Regional disparities in surgical learning curves and maturity for congenital heart surgery in Brazil’s public health system: when volume is not enough

Abstract Background The volume-outcome relationship in congenital heart surgery is established, but its validity in systems with extreme regional inequalities is unclear. This study assessed whether cumulative volume alone reduces mortality for atrial septal defect (ASD) and ventricular septal defect (VSD) repairs across Brazil’s macro-regions or if structural barriers limit improvement. Methods Nationwide cohort of 48,721 ASD and VSD repairs in Brazil’s public health system (SUS), 2008–2024. Regional learning curves were modeled using non-linear smoothing of in-hospital mortality against cumulative volume. A composite Surgical Maturity Index (IMS) integrated experience and outcome stability. Results Procedure volume was highly unequal (Southeast 44%). Mortality ranged 1.4–4.0% (ASD) and 5.8–14.0% (VSD). High-capacity regions achieved < 2% mortality after 1800–3200 cases and continued improving. Constrained regions plateaued above 2% despite > 3000 cases (interaction p = 0.004). IMS strongly correlated with lower mortality ( ρ = − 0.89). The Northeast showed rapid VSD maturity gains (+ 15.2% annual change, p = 0.001) via quality-improvement partnerships. Conclusions Systemic constraints impose a ceiling on volume-driven improvement. Targeted capability transfer accelerates maturity more effectively than volume centralization alone, informing equitable policy in public health systems.