title: Low flow-mediated constriction occurs in the radial but not the brachial artery in healthy pregnant and nonpregnant women.
abstract: Radial artery diameter decreases when a wrist cuff is inflated to stop blood flow to distal tissue. This phenomenon, referred to as low flow-mediated vasoconstriction (L-FMC), was proposed as a vascular function test. Recommendations that L-FMC be measured concurrently with flow-mediated dilation (FMD) were based on radial artery data. However, cardiovascular disease prediction studies traditionally measure brachial artery FMD. Therefore, studies should determine whether L-FMC occurs in the brachial artery. The hypothesis that reduced shear causes L-FMC has not been tested. Brachial and radial artery L-FMC and FMD were assessed in active nonpregnant (n=17), inactive nonpregnant (n=10), active pregnant (n=15, 34.1+/-1.2 wk gestation), and inactive pregnant (n=8, 34.2+/-2.2 wk gestation) women. Radial artery diameter decreased significantly during occlusion in all groups (nonpregnant, -4.4+/-4.2%; pregnant, -6.4+/-3.2%). Brachial artery diameter did not change in active and inactive nonpregnant, and inactive pregnant women; however, the small decrease in active pregnant women was significant. Occlusion decreased shear rate in both arteries, yet L-FMC only occurred in the radial artery. Radial artery L-FMC was not correlated with the reduction in shear rate. L-FMC occurs in the radial but not the brachial artery and is not related to changes in shear rate. Positive correlations between L-FMC (negative values) and FMD (positive values) suggest that radial artery FMD may be reduced among women who experience greater L-FMC. Studies should clarify the underlying stimulus and mechanisms regulating L-FMC, and test the hypothesis that endothelial dysfunction is manifested as enhanced brachial artery L-FMC, but attenuated radial artery L-FMC.
authors.affiliation: Department of Obstetrics, Gynecology, and Reproductive Science, Magee Women's Research Institute, 204 Craft Ave., Pittsburgh, PA 15213, USA. weissgerbertl@mwri.magee.edu
authors.forename: Tracey L
authors.initials: TL
authors.lastname: Weissgerber
authors.forename: Gregory A L
authors.initials: GA
authors.lastname: Davies
authors.forename: Michael E
authors.initials: ME
authors.lastname: Tschakovsky
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D001794:Blood Pressure; D001916:Brachial Artery / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005080:Exercise Test; D005260:Female; D005865:Gestational Age; D006339:Heart Rate; D006801:Humans; D006940:Hyperemia / Q000503:physiopathology; D009043:Motor Activity; D017156:Photoplethysmography; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular / Q000000981:diagnostic imaging / Q000503:physiopathology*; D017534:Radial Artery / Q000000981:diagnostic imaging / Q000503:physiopathology*; D012039:Regional Blood Flow; D057185:Sedentary Behavior; D018608:Ultrasonography, Doppler; D014661:Vasoconstriction; D055815:Young Adult