Abstract
Supraventricular or ventricular tachycardia is one of the most serious late sequelae in patients with a single ventricle who have undergone a Fontan operation. A patient with ventricular tachycardia involving the His-Purkinje system was deemed at high risk of atrioventricular block with ablation. Three-dimensional electroanatomic mapping-guided cryoablation was feasible without the development of atrioventricular block with long-term freedom from recurrence.