Association of ECs and the location with PVI success
The presence of an EC did not influence the success rate of first-pass
isolation (36/51, 70.6% in the EC-negative group vs. 14/23, 60.9% in
the EC-positive group, p=0.4321). However, in patients with an EC, the
relative locations of the EC site and the anterior isolation line of the
right-sided PV affected the success rate of first-pass isolation. The
relationship between the PVI line and the presence of ECs has not yet
been fully elucidated. Our results suggest that the PVI line should be
designed on the EC site (on-the-line) or closer to the PV than the EC
site (outside-line) for successful first-pass isolation in patients with
ECs.
As shown in Figure4B, the distance from the endocardium to the EC varied
according to the relative location between the EC attachment site and
ablation line. Therefore, the distance from the endocardium to the EC
may affect the success rate of first-pass isolation in patients with an
EC. Because the EC gets closer to the endocardium toward the right-sided
PV attachment site, it could be eliminated in the on-the-line group.
However, a longer distance from the endocardium to the EC might result
in failure to eliminate the EC. A longer distance might also cause
incomplete elimination and hinder the long-term success of PVI if the
procedure shows an acute effect. Hasebe et al. reported a similar case
of temporal elimination of an EC by ablation right-sided
PVI.13 If the PVI line was designed on the EC lesion,
the EC could have been eliminated, as was the case in our on-the-line
group. Previous reports have concluded that an EC cannot be eliminated
by circumferential ablation.5,6,12,13 However, the
results of the current study suggest that an EC can be eliminated by
intentionally designing an isolation line. Advances in mapping systems
have contributed to the precise detection and localization of ECs.
In this study, the distances from the EC site to the center of the
carina segment were not significantly different among the three groups
(on-the-line, inside-line, and outside-line), which suggests that the
PVI line can be designed on the EC site in many cases. However, in cases
where the EC site is very close to the carina, designing a PVI line on
the EC lesion is difficult, and the isolation area becomes too small. In
such cases, a strategy for designing a PVI line regardless of the EC
lesion and adding carina ablation may be considered.
In addition, in this study, we did not verify the earliest activation
site of the RA by PV or LA pacing and performed ablation from the RA
side. Barrio-Lopez et al. reported an insufficient success rate of
ablating the EC from the RA.7