Methods and devices involving automatic atrial blanking

1. A method comprising:

during a period of time comprising a plurality of cardiac cycles, acquiring data related to the timing of ventricular events and atrial detections;

processing the data as follows to determine if there is a time correlation between ventricular events and atrial detections:

for each of the plurality of cardiac cycles, measuring the time between a ventricular event and each atrial detection within the cardiac cycle;

based on the measured time, associating each atrial detection with one of a plurality of time windows;

for each window, incrementing an atrial-detection count when an atrial detection is associated with it and decrementing the atrial-detection count when a ventricular-event count reaches a predetermined number; and

comparing the atrial-detection count of each time window to a threshold and for each that satisfies the threshold, designating it a blanking window; and

defining a post-ventricular atrial refractory period comprising an absolute atrial refractory period and a segmented relative atrial refractory period, wherein the segmented relative atrial refractory period includes at least one blanking window.

2. The method of claim 1 wherein a ventricular event corresponds to one of a ventricular pacing stimulus (V-paced) and an intrinsic ventricular depolarization (R-wave) and an atrial detection corresponds to one of an intrinsic atrial depolarization (P wave), a far-field R wave and a far-field T wave.

3. The method of claim 1 further comprising implementing the post-ventricular atrial refractory period during subsequent cardiac cycles.

4. The method of claim 1 further comprising monitoring the ventricular rate during the period of time and processing the data only when the ventricular rate is at or below a maximum ventricular rate.

5. The method of claim 1 wherein acquiring occurs during relative atrial refractory periods.

6. The method of claim 1 wherein processing occurs during absolute atrial refractory periods.

7. The method of claim 1 wherein the count is determined on a beat-by-beat basis.

8. The method of claim 1 wherein the count is determined periodically after a plurality of cardiac cycles.

9. The method of claim 1 wherein the ventricular event may be either a paced ventricular event (V-pace) or an intrinsic ventricular event (R-wave) and separate counts are maintained for each respective ventricular event type.

10. The method of claim 9 wherein designated blanking windows for intrinsic ventricular events are based only on counts maintained for intrinsic ventricular events.

11. The method of claim 9 wherein designated blanking windows for paced ventricular events are based only on counts maintained for paced ventricular events.

12. The method of claim 9 wherein designated blanking windows for paced ventricular events are based on counts maintained for both paced ventricular events and intrinsic ventricular events.

13. The method of claim 1 wherein the ventricular-event count corresponds to a running count of ventricular events that is reset when the predetermined number is reached.

14. A cardiac device comprising:

a ventricular sense channel for sensing ventricular events;

an atrial sense channel for sensing atrial detections; and

a controller connected to the atrial sense channel and the ventricular sense channel and operative to:

during a period of time comprising a plurality of cardiac cycles, acquire data related to the timing of ventricular events and atrial detections;

process the data as follows to determine if there is a time correlation between ventricular events and atrial detections:

for each of the plurality of cardiac cycles, measure the time between a ventricular event and each atrial detection within the cardiac cycle;

based on the measured time, associate each atrial detection with one of a plurality of time windows;

for each window, increment an atrial-detection count when an atrial detection is associated with it and decrement the atrial-detection count when a ventricular-event count reaches a predetermined number; and

compare the atrial-detection count of each time window to a threshold and for each that satisfies the threshold, designating it a blanking window; and

define a post-ventricular atrial refractory period comprising an absolute atrial refractory period and a segmented relative atrial refractory period, wherein the segmented relative atrial refractory period includes at least one blanking window.