Twenty year comparison of a Bjork-Shiley mechanical heart valve with porcine bioprostheses

Abstract

Objective: To compare survival and outcome in patients receiving a mechanical or bioprosthetic heart valve prosthesis.

Design: Randomised prospective trial.

Setting: Tertiary cardiac centre.

Patients: Between 1975 and 1979, patients were randomised to receive either a Bjork-Shiley or a porcine prostheses. The mitral valve was replaced in 261 patients, the aortic in 211, and both valves in 61 patients. Follow up now averages 20 years.

Main outcome measures: Death, reoperation, bleeding, embolism, and endocarditis.

Results: After 20 years there was no difference in survival (Bjork-Shiley v porcine prosthesis (mean (SEM)): 25.0 (2.7)% v 22.6 (2.7)%, log rank test p = 0.39). Reoperation for valve failure was undertaken in 91 patients with porcine prostheses and in 22 with Bjork-Shiley prostheses. An analysis combining death and reoperation as end points confirmed that Bjork-Shiley patients had improved survival with the original prosthesis intact (23.5 (2.6)% v 6.7 (1.6)%, log rank test p < 0.0001); this difference became apparent after 8-10 years in patients undergoing mitral valve replacement, and after 12-14 years in those undergoing aortic valve replacement. Major bleeding was more common in Bjork-Shiley patients (40.7 (5.4)% v 27.9 (8.4)% after 20 years, p = 0.008), but there was no significant difference in major embolism or endocarditis.

Conclusions: Survival with an intact valve is better among patients with the Bjork-Shiley spherical tilting disc prosthesis than with a porcine prosthesis but there is an attendant increased risk of bleeding.

Figure 1

Survival among all patients. There was no significant difference between patients receiving a Bjork-Shiley prosthesis and those receiving a porcine prosthesis (log rank test: p = 0.39). The numbers of surviving patients after each year of follow up are shown at the bottom of the figure.

Figure 2

Survival among all patients with original prosthesis intact (that is, survival without reoperation). Valve survival was significantly better in the patients with Bjork-Shiley prostheses (log rank test: p < 0.0001). The numbers of surviving patients with the original prosthesis intact are shown at the bottom of the figure.

Figure 3

Survival among patients with original prosthesis intact, according to site of implantation (aortic or mitral valve). Valve survival was significantly better in those receiving Bjork-Shiley prostheses than in those receiving porcine prostheses, both in the group undergoing aortic valve replacement (log rank test: p = 0.025) and in the group undergoing mitral valve replacement (log rank test: p < 0.0001). The separation of the survival curves occurred earlier in those undergoing mitral valve replacement. The numbers of surviving patients with the original prosthesis intact are shown at the bottom of the figure.

Figure 4

Survival without major event according to site of implantation (aortic or mitral valve). Survival without major event was significantly better in patients undergoing single aortic valve replacement than in those undergoing single mitral valve replacement. For patients undergoing single mitral valve replacement, survival without major event was better with Bjork-Shiley prostheses (log rank test: p = 0.005) but there was no significant difference in the aortic valve replacement group (log rank test: p = 0.34). The numbers of patients surviving without event are shown at the bottom of the figure.