Prior studies
Several studies have reported an EC between the RPV carina and RA in patients undergoing PV isolation. However, the definition of EC is not standardized, and its assessment varies; it is sometimes performed during sinus rhythm before ablation6 or alternatively during atrial/PV pacing after ablation.7,8 Determining the presence or absence of epicardial breakthrough after ablation can make it difficult to distinguish residual LA–PV conduction from RA–PV epicardial breakthrough. Acute edema and enhancement on T2-weighted magnetic resonance imaging performed immediately after AF ablation correlate significantly with low-voltage areas (<0.05 mV) mapped using the CARTO system.20 Furthermore, acute post-ablation edema is observed not only in regions directly subjected to radiofrequency energy but also in distant regions. Consequently, even in the presence of residual conduction sites after circumferential ablation, early apparent potentials may not be recorded at or around the initial ablation line, and instead only at sites away from the initial lesion, such as the carina, which may mimic the distal attachment of EC. Electroanatomical mapping of LA breakthrough should be performed prior to ablation to avoid the influence of non-transmural ablation or edematous lesions. Two studies have described the disconnection of epicardial connection by ablation in the RA. In the present study, we attempted to ablate the RA end of epicardial fibres in two patients; however, cluster ablation of the RAPW did not achieve PV isolation. As indicated in Figure 6, the earliest area in the RA was extensive and may be difficult to ablate from the RA. Ablation of the carina may be essential for PV isolation.