Flow-Mediated Slowing as a Methodological Alternative to the Conventional Echo-Tracking Flow-Mediated Dilation Technique for the Evaluation of Endothelial Function: A Preliminary Report

The Moens-Korteweg equation predicts changes in pulse wave velocity (PWV) after changes in arterial radius; therefore, an increase in arterial radius, as seen in a reactive hyperemia (RH) condition, should slow PWV over a given arterial segment. If this assumption is true, then the deceleration of PWV over the brachial artery (flow-mediated slowing [FMS]) should be an equivalent signal of endothelial function during a conventional RH flow-mediated dilation (FMD) procedure. Our aim was to compare FMS with FMD after RH in healthy individuals as part of a study that seeks to evaluate the clinical usefulness of FMS as a noninvasive approach to characterize endothelial function. This cross-sectional study included 25 healthy participants (18 women [72%]) with a mean ± SD age of 21.12±0.73 years. The FMD and FMS were simultaneously measured. A significant correlation was observed between both measures of FMS (absolute difference and percentage variation) and echo FMD: R=−0.42 (P=.04) and r=0.46 (P=.02), respectively. The FMS was shown to depend on the baseline brachial diameter, with smaller variations depicted for smaller baseline brachial diameters. It seems to be a promising and feasible method for measuring changes after RH, although further studies are needed to evaluate how this correlation holds in different clinical conditions and to demonstrate its clinical usefulness.