A comparison of brachial artery flow-mediated vasodilation using upper and lower arm arterial occlusion in subjects with and without coronary risk factors

Abstract

Background: The ultrasound assessment of brachial artery flow-mediated vasodilation provides a noninvasive means for measuring endothelial function. The test is performed using either upper or lower arm blood pressure cuff arterial occlusion to induce hyperemia. Upper arm occlusion produces a greater hyperemic stimulus. Brachial artery flow-mediated vasodilation is abnormal in the presence of coronary risk factors. Hypothesis: The study sought to compare the ability of the upper and lower arm occlusion techniques to differentiate endothelial function in subjects with and without risk factors. Methods: We measured brachial artery flow-mediated vasodilation in 20 subjects, 10 without and 10 with a single risk factor (hypertension, hypercholesterolemia, or cigarette smoking) using both the upper and lower arm occlusion techniques (5 min blood pressure cuff occlusion). Using 11 MHz ultrasound, Doppler blood flow velocities were measured before and immediately after cuff deflation. Brachial artery vasodilation was measured 1 min after cuff deflation, compared with baseline, and expressed as a percent increase. Results: The immediately postocclusion hyperemia (% increase in flow) was significantly greater (p<0.01) using the upper versus the lower arm technique in both the normal (530 ± 152 vs. 383 ± 51%) and the risk factor (583 ± 153 vs. 409 ± 114%) groups. Flow-mediated vasodilation was significantly greater (p<0.01) using the upper arm versus the lower arm occlusion technique in both the normal (13.4 ± 5.3 vs. 5.6 ± 3.4%) and risk factor (7.9 ± 3.6 vs. 3.9 ± 2.2%) groups. Vasodilation was significantly greater (p<0.01) in the normal subjects than in the risk factor subjects (13.4 ± 5.3 vs. 7.9 ± 3.6%) using the upper arm technique, but was not statistically different in the two groups using the lower arm technique. Conclusions: Our study demonstrates that upper arm compared with lower arm cuff occlusion undertaken to induce hyperemia for the assessment of brachial artery flow-mediated vasodilation results in significantly greater hyperemia and vasodilation. Flow-mediated vasodilation obtained using the upper arm technique better separates subjects with and without coronary risk factors.