CONTEXT: Medicare has a legislative mandate for quality assurance, but the effectiveness of its population-based quality improvement programs has been difficult to establish.

OBJECTIVE: To improve the quality of care for Medicare patients with acute myocardial infarction.

DESIGN: Quality improvement project with baseline measurement, feedback, remeasurement, and comparison samples.

SETTING: All acute care hospitals in the United States.

PATIENTS: Preintervention and postintervention samples included all Medicare patients in Alabama, Connecticut, Iowa, and Wisconsin discharged with principal diagnoses of acute myocardial infarctions during 2 periods, June 1992 through December 1992 and August 1995 through November 1995. Indicator comparisons were made with a random sample of Medicare patients in the rest of the nation discharged with acute myocardial infarctions from August 1995 through November 1995. Mortality comparisons involved all Medicare patients nationwide with inpatient claims for acute myocardial infarctions during 2 periods, June 1992 through May 1993 and August 1995 through July 1996.

INTERVENTION: Data feedback by peer review organizations.

MAIN OUTCOME MEASURES: Quality indicators derived from clinical practice guidelines, length of stay, and mortality.

RESULTS: Performance on all quality indicators improved significantly in the 4 pilot states. Administration of aspirin during hospitalization in patients without contraindications improved from 84% to 90% (P< .001), and prescription of beta-blockers at discharge improved from 47% to 68% (P < .001). Mortality at 30 days decreased from 18.9% to 17.1% (P = .005) and at 1 year from 32.3% to 29.6% (P < .001). These improvements in quality occurred during a period when median length of stay decreased from 8 days to 6 days. Performance on all quality indicators except reperfusion was better in the pilot states than in the rest of the nation in 1995, and the differences were statistically significant for aspirin use at discharge (P < .001), beta-blocker use (P < .001), and smoking cessation counseling (P = .02). Postinfarction mortality was not significantly different between the pilot states and the rest of the nation during the baseline period, although it was slightly but significantly better in the pilot states during the follow-up period (absolute mortality difference at 1 year, 0.9%; P = .004).

CONCLUSIONS: The quality of care for Medicare patients with acute myocardial infarction has improved in the Cooperative Cardiovascular Project pilot states. Performance on the defined quality indicators appeared to be better in the pilot states than in the rest of the nation in 1995 and was associated with reduced mortality.