Plaque imaging with CT-a comprehensive review on coronary CT angiography based risk assessment

Abstract

CT based technologies have evolved considerably in recent years. Coronary CT angiography (CTA) provides robust assessment of coronary artery disease (CAD). Early coronary CTA imaging-as a gate-keeper of invasive angiography-has focused on the presence of obstructive stenosis. Coronary CTA is currently the only non-invasive imaging modality for the evaluation of non-obstructive CAD, which has been shown to contribute to adverse cardiac events. Importantly, improved spatial resolution of CT scanners and novel image reconstruction algorithms enable the quantification and characterization of atherosclerotic plaques. State-of-the-art CT imaging can therefore reliably assess the extent of CAD and differentiate between various plaque features. Recent studies have demonstrated the incremental prognostic value of adverse plaque features over luminal stenosis. Comprehensive coronary plaque assessment holds potential to significantly improve individual risk assessment incorporating adverse plaque characteristics, the extent and severity of atherosclerotic plaque burden. As a result, several coronary CTA based composite risk scores have been proposed recently to determine patients at high risk for adverse events. Coronary CTA became a promising modality for the evaluation of functional significance of coronary lesions using CT derived fractional flow reserve (FFR-CT) and/or rest/dynamic myocardial CT perfusion. This could lead to substantial reduction in unnecessary invasive catheterization procedures and provide information on ischemic burden of CAD. Discordance between the degree of stenosis and ischemia has been recognized in clinical landmark trials using invasive FFR. Both lesion stenosis and composition are possibly related to myocardial ischemia. The evaluation of lesion-specific ischemia using combined functional and morphological plaque information could ultimately improve the diagnostic performance of CTA and thus patient care. In this review we aimed to summarize current evidence on comprehensive coronary artery plaque assessment using coronary CTA.

Keywords: Coronary CT angiography (coronary CTA); coronary artery disease (CAD); risk assessment.

Conflict of interest statement

Conflicts of Interest: The authors have no conflicts of interest to declare.

Figures

Figure 1

Representative images of plaque characteristics identifiable using coronary CT angiography (CTA).

Figure 2

Representative images of stenosis categories using coronary CT angiography (CTA).

Figure 3

Representative examples of plaque burdens and composite plaque scores. For the CONFIRM score both patients were assumed to be 65-year-old smoking male patients with 230 mg/dL total cholesterol, 47 mg/dL HDL, 142 mmHg systolic blood pressure using hypertension medication. For the SYNTAX score calculations, the LAD-LCX bifurcation was assumed to be ≥70˚ and all plaques were shorter than 20 mm. The example shows, that patients with very different degree of disease can have very similar plaque burden scores. Composite plaque burden scores on the other hand seem to better differentiate between the severity of coronary artery disease. D, diagonal; IM, intermediate branch; LAD, left anterior descending; LCX, left circumflex; PDA, posterior descending artery; PLB, posterolateral branch; OM, obtuse marginal; RCA, right coronary artery; prefixes: d, distal; m, mid; p, proximal.