Clinical consequences of the autonomic imbalance in hypertension and congestive heart failure.

The reduction of coronary mortality is not as large as one would expect from the observed blood pressure lowering in trials of antihypertensive medications. This is not surprising; hypertension is a complex disease where the high blood pressure is only one of numerous coronary risk factors. Sympathetic overactivity in hypertension, independent of the blood pressure, may be conducive to premature atherosclerosis by inducing insulin resistance and dyslipidemia. Through its trophic effect on blood vessels, sympathetic overactivity potentiates vasoconstriction. This, in turn, accelerates hypertension and the metabolic syndrome. The hypertrophy of small coronary arterioles decreases the coronary reserve and enhances coronary spasms. Tachycardia, which is due to increased sympathetic tone and a decreased parasympathetic tone, favors arrhythmias and sudden death in congestive heart failure and hypertension. Increased hematocrit is frequently found in male patients with hypertension, and high hematocrit is a predictor of coronary heart disease/thrombosis. The increase of hematocrit is in part due to an alpha adrenergic postcapillary venoconstriction. Enhanced sympathetic drive, insulin resistance and dyslipidemia have been demonstrated also in congestive heart failure, but the clinical importance of these findings is not fully understood.