Strong Relationship between Vascular Function in the Coronary and Brachial Arteries: A Clinical Coming of Age for the Updated Flow-Mediated Dilation Test?

Early detection of coronary artery dysfunction is of paramount cardiovascular clinical importance, but a noninvasive assessment is lacking. Indeed, the brachial artery flow-mediated dilation test only weakly correlated with acetylcholine-induced coronary artery function (r=0.36). However, brachial artery flow-mediated dilation methodologies have, over time, substantially improved. This study sought to determine if updates to this technique have improved the relationship with coronary artery function and the noninvasive indication of coronary artery dysfunction. Coronary artery and brachial artery function were assessed in 28 patients referred for cardiac catheterization (61±11 years). Coronary artery function was determined by the change in artery diameter with a 1.82 μg/min intracoronary acetylcholine infusion. Based on the change in vessel diameter, patients were characterized as having dysfunctional coronary arteries (>5% vasoconstriction) or relatively functional coronary arteries (<5% vasoconstriction). Brachial artery function was determined by flow-mediated dilation, adhering to current guidelines. The acetylcholine-induced change in vessel diameter was smaller in patients with dysfunctional compared with relatively functional coronary arteries (-11.8±4.6% versus 5.8±9.8%, P<0.001). Consistent with this, brachial artery flow-mediated dilation was attenuated in patients with dysfunctional compared with relatively functional coronaries (2.9±1.9% versus 6.2±4.2%, P=0.007). Brachial artery flow-mediated dilation was strongly correlated with the acetylcholine-induced change in coronary artery diameter (r=0.77, P<0.0001) and was a strong indicator of coronary artery dysfunction (receiver operator characteristic=78%). The current data support that updates to the brachial artery flow-mediated dilation technique have strengthened the relationship with coronary artery function, which may now provide a clinically meaningful indication of coronary artery dysfunction.