Effects of metoprolol and ramipril on action potentials after myocardial infarction in rats

The effects of chronic treatment with the beta-adrenoceptor antagonist meto prolol, the angiotensin converting enzyme inhibitor ramipril, their combina tion, or placebo on action potential configuration 6 weeks after myocardial infarction in rats were studied. Action potentials were measured in isolat ed left ventricular posterior papillary muscles and compared with action po tentials from a sham operated group without infarction. After infarction, t he action potential amplitude was reduced and this phenomenon was partially reversed by metoprolol- and ramipril-treatment. Prolonged repolarisation a fter infarction compared to sham operated animals was additionally delayed after metoprolol treatment. Thus, metoprolol extends the refractory period, which may counteract tachyarrhythmia. (C) 2000 Elsevier Science B.V. All r ights reserved.