Table 3.

Advantages and disadvantages of different endothelial dysfunction assessment techniques

Method	Advantages	Disadvantages
Quantitative coronary angiography	• Directly quantifies endothelial function in the vascular bed of interest • Allows to establish the relationship between agonists and antagonists • Allows to examine basal endothelial function after administration of NOS antagonists	• Invasive • Expensive • Risks related to coronary artery catheterization: stroke, MI, infection
Venous occlusion plethysmography	• More accessible • High reproducibility, validity • Allows to establish the relationship between agonists and antagonists • Allows to examine basal endothelial function after administration of NOS antagonists	• Semi-Invasive • Indirect measure of blood flow • Time consuming • Limited applications in exercise • Risks: median nerve injury, infections, vascular injury
Doppler ultrasound	• Non-invasive • Possible to measure blood flow velocity Continuous wave Doppler • Simpler hardware implementation • Ability to measure high blood flow velocity • Wide depth range Pulse wave Doppler • Measurement range definition	• Precise positioning over a large blood vessel at an appropriate angle • Expensive • Contact gel Continuous wave Doppler • Measurement range ambiguity Pulse wave Doppler • For use by qualified personnel only • “Aliasing” artefacts at high blood flow velocities • Measurement depth limitations
Arterial tonometry	• Non-invasive • Safe and rapid • Less operator dependent than FMD • Accurately records the arterial blood pressure waveform • Can reflect basal endothelial function	• Influenced by structural vascular aspects and less by the endothelium • Sensitivity to the autonomic tone • Temperature dependent • Requires clipping of long fingernails • Movement artefacts
Flow-mediated dilation	• Non-invasive • Safe, rapid • Well correlated with coronary endothelial function • Blood flow is a physiological stimulus of vasodilation, like agonists • Gold-standard method	• Low resolution influenced by the vessel size • Inter-measurement variability • Operator dependence • Poor reproducibility • Lack of strict protocols
Intravascular ultrasound	• Excellent for evaluation of plaque burden and composition	• Invasive • Limited availability • Iodinated contrast agent required (for catheter positioning)

FMD, Flow-mediated dilation; MI, myocardial infarction; NOS, nitric oxide synthase