The sympathetic system in hypertension.

Several experimental observations accumulated during recent years have suggested an active participation of the sympathetic system in the pathogenesis and maintenance of hypertension in various experimental models of hypertension. The evaluation of sympathetic tone by various indirect means in human hypertension has also revealed that the sympathetic system plays an important role in the maintenance of hypertension in a subgroup of the human hypertensive population. The study of circulating catecholamines, which appears to be the best and most reliable indirect means to evaluate the sympathetic activity in the human, at present, has indicated that 25 to 40 per cent of patients with essential hypertension are characterized by higher basal circulating catecholamines and by a higher sympathetic reactivity in response to postural changes. These hyperadrenergic patients are also characterized by a higher heart rate, heart contractility, cardiac index and probably by higher plasma renin activity. The identification of these patients as a separate entity is desirable since it is possible that the evolution of the hypertensive disease and the response to therapy differ in this group of patients. The study of these patients could lead to a better understanding of the mechanisms underlying the pathogenesis of cardiovascular complications and to the development of more rational and efficient therapeutic approaches.