[Effect of selective and non-selective adrenergic beta receptor blockaders on selected electrophysiologic properties...

Beta-2 adrenergic receptors were found in a human heart and their role in regulation of inotropic properties during last year was proved. The aim of our study was comparison of effects of selective (metoprolol) and nonselective (propranolol) beta-receptors blockade on cardiac electrophysiological properties. The study was carried out in 20 patients in the majority without organic heart injury and clinical symptoms of the sinus node dysfunction as well as atroioventricular conduction disorders. Method of the transoesophageal left atrial stimulation was utilized. Examinations were performed after drugs administrations in the same persons, during following days. Propranolol and metoprolol were intravenously administrated in a dose of 0.2 mg/kg b.w. Both drugs statistically significant lengthened sinus rhythm cycle time, sinus node recovery time, sinus node and a-v node effective refraction and lowered Wenckebach's point. They did not significantly effect on sinoatrial conduction and the atrial effective refraction. There were no significant differences between examined beta-blockers. Obtained results allowed us to conclude that: 1) eletrophysiologic properties of propranolol and metoprolol are similar, 2) it seems that in physiological conditions the effects of the adrenergic nervous system on electrophysiologic properties of sinus node, atrio-ventricular node and atrium is mainly realized by beta-1 adrenergic receptors.