Acoustic Shadowing on B-Mode Ultrasound of the Carotid Artery Predicts Ischemic Stroke

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Abstract
Background and Purpose —We examined the relationship of carotid artery lesions (CALs), with and without acoustic shadowing (AS), to incident ischemic stroke events in the Atherosclerosis Risk in Communities study cohort. Methods —The study population consisted of 13 123 men and women aged 45 to 64 years, and free of stroke, examined during 1986–1989. Over an average follow-up time of 8.0 years, 226 incident ischemic stroke cases (thromboembolic brain infarctions) were identified and classified by a standardized protocol. Three levels of exposure were defined on the basis of the presence of B-mode ultrasound–detected CALs and AS in a 3-cm segment of the carotid arteries centered at the bifurcation. Results —The hazard ratio for ischemic stroke adjusted for age, ethnicity, and study site for women with a CAL without AS, compared with those without a CAL, was 1.92 (95% CI, 1.23, 3.01), and the hazard ratio comparing those with a CAL with AS with those without a CAL was 4.01 (95% CI, 2.28, 7.06). The corresponding hazard ratios for men were 1.99 (95% CI, 1.36, 2.91) and 2.23 (95% CI, 1.32, 3.79). Although adjustment for diabetes, hypertension medication, systolic blood pressure, left ventricular hypertrophy score, fibrinogen, von Willebrand factor antigen, and smoking status attenuated these associations somewhat, when compared with no evidence of CALs, CALs with AS remained statistically significant predictors of ischemic stroke in women, while CALs without AS were predictive of ischemic stroke in men. Conclusions —B-mode ultrasound–detected CALs and AS serve as markers of atherosclerosis and thus are predictive of ischemic stroke.