Researchers from the Imperial College Faculty of Medicine in London in the United Kingdom (S Kakkos, M Griffin, A Nicolaides, E Kyriacou, M Sabetai, T Tegos, G Geroulakos) revealed that the presence and size of a juxtaluminal black (hypoechoic) area (JBA) on carotid ultrasound of asymptomatic carotid artery plaques can predict the occurrence of ipsilateral ischemic stroke. Their findings were explained today at the 66th Vascular Annual Meeting presented by the Society for Vascular Surgery®.
Co-author Stavros K. Kakkos, MD, MSc, PhD, RVT, who also is in the Department of Vascular Surgery at the University Hospital of Patras in Patras, Greece, said that the JBA is associated with a lipid core close to the lumen or a thrombus on the plaque surface and is defined as an area of carotid plaque pixels with gray scale median (GSM) value less than 25 which is adjacent to the vessel lumen and lacks a visible echogenic cap, after image normalization of the ultrasound plaque images.
The size of a JBA was measured in the carotid plaque images of 1,121 patients with asymptomatic carotid stenosis that was 50-99 percent in relation to the bulb which was followed for up to eight years. "We confirmed that JBA had a linear association with future stroke rate," said Dr. Kakkos. "The area under the ROC curve was 0.816. Using Kaplan Meier curves, the mean annual stroke rate was 0.4 percent in 706 patients with a JBA size <4 mm2, 1.4 percent in 171 patients with JBA size 4-8 mm2, 3.2 percent in 46 patients with JBA size 8-10 mm2, and 5 percent in 198 patients with JBA size >10 mm2 with a highly significant statistical significance (P<.001)."
In multivariate analysis using a Cox model with ipsilateral ischemic events (amaurosis fugax, transient ischemic attack [TIA] or stroke) as the dependent variable, JBA (<4, 4-8, >8, in mm2) was still significant after adjusting for other plaque features known to be associated with increased risk. These include stenosis, GSM, presence of discrete white areas without acoustic shadowing (DWA) indicating neovascularization, plaque area and history of contralateral TIA or stroke. However, plaque area and GSM were not significant.
Using the significant variables (stenosis, DWA, JBA and history of contralateral TIA or stroke), this model predicted the annual risk of stroke (range 0.5-10.0 percent). The average annual stroke risk was <1 percent in 734 patients; 1-1.9 percent in 94; 2-3.9 percent in 134; 4-5.9 percent in 125; and 6-10 percent in 34.
"The size of JBA is linearly related to the risk of stroke and can be used in risk stratification models," said Dr. Kakkos. "These findings need to be confirmed in future prospective studies or in the medical arm of randomized controlled studies in the presence of optimal medical therapy."
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