Close relationship between the vasodilator response to acetylcholine in the brachial and coronary artery in suspected coronary artery disease

Background Vasodilator response to acetylcholine (endothelium-dependent dilation) is impaired in the peripherial and coronary circulation in patients with coronary artery disease (CAD). The purpose of this study is to investigate if the vasodilator response to acetylcholine in the brachial artery (BA) correlates with the same response in the coronary artery (CA). Study We measured the flow responses of BA and CA in 57 patients with suspected CAD. Doppler guidewire was placed into the proximal portion of the left BA and the major branch of CA. Acetylcholine was infused at 7.5, 15, and 30 μg/min for 5 min into BA and at 10−8, 10−7, 10−6 M for 3 min into CA, respectively. The flow was calculated by multiplying average peak velocity by cross sectional areas obtained from quantitative angiography. Vasodilator response to acetylcholine was assessed by ratio of acetylcholine-induced flow/baseline flow. Results A total of 33 CAD patients (CAD group, 61±8 years old) and 24 normal coronary patients (NL group, 57±12 years old) were investigated. A strong correlation between the vasodilator response to acetylcholine in BA and CA was observed in both CAD and NL groups, only at two moderate doses of acetylcholine (CAD group, r=0.64, p<0.001, NL group, r=0.87, p<0.001, 15 μg/min vs. 10−7 M; CAD group, r=0.68, p<0.001, NL group, r=0.72, p<0.001, 30 μg/min vs. 10−6 M). No significant correlation was obtained during low dose acetylcholine infusion. Conclusions The brachial artery vasodilator response to optimal acetylcholine doses is a useful surrogate for coronary endothelial function studies.