Effects of new antiarrhythmic agent SS-68 on excitation conduction, electrical activity in Purkinje fibers and pulmonary veins: Assessment of safety and side effects risk

The compound SS-68 has been selected among numerous new derivatives of indole and demonstrated antiarrhythmic effects in animal models. The present study concerns several aspects of SS-68 safety and efficacy as a potential antiarrhythmic drug. The first estimation of atrioventricular conduction in mammalian heart under SS-68 has been carried out; effects of SS-68 in Purkinje fibers and myocardium of pulmonary veins have been investigated. The drug weakly affects cardiac atrioventricular conduction: only high concentrations of SS-68 (≥10 μmol/L) significantly decrease this parameter. Also, the drug weakly affects Purkinje fibers automaticity, but effectively alters action potential waveform in Purkinje fibers in a concentration-dependent manner. SS-68 (0.1–100 μmol/L) failed to induce any early or delayed afterdepolarizations in Purkinje fibers both in basal conditions and under provocation of proarrhythmic activity by norepinephrine (NE). Moreover, 10 μmol/L SS-68 suppressed NE-induced extra-beats and rapid firing in Purkinje fibers. In pulmonary veins only high concentrations of SS-68 significantly increased action potential duration, while lower concentrations (0.1–1 μmol/L) were ineffective. Also, 0.1–100 μmol/L SS-68 was unable to elicit arrhythmogenic alternations of action potential waveform in pulmonary veins. In conclusion, SS-68 has no proarrhythmic effects, such as afterdepolarizations or abnormal automaticity in used experimental models