Methods and Devices for Identifying Overdetection of Cardiac Signals

• US 20110098585A1
• Filed: 10/27/2010
• Published: 04/28/2011
• Est. Priority Date: 10/27/2009
• Status: Active Grant

• Current Assignee: Cameron Health Inc (Boston Scientific Corporation)
• Original Assignee: Cameron Health Inc (Boston Scientific Corporation)
• Inventors: Palreddy, Surekha, Warren, Jay A., Sanghera, Rick, Allavatam, Venugopal
• Granted Patent: US 8,265,737 B2
• Time in Patent Office: Days
• US Class Current: 600/509
• CPC Class Codes: A61B 5/276 Protection against electrode failure
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/726 using Wavelet transforms

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, sensed 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.

Claims

1. A method of operating an implantable cardiac system (ICS), the ICS comprising operational circuitry coupled to a plurality of implantable electrodes for sensing electric signals, the method comprising:

sensing signals from the electrodes;

detecting events in the sensed signals;

applying event and feature/proximity analysis rules to the detected events to identify overdetection of cardiac signals;

performing ameliorative action in response to identified overdetection; and

determining whether therapy is likely needed.

2. The method of claim 1 wherein the event and feature/proximity analysis rules are applied across three detected events ([n−

2], [n−

1], [n]) as follows;

identifying a late peak in detection [n−

2], identifying an early peak and a late peak in detection [n−

1] and identifying a detection time for event [n];

measuring a first interval from the late peak of detection [n−

1] to the detection time of event [n] and comparing the first interval to a t1 threshold;

measuring a second interval from the late peak of detection [n−

2] to the early peak of detection [n−

1] and comparing the second interval to a t2 threshold; and

the method comprises

if the first interval is less than the t1 threshold and the second interval is less than the t2 threshold, identifying detection [n−

1] as an overdetected event.

3. The method of claim 1 wherein the event and feature/proximity analysis rules are applied across three detected events ([n−

2], [n−

1], [n]) as follows;

identifying an early peak and a late peak in detection [n−

2], identifying an early peak and a late peak in detection [n−

1] and identifying a detection time for event [n];

measuring a first interval from the late peak of detection [n−

1] to the detection time of event [n] and comparing the first interval to a t1 threshold;

comparing the early peak of the [n−

2] detection to the early peak of the [n−

1] detection and determining whether the two early peaks alternate polarities; and

the method comprises

if the first interval is less than the t1 threshold and the early peaks of the [n−

2] and [n−

1] alternate polarities, identifying detection [n−

1] as an overdetected event.

4. The method of claim 1 wherein the event and feature/proximity analysis rules are applied across three detected events ([n−

2], [n−

1], [n]) as follows;

identifying an early peak and a late peak in detection [n−

2], identifying an early peak and a late peak in detection [n−

1] and identifying a detection time for event [n];

measuring a first interval from the late peak of detection [n−

1] to the detection time of event [n] and comparing the first interval to a t1 threshold;

measuring a second interval from the late peak of detection [n−

2] to the early peak of detection [n−

1] and comparing the second interval to a t2 threshold;

comparing the early peak of the [n−

2] detection to the early peak of the [n−

1] detection and determining whether the two early peaks alternate polarities; and

the method comprises;

a) if the first interval is less than the t1 threshold and the early peaks of the [n−

2] and [n−

1] alternate polarities, identifying detection [n−

1] as an overdetected event; and

b) if the first interval is less than the t1 threshold and the second interval is less than the t2 threshold, identifying detection [n−

1] as an overdetected event.

5. The method of claim 1 wherein:

the operational circuitry is contained in a canister configured for implantation in the torso of a patient;

the canister serves as one of the electrodes;

the ICS further comprises a lead coupled to the canister, the lead including at least two electrodes;

the operational circuitry is configured to select a default sensing pair from the electrodes on the canister and the lead; and

the ameliorative action comprises performing a vector selection process to determine whether to switch to a different default sensing pair.

6. The method of claim 1 wherein the operational circuitry comprises input circuitry for receiving and amplifying signals from the electrodes and the ameliorative action comprises modifying a gain setting of the input circuitry.

7. The method of claim 1 wherein the operational circuitry comprises input circuitry for receiving and filtering signals from the electrodes and the ameliorative action comprises modifying a filtering setting of the input circuitry.

8. An implantable cardiac system (ICS), the ICS comprising operational circuitry coupled to a plurality of implantable electrodes for sensing electric signals, the operational circuitry comprising a controller coupled to memory having an instruction set configuring the ICS to perform a method of cardiac signal analysis comprising:

sensing signals from the electrodes;

detecting events in the sensed signals;

applying event and feature/proximity analysis rules to the detected events to identify overdetection of cardiac signals; and

identifying overdetection of cardiac signal and performing ameliorative action in response to the identified overdetection.

9. The ICS of claim 8 wherein the operational circuitry is configured to apply the event and feature/proximity analysis rules across three detected events ([n−

2], [n−

1], [n]) as follows;

identifying a late peak in detection [n−

2], identifying an early peak and a late peak in detection [n−

1] and identifying a detection time for event [n];

measuring a first interval from the late peak of detection [n−

1] to the detection time of event [n] and comparing the first interval to a t1 threshold;

measuring a second interval from the late peak of detection [n−

2] to the early peak of detection [n−

1] and comparing the second interval to a t2 threshold;

if the first interval is less than the t1 threshold and the second interval is less than the t2 threshold, identifying detection [n−

1] as an overdetected event.

10. The ICS of claim 8 wherein the operational circuitry is configured to apply the event and feature/proximity analysis rules across three detected events ([n−

2], [n−

1], [n]) as follows;

identifying an early peak and a late peak in detection [n−

2], identifying an early peak and a late peak in detection [n−

1] and identifying a detection time for event [n];

measuring a first interval from the late peak of detection [n−

1] to the detection time of event [n] and comparing the first interval to a t1 threshold;

comparing the early peak of the [n−

2] detection to the early peak of the [n−

1] detection and determining whether the two early peaks alternate polarities;

if the first interval is less than the t1 threshold and the early peaks of the [n−

2] and [n−

1] alternate polarities, identifying detection [n−

1] as an overdetected event.

11. The ICS of claim 8 wherein the operational circuitry is configured to apply the event and feature/proximity analysis rules across three detected events ([n−

2], [n−

1], [n]) as follows;

identifying an early peak and a late peak in detection [n−

2], identifying an early peak and a late peak in detection [n−

1] and identifying a detection time for event [n];

measuring a first interval from the late peak of detection [n−

1] to the detection time of event [n] and comparing the first interval to a t1 threshold;

measuring a second interval from the late peak of detection [n−

2] to the early peak of detection [n−

1] and comparing the second interval to a t2 threshold;

comparing the early peak of the [n−

2] detection to the early peak of the [n−

1] detection and determining whether the two early peaks alternate polarities; and

;

a) if the first interval is less than the t1 threshold and the early peaks of the [n−

2] and [n−

1] alternate polarities, identifying detection [n−

1] as an overdetected event; and

b) if the first interval is less than the t1 threshold and the second interval is less than the t2 threshold, identifying detection [n−

1] as an overdetected event.

12. The ICS of claim 8 wherein:

the operational circuitry is contained in a canister configured for implantation in the torso of a patient;

the canister serves as one of the electrodes;

the ICS further comprises a lead coupled to the canister, the lead including at least two electrodes;

the operational circuitry is configured to select a default sensing pair from the electrodes on the canister and lead; and

the ameliorative action comprises performing a vector selection process to determine whether to switch to a different default sensing pair.

13. The ICS of claim 8 wherein the operational circuitry comprises input circuitry for receiving and amplifying signals from the electrodes and the ameliorative action comprises modifying a gain setting of the input circuitry.

14. The ICS of claim 8 wherein the operational circuitry comprises input circuitry for receiving and filtering signals from the electrodes and the ameliorative action comprises modifying a filtering setting of the input circuitry.

15. An implantable cardiac system (ICS), comprising:

means for sensing signals from an implanted location;

means for detecting events in sensed signals;

means for applying event and feature/proximity analysis rules to detected events to identify overdetection of cardiac signals; and

means for ameliorating overdetection of cardiac signals.

16. The ICS of claim 15 wherein the means for applying event and feature/proximity analysis rules includes a controller configured to apply the event and feature/proximity analysis rules across three detected events ([n−

2], [n−

1], [n]) as follows;

identifying a late peak in detection [n−

2], identifying an early peak and a late peak in detection [n−

1] and identifying a detection time for event [n];

measuring a first interval from the late peak of detection [n−

1] to the detection time of event [n] and comparing the first interval to a t1 threshold;

measuring a second interval from the late peak of detection [n−

2] to the early peak of detection [n−

1] and comparing the second interval to a t2 threshold;

if the first interval is less than the t1 threshold and the second interval is less than the t2 threshold, identifying detection [n−

1] as an overdetected event.

17. The ICS of claim 15 wherein the means for applying event and feature/proximity analysis rules includes a controller configured to apply the event and feature/proximity analysis rules across three detected events ([n−

2], [n−

1], [n]) as follows;

identifying an early peak and a late peak in detection [n−

2], identifying an early peak and a late peak in detection [n−

1] and identifying a detection time for event [n];

measuring a first interval from the late peak of detection [n−

1] to the detection time of event [n] and comparing the first interval to a t1 threshold;

comparing the early peak of the [n−

2] detection to the early peak of the [n−

1] detection and determining whether the two early peaks alternate polarities;

if the first interval is less than the t1 threshold and the early peaks of the [n−

2] and [n−

1] alternate polarities, identifying detection [n−

1] as an overdetected event.

18. The ICS of claim 15 wherein the means for applying event and feature/proximity analysis rules includes a controller configured to apply the event and feature/proximity analysis rules across three detected events ([n−

2], [n−

1], [n]) as follows;

identifying an early peak and a late peak in detection [n−

2], identifying an early peak and a late peak in detection [n−

1] and identifying a detection time for event [n];

measuring a first interval from the late peak of detection [n−

1] to the detection time of event [n] and comparing the first interval to a t1 threshold;

measuring a second interval from the late peak of detection [n−

2] to the early peak of detection [n−

1] and comparing the second interval to a t2 threshold;

comparing the early peak of the [n−

2] detection to the early peak of the [n−

1] detection and determining whether the two early peaks alternate polarities; and

;

a) if the first interval is less than the t1 threshold and the early peaks of the [n−

2] and [n−

1] alternate polarities, identifying detection [n−

1] as an overdetected event; and

b) if the first interval is less than the t1 threshold and the second interval is less than the t2 threshold, identifying detection [n−

1] as an overdetected event.

19. The ICS of claim 15 wherein:

the means for sensing signals comprises a plurality of implantable electrodes; and

the means for detecting events in sensed signals comprises a comparing circuit for comparing a received signal to a sensing threshold and, when the sensing threshold is crossed by the received signal, generating an event output.

20. The ICS of claim 19 wherein:

the means for performing ameliorative action comprises switching means for selecting a default sensing pair from among the plurality of implantable electrodes for use in sensing cardiac activity; and

the means for performing ameliorative action is configured to adjust the switching means to modify the default sensing pair in response to identification of overdetected events.

21. The ICS of claim 19 wherein:

the means for performing ameliorative action comprises input circuitry for receiving and amplifying signals from the plurality of implantable electrodes and providing the received and amplified signals to the means for detecting events; and

the means for performing ameliorative action is operative to modify a gain setting of the input circuitry in response to identification of overdetected events.

22. The ICS of claim 19 wherein:

the means for performing ameliorative action comprises input circuitry for receiving and filtering signals from the plurality of implantable electrodes and providing the received and filtered signals to the means for detecting events; and

the means for performing ameliorative action is operative to modify a filtering setting of the input circuitry in response to identification of overdetected events.