Signal compression based on curvature parameters

• US 7,500,955 B2
• Filed: 06/27/2003
• Issued: 03/10/2009
• Est. Priority Date: 06/27/2003
• Status: Expired due to Fees

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Sweeney, Robert J.
• Primary Examiner(s): EVANISKO, GEORGE ROBERT
• Application Number:
  US10/607,820
• Publication Number:
  US 20040267143A1
• Time in Patent Office: 2,083 Days
• Field of Search: 600508-528, 607 1- 76
• US Class Current: 600/508
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/7232 involving compression of the physiological signal, e.g. to extend the signal recording period
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61N 1/371 Capture, i.e. successful stimulation
• CPC Class Codes: G06F 2218/08 Feature extraction
• CPC Class Codes: G16H 20/40 relating to mechanical, radiation or invasive therapies, e.g. surgery, laser therapy, dialysis or acupuncture
• CPC Class Codes: G16H 40/20 for the management or administration of healthcare resources or facilities, e.g. managing hospital staff or surgery rooms
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems
• CPC Class Codes: H03M 7/30 Compression speech analysis-synthesis for redundancy reduction G10L19/00; for image communication H04N; Expansion; Suppression of unnecessary data, e.g. redundancy reduction

Abstract

For a sampled signal, storing characteristic points generated based on parameters corresponding to curvature of the signal. The characteristic points include a time of occurrence of a lobe in a curvature series based on the signal and a corresponding amplitude of the signal. The characteristic points provide a compressed version of the sampled signal. The signal is reconstructed by establishing a function between a chronological sequence of characteristic points. For a repetitive signal, the stored data includes a code to indicate a time of reoccurrence of a previous cycle or data corresponding to differences between a previous cycle and a current cycle.

Claims

1. A method comprising:

receiving a sample series corresponding to a signal sampled at a predetermined rate, the signal sensed using a medical device system;

for each sample in the sample series, calculating a curvature to form a curvature series using a processor, the curvature series corresponding to a curvature signal;

identifying a lobe in the curvature series, the lobe corresponding to a portion of the curvature signal starting when the curvature signal crosses a first threshold in one direction and ending when the curvature signal crosses a second threshold in an opposite direction;

calculating an area of the lobe between the portion of the curvature signal corresponding to the lobe and a baseline; and

if the area is greater than a predetermined value, identifying a parameter for the lobe and storing a characteristic point in a memory of the medical device system, the characteristic point including a time of the parameter and an amplitude corresponding to the time of the parameter.

2. The method of claim 1 wherein identifying the parameter includes identifying a centroid.

3. The method of claim 1 wherein receiving a sample series corresponding to the signal sampled at the predetermined rate includes receiving a sample series generated as a function of an electrocardiogram sampled at a predetermined rate.

4. The method of claim 1 wherein the signal is a function of a sensor signal.

5. The method of claim 1 wherein the signal is a function of time.

6. The method of claim 1 wherein the signal is a function of temperature.

7. The method of claim 1 wherein the signal is a function of an impedance.

8. The method of claim 1 further including receiving the predetermined value.

9. The method of claim 1 further including calculating the predetermined value as a function of changes in the sampled signal.

10. The method of claim 1 wherein identifying the lobe includes identifying a first time when an absolute value of the amplitude of the curvature series is greater than the first threshold and identifying a second time when the absolute value of the amplitude of the curvature series is less than the second threshold.

11. The method of claim 10 wherein the second threshold is less than the first threshold.

12. The method of claim 1 further including, if the area is greater than the predetermined value, storing a code as a function of the predetermined rate.

13. The method of claim 1 wherein storing the characteristic point is performed in real time relative to receiving the sample series.

14. The method of claim 1 wherein receiving the sample series includes accessing stored sample data.

15. The method of claim 1 further including storing a repetition marker to indicate that a later plurality of characteristic points substantially matches an earlier plurality of characteristic points.

16. The method of claim 15 wherein storing the repetition marker includes storing identification data that identifies the earlier plurality of characteristic points.

17. The method of claim 15 wherein storing the repetition marker includes storing temporal data that identifies a time of occurrence of the later plurality of characteristic points.

18. The method of claim 15 wherein storing the repetition marker includes storing a code to indicate a number of consecutive repetitions of the earlier plurality of characteristic points and a time interval between consecutive repetitions.

19. The method of claim 1 further including storing a difference marker to indicate that a later plurality of characteristic points differs from an earlier plurality of characteristic points.

20. The method of claim 19 wherein storing the difference marker includes storing identification data that identifies the earlier plurality of characteristic points.

21. The method of claim 19 wherein storing the difference marker includes storing temporal data that identifies a time of occurrence of the later plurality of characteristic points.

22. The method of claim 19 wherein storing the difference marker includes storing difference data generated as a function of a comparison of the earlier plurality of characteristic points and the later plurality of characteristic points.

23. The method of claim 1 further including, for each characteristic point, storing a start time value determined as a function of a start time for the lobe in the curvature series.

24. The method of claim 1 further including, for each characteristic point, storing an end time value determined as a function of an end time for the lobe in the curvature series.

25. The method of claim 1 further including reconstructing the sampled series by connecting adjacent characteristic points with line segments.

26. The method of claim 1 further including reconstructing the sampled series by connecting adjacent characteristic points with a polynomial equation.

27. The method of claim 1 further including reconstructing the sampled series by connecting adjacent characteristic points with a cubic spline equation.

28. The method of claim 1 further including reconstructing the sampled series as a function of the area of each lobe in the curvature series.

29. The method of claim 1 further including reconstructing the sampled series as a function of a start time of each lobe in the curvature series.

30. The method of claim 1 further including reconstructing the sampled series as a function of an end time of each lobe in the curvature series.

31. The method of claim 1 wherein the sampled signal includes an electrocardiogram and further including:

identifying a plurality of characteristic points; and

delivering therapy as a function of the plurality of characteristic points.

32. The method of claim 1 wherein identifying the parameter for the lobe includes determining a size of the characteristic point as a function of the area of the lobe.

33. The method of claim 1, comprising:

sensing the signal using an implantable medical device, the signal including an intracardiac electrogram; and

storing the characteristic point in a memory of the implantable medical device.