Abstract 377: Retrograde Shear Stress does not Alter Endothelial Function in Healthy Subjects

Abstract

Introduction: Endothelial dysfunction is a precursor and plays a significant role in development of atherosclerosis. Retrograde flow and resulting retrograde shear stress has been shown to adversely affect the endothelial function but the results may be flawed due to experimental conditions. Change in the limb position might result in increase in retrograde flow and adversely affect endothelial function. We hypothesized that elevation of arm above the level of the heart will result in increased retrograde flow and reduced endothelial function as measured by flow mediated dilation (FMD). Methods: We enrolled 27 healthy subjects after obtaining informed consent. Endothelial function was measured by FMD in brachial artery before and after arm elevation with elbow support for 30 minutes in fasting state. Flow velocities were recorded and analyzed at baseline, 10 and 20 minutes after arm elevation and at the end of 30 minutes. Results: The mean retrograde flow velocity was 9.9 ± 7.75 cm/sec at baseline, which increased to 15.8 ± 6.56 cm/sec (p=0.0019) after arm elevation. Out of the 27 subjects 21 (78%) subjects had increase in retrograde flow (20% or more). The difference in FMD change between the groups with increased or no change in retrograde flow was statistically non-significant (p=0.4). Conclusion: In conclusion arm elevation for 30 minutes was associated with statistically significant increase in retrograde flow without significant change in endothelial function in normal healthy subjects. The change in endothelial function between subjects who had augmented retrograde shear and those who did not was statistically not significant.