Methods and devices for accurately classifying cardiac activity

• US 8,160,687 B2
• Filed: 05/07/2009
• Issued: 04/17/2012
• 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
• Primary Examiner(s): Bertram, Eric D.
• Application Number:
  US12/437,547
• Publication Number:
  US 20100004713A1
• Time in Patent Office: 1,076 Days
• Field of Search: 600515-516, 600/508, 600/509
• US Class Current: 600/516
• 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. 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;

wherein the operational circuitry is configured to perform a method comprising;

detecting electrical events occurring within a patient;

constructing event representations for the detected electrical events, the event representations each comprising a series of samples;

comparing a first event representation to a template having a template fiducial point by identifying an event fiducial point in the first event representation and aligning the template fiducial point and the event fiducial point to one another and calculating a first correlation between the first event representation and the template when so aligned;

again comparing the first event representation to the template, this time by selecting a different alignment of the template and event fiducial points;

selecting from at least the first correlation or the second correlation whichever indicates greater correlation as the correlation result for the first event representation;

using a series of correlation results to determine whether accurate event detection is occurring and, if not, correcting data in response to inaccurate event detection;

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;

wherein the operational circuitry is further configured such that the step of using a series of correlation results to determine whether accurate event detection is occurring comprises determining whether an alternating High-Low-High pattern of correlation results occurs and, if so, determining that an event representation having a Low correlation result results from an overdetected signal.

2. The ICS system of claim 1 wherein the operational circuitry is further configured such that the method also comprises another step of comparing the first event representation to the template by misaligning the event fiducial point from the template fiducial point and calculating a third correlation between the first event representation and the template;

wherein the second correlation is calculated with the event fiducial point aligned one or more samples before the template fiducial point, and the third correlation is calculated with the event fiducial point aligned one or more samples after the template fiducial point.

3. The ICS system of claim 1 wherein the operational circuitry is further configured such that:

the second correlation is calculated with the event fiducial point aligned one sample away from the template fiducial point in a first direction;

if the second correlation is greater than the first correlation, the method further includes yet another step of comparing the first event representation to the template by aligning the event fiducial point two samples away from the template fiducial point in the first direction and calculating a third correlation between the first event representation and the template;

or

if the second correlation is less than the first correlation, the method further includes the operational circuitry performing yet another step of comparing the first event representation to the template by aligning the event fiducial point one sample away from the template fiducial point in a direction opposite of the first direction and calculating a third correlation between the first event representation and the template.

4. The ICS system of claim 1 wherein the operational circuitry is further configured such that the method also comprises determining whether a series of detected events are Shockable or Not Shockable by comparing the correlation result for the first event representation to a threshold and, if the correlation result exceeds the threshold determining that a detected event corresponding to the first event representation is Not Shockable.

5. 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 a patient using at least one of the lead or canister electrodes;

constructing event representations for the detected electrical events, the event representations each comprising a series of samples;

comparing a first event representation to a template having a template fiducial point by identifying an event fiducial point in the first event representation and aligning the template fiducial point and the event fiducial point to one another and calculating a first correlation between the first event representation and the template when so aligned;

again comparing the first event representation to the template, this time by selecting a different alignment of the template and event fiducial points;

selecting from at least the first correlation or the second correlation whichever indicates greater correlation as the correlation result for the first event representation;

using a series of correlation results to determine whether accurate event detection is occurring and, if not, correcting data in response to inaccurate event detection;

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;

wherein the step of using a series of correlation results to determine whether accurate event detection is occurring comprises determining whether an alternating High-Low-High pattern of correlation results occurs and, if so, determining that an event representation having a Low correlation result results from an overdetected signal.

6. The method of claim 5 further comprising another step of comparing the first event representation to the template by misaligning the event fiducial point from the template fiducial point and calculating a third correlation between the first event representation and the template;

wherein the second correlation is calculated with the event fiducial point aligned one or more samples before the template fiducial point, and the third correlation is calculated with the event fiducial point aligned one or more samples after the template fiducial point.

7. The method of claim 5 wherein:

the second correlation is calculated with the event fiducial point aligned one sample away from the template fiducial point in a first direction;

if the second correlation is greater than the first correlation, the method further includes yet another step of comparing the first event representation to the template by aligning the event fiducial point two samples away from the template fiducial point in the first direction and calculating a third correlation between the first event representation and the template;

or

if the second correlation is less than the first correlation, the method further includes the operational circuitry performing yet another step of comparing the first event representation to the template by aligning the event fiducial point one sample away from the template fiducial point in a direction opposite of the first direction and calculating a third correlation between the first event representation and the template.

8. The method of claim 5 further comprising determining whether a series of detected events are Shockable or Not Shockable by comparing the correlation result for the first event representation to a threshold and, if the correlation result exceeds the threshold determining that a detected event corresponding to the first event representation is Not Shockable.