Thoracoscopic Surgical Versus Catheter Ablation Approaches for Primary Treatment of Persistent Atrial Fibrillation

Inclusion Criteria: * Age is between 18 and 80 years * Persistent AF as defined following the ESC 2016 Guidelines, evidenced by 1) ongoing AF on the ECG or 2) documentation of AF necessitating cardioversion. * AF documented by ECG or Holter \< 1 year ago. * At least one class I or III anti-arrhythmic drug in standard dosage has failed or is not tolerated. * Left atrial volume index ≤ 45 ml/m2 * Legally competent and willing to sign the informed consent. * Willing and able to adhere to the follow-up visit protocol. * Life expectancy of at least 2 years. Exclusion Criteria: * Prior intervention (catheter ablation or minimally-invasive thoracoscopic ablation) for AF. * AF is secondary to electrolyte imbalance, thyroid disease or other reversible or non-cardiovascular causes. * Documentation of CTI dependent atrial flutter * Valvular AF * Paroxysmal AF * Long standing Persistent AF, defined as AF continuously present for longer than 1 year. * Body mass index \>35kg/m2 * NYHA class IV heart failure symptoms or left ventricular ejection fraction \<35%. * NYHA class III heart failure symptoms, unless caused or aggravated by AF. * Myocardial infarction within the preceding 2 months. * Active infection or sepsis (as evidenced by increased white blood cell count, elevated CRP level or fever \>38,5 °C). * Known and documented carotid stenosis \> 80% * Planned cardiac surgery for other purposes than AF. * Pregnancy or child bearing potential without adequate anticonception. * Requirement of anti-arrhythmic drugs for ventricular arrhythmias. * Presence of intracardiac mass or thrombus (discovery of any thrombus or intracardiac mass after signing of the informed consent will result in withdrawal of the subject from the study) * Co-morbid condition that possesses undue risk of general anesthesia or port access cardiac surgery (in the opinion of the operator). * History of previous radiation therapy on the thorax * Circumstances that prevent follow-up * No vascular access for catheterization. * History of previous thoracotomy. * Factors precluding transseptal puncture for catheterization.