Transatlantic similarities and differences in major natural history endpoints of heart failure after acute myocardial infarction: a propensity-matched study of the EPHESUS trial.

BACKGROUND: Transatlantic differences in outcomes in heart failure after acute myocardial infarction (AMI) have not been examined in propensity-matched studies.
METHODS: In the Eplerenone Post-Acute Myocardial Infarction Heart Failure Efficacy and Survival Study (EPHESUS), there were significant imbalances in baseline characteristics between patients from North America (n=858) and Europe (n=4646). Propensity scores for North America, calculated for each patient using 64 baseline characteristics, were used to assemble 298 pairs of patients who were well balanced on all measured baseline characteristics. Matched Cox regression models were used to estimate transatlantic differences in outcomes.
RESULTS: There was no transatlantic difference in all-cause mortality during 16 months of mean follow-up of (matched hazard ratio {HR}, 1.00; 95% confidence interval {CI}, 0.64-1.57; P=1.000). All-cause hospitalization occurred in 175 (rate, 8974/10,000 person-years) and 137 (rate, 5249/10,000 person-years) patients respectively from North America and Europe (matched HR when North America was compared with Europe, 1.89; 95% CI, 1.41-2.52; P<0.0001). Matched HRs (95% CIs) for cardiovascular and non-cardiovascular hospitalization for North America were respectively 1.35 (0.92-1.97; P=0.125) and 1.89 (1.31-2.72; P<0.0001). Among 5504 pre-match patients, unadjusted, multivariable-adjusted, and propensity-adjusted HRs for all-cause hospitalization for North America were 1.52 (95% CI, 1.38-1.68; P<0.0001), 1.16 (95% CI, 1.02-1.31; P=0.020), 1.41 (95% CI, 1.17-1.70; P<0.0001).
CONCLUSION: Despite major transatlantic differences in baseline characteristics, there was no difference in post-AMI mortality. The increased non-cardiovascular hospitalization in North America may in part be due to transatlantic differences in patient preferences and access to care. Published by Elsevier Ireland Ltd.