International differences in in-hospital revascularization and outcomes following acute myocardial infarction A multilevel analysis of patients in ASSENT-2

BACKGROUND: Revascularization rates vary substantially between countries in patients with acute ST-elevation myocardial infarction (STEMI). The impact of early revascularization on clinical outcomes in such patients remains uncertain. The ASSENT-2 fibrinolytic trial provides the opportunity to compare revascularization rates following STEMI in patients across 29 countries, and to explore the relationship between revascularization and clinical outcome. METHODS: Countries participating in ASSENT-2 were grouped into tertiles according to their in-hospital revascularization rates (39%). Baseline characteristics, medication and procedure use, and clinical outcomes of the 16949 patients enrolled were compared. Multiple Cox regressions were used to assess the relationship between the tertiles and 30-day mortality, the primary endpoint of the ASSENT-2 trial. Multilevel logistic regression models were developed to validate and further extend the findings from the single-level analyses. RESULTS: Patients in highest tertile countries were younger, heavier, and more often diabetic or hypertensive. They were more likely to have had a previous myocardial infarction or revascularization procedure. Time to treatment and hospital length of stay were shorter in the highest tertile, and beta-blocker use was more frequent. Stroke rates were low and similar across tertiles, with no statistically significant difference in rates of intracranial haemorrhage. Recurrent ischaemia and reinfarction were less common in the highest tertile. Mortality rates at 30 days were lower for countries with the highest revascularization rates (5.1% vs 6.9% vs 6.5% for the lower two tertiles, P<0.001). At 1 year, mortality remained significantly lower in the highest tertile countries (8.4% vs 10.6% vs 9.9%, P=0.001). Following adjustment for baseline patient characteristics, Cox regression analysis confirmed an excess of 30-day and 1-year mortality in the lowest and intermediate tertiles compared to the highest tertile. The multilevel analyses validated these findings, and demonstrated that a country's life expectancy and the hospital volume were inversely related to both 30-day and 1-year mortality. CONCLUSIONS: The highest rate of in-hospital revascularization following fibrinolytic therapy for acute myocardial infarction in this international study was associated with a reduction in recurrent ischaemia, reinfarction, and improved survival at both 30 days and at 1 year. The optimal rates of revascularization in this setting remain to be determined.