Brachial artery ultrasound is a commonly used and widely accepted method to evaluate the peripheral macrovascular endothelial function.
Inflating the blood pressure cuff at suprasystolic pressures for 5 minutes occludes the upper arm proximal to the ultrasound measurement. When this occlusion is released, endothelial-dependent, nitric oxide NO-driven, flow-mediated dilation (FMD) of the brachial artery occurs due to an increase in shear stress. Both diameter and blood velocity are measured before and after occlusion at the end of the diastole. The results are reported as a percent change from baseline.
The reported vascular response to increased flow has been shown to be a surrogate for measuring coronary endothelial function.
The stimuli for measuring endothelial reactivity include reactive hyperaemia, exercise, mental stress, or sympathetic nervous activation through the cold pressor test.
Peripheral endothelial dysfunction, as measured by FMD of the brachial artery, was shown to be associated with a higher rate of incident adverse cardiovascular disease (CVD) events during a five-year follow-up period in the MESA study.
For the screening test, an ultrasound is not needed. Just inflate the blood pressure cuff at suprasystolic pressures for five minutes and occlude the upper arm. When the occlusion is released, there is an endothelial-dependent, nitric oxide NO-driven, flow-mediated dilation and increased velocity of the brachial artery. Clinically, this presents as a sudden feeling of warmth in the arm, which suggests normal endothelial function.