Pathophysiology of the beta-adrenoceptor system in chronic heart failure: consequences for treatment with agonists, partial agonists or antagonists?
The human heart contains both beta 1-adrenoceptors and a considerable number of beta 2-adrenoceptors, both of which bring about positive inotropic and chronotropic effects of beta-adrenoceptor agonists in vitro and in vivo. In chronic heart failure, the decrease in beta-adrenoceptor function is related to the severity of the disease. However, both cardiac beta 1- and beta 2-adrenoceptors seem to be differentially affected depending on the type of heart failure and its aetiology. beta 1-adrenoceptor function decreases in all forms of chronic heart failure. beta 2-adrenoceptor function, on the other hand, decreases in mitral valve disease, tetralogy of Fallot and end-stage ischaemic cardiomyopathy, and seems to be unaltered (or only mildly uncoupled) in end-stage dilated cardiomyopathy, and possibly in aortic valve disease. Since the human heart has few spare beta-adrenoceptors and these decline with increasing degree of heart failure, beta-adrenoceptor agonists (but only non-selective full agonists) may be of therapeutic use only if the heart needs acute inotropic support; in long-term treatment they may be not effective, since tolerance develops. On the other hand, for long-term treatment selective beta 1-adrenoceptor antagonists may be beneficial since they protect the heart from the deleterious effects of chronic exposure to high (cardiac derived) noradrenaline and simultaneously may restore the previously reduced beta-adrenoceptor function.
Abtlg. Nieren- und Hochdruckkrankheiten, Universitätsklinikum, Essen, Germany.
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D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use; D002303:Cardiac Output, Low / Q000188:drug therapy / Q000503:physiopathology*; D006801:Humans; D011943:Receptors, Adrenergic, beta / Q000502:physiology*
D000319:Adrenergic beta-Antagonists; D011943:Receptors, Adrenergic, beta