Cardiovascular collapse and hypoxemia in a man with a right-sided mediastinal mass, undiagnosed atrial septal defect, and right-to-left shunt

A 65 year old man presented with fever, pancytopenia, hypoxemia, and cardiovascular collapse requiring intensive care unit admission. Computed tomographic pulmonary angiogram showed a right-sided mediastinal mass adjacent to the right atrium. The patient had a video-assisted thoracoscopic surgical biopsy of the mass, with selective bronchial blockade to maximize oxygenation during lung isolation. Intraoperative transesophageal echocardiography showed an unexpected large atrial secundum defect with a right-to-left shunt and intracardiac mass. This shunt could be reversed with a norepinephrine infusion, resulting in improved oxygenation. Histopathology showed potentially curative diffuse large B cell lymphoma (DLBCL).