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

Background: The ultrasound assessment of brachial artery flow-mediated vaso dilation provides a noninvasive means for measuring endothelial function. T he test is performed using either upper or lower arm blood pressure cuff ar terial occlusion to induce hyperemia. Upper arm occlusion produces a greate r hyperemic stimulus. Brachial artery flow-mediated vasodilation is abnorma l 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 subje cts, 10 without and 10 with a single risk factor (hypertension, hypercholes terolemia or cigarette smoking) using both the upper and lower arm occlusio n 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 s ignificantly greater (p < 0.01) using the upper versus the lower arm techni que in both the normal (530 +/- 152 vs. 383 +/- 51%) and the risk factor (5 83 +/- 153 vs. 409 +/- 114%) groups. Flow-mediated vasodilation was signifi cantly greater ip < 0.01) using the upper arm versus the lower arm occlusio n technique in both the normal (13.4 +/- 5.3 vs. 5.6 +/- 3.4%) and risk fac tor (7.9 +/- 3.6 vs. 3.9 +/- 2.2%) groups. Vasodilation was significantly g reater (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 s tatistically 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 brachia l artery flow-mediated vasodilation results in significantly greater hypere mia and vasodilation. Flow-mediated vasodilation obtained using the upper a rm technique better separates subjects with and without coronary risk facto rs.