The purpose of this study is to determine the feasability of a new epicardial and minimal invasive ablation technique of the left atrium isolating the pulmonary veins for prevention of atrial fibrillation recurrences in patients with antiarrhythmic drug refractory lone atrial fibrillation.

Atrial fibrillation is a major health problem.Despite adequate treatment of underlying heart disease, rhythm control is unsuccessful in almost half of patients, also in patients with lone atrial fibrillation.If patients remain highly symptomatic, a non-pharmacological approach may be considered including pulmonary vein isolation and Cox maze III surgery. Maze III surgery has high succes rates, however it includes major cardiac surgery with substantial risk of complications. New surgical strategies for symptomatic lone atrial fibrillation focus on minimal invasive off-pump procedures omitting cardiopulmonary bypass (and thus lowering the complication rate), while taking advantage of an easier approach to the ablation site and a shorter procedure time. Epicardial surgical ablation isolating pulmonary veins by high intensity focused ultrasound performed off-pump by Video Assisted Thoracic Surgery (VATS)may be a promising treatment option. In this pilot study, we aim to study the feasibility of this new surgical ablation approach in patients with lone atrial fibrillation.

Inclusion Criteria:

1. Documented symptomatic lone paroxysmal or persistent atrial fibrillation, which either convert spontaneously or can be terminated with antiarrhythmic drugs or by an electrical cardioversion.
2. The patient had a least one episode of persistent atrial fibrillation or three episodes of paroxysmal atrial fibrillation during the last three months.
3. Duration present episode persistent atrial fibrillation less then one year.
4. The patient has been treated with at least two different antiarrhythmic drugs (class I-IV) of which at least one belongs to class I or III.
5. The patient will sign and date the written informed consent prior to study participation.

Exclusion Criteria:

1. Age <18 and >76 years.
2. Contraindications for oral anticoagulation.
3. Signs of sick sinus syndrome or AV conduction disturbances (i.e. symptomatic bradycardia or asystole > 3 seconds or escape rate < 40 beats per minute in awake symptom-free patients).
4. Permanent atrial fibrillation defined as atrial fibrillation continuously present and not convertible to sinus rhythm by an electrical cardioversion or antiarrhythmic drugs.
5. Previous transvenous pulmonary vein isolation, Maze surgery, or other cardiac surgery.
6. Heart failure defined as NYHA class III-IV heart failure.
7. Previously implanted intracardiac device or has current or foreseen pacemaker, internal cardioverter defibrillator (ICD) and/ or cardiac resynchronization therapy.
8. Clinically relevant valvular heart disease.
9. Coronary artery disease or an old myocardial infarction
10. Acute or chronic infection.
11. Untreated clinical hypo- or hyperthyroidism or < 3 months euthyroidism.
12. Uncontrolled hypertension, defined as a systolic blood pressure > 160 mm Hg and/or a diastolic blood pressure > 95 mm Hg (anti-hypertensive treatment is allowed).
13. The patient has a concurrent medical condition (i.e. alcohol or drug abuse or a severe progressive extracardiac disease) or is unlikely to comply with the protocol.