Intravenous ibutilide achieved higher conversion rates than procainamide and placebo in atrial flutter (64% vs 0% and 0%) and atrial fibrillation (32% vs 5% and 0%).
RCT (n=136)
Double-blind and open-label
randomized
Does intravenous ibutilide improve conversion rates and alter electrophysiological characteristics compared to procainamide or placebo in patients with atrial flutter and fibrillation?
Intravenous ibutilide is more effective than procainamide for converting atrial flutter and fibrillation, an effect correlated with a relatively greater prolongation of atrial monophasic action potential duration than atrial cycle length.
Absolute Event Rate: 64% vs 0%
BACKGROUND: The selective class III antiarrhythmic agent ibutilide prolongs action potential duration and terminates atrial flutter (AFL) and fibrillation (AF), but the mechanism of its antiarrhythmic efficacy in humans has not been fully characterized. This study compared the antiarrhythmic effects of ibutilide with the class IA agent procainamide in humans during AFL and AF. Antiarrhythmic drug actions and electrophysiological characteristics of AFL and AF that enhanced pharmacological termination were investigated. METHODS AND RESULTS: Right atrial monophasic action potentials were recorded during 148 episodes of AFL (n=89) or AF (n=59) in 136 patients treated with intravenous ibutilide (n=73) or placebo (n=22) as participants in randomized, double-blinded comparative studies or intravenous procainamide (n=53) in a concurrent open-label study. The conversion rates in AFL with ibutilide, procainamide, and placebo were 64% (29 of 45 patients), 0% (0 of 33), and 0% (0 of 11), respectively, whereas in AF the rates were 32% (9 of 28), 5% (1 of 20), and 0% (0 of 11), respectively. In AFL, ibutilide increased atrial monophasic action potential duration (MAPD) more (30% versus 18%, P or = 160 ms (64% versus 0%, P or = 125 ms (57% versus 0%, P=.002) at baseline. CONCLUSIONS: Enhanced conversion efficacy of ibutilide compared with procainamide in AFL is correlated with a relatively greater prolongation of atrial MAPD than atrial CL, and termination of AFL by ibutilide is characterized by oscillations in atrial CL and MAPD. Conversion of AF by ibutilide is enhanced by a longer baseline mean atrial CL or MAPD.
Stambler et al. (Tue,) conducted a rct in Atrial flutter and atrial fibrillation (n=136). Intravenous ibutilide vs. Intravenous procainamide or placebo was evaluated on Conversion rates in atrial flutter. Intravenous ibutilide achieved higher conversion rates than procainamide and placebo in atrial flutter (64% vs 0% and 0%) and atrial fibrillation (32% vs 5% and 0%).
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