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Effects of sotalol on action potentials of canine ventricular muscle fibers and purkinje fibers in postmyocardial infarction period

Gao Tianli, Johannes Brachmann, Jochen Senges

Section of Physiology, Department of Biology, Peking Universiy. Beijing, China；Department of Cardiology, University of Heidelberg. West Germany

Abstract

Mongrel dogs were anesthetized with sodium pentobarbital. A leftside thoracotomy was performed and the left anterior descending coronary artery was ligated in two stages. After 3-5 days, the dog was reanesthetized, the chest was opened to excise the heart. A preparation consisting of roughly equal portion of normal and infarcted areas was removed. The effects of sotalol (5×10~(-5) to 2×10~(-4)M) on normal (NZ) and abnormal (IZ) myocardial tissues were analyzed. Intracellular action potentials (AP) were recorded from ventricular muscle fibers (VM) and Purkinje fibers (PF) in 12 isolated epicardial (EPI) and endocardial (ENDO) preparations respectively. Sotalol has no significant effect on RP, APA, V_(max) and conductive velocity (CV) of PF in the NZ and IZ, however, only the CV of VM in both zones were slightly lengthened. APDas and ERP of PF and VM could be prolonged markedly by sotalol Increase in APD, after sotalol was significantly greater in NZ than IZ fibers, whereas ERP was more prolonged in IZ than in NZ fibers. This means post-repolarization refractoriness selectively increased in infarcted myocardium. In another series of experiments we have found that beta-receptor blockade metoprolol could not significantly increase the APDaS and ERP of both infarcted and non-infarcted myocardium tissues, suggesting that beta-blockade sotalol also has the effect of class III antiarrhythmic drugs-prolongation of myocardium repolarization and refractoriness.

Key words: Sotalol;Myocardial infarction;Purkinje fiber;Ventricular muscle fiber;Action potential

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Citing This Article：

Gao Tianli, Johannes Brachmann, Jochen Senges. Effects of sotalol on action potentials of canine ventricular muscle fibers and purkinje fibers in postmyocardial infarction period . Acta Physiol Sin 1986; 38 (3): (in Chinese with English abstract).