Purpose: Drag reducing polymers (DRPs) have been shown to decrease plaque formation. Their mechanism of action is unknown. Atherosclerosis tends to develop in areas of low shear stress. This study investigates whether DRPs increase shear stress in areas normally exposed to low shear stress.
Methods: Six dogs underwent surgical plication of the left half of the aorta. A specially modified 20-MHz Doppler ultrasound probe mounted at a 45-degree 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 aortic wall and then at subsequent 0.1-mm depths moving into the lumen before and after administering DRP. Shear rates were calculated using linear regression and then compared using the paired t test. The blood viscosity remained constant at 0.04 poise during infusions of this amount of DRP.
Results: The maximum shear rate occurring during the cardiac cycle on the side of the aortic stenosis (plication) was 9.96 +/- 1.52/sec before the administration of the DRP and 14.27 +/- 2.01/sec after the administration of the DRP (P =.0240). The maximum shear rate on the side of the unstenosed aortic wall was 57.25 +/- 7.93/sec before the administration of the DRP and 44.80 +/- 6.23/sec after the administration of the DRP (P =. 0081).
Conclusion: One of the ways that DRPs inhibit the development of atherosclerosis 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.