In vivo association between low wall shear stress and plaque in subjects with asymmetrical carotid atherosclerosis

Background and Purpose It is known that atherosclerosis does not involve both carotid arteries to the same extent. Pathological investigations have demonstrated that lesions develop in regions of low wall shear stress. The aims of the present study were to verify the degree of carotid atherosclerosis asymmetry in a population-based study and to evaluate whether wall shear stress is lower in carotids with atherosclerotic lesions than in carotids without lesions. Methods Participants in a cardiovascular disease prevention campaign (n=1166) were screened for carotid atherosclerosis by echo-Doppler examination. Of these, 23 subjects who pre -sented plaque in the common carotid or bulb of one side and no plaque in the contralateral carotid tree were enrolled for common carotid wall shear stress measurement. Shear stress was calculated according to the following formula: Shear Stress=Blood ViscosityxBlood Velocity/Internal Diameter. Results Of the 1166 subjects screened, 400 (34%) had plaque and/or stenosis in the carotids. Ninety subjects had lesions exclusively in the right carotid, 111 had lesions exclusively in the left, 70 had lesions in both carotids but with different degrees of severity, and only 129 had similar lesions in both carotids. In the 23 subjects in whom wall shear stress was measured, peak shear stress was 18.7+/-4.1 and 15.3+/-4.0 dynes.cm(-2) (mean+/-SD) (P<.0001) in the side without and the side with plaque, respectively. Mean shear stress yielded similar results. Conclusions The present results demonstrate that the atherosclerotic involvement of carotid arteries is usually asymmetrical and that wall shear stress is lower in the carotid arteries where plaques are present than in plaque-free arteries. These findings provide in vivo evidence for a strong association between shear stress and atherosclerotic lesions.