Cardiac rhythm management systems and methods for detecting or validating cardiac beats in the presence of noise

• US 20040030256A1
• Filed: 08/06/2002
• Published: 02/12/2004
• Est. Priority Date: 08/06/2002
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Lin, Yayun
• Granted Patent: US 7,215,993 B2
• Time in Patent Office: Days
• US Class Current: 600/509
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• 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 1/3704 Circuits specially adapted therefor, e.g. for sensitivity control
• CPC Class Codes: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents

Abstract

This document describes systems, devices, and methods for detecting or validating cardiac beats, such as in the presence of myopotential or other noise. In one example, an amplitude peak, which is a candidate for a detected cardiac beat, is used in a weighted average, along with a preceding and subsequent sample. The weighted average is compared to a noise threshold. Based on the result of comparison, the amplitude peak is either deemed an actual cardiac beat, or otherwise is deemed noise. The described systems, devices, and methods improve the accuracy of detecting an actual cardiac beat in the presence of noise, during normal sinus rhythm or during an arrhythmia such as ventricular fibrillation. This, in turn, improves the accuracy with which therapy is delivered or withheld by an implantable cardiac rhythm management device. In one example, such as where the system includes a cardiac signal detector with automatic gain control (AGC) circuitry, the weighted average is normalized.

Claims

1. A system comprising:

a cardiac signal detector, comprising a detector input configured to be coupled to a first electrode associated with a heart, and comprising a detector output providing a sampled cardiac signal; and

a signal processor circuit, coupled to the detector output, the signal processor circuit configured to distinguish, using a peak sample, a preceding sample to the peak sample, and a subsequent sample to the peak sample, a cardiac depolarization from noise.

2. The system of claim 1, in which the signal processor circuit is configured to compute a statistic using the peak sample, the preceding sample, and the subsequent sample, and to distinguish between a cardiac depolarization and noise by comparing the statistic to a predetermined threshold value.

3. The system of claim 2, in which the signal processor circuit is configured to compute a weighted average using the peak sample, the preceding sample, and the subsequent sample, and to distinguish between a cardiac depolarization and noise by comparing the weighted average to a predetermined threshold value.

4. The system of claim 3, in which the signal processor circuit is configured to compute a normalized weighted average using the peak sample, the preceding sample, and the subsequent sample, and to distinguish between a cardiac depolarization and noise by comparing the normalized weighted average to a predetermined threshold value.

5. The system of claim 4, in which the normalized weighted average is computed as NWA=[P(n−

1)+2*P(n)+P(n+1)]/[4*P(n)].

6. The system of claim 5, in which the predetermined threshold value is about 0.62.

7. The system of claim 1, further comprising an electrode.

8. The system of claim 7, further comprising an intracardiac leadwire carrying the electrode.

9. The system of claim 1, further comprising:

an implantable device including the cardiac signal detector and the signal processing circuit; and

a remote user interface, configured to be communicatively coupled to the implantable device.

10. The system of claim 1, in which the signal processor circuit is configured to distinguish a normal sinus rhythm cardiac depolarization from noise.

11. The system of claim 1, in which the signal processor circuit is configured to distinguish an arrhythmic cardiac depolarization from noise.

12. The system of claim 11, in which the signal processor circuit is configured to distinguish a ventricular fibrillation cardiac depolarization from noise.

13. An implantable cardiac rhythm management device comprising:

a cardiac signal detector, comprising a cardiac signal detector input configured to be coupled to a first electrode associated with a heart to receive an intrinsic cardiac signal therefrom, and comprising a cardiac signal detector output providing a sampled cardiac signal; and

a depolarization detector circuit, coupled to the first electrode, the depolarization detector circuit including a level detector circuit configured to detect an intrinsic heart depolarization on the intrinsic cardiac signal; and

a signal processor circuit, coupled to the cardiac signal detector output and the depolarization detector circuit, the signal processor circuit configured to validate the intrinsic heart depolarization detected by the depolarization detector circuit by distinguishing a cardiac depolarization from noise, using a peak sample of the sampled cardiac signal, a preceding sample to the peak sample of the sampled cardiac signal, and a subsequent sample to the peak sample of the sampled cardiac signal, wherein the peak sample of the sampled cardiac signal is associated with a peak of the intrinsic heart depolarization detected by the depolarization detector circuit.

14. The device of claim 13, in which the signal processor circuit is configured to compute a weighted average using the peak sample, the preceding sample, and the subsequent sample, and to distinguish between a cardiac depolarization and noise by comparing the weighted average to a predetermined threshold value.

15. The system of claim 14, in which the weighted average is computed as NWA=[P(n−

1)+2*P(n)+P(n+1)]/[4*P(n)].

16. The system of claim 13, in which the signal processor circuit is configured to distinguish a normal sinus rhythm cardiac depolarization from noise.

17. The system of claim 13, in which the signal processor circuit is configured to distinguish an arrhythmic cardiac depolarization from noise.

18. The system of claim 13, in which the signal processor circuit is configured to distinguish a ventricular fibrillation cardiac depolarization from noise.

19. A method comprising:

sampling a cardiac signal;

detecting a peak sample from the cardiac signal;

detecting a preceding sample to the peak sample from the cardiac signal;

detecting a subsequent sample to the peak sample from the cardiac signal;

distinguishing, using the peak sample, the preceding sample, and the subsequent sample, a cardiac depolarization from noise.

20. The method of claim 19, in which the distinguishing comprises:

computing a statistic using the peak sample, the preceding sample, and the subsequent sample; and

distinguishing between a cardiac depolarization and noise by comparing the statistic to a predetermined threshold value.

21. The method of claim 20, in which the computing comprises:

computing a weighted average using the peak sample, the preceding sample, and the subsequent sample; and

distinguishing between a cardiac depolarization and noise by comparing the weighted average to a predetermined threshold value.

22. The method of claim 21, in which the computing comprises:

computing a normalized weighted average using the peak sample, the preceding sample, and the subsequent sample; and

distinguishing between a cardiac depolarization and noise by comparing the normalized weighted average to a predetermined threshold value.

23. The method of claim 22, in which the computing the normalized weighted average is computed as NWA=[P(n−

1)+2*P(n)+P(n+1)]/[4*P(n)].

24. The method of claim 23, in which the comparing the normalized weighted average to the predetermined threshold value comprises using a predetermined threshold value of about 0.62.

25. The method of claim 19, further comprising programming the predetermined threshold value.

26. The method of claim 19, further comprising detecting the cardiac signal using an electrode.

27. The method of claim 26, further comprising intravascularly disposing the electrode within the heart.

28. The method of claim 19, further comprising communicating an indication of whether a peak sample is a depolarization or noise to a remote location.

29. The method of claim 19, in which the distinguishing a cardiac depolarization from noise comprises distinguishing a normal sinus rhythm cardiac depolarization from noise.

30. The method of claim 19, in which the distinguishing a cardiac depolarization from noise comprises distinguishing an arrhythmic cardiac depolarization from noise.

31. The method of claim 19, in which the distinguishing a cardiac depolarization from noise comprises distinguishing a ventricular fibrillation cardiac depolarization from noise.

32. A method comprising:

detecting an intrinsic cardiac signal;

detecting a depolarization on the intrinsic cardiac signal by comparing a level of the intrinsic cardiac signal to a level threshold value to yield a level-detected depolarization;

sampling the intrinsic cardiac signal to produce a sampled cardiac signal;

detecting a peak sample from the sampled cardiac signal, wherein the peak sample is associated with the level-detected depolarization;

detecting a preceding sample to the peak sample from the sampled cardiac signal;

detecting a subsequent sample to the peak sample from the sampled cardiac signal; and

validating, using the peak sample, the preceding sample, and the subsequent sample, the level-detected depolarization by computing a weighted average using the peak sample, the preceding sample, and the subsequent sample, and comparing the weighted average to a noise threshold.

33. The method of claim 32, in which the computing the weighted average is computed as NWA=[P(n−

1)+2*P(n)+P(n+1)]/[4*P(n)].

34. The method of claim 32, in which the validating comprises validating a normal sinus rhythm cardiac depolarization.

35. The method of claim 32, in which the validating comprises validating an arrhythmic cardiac depolarization from noise.

36. The method of claim 32, in which the validating comprises validating a ventricular fibrillation cardiac depolarization from noise.