Ambulatory blood pressure and endothelium-dependent vasodilation in hypertensive patients

Endothelial function is important for local vascular regulation and an abnormal endothelium-dependent vasodilatation (EDV) has been observed in subjects with essential hypertension. As ambulatory blood pressure (ABP) is more closely related to target organ damage than office blood pressure, this study investigated also if 24-h ABP is more closely related to an impaired EDV than office blood pressure recordings. In a group of 25 untreated patients with essential hypertension and an age- and sex-matched control group (n = 21) endothelial function was evaluated by measurements of forearm blood flow (FBF) during local intra-arterial infusions of metacholine (evaluating EDV) and sodium nitroprusside (evaluating endothelium independent vasodilation, EIDV). FBF was measured with venous occlusion plethysmography. Both office mean artery pressure (MAP; r= -0.57, p < 0.001) and 24-h ABP (r = 0.40, p < 0.01) were related to the endothelial vasodilator function (EDV to EIDV ratio) in an inverse way, but ABP was not superior to office blood pressure recordings. Within the hypertensive group, pronounced white-coat effect (office minus daytime ABP) was associated with a reduced,EDV (r= 0.41, p < 0.05). The degree of night-time decline in blood pressure ("dipping") showed no correlation to EDV. In conclusion, the finding that ABP was no more closely related to the endothelial vasodilator function than office blood pressure recordings might be due to an increased mental alertness affecting EDV in some hypertensive subjects, as suggested by the finding of a reduced EDV in those with a pronounced white-coat effect.