Embolization of a symptomatic systemic to pulmonary (right-to-left) venous shunt caused by fibrosing mediastinitis and superior vena caval occlusion.

Paradoxical embolization can occur when a right-to-left shunt allows a venous thromboembolus to escape filtration by the lungs. Venous collateral pathways draining into the left heart incited by superior vena cava obstruction are a rare acquired right-to-left shunt. Herein, the authors report on a case of transient ischemic attack in a patient with vena caval occlusion secondary to histoplasmosis-related fibrosing mediastinitis, with subclavian vein thrombosis and a right-to-left extracardiac shunt diagnosed with echocardiography. Despite the complexity of the collateral network, this shunt was successfully eradicated with coil embolization.