[An unexpected case of right heart dilation in the elderly].

Atrial septal defects (ASD) represent the most common congenital heart defect diagnosed in adulthood. Adults with an ASD are often asymptomatic, but sometimes may present with non-specific symptoms such as dyspnea on exertion or exercise intolerance. Isolated sinus venosus atrial defect is an extremely rare anomaly. Sinus venosus defects occur more commonly in the superior (rather than inferior) portion of the embryologic sinus venosus and commonly occur with partial anomalous pulmonary venous return, particularly of the right upper pulmonary vein. We describe the case of an 80-year-old man with an undiagnosed, hemodynamically significant superior sinus venosus type of ASD who presented with persistent dyspnea and hypoxia after COVID-19 disease. Although cardiac magnetic resonance represents the gold standard for the morpho-functional evaluation of ASDs, transesophageal echocardiography is an accessible method for diagnosing the superior sinus venosus type of ASD and three-dimensional transesophageal echocardiography is useful for obtaining an "en face" view of the ASD and important surrounding structures.