Variation in hospital mortality rates for patients with acute myocardial infarction

Hospitals vary by twofold in their hospital-specific 30-day risk-stratified mortality rates (RSMRs) for Medicare beneficiaries with acute myocardial infarction (AMI). However, we lack a comprehensive investigation of hospital characteristics associated with 30-day RSMRs and the degree to which the variation in 30-day RSMRs is accounted for by these characteristics, including the socioeconomic status (SES) profile of hospital patient populations. We conducted a cross-sectional national study of hospitals with ≥15 AMI discharges from July 1, 2005 to June 20, 2008. We estimated a multivariable weighted regression using Medicare claims data for hospital-specific 30-day RSMRs, American Hospital Association Survey of Hospitals for hospital characteristics, and the United States Census data reported by Neilsen Claritas, Inc., for zip-code level estimates of SES status. Analysis included 2,908 hospitals with 513,202 AMI discharges. Mean hospital 30-day RSMR was 16.5% (SD 1.7 percentage points). Our multivariable model explained 17.1% of the variation in hospital-specific 30-day RSMRs. Teaching status, number of hospital beds, AMI volume, cardiac facilities available, urban/rural location, geographic region, ownership type, and SES profile of patients were significantly (p < 0.05) associated with 30-day RSMRs. In conclusion, substantial variation in hospital outcomes for patients with AMI remains unexplained by measurements of hospital characteristics including SES patient profile.