PATHOLOGY OF MITRAL-VALVE IN REGULARLY SLAUGHTERED PIGS - AN ABATTOIRSURVEY ON THE OCCURRENCE OF MYXOID DEGENERATION (ENDOCARDIOSIS), FIBROSIS AND VALVULITIS

The aim of this study was to report the prevalence of degenerative and early inflammatory lesions and to discuss some histological aspects o f normal and pathological mitral valve leaflets in healthy, normally s laughtered pigs. Mitral valves were collected from 112, 6 month-old, p igs reared under different conditions. Histological examination reveal ed the presence of myxoid degeneration in 29.5% of the valves with no significantly different prevalence according to rearing conditions; fi brosis was present in 12.5%; inflammation (non-vegetative valvulitis) occurred in 20 (17.9%) macroscopically normal valves. No vegetative en docarditis could be observed. A significantly higher degree of inflamm ation was observed in valves affected by myxoid degeneration (P < 0.05 ) and Anitschkow cells were prevalent in all the pathological valves ( P < 0.01). Capillaries were observed in a wide majority of the valves (86.5%), but small arterioles were related to fibrotic thickening of t he leaflets (P < 0.01). The following conclusions are discussed: (1) e nvironmental factors seem not to influence the prevalence of endocardi osis; (2) inflammatory foci in myxoid valves are a reaction to both ab normal friction and products of degraded collagen and extracellular ma trix; (3) the authors consider the presence of capillaries in pig valv es a normal finding whereas proliferation of the vessels occurs under pathological conditions; (4) non vegetative valvulitis can be related to the presence of vessels in the valve and may have a role in both in fectious endocarditis and fibrosis; (5) Anitschkow cells are normally observed in pig valves and are not specifically related to pathologica l lesions.