Ablating Left-sided Atrioventricular Accessory Pathways in Young Patients with Persistent Left Superior Vena Cava: Start in the Coronary Sinus.

While hemodynamically insignificant, a persistent left superior vena cava (PLSVC) draining to the coronary sinus (CS) may have important implications during an electrophysiology study and catheter ablation. Specifically, ablation of left-sided accessory pathways (APs) poses a special challenge secondary to the potential distortion of the mitral valve annulus (MVA) and the possibility of the AP comprising a discrete epicardial trunk involving CS musculature. Ablation of such pathways is more likely accomplished from within the CS rather than on the MVA after a transseptal puncture. We describe two pediatric cases with a PLSVC draining to a dilated CS in whom successful ablation of left-sided APs was accomplished from within the CS after failed ablation attempts on the MVA. Initial mapping and ablation in the CS after a careful evaluation of the coronary artery proximity may obviate the need for a transseptal puncture with its potential challenges.