"The mitral valve, also known as the bicuspid or atrioventricular valve, plays a major role in controlling the transfer of blood from the left atrium to the left ventricle. There are two main types of mitral valve disease that can lead to mitral regurgitation: degenerative, in which the leaflets or the sub-valvular apparatus are deformed, and functional, in which cardiomyopathic dilatation of the ventricle or atrium results in malcoaptation of otherwise structurally normal leaflets. In reality, mitral regurgitation is often caused by a combination of both degenerative and functional processes"--