<qa>  What was the endpoint of AF termination?A total number of 100 patients with persistent AF were randomized to receive either conventional stepwise ablation conventional group or a sequential substrate ablation substrate group, both with the endpoint of AF termination. All patients were in AF before the procedure. The sequential substrate ablation consisted of pulmonary vein isolation PVI followed by cardioversion and linear ablation at the mitral isthmus, left atrial roof and cavotricuspid isthmus in order to modify the AF substrate. After achievement of bidirectional block, AF was re-induced and electrogram-based ablation was performed to achieve AF termination to sinus rhythm SR. Endpoints are single-procedure outcome and total amount of RF ablation time required to terminate AF by electrogram-guided ablation. 