Quantitative study of the mitral valve in chronic rheumatic heart disease.

A quantitative study of the mitral valve and its tension apparatus was carried out in 54 cases of pure mitral stenosis, 13 cases of mitral stenosis with incompetence, both diseased groups due to rheumatism, and 25 normals. In the group with pure mitral stenosis, the annular size was unaltered but the annular attachment of the mural leaflet was decreased. The average circumference of the orifice was 27 mm. The leaflet length increased by 24%. In the group with mitral stenosis with incompetence, the annular size was increased by 18%. The average circumference of the orifice was 39 mm, but no significant increase in the length of the leaflets was found. The rough zone of the aortic leaflet in pure mitral stenosis is disproportionately increased, indicating greater apposition during closure. In pure mitral stenosis, the cords were severely affected as compared to combined lesion. They were totally absent in 18.5% of cases while this lesion was restricted to the aortic leaflet in 37%. The commissural, paracommissural and paramedial cords were not seen in 75, 60, and 72%. The main cords were not seen in 50% of cases. In the combined lesion, cords attached to the aortic leaflet only were absent in 7.69%. The commissural, paracommissural and paramedial cords were absent in 33, 39, and 23%, respectively. The main cords were absent in only 19%. The reduction in lengths of the cords is more marked in cases with pure stenosis. We conclude that the mitral valve is better preserved in the group having stenosis with incompetence, the incompetence being the result of a larger annulus and orifice with normal leaflets and shorter tendinous cords. In pure mitral stenosis, the incompetence through a small orifice is prevented by the longer leaflets, particularly the aortic.