Morphological variations and morphometry of the papillary muscles of the mitral valve – a cadaveric study

Recent advances and refinements in mitral valve surgery as well as interventional procedures have revived the interest in disparity in the morphology and morphometry of papillary muscles of the mitral valve. Study was taken up with an effort to extend the concepts previously presented on papillary muscles of mitral valve. Papillary muscles were studied in 320 fresh autopsied adult normal hearts. With varying number of muscle bellies. Anterolateral (ALPM) and posteromedial (PMPM) groups of papillary muscles were found. In two hearts, the ALPM and PMPM were connected by muscle tissue. According to the number of separate muscle bellies, 4 groups were categorized with increasing complexity. Single belly was the commonest form in the ALPM (73 %) and two bellies were the commonest form in the PMPM (40 %). The papillary muscles show a great variability on the nature of attachment to the ventricular wall. More than half of the hearts studied had a mixed type of papillary muscles (partly tethered and partly protruding in ALPM and PMPM groups. The mean distance separating the mitral annulus from the apex of the ALPM was 19.38 mm ± 3 SD (range 5 – 26) and from the apex of the PMPM was 20.36 mm ± 3.7 SD (range 10 – 32). The average length of ALPM was 32.24 mm ± 4.8 SD (range 20 - 45) and that of the PMPM was 29.92 mm ± 4.9 SD (range 16 - 44). The documented classical view of two papillary muscles should be adapted with 4 types of variations in morphology with increasing complexity.