Abstract 17531: Differences in Mobility Between Vulnerable Plaque Core and Plaque Cap and Base

Abstract

Rupture of vulnerable carotid plaques is one of the main causes of ischemic strokes, but their detection continues to elude physicians. We hypothesized that vulnerable plaque is characterized by an increased relative mobility of its inner part compared with cap and base.

Objective: To investigate the mechanical properties of symptomatic and asymptomatic carotid plaques using ultrasound speckle tracking.

Methods: Study population consisted of 43 patients with carotid atherosclerosis, 21 (aged 53-89, median 69) with acute atherothrombotic stroke (7 days after stroke onset) and 22 (aged 54-88, median 70) without symptoms. The stroke subtype was classified according to the TOAST criteria. In total, 21 symptomatic and 27 asymptomatic plaques with similar degree of stenosis were analyzed. For each plaque, maximum circumferential and longitudinal strain (Sc, Sl) and strain rate (Src, SRl) were measured (in several points separately for plaque cap, core and base). Plaque echogenicity and degree of stenosis were also assessed.

Results: For symptomatic plaques, Sc, Sl, SRc and SRl of plaque core were significantly higher than values for base and cap. This difference was more pronounced in low-echogenic plaques, whereas no difference was observed for asymptomatic plaques (Table 1). Plaque internal motion coefficient Cpim=(|core SRc - cap SRc|)/base SRc was developed to quantify the relative motion of different plaque segments against each other. According to ROC curve analysis, plaques with Cpim>0.65 were associated with ischemic event (sensitivity 52%, specificity 82%, AUC=0.70, p=0.018). Logistic regression confirmed that Cpim>0.65 is an independent predictor of plaque vulnerability, OR=4.82, 95% CI 1.4-17.6 controlling for degree of stenosis and echogenicity.

Conclusion: In symptomatic plaques, the inner part has a higher degree of mobility as compared with the cap and base. The increased mobility of the plaque core is linked with plaque vulnerability.