Morphologic variability of the mitral valve leaflets.

OBJECTIVES: The rapid development of surgical and less-invasive percutaneous mitral valve repair procedures has increased interest in mitral valve anatomy. We characterize the morphologic variability of the mitral valve leaflets and provide the size of their particular parts.

METHODS: We studied 200 autopsied human hearts from white individuals without any valvar diseases. We measured the intercommissural and aorto-mural diameters of the mitral annulus and identified the leaflets and their scallops. We also noted the base and the height of the inferoseptal commissure, superolateral commissure, anterior mitral leaflet, and posterior mitral leaflet with their scallops.

RESULTS: Variations in posterior mitral leaflet were found in 55 specimens (27.5%), and variations in anterior mitral leaflet were found in 5 hearts (2.5%). The most common variations included valves with 1 accessory scallop between P3 and inferoseptal commissure (7%), accessory scallop between P1 and superolateral commissure (4%), connections of P2 and P3 scallops (4%), connections of P1 and P2 scallops (3%), and accessory scallop in anterior mitral leaflet (2.5%).

CONCLUSIONS: In all cases, the mitral valve is built by 2 main leaflets with possible variants in scallops (29.5%). The variations are largely associated with posterior mitral leaflet and are mostly related to the presence of accessory scallop. Anatomically, the anterior mitral leaflet is not divided into scallops, but could have an accessory scallop (2.5%). Understanding the anatomy of the mitral valve leaflets helps with the planning and performing of mitral valve repair procedures. Variations in scallops may affect repair procedures, but unfortunately cannot be predicted by any of the annular sizes.