Acute effectiveness and safety of the different mitral isthmus lines in the treatment of perimitral flutter with radiofrequency ablation

OBJECTIVE: Ablating perimitral flutter (PMF) is challenging mainly because of epicardial structures such as the Bachmann bundle, the coronary sinus (CS) system, and the ligament of Marshall. There is still no consensus on which ablation strategy is the most effective. This study evaluates the acute effectiveness and safety of 3 different mitral isthmus (MI) ablation line types in treating PMF with radiofrequency ablation. METHODS: This retrospective analysis reviewed 102 cases of definitively diagnosed PMF from 5131 electrophysiological procedures performed between January 2018 and April 2024 in our center. The 3 MI line types implemented were the anteroseptal line (ASML) from the mitral valve annulus to the right superior pulmonary vein, the anterior line (AML) from the mitral valve annulus to the left superior pulmonary vein, and the lateral (or posterior) line (LML) from the lateral mitral valve annulus to the left inferior pulmonary vein. In addition to endocardial ablation, when necessary, CS ablation and ethanol ablation of the vein of Marshall (VOM-ETOH) were used. RESULTS: The LML had the highest block success rate (23/29 cases, 79.3%), followed by AML (41/64 cases, 64%) and ASML (19/33 cases, 57.6%). The overall acute block rate reached 81.4%, due to the combined use of multiple MI lines. In 16 cases (55.2% of LML), epicardial ablation in the CS system was performed. Use of VOM-ETOH with lateral lines increased success rates to 87.5%. Complications were rare, with one cardiac tamponade and one vascular complication. CONCLUSION: The LML demonstrated a trend toward superior acute effectiveness compared with AMLs and ASMLs for PMF, especially with adjunctive epicardial ablation techniques, without safety concerns. Accurate verification of bidirectional block and non-inducibility is critical.