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