Pathophysiologic role of the renin-angiotensin-aldosterone and sympathetic nervous systems in heart failure

Abstract

Purpose. The pathophysiology of heart failure is reviewed, with particular focus on the role of abnormal neurohormonal activation of the sympathetic nervous system and the renin-angiotensin-aldosterone axis in the pathophysiology of this syndrome. Summary. Events preceding myocardial infarction and heart failure are driven in part by norepinephrine, angiotensin II, and aldosterone. The sympathetic nervous system likely evolved to mediate acute regulation of the cardiovascular system, not the sustained activation that is seen in heart failure. Overexpression of β1-receptors in animal models results in decreased left ventricular ejection fraction and ventricular remodeling. In patients with systolic dysfunction, β-blockade has improved left ventricular function and decreased the risk of sudden death. Chronic exposure to excess angiotensin II produces eccentric ventricular hypertrophy, vasoconstriction, and sodium retention. Angiotensin-converting enzyme (ACE) inhibition causes only a transient depression of aldosterone concentrations; the chronic benefit from ACE inhibition in patients with heart failure likely results from augmentation of bradykinin and not from the inhibition of angiotensin II production. Administration of eplerenone, a selective mineralocorticoid receptor antagonist, following induction of ischemic injury in animals, blocked the progressive ventricular dilatation and reduction in systolic function observed in control animals; clinical studies indicate that those findings can be translated to human cardiovascular disease. Overactivity of the mineralocorticoid receptor in cardiomyocytes could be important even in the absence of excessive levels of aldosterone. Clinical studies demonstrated that strategies of neurohormonal blockade using an ACE inhibitor, angiotensin II receptor antagonist, and β-blocker are ineffective in reducing circulating aldosterone in patients with heart failure caused by left ventricular systolic dysfunction. Conclusion. Aldosterone is a key deleterious hormone influencing all forms of cardiovascular disease, including hypertension, myocardial infarction, and heart failure. Treatment of many cardiovascular diseases should include specific antagonism of the adverse pathophysiologic consequences of aldosterone.