Means and method for the detection of cardiac events

• US 20070249947A1
• Filed: 06/22/2007
• Published: 10/25/2007
• Est. Priority Date: 09/20/2002
• Status: Active Grant

• Current Assignee: Angel Medical Systems, Inc.
• Original Assignee: Angel Medical Systems, Inc.
• Inventors: Johnson, Steven, Harwood, Jonathan, Fischell, Tim, Fischell, David, Fischell, Robert
• Granted Patent: US 7,844,323 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 5/0006 ECG or EEG signals
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• 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 5/7465 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 1/3627 for treating a mechanical deficiency of the heart, e.g. congestive heart failure or cardiomyopathy
• CPC Class Codes: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371

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 identifying an ischemic event in a human patient including:

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

an implanted cardiosaver including;

(a) analog-to-digital converter circuitry for digitizing the electrogram to produce a multiplicity of electrogram segments, each having a time period of least 1 second duration;

(b) memory means designed to store a baseline electrogram segment at a first predetermined time;

(c) memory means designed to store a recently collected electrogram segment at a second time that is later than the first predetermined time;

(d) processor means coupled to said memory means for comparing the ST segment voltage of at least one beat of the recently collected electrogram segment at the second time with the average ST segment voltage of at least two beats of the baseline electrogram segment stored in the memory means at the first predetermined time; and

, (e) means for identifying that the ischemic event has occurred when change in the ST segment voltage of the at least one beat of the recently collected electrogram segment as compared to the average ST segment voltage of the at least two beats of the baseline electrogram segment exceeds a detection threshold, the detection threshold being a preset percentage of the average signal amplitude of the at least two beats of the baseline electrogram segment.

2. The system of claim 1 where the average signal amplitude of the at least two beats of the baseline electrogram segment is the R wave peak voltage minus the average PQ segment voltage averaged over the at least two beats of the baseline electrogram.

3. The system of claim 1 where the average signal amplitude of the at least two beats of the baseline electrogram segment is the average peak-to-peak, R-to-S, signal amplitude of the at least two beats of the baseline electrogram.

4. The system of claim 1 where the average signal amplitude of the at least two beats of the baseline electrogram segment is the difference between the average PQ segment voltage and the peak S wave voltage averaged over the at least two beats of the baseline electrogram segment.

5. The system of claim 1 where the average signal amplitude of the at least two beats of the baseline electrogram segment is the larger of the R wave to PQ segment voltage difference or the PQ segment to S wave voltage difference.