Surgical VT Ablation
When VT ablation was failed despite endo/epi ablation, eligible patients would be rescheduled for surgical VT ablation. A quadripolar catheter was advanced into right ventricle for mapping reference and VT induction. Left limited thoracotomy would be the preferred access for surgical VT ablation. If the patient required other concomitant cardiac surgery, a median sternotomy would be performed instead. Three-dimensional electroanatomic mapping system (EnSite NavX, St. Jude Inc., St. Paul, MN, USA) was used to guide the procedure. The mapping strategy was similar to that of endocardial and epicardial approach. An irrigated ablation catheter (CoolFlex, St. Jude, Inc., St. Paul, MN, USA) with a flow rate of 30-60mL/min was used. Since the impedance recorded by the catheter tip was often higher than 200Ω due to its exposure to air, the upper limit of impedance should be reset to the maximum allowed by the RF generator. The tip of ablation catheter was manually pressed against the epicardial surface to maximize the contact force.