Methods and devices implementing dual criteria for arrhythmia detection
Methods and devices providing multiple criteria for use in arrhythmia identification. Based on inputs including defined rules or parameters, one of a more conservative or more aggressive set of arrhythmia identification parameters can be selected. One or the other of the selectable sets of arrhythmia identification parameters may also be adaptive or modifiable during the use of the system, for example, in response to identified nonsustained episodes, the more conservative set of arrhythmia identification parameters can be modified to become still more conservative. Such modification of arrhythmia identification criteria allows reduced time to therapy when indicated, while allowing more deliberate decisions in other circumstances.
1. An implantable cardiac stimulus device comprising electrodes coupled to operational circuitry for sensing cardiac activity and detecting events in the sensed cardiac activity and delivering therapy in response to identified conditions, in which the operational circuitry is configured to use one or more arrhythmia identification parameters which can be modified within predefined ranges, wherein the operational circuitry is configured to:
establish a preliminary identification of a potentially treatable arrhythmia using a set of detected events;
determine whether the set of detected events are varying in shape or consistent in shape using a predefined parameter;
if the set of detected events is varying in shape, apply a first value for the arrhythmia detection parameter to assess whether the preliminary identification of a potentially treatable arrhythmia should be declared as an episode of treatable arrhythmia; and
if the set of detected events is not varying in shape, apply a second value for the arrhythmia detection parameter to assess whether the preliminary identification of a potentially treatable arrhythmia should be declared as an episode of treatable arrhythmia;
wherein the second value is different from the first value; and
wherein the operational circuitry is further configured to: identify a nonsustained episode of potentially treatable arrhythmia and, in response thereto, modify the second value for the arrhythmia detection parameter, and set the first value for the arrhythmia detection parameter to a predefined default value for the modified arrhythmia detection parameter.
2. An implantable cardiac stimulus device comprising electrodes coupled to operational circuitry for sensing cardiac activity and detecting events in the cardiac activity, the operational circuitry further being configured to deliver therapy in response to identified conditions, wherein the operational circuitry is configured to:
observe features of the cardiac signal for a set of detected events and use the observed features to select from at least:
a) a first set of arrhythmia declaration parameters; and
b) a second set of arrhythmia declaration parameters; and
use the selected set of arrhythmia detection parameters to analyze the sensed cardiac activity;
wherein the first set of arrhythmia declaration parameters is different from the second set of arrhythmia declaration parameters such that, for at least a set of detected data, analysis using the first set of arrhythmia declaration parameters would not declare a treatable arrhythmia while analysis using the second set of arrhythmia declaration parameters would declare at treatable arrhythmia; and
wherein the operational circuitry is configured to observe features of the cardiac signal for the set of detected events by determining whether a monomorphic cardiac signal is occurring.
3. The implantable cardiac stimulus device of claim 2 wherein the operational circuitry is configured to observe features of the cardiac signal for the set of detected events to select from at least the first and second sets of arrhythmia declaration parameters excludes observation of cardiac rate information.
4. The implantable cardiac stimulus device of claim 2 wherein the operational circuitry is configured to select the first set of arrhythmia declaration parameters in response to determining that a monomorphic cardiac signal is occurring.
5. The implantable cardiac stimulus device of claim 2 wherein the operational circuitry is configured to select the second set of arrhythmia declaration parameters in response to determining that a monomorphic cardiac signal is not occurring.
6. The implantable cardiac stimulus device of claim 2 wherein:
the operational circuitry is further configured to analyze individual detected events in order to identify whether any detections occur due to noise; and
the operational circuitry is further configured to observe features of the cardiac signal for the set of detected events by determining whether one or more detections have been identified as noise.
7. The implantable cardiac stimulus device of claim 6 wherein the operational circuitry is configured to select the first set of arrhythmia declaration parameters in response to determining that one or more detections have been identified as noise.
8. The implantable cardiac stimulus device of claim 6 wherein the operational circuitry is configured to select the second set of arrhythmia declaration parameters in response to determining that no detections have been identified as noise.
9. The implantable cardiac stimulus device of claim 2 wherein:
the operational circuitry is further configured to analyze individual detected events in order to identify whether any detections occur due to overdetection; and
the operational circuitry is configured to observe features of the cardiac signal for the set of detected events by determining whether one or more detections have been identified as being overdetections.
10. The implantable cardiac stimulus device of claim 9 wherein the operational circuitry is configured to select the first set of arrhythmia declaration parameters in response to determining that one or more detections have been identified as overdetections.
11. The implantable cardiac stimulus device of claim 9 wherein the operational circuitry is configured to select the second set of arrhythmia declaration parameters in response to determining that no detections have been identified as overdetections.
12. The implantable cardiac stimulus device of claim 2 wherein the operational circuitry is configured to observe features of the cardiac signal for the set of detected events by determining whether a sudden onset of increased cardiac rate has occurred.
13. The implantable cardiac stimulus device of claim 12 wherein the operational circuitry is configured to select the first set of arrhythmia declaration parameters in response to determining that no sudden onset of increased cardiac rate has occurred.
14. The implantable cardiac stimulus device of claim 12 wherein the operational circuitry is configured to select the second set of arrhythmia declaration parameters in response to determining that a sudden onset of increased cardiac rate has occurred.
15. A method of cardiac signal analysis in an implantable cardiac device, the implantable cardiac device comprising electrodes coupled to operational circuitry for sensing cardiac activity and performing cardiac signal analysis, the method comprising:
observing features of the cardiac signal for a set of detected events and using the observed features to select from:
a) a first set of arrhythmia declaration parameters; and
b) a second set of arrhythmia declaration parameters; and
using the selected set of arrhythmia declaration parameters to analyze the sensed cardiac activity;
wherein the first set of arrhythmia declaration parameters is different from the second set of arrhythmia declaration parameters such that, for at least a set of detected data, analysis using the first set of arrhythmia declaration parameters would not declare a treatable arrhythmia while analysis using the second set of arrhythmia declaration parameters would declare at treatable arrhythmia;
wherein the step of observing features of the cardiac signal for the set of detected events by determining whether a monomorphic cardiac signal is occurring.
16. The method of claim 15 wherein the step of observing features of the cardiac signal for the set of detected events to select from at least the first and second sets of arrhythmia declaration parameters excludes observation of cardiac rate information.
17. The method of claim 15 further comprising analyzing individual detected events in order to identify whether any detections occur due to noise; and
wherein the step of observing features of the cardiac signal for the set of detected events includes determining whether one or more detections have been identified as noise.
18. The method of claim 15 further comprising analyzing individual detected events in order to identify whether any detections occur due to overdetection; and
wherein the step of observing features of the cardiac signal for the set of detected events includes determining whether one or more detections have been identified as being overdetections.
19. The method of claim 15 wherein the step of observing features of the cardiac signal for the set of detected events includes determining whether a sudden onset of increased cardiac rate has occurred.