Role of autonomic and non-autonomic circulatory components in borderline hypertension in young men.

The role of autonomic nervous system and non-autonomic components in hemodynamic abnormalities of young patients with borderline hypertension was examined by comparing the effects of sequential pharmacological autonomic blockade on hemodynamics between 8 patients with borderline hypertension (mean age 20.0 +/- 0.2) and 10 normotensive subjects (mean age 19.3 +/- 0.2). Propranolol (0.2 mg/Kg), atropine (0.04 mg/Kg), and phenotolamine (10 or 15 mg) were given intravenously in that order to produce "total" autonomic blockade. Increased cardiac index, heart rate, and mean arterial blood pressure with normal peripheral vascular resistance were noted at rest in patients with borderline hypertension. Cardiac index and heart rate in patients with borderline hypertension were normalized by propranolol, but after "total" autonomic blockade mean arterial blood pressure and peripheral vascular resistance were higher in patients with borderline hypertension as compared to those in normotensive subjects. These results suggest that, although autonomic nervous system control of circulation is abnormal, non-autonomic components play an important role in maintaining increased peripheral vascular resistance in borderline hypertension in young men.