A 14-year-old male patient presented with cyanosis and tiredness. The patient had undergone a Glenn procedure at age 12 following the echocardiographic determination of a double inlet left ventricle, ventriculoarterial discordance, moderate valvular-subvalvular pulmonary artery stenosis, non-restrictive inlet ventricular septal defect and right ventricle hypoplasia; his oxygen saturation was 70%. Echocardiography evaluation showed retrograde flow from the vena cava superior to the innominate vein and a left superior vena cava (LSVC) opening into the coronary sinus (CS). Here, we report the case of a patient evaluated for Glenn dysfunction in whom an increase in oxygen saturation was observed following transcatheter occlusion of the LSVC-CS connection using an Amplatzer septal occluder.