Patent foramen ovale

Fetuses have a normal opening between the left and right atria (upper chambers) of the heart. This usually closes naturally soon after the baby is born. Patent foramen ovale (PFO) occurs when the opening fails to close after birth. About 25 percent of adults have a PFO. Patent foramen ovale may increase a person’s risk for heart attack and stroke.

The cause of patent foramen ovale is unknown and there are no known risk factors for developing it. PFO usually has no symptoms.