Implantable medical devices and programmers adapted for sensing vector selection

• US 7,623,909 B2
• Filed: 05/26/2006
• Issued: 11/24/2009
• 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): Behringer; Luther G
• Application Number:
  US11/441,516
• Publication Number:
  US 20070276447A1
• Time in Patent Office: 1,278 Days
• Field of Search: 600/518, 607/9, 607/27, 607/32, 607/4, 607/17, 607/28
• US Class Current: 600/509
• 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 method of directing operation of an implantable cardiac stimulus system, the system comprising an implantable device having operational circuitry coupled to a plurality of sensing electrodes disposed within a patient and defining a plurality of sensing vectors for performing cardiac event detection, the system further comprising a programmer adapted for communication with the implantable device, the method comprising:

the programmer directing data capture by the implantable device using at least one of the plurality of sensing vectors; and

the programmer analyzing at least one of the plurality of sensing vectors to determine suitability for cardiac event detection by use of the following method;

the programmer receiving captured signal data from the implanted device;

the programmer defining a fixed detection floor and a refractory period, the fixed detection floor being established as a fraction of an estimated maximum detection floor that the signals captured using a given sensing vector do not cross;

the programmer identifying a series of detected events that cross the fixed detection floor outside of refractory periods, wherein a refractory period starts each time a detected event is identified;

the programmer observing whether intervals between consecutive detected events are greater than a predetermined interval threshold and, if so, identifying a peak during a refractory period following a detection as a QRS Peak, and a peak during a fixed time period following the refractory period as a Noise Peak;

else

the programmer performing analysis to determine whether individual detected events are likely QRS or Noise events;

and either;

a) determining that a sensing vector is suitable for cardiac event detection;

or

b) determining that operator input is needed to complete a sensing vector selection process based on an inability of the programmer to parse individual detected events into likely QRS or Noise events; and

following a determination that a sensing vector is suitable or following operator input to complete a sensing vector selection process, the programmer directing communication to the implantable device instructing the implantable device to perform cardiac signal analysis using a selected sensing vector as a default vector.

2. The method of claim 1, wherein the operator input is an indication of whether a T-wave component or a QRS-complex component of a cardiac signal, each captured using the same sensing vector, has a greater amplitude.

3. The method of claim 1, wherein if none of a set of at least two sensing vectors is determined to be suitable for cardiac event detection, the method includes requesting operator input using the programmer.

4. The method of claim 1, wherein:

the step of analyzing at least one of a plurality of the sensing vectors includes calculating a score related to the quality of detection available for a sensing vector; and

the step of determining that an identified sensing vector is suitable for cardiac event detection includes comparing the score for the selected sensing vector to a threshold.

5. The method of claim 1, wherein:

the step of analyzing at least one of a plurality of the sensing vectors includes calculating a score related to the quality of detection available for a sensing vector; and

the step of determining that an identified sensing vector is suitable for cardiac event detection includes selecting the sensing vector having the highest score.

6. The method of claim 1, wherein the step of analyzing at least one of a plurality of the sensing vectors includes attempting to calculate a score related to the quality of detection available for at least two of the sensing vectors, failing to calculate the score for at least one sensing vector due to uncertainty, establishing possible outcomes for the score given possible resolutions of the uncertainty, and setting a flag for the at least one sensing vector for which the score was not calculated.

7. The method of claim 6, wherein:

the step of determining that an identified sensing vector is suitable for cardiac event detection includes;

determining that a calculated score exceeds a predetermined threshold and selecting a corresponding sensing vector;

or

determining that a calculated score exceeds all other scores and possible outcomes and selecting a corresponding sensing vector; and

the step of determining that operator input is needed includes determining that a possible outcome exceeds all other possible outcomes and calculated scores.

8. The method of claim 1, wherein the programmer directs the implantable device to capture data and perform one or more steps of amplifying, filtering, and/or digitizing the captured data.

9. The method of claim 1, wherein:

the implantable device is adapted to capture detections by comparison of a signal sensed using a sensing vector to a threshold;

the programmer directs the implantable device to capture a set of detections using a sensing vector; and

the programmer directs the implantable device to send data related to the set of detections to the programmer for use in the step of analyzing at least one of the plurality of sensing vectors.

10. The method of claim 1 further comprising:

the implantable device analyzing cardiac signals using the default sensing vector to determine whether a malignant condition is occurring; and

if so, the implantable device delivering therapy to a recipient of the implantable device.

11. A method of operating an implantable cardiac stimulus system, the system comprising an implantable device having operational circuitry coupled to a plurality of sensing electrodes disposed within a patient and defining a plurality of sensing vectors for performing cardiac event detection, the system further comprising a programmer adapted for communication with the implantable device, the method comprising:

executing instructions with the programmer to analyze at least first and second sensing vectors defined between selected subsets of the plurality of sensing electrodes by instructing the implantable device to perform data capture and transmission related to the at least first and second sensing vectors, the instructions adapted to generate either a score related to characteristics of a signal sensed along a selected sensing vector, or at least two possible scores and an indication of uncertainty relative to the possible scores the instructions configured such that the first and second sensing vectors are analyzed by a method of vector suitability analysis comprising;

the programmer receiving captured signal data from the implanted device;

the programmer defining a fixed detection floor and a refractory period, the fixed detection floor being established as a fraction of an estimated maximum detection floor that the signals captured using a given sensing vector do not cross;

the programmer identifying a series of detected events that cross the fixed detection floor outside of refractory periods, wherein a refractory period starts each time a detected event is identified;

the programmer observing whether intervals between consecutive detected events are greater than a predetermined interval threshold and, if so, identifying a peak during a refractory period following a detection as a QRS Peak, and a peak during a fixed time period following the refractory period as a Noise Peak;

else

the programmer performing analysis to determine whether individual detected events are likely QRS or Noise events;

and;

if no indications of uncertainty are generated, selecting whichever sensing vector has a highest score for use in detecting cardiac events;

or

if at least one indication of uncertainty is generated;

if a score exceeds other scores and all possible scores, selecting a corresponding sensing vector for use in detecting cardiac events without resolving uncertainty related to at least one possible score that does not exceed the identified score;

if an identified possible score exceeds all scores and other possible scores, requesting input from an operator to settle the uncertainty related to the possible score and, if the operator input resolves the uncertainty in favor of the identified possible score, selecting a corresponding sensing vector for use in detecting cardiac events.

12. The method of claim 11, wherein the step of requesting input from an operator includes asking the operator to determine whether the peak amplitude of a sensed QRS complex is greater than the peak amplitude of a sensed T-wave.

13. The method of claim 11, wherein the step of requesting input from an operator includes asking the operator to determine whether the peak amplitude of a sensed QRS complex is greater than the peak amplitude of a sensed noise signal.

14. The method of claim 11, wherein the step of requesting input from an operator includes asking the operator to determine whether a highest peak in a sensed signal is an R-wave peak.

15. The method of claim 11 further comprising:

the programmer transmitting instructions to the implantable device to indicate a default sensing vector for the implantable device based on results of the vector suitability analysis; and

the implantable device analyzing cardiac signals using the default sensing vector to determine whether a malignant condition is occurring and, if so, the implantable device delivering therapy to a recipient of the implantable device.

16. A method of operating an implantable cardiac stimulus system, the system comprising an implantable device having operational circuitry coupled to a plurality of sensing electrodes disposed within a patient and defining a plurality of sensing vectors for performing cardiac event detection, the system further comprising a programmer adapted for communication with the implantable device, the method comprising:

executing vectoring instructions with the programmer to analyze a first sensing vector defined between a selected subset of the plurality of sensing electrodes by at least instructing the implantable device to perform data capture and transmission related to the first sensing vector, wherein the vectoring instructions are adapted to generate either a score related to characteristics of a signal sensed along a selected sensing vector, or at least two possible scores and an indication of uncertainty relative to the possible scores, the vectoring instructions including a method of vector suitability analysis comprising;

the programmer receiving captured signal data from the implanted device;

the programmer defining a fixed detection floor and a refractory period, the fixed detection floor being established as a fraction of an estimated maximum detection floor that the signals captured using a given sensing vector do not cross;

the programmer identifying a series of detected events that cross the fixed detection floor outside of refractory periods, wherein a refractory period starts each time a detected event is identified;

the programmer observing whether intervals between consecutive detected events are greater than a predetermined interval threshold and, if so, identifying a peak during a refractory period following a detection as a QRS Peak, and a peak during a fixed time period following the refractory period as a Noise Peak;

else

the programmer performing analysis to determine whether individual detected events are likely QRS or Noise events;

if the analysis of the first sensing vector generates a first score, comparing the first score to a first threshold and, if the first score exceeds the first threshold, selecting the first sensing vector for use in detecting cardiac events;

otherwise, executing the vectoring instructions with the programmer to analyze a second sensing vector defined between another selected subset of the plurality of sensing electrodes by at least instructing the implantable device to perform data capture and transmission related to the second sensing vector; and

if the analysis of the second sensing vector generates a second score, comparing the second score to a second threshold and, if the second score exceeds the second threshold, selecting the second sensing vector for use in detecting cardiac events.

17. The method of claim 16, wherein the second sensing vector is not analyzed if the first score exceeds the first threshold.

18. The method of claim 16, further comprising:

if;

the first score does not exceed the first threshold or a first score is not generated, and

the second score does not exceed the second threshold or a second score is not generated;

then,

executing the vectoring instructions with the programmer to analyze a third sensing vector defined between yet another selected subset of the plurality of sensing electrodes by at least instructing the implantable device to perform data capture and transmission related to the third sensing vector; and

if the analysis of the third sensing vector generates a third score, comparing the third score to a third threshold and, if the third score exceeds the third threshold, selecting the third sensing vector for use in detecting cardiac events.

19. The method of claim 18, wherein, if none of the first, second or third thresholds are exceeded, the method further comprises:

starting with a set of scores and/or possible scores generated by executing the vectoring instructions;

a) identifying a greatest available score from the scores and/or possible scores;

b) if the greatest available score is a score, selecting sensing vector corresponding to the score for use in detecting cardiac events;

c) if a greatest available score is a possible score, requesting input from an operator to determine whether the identified possible score should be treated as an actual score or discarded;

d) if the operator input indicates that the identified possible score should be treated as an actual score, selecting a sensing vector corresponding to the identified possible score for use in detecting cardiac events;

e) if the operator input indicates that the identified possible score should be discarded, removing the identified possible score from the set of scores and/or possible scores, treating an associated possible score as a score, and returning to step a).

20. The method of claim 16, wherein, if first and second scores are generated by executing the vectoring instructions on the first and second sensing vectors and neither score exceeds a corresponding threshold, the method further comprises determining whether the greater of the first and second scores exceeds a third threshold and, if so, selecting the greater of the first and second scores for use in detecting cardiac events.

21. The method of claim 16, wherein the scores and possible scores are generated by calculating a signal-to-noise ratio and observing a peak amplitude for a selected sensing vector.

22. The method of claim 21, wherein the scores and possible scores are generated by inserting the signal-to-noise ratio and observed peak amplitude into a formula.

23. The method of claim 21, wherein the scores and possible scores are generated by inserting the signal-to-noise ratio and observed peak amplitude into a look-up table.

24. The method of claim 16 further comprising:

the programmer transmitting instructions to the implantable device to indicate a default sensing vector for the implantable device based on results of the vector suitability analysis; and

the implantable device analyzing cardiac signals using the default sensing vector to determine whether a malignant condition is occurring and, if so, the implantable device delivering therapy to a recipient of the implantable device.

25. A method of operating an implantable cardiac stimulus system, the system comprising an implantable device having operational circuitry coupled to a plurality of sensing electrodes disposed within a patient and defining a plurality of sensing vectors for performing cardiac event detection, the system further comprising a programmer adapted for communication with the implantable device, the method comprising:

the programmer instructing the implantable device to perform at least data capture and transmission relative to a first sensing vector;

the programmer analyzing transmitted data related to the first sensing by a method of vector suitability analysis comprising;

the programmer receiving captured signal data from the implanted device;

the programmer defining a fixed detection floor and a refractory period, the fixed detection floor being established as a fraction of an estimated maximum detection floor that the signals captured using a given sensing vector do not cross;

the programmer identifying a series of detected events that cross the fixed detection floor outside of refractory periods, wherein a refractory period starts each time a detected event is identified;

the programmer observing whether intervals between consecutive detected events are greater than a predetermined interval threshold and, if so, identifying a peak during a refractory period following a detection as a QRS Peak, and a peak during a fixed time period following the refractory period as a Noise Peak;

else

the programmer performing analysis to determine whether individual detected events are likely QRS or Noise events;

and returning one of;

a) a score indicating the quality of a signal captured along the first sensing vector;

b) at least two possible scores indicating the quality of the signal captured along the first sensing vector wherein operator input is needed to determine which possible score is correct;

or

c) an indication that the sensing vector under review is unsuitable for cardiac signal sensing;

the programmer determining whether the first sensing vector receives a score indicating that the first sensing vector is well suited to cardiac signal detection and, if not,

the programmer instructing the implantable device to perform at least data capture and transmission relative to a second sensing vector; and

the programmer analyzing transmitted data related to the second sensing vector in similar fashion to the first sensing vector.

26. The method of claim 25, further comprising:

the programmer determining whether the second sensing vector receives a score indicating that the second sensing vector is well suited to cardiac signal detection and, if not,

the programmer identifying which of the returned scores or possible scores is highest and, if a possible score is highest, the programmer querying an operator for the device to determine whether the highest possible score is correct;

if so,

a corresponding sensing vector is selected for use in detecting cardiac activity;

else,

the programmer repeats the step of selecting which of the returned scores or possible scores is highest until a sensing vector is selected.

27. The method of claim 25 further comprising:

the programmer instructing the implantable device to use a default sensing vector based on the results of the vector suitability analysis; and

the implantable device analyzing cardiac signals using the default sensing vector to determine whether a malignant condition is occurring and, if so, the implantable device delivering therapy to a recipient of the implantable device.