A Vascular Abnormality in Hypertension

Forearm blood flow measurements have been made at rest and after 8 to 10 minutes arterial occlusion in 50 normal and 131 untreated hypertensive subjects. The latter group comprised 91 with essential hypertension; 11 with chronic renal disease (nephritis or pyelonephritis); 21 with renovascular disease; and eight with primary aldosteronism. The resting blood flow increased with the rising pressure in patients with mild hypertension but there was a significant increase in the resting resistance in the more severe cases. The average minimal resistance obtained during reactive hyperemia was greater in hypertensive (3.1 SE 1.0 units) than in normal subjects (2.0 SE 0.07 units). This abnormality was related to the level of blood pressure but not to the duration of the disease. Patients with renovascular disease or aldosteronism presented the same vascular fault as the more common causes of hypertension. Evidence is presented to show that the reactive hyperemia produced maximal dilatation of the forearm vasculature, and acute elevation in pressure in normotensive or acute depression of pressure in hypertensive subjects did not influence the level of resistance achieved by reactive hyperemia. It is concluded that the blood vessels themselves are abnormal in hypertension and that this abnormality may not be related to the activity of vascular smooth muscle.