Intra- and interday reproducibility of high-flow-mediated constriction response in young adults

Background: Previously, we have demonstrated that high-flow-mediated constriction (H-FMC) of the brachial artery has been shown to negatively affect flow-mediated dilation (FMD). However, the reproducibility of an H-FMC response is unknown. Objective: The aim of this study was to determine the intra- and interday reproducibility of H-FMC in young adults. Methods: Thirty young adults (15 male, 15 female; 24 ± 3 years) were assessed for H-FMC reproducibility via high-resolution ultrasound imaging of the brachial artery during and after forearm occlusion of a normal FMD procedure. Two vascular assessments were conducted for all participants during two separate visits with a minimum of 7 days in between. H-FMC was characterized as the greatest 10-s average constriction occurring after 3-s postocclusion compared to baseline brachial artery diameter and considered present if the percent change was <−0·1%. Results: Of the 120 total vascular assessments performed in this study, 98 of the assessments (80·3%) displayed an H-FMC. H-FMC diameter was not statistically different for intraday comparisons for visit 1 (P = 0·39) or visit 2 (P = 0·55) or interday comparisons between the first (P = 0·61) or second (P = 0·10) assessments. H-FMC percentage was also not statistically different for intra-day comparison for visit 1 (P = 0·94) or visit 2 (P = 0·15) or interday comparisons between the first (P = 0·63) or second (P = 0·16) assessments. Conclusion: These data are supportive of H-FMC being reproducible in young adults and included in future FMD studies. The impact of H-FMC on future CVD risk and development warrants evaluation.