Endocardial ablation
Catheter ablation was performed 2 to 6 weeks after the surgical procedure. All patients received the procedure under general anesthesia and esophageal temperature monitoring with a dedicated tripolar catheter (Esotherm, Fiab). Heparin boluses were administered to achieve an activated coagulation time above 300 seconds. Mapping and ablation were performed using an electroanatomic mapping system (Carto, Biosense Webster, Diamond Bar, CA, USA). A detailed bipolar voltage map of the left atrium was obtained. All points were acquired point-by-point using the ablation catheter to ensure adequate catheter tissue contact by contact force (8-10g). Radiofrequency was applied using an open irrigated tip catheter with power output up to 35 W in the posterior wall and up to 45 W in the remaining atrial sites (Figure 2).
Entrance block was defined by complete elimination, or dissociation of pulmonary vein (PV) potentials, determined by the circular mapping catheter positioned in the pulmonary veins and posterior wall. Endocardial ablation was first directed to possible gaps in the surgical lesions. Finally, the procedure was completed with: a) ablation of the Marshall ligament; b) roof and anterior mitral lines; c) coronary sinus and superior vena cava isolation d) inter-caval ad cavo-tricuspid isthmus. After restoration of sinus rhythm, linear lesions were assessed for bi-directional block with further ablation performed as required to achieve block. High rate pacing, with a cycle length up to atrial effective refractory period for at least 10 seconds, was used to induce atrial arrhythmias and ablation of all the residual atrial arrhythmias was performed.