[Is sympathetic hyperactivity a coronary risk factor?]

Clinical and experimental data have suggested a role of enhanced sympathetic nervous activity in the pathogenesis and evolution of coronary heart disease. A significant relationship was observed between the circadian pattern of plasma catecholamine levels and the onset of coronary events, which occur most frequently in the early morning, concomitance with sympathetic activation. An enhanced sympathetic tone is frequently observed in both the acute phase of myocardial infarction and in the postinfarction period, potentiating myocardial damage and increasing the risk of arrhythmias. An indirect demonstration of the importance of sympathetic activation arises from the results of several trials on the effects of beta-blocker treatment during and after myocardial infarction, showing a significant reduction in total mortality, sudden deaths and reinfarction. There is accumulating evidence that repeated activation of sympathetic nervous system may contribute to atheroma development and progression. Enhanced sympathetic activity seems to be involved in the pathogenesis and maintenance of essential hypertension as well as in its natural history, contributing to the development of left ventricular hypertrophy and vascular hypertrophy. The problems in measuring and defining the various levels of autonomic activity in human beings and the complexity of the relationship between nervous and non nervous factors in cardiovascular diseases make difficult to establish whether sympathetic hyperactivity represents an independent cardiovascular risk factor.