the plurality of cardiac event intervals used for detection of the rate onset and located subsequent to the after a location of the initiation of the rate onset, analyze a morphology of the obtained 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 obtained EGM.

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

3. The device of claim 1, wherein the processor is configured to analyze characteristics over the plurality of cardiac event intervals to detect the initiation of the rate onset of the rhythm by:

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 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.

4. The device of claim 3, wherein the processor is configured to obtain an EGM of an oldest cardiac event of the first portion of the cardiac event intervals.

5. The device of claim 3, wherein the processor is configured to monitor for rate offset after detecting the rate onset.

6. The device of claim 3, wherein the plurality of cardiac event intervals are R-R intervals corresponding to amount of time between successive R-waves.

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

compute one or more morphology parameters of the EGM of 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.

8. The device of claim 7, 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).

9. The device of claim 7, 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.

10. The device claim 7, 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).

11. A method comprising:

acquiring, via at least one sensor, signals associated with a plurality of cardiac events of a heart of a patient;

computing, with a processor, a plurality of cardiac event intervals, wherein each of the cardiac event intervals corresponds to an amount of time between successive ones of the plurality of cardiac events;

detecting, with the processor, rate onset of a rhythm of the heart of the patient based at least on one of relative changes and variations over the plurality of cardiac event intervals;

identifying, with the processor, a location of the initiation of rate onset among the plurality of cardiac events used to compute the plurality of cardiac event intervals used for detection of the rate onset;

obtaining, with the processor, an electrogram (EGM) of one of the cardiac events of the plurality of cardiac events used to compute the plurality of cardiac event intervals used for detection of the rate onset and located subsequent to the location of the initiation of the rate onset;

analyzing, with the processor, a morphology of the obtained EGM; and

determining, with the processor, whether the rhythm is indicative of a treatable rhythm based on the analysis of the morphology of the obtained EGM.

12. The method of claim 11, wherein obtaining the EGM of one of the cardiac events comprises obtaining an EGM of a first one of the cardiac events of the plurality of cardiac event located subsequent to the location of the initiation of the rate onset.

13. The method of claim 11, wherein analyzing, with the processor, characteristics over the plurality of cardiac event intervals to detect rate onset of the rhythm comprises:

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 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.

14. The method of claim 13, wherein obtaining the EGM of the one of the plurality of cardiac events comprises obtaining an EGM of an oldest cardiac event used in determining the first portion of the cardiac event intervals.

15. The method of claim 13, further comprising monitoring for rate offset after detecting the rate onset.

16. The method of claim 11, wherein the plurality of cardiac event intervals are R-R intervals corresponding to amount of time between successive R-waves.

17. The method of claim 11, wherein analyzing the morphology of the EGM comprises computing one or more morphology parameters of the EGM of 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.

18. The method of claim 17, 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).

19. The method of claim 17, 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.

20. The method claim 17, 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).

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

acquire signals associated with a plurality of cardiac events of a heart of a patient;

compute a plurality of cardiac event intervals, wherein each of the cardiac event intervals corresponds to an amount of time between successive ones of the plurality of cardiac events;

detect rate onset of a rhythm of the heart of the patient based at least on one of relative changes and variations over the plurality of cardiac event intervals;

identify a location of the initiation of rate onset among the plurality of cardiac events used to compute the plurality of cardiac event intervals used for detection of the rate onset;

obtain an electrogram (EGM) of one of the cardiac events of the plurality of cardiac events used to compute the plurality of cardiac event intervals used for detection of the rate onset and located subsequent to the 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.

22. The computer-readable storage medium of claim 21, wherein instructions to obtain the EGM of one of the cardiac events comprises obtaining an EGM of a first one of the cardiac events of the plurality of cardiac event located subsequent to the location of the initiation of the rate onset.

23. The computer-readable storage medium of claim 21, wherein instructions to analyze characteristics over the plurality of cardiac event intervals to detect the rate onset of the rhythm comprise instructions that, when executed, cause the processor to:

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 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.

24. The computer-readable storage medium of claim 23, wherein instructions to obtain the EGM of the cardiac event comprise instructions to obtain an EGM of an oldest cardiac event used in determining the first portion of the cardiac event intervals.

25. The computer-readable storage medium of claim 21, wherein

instructions analyze the morphology of the EGM comprise instructions to compute one or more morphology parameters of the EGM of 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.