Variations in the papillary muscles of the normal mitral valve and their surgical relevance.

A mid-mitral plane passing through the middle of the aortic and mural leaflets divides the chordopapillary support of the mitral valve into anterolateral and posteromedial halves. The papillary muscles of the mitral valve were studied in 100 human autopsy hearts collected at random. The anterolateral papillary support had 1 belly in 67 hearts, 2 in 27, 3 in 4, 4 in 1, and 5 in 1 heart. Likewise, the posteromedial papillary support had 1 muscle belly in 50 hearts, 2 in 36, 3 in 11, and 4 in 3. The single papillary muscles were conical, mammillated, flat topped, grooved, stepped, wavy, arched, sloped or saucerized. When there were two bellies they presented a two tiered, interlinked, parallel, arched, V, Y, or H configuration. Three papillary muscles formed a parallel, interlinked or arched arrangement; or two bellies were interlinked or formed a two tiered arrangement with the third belly separate. When four or five bellies existed, they were parallel or interlinked. In the anterolateral and posteromedial group, the papillary muscle bellies were mostly intraluminal in 14% and 11%, mostly intraluminal with the tip anchored in 19% and 28%, equally sessile and intraluminal in 54.5% and 41.5%, mostly sessile in 12.5% and 19.5%, respectively. In the anterolateral group 19% of papillary muscle bellies arose from the upper third of the ventricle, 79.5% from middle third, and 1.5% from lower third. The corresponding figures for posteromedial group are 6%, 92.5%, and 1.5%, respectively. Four to 22 chordae originated from the anterolateral papillary group, ending in 14 to 72 chordal insertions into the corresponding half of the valve. Likewise, 2 to 18 chordae arose from the posteromedial papillary group ended in 12 to 80 leaflet insertions. The chordae in each group are best considered in toto as a fan. The configuration of the fan is unique in each heart. Imaging techniques need to be refined to outline these variations more precisely. The relevance of chordopapillary variations in rheumatic heart disease, reparative procedures, papillary muscle dysfunction, mitral valve prolapse, mitral valve replacement, and use of mitral valve homograft for mitral/tricuspid replacement is discussed.