The role of the autonomic nervous system in hypertension.

The role of the autonomic nervous system in the genesis and maintenance of hypertension is becoming clearer with time. Early research suggested that increased vascular resistance in hypertension was not dependent on excess autonomic tone and thus it was presumed that the autonomic nervous system had little to do with hypertension. More recent studies have demonstrated that the initial hemodynamic abnormality in hyperkinetic borderline hypertension is "normal" vascular resistance, with an elevated cardiac optput and heart rate, associated with markers of increased sympathetic and decreased parasympathetic tone of central origin. Over time there is a transition to the high peripheral resistance and normal cardiac output hemodynamic state characteristic of established hypertension, which is due to the development of adaptive structural changes in the peripheral resistance vessels and heart. The autonomic abnormality in hypertension and subsequent vascular and cardiac changes may explain some of association between hypertension and risk factors for coronary heart disease. The autonomic imbalance found in hypertension may not be a chance occurrence and we postulate that it is due to the inheritance of the genes responsible for a more pronounced defense reaction, which in earlier times may have conferred a survival advantage but now permit the negative impact of this trait to become evident.