Methods and devices for accurately classifying cardiac activity

• US 8,265,749 B2
• Filed: 12/14/2009
• Issued: 09/11/2012
• Est. Priority Date: 03/07/2008
• Status: Active Grant

• Current Assignee: Cameron Health Inc (Boston Scientific Corporation)
• Original Assignee: Cameron Health Inc (Boston Scientific Corporation)
• Inventors: Allavatam, Venugopal, Palreddy, Surekha, Sanghera, Rick, Warren, Jay A.
• Primary Examiner(s): Bertram, Eric D.
• Application Number:
  US12/637,438
• Publication Number:
  US 20100094369A1
• Time in Patent Office: 1,002 Days
• Field of Search: 607/9, 607/27
• US Class Current: 607/9
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/6847 mounted on an invasive device
• CPC Class Codes: A61B 5/726 using Wavelet transforms
• CPC Class Codes: A61N 1/3704 Circuits specially adapted therefor, e.g. for sensitivity control
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion
• CPC Class Codes: A61N 1/3987 characterised by the timing or triggering of the shock

Abstract

Methods, systems, and devices for signal analysis in an implanted cardiac monitoring and treatment device such as an implantable cardioverter defibrillator. In illustrative 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. New methods for organizing the use of morphology and rate analysis in an overall architecture for rhythm classification and cardiac signal analysis are also discussed.

Claims

1. A method of cardiac signal analysis in an implantable medical device (IMD) the IMD including a number of implantable electrodes and operational circuitry coupled to the implantable electrodes for performing the method of cardiac signal analysis, the method comprising:

a) the operational circuitry detecting events in a signal captured using the implantable electrodes;

b) the operational circuitry determining which detected events to certify for use in rhythm identification by;

i) applying analysis of the morphology of a set of detected events in order to identify overdetected events such that, if a likely overdetection is identified, the likely overdetection is not certified;

ii) applying interval analysis on a set of detected events in order to identify overdetected events such that, if a likely overdetection is identified, the likely overdetection is not certified; and

iii) certifying at least some detected events of the set of detected events;

c) the operational circuitry determining whether a malignant cardiac rhythm is occurring using only certified detected events wherein each certified detected event has undergone analysis of at least b)i) and b)ii) before use to determine whether a malignant cardiac rhythm is occurring; and

d) the IMD delivering therapy in response to the malignant rhythm.

2. The method of claim 1 wherein step b) further includes:

(iv) applying analysis to sequences of consecutive events to identify overdetected events using interval and shape characteristics such that, if a likely overdetection is identified, the likely overdetection is not certified.

3. The method of claim 2 wherein step b)iii) comprises certifying all detected events of the set of detected events that are not identified as overdetections in any of i), ii) and iv).

4. The method of claim 2 further comprising the operational circuitry performing waveform appraisal on detected events and, for each event, either passing the detected event or marking the detected event as suspect, wherein step b) is performed only on detected events that pass waveform appraisal, wherein waveform appraisal operates to determine whether a detected event is noisy and, if so, to prevent any noisy detected events from passing further into the analysis.

5. The method of claim 4 wherein step b)iii) is performed by certifying all events that pass waveform appraisal and that are not identified as overdetection in any of i), ii) or iv).

6. The method of claim 1 further comprising the operational circuitry performing waveform appraisal on detected events and, for each event, either passing the detected event or marking the detected event as suspect, wherein step b) is performed only on detected events that pass waveform appraisal, wherein waveform appraisal operates to determine whether a detected event is noisy and, if so, to prevent any noisy detected events from passing further into the analysis.

7. The method of claim 6 wherein step b)iii) is performed by certifying all events that pass waveform appraisal and that are not identified as overdetection in either of i) or ii).

8. The method of claim 1 wherein step c) comprises the following:

determining that an X/Y condition has been met, wherein X represents how many malignant events have been identified in a set of Y certified detected events; and

determining that the X/Y condition meets a persistence condition.

9. The method of claim 1 wherein the signal in which events are detected is created by:

x) capturing a subject signal from the implantable electrodes; and

y) conditioning the subject signal for use in cardiac signal analysis;

wherein steps x) and y) are performed on a continuous basis, while step a) is performed iteratively using the conditioned signal.

10. The method of claim 1 wherein step b)iii) is performed by certifying events that are not identified as overdetections in either of i) or ii).

11. An implantable cardiac stimulus device (ICSD) comprising electrodes for capturing data from a recipient of the ICSD and operational circuitry coupled to the electrodes to analyze signal captured from the patient, wherein the operational circuitry is configured to perform a method comprising the following steps:

a) detecting events in a signal captured with the electrodes;

b) determining which detected events to certify for use in rhythm identification by;

i) applying analysis of the morphology of a set of detected events in order to identify overdetected events such that, if a likely overdetection is identified, the likely overdetection is not certified;

ii) applying interval analysis on a set of detected events in order to identify overdetected events such that, if a likely overdetection is identified, the likely overdetection is not certified; and

iii) certifying at least some detected events of the set of detected events;

c) determining whether a malignant cardiac rhythm is occurring using only certified detected events wherein each certified detected event has undergone analysis of at least b)i) and b)ii) before use to determine whether a malignant cardiac rhythm is occurring; and

d) delivering therapy in response to the malignant rhythm.

12. The ICSD of claim 11 wherein the operational circuitry is further configured such that step b) further includes:

(iv) applying analysis to identify overdetected events using interval and shape characteristics of sequences of consecutive events such that, if a likely overdetection is identified, the likely overdetection is not certified.

13. The ICSD of claim 12 wherein the operational circuitry is further configured such that b)iii) is performed by certifying any events that are not identified as overdetections in any of i), ii) and (iv).

14. The ICSD of claim 12 wherein the operational circuitry is further configured such that the method further comprises performing waveform appraisal on detected events and, for each event, either passing the detected event or marking the detected event as suspect, wherein step b) is performed only on detected events that pass waveform appraisal;

wherein waveform appraisal operates to determine whether a detected event is noisy and, if so, to prevent any noisy detected events from passing further into the analysis.

15. The ICSD of claim 14 wherein the operational circuitry is configured such that step b)iii) is performed by certifying all events that pass waveform appraisal and that are not identified as overdetection in any of i), ii) or iv).

16. The ICSD of claim 11 wherein the operational circuitry is further configured such that the method further comprises performing waveform appraisal on detected events and, for each event, either passing the detected event or marking the detected event as suspect, wherein step b) is performed only on detected events that pass waveform appraisal;

wherein waveform appraisal operates to determine whether a detected event is noisy and, if so, to prevent any noisy detected events from passing further into the analysis.

17. The ICSD of claim 16 wherein the operational circuitry is configured such that step b)iii) is performed by certifying all events that pass waveform appraisal and that are not identified as overdetection in either of i) or ii).

18. The ICSD of claim 11 wherein the operational circuitry is further configured such that step c) comprises the following:

determining that an X/Y condition has been met, wherein X represents how many malignant events have been identified in a set of Y certified detected events; and

determining that the X/Y condition meets a persistence condition.

19. The ICSD of claim 11 wherein the operational circuitry is further configured such that the signal in which events are detected is created by:

x) capturing a subject signal from electrodes configured to be implanted in a patient subject; and

y) conditioning the signal for use in cardiac signal analysis;

wherein steps x) and y) are performed on a continuous basis, while step a) is performed iteratively using the conditioned signal.

20. The ICSD of claim 11 wherein the operational circuitry is further configured such that step b)iii) is performed by certifying all events that are not identified as overdetections in either of i) or ii).