Patent foramen ovale (PFO)

Patent foramen ovale (PFO) is a flaplike opening between the atrial septa primum and secundum at the location of the fossa ovalis (see the image below) that persists after age 1 year. With increasing evidence being found that PFO is the culprit in paradoxical embolic events, the relative importance of the anomaly is being reevaluated.