Measurement of endothelial function by brachial artery flow-mediated vasodilation.

In response to physical and chemical stimuli, the endothelium regulates vascular tone through the release of vasodilators, such as nitric oxide, and vasoconstrictors, such as endothelin. Increased blood flow is an important stimulus for endothelium-mediated vasodilation (flow-mediated vasodilation). Brachial artery flow-mediated vasodilation can be assessed using high-frequency ultrasound assessment of changes in brachial artery diameter after a 5-minute blood pressure cuff arterial occlusion. Endothelial dysfunction is demonstrated as reduced vasodilation, which is usually associated with the presence of coronary risk factors. Brachial artery flow-mediated vasodilation correlates with coronary artery flow-mediated vasodilation. Both indexes have been shown to predict long-term cardiovascular events. Whereas the clinical applicability of brachial artery flow-mediated vasodilation is unclear, it has become a frequently employed measure of endothelial function.