176-25: Catheter ablation of the superolateral mitral isthmus line

Abstract

Introduction: Perimitral flutter is a common left-atrial macro re-entrant tachycardia following catheter ablation of atrial fibrillation (AF). Commonly, a linear lesion is deployed at the mitral isthmus (MI) connecting the left inferior pulmonary vein ostium and the mitral annulus. Bidirectional conduction block may be challenging to achieve by endocardial ablation alone, regularly demanding additional epicardial ablation within the coronary sinus (CS). However, epicardial ablation bears an increasing risk for serious complications such as injury of the left circumflex artery or cardiac tamponade. The current study evaluates an alternate line design for the mitral isthmus, aiming to avoide the need for epicardial ablation. Methods: A total of 54 consecutive patients (14 women, age 61 ± 11 years) were included. All patients presented for catheter ablation of atrial fibrillation and/or left atrial tachycardia (MI dependent flutter in 28 patients). Electroanatomical reconstruction of the left atrium was performed, followed by angiographic visualization of the LAA. Subsequent endocardial ablation of the MI was performed under fluoroscopic guidance along the base of the LAA at the level of the superior MI, connecting the superior lateral pulmonary vein with the mitral annulus. Bidirectional conduction block was confirmed by mapping and pacing maneuvers. Results: Bidirectional conduction block was achieved by endocardial ablation alone in 51/54 (94,4%) patients. Additional endocardial ablation was required in 2/54 (3,7%). In 1/54 patients (1,8%) the MI could not be bidirectionally blocked, perimitral re-entry was terminated by an anterior line. Periprocedural pericardiac tamponade was observed in 3/54 (5,5%) patients, all of which were drained percutaneously without sequelae. A total of 14/54 (25,9%) patients underwent a reablation procedure demonstrating reconduction of the MI in 6 patients. Following index ablation of the MI coronary angiography was performed in 5 patients without pathological findings and no patient presented for clinical ischemia symptoms after ablation. Conclusion: The superolateral mitral isthmus line is associated with a high success rate of bidirectional block by endocardial ablation alone and bears minimal need for ablation from within the coronary sinus.