Caught in the act: entrapped embolus through a patent foramen ovale.

A patent foramen ovale (PFO) is detected frequently by transesophageal echocardiography. The diagnosis of paradoxical embolism is usually presumptive when arterial emboli occur in the appropriate clinical setting. Presumably, paradoxical embolism of small thrombi arise in the venous system and pass through the PFO during a transient right-to-left shunt; however, cases demonstrating a thrombus traversing the PFO are relatively few.