[Long-term results of heterografts in the mitral position].

The long term results in 43 patients who underwent mitral valve replacement with a bioprosthesis are reported. The average age of the patient was 25, and nearly half of them were under fifteen. The underlying valvular disease was rheumatic in the great majority. Small bioprostheses were used in 40 p. 100 of cases. Hospital mortality was nil. Two patients developed atrioventricular block and needed permanent pacing; this was the principal complication observed in this study. After 34 months, 17 serious complications were recorded including two episodes of thromboembolism. The main problem arose from restenosis of the bioprosthesis, either because of its small size (3 cases) or because of degeneration (6 cases), all in children (33 p. 100 of our paediatric cases). The actuarial survival rate without degeneration shows only 48,2 p. 100 of patients to be without this problem at 5 years. Late mortality reached 29 p. 100 and the five year survival rate showed only 57 p. 100 of patients to be still alive, and only 35 p. 100 with their bioprosthesis. The haemodynamic profile of these prostheses with regards to transvalvular pressure gradient and mitral surface area, was very good for the large size valves, in contrast to the small size. In the absence of degeneration, the gradient was found to be stable. This study has shown that small bioprosthetic valves should be avoided in mitral valve replacement because of the risk of stenosis. Despite the low incidence of thromboembolism, they should not be used in children because of the high incidence of degeneration in paediatric patients.(ABSTRACT TRUNCATED AT 250 WORDS)