Decreased wall shear stress in the common carotid artery of patients with peripheral arterial disease or abdominal aortic aneurysm: relation to blood rheology, vascular risk factors, and intima-media thickness

BACKGROUND: Wall shear stress, a local risk factor of atherosclerosis, is decreased in the common carotid artery of patients with vascular risk factors. We evaluated wall shear stress in the common carotid artery of patients with symptomatic peripheral arterial occlusive disease (PAD) and abdominal aortic aneurysm (AAA). As blood viscosity is a determinant of wall shear stress, we further investigated the impact of rheologic variables on wall shear stress in relation to vascular risk factors and intima-media thickness. METHODS: High-resolution ultrasonography scans were used to study intima-media thickness, internal diameter, and blood velocity in the common carotid artery of 31 patients with PAD, 36 patients with AAA, and 37 controls. Furthermore, major hemorheologic variables and vascular risk factors were evaluated, and wall shear stress was calculated. RESULTS: Wall shear stress was lower in patients with PAD (median [IQR], dynes/cm(2): 14.4 [10 to 19]) and with AAA (12.1 [9 to 15]) than in healthy controls (20.6 [17 to 24]; P < .0001). Wall shear stress was inversely related to red cell aggregation (P = .01), fibrinogen (P = .003), leucocyte count (P = .001), plasma viscosity (P = .04), and intima-media thickness (P < .0001). Furthermore, wall shear stress was negatively associated with age, smoking, and triglycerides, but positively correlated with high-density lipoprotein cholesterol (all P < .001). When the influence of all these predictors were simultaneously taken into account in a multiple regression model, only age (P < .0001), smoking (P = .005), and triglycerides (P = .003) remained significantly associated with wall shear stress. CONCLUSIONS: This is the first report, to our knowledge, showing that wall shear stress of the common carotid artery is decreased in patients with symptomatic PAD and in patients with AAA. Rheologic variables are less important in predicting wall shear stress than age, triglycerides, and smoking