Weissgerber Tracey L, Davies Gregory A L, Tschakovsky Michael E
Department of Obstetrics, Gynecology, and Reproductive Science, Magee Women's Research Institute, 204 Craft Ave., Pittsburgh, PA 15213, USA.
J Appl Physiol (1985). 2010 May;108(5):1097-105. doi: 10.1152/japplphysiol.00815.2009. Epub 2010 Feb 25.
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.
当手腕袖带充气以阻止血液流向远端组织时，桡动脉直径会减小。这种现象被称为低流量介导的血管收缩（L-FMC），被提议作为一种血管功能测试。关于应与血流介导的血管舒张（FMD）同时测量L-FMC的建议是基于桡动脉数据得出的。然而，心血管疾病预测研究传统上测量肱动脉FMD。因此，研究应确定L-FMC是否发生在肱动脉中。剪切力降低导致L-FMC这一假设尚未得到验证。对活跃未孕（n=17）、不活跃未孕（n=10）、活跃孕（n=15，妊娠34.1±1.2周）和不活跃孕（n=8，妊娠34.2±2.2周）女性的肱动脉和桡动脉L-FMC及FMD进行了评估。在所有组中，桡动脉直径在闭塞期间均显著减小（未孕组，-4.4±4.2%；孕组，-6.4±3.2%）。活跃和不活跃未孕女性以及不活跃孕女性的肱动脉直径没有变化；然而，活跃孕女性的微小减小是显著的。闭塞使两条动脉的剪切速率均降低，但L-FMC仅发生在桡动脉中。桡动脉L-FMC与剪切速率的降低无关。L-FMC（负值）与FMD（正值）之间的正相关表明，经历更大L-FMC的女性中桡动脉FMD可能会降低。研究应阐明调节L-FMC的潜在刺激因素和机制，并验证内皮功能障碍表现为肱动脉L-FMC增强但桡动脉L-FMC减弱这一假设。
