Prevalence of obstructive coronary artery disease in an outpatient cardiac CT angiography environment

Abstract

Purpose To determine the prevalence of significant obstructive disease and non-diagnostic studies using coronary computed tomographic angiography (CTA) in an outpatient environment, to establish if CTA could help avoid unnecessary diagnostic cardiac catheterizations. Methods We evaluated all cases consecutively performed in our outpatient CTA laboratory seen over one year with an indication that could warrant a cardiac catheterization to establish the presence or absence of coronary artery disease (CAD). Excluded were patients without established indications for cardiac catheterization and those with known CAD (i.e.— prior myocardial infarction, revascularization). Four hundred and ninety-three (493) CTA case studies were included for the analysis. Patients were classified as normal (no luminal irregularities seen), non-obstructive coronary disease (< 50% stenosis), significant obstructive coronary disease (> 50% stenosis), or a non-diagnostic study. We assumed that all patients assigned to the obstructive CAD group and the non-diagnostic study group would require a cardiac catheterization. In the remaining two groups, a cardiac catheterization would not be necessary for diagnosis or treatment. Results Of the 493 index cases evaluated, 157 (32%) cases were reported to be normal, 204 patients were classified as having non-obstructive disease (41%), 93 patients were defined to have obstructive CAD (19%), and 39 cases were inconclusive (8%). Thus, in 27% of the study population, a conventional coronary angiography would be indicated to clarify the diagnosis or provide definitive disease severity for subsequent revascularization. Conclusion Among ambulatory patients referred for CT angiography with symptoms or positive (or equivocal) cardiac stress tests, 73% of patients were found to have either normal coronary arteries or non-obstructive disease. Given the high negative predictive power of cardiac CTA (93–99%), these patients most likely would not require subsequent invasive coronary angiography. A strategy of selective cardiac catheterization may substantially decrease unnecessary diagnostic cardiac catheterizations and reduce health care expenses.