B-mode ultrasonographic characterization of carotid atherosclerotic plaques in symptomatic and asymptomatic patients

Objective: To identify features on B-mode ultrasonography (US) prevalent in symptomatic plaques and correlate these findings with histopathologic markers of plaque instability. Methods. Carotid endarterectomy (CEA) plaques from symptomatic and asymptomatic patients with critical stenoses (> 70%) were qualitatively assessed using preoperative B-mode US for echolucency and calcific acoustic shadowing. US echolucency was quantitated ex vivo using computerized techniques for gray-scale median (GSM) analysis. Histopathologic correlates for US plaque echolucency (percentage of necrotic core area) and acoustic shadowing (percentage of calcification area) were determined. Results:Fifty CEA plaques were collected from 48 patients (46 unilateral and two bilateral); 26 of these plaques were from symptomatic patients. Age, degree of stenosis, and atherosclerotic risk factors were similar for the symptomatic and asymptomatic patients. Using preoperative B-mode US, 58%, 35%, and 7% of symptomatic plaques and 18%, 41%, and 41% of asymptomatic plaques were found to be echolucent, echogenic, and calcific, respectively (P < .05). Using ex-vivo B-mode US and GSM analysis, symptomatic plaques were more echolucent (41 +/- 19) than asymptomatic plaques (60 +/- 13), P < .03. A strong inverse correlation was found between the percent plaque necrotic area core and GSM (R = -0.9, P < .001). Percentage of calcification area in plaques with acoustic shadowing was 66% and only 27% in those without acoustic shadowing (P < .05). Conclusions. Using B-mode US, symptomatic plaques are more echolucent and less calcified than asymptomatic plaques and are associated with a greater degree of histopathologic plaque necrosis. Such features are indicative of plaque instability and should be considered in the decision-making algorithm when selecting patients with high-grade asymptomatic carotid stenosis for intervention.