CLINICAL COMPARATIVE STUDY BETWEEN MITRAL MECHANICAL AND BIOPROSTHETIC VALVES : What is the Benefit of Bioprosthetic Valves in the Mitral Position?

Abstract

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<0.001), 85±13%, 71±5% (p<0.001), and 52±5% (p<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<0.001, 0.3±0.3 vs. 2.9±0.5%/pt-yr; p<0.001, 2, 5±0.8 vs. 5.6±0.7%/pt-yr; p<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.