A patent foramen ovale is a small, flaplike opening in the wall between the upper chambers of the heart. Most people will not have any signs or symptoms directly from PFO at all.Possible PFO symptoms include: Stroke. A test called an echocardiogram is used to diagnose a PFO. The test uses sound waves to create pictures of the beating heart. The larger the hole, the more likely symptoms are. PFOs, on the other hand, are normal before birth but may fail to close after birth. Infants with a PFO and no other heart defects do not have symptoms. Some adults with PFOs also suffer from migraine headaches. Most people don't have symptoms.