Shear stress in the common carotid artery is related to both intima-media thickness and echogenecity

It has previously been shown that the degree of shear stress (SS) in the carotid artery is related to both plaque occurrence and intima-media thickness (IMT). Since the echogenecity also is an important feature of plaques, we investigated if a reduced shear stress also is related to the echolucency of plaque and the intima-media complex. In the Prospective Study of the Vasculature in Uppsala Seniors (PIVUS) study, a population-based study of 1016 subjects aged 70, left common carotid artery diameter, IMT, the grey scale median (GSM) of the intima-media complex (IM-GSM) and the blood flow velocity were measured by ultrasound. Occurrence of plaque was noted, and the echogenecity of the plaques was visually estimated by the Gray-Weale classification. Shear stress was inversely related to both IMT and IM-GSM (p = 0.0084 and p = 0.003, respectively), independently of gender and coronary risk, estimated by the Framingham risk score. Shear stress was lower in subjects with carotid plaque (44% of the sample) than in those without (p = 0.0013), and was inversely related to the echogenecity in the subjects with plaque (p = 0.0092), independently of gender and coronary risk. A low shear stress in the common carotid artery was associated with both a thick IMT and an echolucent intima-media complex. A similar picture was seen when overt plaques were evaluated, suggesting that shear stress is of importance for both the extent and composition of atherosclerosis.