Functional relationships between plasma renin activity and hemodynamic indices in essential arterial hypertension

: Vasoconstriction-volume analysis postulates that arteriolar vasoconstriction is the mechanism of blood pressure elevation in patients with "high-renin" essential hypertension while a volume expanded state with relatively dilated arterioles sustains "low renin" essential hypertension. To test this hypothesis we carried out hemodynamic and PRA studies in 43 essential hypertensives. Cardiac index was directly related to PRA (r=0,41; p less than 0,01), by contrast, peripheral vascular resistances and plasma volume were unrelated to PRA. The data do not support the bipolar hypothesis since vasoconstriction and volume expansion are associated with unpredictable changes in PRA. The direct relationship between CI and PRA may be interpreted as the result of a common factor (presumably sympathetic nervous system) governing both functions.