What is a patent foramen ovale (PFO)?

A PFO is present in everyone at the time of birth. When you are a fetus, there is no need for blood to be sent to the lungs because you get all your oxygen from your mother’s blood. A flap between two heart chambers allows blood to be diverted as it returns to the heart to be sent back to the body. At the time of birth, the pressures in the heart change rapidly, and this flap normally closes and scars over. In about 20% of people, however, the flap remains open. This is called a patent foramen ovale.