A patent foramen ovale or PFO is a defect in the wall between the two upper chambers of the heart. Patients who do need treatment may take medicines or have a percutaneous coronary intervention to close the PFO.In more serious cases, surgery may be needed. The foramen ovale is a hole in the wall between the left and right atria of every human fetus. This hole allows blood to bypass the fetal lungs. PFO closure is an outpatient, catheter-based procedure that lasts between one and two hours. A patent foramen ovale is a small, flaplike opening in the wall between the upper chambers of the heart. A patent foramen ovale occurs when a hole that is always present in a newborn's heart fails to close as it should once the lungs begin to function after birth. The interatrial septum is the thin wall that separates the upper atrial cavities of heart. A patent foramen ovale (PFO) means that the foramen ovale stays open after birth.