BASELINE PROCESSING FOR THE DETECTION OF CARDIAC EVENTS

• US 20090171228A1
• Filed: 02/06/2009
• Published: 07/02/2009
• Est. Priority Date: 09/20/2002
• Status: Active Grant

• Current Assignee: Angel Medical Systems, Inc.
• Original Assignee: Angel Medical Systems, Inc.
• Inventors: FISCHELL, DAVID R., HARWOOD, JONATHAN, KEENAN, DAVID, JOHNSON, STEVEN R.
• Granted Patent: US 8,170,653 B2
• Time in Patent Office: Days
• US Class Current: 600/517
• CPC Class Codes: A61B 2560/0209 adapted for power saving
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/02455 provided with high/low alarm devices
• CPC Class Codes: A61B 5/287 Holders for multiple electrodes, e.g. electrode catheters for electrophysiological study [EPS]
• 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 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/364 Detecting abnormal ECG interval, e.g. extrasystoles, ectopic heartbeats
• CPC Class Codes: A61B 5/366 Detecting abnormal QRS complex, e.g. widening
• 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 system for the detection of cardiac events occurring in a human patient is provided. At least two electrodes are included in the system for obtaining an electrical signal from a patient'"'"'s heart. An electrical signal processor is electrically coupled to the electrodes for processing the electrical signal and a patient alarm means is further provided and electrically coupled to the electrical signal processor. The electrical signal is acquired in the form of electrogram segments, which are categorized according to heart rate, ST segment shift and type heart rhythm (normal or abnormal). Baseline electrogram segments are tracked over time.

Claims

1. A cardiac event detection system for detecting a cardiac event in a patient comprising:

(a) at least two electrodes for sensing an electrical signal from said patient'"'"'s heart;

(b) an implantable device coupled to said electrodes, said implantable device having an analog-to-digital circuit system contained therein for digitizing said electrical signal to produce segments;

(c) a processor contained in said implantable device and electrically coupled to said electrodes, said processor configured to;

(i) determine whether an electrical signal segment qualifies as a baseline segment;

(ii) compute the value of a heart signal parameter for each of at least two baseline segments, thereby deriving baseline heart signal parameter values, (iii) generate a statistical measure of the heart signal parameter based on the baseline heart signal parameter values;

(iv) compute the value of the heart signal parameter for an additional electrical signal segment;

(v) detect the cardiac event based on a comparison of the statistical measure with the value of the heart signal parameter of the additional electrical signal segment.

2. The system of claim 1 wherein the statistical measure is the average of the baseline heart signal parameter values.

3. The system of claim 1 wherein the heart signal parameter is calculated by the processor from ST segment voltage.

4. The system of claim 3 wherein the heart signal parameter is calculated by the processor by computing a difference between ST segment voltage and PQ segment voltage.

5. The system of claim 3 wherein the heart signal parameter is calculated by the processor by computing an R wave amplitude, and normalizing the heart signal parameter by R wave amplitude.

6. The system of claim 3 wherein the cardiac event is ischemia, and the processor is configured to detect ischemia when the difference between the ST segment voltage of the additional electrical signal segment and the statistical measure exceeds a detection threshold.

7. The system of claim 1 wherein the statistical measure is based on a plurality of baseline heart signal parameter values associated with a corresponding plurality of baseline time slots.

8. The system of claim 7 wherein the processor further includes means for assigning a predetermined heart signal parameter value to a time slot whose baseline has not been updated within a specified period.

9. A cardiac event detection system for detecting a cardiac event in a patient comprising:

(a) at least two electrodes for sensing an electrical signal from said patient'"'"'s heart;

(b) an implantable device coupled to said electrodes, said implantable device having an analog-to-digital circuit system contained therein for digitizing said electrical signal to produce segments;

(c) a processor contained in said implantable device and electrically coupled to said electrodes, said processor configured to;

(i) compute the values of a heart signal parameter for a plurality beats within a plurality of segments, (ii) generate a plurality of representative values of the heart signal parameter, wherein each of the plurality of representative values is based on the plurality of values of the heart signal parameter in a corresponding one of the plurality of segments;

(iii) generate a statistical measure that is based on the plurality of representative values;

and (iv) applying a test to detect a cardiac event, wherein the test is based on the statistical measure.

10. The system of claim 9 wherein each of the plurality of representative values is an average of the plurality of heart signal parameter values within a corresponding segment.

11. The system of claim 9 wherein the statistical measure is an average of the plurality of representative values.

12. The system of claim 9 wherein the processor is configured to acquire an additional segment and to calculate the value of the heart signal parameter of at least one beat in the additional segment, and wherein the test involves a comparison of the value of the heart signal parameter in the additional segment with the statistical measure.

13. The system of claim 9 wherein the cardiac event is ischemia.

14. The system of claim 13 wherein the heart signal parameter pertains to ST segment shift.

15. A cardiac event detection system for detecting a cardiac event in a patient comprising:

(a) at least two electrodes for sensing an electrical signal from said patient'"'"'s heart;

(b) an implantable device coupled to said electrodes, said implantable device having an analog-to-digital circuit system contained therein for digitizing said electrical signal to produce segments;

(c) a programmable memory for storing a default baseline heart signal parameter value;

(d) a processor contained in said implantable device and electrically coupled to said electrodes, said processor configured to;

(i) compute a value of a heart signal parameter for an electrical signal segment;

(ii) select the default baseline heart signal parameter value or an actual baseline heart signal parameter value to compare with the value of the heart signal parameter for the electrical signal segment;

(iii) responsive to the results of the comparison, detect the cardiac event.

16. The system of claim 15 wherein the processor is configured to select the default baseline heart signal parameter value or the actual baseline heart signal parameter value according to an externally programmable flag.

17. The system of claim 15 wherein the processor is configured to adaptively select the default baseline heart signal parameter value or the actual baseline heart signal parameter value based on an analysis of the electrical signal.

18. The system of claim 17 wherein the analysis of the electrical signal involves determining whether electrical signal segments do not qualify as baseline segments.