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Medicine

Ultrasound Assessment of Endothelial Function: A Technical Guideline of the Flow-mediated Dilation Test

Published: April 27th, 2016

DOI:

10.3791/54011

1Division of Clinical and Translational Sciences, Georgia Prevention Institute, Georgia Regents University, 2Sport and Exercise Science Research Institute, University of Ulster

The flow mediated dilation (FMD) test is the most commonly utilized, non-invasive, ultrasound assessment of endothelial function in humans. Although the FMD test has been related with the prediction of future cardiovascular disease and events, it is a physiological assessment with many inherent confounding factors that need to be considered.

Cardiovascular disease is the primary cause of mortality and a major cause of disability worldwide. The dysfunction of the vascular endothelium is a pathological condition characterized mainly by a disruption in the balance between vasodilator and vasoconstrictor substances and is proposed to play an important role in the development of atherosclerotic cardiovascular disease. Therefore, a precise evaluation of endothelial function in humans represents an important tool that could help better understand the etiology of multiple cardio-centric pathologies.

Over the past twenty-five years, many methodological approaches have been developed to provide an assessment of endothelial function in humans. Introduced in 1989, the FMD test incorporates a forearm occlusion and subsequent reactive hyperemia that promotes nitric oxide production and vasodilation of the brachial artery. The FMD test is now the most widely utilized, non-invasive, ultrasonic assessment of endothelial function in humans and has been associated with future cardiovascular events.

Although the FMD test could have clinical utility, it is a physiological assessment that has inherited several confounding factors that need to be considered. This article describes a standardized protocol for determining FMD including the recommended methodology to help minimize the physiological and technical issues and improve the precision and reproducibility of the assessment.

Cardiovascular disease is the leading cause of morbidity and mortality worldwide. Dysfunction of the vascular endothelium represents an initial phase toward the development of multiple vascular-related diseases1. Hence, an accurate assessment of endothelial function in humans represents an important technique that could help in understanding the etiology of multiple cardiovascular pathologies, with the ultimate goal of improving the efficacy of the treatment and prevention of disease.

Endothelium

The endothelium is a monolayer of cells that synthesizes numerous vasoactive substances, such as nitric oxi....

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NOTE: The following FMD procedure is routinely conducted during vascular assessment studies in the Laboratory of Integrative Vascular and Exercise Physiology (LIVEP). All procedures followed the principles of the Declaration of Helsinki and were approved by the Institutional Review Board at Georgia Regents University. All participants were informed of the objectives and possible risks of the technique before written consent for participation was obtained. Figure 1 illustrates a schematic summary of the essential elements tha.......

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Baseline characteristics from an apparently healthy cohort group are presented in Table 1. The most common variables of FMD testing conducted in the Laboratory of Integrative Vascular and Exercise Physiology (LIVEP) are presented in Table 2. The following variables are considered the main FMD parameters to analyze by the published FMD tutorial4 and guidelines36.

Baseline an.......

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Introduced in 198920, the FMD test has been widely used in humans as a non-invasive measure of endothelial function. FMD has not only been shown to predict future vascular-related disease risk19,52,53, lower FMD values have been show to strongly correlate with cardiovascular impairments24,25,54. Although there are other techniques to assess endothelial function, both invasively (coronary angiography) and non-invasively (venous plethysmography and finger plethysmography), FMD has been the .......

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The authors would like to thank the many subjects and patients who have participated in our studies in which we have evaluated endothelial function using the FMD test.

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Name Company Catalog Number Comments
Doppler ultrasound GE Medical Systems  Logiq 7 Essential to include Duplex mode for simultaneous acquisition of B-mode and Doppler
Electrocardiographic (ECG) gating  Accusync Medical Research Accusync 72
12-MHz Linear array transducer  GE Medical Systems 11L-D A high-resolution linear array probe is essential
Forearm occlusion cuff  D.E. Hokanson SC5 5 x 84 cm
Ultrasound transmission gel  Parker 01-08
Rapid cuff inflator D.E. Hokanson E-20 AG101
Sterotactic-probe holder Flexabar  18047 Magnetic base fine adjustor
Edge detection analysis software Medical Imaging Applications Brachial Analyzer 5

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