Atrial fibrillation detection

• US 7,596,405 B2
• Filed: 03/07/2005
• Issued: 09/29/2009
• Est. Priority Date: 03/07/2005
• Status: Active Grant

• Current Assignee: Medicomp Incorporated (Medicomp, Inc. /Balda/)
• Original Assignee: United Therapeutics Corporation
• Inventors: Gibson, Lucy, Albrecht, Paul, Kurzweil, Raymond C., Grimshaw, Paul
• Primary Examiner(s): Evanisko; George R
• Assistant Examiner(s): Patton; Amanda
• Application Number:
  US11/074,320
• Publication Number:
  US 20060200036A1
• Time in Patent Office: 1,667 Days
• Field of Search: 600/518, 600/516, 600/515
• US Class Current: 600/518
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/35 by template matching
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• CPC Class Codes: A61B 5/7271 Specific aspects of physiological measurement analysis A61B5/316, A61B5/349 and A61B5/374 take precedence
• CPC Class Codes: A61B 5/7445 Display arrangements, e.g. multiple display units
• CPC Class Codes: A61B 5/746 Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms alarms per se G08B

Abstract

Atrial fibrillation is detected in an electrical signal representative of a beating heart by measuring atrial activity over a time window of three or more beats, measuring beat interval variation over the time window and combining the measures of atrial activity and beat interval variation to produce an indication of an atrial fibrillation condition in the electrical signal.

Claims

1. A method of detecting atrial fibrillation, the method comprising

receiving an electrical signal representative of a beating heart;

measuring atrial activity over a time window of three or more beats;

measuring beat interval variation over the time window;

combining the measures of atrial activity and beat interval variation to produce an indication of an atrial fibrillation condition in the electrical signal; and

producing the indication with a processing system;

wherein measuring atrial activity comprises measuring P waves and measuring beat interval variation comprises determining RR interval variation and combining comprises producing a combined measure C[i] determined by;

2. The method of claim 1, wherein measuring atrial activity comprises detecting P-waves.

3. The method of claim 2, wherein measuring atrial activity further comprises:

computing a measure of the fraction of beat intervals that have one detected P wave.

4. The method of claim 2, wherein measuring atrial activity comprises determining if more than one P wave was present in a beat interval.

5. The method of claim 2, wherein detecting P waves comprises:

provisionally classifying a P wave as conducted or non-conducted.

6. The method of claim 1, wherein measuring atrial activity comprises:

using information from more than one signal channel representative of a beating heart.

7. The method of claim 6, wherein measuring atrial activity comprises:

measuring the atrial activity for a plurality of channels;

determining a quality indicator for the measured channels; and

selecting one of the measures from the channels based at least in part on the determined quality indicators for the measured channels.

8. The method of claim 1, wherein measuring atrial activity comprises:

removing part or all of a ventricular waveform from the received ECG signal.

9. The method of claim 8, wherein measuring atrial activity comprises:

measuring the atrial activity from a portion of the signal from which part or all of the ventricular waveform was removed.

10. The method of claim 1, wherein measuring atrial activity over the time window comprises:

producing two or more atrial activity measures in the time window; and

combining the atrial activity measures into a representative atrial activity measure for the time window.

11. The method of claim 10, wherein combining the individual atrial activity measures uses a filtering function.

12. The method of claim 10, wherein combining the atrial activity measures into a representative atrial activity measure for the time window uses a weighted average.

13. The method of claim 1, wherein at least one of measuring atrial activity and measuring beat interval comprises determining a measure for a subwindow of the time window, the subwindow including at least three beats.

14. The method of claim 1, wherein at least one of measuring atrial activity and measuring beat interval comprises combining measures from subwindows of the time window, each subwindow including at least three beats.

15. The method of claim 1, wherein measuring beat variation activity over the time window comprises:

producing two or more beat variation measures in the time window; and

combining the beat variation measures into a representative beat variation measure for the time window.

16. The method of claim 15, wherein combining the individual beat variation measures uses a filtering function.

17. The method of claim 15, wherein combining the beat variation measures into a representative beat variation measure for the time window uses a weighted average.

18. The method of claim 1, wherein measuring beat interval variation comprises:

excluding beat intervals that meet one or more rejection criteria.

19. The method of claim 18, wherein the rejection criteria comprise determining that:

the beat interval is longer than a maximum duration, or the beat interval is bounded by a beat that is not of an atrial origin, or the beat interval includes a non-conducted P wave.

20. The method of claim 1, wherein combining comprises:

coasting the indication of the atrial fibrillation based on the quality indicator Q[i].

21. A computer program product residing on a computer readable medium for detecting the presence of atrial fibrillation in an electrical signal, the computer program product comprising instructions for causing a computer to:

receive the electrical signal representative of a beating heart;

measure atrial activity over a time window of three or more beats;

measure beat interval variation over the time window;

combine the measures of atrial activity and beat interval variation to produce an indication of an atrial fibrillation condition in the electrical signal; and

produce the indication,

wherein instructions for causing a computer to measure atrial activity comprise instructions for causing a computer to measure P waves and

wherein instructions for causing a computer to measure beat interval variation comprise instructions for determining RR interval variation, and

wherein instructions for causing a computer to combine measures of atrial activity and beat interval variation comprise instructions for causing a computer to produce a combined measure C[i] determined by;

22. The computer program product of claim 21, wherein instructions to measure atrial activity comprise instructions to detect P-waves.

23. The computer program product of claim 22, wherein instructions to detect P-waves further comprise instructions to:

compute a measure of the fraction of beat intervals that have one detected P wave.

24. The computer program product of claim 21, wherein instructions to measure atrial activity comprise instructions to:

use information from more than one signal channel representative of a beating heart.

25. The computer program product of claim 21, wherein instructions to measure atrial activity comprise instructions to:

filter part or all of a ventricular waveform from the received ECG signal.

26. The computer program product of claim 21, wherein instructions to measure atrial activity over the time window comprise instructions to:

produce two or more atrial activity measures in the time window; and

combine the atrial activity measures into a representative atrial activity measure for the time window.

27. The computer program product of claim 21, wherein instructions to measure beat variation activity over the time window comprise instructions to:

produce two or more beat variation measures in the time window; and

combine the beat variation measures into a representative beat variation measure for the time window.

28. The computer program product of claim 21, wherein instructions to measure beat interval variation comprise instructions to:

filter out beat intervals that meet one or more rejection criteria.

29. The computer program product of claim 21, wherein instructions to combine comprise instructions to:

coast the indication of the atrial fibrillation based on the quality indicator Q[i].

30. An apparatus comprising circuitry to process an electrical signal for detecting the presence of atrial fibrillation in the electrical signal, the circuitry for processing an electrical signal comprising circuitry to:

receive the electrical signal representative of a beating heart;

measure atrial activity over a time window of three or more beats;

measure beat interval variation over the time window;

combine the measures of atrial activity and beat interval variation to produce an indication of an atrial fibrillation condition in the electrical signal; and

produce the indication,

wherein measuring atrial activity comprises measuring P waves and measuring beat interval variation comprises determining RR interval variation and wherein combining comprises producing a combined measure C[i] determined by;

31. The apparatus of claim 30, wherein the circuitry comprises:

a digital processor device; and

a computer readable medium storing a computer program product that comprises instructions that causes the processor to process the electrical signal to detect the presence of atrial fibrillation in the electrical signal.

32. The apparatus of claim 31, wherein circuitry to detect P-waves further comprises circuitry to:

compute a measure of the fraction of beat intervals that have one detected P wave.

33. The apparatus of claim 30, wherein circuitry to measure atrial activity comprises circuitry to detect P-waves.

34. The apparatus of claim 30, wherein circuitry to measure atrial activity comprises circuitry to:

use information from more than one signal channel representative of a beating heart.

35. The apparatus of claim 30, wherein circuitry to measure atrial activity comprise circuitry to:

filter part or all of a ventricular waveform from the received ECG signal.

36. The apparatus of claim 30, wherein circuitry to measure atrial activity over the time window comprises circuitry to:

produce two or more atrial activity measures in the time window; and

combine the atrial activity measures into a representative atrial activity measure for the time window.

37. The apparatus of claim 30, wherein circuitry to measure beat variation activity over the time window comprises circuitry to:

produce two or more beat variation measures in the time window; and

combine the beat variation measures into a representative beat variation measure for the time window.

38. The apparatus of claim 30, wherein circuitry to measure beat interval variation comprises circuitry to:

filter out beat intervals that meet one or more rejection criteria.

39. The apparatus of claim 30, wherein circuitry to combine comprises circuitry to:

coast the indication of the atrial fibrillation based on the quality indicator Q[i].