Clinical and Haemodynamic Outcomes in Small Versus Large Prostheses in Surgical Aortic Valve Replacement: A Systematic Review and Meta-Analysis

Objectives: This systematic review and meta-analysis evaluate clinical and haemodynamic outcomes between small (<= 21 mm) and large (>= 23 mm) prosthetic valves in surgical aortic valve replacement (SAVR). Methods: A comprehensive literature search was conducted from inception to March 2025. Studies comparing outcomes between small and large aortic valve prostheses were included. Primary outcome was all-cause mortality. Secondary outcomes included short-term mortality, stroke, reoperation, endocarditis, haemodynamic parameters and patient-prosthesis mismatch (PPM). Random-effects models calculated pooled risk ratios (RRs) or mean differences (MDs). Mediation analysis explored the relationships between prosthesis size, PPM and mortality. Results: Twelve studies comprising 9896 patients were included. Small prostheses were associated with increased all-cause mortality (RR 1.23, 95% CI 1.07-1.41, p = 0.004) and short-term mortality (RR 1.73, 95% CI 1.11-2.68, p = 0.015). No significant differences were observed for stroke, reoperation or endocarditis. Small prostheses demonstrated significantly lower indexed effective orifice area (MD -0.13 cm(2)/m(2), 95% CI -0.24 to -0.01, p = 0.030) and higher incidence of PPM (RR 2.02, 95% CI 1.36-3.00, p < 0.0001). Mediation analysis revealed a strong correlation (r = 0.904) between PPM and all-cause mortality effect sizes. Very small prostheses (< 19 mm) exhibited elevated mean gradients (20.8 mmHg) and substantial PPM incidence (33.2%). Conclusions: Small aortic valve prostheses are associated with increased mortality and PPM. The strong correlation between PPM and mortality effects suggests PPM may be the key mechanism underlying adverse outcomes. Alternative strategies such as root enlargement may be warranted in patients requiring small prostheses.