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.