POSITION-RELATED FACTORS IN MITRAL AND TRICUSPID BIOPROSTHESES DEGENERATIVE CHANGES

We report clinicopathological findings in 15 patients in whom the same bioprosthesis (BP) had been implanted simultaneously in both mitral a nd tricuspid positions. The aim of the study was to investigate whethe r position-related factors played an important role in BP degeneration . There were 14 women and 1 man with a mean age of 34+/-11 years. The indications for the initial operation were rheumatic in 14 cases and e ndocarditis in one patient. The mean interval before reoperation was 7 .5+/-3.3 years, Predominant cause of reoperation was: structural deter ioration of both mitral and tricuspid BPs (6), mitral regurgitation (5 ), tricuspid BP dysfunction (1), para-aortic leak (1), mitro-aortic th rombi (1). Calcific deposits were the principal cause of early deterio ration of mitral BPs and the major cause of late tricuspid BPs dysfunc tion, This lesion was predominantly related to local factors. Cuspal t ears were the principal cause of late (>9 yrs) mitral BP failure and m ost probably related to mechanical stress. Extensive fibrosis affected only tricuspid bioprostheses. In 7 patients more extensive degenerati ve changes occurred in bioprostheses in the mitral rather than the tri cuspid position (Group I). However, in the remaining eight the magnitu de of the changes was very similar in the two positions (Group II), Th e interval before reoperation was significantly longer in patients of Group II (9.8 yrs, range 5-13) than patients in Group I (4.9 yrs, rang e 3-6), (p<0.01). We concluded that position-related factors exert a m ajor role in bioprosthetic failure. These factors are more deleterious in the mitral position than in the tricuspid position.