Right Atrial Dimension Is Related to Bidirectional Block Parameters After Cavotricuspid Isthmus Ablation in Patients with Typical Atrial Flutter

Background: There is insufficient data in the literature regarding the relationship between bidirectional conduction block (BCB) parameters and right atrial dimension (RAd). In our study, we aimed to evaluate the relationship between RAd and BCB parameters in typical atrial flutter (AFL) patients. Methods: This prospective study included 197 patients who underwent successful RFA with a diagnosis of typical AFL between 2020 and 2025. We performed RAd and BCB measurements in addition to routine assessments in all patients. The presence of BCB was confirmed by measurement of the CTI double-potential peak-to-peak interval (DPPPI) during CSp pacing, as well as by the difference between the conduction times from isthmus lateral-to-medial pacing to the CSp stimulus (ΔI-CS = LI-to-CSp − MI-to-CSp) and the difference between the conduction times from CSp pacing to the lateral and medial isthmus sites (ΔCS-I = CSp-to-LI − CSp-to-MI). Patients were divided into 3 groups according to RAd: Group-I: <2.2 cm/m2, Group-II: 2.2–2.4 cm/m2, and Group-III: >2.4 cm/m2. Results: The number of patients in Groups I, II, and III was determined to be 99, 55, and 43, respectively. RA-volume, LVEF, RAd, and LAd values, as well as LI-to-CSp, ΔI-CS, CSp-to-LI, ΔCS-I, and DPPPI durations, significantly increased from Group I to Group III. MI-to-CSp and CSp-to-MI durations also increased from Group I to Group III; being Group I was significantly lower than Groups II and III. When DPPPI durations were categorized as ≤110 ms, 110–119 ms, 120–129 ms, and ≥130 ms, a significant difference was observed among the groups, and all Group II–III cases were found to have a DPPPI duration of ≥120 ms. In Groups II and III, the proportions of patients with DPPPI ≥ 130 ms were 46% and 84%, respectively. Conclusions: Our study showed that cavotricuspid-isthmus BCB parameters, which are indicators of successful AFL ablation, are closely and significantly related to RAd.