Patent ID: 7209785

Claim:
A method for delivering atrial defibrillation therapy, comprising: detecting an episode of atrial fibrillation or other atrial tachyarrhythmia; detecting ventricular depolarizations (R-waves) with a ventricular sensing channel, wherein R-waves are detected when a sensed ventricular electrogram value exceeds a dynamically varying threshold value, wherein the dynamically varying threshold value is set to a specified percentage of the peak absolute value of each detected R-wave and then decays to a specified minimum threshold; starting a shockable interval timer upon detection of an R-wave; detecting separate events in the ventricular sensing channel with a specified low shock threshold value and a specified high shock threshold value, wherein the low shock threshold value is lower than the dynamically varying threshold and the high shock threshold value is higher than the dynamically varying threshold; restarting the shockable interval timer if the sensed ventricular electrogram exceeds the low shock threshold value; and, delivering an atrial defibrillation shock pulse synchronously with a detected R-wave if the shockable interval timer has reached or exceeded a specified minimum value and if the sensed ventricular electrogram value exceeds the high shock threshold value.