Paradoxical embolism and a patent foramen ovale.

Patients who sustain an unexplained stroke or peripheral ischemic event should be examined for paradoxical embolism via right-to-left shunting. The confirmation of a patent foramen ovale by echocardiography is simple and noninvasive, and should suggest the possibility of a right-sided embolic source. Unrecognized right-to-left shunting that allows paradoxical embolism may be more frequent than generally recognized.