Acute ischemia detection based on parameter value range estimation

• US 9,375,151 B1
• Filed: 09/25/2015
• Issued: 06/28/2016
• Est. Priority Date: 08/25/2010
• Status: Active Grant

• Current Assignee: Angel Medical Systems, Inc.
• Original Assignee: Angel Medical Systems, Inc.
• Inventors: Hopenfeld, Bruce, Johnson, Steven R.
• Primary Examiner(s): Holmes, Rex R
• Application Number:
  US14/865,141
• Time in Patent Office: 277 Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/0006 ECG or EEG signals
• CPC Class Codes: A61B 5/0022 Monitoring a patient using a global network, e.g. telephone networks, internet
• 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 5/02405 Determining heart rate variability
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: A61B 5/7282 Event detection, e.g. detecting unique waveforms indicative of a medical condition A61B5/4094, A61B5/4818, A61B5/349, A61B5/0823 take precedence
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence
• 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
• CPC Class Codes: A61B 5/7465 Arrangements for interactive communication between patient and care services, e.g. by using a telephone network telemetry of measured physiological signal A61B5/0002

Abstract

A method for detecting acute ischemia is disclosed. The method comprises the steps of determining ST segment deviations and storing the results in heart rate based histograms. The histogram data is periodically analyzed to estimate a true range of ST deviation for a particular heart rate range. A current threshold for a heart rate range is set by estimating the true range of ST deviations within that bin, determining the median value of ST deviations within the range, and basing thresholds on the range and median value. The true range for a particular heart rate bin is estimated by locating ST deviation values between which reside a predetermined percentage of all ST deviation values collected for that bin.

Claims

1. A method for detecting cardiac events by analyzing a digitized waveform signal derived from sensors, the method comprising the steps of:

(i) computing a plurality of ST deviations from the digitized waveform over an initial time period for a plurality of heart beats, each of said ST deviations being an ST deviation for a singular heartbeat;

(ii) storing data pertaining to the plurality of ST deviations;

(iii) determine an upper limit of the plurality of ST deviations by selecting an ST deviation value that exceeds the value of most but not all of the plurality of ST deviations;

(iv) determine a lower limit of the plurality of ST deviations by selecting an ST deviation value that is less than the value of most but not all of the plurality of ST deviations, said upper and lower limits of the ST deviations containing therebetween a reduced set of ST deviations with respect to all ST deviations computed within said initial time interval;

(v) compute a dispersion measure of the reduced set of plurality of ST deviations within said initial time period that is based on both the upper and lower limits;

(vi) apply a test to detect a cardiac event after the initial time period, wherein the test is based on the dispersion measure.

2. The method of claim 1 wherein the dispersion measure is based on the difference between the upper and lower limits.

3. The method of claim 2 further comprising the step of computing an average value of the plurality of ST deviations in between the upper and lower limits.

4. The method of claim 3 wherein the average value is the median value of the plurality of ST deviations in between the upper and lower limits.

5. The method of claim 3 wherein the dispersion measure is based on the difference between the upper limit and the average value.

6. The method of claim 3 wherein the test involves applying an upper threshold that is equal to the average value plus a multiple of the dispersion measure.

7. The method of claim 3 wherein the dispersion measure is based on the difference between the lower limit and the average value.

8. The method of claim 1 further comprising the step of storing the plurality of ST deviation according to heart rate ranges, and wherein the upper and lower limits are computed for one of the plurality of heart rate ranges.