Systems and methods for sensing vector selection in an implantable medical device

• US 10,575,740 B2
• Filed: 05/31/2016
• Issued: 03/03/2020
• Est. Priority Date: 05/26/2006
• Status: Active Grant

• Current Assignee: Cameron Health Inc (Boston Scientific Corporation)
• Original Assignee: Cameron Health Inc (Boston Scientific Corporation)
• Inventors: Sanghera, Rick, Allavatam, Venugopal
• Primary Examiner(s): Layno, Carl H
• Assistant Examiner(s): Ghand, Jennifer L
• Application Number:
  US15/169,207
• Publication Number:
  US 20160270681A1
• Time in Patent Office: 1,372 Days
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/287 Holders for multiple electrodes, e.g. electrode catheters for electrophysiological study [EPS]
• CPC Class Codes: A61B 5/341 Vectorcardiography [VCG]
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: A61N 1/368 comprising more than one electrode co-operating with different heart regions A61N1/3622, A61N1/3627 take precedence
• CPC Class Codes: A61N 1/3704 Circuits specially adapted therefor, e.g. for sensitivity control
• CPC Class Codes: A61N 1/37211 Means for communicating with stimulators
• CPC Class Codes: A61N 1/3918 characterised by shock pathway, e.g. by electrode configuration
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion

Abstract

Methods and devices for sensing vector analysis in an implantable cardiac stimulus system. In an illustrative example, a first sensing vector is analyzed to determine whether it is suitable, within given threshold conditions, for use in cardiac event detection and analysis. If so, the first vector may be selected for detection and analysis. Otherwise, one or more additional vectors are analyzed. A detailed example illustrates methods for analyzing sensing vectors by the use of a scoring system. Devices adapted to perform these methods are also discussed, including implantable medical devices adapted to perform these methods, and systems comprising implantable medical devices and programmers adapted to communicate with implantable medical devices, the systems also being adapted to perform these methods. Another example includes a programmer configured to perform these methods including certain steps of directing operation of an associated implanted or implantable medical device.

Claims

1. A medical device comprising an implantable stimulus device including an implantable lead and operational circuitry contained within a housing, the operational circuitry coupled to a plurality of electrodes for sensing cardiac activity, wherein the plurality of electrodes includes at least one electrode on the housing and at least one electrode on the lead;

the operational circuitry being configured to perform the following;

receive a signal from the electrodes;

sense a plurality of detected events from the signal received from the electrodes, the detected events separated by intervals;

analyze consecutive intervals defined between pairs of detected events;

determine that at least two consecutive intervals are equal within a predefined margin;

determine that each of the at least two equal consecutive intervals are shorter than a predefined duration; and

after determining the consecutive intervals are equal within the predefined margin and shorter than the predefined duration, mark whichever of the two detected events occurring at the start of each of the consecutive intervals is of lesser amplitude as noise and the other of the two detected events as QRS; and

wherein the operational circuitry is configured to sense the plurality of detected events by;

comparing a sensing threshold set to a selected amplitude to the received signal from the electrodes;

observing crossing of the sensing threshold and declaring a detected event;

applying a refractory period for predetermined period of time; and

again comparing the sensing threshold set to the selected amplitude to the received signal from the electrodes after the refractory period to sense a subsequent detected event.

2. The medical device of claim 1 wherein the plurality of electrodes define a plurality of sensing vectors and the operational circuitry is configured to perform vector selection to select a default vector for use in sensing cardiac activity, in which the operational circuitry is configured to analyze said detected events marked as QRS to determine an amplitude factor used for vector selection.

3. The medical device of claim 2 wherein the operational circuitry is configured to analyze said detected events marked as noise to determine a noise factor used for vector selection.

4. The medical device of claim 1 wherein the plurality of electrodes define a plurality of sensing vectors and the operational circuitry is configured to perform vector selection to select a default vector for use in sensing cardiac activity, in which the operational circuitry is configured to analyze detected events marked as noise to determine a noise factor used for vector selection.

5. The medical device of claim 1 wherein the operational circuitry is configured to set the selected amplitude in a setting process by:

the operational circuitry setting an initial sensing floor;

the operational circuitry comparing the initial sensing floor to the received signal until the received signal crosses the initial sensing floor;

the operational circuitry raising the sensing floor until a timeout occurs; and

the operational circuitry setting the selected amplitude relative a level of the sensing floor at which the timeout occurs.

6. A medical device as in claim 1 wherein the implantable cardiac stimulus device is configured as a subcutaneous-only implantable defibrillator such that all electrodes are disposed outside of the ribcage of the patient.

7. A medical device as in claim 1 wherein the implantable cardiac stimulus device is configured as a transvenous implantable defibrillator such that the lead is configured to enter the patient'"'"'s venous system and attach to the heart thereof.

8. A medical device as in claim 1 wherein the housing has at least two electrodes disposed thereon.

9. A medical device as in claim 1, wherein the operational circuitry is configured such that the predefined margin calls for the duration of the at least two consecutive intervals to be within a set time period of one another.

10. A medical device as in claim 9 wherein the set time period is 50 milliseconds.

11. A method of operation in a medical device comprising a housing, an implantable lead, a plurality of electrodes and operational circuitry disposed within the housing, the operational circuitry coupled to the plurality of electrodes for sensing cardiac activity, the plurality of electrodes includes at least one electrode on the housing and at least one electrode on the lead, the method comprising the operational circuitry:

receiving a signal from the electrodes;

sensing a plurality of detected events from the signal received from the electrodes, the detected events separated by intervals;

analyzing consecutive intervals defined between pairs of detected events;

determining that at least two consecutive intervals are equal, within a predefined margin;

determining that the at least two equal consecutive intervals are each shorter than a predefined duration;

after determining the consecutive intervals are equal within the predefined margin and shorter than the predefined duration, marking whichever of the two detected events occurring at the start of each of the consecutive intervals is of lesser amplitude as noise and the other of the two detected events as QRS; and

using the QRS to identify and select a default sensing vector for the medical device and using the default sensing vector to sense cardiac activity of a patient;

wherein the operational circuitry is configured to sense the plurality of detected events by;

comparing a sensing threshold set to a selected amplitude to the received signal from the electrodes;

observing crossing of the sensing threshold and declaring a detected event;

applying a refractory period for predetermined period of time; and

again comparing the sensing threshold set to the selected amplitude to the received signal from the electrodes after the refractory period to sense a subsequent detected event.

12. A method of vector selection in a medical device having a plurality of electrodes that define a plurality of sensing vectors and operational circuitry coupled to the plurality of electrodes, the method comprising:

performing the method of claim 11; and

analyzing said detected events marked as QRS to determine an amplitude factor used for vector selection.

13. A method of vector selection as in claim 12, further comprising analyzing said detected events marked as noise to determine a noise factor used for vector selection.

14. A method of vector selection in a medical device having a plurality of electrodes that define a plurality of sensing vectors and operational circuitry coupled to the plurality of electrodes, the method comprising:

performing the method of claim 11; and

analyzing detected events marked as noise to determine a noise factor used for vector selection.

15. A method as in claim 11 further comprising the operational circuitry setting the selected amplitude by:

setting an initial sensing floor;

comparing the initial sensing floor to the received signal until the received signal crosses the initial sensing floor;

raising the sensing floor until a timeout occurs; and

setting the selected amplitude relative to a level of the sensing floor at which the timeout occurs.

16. A method as in claim 11 wherein the medical device is a subcutaneous-only implantable defibrillator, and the operational circuitry comprises a charging sub-circuit and a power storage sub-circuit for building up a stored voltage for cardiac stimulus taking the form of defibrillation therapy, and the method further comprises the operational circuitry using the selected sensing vector to identify a treatable arrhythmia and the operational circuitry delivering a defibrillation therapy, and the step of receiving a signal from the electrodes is performed using electrodes placed outside of the ribcage of a patient.

17. A method as in claim 11 wherein the medical device is a transvenous defibrillator and the implantable lead is configured to be placed inside of the heart of a patient, and the operational circuitry comprises a charging sub-circuit and a power storage sub-circuit for building up a stored voltage for cardiac stimulus taking the form of defibrillation therapy, and the method further comprises the operational circuitry using the selected sensing vector to identify a treatable arrhythmia and the operational circuitry delivering a defibrillation therapy, and the step of receiving a signal from the electrodes is performed using one or more electrodes in or on the heart.

18. A method as in claim 11 wherein the housing has at least two electrodes disposed thereon.

19. A method as in claim 11, wherein the operational circuitry is configured such that the predefined margin calls for the durations of the at least two consecutive intervals to be within a set time period of one another.

20. A method as in claim 19 wherein the set time period is 50 milliseconds.