TABLE 1.

Comparison of the invasive and non-invasive methods for assessing endothelial function.

Modality	Strengths	Limitations
Coronary angiography	• Gold standard method • Direct visualization and quantitation of endothelial function • Able to assess dose-response • Precise and accurate results	• Invasive • Expensive • Vasoactive medications can have systemic effects • Largely limited to clinical studies
Brachial artery flow mediated dilatation	• Non-invasive • Cost-effective • Validated software for automated analyses • Well correlated with coronary endothelial function	• Operator dependent • Technically challenging to obtain optimal images • Variable measurements, which limit comparability and reproducibility
Forearm plethysmography/Applanation tonometry	• Minimal training required • Inexpensive • Portable • Well tolerated • Can provide indirect information on the structure of small resistance arteries	• No clear cutoff values • Used mostly for mechanistic research studies • Limited reproducibility • Requires specialized training for standardization • Findings may not reflect endothelial function only
Venous occlusion plethysmography	• Validated technique • Reproducible • Easier to access than coronary arteries	• Invasive • Limited ability to compare application between individuals or groups
Positron emission tomography	• Well-validated in animal and human studies • Automated software for quantitative analysis	• Radiation exposure • Expensive • Lack of easy access
Computed tomography	• Good spatial resolution • Relatively cost-effective • Fast image acquisition	• Radiation exposure • Image may be compromised by increased heart rate • Calcium related beam hardening may result in artifacts
Magnetic resonance imaging	• High spatial and temporal resolution • No ionizing radiation • Cardiac structure and function assessment included	• Limited availability • Expensive • Long study length • Limited use in patients with arrhythmias, claustrophobia or implanted devices