Disparate hemodynamic and sympathoadrenergic responses to isometric and mental stress in essential hypertension

The hemodynamic and sympathoadrenergic responses during isometric handgrip and mental arithmetic tests were compared in 18 patients with mild essential hypertension. Mean blood pressure increased significantly after both maneuvers (27% during isometric stress and 10.7% during mental stress), but the increase was significantly higher during isometric stress (p less than 0.001). Both stressors increased the heart rate (p less than 0.001) and cardiac output (p less than 0.001). However, the total peripheral resistance behaved differently, for it increased during isometric stress (p less than 0.05) and remained unchanged during mental stress. Both stressors increased the epinephrine levels (p less than 0.005), but only isometric stress increased the norepinephrine levels (p less than 0.001). It is concluded that both stressors increase cardiac output by way of an increase in heart rate, but isometric stress also increases total peripheral resistance and thus causes a greater increase in arterial pressure. Isometric stress activates both the adrenergic and noradrenergic systems, thereby accounting for the exaggerated response in arterial pressure, whereas mental stress stimulates the adrenergic system only.