Epicardial Ablation Procedure
When endocardial VT ablation was unsuccessful, epicardial approach would be attempted using subxiphoid access. Mapping and ablation strategies were similar to the endocardial approach as described above. Coronary angiogram was performed in all the patients before ablation to avoid inadvertent damage of coronary artery. High output pacing was performed in the area close to the course of phrenic nerve before ablation to avoid phrenic nerve injury.