ABSTRACT
Mitral valves tissue samplings from children with complete (13 patients) and partial (6 patients) atrioventricular defects at the age of from I month to 3 years old were examined. The biopsy material was received during the repeat surgical operation on mitral valve, performed due to residual mitral valve regurgitation grade 3-4 at the period of time from 2 days to 1 year after radical defect correction. On histological examination the areas of myxomatous tissue degeneration occupying more than 50% of mitral valves surface were found in 6 (32%) of the 19 patients. There were dispersed star-shaped cells, architectonics disturbances, deposition of acid mucopolysaccharides and increased content of matrix metalloproteinase 13 in such areas of myxomatous degeneration. The sizes of these areas correlated with mitral valve regurgitation grade. After the radical correction of atrioventricular defect the sutures on the folds and fibrous ring of the mitral valve "cut through" reliably more often in patients with wider areas of myxomatous degeneration, which indicates poor prognosis. According to the ultrastructural classification the majority of mitral valve cells regarded as fibroblasts; there also were found cells with the signs of myogenic differentiation--myofibroblasts and isolated hystiocytes. According to the immunohistochemistry assay the cells phenotype regarded as fibroblastic and endothelial differentiation; in some patients there were found cells of smooth muscle origin.
