Sympatho-adrenal and cardiovascular responses during hand-grip in human hypertension

Circulating norepinephrine and epinephrine levels were correlated with echocardiographic indices of cardiovascular function during isometric exercise (hand-grip at 30% of maximum force for 3 minutes) in 19 patients with mild essential hypertension and 9 normotensive subjects. At the end of the third minute of exercise, plasma norepinephrine and epinephrine, blood pressure and heart rate, increased significantly and similarly in both groups of patients. In contrast, peripheral resistance tended to increase in hypertensives but tended to decrease in normotensives. Moreover, indices of ventricular function increased in normotensives but decreased in hypertensives. At the end of the exercise, systolic and diastolic blood pressures were directly correlated with epinephrine levels in normotensives but were correlated only with norepinephrine levels in hypertensives. On the other hand, norepinephrine and epinephrine levels were inversely correlated with changes in indices of left ventricular performance in hypertensive patients only. These results demonstrate that during isometric exercise, the increase in blood pressure in normotensives is associated with a sympatho-adrenal activation of cardiac performance and contractility, while in hypertensives the increase in blood pressure results mainly from an increase in peripheral resistance associated with a reduction in cardiac performance and contractility, despite a similar sympatho-adrenal activation in both groups. These differences in the hemodynamic responses may be compatible with the hypothesis of beta-adrenoceptor desensitization or structural alterations of the cardiovascular system in hypertensive patients.