[Labile arterial hypertension and sympathetic tonus. Hemodynamic study].

Cardiac output, cardiopulmonary (CPBV) and total (TBV) blood volumes, vascular reactivity to norepinephrine and dopamine B hydroxylase (DBH) were determined in 41 borderline hypertensives patients in comparison with 28 normal subjects. Cardiac output (P less than 0.001) and CPBV/TBV ratio (P less than 0.01) were significantly increased. The ratio was directly correlated to the pressor-response to norepinephrine (P less than 0.01) and the DBH level (P less than 0.005). The results suggest that sympathetic overactivity plays a dominant role in the cardiac output elevation of borderline hypertensive patients.