Techniques for determining morphological stability of cardiac cycles

• US 8,594,775 B2
• Filed: 05/10/2011
• Issued: 11/26/2013
• Est. Priority Date: 05/10/2011
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Ghosh, Subham, Gillberg, Jeffrey M.
• Primary Examiner(s): Holmes, Rex R
• Assistant Examiner(s): Hankins, Lindsey G
• Application Number:
  US13/104,794
• Publication Number:
  US 20120289845A1
• Time in Patent Office: 931 Days
• Field of Search: 607/4, 607/5, 607/25, 600/509, 600/510, 600/513, 600515-518
• US Class Current: 600/510
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: A61N 1/3621 for treating or preventing abnormally high heart rate

Abstract

A method includes retrieving electrogram (EGM) data for N cardiac cycles from a memory of an implantable medical device. N is an integer greater than 1. The method further include categorizing each of the N cardiac cycles into one of a plurality of categories based on a morphology of the N cardiac cycles and performing comparisons between pairs of the N cardiac cycles. Each of the comparisons between two cardiac cycles includes detecting a mismatch between the two cardiac cycles when the two cardiac cycles are in different categories, and detecting a match between the two cardiac cycles when the two cardiac cycles are in the same category. Additionally, the method includes classifying the rhythm of the N cardiac cycles based on a number of detected matches and detected mismatches.

Claims

1. A method comprising:

retrieving electrogram (EGM) data for N cardiac cycles from a memory of an implantable medical device, wherein N is an integer greater than 1;

categorizing each of the N cardiac cycles into one of a plurality of categories based on a morphology of the N cardiac cycles;

performing comparisons between pairs of the N cardiac cycles, each of the comparisons between two cardiac cycles including;

detecting a mismatch between the two cardiac cycles when the two cardiac cycles are in different categories; and

detecting a match between the two cardiac cycles when the two cardiac cycles are in the same category; and

classifying the rhythm of the N cardiac cycles based on a number of detected matches and detected mismatches, wherein categorizing each of the N cardiac cycles comprises categorizing a single cardiac cycle of the N cardiac cycles based on at least one of a positive peak value of the single cardiac cycle, a negative peak value of the single cardiac cycle, and an order in which the positive peak value and the negative peak value occur in the single cardiac cycle, and further comprising;

categorizing the single cardiac cycle as a dominantly positive cycle when the positive peak value is greater than the absolute value of the negative peak value by a first threshold amount; and

categorizing the single cardiac cycle as a dominantly negative cycle when the absolute value of the negative peak value is greater than the positive peak value by a second threshold amount.

2. The method of claim 1, wherein the implantable medical device includes at least one of a pacemaker and a cardioverter-defibrillator.

3. The method of claim 1, further comprising categorizing the single cardiac cycle as one of initially positive or initially negative when the positive peak value is not greater than the absolute value of the negative peak value by the first threshold amount and when the absolute value of the negative peak value is not greater than the positive peak value by the second threshold amount.

4. The method of claim 3, wherein categorizing the single cardiac cycle as initially positive comprises determining that the positive peak value occurs before the negative peak value in the single cardiac cycle, and wherein categorizing the single cardiac cycle as initially negative comprises determining that the negative peak value occurs before the positive peak value in the single cardiac cycle.

5. The method of claim 1, wherein performing comparisons between pairs of the N cardiac cycles comprises performing N*(N−

1)/2 comparisons.

6. The method of claim 1, wherein classifying the rhythm comprises:

classifying the rhythm as a monomorphic ventricular tachycardia when the number of detected matches is greater than or equal to a threshold number of matches; and

classifying the rhythm as at least one of a polymorphic ventricular tachycardia or ventricular fibrillation when the number of detected matches is less than the threshold number of matches.

7. The method of claim 1, wherein each of the comparisons between the two cardiac cycles includes detecting a match between the two cardiac cycles when the two cardiac cycles are in the same category and the two cardiac cycles have a second quantifiable morphological similarity.

8. The method of claim 7, wherein the second quantifiable morphological similarity is a peak-to-peak amplitude, and wherein each of the comparisons between the two cardiac cycles includes detecting a match between the two cardiac cycles when the two cardiac cycles are in the same category and when a difference in the peak-to-peak amplitudes of the two cardiac cycles is less than a threshold amplitude.

9. The method of claim 7, wherein the second quantifiable morphological similarity includes slope values of the two cardiac cycles, areas of the two cardiac cycles, and ratios of peak values of the two cardiac cycles.

10. The method of claim 1, wherein N is an integer greater than or equal to 12.

11. A medical device comprising:

a memory; and

a processing module configured to;

retrieve electrogram (EGM) data for N cardiac cycles from the memory, wherein N is an integer greater than 1;

categorize each of the N cardiac cycles into one of a plurality of categories based on a morphology of the N cardiac cycles;

perform comparisons between pairs of the N cardiac cycles, each of the comparisons between two cardiac cycles including;

detecting a mismatch between the two cardiac cycles when the two cardiac cycles are in different categories; and

detecting a match between the two cardiac cycles when the two cardiac cycles are in the same category; and

classify the rhythm of the N cardiac cycles based on a number of detected matches and detected mismatches, wherein the processing module is configured to categorize a single cardiac cycle of the N cardiac cycles based on at least one of a positive peak value of the single cardiac cycle, a negative peak value of the single cardiac cycle, and an order in which the positive peak value and the negative peak value occur in the single cardiac cycle, and wherein the processing module is configured to;

categorize the single cardiac cycle as a dominantly positive cycle when the positive peak value is greater than the absolute value of the negative peak value by a first threshold amount; and

categorize the single cardiac cycle as a dominantly negative cycle when the absolute value of the negative peak value is greater than the positive peak value by a second threshold amount.

12. The medical device of claim 11, further comprising a housing configured to be implanted in a patient, wherein the housing houses the memory and the processing module.

13. The medical device of claim 11, wherein the processing module is configured to categorize the single cardiac cycle as one of initially positive or initially negative when the positive peak value is not greater than the absolute value of the negative peak value by the first threshold amount and when the absolute value of the negative peak value is not greater than the positive peak value by the second threshold amount.

14. The medical device of claim 13, wherein the processing module is configured to categorize the single cardiac cycle as initially positive when the positive peak value occurs before the negative peak value in the single cardiac cycle, and wherein the processing module is configured to categorize the single cardiac cycle as initially negative when the negative peak value occurs before the positive peak value in the single cardiac cycle.

15. The medical device of claim 11, wherein the processing module is configured to:

classify the rhythm as a monomorphic ventricular tachycardia when the number of detected matches is greater than or equal to a threshold number of matches; and

classify the rhythm as one of a polymorphic ventricular tachycardia and ventricular fibrillation when the number of detected matches is less than the threshold number of matches.

16. The medical device of claim 11, wherein each of the comparisons between the two cardiac cycles includes detecting a match between the two cardiac cycles when the two cardiac cycles are in the same category and the two cardiac cycles have a second quantifiable morphological similarity.

17. The medical device of claim 16, wherein the second quantifiable morphological similarity is a peak-to-peak amplitude, and wherein each of the comparisons between the two cardiac cycles includes detecting a match between the two cardiac cycles when the two cardiac cycles are in the same category and when a difference in the peak-to-peak amplitudes of the two cardiac cycles is less than a threshold amplitude.