The Operation: Surgery Live S01E01 - Open Heart Surgery

David had a leaky mitral valve in his heart, which was causing him to feel extremely tired and short of breath. A functioning mitral valve only lets blood flow in one direction through the left side of the heart. However, when the valve is damaged, blood can flow the wrong way, resulting in increased pressure on the heart. If David's condition had been left untreated his heart would have eventually failed.