Variations in the management of acute myocardial infarction. Importance of clinical measures of disease severity

Abstract

Objective: To determine the extent to which resource use for patients hospitalized with acute myocardial infarction varies with clinical status, and to see if an observed difference in resource use between two states can be explained by clinically detailed risk adjustment.

Design: Retrospective review of the clinical characteristics and resource use of 342 patients hospitalised in two states with acute myocardial infarction.

Data sources: Merged data from three sources: a large, existing research database used in developing the Medicare Mortality Predictor Score, clinical data abstracted from medical charts specifically for this study, and Medicare Parts A and B claims records.

Patients: A probability sample of Medicare patients hospitalized in 1986 with a diagnosis of acute myocardial infarction and residing in either Wisconsin or Washington state; patients dying within 30 days are oversampled.

Measurements and main results: Although patients were clinically similar in the two states, there were systematic differences in resource use. Patients in Wisconsin spent more than one extra day in the intensive care unit (ICU) (2.8 vs 1.7) as well as more than one extra non-ICU day in the hospital (8.0 vs 6.5) than patients in Washington. Patients in Wisconsin were also more likely to receive an echocardiogram (35.6% vs 15.8%), nuclear ventriculogram (12.8% vs 4.1%), exercise tolerance test (21.5% vs 3.4), and Holter monitoring (5.4% vs 0%). (All p < .01.) Differences in utilization were greater for patients at lower risk of dying. The average cost of care was 20.8% higher in Wisconsin (p = .01); risk adjustment for clinical and other factors reduced this difference to 11.8%, but did not eliminate it (p = .04).

Conclusions: Patients with acute myocardial infarction vary in resource use as a function of clinical factors present at admission and occurring during the hospital stay; comparisons that do not take account of these factors may not discriminate well between providers who care for sicker patients and those who are inefficient. The greater use of resources for patients in Wisconsin is at least partially explained by differences in clinical characteristics that are not presently captured in administrative data.