Shear stress regulation of artery lumen diameter in experimental atherogenesis

Abstract

We studied the adaptive response of the arterial wall and intimal thickening under conditions of increased flow in an atherogenic model. Blood flow was increased by construction of an arteriovenous fistula between the right iliac artery and vein in six cynomolgus monkeys fed a diet containing 2% cholesterol and 25% peanut oil. The left iliac artery served as the control. Serum cholesterol increased from 135 ± 22 mg/dl to 880 ± 129 mg/dl during the experiment. After 6 months, blood flow in the right iliac artery (420 ± 95 ml/min) was 10 times greater than in the left iliac artery (44 ± 9 ml/min, p < 0.005). Flow velocity in the right iliac artery (31 ± 6 cm/sec) was more than twofold greater than in the left (12 ± 1 cm/sec, p < 0.05). Despite the marked difference in blood flow and flow velocity, calculated wall shear stress was the same in both the right (16 ± 4 dynes/cm2) and left iliac vessels (15 ± 2 dynes/cm2) because of a twofold increase in lumen diameter (p < 0.001) of the right iliac artery. Shear stress in the aorta was also normal (12 ± 2 dynes/cm2). There was no difference in plaque deposition or mean intimal thickness between the right and left iliac arteries. In the right iliac artery there was a twofold increase in media cross-sectional area (p < 0.001) but no change in media thickness or total wall thickness. Tangential wall tension and tangential wall stress were two times greater on the right than on the left (p < 0.001). These results suggest that increased blood flow results in arterial dilatation and normalization of wall shear stress and that shear stress may serve to regulate artery lumen diameter. Increased blood flow and increased flow velocity do not enhance atherosclerotic plaque deposition under these experimental conditions. Arterial enlargement resulting in an increase in wall tension without artery wall thickening or compensatory changes in wall composition may explain the aneurysmal dilatation seen in chronic arteriovenous fistulas and high flow autogenous grafts in human beings. © 1987.