Reduction in acute myocardial infarction mortality in the United States: risk-standardized mortality rates from 1995-2006

Abstract

Context: During the last 2 decades, health care professional, consumer, and payer organizations have sought to improve outcomes for patients hospitalized with acute myocardial infarction (AMI). However, little has been reported about improvements in hospital short-term mortality rates or reductions in between-hospital variation in short-term mortality rates.

Objective: To estimate hospital-level 30-day risk-standardized mortality rates (RSMRs) for patients discharged with AMI.

Design, setting, and patients: Observational study using administrative data and a validated risk model to evaluate 3,195,672 discharges in 2,755,370 patients discharged from nonfederal acute care hospitals in the United States between January 1, 1995, and December 31, 2006. Patients were 65 years or older (mean, 78 years) and had at least a 12-month history of fee-for-service enrollment prior to the index hospitalization. Patients discharged alive within 1 day of an admission not against medical advice were excluded, because it is unlikely that these patients had sustained an AMI.

Main outcome measure: Hospital-specific 30-day all-cause RSMR.

Results: At the patient level, the odds of dying within 30 days of admission if treated at a hospital 1 SD above the national average relative to that if treated at a hospital 1 SD below the national average were 1.63 (95% CI, 1.60-1.65) in 1995 and 1.56 (95% CI, 1.53-1.60) in 2006. In terms of hospital-specific RSMRs, a decrease from 18.8% in 1995 to 15.8% in 2006 was observed (odds ratio, 0.76; 95% CI, 0.75-0.77). A reduction in between-hospital heterogeneity in the RSMRs was also observed: the coefficient of variation decreased from 11.2% in 1995 to 10.8%, the interquartile range from 2.8% to 2.1%, and the between-hospital variance from 4.4% to 2.9%.

Conclusion: Between 1995 and 2006, the risk-standardized hospital mortality rate for Medicare patients discharged with AMI showed a significant decrease, as did between-hospital variation.

Figures

Figure

Change in Acute Myocardial Infarction 30-Day All-Cause Risk-Standardized Mortality From 1995 to 2006 Mean risk-standardized mortality rates were 18.8% (SD, 2.1%; range, 10.4%-27.5%) in 1995 and 15.8% (SD, 1.7%; range, 10.6%-21.6%) in 2006. The size of each bin reflects the number of hospitals that filled in a particular interval of risk-standardized mortality rate as well as the distributions (ranges) of rates in 1995 and 2006. Because the number of bins in each year is the same (n=35), the 1995 bin is wider than the 2006 bin to reflect the change in risk-standardized mortality rate distributions.