Mitral annular flutter: Review of mechanisms, challenges of ablation, and assessment of block

Author(s): Sumedh Iyengar, Sudeepthi Reddy Mekala, Komandoor Srivathsan

Mitral Annular Flutter (MAF) occurs with increased frequency after procedures such as atrial fibrillation ablation and mitral valve surgeries. Catheter ablation of the mitral annulus is challenging due to its complex anatomy. We wish to highlight the anatomical considerations, mechanisms of MAF, challenges during ablation, and assessment of bidirectional block. The mechanism of MAF mostly revolves around previous extensive ablation in the left atrium for AF or mitral valve surgeries such as the Maze procedure. The commonly used lines for MAF ablation are the Lateral Mitral Isthmus line (LMI) and Left Atrial Anterior wall (LAAW) line. LMI line often necessitates ablation within the Coronary Sinus, which can lead to additional complications. There is also variable myocardial thickness in this region, increasing the difficulty. LAAW line ablation can lead to complications like left circumflex artery injury and strokes, and TIAs in rare cases. There is no significant difference in bidirectional block and ablation time rates in the different approaches. Although the success rates are high, assessment of bidirectional block is of utmost importance to reduce recurrence. Evaluation of the block involves the presence of widely split fixed double potentials, electro anatomic mapping, and differential pacing.