Coronary CT Angiography Findings in Patients with Ambiguous Left Main Coronary Artery Disease

Left main coronary artery (LMCA) stenosis is a high risk subset of coronary artery disease; however, its occurrence may be misjudged by coronary angiography. Coronary CT angiography (CCTA) was performed on 5 patients with clinically highly suspicious and angiographically borderline LMCA disease (ostial: 3 patients, mid: 1 patient and distal: 1 patient). A cross-sectional CCTA image was used to calculate the diameter stenosis. The quantitative coronary angiography (QCA) reference diameter (RD) correlated well with CCTA RD in all 5 patients. However, the lesion site minimal lumen diameter (MLD) by QCA correlated less well with that obtained by CCTA. The grade of stenosis measured by CCTA was significantly lower than that measured by QCA. Morphologically, three patients had LMCA ostial angulation (with minimal atheromatous changes), one patient had a biconcave configuration of the LMCA (with normal vessel wall) and one other had a tapering-morphology of the LMCA (with minimal atheromatous changes). In conclusion, CCTA may have a complementary diagnostic role in patients with angiographically ambiguous or inconclusive LMCA lesions and therefore it should be considered in the assessment of selected patients before they undergo coronary bypass surgery. In order to validate CCTA for main stem stenosis a proper gold standard, such as IVUS, is required.