Methods and devices for accurately classifying cardiac activity

• US 8,600,489 B2
• Filed: 03/30/2012
• Issued: 12/03/2013
• Est. Priority Date: 05/07/2008
• Status: Active Grant

• Current Assignee: Cameron Health Inc (Boston Scientific Corporation)
• Original Assignee: Cameron Health Inc (Boston Scientific Corporation)
• Inventors: Warren, Jay A., Sanghera, Rick, Allavatam, Venugopal, Palreddy, Surekha
• Primary Examiner(s): Bertram, Eric D.
• Application Number:
  US13/436,448
• Publication Number:
  US 20120197334A1
• Time in Patent Office: 613 Days
• Field of Search: 600/516, 607/9
• 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 5/349 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 electrical events occurring within the patient, wherein the detected electrical events are separated by intervals;

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

identifying one or more detected events as likely occurring due to overdetection;

analyzing intervals around the events identified as likely occurring due to overdetection to determine whether the likely overdetection is likely a T-wave and;

a) if the likely overdetection is likely a T-wave, correcting data relating to the overdetection to reduce calculated cardiac rate;

or

b) if the likely overdetection is unlikely to be a T-wave, disabling data correction methods in the ICS system for at least the likely overdetection;

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 step of analyzing intervals to determine whether the likely overdetection is likely a T-wave includes treating an period between the likely overdetection and an immediately preceding detected electrical event as a presumed QT period and treating a period between the detected electrical event that immediately precedes the likely overdetection and a detected electrical event immediately after the likely overdetection as a presumed RR interval, and applying an accepted relationship to the presumed RR interval and presumed QT period and:

if the accepted relationship is met for the presumed RR interval and presumed QT period, determining that the likely overdetection is likely to be a T-wave;

or

if the accepted relationship is not met for the presumed RR presumed interval and resumed QT period, determining that the likely overdetection is unlikely to be a T-wave.

3. The method of claim 2 wherein the accepted relationship defines an expected relationship between the RR interval and QT period of a cardiac cycle and is chosen from the group consisting of Bazett'"'"'s formula, Friderica'"'"'s formula, or a regression formula.

4. The method of claim 1 wherein the step of analyzing intervals to determine whether the likely overdetection is likely a T-wave includes comparing an interval between the likely overdetection and an immediately preceding detected event to a threshold and, if the threshold is exceeded, finding that the likely overdetection is not likely to be a T-wave.

5. A method of operation in an implantable cardiac system comprising a canister housing operational circuitry and a plurality of electrodes for sensing cardiac activity, the plurality of electrodes coupled to the operational circuitry and the operational circuitry comprising a processor and associated logic circuits for processing cardiac signals from the electrodes;

the method comprising;

the operational circuitry detecting electrical events occurring within the patient by use of the electrodes, wherein the detected electrical events are separated by intervals;

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

the operational circuitry identifying one or more detected events as likely occurring due to overdetection;

the operational circuitry analyzing intervals around the events identified as likely occurring due to overdetection to determine whether the likely overdetection is likely a T-wave and;

a) if the likely overdetection is likely a T-wave, the operational circuitry correcting data relating to the overdetection to reduce calculated cardiac rate;

or

b) if the likely overdetection is unlikely to be a T-wave, the operational circuitry disabling data correction methods in the ICS system for at least the likely overdetection; and

the operational circuitry determining whether a likely cardiac arrhythmia is occurring.

6. The method of claim 5 wherein the implantable cardiac system further comprises therapy delivery components for providing therapy to the patient, wherein the method further comprises:

If a likely cardiac arrhythmia is occurring, the operational circuitry determining whether stimulus is needed; and

if stimulus is needed, the implantable cardiac system using the therapy delivery components to deliver therapy to the patient.

7. The method of claim 5 wherein the step of the operational circuitry analyzing intervals to determine whether the likely overdetection is likely a T-wave includes treating an period between the likely overdetection and an immediately preceding detected electrical event as a presumed QT period and treating a period between the detected electrical event that immediately precedes the likely overdetection and a detected electrical event immediately after the likely overdetection as a presumed RR interval, and applying an accepted relationship to the presumed RR interval and presumed QT period and:

if the accepted relationship is met for the presumed RR interval and presumed QT period, determining that the likely overdetection is likely to be a T-wave;

or

if the accepted relationship is not met for the presumed RR interval and presumed QT period, determining that the likely overdetection is unlikely to be a T-wave.

8. The method of claim 7 wherein the accepted relationship defines an expected relationship between the RR interval and QT period of a cardiac cycle and is chosen from the group consisting of Bazett'"'"'s formula, Friderica'"'"'s formula, or a regression formula.

9. The method of claim 5 wherein the step of the operational circuitry analyzing intervals to determine whether the likely overdetection is likely a T-wave includes comparing an interval between the likely overdetection and an immediately preceding detected event to a threshold and, if the threshold is exceeded, finding that the likely overdetection is not likely to be a T-wave.

10. An implantable cardiac system comprising a canister housing operational circuitry and a plurality of electrodes for sensing cardiac activity, the plurality of electrodes coupled to the operational circuitry and the operational circuitry comprising a processor and associated logic circuits for processing cardiac signals from the electrodes;

the operational circuitry configured to perform the following to monitor cardiac activity of a patient;

the operational circuitry detecting electrical events occurring within the patient by use of the electrodes, wherein the detected electrical events are separated by intervals;

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

the operational circuitry identifying one or more detected events as likely occurring due to overdetection;

the operational circuitry analyzing intervals around the events identified as likely occurring due to overdetection to determine whether the likely overdetection is likely a T-wave and;

a) if the likely overdetection is likely a T-wave, the operational circuitry correcting data relating to the overdetection to reduce calculated cardiac rate;

or

b) if the likely overdetection is unlikely to be a T-wave, the operational circuitry disabling data correction methods in the ICS system for at least the likely overdetection; and

the operational circuitry determining whether a likely cardiac arrhythmia is occurring.

11. The implantable cardiac system of claim 10 further comprising therapy delivery components for providing therapy to the patient coupled to the operational circuitry;

wherein the operational circuitry and therapy delivery components are configured such that the operational circuitry controls therapy delivery by the therapy delivery components;

wherein the operational circuitry is also configured to determine whether stimulus is needed in response to determining that a likely cardiac arrhythmia is occurring and, if so, directing the therapy delivery components to deliver therapy to the patient.

12. The implantable cardiac system of claim 10 wherein the operational circuitry is further configured such that:

the step of the operational circuitry analyzing intervals to determine whether the likely overdetection is likely a T-wave includes treating an period between the likely overdetection and an immediately preceding detected electrical event as a presumed QT period and treating a period between the detected electrical event that immediately precedes the likely overdetection and a detected electrical event immediately after the likely overdetection as a presumed RR interval, and applying an accepted relationship to the presumed RR interval and presumed QT period and;

if the accepted relationship is met for the presumed QT period and the presumed RR interval, determining that the likely overdetection is likely to be a T-wave;

or

if the accepted relationship is not met, determining that the likely overdetection is unlikely to be a T-wave.

13. The implantable cardiac system of claim 12 wherein the operational circuitry is further configured such that the accepted relationship defines an expected relationship between the RR interval and QT period of a cardiac cycle and is chosen from the group consisting of Bazett'"'"'s formula, Friderica'"'"'s formula, or a regression formula.

14. The implantable cardiac system of claim 10 wherein the operational circuitry is further configured such that analyzing intervals to determine whether the likely overdetection is likely a T-wave includes comparing an interval between the likely overdetection and an immediately preceding detected event to a threshold and, if the threshold is exceeded, finding that the likely overdetection is not likely to be a T-wave.