Then, the two flexible components of the provided special introducer (Estech, San Ramon, USA) are gently passed through the oblique and transverse pericardial sinuses around the pulmonary veins, and pulled until their magnetic tips meet together. At this point, the Cobra Fusion^TM ablation probe (Estech) is connected to the introducer and advanced inside the chest to encircle the “box-lesion”. A useful manoeuvre to reveal indirectly any interference with the circumflex artery is verifying any haemodynamic or ECG- abnormalities after traction on the extremities of the probe. After correctness of position is confirmed, the Cobra Fusion^TM catheter is stabilized by suction to permit a temperature-controlled use of both monopolar and bipolar Radio-Frequency (RF) energy. Multiple ablations (60 sec at 70°C each) are performed, while circumferentially moving the catheter, to assure adequate overlapping of segments and closure of the “box-lesion”.