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Evaluating endothelial function in humans: a guide to invasive and non-invasive techniques
  1. D Tousoulis,
  2. C Antoniades,
  3. C Stefanadis
  1. Athens University Medical School, Hippokration Hospital, Cardiology Department, Athens, Greece
  1. Correspondence to:
    Dr Dimitris Tousoulis
    Athens University Medical School, S Karagiorga Street 69, 166 75, Glifada, Athens, Greece;

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The endothelium regulates vascular homeostasis through the release of a variety of autocrine and paracrine substances, such as nitric oxide (NO), prostacyclin, and the endothelium derived hyperpolarising factor(s).1 Beyond its vasodilatory effects, NO has antiatherogenic properties, inhibits platelet aggregation and adhesion, smooth muscle cell proliferation, leucocyte adhesion, vascular permeability, and inflammatory mechanisms (fig 1).1

Figure 1

 Effects of different stimuli (physical or chemical) on vascular endothelium. Stimuli leading to vasorelaxation in the presence of intact vascular endothelium (such as acetylcholine), produce vasoconstriction when acting directly on the underlying smooth muscle cells, in vascular areas with injured endothelium. CPT, cold pressor stress test; EDHF, endothelium derived hyperpolarising factor; eNOS, endothelial nitric oxide synthase; GC, guanyl cyclase; L-NMMA, NG-monomethyl-L-arginine; MS, mental stress; NO, nitric oxide; SMC, smooth muscle cell.

Several prospective and retrospective studies have shown that evaluation of endothelial function may be useful in identifying subjects at high risk for atherosclerosis, as well as for risk stratification of patients with already established coronary artery disease.2w1 Several invasive and non-invasive techniques have been developed during the last few years to evaluate endothelial function. Invasive techniques, which involve intracoronary or intrabrachial infusions of vasoacting agents, are still considered to be the gold standard for early detection of endothelial dysfunction. In addition, several non-invasive techniques have been developed, with comparable results and good reproducibility. In this article we describe and evaluate the different methods for assessing endothelial function in humans.


Intracoronary infusions of vasoactive agents

Intracoronary agonist infusion, combined with quantitative angiography, is the method of choice for direct quantification of endothelial function in the coronary arteries, since it allows both the evaluation of dose–response relations of endothelial agonists and antagonists, as well as assessing the basal endothelial function by the infusion of nitric oxide synthase (NOS) inhibitors.2 It is well known that intracoronary …

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