The pioneering cardiac surgeon Alain Carpentier, MD, PhD, developed a functional classification to reflect the underlying pathological changes that contributed to MR (Carpentier A. 1983) (Figure 4). As described in this classification, type I MR is characterized as normal leaflet motion but with annular dilatation or leaflet perforation; type II lesions are related to leaflet prolapse and may be caused by myxomatous disease, such as chord rupture or elongation, or by papillary muscle rupture or elongation; and type III lesions are caused by restricted leaflet motion. Type IIIA is typically caused by rheumatic valve disease with normal ventricular motion.
