Carotid artery plaque echomorphology and its association with histopathologic characteristics

Objective: The aim of the study was to determine the association of ultrasonic texture features (severity of stenosis, grey scale median, plaque area, juxtaluminal black area [JBA], and discrete white areas) previously shown to be independent predictors for stroke with established histologic features of plaque instability. Methods: A cross-sectional study was performed involving 70 patients scheduled for carotid endarterectomy. Before surgery, carotid plaque texture features were obtained with ultrasound after normalization using commercially available software (LifeQ Medical, Nicosia, Cyprus). After carotid endarterectomy, histologic features (number of macrophages [CD68 staining], severity of angiogenesis [CD31 staining], smooth muscle cell [SMC] numbers, size of lipid core, thickness of the fibrous cap, presence of intraplaque hemorrhage, plaque rupture, and instability) also were studied. Results: Symptomatic (n = 20) and asymptomatic (n = 50) patients were comparable in terms of internal carotid stenosis (mean stenosis, 86%; range, 60%-99%) and prevalence of risk factors except for total cholesterol (which was higher in the symptomatic group; P =.023). A low grey scale median and the presence of discrete white areas were associated with an increased number of macrophages (P <.001 and P <.001, respectively), increased neovascularization (P =.019 and P <.001, respectively), larger lipid core (P =.001 and P =.025, respectively), intraplaque hemorrhage presence (P =.001 and P =.001, respectively), plaque rupture (P =.001 and P =.025, respectively), and a decreased number of SMCs (P =.003 and P =.003, respectively). The presence of JBA was associated with a decreased number of SMCs (P =.042), larger lipid core (P =.013), and plaque rupture (P =.002). The combination of a thin fibrous cap with either a large lipid core or plaque rupture was associated with the highest (65%) prevalence of a JBA. Plaque area was not associated with any of the histologic features. After adjusting statin therapy for symptoms, statins were associated with a decreased number of macrophages (P =.038), decreased neovascularization (P =.019), and an increased number of SMCs (P =.023). Conclusions: A number of ultrasonic texture features previously shown to be independent predictors of stroke have been found to have a strong association with established histologic features of plaque instability. This finding provides insight into the mechanism of ultrasonic texture features in stroke prediction and validates the use of ultrasound in stroke risk stratification.