BACKGROUND: Flow-Mediated Slowing (FMS) is a potentially simple, automated and user-objective test for assessing endothelial function. FMS can be defined as the minimum pulse wave velocity (PWV_min) during reactive hyperemia.
PURPOSE: The purpose of this study was to determine the effects of acute endothelial dysfunction on PWV_min. It was hypothesized that endothelial dysfunction would increase PWV_min.
METHODS: 22 young, healthy adults (23.8 yrs ± 4.1, 73% F, 22.8 kg/m² ± 2.8) underwent simultaneous assessment of Flow-Mediated Dilation (FMD) and PWV_min at baseline and immediately following 30min of an endothelial dysfunction protocol. FMD is the current gold-standard test of endothelial function and was used to confirm endothelial dysfunction. Endothelial dysfunction was induced by increasing retrograde shear stress in the brachial artery via inflation of a pneumatic tourniquet to 75 mm Hg around the forearm. PWV was measured from the upper-arm to the wrist using an oscillometric-based device, and brachial FMD was measured using duplex Doppler ultrasound. FMD (%) was calculated as the mean increase in diameter during reactive hyperemia, and PWV_min as the minimum pulse wave velocity during reactive hyperemia. Linear mixed models were used to assess baseline versus endothelial dysfunction changes in PWV_min and FMD, controlling for within-subject changes in mean arterial pressure. Inter-individual associations between baseline PWV_min and FMD were examined using Pearson’s product moment correlation, and intra-individual associations between change (baseline vs. endothelial dysfunction) in PWV and change in FMD using the repeated measures correlation package for R. RESULTS: The endothelial dysfunction protocol resulted in large effect size (ES) decrease in FMD (∆ = -3.10, 95%CI: -4.15, -2.05, ES = -1.3), and a moderate significant increase in PWV_min (∆ = 0.16, 95%CI: 0.05, 0.28, ES = 0.6). There was a moderate inter-individual association between FMD and PWV_min (r = 0.46), and a large intra-individual association between FMD and PWV_min (r = -0.61). CONCLUSIONS: Acute changes in PWV_min may be a user-objective, automated, and viable tool for monitoring acute changes in endothelial function.