Preferability of bioprostheses for isolated aortic valve replacement. A comparative study between mechanical and bioprosthetic valves.

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Abstract
Comparative long-term performance characteristics of mechanical valves and bioprosthetic valves were analyzed retrospectively among patients who had undergone isolated aortic valve replacement between 1968 and 1987. One hundred sixty-seven patients received either mechanical (n = 82) or bioprosthetic (n = 85) valves. The cumulative follow-up was 926 patient-years (mean 6.1 .+-. 4.7 years, ranging from 0.5 to 20.2 years, 100% complete follow-up). Actuarial survival rate, including operative death, at 10 years was 74 .+-. 7% for mechanical and 77 .+-. 7% for bioprosthetic valve recipients. The rates of freedom from thromboembolism, structural valve failure, prosthetic value endocarditis, and valve re-replacement at 10 years were 77 .+-. 7%, 100% 96 .+-. 2% and 95 .+-. 3% for mechanical, and 94 .+-. 4%, 83 .+-. 8% (p < 0.05), 88 .+-. 5% and 75 .+-. 8% (p < 0.05) for bioprosthetic valve recipients, respectively. Thromboembolism occurred more frequently in the mechanical valve recipients (p < 0.01), and structural valve failure in the bioprostheses recipients (p < 0.05). There was no mortality at the time of valve re-replacement. Most of the bioprosthesis recipients received no anticoagulation therapy beyond 3 months postoperatively. Cardiac medication in the late postoperative period was not required in 31.3% of bioprosthetic, and 3.2% of mechanical valve recipients (p < 0.01). These results show that bioprosthesis in the aortic position exhibits a superb antithrombogenicity and may enable a drug-free state, though its limited durability requires reoperation.

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