Undiagnosed inferior vena cava type of sinus venosus atrial septal defect in a middle-aged woman: A rare case report.

Sinus venosus atrial septal defect (ASD) accounts for 5% to 10% of ASDs. In contrast with the more common superior vena cava (SVC) type, the inferior vena cava (IVC) type of sinus venosus ASD with overriding IVC is extremely rare. The sinus venosus defect occur posterior to the fossa ovalis and is not regarded as true ASD. Transesophageal echocardiography (TEE) is a diagnostic procedure of choice due to close proximity of atrial septum to TEE transducer. However; it may not constantly yield detailed anatomical and functional characterization, and other imaging modalities such as cardiac magnetic resonance imaging (MRI) may be needed. We report the case of a 45-year-old woman with an undiagnosed hemodynamically significant IVC-type ASD without any anomalous drainage of pulmonary veins, who presented with progressive dyspnea.