Treatment of Atrial Fibrillation and Paroxysmal Supraventricular Tachycardia With Bidisomide

BACKGROUND: Atrial fibrillation and paroxysmal supraventricular tachycardia are common disorders of the heart rhythm for which antiarrhythmic drug therapy is commonly prescribed. The Atrial Fibrillation Investigation with Bidisomide (AFIB) study was a randomized, placebo-controlled clinical trial designed to accomplish three goals in a single protocol: (1) to determine the efficacy of the antiarrhythmic drug bidisomide in the treatment of these two arrhythmias; (2) to establish the appropriate dose range for bidisomide; and (3) to detect an adverse mortality effect of bidisomide if one were present in patients with atrial fibrillation. METHODS AND RESULTS: In this clinical trial, 1227 patients with atrial fibrillation and 187 with paroxysmal supraventricular tachycardia were randomly assigned to bidisomide (200, 400, or 600 mg BID) or placebo; patient groups with each arrhythmia were analyzed separately. Symptomatic recurrences of atrial fibrillation and paroxysmal supraventricular tachycardia were documented with the use of transtelephonic ECG monitoring. The time to the first symptomatic arrhythmia recurrence was measured in each patient and compared among treatment groups. Among the atrial fibrillation patients, there was no significant difference in the time to first symptomatic recurrence between the placebo group and any of the three bidisomide treatment groups; the hazard ratios (placebo:treatment) were 1.19, 1.03, and 1.14 for bidisomide 200, 400, and 600 mg BID, respectively. Among paroxysmal supraventricular tachycardia patients, there was a similar lack of a significant treatment effect; the hazard ratios were 1.30, 1.93, and 1.59 for bidisomide 200, 400, and 600 mg BID, respectively. In the primary safety analysis of mortality, 3 of 493 patients taking placebo died, compared with 9 of 488 patients taking one of the two higher doses of bidisomide (P>.10). CONCLUSIONS: Bidisomide in the doses tested did not have a clinically important antiarrhythmic effect. The AFIB study provided a novel clinical trial design to test antiarrhythmic drugs for both safety and efficacy.