Contrast Enhanced Ultrasound (CEUS) Is Not Able to Identify Vulnerable Plaques in Asymptomatic Carotid Atherosclerotic Disease

Objectives: Contrast enhanced ultrasound (CEUS) has been suggested as an imaging tool for detection of asymptomatic carotid atherosclerotic disease (ACAD) at high risk of cerebral embolisation. The objective of this study was to evaluate CEUS and immunohistochemical (IHC) patterns in ACAD (i.e., without any neurologic symptoms in the last 6 months) and their correlations with histology.

Methods: CEUS analysis was classified on a semiquantitative basis using a three-point classification scale. Plaque morphology was assessed using the American Heart Association (AHA) classification of atherosclerotic plaques, then accordingly assigned as non-vulnerable (AHA Type IV/V) or vulnerable (AHA Type VI). IHC analysis for intra-plaque neo-angiogenesis (IPN) was identified by CD34/VEGF immunostaining and classified on a semiquantitative basis using a four-point classification scale. Both CEUS and IHC analyses were performed and scored by single observers.

Results: Fifty-eight consecutive asymptomatic patients (mean age 73 years, 33 males) undergoing carotid endarterectomy were included in the final analysis. Nineteen had AHA Class IV/V plaques, and the remaining 39 had AHA Class VI plaques. There were two main findings of the study: (a) histologically proven vulnerable plaques compared with histologically proven non-vulnerable plaques had denser IPN (p = .004), but did not show more pronounced contrast enhancement; (b) the correlation between IHC analysis and CEUS analysis was significant for both vulnerable and non-vulnerable plaques (p = .04 and p = .01, respectively), but it was direct for AHA Type IV/V plaques and inverse for AHA Type VI plaques.

Conclusions: The main findings of the study were that histologically proven vulnerable plaques (i.e., AHA Class VI) as compared with histologically proven non-vulnerable plaques (i.e., AHA Class IV/V) had denser neo-vascularisation, but not more pronounced contrast enhancement.