Mechanical or Biologic Prostheses for Aortic-Valve and Mitral-Valve Replacement

Abstract

Background: In patients undergoing aortic-valve or mitral-valve replacement, either a mechanical or biologic prosthesis is used. Biologic prostheses have been increasingly favored despite limited evidence supporting this practice.

Methods: We compared long-term mortality and rates of reoperation, stroke, and bleeding between inverse-probability-weighted cohorts of patients who underwent primary aortic-valve replacement or mitral-valve replacement with a mechanical or biologic prosthesis in California in the period from 1996 through 2013. Patients were stratified into different age groups on the basis of valve position (aortic vs. mitral valve).

Results: From 1996 through 2013, the use of biologic prostheses increased substantially for aortic-valve and mitral-valve replacement, from 11.5% to 51.6% for aortic-valve replacement and from 16.8% to 53.7% for mitral-valve replacement. Among patients who underwent aortic-valve replacement, receipt of a biologic prosthesis was associated with significantly higher 15-year mortality than receipt of a mechanical prosthesis among patients 45 to 54 years of age (30.6% vs. 26.4% at 15 years; hazard ratio, 1.23; 95% confidence interval [CI], 1.02 to 1.48; P=0.03) but not among patients 55 to 64 years of age. Among patients who underwent mitral-valve replacement, receipt of a biologic prosthesis was associated with significantly higher mortality than receipt of a mechanical prosthesis among patients 40 to 49 years of age (44.1% vs. 27.1%; hazard ratio, 1.88; 95% CI, 1.35 to 2.63; P<0.001) and among those 50 to 69 years of age (50.0% vs. 45.3%; hazard ratio, 1.16; 95% CI, 1.04 to 1.30; P=0.01). The incidence of reoperation was significantly higher among recipients of a biologic prosthesis than among recipients of a mechanical prosthesis. Patients who received mechanical valves had a higher cumulative incidence of bleeding and, in some age groups, stroke than did recipients of a biologic prosthesis.

Conclusions: The long-term mortality benefit that was associated with a mechanical prosthesis, as compared with a biologic prosthesis, persisted until 70 years of age among patients undergoing mitral-valve replacement and until 55 years of age among those undergoing aortic-valve replacement. (Funded by the National Institutes of Health and the Agency for Healthcare Research and Quality.).

Figure 1.. Mortality after Aortic-Valve Replacement with a Biologic or Mechanical Prosthesis.

All-cause mortality is plotted against time after surgery and stratified according to age group. The group of patients who received a mechanical valve is the reference group. The numbers of patients at risk are included below each graph. Note that the numbers are not necessarily integers owing to inverse probability weighting.

Figure 2.. Age-Dependent Hazard of Death with a Biologic Prosthesis, as Compared with a Mechanical Prosthesis, in the Aortic-Valve or Mitral-Valve Position.

The hazard ratio for death among recipients of a biologic prosthesis, as compared with recipients of a mechanical valve, is plotted against age as a continuous variable (solid lines). Dashed lines represent the 95% confidence intervals that were obtained from bootstrap resampling. The horizontal line at 1.00 denotes no difference between valve types.

Figure 3.. Mortality after Mitral-Valve Replacement with a Biologic or Mechanical Prosthesis.

All-cause mortality is plotted against time after surgery and stratified according to age group. The group of patients who received a mechanical valve is the reference group. The numbers of patients at risk are included below each graph. Note that numbers are not necessarily integers owing to inverse probability weighting.