Non-invasive assessment of endothelial function - relation between vasodilatory responses in skin microcirculation and brachial artery

Objective: To compare different non-invasive methods for determination of human endothelial function in peripheral circulation. Design: Observational, cross-sectional study in 39 healthy subjects (21 females, age 17-56 years). Setting: Vascular research laboratory at university hospital. Methods: Laser Doppler (LD) flowmetry was used to compare skin microvascular perfusion changes during postocclusive reactive hyperaemia with those induced by iontophoretic administration of acetylcholine (ACh), an endothelial-dependent vasodilator. LD measurements were compared with ultrasonographic measurements of postocclusive flow-mediated dilatation (FMD) in the brachial artery (n = 21). Results: Local ACh induced a larger and more sustained skin perfusion increase than reactive hyperaemia after 4 min of regional arterial occlusion (P<0.001). A significant correlation was found between the magnitude of ACh-induced vasodilatation and peak reactive hyperaemia, both in absolute (r = 0.62, P<0.001) and relative terms (r = 0.58, P<0.001). A correlation was also found between brachial artery FMD and the magnitude of ACh-induced skin perfusion increase (r = 0.43, P<0.05) but not between FMD and reactive hyperaemia. Conclusion: Endothelial function, an early marker of cardiovascular risk, can be non-invasively assessed and graded by LD and FMD-measurements and despite inherent differences, both methods do correlate.