Method for discriminating between ventricular and supraventricular arrhythmias
The present invention is directed toward a detection architecture for use in implantable cardiac rhythm devices. The detection architecture of the present invention provides methods and devices for discriminating between arrhythmias. Moreover, by exploiting the enhanced specificity in the origin of the identified arrhythmia, the detection architecture can better discriminate between rhythms appropriate for device therapy and those that are not.
1. An implantable cardiac device comprising a battery, operational circuitry coupled to the battery, and a housing for at least the operational circuitry, in which the operational circuitry includes input circuitry configured to couple to at least three electrodes to define a plurality of sensing vectors, wherein the operational circuitry is configured to analyze electrical signals in the plurality of sensing vectors as follows:
monitoring at least two sensing vectors to identify a signal-to-noise ratio (SNR) for each of the at least two sensing vectors;
calculating templates for each of the at least two sensing vectors;
on a cardiac complex-by-cardiac complex basis, selecting a best sensing vector as distinguished by SNR; and
using a corresponding template to assess whether a ventricular arrhythmia is occurring.
2. The device of claim 1 wherein the operational circuitry is configured to use, in addition to template analysis in the best sensing vector, a template analysis in a second sensing vector, to assist in determining whether a ventricular arrhythmia is occurring.
3. The device of claim 2 wherein the operational circuitry is further configured such that the template analysis in the best sensing vector uses a static template, and the template analysis in the second sensing vector uses a dynamic template formed from a preceding cardiac complex taken from the second sensing vector.
4. The device of claim 2 wherein the operational circuitry is configured to identify the second vector based on determining that it is generally orthogonal to the best sensing vector.
5. The device of claim 1 wherein the operational circuitry is configured to analyze a set of sensed cardiac complexes using the best sensing vector and calculate a set variance of correlation scores to assess whether a ventricular arrhythmia is occurring.
6. The device of claim 1 wherein the operational circuitry is configured to analyze both a correlation of a sensed cardiac complex to an immediately preceding cardiac complex captured with the best sensing vector, as well as a correlation of the sensed cardiac complex to a stored, static template.
7. The device of claim 1 wherein the operational circuitry is configured to assess a set of correlation results using the best sensing vector, calculate a variance thereof, and use the variance of the set of correlation results in assessing whether a ventricular arrhythmia is occurring.
8. An implantable cardiac system comprising a canister housing a battery and operational circuitry coupled to the battery, and a lead having at least three electrodes to define a plurality of sensing vectors, wherein the operational circuitry includes inputs for the at least three electrodes and is configured to analyze electrical signals in the plurality of sensing vectors as follows:
monitoring at least two sensing vectors to identify a signal-to-noise ratio (SNR) for cardiac complexes captured in each of the at least two sensing vectors;
calculating templates for each of the at least two sensing vectors;
on a cardiac complex-by-cardiac complex basis, selecting a best sensing vector as distinguished by SNR; and
performing a template analysis using a template corresponding to the best sensing vector to assess whether a ventricular arrhythmia is occurring.
9. The system of claim 8 wherein the operational circuitry is configured to use, in addition to template analysis in the best sensing vector, a template analysis in a second sensing vector, to assist in determining whether a ventricular arrhythmia is occurring.
10. The system of claim 9 wherein the operational circuitry is further configured such that the template analysis in the best sensing vector uses a static template, and the template analysis in the second sensing vector uses a dynamic template formed from a preceding cardiac complex taken from the second sensing vector.
11. The system of claim 9 wherein the operational circuitry is configured to identify the second vector based on determining that it is generally orthogonal to the best sensing vector.
12. The system of claim 8 wherein the operational circuitry is configured to analyze a set of sensed cardiac complexes using the best sensing vector and calculate a set variance of correlation scores to assess whether a ventricular arrhythmia is occurring.
13. The system of claim 8 wherein the operational circuitry is configured to analyze both a correlation of a sensed cardiac complex to an immediately preceding cardiac complex captured with the best sensing vector, as well as a correlation of the sensed cardiac complex to a stored, static template.
14. The system of claim 8 wherein the operational circuitry is configured to assess a set of correlation results using the best sensing vector, calculate a variance thereof, and use the variance of the set of correlation results in assessing whether a ventricular arrhythmia is occurring.
15. A method of operation in an implantable cardiac system comprising operational circuitry and at least three of electrodes coupled thereto, in which the operational circuitry includes input circuitry configured to couple to the at least three electrodes to define a plurality of sensing vectors, wherein the method comprises:
the operational circuitry monitoring at least two sensing vectors to identify a signal-to-noise ratio (SNR) for each of the at least two sensing vectors;
the operational circuitry calculating templates for each of the at least two sensing vectors;
on a cardiac complex-by-cardiac complex basis, the operational circuitry selecting a best sensing vector as distinguished by SNR; and
the operational circuitry performing a template analysis using a corresponding template for the best sensing vector to assess whether a ventricular arrhythmia is occurring.
16. The method of claim 15 further comprising the operational circuitry performing a template analysis in a second sensing vector using a template corresponding to the second sensing vector, to assist in determining whether a ventricular arrhythmia is occurring.
17. The method of claim 16 wherein:
the template analysis in the best sensing vector uses a static template; and
the template analysis in the second sensing vector uses a dynamic template formed from a preceding cardiac complex taken from the second sensing vector.
18. The method of claim 16 further comprising the operational circuitry selecting the second vector based on determining that it is generally orthogonal to the best sensing vector.
19. The method of claim 15 wherein the template analysis includes analysis of both of a correlation of a sensed cardiac complex to an immediately preceding cardiac complex captured with the best sensing vector, as well as a correlation of the sensed cardiac complex to a stored, static template.
20. The method of claim 15 further comprising the operational circuitry analyzing a set of correlation results using the best sensing vector, calculating a variance thereof, and using the variance of the set of correlation results in assessing whether a ventricular arrhythmia is occurring.