Norwegian Study of Persistent Atrial Fibrillation Treatment: Cryoballoon Versus Radiofrequency Catheter Ablation

Inclusion criteria: * Patients plan to undergo pulmonary vein isolation as the first procedure for symptomatic persistent atrial fibrillation (\>7 days) and longstanding persistent atrial fibrillation (\> 12 months, but ≤ 3 years) who are refractory to at least one class I or class III antiarrhythmic drug and required at least one electrical or pharmacologic cardioversion. * Subject is at least 18 and ≤ 75 years old. * Subject is able and willing to give informed consent. Exclusion criteria: * Subject has paroxysmal atrial fibrillation (\< 7days) or persistent atrial fibrillation with duration \> 3 years. * Subject has any previous left atrial ablation procedure or surgery, including pulmonary vein isolation. * Subject has presence of an intracavitary thrombus. * Subject has uncontrolled heart failure. * Subject has severe valvular disease. * Subject has the left atrial diameter \> 60 mm confirmed by echocardiography. * Subject has contraindications to systemic anticoagulation with heparin or oral anticoagulants. * Subject has known cryoglobulinaemia. * Subject has severe renal dysfunction. * Subject who is or may potentially be pregnant. * Subject has unstable angina pectoris. * Subject has history of previous myocardial infarction or percutaneous intervention during the last three months. * Subject has chronic obstructive pulmonary disease with detected pulmonary hypertension.