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Electrophysiological effects of sotalol on sinus node atrium atrioventricular node and his bundle cells in rabbit heart


Acta Physiologica Sinica 37(5): 425-436
Electrophysiological effects of sotalol on sinus node atrium atrioventricular node and his bundle cells in rabbit heart
By means of microelectrode techniques the electrophysiological effects of beta blocking agents, sotalol and metoprolol, were studied on isolated rabbit right atrium-atrioseptum preparations. Sotalol (1.6 .times. 10-6 to 1.6 .times. 10-4 M) and metoprolol (1.2 .times. 10-7 to 1.2 .times. 10-4 M) had no effect on SAN, AVN, atrial and His-bundle cell APA and .ovrhdot.Vmax. Sotalol caused a dose-dependent decrease in sinus rate and AVN rate as well as in corrected SAN and AVN recovery time after rapid atrial stimulation, while metoprolol had no effect on these parameters. The most prominent effect of sotalol was the prolongation of action potential duration (APD) and effective refractory period (ERP) of the SAN, AVN, atrial and His-bundle cells. In contrast to sotalol, metoprolol had no effect on APD and ERP of all the above cells. In 8 preparations, the rapid automatic discharge of AP could be induced by adequate premature stimulus, thus providing a basis of reentrant supraventricular tachycardia. Administration of sotalol caused cessation of the rapid discharge in 7 cases, while only one case of such arrhythmia was suppressed by metoprolol. Therefore, the antiarrhythmic action of sotalol is related mainly to the prolongation of repolarization and refractoriness in SAN, AVN, and atrium with consequent interruption of reentrant circular conduction. This is just the characteristic mechanism of action associated with Class III antiarrhythmic agents.


Accession: 005349598



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