The presence of lipid-rich, necrotic core (LC) in coronary arterial wall is known to denote a high risk of rupture, resulting in acute coronary syndrome (ACS). The purpose of this study is to know whether ECG-gated cardiac CT can detect LC in comparison with intravascular ultrasound (IVUS).

Thirty two patients with coronary artery disease (21 ACS, 11 stable angina) and heart rate less than 66/min, who had underwent both ECG-gated cardiac CT and IVUS of three major coronary arteries, were included (M:F=26:6, mean age=55 yrs). ECG-gated contrast-enhanced cardiac CT was performed using a 16-slice spiral CT scanner (Sensation 16, Siemens). Images were reconstructed with a slice thickness of 1mm and interval of 0.3mm in mid-diastolic phase with a soft tissue kernel (B10f). FOV was adjusted to cover each major coronary vessel with maximum in-slice resolution. Cross sectional MPR images, perpendicular to the course of each vessel were generated in 0.2mm interval. Using this cross sectional MRP images, two radiologists, who were blind to the IVUS result, were request to detect the well-defined area with low attenuation less than 60 HU in coronary arterial wall, which is larger than 3mm². The result was compared with IVUS study. 10 segment-model was used to assess the three major coronary arteries and left main coronary artery. Interobserver agreement was evaluated.

231 coronary arterial segments were evaluated. 53 segments were excluded in the assessment; 36 segments due to poor enhancement or severe motion artifact on CT, 17 segments due to failure of IVUS study. IVUS detected 13 LCs with significant coronary stenosis and 9 LCs with minimal luminal narrowing. The sensitivity (and 95% confidence intervals) of CT for the two readers were 73% (52-87%) and 68% (47-84%), respectively. The specificity were 92% (87-95%) and 90% (85-93%). Interobserver agreement was good (kappa 0.608). Ten concordant false positive lesions between two readers on CT may be attributable to IVUS-misdiagnosed true LCs or errors of CT attenuation.

ECG-gated cardiac CT may be used as a noninvasive tool to detect vulnerable, lipid-rich, necrotic core in coronary arterial wall.