A patent foramen ovale (PFO) is a hole in the heart that didn't close the way it should after birth.

During fetal development, a small flap-like opening — the foramen ovale (foh-RAY-mun oh-VAY-lee) — is normally present in the wall between the right and left upper chambers of the heart (atria). It normally closes during infancy. When the foramen ovale doesn't close, it's called a patent foramen ovale.

Patent foramen ovale occurs in about 25 percent of the normal population, but most people with the condition never know they have it. A patent foramen ovale is often discovered during tests for other problems. Learning that you have a patent foramen ovale is understandably concerning, but most people never need treatment for this disorder.