Four-Dimensional Ultrasonographic Characterization of Plaque Surface Motion in Patients With Symptomatic and Asymptomatic Carotid Artery Stenosis

Abstract

Background and Purpose-In vitro studies of atherosclerotic plaque fracture mechanics suggest that analysis of local variations in surface deformability may provide information on relative vulnerability to plaque fissuring or rupture. We investigated plaque surface deformations in patients with symptomatic and asymptomatic carotid artery disease using 4-dimensional ultrasonography and techniques for measuring optical flow. Methods-Four-dimensional ultrasound examinations of carotid artery plaques were performed in 23 asymptomatic and 22 symptomatic patients with 50% to 90% stenosis of the internal carotid artery. Plaque surface motion during 1 cardiac cycle was computed with a hierarchical model-based motion estimator. Results were compared with plaque echogenicity and surface structure. Results-Of the 45 patients examined, plaque surface motion estimates were obtained for 18 asymptomatic and 13 symptomatic patients. There were no significant differences in echogenicity or surface structure of asymptomatic and symptomatic plaques (PϾ0.05). Results of motion estimation showed that asymptomatic plaques had surface motion vectors of equal orientation and magnitude to those of the internal carotid artery, whereas symptomatic plaques demonstrated evidence of inherent plaque movement. There was no significant difference in maximal plaque velocity between symptomatic and asymptomatic plaques (PϽ0.14). Maximal discrepant surface velocity (MDSV) in symptomatic plaques was 3.85Ϯ1.26 mm/s (meanϮSD), which was significantly higher (PϽ0.001) than MDSV of asymptomatic plaques with 0.58Ϯ0.42 mm/s (meanϮSD). Conclusions-MDSV

Critical Cap Thickness and Rupture in Symptomatic Carotid Plaques

“…26 Second, arterial wall motion is also likely to differ between the 2 vascular beds which may affect propensity of plaques to rupture. 28 Third, some data suggest that macrophages play a more important role in coronary plaque rupture than in carotid rupture and therefore the mechanisms of cap rupture may differ. 26 Fourth, the importance of plaque "erosion" in symptom generation may differ between the 2 vascular beds.…”

Comparison of Block Matching and Differential Methods for Motion Analysis of the Carotid Artery Wall From Ultrasound Images

“…The method of Bang et al [6] produced a dense displacement vector map, from which 29 parameters were estimated representing amplitude, stretch/compression, and shear motion of the atherosclerotic plaque [7]. Motion of the carotid atheromatous plaque from 3-D ultrasound images has been estimated using OF [8]. Significant differences were found in relative plaque motion between symptomatic and asymptomatic subjects.…”

Stratifying risk: asymptomatic carotid disease

“…In addition, asymptomatic patients were found to have more homogenous orientation and magnitude of velocity vectors 73 . Heterogeneous plaque motion pattern was also found inside the plaque with some regions fairly immobile and others highly mobile, in a study performed in 11 volunteers by Bang and colleagues 76 .…”

“…Some experimental and clinical observations of plaque motion have been made [72][73][74][75][76] . The rationale of plaque motion relies on the constant displacement vectors applied to the plaque surface by the dragging forces generated by the blood stream during the cardiac cycle.…”

“…The differences of the plaque surface motion were assessed in asymptomatic (n=18) and symptomatic (n=13), demonstrating maximal discrepant surface velocity higher in symptomatic patients than in those asymptomatic mainly in the cardiac systole 73 . In addition, asymptomatic patients were found to have more homogenous orientation and magnitude of velocity vectors 73 .…”