Endothelial function can be non-invasively evaluated using Brachial (or Radial) artery reactivity testing (BART) as a measure of flow-mediated dilation (FMD). Since it's beginnings in 1989, the study of FMD has now taken on an expanded role in the understanding of endothelial physiology. FMD is an endothelial dependent process that reflects relaxation of a conduit artery when exposed to shear stress. Increased flow, and thereby increased shear stress, through the brachial artery occurs after post occlusive reactive hyperemia. Several studies have suggested that the maximal increase in diameter occurs after approximately 60 seconds after the release of the occlusive cuff or after 45-60 seconds after peak reactive hyperemia blood flow. The increase in diameter at this time is prevented by the NO synthase inhibitor, N-G monomethyl-L-arginine, indicating that it is an endothelial dependent process mediated by NO. Other measures of vasodilator response include time to maximum response, duration of the vasodilator response, and the area under the dilation curve .An impairment of endothelial function, via FMD assessment by BART, has been shown to correlate with risk factors for coronary artery disease (smoking, hyperlipidemia, diabetes mellitus) and adverse cardiovascular events.