Long-term monitoring for detection of atrial fibrillation

• US 20060084883A1
• Filed: 10/19/2005
• Published: 04/20/2006
• Est. Priority Date: 10/19/2004
• Status: Active Grant

• Current Assignee: University of Washington
• Original Assignee: University of Washington
• Inventors: Linker, David Thor
• Granted Patent: US 7,630,756 B2
• Time in Patent Office: Days
• US Class Current: 600/518
• CPC Class Codes: A61B 5/02405 Determining heart rate variability
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• CPC Class Codes: A61B 5/7232 involving compression of the physiological signal, e.g. to extend the signal recording period
• CPC Class Codes: A61N 1/3621 for treating or preventing abnormally high heart rate
• CPC Class Codes: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371

Abstract

A method and a system for detection of an arrhythmia, the method comprising determining a number of heart beat intervals; determining an instantaneous heart rate for each of the heart beat intervals; determining the variability of the instantaneous heart rates compared to a mean of the number of instantaneous heart rates; determining a non-linear value that represents the variability of the instantaneous heart rates; and detecting the arrhythmia by comparing the non-linear value with a predetermined threshold.

Claims

1. A method for detection of an arrhythmia, the method comprising:

determining a number of heart beat intervals;

determining an instantaneous heart rate for each of the heart beat intervals;

determining the variability of the instantaneous heart rates compared to a mean of the number of instantaneous heart rates;

determining a non-linear value that represents the variability of the instantaneous heart rates; and

detecting the arrhythmia by comparing the non-linear value with a predetermined threshold.

2. The method of claim 1 wherein the determining a number of heart beat intervals comprises using a predetermined number of segments, each of the segments including a number of heart beat intervals.

3. The method of claim 2 wherein determining the non-linear value comprises:

determining a mean value of the instantaneous heart rates within each segment;

determining a value of a deviation of each instantaneous heart rate from the mean value of each segment;

determining a median value of the value of the deviation of each instantaneous heart rate from the mean value for each of the segments; and

determining a median of the median values of each of the segments.

4. The method of claim 1 wherein the arrhythmia is atrial fibrillation.

5. The method of claim 1 wherein the number of segments is greater than or equal to three.

6. The method of claim 1 wherein the mean value of the instantaneous heart rates for each segment is removed from calculation data after determining the instantaneous heart rates.

7. The method of claim 1 wherein the predetermined threshold is dynamically determined prior to the comparison.

8. The method of claim 1 wherein the number of heart beat intervals in each segment is greater than or equal to seven and less than or equal to nineteen.

9. A method for detection of an arrhythmia, the method comprising:

determining a number of segments, each of the segments including a number of heart beat intervals;

determining arrival time of a QRS complex portion of a signal representing each heart beat;

using the arrival times of the QRS complex portions to determine an instantaneous heart rate for each of the heart beat intervals;

determining the variability of the instantaneous heart rates compared to a mean of the instantaneous heart rates;

determining a non-linear value that represents the variability of the instantaneous heart rates; and

detecting the arrhythmia by comparing the non-linear value with a predetermined threshold.

10. The method of claim 9 wherein the arrhythmia is atrial fibrillation.

11. The method of claim 9 wherein the number of segments is greater than or equal to three.

12. The method of claim 9 wherein the mean value of the heart rates for each segment is removed from calculation data after determining the instantaneous heart rates.

13. The method of claim 9 wherein the predetermined threshold is dynamically determined prior to the comparison.

14. The method of claim 9 wherein determining the non-linear value comprises:

determining a mean value of the instantaneous heart rates within each segment;

determining a value of a deviation of each instantaneous heart rate from the mean value of each segment;

determining a median value of the value of the deviation of each instantaneous heart rate from the mean value for each of the segments; and

determining a median of the median values of each of the segments.

15. The method of claim 9 wherein the arrival time of the QRS complex is determined based on one of a real-time data and a stored data.

16. A method for detection of a QRS complex portion of a signal representing a heart beat, the method comprising:

determining a next signal sample;

determining an amplitude difference between the next signal and an immediate previous signal;

determining an absolute value of the amplitude difference;

determining a total of the absolute values of the amplitude differences over a predetermined time window;

determining whether the total is greater than a predetermined threshold value;

determining a QRS complex time based on the predetermined time window; and

providing the QRS complex time.

17. The method of claim 16 wherein the QRS complex time is determined by subtracting half of a value of the predetermined time window from a time of a maximum signal amplitude value within the predetermined time window.

18. The method of claim 17 wherein the time of the maximum signal amplitude value is determined by detecting whether a time of the next signal is within a maximum QRS time window.

19. The method of claim 18 wherein the time of the next signal is within the QRS complex portion.

20. A portable monitoring device for detecting an arrhythmia, the device comprising:

a portable power source;

at least one electrode for collecting heart rhythm data from a patient;

a monitoring circuit coupled to the power source and the at least one electrode, wherein the monitoring circuit analyzes segments of the collected heart rhythm data to detect an arrhythmia; and

a memory coupled to the monitoring circuit, wherein the memory stores the analyzed segments of collected heart rhythm data if an arrhythmia is detected.

21. The portable monitoring device of claim 20, wherein the power source, monitoring circuit and memory are housed in a body having a volume less than 80 milliliters.

22. The portable monitoring device of claim 20, wherein the body including the power source, monitoring circuit and memory weighs less than or equal to 90 grams.

23. The portable monitoring device of claim 20, wherein the power source comprises a battery.

24. The portable monitoring device of claim 23, wherein the power source comprises an off-the-shelf battery.

25. The portable monitoring device of claim 20 further comprising at least one communication interface.

26. The portable monitoring device of claim 25, wherein the communication interface comprises a wireless communication interface.

27. The portable monitoring device of claim 25, wherein the communication interface comprises a wired communications interface.

28. The portable monitoring device of claim 20 further comprising at least one user input component.

29. The portable monitoring device of claim 20 further comprising a removable memory.

30. The portable monitoring device of claim 20 further comprising a user interface display.

31. The portable monitoring device of claim 20, wherein the at least one electrode, monitoring circuit, and memory are integrated into a portable package.

32. The portable monitoring device of claim 31, wherein the power source is integrated into the portable package.

33. The portable monitoring device of claim 31, wherein the package is disposable.

34. The portable monitoring device of claim 33, wherein the portable package weighs less than or equal to 90 grams.

35. The portable monitoring device of claim 20, wherein the monitoring circuit comprises a microprocessor and a preamplifier.

36. The portable monitoring device of claim 35, wherein the monitoring circuit further comprises a QRS detector.

37. The portable monitoring device of claim 20, wherein the arrhythmia detected is atrial fibrillation.

38. The monitoring system of claim 20 wherein the collected heart rhythm data is compressed.

39. A monitoring system for detecting an arrhythmia in a patient, the system comprising:

a portable monitoring device for analyzing segments of heart rhythm data collected from the patient and storing the analyzed segments of collected heart rhythm data if an arrhythmia is detected; and

a data collection system for collecting the stored analyzed segments of heart rhythm data from the portable monitoring device.

40. The monitoring system of claim 39, wherein the data collection system receives the stored analyzed segments of heart rhythm data from the portable monitoring device via a communication link.

41. The monitoring system of claim 40, wherein the communication link is a wireless communication link.

42. The monitoring system of claim 40, wherein the communication link is a wired communication link.

43. The monitoring system of claim 40, wherein the portable monitoring device transfers the stored analyzed segments of heart rhythm data to a base station and the base station transfers the stored analyzed segments of heart rhythm data to the data collection system via the communication link.

44. The monitoring system of claim 43, wherein the portable monitoring device transfers the stored analyzed segments of heart rhythm data to the base station via a wireless communication link.

45. The monitoring system of claim 44, wherein the portable monitoring device transfers the stored analyzed segments of heart rhythm data to the base station via a wired communication link.

46. The monitoring system of claim 39, wherein the stored analyzed segments of heart rhythm data are uploaded to the data collection system from a memory of the portable monitoring device.