A patent foramen ovale (PFO) is a hole in the heart that should have closed after birth. Patent foramen ovale (PFO) is a hole between your heart's upper chambers.A test called an echocardiogram is used to diagnose a PFO. The test uses sound waves to create pictures of the beating heart. 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. A patent foramen ovale (PFO) is a hole in the heart that didn't close the way it should after birth. The healthcare provider inserts the catheter through a blood vessel in the groin and guides it to the PFO. However, it may cause serious complications under certain circumstances. Patent foramen ovale (PFO) is a small hole between the upper right and left chambers (atria) of your heart.