Introduction: Atrial septal defect (ASD) is the second most common adult congenital heart disease, usually asymptomatic until the third decade. Superior sinus venosus defect (SVASD) account for 5% of ASD and it is usually associated with the partial or complete connection of right pulmonary veins to vena cava superior (SVC) or right atrium (RA) (1, 2).

Case report: We report a case of a 45-year-old woman with previously known thyroiditis and hyperprolactinemia. She was referred for echocardiographic examination after an accidental finding of mid-systolic murmur during preoperative preparation for ovarian cyst surgery. She worked as a waiter and reported exertional dyspnea. An electrocardiogram revealed sinus rhythm with the right bundle branch block. Transthoracic echocardiography (TTE) demonstrated a normal-sized left heart with preserved systolic function (LVEF 70%), a dilated RA and right ventricle (RV) without signs of pulmonary hypertension. Cardiac magnetic resonance (CMR) showed a dilated RV (end-diastolic diameter 46 mm), dilated RA and dilated pulmonary artery (diameter 33 mm). During the CMR scan there was constantly a high concentration of contrast in the RV which raised suspicion of shunt presence. Transesophageal echocardiography using contrast revealed SVASD (Figure 1, Figure 2). The patient was referred for computer tomography angiography which demonstrated superior SVASD, 16 mm in width. The right superior pulmonary vein had abnormal inflow into SVC, while the right inferior and both left pulmonary veins had typical anatomical inflow into the left atrium. Cardiac scintigraphy with technetium-99 confirmed the existence of a left-right shunt, Qp: Qs ratio of 1.7: 1. Surgical repair was performed by forming an intraatrial patch using autologous pericardium and dilating plastic of the SVC and RA with a xenopericardial patch. Postoperative recovery went well and control TTE showed less dilated RV with good patch position and no signs of shut over intraatrial septum.

Conclusion: We represented a rare case of congenital heart disease, diagnosed in a middle-aged patient. Having a patient with a dilated right heart and normal-sized left heart without signs of pulmonary hypertension needs to raise suspicion of L-R shunt existence and further investigation should be done.