Cardiovascular reactivity in mild hypertension.

Blood pressure and heart rate were monitored in 18 mild hypertensives and 18 normotensive controls matched for age and sex during rest, isometric exercise, carbon dioxide rebreathing, cold pressor test, head-up tilt, radiant heat, head-back tilt and mental arithmetic. Blood pressure and heart rate were higher in the hypertensive than in the normotensive group at rest. During the instructions prior to the mental arithmetic and head-back tilt tests, heart rate increased more in the hypertensive than in the normotensive group while during mental arithmetic performance, blood pressure levels increased more in hypertensives than in normotensive controls. Diastolic blood pressure levels increased more in hypertensives during head-up tilt. In all other conditions, cardiovascular responses were similar in both groups. The results support the view that the sympathetic nervous system contributes to hypertension since the cardiovasculature of mild hypertensives was hyperreactive during tests where sympathetic activity was likely to predominate.