A Delayed Presentation of a Sinus Venosus Atrial Septal Defect.

Sinus venosus atrial septal defects (ASDs) are rare congenital anomalies that result from an abnormality of the junction between the right atrium, superior vena cava (SVC), and pulmonary veins. This defect causes right-to-left shunting, which can lead to progressive right heart enlargement. We present a case of a 59-year-old man with a history of hypertension and hyperlipidemia who presented with dyspnea and newly diagnosed atrial flutter. Transthoracic echocardiography, transesophageal echocardiography, and CT imaging revealed a sinus venosus ASD with multiple anomalous pulmonary venous returns. The patient underwent successful surgical repair of the defect, which included ASD closure, augmentation of the SVC, and redirection of the anomalous pulmonary veins into the left atrium. This case underscores the importance of maintaining a high index of suspicion for congenital defects such as sinus venosus ASDs, even in adults, and the role of advanced imaging and timely surgical repair in these patients.