DETERMINATION OF WALL SHEAR-STRESS IN THE AORTA WITH THE USE OF MR PHASE-VELOCITY MAPPING

MR phase velocity mapping was used to calculate wall shear stress (WSS ) in thc suprarenal and infrarenal abdominal aorta, two sites with ver y different proclivities for development of atherosclerosis. For the E ight subjects studied, the average value of the mean (time averaged ov er the cardiac cycle) WSS in the suprarenal aorta was 10.4 dynes/cm(2) at the posterior wail and 8.6 at the anterior wall. In the infrarenal aorta, WSS values were 4.7 at the posterior wall and 6.1 at the anter ior wall, Peak WSS over the cardiac cycle was 48 and 54 at the anterio r and posterior walls of the suprarenal aorta, respectively, and 33 an d 30 at the anterior and posterior walls of the infrarenal aorta, resp ectively. Wide variation was found in both mean and peak WSS values am ong subjects. However, for 28 of 32 locations examined, mean and peak WSS were higher in the suprarenal aorta than in the infrarenal aorta B ecause atherosclerosis Is more likely to form in the infrarenal aorta than in the suprarenal aorta, this study supports the hypothesis that low WSS is a localizing factor for atherosclerosis, and high WSS may a ct as a deterrent against formation of atherosclerosis.