To present a case of an anomalous connection between the brachiocephalic and pulmonary vein resulting in a right-to-left shunt.

About 40% of ischemic strokes in young patients are cryptogenic. Paradoxical embolism is a well-recognized cause of ischemic stroke that occurs when thrombo-emboli pass through an abnormal connection from the venous circulation into the arterial system, creating a right-to-left shunt. Well-known causes of this include interventricular/interatrial wall defects, and arteriovenous malformations. The most common cause is a patent foramen ovale (PFO), which is found in 25% of the general population and is about twice as prevalent in younger patients with cryptogenic stroke who lack traditional cardiovascular risk factors. This is suggestive that paradoxical embolism could be a major contributor to strokes in young patients.

24 y/o male with no past medical history presented with acute onset of vertigo and right facial droop. MRI head showed acute infarcts in the cerebellar vermis and linear punctate infarcts in the right cerebellum. Workup including CTA head and neck, hypercoagulable studies, duplex US, and heart monitor were unrevealing. TTE showed a small right-to-left shunt with agitated saline concerning for a PFO. Follow up TEE did not show a PFO, however there was evidence of agitated bubbles in the left atrium with a delay of 6-8 beats, suggestive of an extra cardiac shunt. CT angiogram chest found an anomalous vein arising from the left brachiocephalic vein which entered the left inferior pulmonary vein, the source of the right-to-left shunt. There were discussions with interventional cardiology to close this connection, however the patient opted for medical management.

This case report proposes a unique mechanism of paradoxical embolism. Thorough workup for young patients with cryptogenic stroke is needed, as treatment recommendation in patients with a right-to-left shunt often includes surgical intervention.