This study evaluates the efficacy of high-density mapping guided atrial substrate ablation for persistent atrial fibrillation. 1/5 of the patients with persistent atrial fibrillation undergo pulmonary veins isolation, 2/5 of them pulmonary veins and box isolation while others undergo atrial substrate ablation apart from pulmonary veins and box isolation.

Inclusion Criteria:

• Informed consent signed.
• Age of 18 to 75 years old.
• Persistent or longstanding persistent atrial fibrillation (≥7 days), which is confirmed by Holter in recent six months.
• Willing to have catheter ablation for atrial fibrillation.

Exclusion Criteria:

• Accompanied by serious heart diseases including cardiac valvular diseases, congenital heart diseases, hypertrophic obstructive cardiomyopathy, acute myocardium infarction, unstable anginal pectoris and so on.
• Complete atrioventricular block.
• An acute stroke or contradiction of anti-coagulation.
• Hyperthyroidism.
• Having a history of catheter ablation of atrial fibrillation.
• Left atrial appendage thrombosis confirmed by transesophageal echocardiography.
• Pregnancy or lactation.
• Planning for pregnancy in the near future.
• Myopathy or active liver disease, including patients with sustained increase of serum transaminase of unknown reason and the ones with increased serum transaminase over three times the upper limit of normal.
• Patients of severe renal insufficiency with creatinine clearance lower than 30 ml/min.