AbstractThe electrophysiologic and antiarrhythmic effects of artilide were evaluated in dogs 24 h after myocardial infarction. Artilide (0.1 to 3.0 mg/kg or 0.2 to 7.0 μuM/kg iv) prevented programmed stimulation induced ventricular arrhythmias in 9 out of 9 dogs that had demonstrated inducibe ventricular arrhythmias prior to treatment. This antiarrhythmic action was associated with significant increases in ventricular refractoriness and monophasic action potential duration. Lower doses of artilide tended to reduce the incidence of spontaneous ventricular arrhythmias but these effects were not significant. These results are consistent with the concept that spontaneous and pacing induced ventricular arrhythmias result from different mechanisms, and that class III anti‐arrhythmic agents are more effective in suppressing induced ventricular tachycardia due to reentry than spontaneous arrhythmias which result from nonreentrant mechanisms. © 1993 wiley‐Liss