METHODS AND DEVICES FOR ACCURATELY CLASSIFYING CARDIAC ACTIVITY

• US 20140046396A1
• Filed: 10/21/2013
• Published: 02/13/2014
• Est. Priority Date: 05/07/2008
• Status: Active Grant

• Current Assignee: Cameron Incorporated (Schlumberger NV)
• Original Assignee: Cameron Incorporated (Schlumberger NV)
• Inventors: Warren, Jay A., Sanghera, Rick, Allavatam, Venugopal, Palreddy, Surekha
• Granted Patent: US 8,880,161 B2
• Time in Patent Office: Days
• US Class Current: 607/25
• 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 5/35 by template matching
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/364 Detecting abnormal ECG interval, e.g. extrasystoles, ectopic heartbeats
• CPC Class Codes: A61B 5/4836 Diagnosis combined with treatment in closed-loop systems or methods A61B5/0036 takes precedence
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 5/726 using Wavelet transforms
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00
• CPC Class Codes: A61N 1/3621 for treating or preventing abnormally high heart rate
• CPC Class Codes: A61N 1/36514 controlled by a physiological quantity other than heart potential, e.g. blood pressure controlled by two or more physical parameters A61N1/36585
• CPC Class Codes: A61N 1/36592 controlled by the heart rate variability
• CPC Class Codes: A61N 1/37 Monitoring; Protecting
• CPC Class Codes: A61N 1/3987 characterised by the timing or triggering of the shock
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

Methods, systems, and devices for signal analysis in an implanted cardiac monitoring and treatment device such as an implantable cardioverter defibrillator. In some examples, captured data including detected events is analyzed to identify likely overdetection of cardiac events. In some illustrative examples, when overdetection is identified, data may be modified to correct for overdetection, to reduce the impact of overdetection, or to ignore overdetected data. Several examples emphasize the use of morphology analysis using correlation to static templates and/or inter-event correlation analysis.

Claims

1. A method of operation in an implantable cardiac stimulus (ICS) system comprising a canister housing operational circuitry for the ICS system, the canister having a canister electrode disposed thereon, and a lead having at least a first lead electrode disposed thereon, the canister electrode and the first lead electrode electrically coupled to the operational circuitry;

the method comprising;

detecting cardiac electrical events occurring within the patient;

constructing event representations for the detected electrical events;

calculating a cardiac rate using a set of the detected electrical events;

comparing the event representations to a template representative of a known cardiac state to establish a set of correlations;

analyzing the set of correlations for one of the following;

a) a short pattern calling for a set of 3 or more consecutive correlations to include a High-Low-High pattern around first boundaries, or

b) a long pattern calling for a set of 5 or more consecutive correlations to include High-Low-High-Low-High correlations around second boundaries,

wherein the first boundaries require stronger correlation for “

High”

than the second boundaries;

if either the short pattern or the long pattern is identified, characterizing one or more detected events as overdetections and modifying the calculated cardiac rate;

determining whether a likely cardiac arrhythmia is occurring and, if so, determining whether stimulus is needed; and

if stimulus is needed, delivering electrical stimulus to the patient from the ICS system.

2. The method of claim 1 wherein the second boundaries are defined by:

identifying a mean correlation in the set of correlations; and

establishing an upper bound a set distance above the mean correlation.

3. The method of claim 1 further comprising analyzing the set of detections for the following:

c) a triplet pattern comprising at least two sequences of High-Low-Low correlations, wherein, if the triplet pattern is identified, the method includes characterizing each “

Low”

event as an overdetection and calculating intervals between High events for use in re-calculating rate.

4. The method of claim 1 wherein the known cardiac state is a normal sinus rhythm.

5. The method of claim 1 wherein the canister and lead are disposed entirely subcutaneously between the skin and ribs of the patient.

6. A method of operation in an implantable cardiac stimulus (ICS) system comprising a canister housing operational circuitry for the ICS system, the canister having a canister electrode disposed thereon, and a lead having at least a first lead electrode disposed thereon, the canister electrode and the first lead electrode electrically coupled to the operational circuitry;

the method comprising;

detecting electrical events occurring within the patient;

constructing event representations for the detected electrical events;

for a set of events N, N-1, N-2 and N-3, comparing the Nth event to each of the N-1, N-2 and N-3 events by correlation analysis;

determining, using the results of the correlation analysis, whether the set of events indicates one of the following;

overdetection,

benign cardiac rhythm, or

likely cardiac arrhythmia; and

if likely cardiac arrhythmia is identified, determining whether stimulus is needed; and

if stimulus is needed, delivering electrical stimulus to the patient from the ICS system;

wherein overdetection is identified if the correlation analysis indicates a pattern of correlations between the events N, N-1, N-2 and N-3 that corresponds to overdetection.

7. The method of claim 6 wherein the method includes determining that overdetection is occurring if the step of comparing the Nth event to each of the N-1, N-2 and N-3 events by correlation analysis results in a pattern of correlations of the following type:

low correlation to N-1 and N-3 events, and high correlation to the N-2 event.

8. The method of claim 6 further comprising:

calculating a cardiac rate using the detected electrical events; and

if the set of events, N, N-1, N-2, N-3 indicates overdetection, correcting data relating to one or more overdetected events and recalculating the calculated cardiac rate.

9. The method of claim 6 wherein the step of determining whether the set of events indicates one of the following:

overdetection, benign cardiac rhythm, or likely cardiac arrhythmia includes determining whether the Nth event correlates highly to at least one of the N-1, N-2 or N-3 events and, if so, determining that a benign cardiac rhythm is occurring.

10. The method of claim 9 wherein the step of determining whether the set of events indicates one of the following:

overdetection, benign cardiac rhythm, or likely cardiac arrhythmia includes determining whether the Nth event correlates closely to each of the N-1, N-2 or N-3 events and, if so, determining that a benign cardiac rhythm is occurring, further wherein “

correlates highly”

indicates a relatively higher correlation than “

correlates closely.”

11. A method of operation in an implantable cardiac stimulus (ICS) system comprising a canister housing operational circuitry for the ICS system, the canister having a canister electrode disposed thereon, and a lead having at least a first lead electrode disposed thereon, the canister electrode and the first lead electrode electrically coupled to the operational circuitry;

the method comprising;

detecting electrical events occurring within the patient;

constructing event representations for the detected electrical events;

for a set of events N, N-1, N-2 and N-3, comparing the Nth event to each of the N-1, N-2 and N-3 events by correlation analysis;

identifying a pattern of triple detection by application of a rule set for triple detection;

discarding the N-1 and N-2 events in response to identification of a pattern of triple detection and calculating a cardiac rate for the patient relying, at least in part, upon the entire interval from the Nth event to the N-3 event;

wherein the rule set for triple detection uses a Static Template representative of a cardiac event occurring while the patient is in a known benign cardiac state and the rule set comprises the following requirements;

a) finding that the Nth event has a High correlation to the N-3 event;

b) finding that the Nth event has low correlation to each of the N-1 and N-2 events; and

c) finding the N-1 and N-2 events have low correlations to the Static Template;

wherein the rule set for triple detection only indicates a pattern of triple detection if each of a), b) and c) are met.

12. The method of claim 11 wherein:

the rule set further comprises d) finding the Nth and N-3 events have high correlation to the Static Template; and

the rule set for triple detection only indicates a pattern of triple detection if each of a), b), c) and d) are met.

13. The method of claim 11 wherein:

the rule set further comprises d) finding the N-1 and N-2 events are wider than a Width Threshold; and

the rule set for triple detection only indicates a pattern of triple detection if each of a), b), c) and d) are met.

14. The method of claim 13 wherein the width threshold is in the range of 100 to 140 milliseconds.

15. The method of claim 11 wherein:

the rule set further comprises d) finding the N-1 and N-2 events are both of the same polarity, where polarity is defined for each event by the polarity of the signal peak having the greatest magnitude for each event; and

the rule set for triple detection only indicates a pattern of triple detection if each of a), b), c) and d) are met.

16. The method of claim 11 wherein:

the rule set further comprises d) finding the interval between the Nth and N-3 events is less than a duration threshold;

the duration threshold is in the range of 800 to 1200 milliseconds; and

the rule set for triple detection only indicates a pattern of triple detection if each of a), b), c) and d) are met.