Acute ischemia detection based on smoothed temporal thresholding
First Claim
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1. A cardiac monitor comprising:
- (a) a sensor adapted to sense an analog signal from a heart;
(b) a device coupled to the sensor, the device having an analog-to-digital circuit system contained therein for digitizing the analog signal to produce a digitized waveform;
(c) a processor electrically coupled to the analog-to-digital circuit system, said processor configured to;
(i) compute first and second pluralities of ST deviations from the digitized waveform over initial and subsequent time periods respectively, each of the pluralities of ST deviations being characterized by a statistical distribution;
(ii) storing data pertaining to the first and second pluralities of ST deviations in a form that enables characteristics of the statistical distribution to be computed;
(iii) form a first threshold that is based on the statistical distribution associated with the first plurality of ST deviations in said initial time period;
(iv) apply a test to detect a cardiac event, wherein the test is based on the first threshold formed in said initial time interval;
(v) form a second threshold that is based on the statistical distribution associated with the second plurality of ST deviations in a second time interval subsequent to said first time interval, wherein the second threshold in said second time interval is constrained by the value of the first threshold in said initial time interval;
(vi) apply a test to detect a cardiac event, wherein the test is based on the second threshold of said second time interval.
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Abstract
A heart monitor is disclosed. The monitor computes ST segment deviations and stores the results in heart rate based histograms. Periodically, the monitor analyzes the histogram data to determine a normal range of ST deviation for a particular heart rate range. The monitor computes heart rate dependent ischemia detection thresholds based on the upper and lower boundaries of the normal range. A current threshold for a heart rate range is set as a weighted average of the prior threshold and a provisional threshold based on recent data, thereby limiting the amount the actual detection threshold changes from period to period.
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9 Claims
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1. A cardiac monitor comprising:
- (a) a sensor adapted to sense an analog signal from a heart;
(b) a device coupled to the sensor, the device having an analog-to-digital circuit system contained therein for digitizing the analog signal to produce a digitized waveform;
(c) a processor electrically coupled to the analog-to-digital circuit system, said processor configured to;
(i) compute first and second pluralities of ST deviations from the digitized waveform over initial and subsequent time periods respectively, each of the pluralities of ST deviations being characterized by a statistical distribution;
(ii) storing data pertaining to the first and second pluralities of ST deviations in a form that enables characteristics of the statistical distribution to be computed;
(iii) form a first threshold that is based on the statistical distribution associated with the first plurality of ST deviations in said initial time period;
(iv) apply a test to detect a cardiac event, wherein the test is based on the first threshold formed in said initial time interval;
(v) form a second threshold that is based on the statistical distribution associated with the second plurality of ST deviations in a second time interval subsequent to said first time interval, wherein the second threshold in said second time interval is constrained by the value of the first threshold in said initial time interval;
(vi) apply a test to detect a cardiac event, wherein the test is based on the second threshold of said second time interval. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
- (a) a sensor adapted to sense an analog signal from a heart;
Specification