Mechanical Forces and Carotid Atherosclerosis in Patients with Risk Factors for Atherosclerosis
Mechanical stresses to the arterial wall were evaluated in the carotid artery in 117 patients with risk factors for atherosclerosis including hypertension, dyslipidemia, and diabetes mellitus. Circumferential wall tension and shear stress were evaluated using Laplace’s law and Poiseuillean‘s parabolic model of flow velocity distribution. Arterial strain was also evaluated as the circumferential wall stretch. Wall tension was significantly related to BMI (r=0.40, p<0.0001), systolic pressure (r=0.79, p<0.0001), triglyeride (r=0.19, p<0.05) as well as HDL cholesterol (r=-0.22, p<0.05), while shear stress showed significant relationships with age (r=-0.34, p<0.001), pulse pressure (r=-0.27, p<0.01) and HDL-cholesterol (r=0.19, p<0.05). On the other hand, arterial strain did not correlate with any risk factor. Carotid intima-media thickness (IMT) showed a significant positive correlation with peak wall tension (r=0.44, p<0.0001) and mean wall tension (r=0.31, p<0.001), and a significant negative correlation with peak systolic shear stress (r=0.34, p<0.001) and mean shear stress (r=-0.42, p<0.0001), while there was no significant relationship between arterial strain and IMT. Stepwise regression analysis revealed that low shear stress and high wall tension were independently associated with IMT in the total subjects with risk factors. Furthermore, it revealed that wall tension was independently associated with IMT in hypertensive patients, while shear stress was an independent determinant of IMT in normotensive subjects. These findings indicate that both wall tension and shear stress are associated with carotid atherosclerosis in subjects with risk factors for atherosclerosis. However, the degree of contribution of mechanical forces to atherosclerosis differs among risk factors.