Comparison of the strategies
By determining the PVVJ, we found that half of the RVOT-type VAs were of supravalvular origin. The result is supported by previous studies using intracardiac echocardiography (ICE) and PA angiography.7,8 Therefore, it is essential to remind the importance of PVs in catheter ablation of RVOT-type VAs. They protect supravalvular origins when using the antegrade method and prevent engaging subvalvular origins when using the reversed U-curve method. Although the trial did not reach the enrollment goal and the ITT analysis showed no difference, the subgroup analysis had revealed the significant and qualitative interaction between the EVA sites and IA strategies. The subgroup effect cannot be explained by chance because of its substantial magnitude, statistical significance, consistency through subgroups, and electrophysiologic rationale.15 The result identified the EVA site as a critical baseline characteristic for selecting optimal IA strategy to achieve higher ablation effectiveness. The findings decreased the value of comparing the overall IA success rates between the strategies irrespective of the EVA sites. Since the contralateral IA was no longer in patients’ interests and a larger sample size would not add value to the ITT analysis, the ethnic committee and the leadership discontinued the study.