Flow-mediated slowing shows poor repeatability compared with flow-mediated dilation in non-invasive assessment of brachial artery endothelial function

Abstract

Pulse wave velocity (PWV) deceleration to reactive hyperemia–flow-mediated slowing (FMS)–has been suggested as an alternative method to flow-mediated dilation (FMD) to evaluate brachial artery endothelial function. FMS is suggested to address major caveats of the FMD procedure including its suboptimal repeatability and high-operator dependency. However, the repeatability of FMS has not been thoroughly examined, especially given the plethora of methods claiming to measure PWV. We assessed and compared the intra- and inter-day repeatability of FMS as measured by piezoelectric pressure mechanotransducers placed in the carotid and radial arteries, and brachial artery FMD as measured by echo-tracking. Twenty-four healthy male participants aged 23–75 yr, were examined on three separate days to assess intra and inter-day repeatability. All FMD and FMS examinations were conducted simultaneously by the same researcher complying with standardized guidelines. Repeatability was examined with intraclass correlation coefficient (ICC; >0.80), coefficient of variation (CV; <15%), and limits of agreement (95% LOA). Relative (%) FMD and FMS were scaled for baseline brachial artery diameter and PWV, respectively. Intra- (ICC: 0.72; CV: 136%; 95% LOA: -19.38 to 29.19%) and Inter-day (ICC: 0.69; CV: 145%, 95% LOA: -49.50 to 46.08%) repeatability of %FMS was poor, whereas %FMD demonstrated moderate-to-good intra- (ICC: 0.93; CV: 18%, 95% LOA: -3.02 to 3.75%) and inter-day repeatability (ICC: 0.74; CV: 25%, 95% LOA: -9.16 to 7.04%). Scaling FMD reduced the intra-day CV (-5%), and the uncertainty of the 95% LOA (- 37.64 to 35.69%) estimates of FMS. Carotid-radial artery FMS showed poorer repeatability compared to FMD.

Intra and inter-rater repeatability of brachial artery ultrasound estimates of flow-mediated slowing and flow-mediated dilation

“…Both raters demonstrated good to excellent intra-and inter-day repeatability in the offline analyses of local estimates of FMS and FMD [7,32]. These findings are contradictory to those from regional FMS (CV > 100%) published earlier by this research group [15], but aligned with the FMS repeatability reported by Ellins et al [11]. Together, this suggests that the heterogeneity in viscous-elastic properties of the arteries is likely the main confounder in regional FMS including both elastic and muscular arteries.…”

“…However, this conclusion was drawn from a single-rater study, limiting its clinical applicability where multiple raters would evaluate the same patient. In addition, our previous work contradicts this initial report as FMS (CV: 136%) was found to be less repeatable compared to FMD (CV: 25%) [15]. One possible reason for this discrepancy is the heterogeneity in viscoelasticity properties between the upper limb arterial segments used to estimate PWV.…”

“…Hypothetically, this supports the idea that increases in NO-mediated vasodilation mediated by shear stress underpin local but not regional carotid radial PWV reductions to reactive hyperemia. Therefore, these confounding factors can explain the equivocal repeatability of FMS measurements between studies [ 11 , 15 ] and are likely to extend to other devices used in FMS repeatability studies.…”

“…Ellins et al, [ 11 ] estimated FMS using reactive hyperemia-induced changes in PWV over the brachial to radial arterial segment, which is a muscular arterial segment with thicker tunica media. On the other hand, we measured PWV over a mixed carotid-radial segment where the carotid artery has a higher elastin-to-collagen ratio resulting in a greater distensibility compared to the radial and brachial arteries [ 15 ].…”

Radiological Modalities for the Assessment of Fetal Growth Restriction: A Comprehensive Review

“…Studies on flow-mediated dilatation (FMD) and flow-mediated slowing (FMS) in newborns with FGR are scarce. Although these methods are widely accepted for evaluating vascular well-being in adults and older kids, their application in newborns, particularly in FGR, is still nascent (57).…”