Copyright © 1990 by the European Society of Cardiology.
© 1990 The European Society of Cardiology
Cardiac adrenoceptors in the failing heart: effect of intervention
Cardiology Division, Stanford University Medical Center Stanford, California U.S.A
Address for correspondence: Professor M. B. Fowler, Cardiology Division-CVRB 295, Stanford University Medical Centre, Stanford, California 95405, U.S.A.
The sympathetic nervous system is chronically activated in heart failure. This results in a reduction in numbers and sensitivity of β-receptors, making the heart less responsive to the actions of catecholamines. This is specific to β-receptors, the adenycyclase system being largely unaffected.
Sympathomimetic agents are still used in patients with heart failure to augment cardiac contractility, but tachyphylaxis limits their long-term usefulness, and they may actually cause further myocardial damage. On the other hand, β-blockade can improve sensitivity to catecholamines and cardiac action in some patients with severe left ventricular dysfunction, although this treatment can be hazardous and cannot yet be routinely recommended.
Partial β-agonists are theoretically useful since they can provide bareline sympathetic drive while protecting the heart against excessive sympathetic stimulation and down-regulation of β-receptors. Xamoterol, a partial agonist with half the sympathetic activity of isoprenaline, has been shown to be superior to placebo and to digoxin in patients with mild to moderate heart failure.
Key Words: Congestive heart failure • cardiac adrenoceptors • β-blockade • partial β-agonist • xamoterol