[Pathology of the cardiac valves]

The cardiac valves develop from the endocardial cushions of the fetus. Some congenital anomalies such as the 21-trisomy syndrome (Down syndrome) show poorly differentiated immature valves similar to those under development. The normally mature valves have four layers of the connective tissue, i.e., proximalis, spongiosa, fibrosa and distalis. Gargoylism promotes abnormal thickening of collagen fibers in the fibrosa via acid-mucopolysaccharide (aMPS) overproduction, but Marfan syndrome weakens the valves in spite of increased aMPS. The reversed conditions could be caused by the difference of increased aMPS; i.e., dermatan sulfate B or heparitin sulfate in gargoylism, on the contrary, dermatan sulfate A and C or hyaluronic acid in Marfan syndrome. Hemodynamic changes in the valves consist of diffuse hypertrophy of the proximalis and fibrosa in high flow cases and focal thickening of the proximalis at the line of closure and of the spongiosa at the anatomical edge in high pressure cases. Aging of the valves simulates partly the hemodynamic changes but degeneration of collagen fibers in the fibrosa after consumption of the spongiosa is more prominent than the latter. So-called myxomatous degeneration in the mitral valve prolapse cases seems reactive hypertrophy of the spongiosa replacing the interrupted fibrosa. Spontaneous chordal rupture is partly related to myxomatous change, but that in the elderly cases shows only simple disruption of collagen fibers with loss of the spongiosa tissue. Calcification of the valvular rings and bodies often observed in the elderly cases with parallelism to degeneration of the connective tissue produces mitral regurgitation, aortic stenosis or both, showing a preponderance of females.(ABSTRACT TRUNCATED AT 250 WORDS)