Drag reducing polymers may decrease atherosclerosis by increasing shear inareas normally exposed to low shear stress

Purpose: Drag reducing polymers (DRPs) have been shown to decrease plaque f ormation. Their mechanism of action is unknown. Atherosclerosis tends to de velop in areas of low shear stress. This study investigates whether DRPs in crease shear stress in areas normally exposed to low shear stress. Methods: Six dogs underwent surgical plication of the left half of the aort a. A specially modified 20-MHz Doppler ultrasound probe mounted at a 45-deg ree angle on a micromanipulator was used to measure blood flow velocity at six 4-mm intervals along both lateral sides of the aorta starting at the ao rtic wall and then at subsequent 0.1-mm depths moving into the lumen before and after administering DRP. Shear rates were calculated using linear regr ession and then compared using the paired t test. The blood viscosity remai ned constant at 0.04 poise during infusions of this amount of DRP. Results: The maximum shear rate occurring during the cardiac cycle on the s ide of the aortic stenosis (plication) was 9.96 +/- 1.52/sec before the adm inistration of the DRP and 14.27 +/- 2.01/sec after the administration of t he DRP (P = .0240). The maximum shear rate on the side of the unstenosed ao rtic wall was 57.25 +/- 7.93/sec before the administration of the DRP and 4 4.80 +/- 6.23/sec after the administration of the DRP (P = .0081). Conclusion: One of the ways that DRPs inhibit the development of atheroscle rosis appears to be by increasing shear stress in areas normally exposed to low shear stress. Understanding this mechanism may lead to the development of pharmaceutical agents that inhibit the development of atherosclerosis.