When the heart is developing, an opening exists between the left and right atria of the heart. This opening should close within the first two years after birth. If it does not, this hole is called patent foramen ovale. Medical science does not know why the hole does not close in roughly one out of four people.
The infant with PFO and no other heart issues won't display any symptoms. Most people with PFO do not know they have it. As long as you don't have any symptoms, you don't need to treat PFO. It is associated with increased risk of stroke, although most people with PFO will not have a stroke. It is also associated with migraines with auras, which have disappeared in some people who have had their PFO closed.
Symptoms of PFO include fatigue, shortness of breath upon exertion, heart palpitations, swelling in the legs, feet and ankles, cyanosis, or possibly stroke. At this point, exercise is impossible. Even the smallest activities will leave you out of breath. If your doctor discovers a PFO, it is a simple procedure, similar to a cardiac catherization, to insert an implant that the heart grows around and closes the hole. It is usually done on an outpatient basis. After a short restriction on lifting, you will be back to normal activities.
If the PFO is small, it might have a limited effect on heart function. If the PFO is large, then a large amount of oxygen-rich blood leaks from the left side of the heart to the right. The blood is pumped back into the lungs, although it just came from there, fully loaded with oxygen. The right side of the heart has to work harder to compensate. The extra blood flow can also cause damage to the lung arteries.
Most people, whether with small, unrepaired PFOs, or with repaired PFOs, do not require any special precautions. Those rare exceptions would be patients who developed high pressure in their lungs. There is no risk during pregnancy for a repaired PFO. Once the PFO has been repaired, further surgery is unlikely. Medications are also not necessary.