Plasma norepinephrine and age as determinants of systemic hemodynamics in men with established essential hypertension

Two primary predictor variables, age and supine plasma norepinephrine, were studied with respect to their influences on supine hemodynamic variables in 52 white men with essential hypertension who were 23 to 67 years of age and had been off active therapy for at least 4 weeks. Plasma norepinephrine was related to age (r = 0.39, p < 0.01), correlated closely with mean arterial pressure (MAP; r = 0.54, p < 0.0002) and systemic vascular resistance (r = 0.49, p < 0.0005), and was related inversely to cardiac output (r = -0.26, p < 0.06) and stroke volume (r = -0.31, p < 0.05). Age correlated weakly with MAP (r = 0.31, p < 0.05) and more strongly with systemic vascular resistance (r = 0.46, p < 0.005) but was negatively related to cardiac output (r = -0.41, p < 0.005) and heart rate (r = -0.33, p < 0.05). Weight did not correlate with any of the hemodynamic variables. Partial regression techniques yielded significant residual correlations between age-adjusted plasma norepinephrine and MAP (r = 0.42, p < 0.005) or systemic vascular resistance (r = 0.38, p < 0.005). Residual correlations with cardiac output (r = -0.34, p < 0.05), heart rate (r = -0.36, p < 0.02), and systemic vascular resistance (r = 0.33, p < 0.05) remained after adjusting age for the corresponding plasma norepinephrine values. These correlations demonstrate the independent effects of sympathetic nervous activity and the aging process on the systemic vasoconstriction and decreased cardiac function observed in essential hypertension.