Systems and methods for sensing vector selection in an implantable medical device using a polynomial approach

• US 7,783,340 B2
• Filed: 01/16/2007
• Issued: 08/24/2010
• 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
• Primary Examiner(s): Layno; Carl H
• Assistant Examiner(s): Stewart; Jennifer
• Application Number:
  US11/623,472
• Publication Number:
  US 20080172100A1
• Time in Patent Office: 1,316 Days
• Field of Search: 600/509, 600/512, 600/513, 600/515, 607/9, 607/14, 607/17, 607 27- 28
• US Class Current: 600/509
• 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 of selecting a default sensing vector for use with an implantable cardiac stimulus device system, the system comprising:

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 to establish a set of detections separated by intervals, the set of detections including a first detection in time and a series of detections occurring after the first detection;

(y) analyzing the set of detections by identifying the first detection in time as a QRS peak and, for the remaining detections performing the following until a predetermined number of QRS peaks are identified;

comparing an interval from a preceding detection to a threshold and, if the threshold is exceeded, identifying a detection as a QRS peak;

if not,

comparing the interval from the preceding detection to a prior interval and (i) if the interval and the prior interval are similar within a boundary condition, advancing to amplitude analysis;

if the prior interval is shorter outside the boundary condition, identifying a detection as a QRS peak;

or, if the prior interval is longer outside the boundary condition, identifying a detection as a Noise Peak; and

if consecutive detections are identified as QRS peaks, identifying a Noise peak therebetween;

if the step of comparing the intervals leads to amplitude analysis, performing the amplitude analysis by comparing the amplitudes of two detections to one another and binning the latter detection of the two detections according to whether it is approximately equal to, within predetermined bounds, larger than, or smaller than the earlier detection of the two detections; and

if all of the detections have been analyzed in the comparing the interval step and less than a predetermined number of QRS peaks have been identified, determining whether a threshold number of detections are in the approximately equal to bin and, if so, declaring a bad vector;

otherwise, further parsing the detections by amplitude into QRS peaks and noise peaks and calculating a vector score using each of the average amplitudes of identified QRS peaks and Noise peaks in a polynomial formula;

(z) if a score is generated in step (y), 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, or if a bad vector is declared, 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), (y) and (z).

3. The method of claim 2, wherein if, after repeating steps (x), (y) and (z) 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), (z) 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), (z), (a) and (b) are performed by the programmer.

6. The method of claim 1, wherein:

the polynomial formula, includes at least first and second peaks with a valley therebetween, the valley corresponding to a limit of a signal input dynamic range of an ECG amplifier of the implantable medical device.

7. The method of claim 1, wherein the polynomial formula is a sixth order non-continuous polynomial.

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 to establish a set of detections separated by intervals, the set of detections including a first detection in time and a number of detections occurring after the first detection;

(y) analyzing the set of detections by identifying the first detection in time as a QRS peak and, for the remaining detections performing the following until a predetermined number of QRS peaks are identified;

comparing an interval from a preceding detection to a threshold and, if the threshold is exceeded, identifying a detection as a QRS peak;

if not,

comparing the interval from the preceding detection to a prior interval and if the interval and the prior interval are similar within a boundary condition, advancing to amplitude analysis;

if the prior interval is shorter outside the boundary condition, identifying a detection as a QRS peak;

or, if the prior interval is longer outside the boundary condition, identifying a detection as a Noise Peak; and

if consecutive detections are identified as QRS peaks, identifying a Noise peak therebetween;

if comparing the intervals leads to amplitude analysis, performing the amplitude analysis by comparing the amplitudes of two detections to one another and binning the latter detection of the two detections according to whether it is approximately equal to, within predetermined bounds, larger than, or smaller than the earlier detection of the two detections; and

if all of the detections have been analyzed in the comparing the interval step and less than a predetermined number of QRS peaks have been identified, determining whether a threshold number of detections are in the approximately equal to bin and, if so, declaring a bad vector;

otherwise further parsing the detections by amplitude into QRS peaks and Noise peaks and calculating a vector score using each of the average amplitudes of identified QRS peaks and Noise peaks in a polynomial formula;

(z) if a score is generated in step (y), 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, or if a bad vector is declared, 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), (y) and (z).

10. The device of claim 9, wherein the operational circuitry is further configured such that, if, after repeating steps (x), (y) and (z) 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 formula includes first and second polynomials and includes at least first and second peaks with a valley therebetween, the valley corresponding to a limit of a signal input dynamic range of an ECG amplifier making up part of the operational circuitry.

15. The device of claim 8, wherein the operational circuitry is further configured such that the polynomial formula includes a sixth order non-continuous polynomial making use of an average Signal Amplitude for the series of detections.

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, the 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 to establish a set of detections separated by intervals, the set of detections including a first detection in time and a number of detections occurring after the first detection;

(y) analyzing the set of detections by identifying the first detection in time as a QRS peak and, for the remaining detections performing the following until a predetermined number of QRS peaks are identified;

comparing an interval from a preceding detection to a threshold and, if the threshold is exceeded, identifying a detection as a QRS peak;

if not,

comparing the interval from the preceding detection to a prior interval and if the interval and the prior interval are similar within a boundary condition, advancing to amplitude analysis;

if the prior interval is shorter outside the boundary condition, identifying a detection as a QRS peak;

or, if the prior interval is longer outside the boundary condition, identifying a detection as a Noise Peak; and

if consecutive detections are identified as QRS peaks, identifying a Noise peak therebetween;

if comparing the intervals leads to amplitude analysis, performing the amplitude analysis by comparing the amplitudes of two detections to one another and binning the latter detection of the two detections according to whether it is approximately equal to, within predetermined bounds, larger than, or smaller than the earlier detection of the two detections; and

if all of the detections have been analyzed in the comparing the interval step and less than a predetermined number of QRS peaks have been identified, determining whether a threshold number of detections are in the approximately equal to bin and, if so, declaring a bad vector;

otherwise further parsing the detections by amplitude into QRS Peaks and Noise peaks to calculate a vector score using each of the average amplitudes of identified QRS peaks and Noise peaks in a polynomial formula;

(z) if a score is generated in step (y), 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, or if a bad vector is declared, 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), (y) and (z).

18. The system of claim 17, wherein if, after repeating steps (x), (y) and (z) 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), (z) 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), (z), (a) and (b) are performed by the programmer.