Mechanisms of the beneficial effects of beta-adrenoceptor antagonists in congestive heart failure.

Many clinical studies have documented favourable effects (reduced morbidity and mortality) of beta-adrenoceptor (β-AR) antagonists, such as carvedilol, metoprolol, propranolol, atenolol and bisoprolol, in congestive heart failure. These agents attenuate the effects of sympathetic activation during the development of heart failure, prevent ventricular remodelling and improve cardiac function. Because β-AR blockers are known to exert negative inotropic action, the mechanisms responsible for their beneficial effects in heart failure have been a subject of debate. While attenuation of changes in β-AR cyclic AMP-mediated signal transduction in heart failure is considered to be responsible for the beneficial effects of β-AR antagonists, other mechanisms such as the effects of these agents on subcellular remodelling, oxidative stress, apoptosis and defect in calcium handling, are equally important in preventing cardiac alterations in the failing heart. Moreover, β-AR antagonists are not a homogeneous group of drugs because they differ in their pharmacokinetics and pharmacodynamics, in addition to the selective and nonselective nature of their actions on β-AR. Various β-AR blocking agents have been shown to possess different ancillary properties and produce effects that are independent of β-AR. In fact, different β-AR antagonists have been observed to lower the elevated levels of plasma catecholamines in heart failure. Thus, the beneficial effects of β-AR antagonists are not only elicited through their interaction with mediated β-AR signal transduction sites in the myocardium, but other mechanisms may also contribute to their favourable actions in heart failure.