Background: Coronary angiograms are important in the diagnostic workup of patients with suspected coronary artery disease. However, little is known about the clinical predictors of normal angiograms and whether this rate varies across different cardiac centers in Ontario.
Methods: We conducted a study using the Cardiac Care Network Variations in Revascularization Practice in Ontario database of 2,718 patients undergoing an index cardiac catheterization for an indication of stable angina between April 2006 and March 2007 at one of 17 cardiac hospitals in Ontario. We determined predictors of normal coronary angiograms (0% coronary stenosis) and compared rates of patients with normal catheterizations across centers.
Results: Overall, 41.9% of patients with stable angina had a normal catheterization. A multivariate model demonstrated female gender to be the strongest predictor of a normal angiogram (odds ratio 3.55, 95% CI 2.93-4.28). In addition, atypical ischemic symptoms or no symptoms, the absence of diabetes, hyperlipidemia, smoking history, peripheral vascular disease, and angiography performed at a nonteaching site were associated with higher rates of normal catheterization. The rate of normal angiograms studied varied from 18.4% to 76.9% across hospitals and was more common in community compared with academic settings (47.1% vs 35.4%, P < .001).
Conclusions: The absence of traditional cardiac risk factors, female gender, and lack of typical angina symptoms are all associated with a higher frequency of normal cardiac catheterizations. The wide variation in Ontario in the frequency of normal angiograms in patients with stable angina suggests that there are opportunities to improve patient case selection.
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