Clinical implication
One critical electrophysiologic principle is that ablation is more
likely to succeed at the target closer to the origin. The high IA
success rate by ipsilateral IA indicated the close relationship of the
EVA sites and origins. Currently, no ECG characteristics could
distinguish RVOT-type VAs with supravalvular origins from those with
subvalvular origins.9,10,16 The widely accepted
stepwise strategy is that after one method fails, then consider the
other. However, considering the high proportion of supravalvular origins
in RVOT-type VAs, activation mapping by single method is not sufficient
to reveal the actual EVA sites. One common cause of ablation failure is
that the target is not close enough to the origin. A subset of VAs
originating from the PSC junction was reported refractory to the
reversed U-curve method.17 When using the antegrade
method, the earliest activation time beneath PV was 13.2±4.2ms earlier,
indicating subvalvular origins. For this reason, the antegrade method
had better performance. We defined the VA suppression by contralateral
ablation as collateral damage. More ablation applications, prolonged
ablation, and higher power were usually needed to achieve
success.7 The collateral damage pattern of ablation
may impair the outcomes and increase the risk of complication. Our
findings suggested complete activation mapping for locating VA origins,
then selecting the optimal method to ipsilateral ablation for higher
effectiveness.