Prachi Mehndiratta, MD

Gupta A, Kesavabhotla K, Baradaran H, Kamel H, Pandya A, Giambrone AE, et al. Plaque Echolucency and Stroke Risk in Asymptomatic Carotid Stenosis: A Systematic Review and Meta-Analysis. Stroke. 2014

In light of improvement in intensive medical therapy, many question the need for asymptomatic carotid intervention and surgery despite two large positive clinical trials. Carotid plaque characteristics might help identify a sub population within this cohort of asymptomatic carotid stenosis patients that may have a higher risk of ipsilateral stroke. Carotid ultrasound is a tried and tested non invasive test employed to describe plaque characteristics such as plaque echolucency that is an imaging surrogate for hispathological core necrosis and intraplaque hemorrhage.

The authors performed meta-analyses of 7 studies evaluating whether ultrasound characterization of carotid plaque echogenicity is a predictor of ipsilateral stroke in asymptomatic carotid atherosclerotic disease. Manuscripts written in the English language, with atleast 30 or more asymptomatic patients, with follow up data available for >12 months on atleast 85%of the cohort were included. An effort was made to assess outcome ascertainment bias that relies on blinding of investigators, confounding by other variables and completeness of follow up data. A meta-analysis of studies that met two criteria was performed – 1) a relative risk (RR) was calculable; 2) echolucency test results were presented in a dichotomized or categorical fashion. Random effects modeling was used for statistical analysis as the included studies did not have the same effect size, 3 pre specified subgroup analyses were performed to evaluate studies with blinded adjudicators, studies in which plaque echolucency determination was made by subjective visual interpretation and newer studies published since 2000.

A total of 8 articles that were all prospective, longitudinal, non-randomized observational studies met criteria for qualitative review and pooling. Mean age ranged from 64.0-72.6 years and there was a male preponderance. Seven articles met criteria for calculation of relative risk and mean follow up period was 37.2 months. When subjects with and without carotid stenosis on medical management were evaluated, a positive relationship between plaque echolucency and the risk of future ipsilateral stroke was found with random effects (RR of 2.31, 95% confidence interval [CI], 1.58-3.39, P<.001). This relationship was true for risk across all stenosis severities. No statistically significant heterogeneity or publication bias was present in any of the meta-analyses.

This study has several important clinical implications. Patients with echogenic plaques have a 2.3 fold greater risk for ipsilateral stroke. This risk is present across all degrees of carotid stenosis and does not vary when adjustments were made for studies that utilized subjective visual interpretation of plaques, or studies with ascertainment and confounding bias were excluded. The authors concede that the studies included in this meta-analysis are fraught with some serious limitations due to unclear loss to follow up, ascertainment bias and selection bias due to inclusion of only medically managed patients. Despite these limitations, this study provides significant evidence in favor of detailed plaque evaluation in patients with asymptomatic carotid stenosis. An avenue for growth would be development of a standardized and validated technique for doing so.