RF Ablation
The ablation strategy was adopted depending on the activation mapping result. Localized reentry aimed to find the isthmus region, which was always located between 2 anatomic barriers, consisting of either the natural MA or pulmonary vein (PV) or acquired ESAs or late diastolic potentials (LDPs) and showed fragmented potentials. All the ATs of localized reentry converted to another AT after fragmented potential ablation. Remapping of the new tachycardia showed that an isthmus, which had been a bystander in the previous tachycardia, had become a critical part in the new circuit in 2 patients (Fig. 1C). The AMATs ablated the narrowest bridge of conducting tissue between scars or anatomical obstacles. The 4 perimitral flutter circuits were ablated by a line connecting the MA to the left superior PV (n=3) and the right superior PV (n=1). The peri-roof circuits were ablated by joining the PV to the contralateral superior PV across the LA roof (n=2). CTI was ablated in 2 patients due to the CTI-dependent AT in the first mapping. The FCB areas were never the target ablation site after mapping the mechanism of the ATs, but some of the suited ablation sites could be near the barrier formed by them (Fig. 2). No patients received further substrate-modified ablation in AT or sinus rhythm.