STAR-AF:Substrate Versus Trigger Ablation for Reduction of Atrial Fibrillation Trial

Inclusion Criteria: * Patients age 18 or greater. * "high burden" of paroxysmal atrial fibrillation or persistent atrial fibrillation * candidates for AF ablation based on AF that is symptomatic and refractory to at least one antiarrhythmic medication. * At least one episode of AF must have been documented by ECG or Holter within 12 months of randomization in the trial. * continuous anticoagulation with warfarin (INR 2-3) for \>4 weeks prior to the ablation. * Patients must be able and willing to provide written informed consent to participate in the clinical trial. Exclusion Criteria: * chronic atrial fibrillation. * Patients with AF felt to be secondary to an obvious reversible cause. * inadequate anticoagulation as defined in the inclusion criteria. * left atrial thrombus or spontaneous echo contrast on TEE prior to procedure. * contraindications to systemic anticoagulation with heparin or coumadin. * previously undergone atrial fibrillation ablation. * left atrial size \> 55 mm. * Patients who are or may potentially be pregnant