Association of Flow-mediated Dilation with Shear Rate in Patients and Healthy Volunteers

Introduction: Flow mediated-dilation (FMD) is a noninvasive test of endothelial function based on shear stressdependent nitric oxide secretion causing vasodilation. Normalization of FMD to shear stress was previously proposed. The aim of present study is an examination of relationship between shear rate and FMD in patients with hypertension and atherosclerosis in comparison with healthy volunteers. Methods: Three groups (11 with essential hypertension, 28 with advanced atherosclerosis and 26 controls) were examined. Flow mediated dilation after 5-minute cuff occlusion and post-deflation shear rate were assessed. Brachial artery diameters and blood velocities were obtained by means of high-resolution ultrasound machine. Results: Positive correlations were found between FMD and shear rate with correlation coefficients depending on the disease. Statistical significance was found in atherosclerosis and control groups. Shear rate stimulus is most effective in healthy controls and least effective in hypertensive patients. Conclusions: Post-ischemic shear rate or shear stress should also be taken into account while evaluating the endothelial function with vasodilation measurements.