Anatomical characteristics of mitral isthmus requiring ablation inside the coronary sinus for creation of complete linear block in patients with atrial fibrillation

Abstract

Background: Radiofrequency energy delivery inside the coronary sinus (CS) is often required to achieve complete linear block at the mitral isthmus (MI). The purpose of this study is to elucidate the morphologic characteristics of the MI which may need ablating inside the CS. Method and results: Ninety-eight consecutive patients (mean age 64±11, 74 male [76%], 51 persistent AF [52%]) who underwent the first linear ablation at the MI during catheter ablation for AF/AT were enrolled in the study. All patients underwent 64-slice MDCT scanning prior to the procedure and its anatomical features of the MI were analyzed. Complete block along the mitral isthmus was achieved in 85 (87%) patients, of which 45 (53%) patients required radiofrequency ablation inside the CS (Group CS), and RF application was not required in the other 40 (47%) patients (Group Non-CS). There were no significant differences in the MI length, isthmus depth, CS diameter, CS cross-sectional area, and the distance between the CS and the MI. However, group CS patients were more likely to have interposed circumflex artery between the CS and the MI (40% vs. 18% p=0.02). Conclusion: Interposition of the circumflex artery between the MI and the CS is associated with a higher probability of requiring ablation inside the CS to achieve complete mitral isthmus block.