Incremental detection of coronary artery disease by assessment of non-calcified plaque on coronary CT angiography

AIM: The purpose of this study was to evaluate the improved assessment of coronary atherosclerotic plaque burden by measurement of non-calcified plaque in addition to calcified plaque using CT coronary angiography (CTA). MATERIALS AND METHODS: Low to intermediate-risk outpatients with suspected coronary artery disease were prospectively recruited. Patients underwent CTA and calcium scoring in addition to invasive angiography. The presence of plaque (calcified, non-calcified, and mixed) was analysed on a per segment basis (percentage of segments with disease) with stratification by calcium score (CS). RESULTS: Seventy-six patients were enrolled of whom 30 had a CS of 0, 26 had a CS of 1-200, and 20 had a CS of >200. One thousand, one hundred and two segments were analysed using CTA and invasive angiography. The prevalence of segments with calcified or mixed plaque was 3.1% (n = 13) for a CS of 0, 15.1% (n = 57) for a CS of 1-200, and 50% (n = 142) for a CS of >200 (all p < 0.0001). The proportion of segments with non-calcified plaque alone was low and similar among the three groups: 5.4% (n = 23; CS = 0), 8.2% (n = 32; CS = 1-200), and 8.6% (n = 25; CS = >200), (CS = 0 versus CS = >200; p = 0.04, others p = ns). The relative increase in diseased segments by additional assessment of non-calcified plaque was greatest for patients with a CS of 0 (173%) versus a CS of 1-200 (55%), and a CS of >200 (17%). CONCLUSION: CTA offers increased relative incremental detection of non-calcified plaque, particularly in those with negative CS; however, the absolute detection of non-calcified plaque in those with negative CS is low. The prognostic significance of non-calcified plaque for the prediction of cardiac events, particularly in patients with low CS, requires continued study. (C) 2008 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.