Definition
“Coaptation reserve” defined by the actual contact area of the leaflets is less well established, but is still crucial for the intraoperative guidance of MV repair. The leaflet coaptation failure of IMR is due to annular dilatation, leaflet tethering caused by papillary muscle displacement, or both[73]. “Mitral valve reserve” refers to the degree of apposition of the MV leaflets that allows the apparatus to maintain further remodeling without overt systolic incompetence[7,8]. Restrictive annuloplasty is performed under these circumstances to reduce annular area, provide a greater zone of coaptation between the MV leaflets, and consequently reduce the severity of MR[9]. However, in IMR, the remodeling of the MV apparatus can be heterogeneous with varying degrees of apposition/reserve along the coaptation line[10,11].