[Borderline essential hypertension and the adrenergic nervous system. Identification assay].

The physiopathological participation of the sympathetic nervous system in borderline hypertension may be assessed on the following criteria: I) A quantitative rather than qualitative classification of hypertensive patients shows a group of patients with diastolic pressures between 75 and 95 mm Hg, in whom increases in cardiac output are closely related to increases in heart rate; 2) Clinical examination, which should include an assessment of personality, shows a higher incidence of signs in favour of an increase (absolute or relative) in sympathetic activity; 3) Plasma catecholamine levels are not helpful: the absence of raised concentrations could be related to increased excretion, especially by the kidney; 4) Urinary excretion of catecholamines is slightly raised: this is very evident when homovanillic acid levels are assessed.