Mitral prolapse, stenosis, regurgitation
Blood flows through four chambers in the heart separated by one-way valves. A major valve is the one separating the upper and lower chambers on the left side of the heart. The left side is especially important because freshly oxygenated blood returning from the lungs is circulated out of the heart to the rest of the body. The left valve, called atrioventricular, for the chambers it separates, is also called the mitral valve, because it is shaped like an upside down Bishop's hat, a miter. If the flaps of this valve tear away due to disease, the process is called prolapse, "a falling forward". This results in leakage and backward flow called "regurgitation" (get the picture?). Sometimes a valve is abnormally narrow causing partial obstruction constricting flow. Stenosis means "a narrowing".