The Fontan operation is the primary surgical technique used for palliation of patients with single-ventricle physiology. Arrhythmias are frequently observed and associated with morbidity and mortality in Fontan patients. The frequency of arrhythmias after the Fontan procedure increases over time and it was reported to reach 50% in a 20-year follow up. Atrial tachyarrhythmias, especially atrial tachycardia and sinus bradycardia, are most frequently observed in these patients. Ventricular arrhythmias are rarely observed.