Non-invasive detection of endothelial dysfunction in patients with essential hypertension

The endothelium regulates vascular tone through the release of vasoactive agents that act on the underlying vascular smooth muscle. This endothelial function is impaired in certain cardiovascular conditions including atherosclerosis, and hypercholesterolemia. However, in patients with essential hypertension it is unclear whether endothelium-dependent vasodilation is impaired. Using high-resolution ultrasound, we measured the diameter of the brachial arteries at rest, during reactive hyperaemia (with increase flow causing endothelium-dependent dilatation), and after sublingual glyceryl trinitrate (GTN; causing endothelium-independent dilatation) in 42 subjects, consisted of 21 controls with normal blood pressure [mean(SD) arterial blood pressure, 92±7 mmHg] and 21 patients with established essential hypertension (mean arterial blood pressure, 123±12 mmHg). The results showed that in patients with essential hypertension, flow-mediated dilatation in arteries was much reduced in comparison with the control group (4.6%±2.8% vs. 12.4%±2.9%, P<0.001), However, there was no significant difference in response to GTN between the two groups (19.8%±6.0% vs. 24.5%±10.2%, P=0.186). This indicates that endothelium-dependent vasodilation is impaired in patients with essential hypertension.