Here we report two cases of residual atrial septal defect (ASD) with inferior extension towards the inferior vena cava (inferior sinus venosus type). In both cases, patients underwent surgical repair of their ASD in childhood. However, signs of persistent hemodynamic right ventricular overload were detected at the last follow-up and a residual ASD was demonstrated. Both underwent successful minimally invasive surgical closure of the ASD by combining a right postero-lateral mini-thoracotomy (sub-axillary approach) and total peripheral cardiopulmonary bypass, avoiding snaring of the inferior vena cava. This allowed an optimal visualization of the residual intra-cardiac shunt and its subsequent closure.