Vasodilator effects of enalapril in patients with arterial hypertension

Although it has been recognized that enalapril lowers blood pressure by reducing the total peripheral vascular resistance, its direct effect on blood vessels is largely unknown. Little information is available about the influence of enalapril on the different vascular regions. Ten patients with moderate essential hypertension were treated with enalapril 20 mg daily in a double-blind, placebo controlled cross-over study for six weeks during each period. Blood pressure and heart rate were measured in supine, sitting and standing position. Venous capacity was derived from pressure volume curves plotted simultaneously at forearm and calf. Arterial blood flow at rest and during reactive hyperemia was measured at calf and finger by plethysmography. Enalapril increases venous capacity in upper and lower limbs in patients with moderate essential hypertension. Also, there is vasodilation of calf and finger arteries both at rest and during reactive hyperemia. Finger and calf arteries contribute to the decrease of the total peripheral vascular resistance during treatment with enalapril; thus, ACE inhibition is capable of correcting the increased peripheral resistance which often is the main cause of arterial hypertension.