Acute Effectiveness and Safety of the different mitral isthmus lines against Perimitral Flutter with Radiofrequency Ablation.

Background: Ablating perimitral flutter (PMF) is challenging mainly due to epicardial structures like the Bachmann bundle, coronary sinus (CS) system, and ligament of Marshall. There is still no consensus which ablation strategy is the most effective. This study evaluates the acute effectiveness and safety of three different 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 three MI line types implemented were the anteroseptal (ASML) to right superior pulmonary vein, the anterior (AML) to left superior pulmonary vein, and the lateral (LML) to left inferior pulmonary vein. In addition to endocardial ablation, when necessary, CS ablation and ethanol ablation of the vein of Marshall (VOM-ETOH) were employed.

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 combination of 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 lateral mitral line (LML) demonstrated a trend towards superior acute effectiveness compared to AML and ASML for PMF, especially with adjunctive epicardial ablation techniques without safety concerns. Accurate verification of bidirectional block and non-inducibility is critical.