Comparison of class Ia/Ib versus class III antiarrhythmic drugs for the suppression of inducible sustained ventricular tachycardia associated with coronary artery disease.

Previous studies suggest that class Ia drugs are ineffective in suppression of sustained ventricular tachycardia by programmed stimulation. More favorable results have been described with combinations of Ia and Ib drugs and also with class III antiarrhythmic drugs, but there have been no direct comparisons between these 2 regimens. The present study was undertaken to compare the electrophysiologic efficacy and predictors of success of these 2 regimens in patients with ischemic heart disease and inducible sustained monomorphic ventricular tachycardia. The population consisted of 136 patients with documented coronary artery disease. All had sustained monomorphic ventricular tachycardia inducible during baseline electrophysiologic study and following intravenous procainamide. Follow-up studies were performed with a combination of oral class Ia and Ib or class III antiarrhythmic drugs. A positive response was the inability to induce a sustained ventricular arrhythmia with up to 3 extrastimuli at 2 right ventricular pacing sites. Response rates were 13% for Ia/Ib combination and 19% for class III agents (p = 0.40). Congestive heart failure differentially affected response rates. Only 8% of those responding to Ia/Ib therapy had heart failure compared with 59% of responders to class III (p <0.01). Multivariate analysis identified heart failure (RR 12.2, p = 0.03) as the only parameter with independent predictive value of response to Ia/Ib therapy. These results indicate that congestive heart failure is a potent predictor of a negative response to a combination of class Ia and Ib antiarrhythmic drugs. In this population, class III drugs or nonpharmacologic therapy should be considered as initial treatment.