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.