Serial photon-counting CCTA reveals the natural history of high-risk plaques in patients after ACS

Background High-risk plaque (HRP) in non-culprit arteries confers future risk of acute coronary syndrome (ACS), yet plaque phenotype is dynamic and potentially modifiable with optimal medical therapy. Photon-counting coronary computed tomography angiography (CCTA), with superior spatial resolution compared with conventional CT, may allow improved identification and longitudinal assessment of HRP. Purpose To use serial photon-counting CCTA to 1) to determine the prevalence of HRP in patients with symptomatic CAD, 2) to define the natural history of HRP on clinician-directed care, 3) to investigate clinical factors that associate with HRP, and 4) assess whether dynamic HRP changes associate with changes in quantitative plaque burdens. Methods 100 patients underwent clinically-indicated invasive coronary angiography followed by serial photon-counting CCTA within 30 days and at 12-months as part of a prospective multicentre research study. Residual coronary lesions were analysed for the four HRP features: positive remodelling, low-attenuation plaque, spotty calcification, and napkin-ring sign (Figure 1A-D). Plaque volume quantification was performed using artificial-intelligence-enabled software (Autoplaque v3.0). Results In this high-risk cohort with median age 62 years, 85% of participants had a recent ACS and 79% underwent stenting, while 64% had residual lesions causing obstructive (≥50%) stenosis. At baseline, 94% had at least one HRP feature across the whole coronary tree and 51% at least one HRP containing ≥2 high-risk plaque characteristics in the same lesion. Conventional cardiovascular risk factors and baseline LDL-cholesterol did not differentiate patients with high-risk plaques from those without. Over follow-up, 88% of patients were on a high-intensity statin with median LDL-cholesterol reducing from 2.7 mmol/L (IQR 1.9, 3.2) to 1.4 mmol/L (IQR 1.1, 1.8). HRP prevalence did not change (51% vs 45%, P=0.40) (Figure 2A), although there was a decrease in the frequency of low-attenuation plaque (63% vs 56%, P=0.0005) (Figure 2B). Persistent HRP features were more abundant in patients who did not reach LDL-cholesterol <1.4mmol/L (median number 4.5 [IQR 2.0-6.0] vs 3 [IQR 1.0-5.0], P=0.03) (Figure 2C) and remained more common in those with residual obstructive stenoses (99% vs 84%, P=0.012) (Figure 2D). HRP presence did not associate with progression of total plaque burden (Figure 2E). Serial photon-counting provided high-resolution images for tracking HRP (example in Figure 3). Conclusions HRP features are prevalent in residual plaques post-ACS. Intensive lipid-lowering is associated with a more favourable plaque-phenotype. Obstructive stenosis associates with HRP persistence. This demonstrates a need for more personalised anti-atherosclerotic treatment, and a potential role for serial photon-counting CCTA to monitor HRP morphology in patients with established CAD.picture 1picture 2