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The goal of this study was to test the hypothesis that class I drugs modify the electrophysiological substrate of atrial fibrillation. The effects of a single intravenous dose (1.4 +/- 0.3 mg.kg-1) of the new class I drug, cibenzoline, were studied in 20 patients with spontaneous (n = 11) or induced (n = 9) atrial fibrillation, during an electrophysiological study. In one additional patient with chronic atrial fibrillation, the effects of a single intravenous dose of 2 mg.kg-1 of cibenzoline were studied intra-operatively before undergoing a 'corridor' operation. High resolution epicardial mapping (248 channels) was used to reconstruct the atrial activation patterns before and after administration of the drug. In 18 out of 20 patients administration of cibenzoline resulted in conversion of atrial fibrillation into regular monomorphic atrial tachycardia. In these 18 patients, the mean atrial cycle length was prolonged from 147 +/- 34 ms during atrial fibrillation to 302 +/- 34 ms after cibenzoline (P < 0.001). In eight out of the 18 patients, spontaneous (n = 3) or pacing induced (n = 5) conversion into sinus rhythm was observed after administration of the drug. In the patient undergoing the 'corridor' operation, epicardial mapping of both atria showed that the multiple wavelets present during atrial fibrillation fused into a single broad wavefront circulating counterclockwise around the caval veins after cibenzoline. In conclusion, cibenzoline transforms random re-entry into ordered re-entry in the atria. This effect seems related to the depression of conduction produced by the drug.
Brugada et al. (Tue,) studied this question.