Interventions: Patients will be randomized to either wide circumferential pulmonary vein isolation ("trigger") or ablation of high-frequency, fractionated electrograms during AF ("substrate"), or a hybrid approach combining trigger and substrate. Both techniques will be performed with NavX mapping system and a standardized ablation catheter. Endpoint of PVI will be isolation of all four PVs documented by circular catheter. Endpoint for substrate-based ablation will be termination and noninducibility of AF. Up to 2 procedures will be allowed within 6 months. A 2 month blanking period will be allowed after each procedure during which early recurrences will not be counted.