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.
Keywords: ED, endothelial dysfunction; EF, endothelial function; FMD, flow-mediated dilation; FMS, flow-mediated slowing; PWV, pulse wave velocity; RH, reactive hyperemia.