Noninvasive assessment of endothelial dysfunction in essential hypertension: Comparison of the forearm microvascular reactivity with flow-mediated dilatation of the brachial artery

Abstract

Endothelial dysfunction is detectable both in the forearm skin microcirculation by laser Doppler flowmetry and in the brachial artery by Duplex Ultrasound. The aim of the study was to evaluate whether endothelium-dependent vasodilation in the forearm microcirculation is related to endothelium-dependent flow mediated dilation (FMD) of the brachial artery. In 22 treated male essential hypertensive patients (EHT) who had impaired FMD of the brachial artery, and in 11 male normotensive subjects (NT) we measured first the postocclusive reactive hyperemic response (PORH), then the effect of two doses of acetylcholine (ACh) and sodium nitroprusside (SNP) on the forearm skin microcirculation. FMD resulted from forearm reactive hyperemia induced by 5 minutes of ischaemia and the vasodilation induced by sublingual nitroglycerine (GTN) were also measured. Responses were calculated as the maximal percent increase above baseline. PORH and the responses to ACh were significantly (p < 0.05, p <0.01) reduced in EHT (272 ± 180, 177 ± 194, 463 ± 302) as compared to NT (409 ± 123, 470 ± 467, 805 ± 603). Response to SNP was similar. FMD was significantly (p < 0.001) reduced in EHT as compared to NT (3.98 ± 2.2 vs 9.3 ± 2.88), while response to GTN was similar. There was no significant relationship (p = n.s.) either between maximal response to ACh and FMD (r = 0.28), or between PORH and FMD (r = )0.01). Endothelial dysfunction was detectable with both methods in EHT. Our results show that endotheliumdependent vasodilation in forearm microcirculation is not related to FMD of the brachial artery. This can be explained by the differences in vascular beds and mechanism involved in the hyperemic response.