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 medical device (IMD) configured for monitoring a patient's cardiac rhythm to determine whether an arrhythmia is occurring, the IMD comprising:
a housing containing a battery and operational circuitry for the IMD;
at least first and second electrodes on the housing and coupled to the operational circuitry, the operational circuitry configured to use the first and second electrodes for sensing a cardiac signal of the patient;
wherein the operational circuitry is configured to detect a plurality of R-waves for the patient in a sensed cardiac signal from the electrodes and observe a measure of interval rate stability for the R-waves to determine whether the intervals are stable or unstable, relative to an interval rate stability threshold;
wherein the operational circuitry is configured to compare a selected R-wave from the plurality of R-waves to a dynamic template representing an immediately preceding R-wave to determine whether the dynamic template is matched by the selected R-wave; and
wherein the operational circuitry is configured to identify atrial fibrillation in response to finding that the intervals are unstable and the selected R-wave matches the dynamic template.
2. The IMD of claim 1 wherein the interval rate stability threshold defines the intervals as stable when the intervals are within plus or minus 30 milliseconds.
3. The IMD of claim 1 wherein the operational circuitry is configured to identify cardiac complexes associated with the detected R-waves, and further adapted to update the dynamic template after each sensed cardiac complex.
4. The IMD of claim 1 further comprising therapy circuitry in the housing for generating and delivering defibrillation therapy in response to ventricular arrhythmias, wherein the operational circuitry is configured to avoid delivery of therapy to atrial arrhythmias.
5. The IMD of claim 4 wherein the operational circuitry is further configured to identify ventricular arrhythmia by identifying a combination of a failure of the selected R-wave to match the dynamic template and failure of the selected R-wave to match a static template.
6. The IMD of claim 5 wherein the operational circuitry is further configured to deliver defibrillation therapy using the therapy circuitry in response to identifying ventricular arrhythmia.
7. The IMD of claim 4 wherein the operational circuitry is further configured to identify ventricular arrhythmia by identifying a combination of a failure of the selected R-wave to match the dynamic template and by determining that the selected R-wave has a width which exceeds a threshold.
8. The IMD of claim 7 wherein the operational circuitry is further configured to deliver defibrillation therapy using the therapy circuitry in response to identifying ventricular arrhythmia.
9. The IMD of claim 1 wherein the operational circuitry is further configured to identify ventricular arrhythmia by identifying a combination of a failure of the selected R-wave to match the dynamic template and failure of the selected R-wave to match a static template.
10. The IMD of claim 1 wherein the operational circuitry is further configured to identify ventricular arrhythmia by identifying a combination of a failure of the selected R-wave to match the dynamic template and by determining that the selected R-wave has a width which exceeds a threshold.
11. An implantable medical device (IMD) configured for monitoring a patient's cardiac rhythm to determine whether an arrhythmia is occurring, the IMD comprising:
a housing containing a battery and operational circuitry for the IMD;
at least first and second electrodes on the housing and coupled to the operational circuitry, the operational circuitry configured to use the first and second electrodes for sensing a cardiac signal of the patient;
wherein the operational circuitry is configured to detect a plurality of R-waves for the patient in a sensed cardiac signal from the electrodes and observe a measure of interval rate stability for the R-waves to determine whether the intervals are stable or unstable, relative to an interval rate stability threshold;
wherein the operational circuitry is configured to compare a selected R-wave from the plurality of R-waves to a static template representing a stored template of a sinus cardiac complex template to determine whether the static template is matched by the selected R-wave; and
wherein the operational circuitry is configured to identify atrial fibrillation in response to finding that the intervals are unstable and the selected R-wave matches the static template.
12. The IMD of claim 11 wherein the interval rate stability threshold defines the intervals as stable when the intervals are within plus or minus 30 milliseconds.
13. The IMD of claim 11 further comprising therapy circuitry in the housing for generating and delivering defibrillation therapy in response to ventricular arrhythmias, wherein the operational circuitry is configured to avoid delivery of therapy to atrial arrhythmias.
14. The IMD of claim 13 wherein the operational circuitry is further configured to identify ventricular arrhythmia by identifying a combination of a failure of the selected R-wave to match the static template and failure of the selected R-wave to match a dynamic template representing an immediately preceding R-wave.
15. The IMD of claim 14 wherein the operational circuitry is further configured to deliver defibrillation therapy using the therapy circuitry in response to identifying ventricular arrhythmia.
16. The IMD of claim 13 wherein the operational circuitry is further configured to identify ventricular arrhythmia by identifying a combination of a failure of the selected R-wave to match the static template and by determining that the selected R-wave has a width which exceeds a threshold.
17. The IMD of claim 16 wherein the operational circuitry is further configured to deliver defibrillation therapy using the therapy circuitry in response to identifying ventricular arrhythmia.
18. The IMD of claim 11 wherein the operational circuitry is further configured to identify ventricular arrhythmia by identifying a combination of a failure of the selected R-wave to match the static template and failure of the selected R-wave to match a dynamic template representing an immediately preceding R-wave.
19. The IMD of claim 11 wherein the operational circuitry is further configured to identify ventricular arrhythmia by identifying a combination of a failure of the selected R-wave to match the static template and by determining that the selected R-wave has a width which exceeds a threshold.