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. 2021 Aug 17;8:716938. doi: 10.3389/fcvm.2021.716938

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Copyright © 2021 Stoner, Barone Gibbs, Meyer, Fryer, Credeur, Paterson, Stone, Hanson, Kowalsky, Horiuchi, Mack and Dave.

This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

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Schematic of the flow-mediated dilation (FMD) test. (A) Shear stress created by red blood cells flowing past the vessel wall is detected by mechanoreceptors in the endothelium, triggering a signal cascade whereby vasodilators, nitric oxide (NO) prostacyclin (PGI₂) and endothelial hyperpolarizing factor (EDHF) are produced. Vasodilators subsequently diffuse to the vascular smooth muscle cells, prompting vasodilation. (B) Vessel diameter and shear rate responses before and after 5-min ischaemic stimulus. eNOS, endothelial nitric oxide synthase; COX-2, cyclooxygenase-2.