In most cases, AF originates where the pulmonary veins (PV) enter the left upper chamber of the heart, known as the left atrium (LA). Common to the procedure in each arm of the study is pulmonary vein isolation (PVI) or ablation of tissue around the pulmonary vein entrances. After PVI, the procedure continues with ablation in other areas of the LA where similar abnormal impulses are found. The three strategies for continuing with ablation after PVI are described in the "Arms" section below.
