Hospital variation in mortality after first acute myocardial infarction in Denmark from 1995 to 2002: lower short-term and 1-year mortality in high-volume and specialized hospitals

BACKGROUND: This study used linked data from the National Hospital Registry to determine the factors that contribute to differences between hospitals in all-cause mortality after first acute myocardial infarction (AMI) between 1995 and 2002.

METHODS: The study included 64,321 patients with their first admission for AMI between 1995 and 2002 and surviving the day of admission. Multilevel logistic regression was used to determine the relationships between regional and hospital characteristics and 28-day and 365-day mortality after adjusting for individual characteristics, period, and medical history.

RESULTS: Tertiary cardiac care centers (odds ratio [OR], 0.80; 95% confidence interval [CI], 0.67-0.96) and main regional hospitals (OR, 0.90; 95% CI, 0.80-0.99) had improved 28-day mortality compared with local hospitals. A 2-fold increase in annual total MI volume decreased 28-day mortality (OR, 0.91; 95% CI, 0.87-0.94) and 365-day mortality (OR, 0.95; 95% CI, 0.91-0.98). Differences between hospitals were more substantial for short-term mortality, such that patients were about twice as likely to die within 28 days in hospitals with the worst performance versus those with the best performance. Higher regional AMI incidence was associated with lower mortality before 2000; this disappeared after 2000. Other regional contextual characteristics had very modest effects on mortality.

CONCLUSIONS: Type of hospital, and especially total MI volume at the hospital level, were significantly associated with mortality after AMI. Individual hospitals varied substantially in both short- and long-term mortality.