A Systematic Literature Review of Ultrasonography for Morphology and Characterization of Vulnerable Carotid Artery Plaques

Background and Purpose Although ultrasound (US) evaluation of the carotid artery for stenosis is the accepted method for identifying risk factors for cerebrovascular (CV) events, patients with specific plaque morphology may be at increased risk. Plaque characterization via US is a potentially useful adjunct to stenotic grading for identifying vulnerable carotid disease. The aim of this study was to systematically review published clinical trials via the use of US to identify vulnerable plaques among both symptomatic and asymptomatic plaques. Methods We used a systematic search using Medline, Embase, and the Cochrane library databases to find relevant studies published between 2001 and 2011. We reviewed randomized, controlled human clinical trials that validated the applicability, diagnostic accuracy, and diagnostic impact of US carotid plaque characterization. For studies reporting qualitative findings, we abstracted information about the study design and technique and the quality of the methodology and analyzed the data using a modified Jadad scale. Results In this review, we identified 12 studies related to the evaluation of carotid plaque using US. The studies used a wide range of methodologies to quantify and image the plaque morphology. Published literature on this subject is lacking; however, this deficit may be because current studies are ongoing. Specific plaque characteristics identified as vulnerable included particular echo texture, the presence of echolucency and/or ulceration, surface alterations, and volume assessment using 3-dimensional US (3D US). In a minority of studies investigators used histopathology as the reference standard, and in most they used subsequent clinical observations. All studies demonstrated that US has good accuracy and specificity in identifying possible imaging characteristics related to vulnerable plaques. Conclusion The collected evidence shows that US is effectively able to detect specific carotid plaque characteristics related to high-risk plaques vulnerable for CV events. We anticipate that additional well-designed prospective studies will provide more definitive evidence and distinguish specific distinctive findings that may serve as indicators of vulnerable plaques. Our findings must be extended to demonstrate the accuracy and validity in everyday clinical imaging findings.