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

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 valve 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 less than 0.05), 88 +/- 5% and 75 +/- 8% (p less than 0.05) for bioprosthetic valve recipients, respectively. Thromboembolism occurred more frequently in the mechanical valve recipients (p less than 0.01), and structural valve failure in the bioprostheses recipients (p less than 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 less than 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.