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Coronary angiography exposes patients to procedural risks and substantial radiation; most would agree that we should avoid the procedure in patients who are unlikely to require further intervention. To find out how often patients referred for elective coronary angiography are found not to have obstructive coronary artery disease (CAD), investigators for the CathPCI Registry of the National Cardiovascular Data Registry assessed the diagnostic yield (prevalence of obstructive CAD) at 663 participating sites. Obstructive CAD was defined as ≥50% stenosis of the left main coronary artery or ≥70% stenosis of a major epicardial or branch vessel.
Of patients who underwent elective diagnostic catheterization (about 20% of all procedures), 38% had obstructive CAD. If the definition of obstructive CAD was expanded to ≥50% stenosis in any vessel, the prevalence increased to only 41%. An increase in diagnostic yield from 2004 (36.8%) to 2008 (38.8%) was significant but very small. Almost 70% of the patients undergoing elective coronary angiography had positive findings on resting electrocardiography, echocardiography, computed tomography, or stress testing; however, these data were only available as a composite.
Patel MR et al. Low diagnostic yield of elective coronary angiography. N Engl J Med 2010 Mar 11; 362:886.
Brenner DJ. Medical imaging in the 21st century — Getting the best bang for the rad. N Engl J Med 2010 Mar 11; 362:943.
Comment
In this national study, the diagnostic yield of elective coronary angiography was remarkably low: only 38%. However, an angiogram's results do not tell us whether it was appropriately ordered. Because the noninvasive testing variable included a wide range of procedures — from resting electrocardiography to stress testing — we cannot speculate from the data how many catheterizations could have been avoided. Nonetheless, these results suggest room for improvement and underscore the importance of implementing evidence-based appropriateness criteria for coronary angiography.