the Study of STABLE_SR for Persistent Atrial Fibrillation

* Background:the ablation outcomes for the treatment of persistent atrial fibrillation are not as satisfactory as paroxsymal AF. The successful rate ranges from 30%-55%. We found a new novel strategy for the modification of LA substrate during sinus rhythm based on our pilot study. * Hypothesis: our new method may be more effective than conventional strategy. * Objectives:The primary objective of this investigation is to compare the efficacy of two different AF ablation strategies in patients with persistent AF:Study Group: CPVI plus electrophysiologic substrate ablation in the left atrium during sinus rhythm ( STABLE-SR);Control Group: conventional stepwise approach for persistent AF(CPVI + Lines +CFE) .The secondary objectives of this investigation are to evaluate and compare the safety and procedural characteristics of both groups. * Sample size: 220 * Time line: 2013 Q1-2014 Q2