We randomly assigned 589 patients with persistent atrial fibrillation in a 1:4:4 ratio to ablation with pulmonary-vein isolation alone ( 67 patients ) , pulmonary-vein isolation plus ablation of electrograms showing complex fractionated activity ( 263 patients ) , or pulmonary-vein isolation plus additional linear ablation across the left atrial roof and mitral valve isthmus ( 259 patients ) .