Simultaneous Assessment of Systemic and Coronary Endothelial Function

Besides lining the inner surface of vessels, endothelium serves other important functions, including keeping blood and platelets in a nonthrombotic status, avoiding intravascular activation of inflammatory cells, and finally what is possibly the most important function—and definitely the most actively investigated—namely regulation of vascular tone and blood flow. To a large extent, these various functions can be traced to the effects of nitric oxide (NO) produced by a healthy endothelium.1,2See Article by Iantorno et al A first corollary of the theory, which puts healthy endothelium center stage in vascular homeostasis, is that the opposite condition (ie, endothelial dysfunction) fosters vasoconstriction, thrombosis, and vascular smooth muscle cell proliferation. Accordingly, development of endothelial dysfunction can be viewed as a mechanistic link between cardiovascular risk factors (hypercholesterolemia, hypertension, diabetes mellitus, and smoking) and morbidity.3,4 A second corollary then is that, should we be able to gauge endothelial (dys)function, we would also be able to check vascular health, and consequently to afford better assessment of cardiovascular risk and improved prognostication of vascular events.5The central question is how to translate a nice theory into clinical practice. How can we reliably measure endothelial function? Because NO-mediated vascular dilatation apparently goes hand-in-glove with the various activities of healthy endothelium, it would seem logical to measure endothelium-mediated dilatation and, through it, assess the degree of vascular (dys)function and possibly correlate it with future cardiovascular events.6 The problem, though, is the choice of the most appropriate methodology.Since the pivotal study by Ludmer et al,7 which demonstrated the lack of vasodilation in response to intracoronary acetylcholine in patients with atherosclerotic coronary arteries, assessment of response to acetylcholine of coronary artery diameter and flow has been considered the gold standard for endothelial function evaluation.8 However, intracoronary catheterization has …