A patent foramen ovale is a small, flaplike opening in the wall between the upper chambers of the heart. PFO often has no symptoms.Many people don't need treatment unless they're at risk of stroke or blood clots. A test called an echocardiogram is used to diagnose a PFO. The test uses sound waves to create pictures of the beating heart. The larger the hole, the more likely symptoms are. PFOs, on the other hand, are normal before birth but may fail to close after birth. Most people don't have symptoms. Symptoms of Patent Foramen Ovale. While most PFOs do not cause any symptoms and they can sometimes lead to very serious complications, such as stroke.