Twelve-year comparison of a Bjork-Shiley mechanical heart valve with porcine bioprostheses BACKGROUND. Patients undergoing heart-valve replacement may receive a mechanical prosthesis, necessitating lifelong anticoagulant treatment, or a porcine bioprosthesis, which involves no absolute need for anticoagulants. METHODS. We carried out a randomized, prospective trial to compare the durability of the Bjork-Shiley mechanical prosthesis (spherical tilting-disk model) and the incidence of valve-related complications with those variables in the Hancock and the Carpentier-Edwards porcine prostheses. The mitral valve was replaced in 261 patients, the aortic valve in 211, and both in 61; the survivors have been followed up for a mean of 12 years. RESULTS. We found a trend toward improved actuarial survival after 12 years with the Bjork-Shiley prosthesis, but this trend was not statistically significant (group with Bjork-Shiley valve vs. group with porcine valve [mean +/- SE], 51.5 +/- 3.2 vs. 44.4 +/- 3.2 percent; P = 0.08). There was no significant difference in the actuarial incidence of reoperation after 5 years, but after 12 years significantly more patients with a porcine prosthesis had undergone reoperation (8.5 +/- 2.0 vs. 37.1 +/- 4.1 percent, P less than 0.001). An analysis combining death and reoperation as end points for an actuarial assessment of survival with the original prosthesis intact confirmed that the patients with Bjork-Shiley Shiley prostheses had improved survival (48.6 +/- 3.2 vs. 30.0 +/- 3.0 percent after 12 years, P less than 0.001). Bleeding requiring hospitalization or blood transfusion was significantly more frequent in the patients with Bjork-Shiley prostheses (18.6 +/- 3.2 vs. 7.1 +/- 2.3 percent after 12 years, P less than 0.01). There was no significant difference after 12 years in the actuarial occurrence of embolism (Bjork-Shiley vs. porcine, 21.1 +/- 3.1 vs. 26.4 +/- 3.5 percent) or endocarditis (3.7 +/- 1.4 vs 4.6 +/- 1.6 percent). CONCLUSIONS. Survival with an intact valve is better among patients with the Bjork-Shiley spherical tilting-disk prosthesis than among patients with porcine bioprostheses, but use of the Bjork-Shiley valve carries an attendant increased risk of bleeding associated with the need for anticoagulant treatment. 