MORPHOLOGIC CLASSIFICATION OF THE MITRAL PAPILLARY-MUSCLES

Background and aims of the study: Mitral homograft replacement require s a good knowledge of the anatomy of the papillary muscles. Clinical e xperience with mitral homografts has revealed an as yet unexplored asp ect of the morphology of the mitral subvalvular apparatus, that is cor respondence between papillary muscle sub-divisions and chordal attachm ent to the leaflets. Methods:To further our understanding we subjected 65 normal hearts to close scrutiny which confirmed our perioperative observations. Results: We could establish a classification based on th e ways that the papillary muscles relate to the leaflets via the chord ae. Four types are described. In type I the papillary muscle is single . in type II the papillary muscle has two heads, one of which sends ch ordae exclusively to the posterior leaflet. In type III the papillary muscle is also divided, one head supporting the commissural area exclu sively. Type IV PM resembles type III but is distinguished from it in the way that the head supporting the commissure is very short. In this type the different heads also originate at different levels on the ve ntricular wall from the apex to the base.