Substrate Versus Trigger Ablation for Paroxysmal Atrial Fibrillation

INCLUSION CRITERIA: * male or female \>21 years * reported incidence of at least two documented episodes of symptomatic paroxysmal atrial fibrillation (AF) during the three months preceding trial entry (at least 1 episode documented by 12-lead ECG or ECG rhythm strip) * women without childbearing potential or women of childbearing potential who are not pregnant per a serum HCG test * refractory to at least one Class I or III anti-arrhythmic medications. Drug doses must be therapeutic and stable * willingness, ability and commitment to participate in baseline and follow-up evaluations without participation in another clinical trial (unless documented approval received from both sponsors) * oral anticoagulation required for those subjects who have a score of two or more based on the following criteria (CHAD score): * Congestive heart failure (1 point) * hypertention (1 point) * age 75 years or older (2 points) * diabetes (1 point) * prior stroke or transient ischemic attack (2 points) * vascular disease (1 point) * age 65 years or older (1 point) * sex category: female (1 point) * patient is willing and able to remain on anti-coagulation therapy for a minimum of 3 months post procedure for all subjects, and potentially indefinitely post procedure if the patient has CHAD score \>or=2 * signed informed consent after a full discussion of the risks and benefits of both therapy arms, and the concept of randomization * NYHA Class 0,I, II stable on medical therapy for \> 3months * left atrial diameter \<or= 5.5cm * LVEF \>or=40% * sustained AF during the procedure EXCLUSION CRITERIA: * atrial fibrillation from a reversible cause (e.g., surgery, hyperthyroidism, pericarditis) * cardiac or thoracic surgery within the past 180 days * AF secondary to electrolyte imbalance, thyroid disease * contraindication to Heparin * Contraindication to Warfarin or other novel oral anticoagulants * history of significant bleeding abnormalities * history of significant blood clotting abnormalities, systemic thrombi or systemic embolization * ASD closure device, LAA closure device, prosthetic mitral or tricuspid valve * atrial clot/thrombus on imaging such as on a trans-esophageal echocardiogram (TEE) within 72 hours of the procedure * intramural thrombus or other cardiac mass that may adversely effect catheter introduction or manipulation * significant pulmonary embolus within 6 months of enrollment * acute illness or active systemic infection or sepsis that may ordinarily warrant postponement of the procedure * history of recent cerebrovascular disease (stroke or TIA) or systemic thromboembolism within \< 6 months * NYHA classes III, IV * heart failure that is not stable on medical therapy * pulmonary edema, that may make planned anesthesia or sedation difficult * stable/unstable angina or ongoing myocardial ischemia * myocardial infarction (MI) within the past three months * structural heart disease of clinical significance including: * congenital heart disease where the abnormality or its correction prohibit or increase the risk of ablation * acquired heart disease that may increase risk of ablation, such as significant ventricular septal defect post myocardial infarction * rheumatic valve disease, since this produces a unique AF phenotype * extreme left atrial enlargement (LA volume index \> 60 ml/m2) in whom PVI has low success and 55 mm baskets are too small for the atria * cardiac transplantation or other cardiac surgery planned within the 12 month followup period of the trial * life expectancy less than 12 months (the followup period of the trial) * significant pulmonary disease (e.g., COPD) or any other disease that significantly increase the risk to the patient from sedation or anesthesia * untreatable allergy to contrast media * at time of ablation procedure, clinically significant abnormalities in serum potassium, sodium, magnesium or other electrolytes that affect the suitability of the patient for ablation at that time