SYSTEMS AND METHODS FOR SENSING VECTOR SELECTION IN AN IMPLANTABLE MEDICAL DEVICE USING A POLYNOMIAL APPROACH

• US 20080172100A1
• Filed: 01/16/2007
• Published: 07/17/2008
• Est. Priority Date: 01/16/2007
• Status: Active Grant

• Current Assignee: Cameron Health Inc (Boston Scientific Corporation)
• Original Assignee: Cameron Health Inc (Boston Scientific Corporation)
• Inventors: Sanghera, Rick, Allavatam, Venugopal
• Granted Patent: US 7,783,340 B2
• Time in Patent Office: Days
• US Class Current: 607/30
• 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: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371
• CPC Class Codes: A61N 1/3918 characterised by shock pathway, e.g. by electrode configuration

Abstract

Methods and devices configured for analyzing sensing vectors 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 sensing vector may be selected for detection and analysis. Otherwise, and in other examples, one or more additional sensing vectors are analyzed. A polynomial may be used during analysis to generate a metric indicating the suitability of the sensing vector for use in cardiac event detection and analysis. Additional illustrative examples include systems and devices adapted to perform at least these methods, including implantable medical devices, and/or programmers for implantable medical devices, and/or systems having both programmers and implantable medical devices that cooperatively analyze sensing vectors.

Claims

1. A method involving:

an implantable medical device adapted to define a plurality of sensing vectors between electrodes implanted in a patient, and

a programmer adapted for communication with the implantable medical device;

the method comprising;

the implantable medical device capturing cardiac signal data using at least one of the plurality of sensing vectors;

(x) analyzing data related to the captured cardiac signal data and;

(i) determining the data indicates a plurality of likely cardiac events in relatively clear fashion and, if so, generating a score related to the at least one sensing vector by the use of a polynomial function;

or

(ii) determining that the data fails to indicate a plurality of likely cardiac events in relatively clear fashion; and

(y) if a score is generated in step (x), comparing the score to a threshold and,

(i) if the threshold is at least met, determining that an identified sensing vector is suitable for cardiac event detection;

or

(ii) if the threshold is not met, determining that one or more other sensing vectors is to be analyzed.

2. The method of claim 1, wherein, if it is determined that one or more other sensing vectors is to be analyzed, the method further comprises:

the implantable medical system capturing additional cardiac signal data using one or more other sensing vectors; and

repeating steps (x) and (y).

3. The method of claim 2, wherein if, after repeating steps (x) and (y) for a number of vectors, no threshold is met by a score, the method further comprises:

(a) if at least one score is generated, identifying a vector for which a highest score is generated as the best available sensing vector;

or

(b) if no scores are generated, requesting operator input to complete a sensing vector selection process.

4. The method of claim 3, wherein steps (x), (y) and (a) are performed by the implantable medical device, and step (b) is performed using the programmer.

5. The method of claim 3, wherein steps (x), (y), (a) and (b) are performed by the programmer.

6. The method of claim 1, wherein:

the polynomial function includes first and second polynomials and takes into account a sensed amplitude of the cardiac signal and a sensed amplitude of noise; and

the polynomial function, when plotted against the sensed amplitude of cardiac signal, includes at least first and second peaks with a valley therebetween, the valley being associated with a limit of a dynamic range of an electrical component of the implantable medical device.

7. The method of claim 1, wherein the polynomial is a sixth order non-continuous polynomial making use of a sensed amplitude of a cardiac signal.

8. An implantable medical device comprising a canister housing operational circuitry and at least first, second, and third electrodes useable by the operational circuitry for sensing cardiac activity when implanted in a patient, the operational circuitry being configured to perform cardiac signal analysis by the use of a selected sensing vector, wherein the operational circuitry is further configured to select a sensing vector from among at least first, second and third sensing vectors defined by the first, second and third electrodes by a vector selection method comprising:

capturing cardiac signal data using at least one of the sensing vectors;

(x) analyzing data related to the captured cardiac signal data and;

(i) determining the data indicates a plurality of likely cardiac events in relatively clear fashion and, if so, generating a score related to the at least one sensing vector by the use of a polynomial function;

or

(ii) determining that the data fails indicate a plurality of likely cardiac events in relatively clear fashion; and

(y) if a score is generated in step (x), comparing the score to a threshold and,

(i) if the threshold is at least met, determining that an identified sensing vector is suitable for cardiac event detection;

or

(ii) if the threshold is not met, determining that one or more other sensing vectors is to be analyzed.

9. The device of claim 8, wherein the operational circuitry is further configured such that, if it is determined that one or more other sensing vectors is to be analyzed, the vector selection method further comprises:

capturing additional cardiac signal data using one or more other sensing vectors; and

repeating steps (x) and (y).

10. The device of claim 9, wherein the operational circuitry is further configured such that, if, after repeating steps (x) and (y) for a number of vectors, no threshold is met by a score, the vector selection method further comprises:

(a) if at least one score is generated, identifying a vector for which a highest score is generated as the best available sensing vector;

or

(b) if no scores are generated, requesting operator input to complete a sensing vector selection process.

11. The device of claim 8, further comprising telemetry circuitry configured for communication with a programmer, wherein the operational circuitry is configured to perform the vector selection method in response to prompting by the programmer.

12. The device of claim 8, wherein the operational circuitry is configured to perform the vector selection method periodically.

13. The device of claim 8, wherein the operational circuitry is configured to perform the vector selection method occasionally if occasions of sensing error or cardiac event detection error occur.

14. The device of claim 8, wherein the operational circuitry is further configured such that:

the polynomial function includes first and second polynomials and takes into account a sensed amplitude of the cardiac signal and a sensed amplitude of noise; and

the polynomial function, when plotted against the sensed amplitude of cardiac signal, includes at least first and second peaks with a valley therebetween, the valley being associated with a limit of a dynamic range of a device making up part of the operational circuitry.

15. The device of claim 8, wherein the operational circuitry is further configured such that the polynomial function includes a sixth order non-continuous polynomial making use of a sensed amplitude of a cardiac signal.

16. A system for implantable cardiac monitoring and stimulus comprising:

an implantable medical device including a canister housing operational circuitry, the operational circuitry including telemetry circuitry, the device further comprising at least first, second and third electrodes usable as sensing electrodes by the operational circuitry; and

a programmer configured to communicate with the telemetry circuitry of the implantable medical device;

wherein the system is configured to perform a vector selection method for selecting from among a plurality of sensing vectors defined between the first, second and third electrodes by a selection method comprising;

capturing cardiac signal data using at least one of the sensing vectors;

(x) analyzing data related to the captured cardiac signal data and;

(i) determining the data indicates a plurality of likely cardiac events in relatively clear fashion and, if so, generating a score related to the at least one sensing vector by the use of a polynomial function;

or

(ii) determining that the data fails to indicate a plurality of likely cardiac events in relatively clear fashion; and

(y) if a score is generated in step (x), comparing the score to a threshold and,

(i) if the threshold is at least met, determining that an identified sensing vector is suitable for cardiac event detection;

or

(ii) if the threshold is not met, determining that one or more other sensing vectors is to be analyzed.

17. The system of claim 16, wherein, if it is determined that one or more other sensing vectors is to be analyzed, the selection method further comprises:

capturing additional cardiac signal data using one or more other sensing vectors; and

repeating steps (x) and (y).

18. The system of claim 17, wherein if, after repeating steps (x) and (y) for a number of vectors, no threshold is met by a score, the selection method further comprises:

(a) if at least one score is generated, identifying a vector for which a highest score is generated as the best available sensing vector;

or

(b) if no scores are generated, requesting operator input to complete a sensing vector selection process.

19. The system of claim 18, wherein steps (x), (y) and (a) are performed by the implantable medical device, and step (b) is performed using the programmer.

20. The system of claim 18, wherein steps (x), (y), (a) and (b) are performed by the programmer.

21. A method of cardiac signal analysis in an implantable cardiac stimulus system having at least first and second sensing electrodes defining a first sensing vector therebetween, the method comprising:

selecting a detection threshold;

capturing a plurality of detected events in which an electrical signal sensed along the first sensing vector exceeds the detection threshold;

analyzing at least one metric related to a signal to noise ratio and amplitude for the plurality of detected events, the metric including a polynomial term related to the amplitudes for the plurality of detected events; and

determining whether the first sensing vector is;

suitable for cardiac event detection;

unsuitable for cardiac event detection;

or

available for cardiac event detection.

22. A method of cardiac signal analysis in an implantable cardiac stimulus system having a plurality of sensing electrodes that define a plurality of sensing vectors comprising, for each of a predetermined set of sensing vectors:

selecting a vector;

capturing a plurality of detected events using the selected sensing vector;

generating an amplitude metric for the plurality of detected events;

generating a signal-to-noise ratio (SNR) metric for the plurality of detected events;

subjecting the amplitude metric and the SNR metric to polynomial formula calculations, and combining results for the amplitude metric and/or the SNR metric to generate a SCORE for the selected vector;

then,

after generating SCOREs for a plurality of vectors, selecting one of the predetermined set of sensing vectors having a highest SCORE for use in cardiac event detection.

23. The method of claim 22, wherein the steps of generating an amplitude metric and generating an SNR metric include determining whether one or more of the plurality of detected events indicates ambiguity in identifying event peaks and, if so, setting an ambiguity flag for requesting input related to resolving the ambiguity.

24. The method of claim 22, wherein

the implantable cardiac stimulus system is configured for communication with a programmer adapted for use by an operator;

the step of subjecting the amplitude metric and the SNR metric to polynomial formula calculations and combining results includes identifying first and second possible SCOREs for any vector for which the ambiguity flag is set; and

the step of selecting one of the predetermined set of sensing vectors includes, if the highest SCORE is a possible SCORE for a vector having a set ambiguity flag, communicating with the operator using the programmer to resolve the ambiguity.