Abstract: An apparatus and method for tachyarrhythmia reversion provides a pacing pulse to the atrium at a predetermined time prior to the delivery of a cardioversion shock to the ventricle. The pacing pulse depolarizes the atrium producing an atrial refractory period., The cardioversion shock therapy is delivered during this refractory period in order to avoid the vulnerable zone of the atrium. This minimizes post-shock arrhythmias attributable to shock delivery during the atrial vulnerable zone. When used with bradycardia support pacing, a post-shock therapy pacing delay or pause is introduced, following reversion of the tachyarrhythmia, before delivering the bradycardia support pacing. The magnitude of the delay period is substantially greater than the normal bradycardia support pacing standby interval.