Clinical comparative study between mitral mechanical and bioprosthetic valves. What is the benefit of bioprosthetic valves in the mitral position?

Comparative long-term performance characteristics of mechanical valves and bioprosthetic valves were analyzed retrospectively for patients who had undergone isolated mitral valve replacement from 1967 to 1988. Two hundred ninety-one patients received either mechanical (n = 97) or bioprosthetic (n = 194) valves. The cumulative follow-up was 1,609 patient-years (mean 6.3 +/- 3.8 years, ranging from 0.6 to 20.2 years, 98.9% complete follow-up). The actuarial survival rate, including hospital deaths, at 10 years was 72 +/- 12% for mechanical and 74 +/- 4% for bioprosthetic valve recipients. The rates of freedom from thromboembolism, structural valve failure, prosthetic valve endocarditis, prosthetic valve endocarditis, reoperation, and overall valve-related complications at 10 years were 87 +/- 5%, 100%, 91 +/- 3%, 100%, and 79 +/- 8% for mechanical valve recipients and 85 +/- 3%, 77 +/- 5% (p less than 0.001), 85 +/- 13%, 71 +/- 5% (p less than 0.001), and 52 +/- 5% (p less than 0.001) for bioprosthetic valve recipients, respectively. Thromboembolism occurred at a similar incidence in two types of valves (2.0 +/- 0.7 vs. 2.2 +/- 0.4%/pt-yr). Structural valve failure, reoperations, and overall valve-related events occurred more frequently in the bioprostheses recipients (0 vs. 2.0 +/- 0.4%/pt-yr; p less than 0.001, 0.3 +/- 0.3 vs. 2.9 +/- 0.5%/pt-yr; p less than 0.001, 2.5 +/- 0.8 vs. 5.6 +/- 0.7%/pt-yr; p less than 0.005, respectively). There was no mortality at the time of redo-operation. These results show that bioprostheses in the mitral position exhibit small benefits of antithrombogenesis and prominent disadvantage of poor durability requiring reoperation.