A patent foramen ovale is a small, flaplike opening in the wall between the upper chambers of the heart. This hole may let blood flow between the atria.PFO often has no symptoms. Infants with a PFO and no other heart defects do not have symptoms. Some adults with PFOs also suffer from migraine headaches. Most of the time, a PFO itself causes no symptoms. Sometimes symptoms do result from the complications of a PFO, such as stroke. Most people don't have symptoms. Most of the time, PFO itself causes no symptoms. Sometimes symptoms do result from the complications of PFO, like stroke.