Prevalence of the EC
Previous studies have reported an inconsistent prevalence of an EC
between right-sided PV and the RA in patients undergoing PVI: 18% by
Yoshida et al. and 51% by Hanaki et al.6,12 The prevalence of an EC in the current study fell
between that of those studies of Japanese patients, at 31%. In
contrast, Barrio-Lopez et al. reported a much lower prevalence
(6.8%).7 This may be due to differences in races and
the method of ECs verification. They confirmed the presence of ECs after
PV antrum ablation, which might have led to underestimation because of
the elimination of ECs. Contrary to their study, three other studies,
including the current study, evaluated ECs before PV antrum ablation
using the LA activation map.
As for the LA activation map, the mean number of LA mapping points in
the current study was much larger than that in the reports by Yoshida
and Hanaki (2532 vs. 679 vs. 1479, respectively). Further, those other
reports did not mention specific methods for visualizing the activation
pattern of LA in detail. We confirmed the existence of the EC before
ablation with Ripple mapping and Coherent mapping, which are useful for
atrial tachycardia and other reentrant tachycardia ablations as well as
for detecting the presence of ECs by visualizing activation patterns.
In accordance with previous reports, most EC sites were located anterior
to the carina segment of the right-sided PV. However, we must recognize
that the EC is composed of multiple myofibers.9 The EC
site was defined as the earliest activation site near the right-sided PV
except for Bachman bundle. However, the “EC site” in our study was
only the earliest conduction site on the PV side of the myofibers. In
previous anatomical studies, the muscle fibers were also widely attached
elsewhere in the craniocaudal direction and transverse to the epicardial
fat of the interatrial groove.9 In Figure4A, we depict
the figure of epicardial fiber connected between the RA and LA
speculated in a previous study. The attachment of epicardial fibers in
the LA might be a variable location that would influence PVI success.