A randomized controlled study comparing pulmonary vein antrum isolation with and without the knowledge of the real-time contact force. In both groups, a catheter, which is able to measure contact force (SmartTouch, ThermoCool catheter, Biosense Webster) will be used. In the control group, the operator will be blinded to the measured contact-force. In all patients, the ablation will be guided by a circumferential mapping catheter (Lasso, Biosense Webster), CARTO 3 mapping system and ablation of adenosine-induced reconnection will be performed in all patients. Follow-up will be performed by continuous monitoring using an implantable loop recorder (Reveal XT, Medtronic Inc, Minneapolis, Minn)