CATECHOLAMINES AND THEIR BLOCKADE IN CONGESTIVE-HEART-FAILURE

The hemodynamic effects of sympathetic nervous system stimulation and the benefits of catecholamine blockade in patients with congestive hea rt failure (CHF) are discussed. Prolonged stimulation of the sympathet ic nervous system promotes disease progression in patients with CHF. T he level of circulating norepinephrine is the factor most closely corr elated with prognosis. Long-term catecholamine stimulation of beta-rec eptors in the myocardium reduces the ability of catecholamines to impr ove cardiac contractility. CHF patients have higher vascular resistanc e (afterload) than healthy persons, increasing the strain on the heart . Also, beta(1)-adrenergic activity stimulates renin release, which is deleterious in CHF. Clinical trials suggest that long-term (greater t han one month), carefully dose-adjusted therapy with beta-blockers imp roves symptoms, ventricular ejection fraction, exercise time, and qual ity of life in patients with CHF, but it is unclear whether beta-block ers reduce mortality. Some patients cannot tolerate even the lowest st arting dosages of beta-blockers, and withdrawal of these agents may re sult in clinical and hemodynamic deterioration. Carvedilol, which has beta-blocking, alpha-blocking, and antioxidant properties, is associat ed with a reduction in hospitalizations and symptoms and improvements in ejection fraction; it also appears to reduce mortality, although co nfirmatory studies are needed. Initiation of carvedilol therapy can ca use symptomatic and hemodyamic worsening in the short term, and some p atients cannot tolerate it. Adrenergic blocking agents are important c omponents of therapy for CHF. Carvedilol may prove useful in reducing symptoms and improving survival in these patients.