Acute beta-adrenoceptor blockade improves efficacy of ibutilide in conversion of atrial fibrillation with a rapid ventricular rate.

Aims: Activation of beta-adrenoceptors attenuates prolongation of action potential duration induced by blockade of the delayed rectifier potassium current. We examined whether acute administration of beta-blocker could enhance ibutilide (IB) efficacy in conversion of atrial fibrillation (AF) with a rapid ventricular rate.

Methods And Results: Ninety patients (aged 63 +/- 13.