Combination of electrogram and intra-cardiac pressure to discriminate between fibrillation and tachycardia

• US 20050288725A1
• Filed: 06/29/2004
• Published: 12/29/2005
• Est. Priority Date: 06/29/2004
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Hettrick, Douglas A., Brown, Mark L., Euler, David E.
• Granted Patent: US 7,233,822 B2
• Time in Patent Office: Days
• US Class Current: 607/17
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/287 Holders for multiple electrodes, e.g. electrode catheters for electrophysiological study [EPS]
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/6882 Anchoring means
• CPC Class Codes: A61B 5/7257 using Fourier 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 1/3622 comprising two or more electrodes co-operating with different heart regions
• CPC Class Codes: A61N 1/36564 controlled by blood pressure
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

A system and method for detecting and classifying cardiac arrhythmias based on cardiac pressure signals or the combination of cardiac electrical and cardiac pressure signals. A cardiac electrogram signal is sensed to derive a cardiac rate from which an arrhythmia detection is made when the cardiac rate meets arrhythmia detection criteria. An intracardiac pressure signal is sensed to derive an indicator of tachycardia based on an analysis of the pressure signal in either the time domain or frequency domain. The detected arrhythmia is classified as tachycardia or fibrillation based on the tachycardia indicator wherein the tachycardia indicator is compared to tachycardia detection criteria and the arrhythmia is classified as tachycardia if tachycardia detection criteria are met and the arrhythmia is classified as fibrillation if the tachycardia detection criteria are not met.

Claims

1. A method for detecting and classifying an arrhythmia, comprising:

sensing a cardiac electrogram signal;

determining a cardiac rate in response to the sensed cardiac electrogram signal;

detecting an arrhythmia in response to the cardiac rate;

sensing an intracardiac pressure signal;

generating a parameter corresponding to a frequency content of the pressure signal;

comparing the parameter to predetermined criteria; and

classifying the arrhythmia in response to the comparing, wherein the arrhythmia is classified as a first arrhythmia in response to the parameter meeting the predetermined criteria and as a second arrhythmia in response to the parameter not meeting the predetermined criteria.

2. The method of claim 1, wherein generating the parameter includes processing the sensed pressure signal using time-domain signal analysis.

3. The method of claim 1, wherein generating the parameter includes processing the sensed pressure signal using frequency-domain signal analysis.

4. The method according to claim 1, wherein the sensed cardiac electrogram signal corresponds to an atrial signal, the determined cardiac rate corresponds to an atrial rate, and the sensed pressure signal corresponds to an atrial pressure signal, and wherein the first arrhythmia corresponds to atrial flutter and the second arrhythmia corresponds to atrial fibrillation.

5. The method according to claim 1, wherein the sensed cardiac electrogram signal corresponds to an atrial signal, the determined cardiac rate corresponds to an atrial rate, and the sensed pressure signal corresponds to a ventricular pressure signal, and wherein the first arrhythmia corresponds to atrial flutter and the second arrhythmia corresponds to atrial fibrillation.

6. The method according to claim 1, wherein the sensed cardiac electrogram signal corresponds to a ventricular signal, the determined cardiac rate corresponds to a ventricular rate, and the sensed pressure signal corresponds to a ventricular pressure signal, and wherein the first arrhythmia corresponds to ventricular tachycardia and the second arrhythmia corresponds to ventricular fibrillation.

7. The method according to claim 1, wherein generating the parameter further comprises:

filtering the sensed pressure signal to remove high frequency pressure signals;

subtracting the filtered pressure signal from the sensed pressure signal to generate a high frequency pressure signal; and

determining an amplitude-related parameter in response to the high frequency signal.

8. The method according to claim 1, wherein generating the parameter further comprises:

filtering the sensed pressure signal to remove high frequency pressure signals;

subtracting the filtered pressure signal from the sensed pressure signal to generate a high frequency pressure signal;

rectifying the high frequency pressure signal; and

integrating the high frequency pressure signal to determine an integral value.

9. The method according to claim 8, wherein generating the parameter includes comparing the integral value to a tachycardia detection threshold value and classifying the detected arrhythmia as a tachycardia in response to the integral value being greater than the tachycardia detection threshold value and classifying the detected arrhythmia as fibrillation in response to the integral value being less than the tachycardia detection threshold value.

10. The method according to claim 1, wherein generating the parameter further comprises:

computing a summation of sampled pressure signal points;

comparing the summation to a previously determined summation of sampled pressure signal points; and

determining a correlation between the summation and the previously determined summation.

11. The method according to claim 10, wherein classifying the arrhythmia includes classifying the arrhythmia as tachycardia in response to the correlation being substantially less than 1 and classifying the arrhythmia as fibrillation in response to the correlation being substantially equal to 1.

12. The method according to claim 1, wherein generating a parameter further comprises:

performing a Fourier transform on the sensed pressure signal;

determining the fundamental frequency of the Fourier transform; and

determining if a peak exists at a non-harmonic frequency of the fundamental frequency.

13. The method according to claim 12, wherein classifying the arrhythmia includes classifying the arrhythmia as tachycardia in response to a peak occurring at a non-harmonic frequency of the fundamental frequency, and classifying the arrhythmia as fibrillation in response to a peak not occurring at a non-harmonic frequency of the fundamental frequency.

14. The method according to claim 1, wherein generating a parameter further comprises:

performing a Fourier transform on the sensed pressure signal;

defining a threshold frequency separating the low frequency components from the high frequency components of the Fourier transform;

determining a low frequency peak magnitude as the magnitude of a low frequency peak occurring below the threshold frequency;

determining a high frequency peak magnitude as the magnitude of a high frequency peak occurring above the threshold frequency; and

computing a relation between the low frequency peak magnitude and the high frequency peak magnitude.

15. The method according to claim 1, further comprising selecting a therapy in response to the arrhythmia classification.

16. The method according to claim 15, wherein selecting a therapy further comprises:

selecting an anti-tachycardia therapy in response to an atrial rate falling within an atrial detection threshold and the arrhythmia being classified as the first arrhythmia;

selecting a defibrillation therapy in response to the atrial rate falling within a fibrillation detection threshold and the arrhythmia being classified as the second arrhythmia;

selecting a first user-defined therapy in response to the atrial rate falling within the atrial detection threshold and the arrhythmia being classified as the second arrhythmia; and

selecting a second user-defined anti-arrhythmia therapy in response to the atrial rate falling within the fibrillation detection threshold and the arrhythmia being classified as the first arrhythmia.

17. A medical device, comprising:

means for sensing a cardiac electrogram signal;

means for determining a cardiac rate in response to the sensed cardiac electrogram signal;

means for detecting an arrhythmia in response to the cardiac rate;

means for sensing an intracardiac pressure signal;

means for generating a parameter corresponding to a frequency content of the pressure signal;

means for comparing the parameter to predetermined criteria; and

means for classifying the arrhythmia in response to the comparing, wherein the arrhythmia is classified as a first arrhythmia in response to the parameter meeting the predetermined criteria and as a second arrhythmia in response to the parameter not meeting the predetermined criteria.

18. The device of claim 17, wherein means for generating the parameter includes means for processing the sensed pressure signal using time-domain signal analysis.

19. The device of claim 17, wherein means for generating the parameter includes means for processing the sensed pressure signal using frequency-domain signal analysis.

20. The device according to claim 17, wherein the sensed cardiac electrogram signal corresponds to an atrial signal, the determined cardiac rate corresponds to an atrial rate, and the sensed pressure signal corresponds to an atrial pressure signal, and wherein the first arrhythmia corresponds to atrial flutter and the second arrhythmia corresponds to atrial fibrillation.

21. The device according to claim 17, wherein the sensed cardiac electrogram signal corresponds to an atrial signal, the determined cardiac rate corresponds to an atrial rate, and the sensed pressure signal corresponds to a ventricular pressure signal, and wherein the first arrhythmia corresponds to atrial flutter and the second arrhythmia corresponds to atrial fibrillation.

22. The device according to claim 17, wherein the sensed cardiac electrogram signal corresponds to a ventricular signal, the determined cardiac rate corresponds to a ventricular rate, and the sensed pressure signal corresponds to a ventricular pressure signal, and wherein the first arrhythmia corresponds to ventricular tachycardia and the second arrhythmia corresponds to ventricular fibrillation.

23. The device according to claim 17, wherein means for generating the parameter further comprises:

means for filtering the sensed pressure signal to remove high frequency pressure signals;

means for subtracting the filtered pressure signal from the sensed pressure signal to generate a high frequency pressure signal; and

means for determining an amplitude-related parameter in response to the high frequency signal.

24. The device according to claim 17, wherein means for generating the parameter further comprises:

means for filtering the sensed pressure signal to remove high frequency pressure signals;

means for subtracting the filtered pressure signal from the sensed pressure signal to generate a high frequency pressure signal;

means for rectifying the high frequency pressure signal; and

means for integrating the high frequency pressure signal to determine an integral value.

25. The device method according to claim 24, wherein means for generating the parameter includes means for comparing the integral value to a tachycardia detection threshold value and classifying the detected arrhythmia as a tachycardia in response to the integral value being greater than the tachycardia detection threshold value and classifying the detected arrhythmia as fibrillation in response to the integral value being less than the tachycardia detection threshold value.

26. The device according to claim 17, wherein means for generating the parameter further comprises:

means for computing a summation of sampled pressure signal points;

means for comparing the summation to a previously determined summation of sampled pressure signal points; and

means for determining a correlation between the summation and the previously determined summation.

27. The device according to claim 26, wherein means for classifying the arrhythmia includes classifying the arrhythmia as tachycardia in response to the correlation being substantially less than 1 and classifying the arrhythmia as fibrillation in response to the correlation being substantially equal to 1.

28. The device according to claim 17, wherein means for generating a parameter further comprises:

means for performing a Fourier transform on the sensed pressure signal;

means for determining the fundamental frequency of the Fourier transform; and

means for determining if a peak exists at a non-harmonic frequency of the fundamental frequency.

29. The device according to claim 28, wherein means for classifying the arrhythmia includes classifying the arrhythmia as tachycardia in response to a peak occurring at a non-harmonic frequency of the fundamental frequency, and classifying the arrhythmia as fibrillation in response to a peak not occurring at a non-harmonic frequency of the fundamental frequency.

30. The device according to claim 17, wherein means for generating a parameter further comprises:

means for performing a Fourier transform on the sensed pressure signal;

means for defining a threshold frequency separating the low frequency components from the high frequency components of the Fourier transform;

means for determining a low frequency peak magnitude as the magnitude of a low frequency peak occurring below the threshold frequency;

means for determining a high frequency peak magnitude as the magnitude of a high frequency peak occurring above the threshold frequency; and

means for computing a relation between the low frequency peak magnitude and the high frequency peak magnitude.

31. The device according to claim 17, further comprising means for selecting a therapy in response to the arrhythmia classification.

32. The device according to claim 31, wherein means for selecting a therapy further comprises:

means for selecting an anti-tachycardia therapy in response to an atrial rate falling within an atrial detection threshold and the arrhythmia being classified as the first arrhythmia;

means for selecting a defibrillation therapy in response to the atrial rate falling within a fibrillation detection threshold and the arrhythmia being classified as the second arrhythmia;

means for selecting a first user-defined therapy in response to the atrial rate falling within the atrial detection threshold and the arrhythmia being classified as the second arrhythmia; and

means for selecting a second user-defined anti-arrhythmia therapy in response to the atrial rate falling within the fibrillation detection threshold and the arrhythmia being classified as the first arrhythmia.

33. A computer readable medium having computer executable instructions for performing a method comprising:

sensing a cardiac electrogram signal;

determining a cardiac rate in response to the sensed cardiac electrogram signal;

detecting an arrhythmia in response to the cardiac rate;

sensing an intracardiac pressure signal;

generating a parameter corresponding to a frequency content of the pressure signal;

comparing the parameter to predetermined criteria; and

classifying the arrhythmia in response to the comparing, wherein the arrhythmia is classified as a first arrhythmia in response to the parameter meeting the predetermined criteria and as a second arrhythmia in response to the parameter not meeting the predetermined criteria.