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.