Prominent persisting Eustachian valve initiates spontaneous right-to-left shunt and paradoxical embolism in a patient with patent foramen ovale.

The Eustachian valve (EV) is an embryological remnant of the inferior vena cava valve that prenatally directs the oxygenated blood from inferior vena cava across the patent foramen ovale (PFO) into systemic circulation. We present a 30-year-old man with PFO whose prominent EV initiated spontaneous right-to-left shunt without Valsalva maneuver and promoted paradoxical embolism. Even when the persistence of EV is prominent in adult, it has been considered to be benign finding in the absence of the associated cardiac anomalies. EV should be considered as an adjunctive risk factor for paradoxical embolism in patients with PFO.