A meta-analysis of the performance of small tissue versus mechanical aortic valve prostheses

Small aortic prosthetic valves have been associated with suboptimal performance due to patient-prosthesis mismatch (PPM). This meta-analysis compared the outcomes of patients with a small root who received tissue versus mechanical aortic valves.

A systematic literature review identified 7 candidate studies; of these, 5 met the meta-analysis criteria. We analysed outcomes for a total of 680 patients (227 tissue valves and 453 mechanical valves) using random effects modelling. Each study was assessed for heterogeneity and quality. The primary end point was mortality at follow-up. Secondary end points included intraoperative and postoperative outcomes, the rate of PPM and left ventricle mass regression and major cardiac and prosthesis-related adverse events at follow-up.

There was no between-group difference in mortality at follow-up [incidence rate ratio 1, 95% confidence interval (CI) 0.50-2.01; P = 0.99]. The tissue group had a higher rate of PPM (odds ratio 17.19, 95% CI 8.6-25.78; P = 0.002) and significantly less reduction in ventricular mass (weighted mean difference 40.79, 95% CI 4.62-76.96; P = 0.02). There were no significant differences in the incidence of structural valve disease at follow-up compared to that in the mechanical valve group. There was also no between-group difference in aggregated adverse events at follow-up (P = 0.68).

Tissue and mechanical valves were associated with similar mortality rates; however, patients receiving tissue valves had a higher rate of PPM and significantly less left ventricle mass regression. These findings indicate that patients receiving small tissue valves may require closer clinical surveillance than those receiving mechanical valves.