System and method for tracking ST shift data utilizing histograms

• US 7,725,171 B1
• Filed: 08/31/2007
• Issued: 05/25/2010
• Est. Priority Date: 08/31/2007
• Status: Active Grant

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Inventors: Hoberman, Katie, Jalali, Laleh, Zhu, Bing, Snell, Jay, Bacon, Elizabeth
• Primary Examiner(s): Layno; Carl H
• Assistant Examiner(s): Kimball; Jeremiah T
• Application Number:
  US11/848,606
• Time in Patent Office: 998 Days
• Field of Search: 600/509
• US Class Current: 600/509
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61N 1/365 controlled by a physiological parameter, e.g. heart potential evoked response A61N1/371

Abstract

A method and system are provided for tracking ST shift data. The system includes an implantable medical device having an input configured to receive cardiac signals. Each cardiac signal has an associated heart rate and includes a segment of interest. The implantable medical device further includes a processor configured to determine segment variations of the segment of interest in the cardiac signals. The processor determines a heart rate associated with each of the segment variations with each heart rate falling within a corresponding heart rate range. The implantable medical device also includes a memory configured to store a group of histograms for a corresponding group of heart rate ranges. The histograms store distributions for the segment variations within corresponding heart rate ranges.

Claims

1. An implantable medical device, comprising:

an input configured to receive cardiac signals, each cardiac signal having an associated heart rate and including a segment of interest;

a processor configured to determine segment variations of the segment of interest in the cardiac signals, the processor determining a heart rate associated with each of the segment variations, each heart rate falling within a corresponding heart rate range; and

a memory configured to store a group of histograms for a corresponding group of heart rate ranges, the histograms storing distributions for the segment variations within corresponding heart rate ranges, wherein at least one of the histograms includes a series of bins corresponding to different segment variations, the bins being automatically normalized by the processor when a count in at least one of the bins reaches a predetermined threshold.

2. The device of claim 1, wherein the segment of interest represents an ST segment.

3. The device of claim 1, wherein the processor is configured to identify at least one of a segment shift and a segment deviation as the segment variation.

4. The device of claim 1, wherein the processor is configured to identify the segment variation with respect to a reference level, the reference level presenting one of i) a baseline value for the segment of interest and ii) a value for a reference segment with the cardiac signal.

5. The device of claim 1, wherein first and second groups of histograms store distributions of the segment variations over different first and second periods of time.

6. The device of claim 1, wherein the processor maintains running average distributions for the segment variations input to each of the histograms and auto-normalizes the histograms based on the running average distributions.

7. The device of claim 1, further comprising at least one total input counter associated with the histograms, the total input counter maintaining a count of a total number of segment variations stored in a corresponding histogram.

8. The device of claim 1, further comprising at least one total input counter associated with the histograms, the total input counter maintaining a count of a total number of segment variations stored in a corresponding histogram, the processor utilizing the count in the total input counter to determine relative values of bins in the histograms.

9. The device of claim 1, further comprising at least one normalization counter associated with the histograms, the normalization counter maintaining a count of a number of times a corresponding histogram is normalized.

10. The device of claim 1, wherein the processor is configured to divide the count within each bin in the series of bins for at least one of the histograms by a normalizing value to reduce counts within each bin in the series of bins and maintain a relative distribution for the histogram.

11. The device of claim 1, wherein each of the bins corresponds to one of a different percentage value range or a magnitude value range.

12. The device of claim 1, wherein the cardiac signals are obtained on one of a heart beat by heat beat basis and a set by set basis.

13. The device of claim 1, wherein a plurality of groups of histograms correspond to distributions of the segment variations over a plurality of time periods and wherein the processor is configured to combine the plurality of groups of histograms into a single histogram.

14. The device of claim 1, wherein the group of histograms includes histograms rotated on a daily basis.

15. A method for maintaining myocardial data in an implantable medical device, comprising:

receiving myocardial data including segments of interest;

associating the segments of interest with heart rate ranges;

generating a group of histograms corresponding to each of the heart rate ranges, the group of histograms including distributions for segment variations for the segments of interest, wherein the histograms each include a series of bins corresponding to different segment variations;

storing the group of histograms in the implantable medical device; and

automatically normalizing the bins in at least one of the histograms when a count in at least one of the bins reaches a predetermined threshold.

16. The method of claim 15, further comprising generating histograms based on a predetermined time period.

17. The method of claim 15, further comprising automatically normalizing bins in at least one of the histograms upon determining that a bin corresponding to a particular segment variation has reached a maximum count.

18. The method of claim 15, wherein the distributions include running averages.

19. The method of claim 15, wherein the histograms comprise ST shift histograms.

20. A non-transitory computer readable medium for use in an implantable medical device having a memory and a programmable controller, the computer readable medium having instructions to direct the programmable controller to:

i) receive myocardial data including segments of interest;

ii) associate the segments of interest with heart rate ranges; and

iii) generate a group of histograms corresponding to each of the heart rate ranges, the group of histograms including distributions for segment variations for the segments of interest, wherein the histograms each include a series of bins corresponding to different segment variations;

iv) automatically normalize the bins in at least one of the histograms when a count in at least one of the bins reaches a predetermined threshold; and

direct the memory to;

i) store the group of histograms in the implantable medical device.