CT angiographic features of symptom-producing plaque in moderate-grade carotid artery stenosis

Abstract

Background and purpose: Emerging evidence indicates that plaque imaging can improve stroke risk stratification in patients with carotid artery atherosclerosis. We studied the association between soft and hard (calcified) plaque thickness measurements on CTA and symptomatic disease status (ipsilateral stroke or TIA) in patients with moderate-grade carotid artery stenosis.

Materials and methods: We measured soft-plaque and hard-plaque thickness on CTA axial source images in each carotid artery plaque in subjects with NASCET 50%-69% ICA stenosis. We used logistic regression and receiver operating characteristic analyses to assess the strength of the association between thickness measurements and prior stroke or TIA.

Results: Twenty of 72 vessels studied (27.7%) had ischemic symptoms ipsilateral to the side of moderate-grade carotid stenosis. Each 1-mm increase in soft plaque resulted in a 3.7 times greater odds of a prior ipsilateral ischemic event (95% CI, 1.9-7.2). Conversely, for each 1-mm increase in hard plaque, the odds of being symptomatic decreased by approximately 80% (OR, 0.22; 95% CI, 0.10%-0.48%). Receiver operating characteristic analysis showed an area under the curve of 0.88 by using soft-plaque thickness measurements to discriminate between asymptomatic and symptomatic plaques. Sensitivity and specificity were optimized by using a maximum soft-plaque thickness of 2.2 mm, which provided a sensitivity of 85% and a specificity of 83%.

Conclusions: Simple CTA plaque-thickness measurements might differentiate symptomatic and asymptomatic moderate-grade carotid artery plaque. With further prospective validation, CTA plaque measures could function as an easily implementable tool for risk stratification in carotid artery disease.

Fig 1.

Representative magnified axial CTA image of the proximal internal carotid artery in a patient with predominantly soft plaque. The asterisk represents the residual patent ICA lumen. The white calipers represent maximum linear soft-plaque thickness, and black calipers represent maximum hard-plaque thickness measurements.

Fig 2.

Representative magnified axial CTA image of the proximal internal carotid artery in a patient with predominantly calcified plaque. The asterisk represents the residual patent ICA lumen. The white calipers represent maximum linear soft-plaque thickness, and black calipers represent maximum hard-plaque thickness measurements.

Fig 3.

Receiver operating characteristic curves for maximum soft-plaque thickness (A) and maximum hard-plaque thickness (B).