Patent foramen ovale and atrial septal defect closure is a routine procedure to close holes in the upper chambers of the heart. A patent foramen ovale, or PFO, is a special type of hole between the upper chambers of the heart.However, it may cause serious complications under certain circumstances. 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. Patent foramen ovale (PFO) is a congenital cardiac lesion which is generally asymptomatic and affects up to a quarter of the population. Treatment is a catheter procedure or surgery to close the opening in the heart. Percutaneous closure of a patent foramen ovale (PFO) reduces the risk of recurrent cryptogenic stroke specifically in younger patients. If you have a PFO and low blood oxygen levels or an unexplained stroke, you may need a procedure to close the hole. ASD = atrial septal defect; PFO = patent foramen ovale.