Brachial artery flow mediated vasodilation

Brachial artery flow mediated vasodilation

Brachial artery flow mediated vasodilation is considered to be an important way to assess the endothelial function on the bedside. It is a method of provoking release of the potent vasodilator nitric oxide non invasively and measuring its vascular response at the bedside.

A segment of brachial artery is measured by ultrasound and proximal occlusion is applied for a period of 5 minutes. Repeated measurement is taken after 1 minute and within 10 minutes, to assess the flow mediated vasodilation. More than 10% increase in vessel diameter is taken as a positive response.

It may be technically challenging to get good brachial artery images with proximal occlusion which can distort the vessel. Alternative method of induction of distal ischemia, the main vasodilatory stimulus, is by inflating cuff in forearm [1].

As the vascular response may be affected by food, drugs, temperature and sympathetic stimuli, certain precautions are needed. Overnight fasting before the test is recommended. All medications acting on the blood vessels have to be withdrawn for an adequate wash out period.

High fat foods, caffeine, vitamin C and tobacco can affect the flow mediated vasodilation and are avoided in the preceding six hours. Study should be conducted in a quiet, temperature controlled room. A linear array ultrasound transducer of at least 7 MHz frequency is used along with ECG triggering.

Reference

1. Mary C Corretti, Todd J Anderson, Emelia J Benjamin, David Celermajer, Francois Charbonneau, Mark A Creager, John Deanfield, Helmut Drexler, Marie Gerhard-Herman, David Herrington, Patrick Vallance, Joseph Vita, Robert Vogel, International Brachial Artery Reactivity Task Force. Guidelines for the ultrasound assessment of endothelial-dependent flow-mediated vasodilation of the brachial artery. J Am Coll Cardiol. 2002;39(2):257-265.