Patent foramen ovale closure can help reduce risk of another ischemic stroke. Learn more about a minimally-invasive treatment option.A patent foramen ovale (PFO) is a hole in the wall between the heart's two upper chambers (atria). Before birth, all babies have this opening. The foramen ovale is a hole in the wall between the left and right atria of every human fetus. However, it may cause serious complications under certain circumstances. This test uses bubbles and images to look for the hole in the septum of the heart. How is a PFO treated? Your patent foramen ovale (PFO) closure was done to close a small hole in the area that separates the upper right and left chambers (atria) of the heart. If you have a PFO and low blood oxygen levels or an unexplained stroke, you may need a procedure to close the hole.