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. Patent foramen ovale (PFO) is a hole between your heart's upper chambers. Most people with PFO do not require treatment. But in some cases, the opening in the heart wall must be closed. A patent foramen ovale (PFO) is a hole in the heart that didn't close the way it should after birth. Patent foramen ovale (PFO) is a hole between the left and right atria (upper chambers) of the heart. This hole exists in everyone before birth.