PERIODIC BEAT DETECTION TO DETECT ARTIFACTS IN A CARDIAC ELECTROGRAM

• US 20100030093A1
• Filed: 07/31/2008
• Published: 02/04/2010
• Est. Priority Date: 07/31/2008
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Ghanem, Raja N., Stadler, Robert W., Zhang, Xusheng
• Granted Patent: US 8,050,751 B2
• Time in Patent Office: Days
• US Class Current: 600/518
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• 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 1/3925 Monitoring; Protecting
• CPC Class Codes: A61N 1/39622 Pacing therapy

Abstract

Techniques for determining whether artifacts are present in a cardiac electrogram are described. According to one example, a medical device senses a cardiac electrogram via electrodes. The medical device determines a derivative, e.g., a second order derivative, the electrogram. The medical device detects beats within the derivative, e.g., by comparing a rectified version of the derivative to one or more thresholds determined based on a maximum of the rectified derivative. The medical device determines whether the beats are periodic, and determines whether artifacts are present in the cardiac electrogram based on the determination of whether the beats are periodic. The medical device may further determine whether tachyarrhythmia is present and/or whether the cardiac rhythm of the patient is treatable based on the determination of whether the beats are periodic. For example, the medical device may determine that an electrogram is not treatable when the beats are periodic.

Claims

1. A method comprising:

determining a derivative of a cardiac electrogram of a patient;

detecting beats within the derivative;

determining whether the beats are periodic; and

determining whether artifacts are present in the cardiac electrogram based on the determination of whether the beats are periodic.

2. The method of claim 1, wherein determining whether artifacts are present comprises determining whether a tachyarrhythmia is present in the patient based on the determination of whether the beats are periodic.

3. The method of claim 2, wherein the cardiac electrogram was previously classified as treatable, and determining whether a tachyarrhythmia is present comprises classifying the cardiac electrogram as nontreatable when the beats are periodic.

4. The method of claim 1, wherein determining a derivative comprises determining a second order derivative.

5. The method of claim 1, wherein detecting beats comprises:

comparing the derivative to a first threshold to detect small beats; and

comparing the derivative to a second threshold to detect large beats,

wherein the first threshold is smaller than the second threshold.

6. The method of claim 5, further comprising:

rectifying the derivative;

identifying a maximum of the derivative; and

determining the first threshold and the second threshold based on the maximum,

wherein comparing the derivative to the first and second thresholds comprises comparing the rectified derivative to the first and second thresholds.

7. The method of claim 5, wherein determining whether the beats are periodic comprises:

determining whether the large beats are periodic;

determining whether the small beats are periodic if the large beats are not periodic; and

determining that the beats are periodic if either the large or small beats are periodic.

8. The method of claim 1, wherein determining whether the beats are periodic comprises determining beat to beat intervals between successive beats.

9. The method of claim 8, wherein determining whether the beats are periodic comprises:

comparing the beat to beat intervals to a minimum beat to beat interval threshold; and

determining that beats are not periodic if any of the beat to beat intervals is less than the threshold.

10. The method of claim 8, wherein determining whether the beats are periodic comprises:

determining differences between successive beat to beat intervals;

determining means of successive beat to beat intervals;

comparing the differences to the means; and

determining whether the beats are periodic based on the comparison.

11. The method of claim 8, wherein the cardiac electrogram comprises a sample of a predetermined length of time, the method further comprising:

determining a time before a first one of the beats;

determining a time after a last one of the beats;

determining a mean of the beat to beat intervals;

comparing the time before a first one of the beats and the time after a last one of the beats to the mean; and

determining whether the beats are periodic based on the comparisons.

12. The method of claim 1, wherein determining whether the beats are periodic comprises:

determining a number of the beats;

comparing the number to a threshold; and

determining whether the beats are periodic based on the comparison.

13. The method of claim 1, further comprising determining whether to analyze a cardiac rhythm using the electrogram based on the determination of whether artifacts are present.

14. The method of claim 1, further comprising determining whether to store the electrogram within a memory based on the determination of whether artifacts are present.

15. A system comprising:

a plurality of electrodes;

a medical device coupled to the electrodes that senses a cardiac electrogram via the electrodes; and

a processor that;

determines a derivative of a cardiac electrogram of a patient,

detects beats within the derivative,

determines whether the beats are periodic, and

determines whether artifacts are present in the cardiac electrogram based on the determination of whether the beats are periodic.

16. The system of claim 15, wherein the processor determines whether a tachyarrhythmia is present in the patient based on the determination of whether the beats are periodic.

17. The system of claim 16, wherein the cardiac electrogram was previously classified as treatable, and the processor classifies the cardiac electrogram as nontreatable when the beats are periodic.

18. The system of claim 15, the derivative comprises a second order derivative.

19. The system of claim 15,

wherein the processor compares the derivative to a first threshold to detect small beats, and compares the derivative to a second threshold to detect large beats, and

wherein the first threshold is smaller than the second threshold.

20. The system of claim 19, wherein the processor:

rectifies the derivative,

identifies a maximum of the derivative,

determines the first threshold and the second threshold based on the maximum, and

compares the rectified derivative to the first and second thresholds.

21. The system of claim 19, wherein the processor:

determines whether the large beats are periodic,

determines whether the small beats are periodic if the large beats are not periodic, and

determines that the beats are periodic if either the large or small beats are periodic.

22. The system of claim 15, wherein the processor determines beat to beat intervals between successive beats and determines whether the beats are periodic based on the beat to beat intervals.

23. The system of claim 22, wherein the processor compares the beat to beat intervals to a minimum beat to beat interval threshold, and determines that beats are not periodic if any of the beat to beat intervals is less than the threshold.

24. The system of claim 22, wherein the processor:

determines differences between successive beat to beat intervals,

determines means of successive beat to beat intervals,

compares the differences to the means, and

determines whether the beats are periodic based on the comparison.

25. The system of claim 22, wherein the cardiac electrogram comprises a sample of a predetermined length of time, and the processor:

determines a time before a first one of the beats,

determines a time after a last one of the beats,

determines a mean of the beat to beat intervals,

compares the time before a first one of the beats and the time after a last one of the beats to the mean, and

determines whether the beats are periodic based on the comparisons.

26. The system of claim 15, wherein the processor:

determines a number of the beats,

compares the number to a threshold, and

determines whether the beats are periodic based on the comparison.

27. The system of claim 15, wherein the processor comprises a processor of the medical device.

28. The system of claim 15, wherein the electrodes comprise implantable electrodes and the medical device comprises an implantable medical device.

29. The system of claim 28, wherein the implantable medical device comprises a subcutaneously implantable medical device comprising a housing, and the electrodes comprise electrodes on or integral with the housing.

30. The system of claim 15, wherein the processor determines whether to analyze a cardiac rhythm using the electrogram based on the determination of whether artifacts are present.

31. The system of claim 15, further comprising a memory, wherein the processor determines whether to store the electrogram within the memory based on the determination of whether artifacts are present.

32. A system comprising:

means for determining a derivative of a cardiac electrogram of a patient;

means for detecting beats within the derivative;

means for determining whether the beats are periodic; and

means for determining whether artifacts are present in the cardiac electrogram based on the determination of whether the beats are periodic.

33. A computer-readable medium comprising instructions that cause a programmable processor to:

determine a derivative of a cardiac electrogram of a patient;

detect beats within the derivative;

determine whether the beats are periodic; and

determine whether artifacts are present in the cardiac electrogram based on the determination of whether the beats are periodic.