RR INTERVAL BASED BEAT REJECTION FOR A CARDIAC MONITOR

• US 20110137194A1
• Filed: 02/11/2011
• Published: 06/09/2011
• Est. Priority Date: 09/20/2002
• Status: Active Grant

• Current Assignee: Angel Medical Systems, Inc.
• Original Assignee: Angel Medical Systems, Inc.
• Inventors: Fischell, Tim A., FISCHELL, DAVID R., Fischell, Robert E., Harwood, Jonathan
• Granted Patent: US 9,101,278 B2
• Time in Patent Office: Days
• US Class Current: 600/521
• 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:

(a) at least two sensors configured for obtaining the electrical signal from the patient'"'"'s heart,

(b) analog-to-digital converter circuitry for digitizing the signal to produce data segments having a time duration that is at least 1 second;

(c) means for processing data segments to identify activity related to each beat, each beat being a sub-segment of the data segment having a measurable R-R interval from the preceding beat;

(d) means for calculating the average R-R interval of the data segment by averaging the R-R intervals of the beats in the data segment;

(e) means to identify short beats within an data segment, a short beat being a beat that has an R-R interval that is a threshold amount less than the average R-R interval of the data segment;

(f) means to detect the cardiac event by processing only the beats in the data segments that are not short beats.

2. The system of claim 1 in which the sensors are electrodes adapted for implantation into a body of the patient.

3. The system of claim 1 further comprising a housing adapted for implantation into a body, and wherein the housing contains the analog-to-digital converter, the means for processing data segments, the means for calculating the average R-R interval, the means to identify short beats, and the means to detect the cardiac event.

4. 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

(a) analog-to-digital converter circuitry for digitizing the electrogram to produce electrogram segments having a time duration that is at least 1 second;

(b) means for processing an electrogram segment to identify beats of the electrogram, each beat being a sub-segment of the electrogram segment having a measurable cardiac feature;

(c) means for calculating the average of the cardiac feature within electrogram segment by averaging the feature values of the beats in the electrogram segment;

(d) means to identify rejected beats within an electrogram segment, a rejected beat being a beat that has a feature value that is a predetermined amount different than the average of the feature value calculated across an interval;

(e) means to detect the cardiac event by processing only the beats in the electrogram segments that are not rejected beats.

5. The system of claim 4 wherein the cardiac feature is the R-R interval, and wherein the identified rejected beats are short beats which have R-R intervals which are less than a selected R-R interval.

6. A system of claim 4 wherein the predetermined amount is a function of the average heart rate of the segment.

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

at least two sensors adapted to obtain an electrical signal from the patient'"'"'s heart;

a device including;

analog-to-digital converter circuitry for digitizing the electrical signal to produce electrogram segments having a time duration of at least 1 second;

a processor configured to;

identify a plurality of beats within a segment;

calculate for each of the plurality of beats a parameter indicative of the interval between each of the plurality of beats and a preceding beat, thereby generating a plurality of heart beat interval values;

categorize each of the plurality of beats based on its associated heart beat interval value;

detect the cardiac event based at least in part on the categorization of each of the plurality of beats.

8. The system of claim 7 wherein the processor is further configured to calculate a plurality of values of a heart signal parameter for a subset of the plurality of beats that fall into a particular category, and wherein the cardiac event is detected based on the plurality of values of the heart signal parameter.

9. The system of claim 8 wherein the heart signal parameter is ST segment shift, and wherein the particular category is those beats that are normal sinus rhythm beats.

10. The system of claim 7 wherein the parameter indicative of the interval between each of the plurality of beats and a preceding beat is the R-R interval.