Purpose: The aim of this study was to compare outcomes after acute myocardial infarction between regions with low and high catheterization access.
Methods: Observational study using administrative databases of patients with acute myocardial infarction in provinces with low (Ontario) and high (Quebec and British Colombia) access to invasive cardiac procedures (ICP, n = 141718). Using instrumental variables to control for confounding, effectiveness of treatment was measured on 1-year mortality among marginal patients (patients for whom treatment is discretionary and highly dependent on access to ICP).
Results: The ICP approach was associated with overall decreased mortality (-11%, 95% CI -13% to -8%) with statistically significant reductions in low-access regions (-16%, 95% CI -21% to -10%). High-access regions (QC -8%, 95% CI -19% to 4%) (BC -2%, 95% CI -12% to 7%) exhibited smaller marginal benefits.
Conclusion: The invasive approach benefits all marginal patients, with greater benefits in regions of lower access, indicating a threshold of availability above which further mortality benefits are negligible.