[Morphogenesis of mitral valve calcification in rheumatism and the significance of the petrifications in surgical practice].

Eighty-five calcified mitral valves were examined histologically and histochemically and 28 valves were examined in the scanning electron microscope. Different forms of calcification were discovered in rheumatic sclerosis of the mitral valve: dust-like, laminar petrifact, large-tuberous petrifact with protein apoplexy. The cardiac valve calcification in rheumatic fever is preceeded by local dystrophic changes of collagen fibers which undergo swelling, homogenization, and become picrinophilic. Qualitative changes in collagen predispose to calcium salts adsorption by collagen fibers. Scanning electron microscopy revealed the features of three-dimensional structure of petrifactions at various stages of their development. Dust-like petrifactions are microplates of lime with smooth surface, laminar petrifacts consist of accumulations of these microplates. The surface of large-tuberous petrifacts is irregular, ulcerated, covered with thrombotic masses.