Identification of Carotid 'Vulnerable Plaque' by Contrast-enhanced Ultrasonography: Correlation with Plaque Histology, Symptoms and Cerebral Computed Tomography.

Introduction: Indication to carotid revascularisation is commonly determined by percent of stenosis as well as neurological symptoms and clinical conditions. High plaque embolic potential is defined as 'vulnerability'; however, its characterisation is not universally used for carotid revascularisation. We investigated the role of contrast-enhanced ultrasonography (CEUS) to identify carotid vulnerable plaque. Methods: Patients undergoing carotid endarterectomy were preoperatively evaluated by cerebral computed tomography (CT) scan and CEUS. Contrast microbubbles detected within the plaque indicated neovascularisation and were quantified by decibel enhancement (dB-E). Plaques were histologically evaluated for five features: (microvessel density, fibrous cap thickness, extension of calcification, inflammatory infiltrate and lipid core) and blindly scored 1-5 to assess plaque vulnerability. Analysis of variance (ANOVA), Fisher's and Student's t-test were used to correlate patients' characteristics, histological features and dB-E. Results: In 22 patients, dB-E (range 2-7.8, mean 4.85 ± 1.9 SD) was significantly greater in symptomatic (7.40 ± 0.5) vs. asymptomatic (3.5 ± 1.4) patients (p = 0.002). A higher dB-E was significantly associated with thinner fibrous cap (<200 μm, 5.96 ± 1.5 vs. 3 ± 1, p = 0.01) and greater inflammatory infiltrate (3.2 ± 0.9 vs. 6.4 ± 1.2, p = 0.03). Plaques with vulnerability score of 5 had significantly higher dB-E compared with those with vulnerability score of 1 (7.6 ± 0.2 vs. 2.5 ± 0.6, respectively, p = 0.001). Preoperative ipsilateral embolic lesions at CT were correlated with higher dB-E (5.96 ± 1.5 vs. 3.0 ± 1.0, p = 0.01). Conclusion: CEUS with dB-E is indicative of the extent of plaque neovascularisation. It can be used therefore as a marker for vulnerable plaque.