When stress testing yields an ambiguous or indeterminate result in a patient with a high likelihood of CAD, coronary angiography may be preferable to another noninvasive test and may be the most effective means to reach a diagnosis. The frequency with which coronary angiography is per- formed varies across geographic regions, and in some areas it may be underutilized or overutilized.34 The optimal rate of normal coronary angiography in clinical practice remains undefined. In the ACC s National Cardiovascular Data Registry CathPCI Registry, approximately 45% of elective cardiac catheterizations performed at hospitals did not detect clinically significant (defined as >50% luminal diameter) although rates varied markedly between hospi- tals (ie, range, 0% to 77%).35 Hospitals with lower rates of significant CAD at catheterization were more likely to have performed angiography on younger patients; those with no Fihn et al 2014 Stable Ischemic Heart Disease Focused Update 1755 symptoms or atypical symptoms; and those with negative, equivocal, or unperformed functional status assessment.35 Even among those with a positive result on a noninvasive test, only 41% of patients were found to have significant CAD.36 In a study performed within the Veterans Health Administration, 21% of patients undergoing elective catheterization had nor- mal coronary arteries (defined as having no lesions 20%). The median proportion of normal coronary arteries was 10.8% among hospitals in the lowest quartile and 30.3% among hos- pitals in the highest quartile.37 The authors concluded that factors causing variation in patient selection for coronary angiography exist in integrated non fee-for-service health systems as well as in fee-for-service systems. Angiographically normal or near-normal coronary arteries are more common among women, who are more likely than men to have myocardial ischemia due to microvascular dis- ease. 