New approaches to the evaluation of coronary endothelial function.

itric oxide (NO) is released by endothelial cells in response to hemodynamic forces (eg, shear stress, axial strain) and has vasodilator and anti-atherogenic properties. Endothelial dysfunction is associated with diminished bioavailability of NO and poor prognosis in patients with traditional cardiovascular risk factors. Rather than directly measuring NO concentrations, most previous studies have measured vasodilator activity as a proxy, including assessment of flow-mediated dilation (FMD) and response to intracoronary injection of acetylcholine (ACh).