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.