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 is a flap-like opening in the heart between the upper chambers. The foramen ovale is a structure in the wall of the heart between the two upper chambers. Patent foramen ovale closure is a procedure to close a hole in the heart. We use minimally invasive approaches to treat PFO without open-chest surgery. A patent foramen ovale (PFO) is a small opening between the two upper chambers of the heart, the right and the left atrium. A PFO closure is a procedure that can help lower the risk of a stroke for some people. However, it may cause serious complications under certain circumstances. A patent foramen ovale (PFO) is a hole in the wall between the heart's two upper chambers (atria).