Regional variation in cardiac catheterization appropriateness and baseline risk after acute myocardial infarction

Abstract

Objectives: We evaluated whether appropriateness and baseline risk of cardiac catheterization varied according to regional intensity of invasive therapy after acute myocardial infarction (AMI), and whether AMI mortality varied according to invasive intensity regions.

Background: Marked regional variations exist in cardiac invasive procedure use after AMI within the U.S.

Methods: We performed an analysis of 44,639 Medicare fee-for-service beneficiaries hospitalized with AMI between 1998 and 2001. Invasive procedure intensity was determined based on overall cardiac catheterization rates for Medicare enrollees. Cardiac catheterization appropriateness was determined by the American College of Cardiology/American Heart Association classification and baseline risk was estimated using the GRACE (Global Registry of Acute Coronary Events) risk score. The primary outcomes of the study were cardiac catheterization use within 60 days and 3-year mortality after hospital admission.

Results: Higher invasive intensity regions were more likely to perform cardiac catheterizations on class I patients (appropriate) (RR 1.38, 95% confidence interval [CI] 1.27 to 1.48), class II patients (equivocal) (RR 1.42, 95% CI 1.31 to 1.53), and class III patients (inappropriate) (RR 1.29, 95% 0.97 to 1.67) compared with low-intensity regions after adjusting for patient and physician characteristics. The overall cardiac catheterization use was 5.2% lower for each increase in GRACE risk decile, and this relationship was observed similarly in all regions. Risk-standardized mortality rates of AMI patients at 3 years were not substantially different between regions.

Conclusions: Although higher-risk patients and those with more appropriate indications may have the most to benefit from an invasive strategy after AMI, we found that higher-invasive regions do not differentiate procedure selection based on the patients' appropriateness or their baseline risks.