Catheter Ablation of the Superolateral Mitral Isthmus Line: A Novel Approach to Reduce the Need for Epicardial Ablation.

BACKGROUND: The mitral isthmus is a critical part of perimitral reentrant tachycardia, as well as an important substrate of persistent atrial fibrillation. Deployment of an endocardial mitral isthmus line (MIL) with the end point of bidirectional block may be challenging and often requires additional epicardial ablation within the coronary sinus.

METHODS AND RESULTS: The study population comprised 114 patients with perimitral flutter who underwent de novo ablation of an MIL. The initial 57 patients (group A) underwent catheter ablation using a novel superolateral MIL design, connecting the left-sided pulmonary veins with the mitral annulus along the posterior base of the left atrial appendage visualized by selective angiography. The next 57 patients (group B) served as a control group and underwent ablation using a conventional MIL design, connecting the left inferior pulmonary vein with the mitral annulus. Bidirectional block was achieved in 56 of 57 patients in group A (98.2%) and 50 of 57 patients in group B (87.7%; P=0.06). Deployment of a superolateral MIL required significantly less ablation from within the coronary sinus (7.0% versus 71.9%; P<0.01). Predictors for unsuccessful bidirectional mitral isthmus blockade were the need for epicardial ablation from within the coronary sinus (P<0.01) and the total length of the MIL (29.3±6.35 mm versus 40.8±7.29 mm; P=0.005). A higher rate of pericardial tamponade was observed in group A (5.2% versus 0%; P=0.24).

CONCLUSIONS: The superolateral MIL is associated with a high acute success rate to achieve bidirectional block using endocardial ablation only with minimal need for epicardial ablation from within the coronary sinus.