Means and method for the detection of cardiac events

• US 8,965,494 B2
• Filed: 10/16/2013
• Issued: 02/24/2015
• Est. Priority Date: 05/26/2004
• Status: Active Grant

• Current Assignee: Angel Medical Systems, Inc.
• Original Assignee: Angel Medical Systems, Inc.
• Inventors: Fischell, David R., Fischell, Tim A., Harwood, Jonathan, Fischell, Robert E., Johnson, Steven R.
• Primary Examiner(s): GETZOW, SCOTT M
• Application Number:
  US14/054,982
• Publication Number:
  US 20140107454A1
• Time in Patent Office: 496 Days
• Field of Search: 607/9, 607 25- 27, 600508-521
• US Class Current: 600/517
• CPC Class Codes: A61B 5/0006 ECG or EEG signals
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/02455 provided with high/low alarm devices
• CPC Class Codes: A61B 5/283 Invasive
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/333 Recording apparatus specially adapted therefor
• 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 5/361 Detecting fibrillation
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/366 Detecting abnormal QRS complex, e.g. widening
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 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
• CPC Class Codes: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371
• CPC Class Codes: A61N 1/37258 Alerting the patient
• CPC Class Codes: A61N 1/3756 Casings with electrodes thereon, e.g. leadless stimulators
• CPC Class Codes: G16H 40/67 for remote operation

Abstract

Disclosed is a system for the detection of cardiac events 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 different 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 system includes an internal alarm sub-system (internal alarm means) within the cardiosaver and/or an external alarm system (external alarm means) which are activated after the ST segment of the electrogram exceeds a preset threshold.

Claims

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

at least two implanted electrodes for sensing a plurality of electrical signals from the patient'"'"'s heart during a plurality of time intervals;

an implanted device designed to store the electrical signals from the patient'"'"'s heart;

a determination mechanism for determining a plurality of ST segment values associated with a plurality of beats from the electrical signals;

a memory for storing the plurality of ST segment values;

a processor configured to generate a measure of statistical dispersion of the patient'"'"'s ST segment from a subset of the plurality of ST segment values, the processor further configured to calculate a detection threshold based on the measure of statistical dispersion;

a comparison mechanism for comparing at least one of the plurality of ST segment values that is not within the subset with the detection threshold, thereby generating comparison results, the results being used to identify excessive ST shifts; and

a detection mechanism for detecting an ischemic event based on the comparison results.

2. The system of claim 1 further including a programmer that includes a first transceiver and wherein the implanted device includes a second transceiver, the determination mechanism, the memory for storing the plurality of ST segment values, the comparison mechanism and the detection mechanism, and wherein the implanted device is configured to transmit information regarding the subset of the plurality of ST segment values to the programmer, and wherein the programmer includes the processor configured to generate the measure of statistical dispersion and to calculate the detection threshold and to transmit the threshold to the implanted device.

3. The system of claim 1 where the detection threshold is calculated for each of at least two different heart rate ranges.

4. The system of claim 1 further including patient alerting means.

5. The system of claim 4 where the patient alerting means includes at least two types of alarm signals.

6. The system of claim 5 where the patient alerting means is provided by the implanted device.

7. The system of claim 6 where the patient alerting means is provided by an external alarm system.

8. The system of claim 1 where the ischemic event is an acute myocardial infarction.

9. The system of claim 8 where the ischemic event is ST elevation acute myocardial infarction.

10. The system of claim 8 where the ischemic event is non-ST elevation acute myocardial infarction.

11. The system of claim 1 where the ischemic event is an ST shift at an elevated heart rate.

12. The system of claim 1 where the ischemic event is ST depression at an elevated heart rate.

13. The system of claim 1 wherein the measure of statistical dispersion is based on a standard deviation of ST segment values.

14. The system of claim 13 wherein the detection thresholds is set at a mean of the ST segment values plus or minus a multiple of the standard deviation of ST segment values.

15. The system of claim 14 wherein the multiple is 3.

16. The system of claim 1 wherein the processor is configured to determine a plurality of ST segment values associated with a corresponding plurality of beats within the electrical signal, and to separately compare each of the plurality of ST segment values with the detection threshold.

17. The system of claim 16 wherein the ischemic event is detected when more than a predetermined percentage of the plurality of ST segment values exceeds the detection threshold.

18. The system of claim 1 wherein the value of the ST segment associated with at least one beat is the value of the ST segment for a single beat.