Does size matter? The impact of caseload and expertise concentration on AMI 30-day mortality-A comparison across 10 OECD countries.

Objective: To examine the variability of hospital performance within and across countries, using 30-day acute myocardial infarction (AMI) mortality, and to study the impact of hospital characteristics on performance.

Study Setting: Hospital-level adjusted risk standardized mortality rates (RSMR) and hospital characteristics were collected from 10 OECD and two collaborating countries including 1,163 hospitals.

Study Design: Associations between RSMR and hospital characteristics were studied using univariate and multivariate linear regressions. Clusters of hospitals were created using hierarchical clustering and mortality compared using linear regression.

Findings: Wide variation between countries was found for RSMR and hospital characteristics. Regression models showed large country effects. A high volume of AMI admission was associated with lower RSMR in a model using a restricted number of hospital characteristics (-0.83, p < 0.001) but not in a model using all characteristics (-1.03, p = 0.06). Analysis within countries supported this association. Hospital clusters showed clear differences in characteristic distributions but no difference in RSMR.

Conclusions: The effect of volume may support policies toward a concentration of services within the hospital sector. The effect of other hospital characteristics was inconclusive and suggests the importance of system-wide characteristics or pathways of care (i.e. timeliness and nature of initial response and during transportation to a hospital, transfers between hospitals, post-discharge organization) in explaining variation.