A huge mediastinal organizing hematoma causing reversal of atrial septal defect shunt flow

We report a case of a 46-year-old woman who presented with subacute exertional dyspnea and severe hypoxia. A large cystic mass compressing the right side of the heart along with right-to-left atrial shunt flow through an alleged atrial septal defect (ASD) were detected on echocardiography. CT scan of the chest and MRI of the heart revealed a loculated cystic mediastinal mass with hemorrhage measuring 5.5x8 cm compressing the right atrium and ventricle. The patient underwent cyst resection and primary closure of the ASD. This report illustrates a case of an unusual symptomatic pericardial mass compressing the right atrium and ventricle in a patient with an secundum ASD.