[Effect of the novel III class anti-arrhythmia preparation (AL-275) in experimental myocardium and sympathetic stimulation].

AL-275, a new antiarrhythmic agent, exhibits the properties typical of the class III antiarrhythmogen: (i) prolongs the ventricular repolarization; (ii) inhibits the sinus node automatism; (iii) increases the effective refractory periods in atrium and ventricles; and (iv) does not modify AV and intraventricular conduction. AL-275 produces a pronounced antiarrhythmic and antifibrillatory action. The effect of AL-275 is independent of the heart rate, which is an advantage over the other class III agents. Both character and intensity of the electrophysiological and antiarrhythmic activity of AL-275 were fully retained upon the preliminary infusion of isoproterenol. Independence of the drug action of both the heart rate and the isoproterenol-induced changes in refractoriness are related to the ability of AL-275 to block a slow component (IKs) of the potassium current.