System for the detection of cardiac events

• US 20040059238A1
• Filed: 08/18/2003
• Published: 03/25/2004
• 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., Fischell, Robert E., Johnson, Steven R., Harwood, Jonathan, Fischell, Tim A.
• Granted Patent: US 8,038,624 B2
• Time in Patent Office: Days
• US Class Current: 600/515
• 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

Disclosed is a system for the detection of cardiac events (a guardian system) that includes an implanted device called a cardiosaver, a physician'"'"'s programmer and an external alarm system. The system is designed to provide early detection of cardiac events such as acute myocardial infarction or exercise induced myocardial ischemia caused by an increased heart rate or exertion. The system can also alert the patient with a less urgent alarm if a heart arrhythmia is detected. Using one or more detection algorithms, the cardiosaver can detect a change in the patient'"'"'s electrogram that is indicative of a cardiac event within five minutes after it occurs and then automatically warn the patient that the event is occurring. To provide this warning, the guardian system includes an internal alarm sub-system (internal alarm means) within the cardiosaver and/or an external alarm system (external alarm means). If the guardian system is put into a pacemaker, the algorithm can utilize a different analysis of the electrogram depending on whether or not the pacemaker is actually pacing the heart.

Claims

1. A system for detecting a cardiac event in a human patient the system including:

at least two electrodes for obtaining an electrical signal from the patient'"'"'s heart, the electrical signal being either or both an electrogram and/or an electrocardiogram, the electrical signal consisting of a multiplicity of segments each having a time period of a specific time duration;

a device for detecting a cardiac event, the device including means for processing at least some segments of the electrical signal, the means for processing including the processing of individual beats of the patient'"'"'s heart and also the sequential processing of successive beats to detect at least one abnormality within that beat, the processing being capable of determining if the beat is an abnormal beat or a normal beat; and

means for determining that a cardiac event has occurred when at least M out of N abnormal beats occur during the processing of the electrical signal before the occurrence of M−

N+1 normal beats.

2. The system of claim 1 where the cardiac event is an acute myocardial infarction.

3. The system of claim 1 where the abnormality is a detected ST shift.

4. The system of claim 1 the cardiac event is an arrhythmia.

5. The system of claim 4 where the arrhythmia is selected from the group consisting of tachycardia, bradycardia, unsteady heart rate, bigeminal rhythm, premature ventricular contractions, premature atrial contractions and atrial fibrillation.

6. The system of claim 1 where the cardiac event is exercise induced ischemia.

7. The system of claim 1 where at least one of the electrodes is located within the heart.

8. The system of claim 7 where the electrode located within the heart is located within the right ventricle.

9. The system of claim 7 where the electrode located within the heart is located within the right atrium.

10. The system of claim 1 where at least one of the electrodes is located outside of the heart.

11. The system of claim 1 where at least one electrode is located on the surface of the patient'"'"'s skin.

12. The system of claim 1 where at least one electrode is located subcutaneously.

13. The system of claim 12 where at least one subcutaneously located electrode is located on the patient'"'"'s left side.

14. A system for detecting a cardiac event from the electrogram of a patient'"'"'s heart as measured by implantable electrodes the electrogram including segments consisting of multiple beats and each beat having sub-segments, the system including:

(a) electrical circuitry means for determining the time of occurrence of the R waves of successive beats within the electrogram;

(b) processor means for calculating the time period between successive R waves, that time period being called an R-R interval, the R-R interval for a specific beat within the electrogram being the difference in time of occurrence of the R wave of a first beat to the time of occurrence of the R wave of the preceding beat;

(c) means for determining the signal amplitude of at least one sub-segment of at one beat of the electrogram, the sub-segment having a start time and a time duration;

(d) means for adjusting the start time of the sub-segment responsive to the calculated R-R interval; and

,

(e) processing means for detecting that the cardiac event has occurred by further analysis of the signal amplitude of at least one sub-segment of at least one beat of the electrogram.

15. The system of claim 14 where the cardiac event is an acute myocardial infarction.

16. The system of claim 14 where the cardiac event is exercise induced ischemia.

17. The system of claim 14 where the sub-segment of the electrogram includes at least a portion of the ST segment of the electrogram.

18. The system of claim 14 where the sub-segment of the electrogram includes at least a portion of the PQ segment of the electrogram.

19. The system of claim 14 where the sub-segment of the beat of the electrogram includes the peak of the T wave.

20. The system of claim 14 further including means to exclude any beat where the R-R interval is shorter than a predetermined time period from the processing means for detecting a cardiac event.

21. The system of claim 20 where the predetermined time period is 60 milliseconds.

22. The system of claim 14 where the signal amplitude of the sub-segment is the average signal amplitude of that sub-segment.

23. The system of claim 14 where the start time of the sub-segment is adjusted in proportion to the R-R interval.

24. The system of claim 14 where the start time of the sub-segment is adjusted in proportion to the square root of the R-R interval.

25. The system of claim 14 where the means for adjusting the start time for the sub-segment uses a look-up table with values of start time corresponding to certain values of R-R interval.

26. A cardiac pacemaker with the capability of detecting a heart attack in a human patient the pacemaker including:

electronic demand pacing circuitry designed to pace the heart of the human patient when the R-R interval exceeds a pre-determined time period;

a pacemaker lead placed within the heart of the patient, the lead providing an electrogram signal to the electronic demand pacing circuitry;

electronic circuitry for detecting a shift in a specific sub-segment of the electrogram signal, the electronic circuitry including timing means to identify the start and time duration of a sub-segment for each beat within the patient'"'"'s electrogram signal, the timing means having at least two sets of parameters used to calculate the start time and duration of the sub-segment, a first set of parameters for detecting a shift in the specific sub-segment of the heart beat for heart beats that are not triggered by the electronic demand pacing circuitry, and a second set of parameters to be used for detecting a shift in the specific sub-segment of the heart beat for heart beats that are triggered by the electronic demand pacing.

27. The system of claim 26 where the sub-segment is the ST segment.

28. The system of claim 26 where the sub-segment includes the peak of the T wave.

29. The system of claim 26 where start time of the sub-segment is calculated relative to the time of occurrence of the R wave.

30. The system of claim 26 where start time of the sub-segment is calculated relative to the time of occurrence of the S wave.

31. The system of claim 26 where start time of the sub-segment is calculated relative to the time of occurrence of the S wave on beats where the pacemaker is pacing and relative to the R wave on beats where the pacemaker is not pacing.

32. The system of claim 26 further including alerting means to notify the patient when a heart attack is detected.

33. The system of claim 32 further including means to detect exercise induced ischemia and heart arrhythmias.

34. A system for detecting a cardiac event in a human patient, the system including:

at least two electrodes implanted in the patient for obtaining the electrical signal from the patient'"'"'s heart, the electrical signal being an electrogram;

an implanted cardiosaver including electronic circuitry designed to identify at least one feature of a beat of the electrogram by comparing the slope of the electrogram signal with a first predetermined threshold if the slope of the electrogram signal is positive and a second predetermined threshold if the slope of the electrogram signal is negative.

35. The system of claim 34 where the electronic circuitry includes a microprocessor.