Evaluation of Computed Tomography Angiography Plaque Thickness Measurements in High-Grade Carotid Artery Stenosis

Abstract

Background and Purpose— Increasing evidence suggests that carotid artery imaging can identify vulnerable plaque elements that increase stroke risk. We correlated recently proposed markers, soft and hard plaque thickness measurements on axial computed tomography angiography source images, with symptomatic disease status (ipsilateral stroke or transient ischemic attack) in high-grade carotid disease. Methods— Soft plaque and hard plaque thickness were measured with a recently validated technique using computed tomography angiography source images in subjects with ≥70% extracranial carotid artery stenosis. Logistic regression analyses were used to assess the strength of association between soft and hard plaque thickness measurements and previous stroke or transient ischemic attack. Receiver operating characteristic analysis was also performed. Results— Compared with asymptomatic subjects, those with symptomatic carotid disease had significantly larger soft plaque and total plaque thickness measurements and smaller hard plaque thickness measurements. Each 1-mm increase in soft plaque resulted in a 2.7 times greater odds of previous stroke or transient ischemic attack. Soft plaque thickness measurements provided excellent discrimination between symptomatic and asymptomatic disease, with receiver operating characteristic analysis showing an area under the curve of 0.90. A cutoff of 3.5-mm maximum soft plaque thickness provided a sensitivity of 81%, specificity of 83%, positive predictive value of 85%, and a negative predictive value of 78%. Conclusions— Increasing maximum soft plaque thickness measurements are strongly associated with symptomatic disease status in carotid artery stenosis. Prospective validation of these results may translate into a widely accessible stroke risk stratification tool in high-grade carotid artery atherosclerotic disease.

CT Angiographic Features of Symptom-Producing Plaque in Moderate-Grade Carotid Artery Stenosis

“…Previous studies have shown that CTA plaque thickness measures can predict high-risk plaque as defined on correlative MR imaging 12 or symptomatic plaque in high-grade stenosis. 13 In the current study, we found that such CTA plaque measures can differentiate asymptomatic and symptomatic carotid plaques despite the relatively smaller volume of plaque and lower absolute stroke risk present in moderategrade stenosis. Moreover, we found no significant differences in traditional vascular risk factors in the asymptomatic and symptomatic groups, suggesting that plaque thickness measurements may be able to discriminate high-risk and stable plaque more accurately than clinical factors.…”

“…For example, a recent meta-analysis 25 of subjects with carotid stenosis followed after plaque MR imaging showed a lipid-rich necrotic core, intraplaque hemorrhage, and thinning or rupture of the fibrous cap as conferring 3-, 6-, and 4.5-fold higher risks of future stroke or TIA, respectively. Because lipid cores or hemorrhage together likely form a significant component of soft plaque, 13 we hypothesize that soft-plaque measurements may represent a simple composite marker of vulnerable, high-risk plaque elements. Similarly, calcium in carotid plaque may be associated with relatively more stable plaque, which is likely to cause ischemic stroke.…”

“…12,13 Briefly, a board-certified neuroradiologist analyzed axial source images from the CTA examination and recorded 3 measurements for each carotid artery: 1)…”

“…CTA-based measurements of soft and hard (calcified) plaque determined on axial CTA source images have recently been proposed as potential simple alternative markers of vulnerable plaque in high-grade ICA stenosis. 12,13 Because plaque volumes are relatively smaller in moderate-grade stenosis, it is unclear to what extent such techniques are capable of identifying symptom-producing plaque in this group of patients in whom optimal treatment guidelines are controversial. Therefore, we used a cross-sectional study design to assess the association between plaque thickness measurements obtained from neck CTA and previous stroke or TIA in patients with moderate-grade ICA stenosis.…”

Plaque morphology (the PLAC Scale) on CT angiography: predicting long-term anatomical success of primary carotid stenting

“…13,29,30 Although the CT calcification grade is known to predict the expansion of coronary stents 15 and has been suggested to be a relative contraindication to CAS, 8,16 few investigators use plaque morphology to help guide the choice of treatment 19 or to predict the immediate or long-term morphological success of CAS procedures.…”