Whereas primary mitral regurgitation (MR) is due to a structural or degenerative abnormality of the mitral valve (MV) or adjacent structures, secondary or functional MR occurs in the absence of organic MV disease, usually resulting instead from left ventricular (LV) dysfunction. This dysfunction and the resultant remodeling lead to apical and lateral papillary muscle displacement or deformation of the MV annulus, thereby interfering with leaflet coaptation. The development of secondary MR is associated with a poorer prognosis in patients with heart failure of any cause.