Pulmonary Vein Isolation Alone or in Combination With Substrate Modulation After Electric Cardioversion Failure

This study is comparing two types of ablation (a procedure that uses energy to destroy heart tissue) for people with persistent atrial fibrillation (an irregular heartbeat that has lasted more than 7 days). One approach targets just the pulmonary veins; the other also targets additional abnormal areas in the heart. **You may be eligible if...** - You are between 18 and 80 years old - You have persistent atrial fibrillation that has lasted at least 7 days without stopping - Your irregular heartbeat is causing symptoms and has not responded to at least one anti-arrhythmic drug (including amiodarone) - You have recently had an electrical cardioversion procedure (or are about to have ablation planned) - Your life expectancy is greater than 5 years **You may NOT be eligible if...** - You have severe heart valve disease, severe heart failure, or other serious heart conditions - A blood clot is found in your heart before the procedure - You have had a prior ablation procedure for atrial fibrillation - You are pregnant Talk to your doctor to see if this trial is right for you.