Techniques are provided for coordinating the delivery of cardioversion therapy and overdrive pacing therapy to the heart of a patient, primarily to prevent the re-occurrence of atrial fibrillation (AF) following a cardioversion shock. Included are techniques for modulating the aggressiveness of overdrive pacing by adjusting the magnitude of overdrive pulses or by changing the electrodes with which overdrive pacing pulses are generated. In one example, three phases or "tiers" of AF suppression therapy are provided: cardioversion therapy; far-field dynamic atrial overdrive (DAO) pacing; and near-field DAO pacing. Briefly, a cardioversion shock is delivered to the heart of the patient in response to the detection of AF, then smoothed, far-field overdrive pacing pulses are delivered using widely-spaced electrodes for a period of two minutes while the magnitude of the pulses is gradually reduced. Finally, near-field overdrive pacing pulses are delivered more or les continuously until another episode of AF is detected.