Mitral valve basal chordae: Comparative anatomy and terminology

Background. Recent awareness of the importance of the mitral valve's basal chordae stimulated a comparative anatomic study of these chordae in 11 human, 10 ovine, and 10 porcine hearts. Methods. The basal chordae were defined as the chordae that arise from the papillary muscles and insert into the ventricular aspect of the leaflets. Results. All leaflet insertions of the basal chordae were close to the annulus, except at the anterior mitral leaflet, where insertion was at the junction of the smooth and rough zones. The number of basal chordae was 24.6 +/- 4.21 in the porcine, 19.7 +/- 2.90 in ovine, and 18.81 +/- 3.54 in the human hearts. At least two anterior basal chordae were present in each half of the anterior leaflet in 70% of ovine and porcine and in 100% of human hearts. At least two basal chordae were present in each half of the middle scallop of the posterior mitral leaflet in 80% of ovine, 70% of porcine, and 63.6% of humans. Among them, only the two principal or strut chordae were identified as the longest and thickest. Conclusions. The basal chordae of the mitral valve follow a definite pattern in each of the three species studied. A new and logical terminology that should facilitate identification of specific basal chordae is suggested.