 During the first weeks following pulmonary vein isolation PVI, it is not unusual for patients to experience early recurrences of atrial fibrillation or atrial tachycardia due to irritability from the ablation. While these arrhythmias tend to resolve over time, it is nevertheless standard practice to prescribe antiarrhythmic drugs for the first 2-3 months after the intervention to prevent these early recurrences. However, the efficacy of this practice has never been formally evaluated. In addition, we have identified a small group of patients whose atrial tachycardias have terminated after cessation of antiarrhythmic therapy, suggesting that proarrhythmia from these agents may promote reentrant tachycardias in some patients. We therefore designed a study protocol that will evaluate the usefulness of short term antiarrhythmic drug therapy in order to prevent atrial fibrillation and atrial tachycardia episodes during the first 6 weeks following PVI. 