Understanding individual and small area variation in the underuse of coronary angiography following acute myocardial infarction

BACKGROUND. Underuse of coronary angiography is common among patients with acute myocardial infarction (AMI) and the magnitude of underuse varies across geographic areas. OBJECTIVES. To examine the influence of patient demographic, clinical and hospital characteristics on underuse of coronary angiography, and the contribution of these factors to variation in underuse across geographic regions. RESEARCH DESIGN. Cohort study using data from the Cooperative Cardiovascular Project. SUBJECTS. Nine thousand four hundred fifty-eight patients in 95 hospital referral regions (HRRs) hospitalized for AMI in 1994 to 1995 and for whom angiography was rated necessary. MEASURES. Odds ratios (95% confidence intervals) associated with underuse of angiography according to patient and hospital characteristics. The difference between low and high rates of underuse of angiography across regions after controlling for regional differences in patient and hospital characteristics. RESULTS. Of those for whom angiography was rated necessary, 42% did not undergo the procedure. Underuse of angiography was associated with several patient demographic and hospital attributes (eg, female gender, black race, treatment in a hospital without angiography, treatment by a general practitioner) as well as with prevalent clinical characteristics, such as renal insufficiency, congestive heart failure, prior coronary artery bypass surgery, and chronic obstructive pulmonary disease. Across HRRs, variation in underuse ranged from 24.0% to 58.3%. The difference between low and high rates did not decline significantly after controlling for regional differences in patient or hospital characteristics. CONCLUSIONS. At the patient-level, rates of necessary angiography may be improved if we address disparities in care related to sociodemographic characteristics and to the technological capabilities of hospitals. In addition, practice guidelines should be updated to reflect clinical concerns about the risks and benefits of angiography and subsequent revascularization in certain patient sub-groups, both to provide appropriate guidance to physicians and to facilitate better estimates of underuse. The causes of regional variation in underuse do not appear to be related to regional differences in patient or hospital characteristics, and therefore, require further study.