RESUMEN
Inferior sinus venosus ASD (atrial septal defect) is a rare congenital cardiac deformity, that occurs on between the inferior vena cava and right atrium. Diagnosis of inferior sinus venosus ASD is difficult because of its infero-posterior location of the fossa ovalis. Therefor, exact anatomical diagnosis by preoperative and intraoperative transesophageal echocardiography is necessary at preoperation and during the operation. We present a case of residual ASD, which was diagnosed secundum ASD and repaired when the patient was 10 years old. Residual ASD was diagnosed by cardiac echocardiography in preparation of otorhinolaryngology operation. Therefore, reoperation of residual ASD was done when the patient was 24 years old. The patient had secundum ASD and inferior sinus venosus ASD, but in the prior operation, inferior sinus venosus ASD wasn't found and only secundum ASD was repaired. In reoperation, inferior sinus venosus ASD was reveled and patch closure was done.