Q: Ibutilide, despite its effective role in management of atrial fibrillation, remained less popular, due to fear of causing polymorphic ventricular tachycardia. What adjuvant treatment may decrease the chances of this side effect?

Answer:  Concurrent administration of high dose IV magnesium

Concurrent administration of high dose ( 4-5 grams) IV magnesium enhances the ability of ibutilide to successfully convert atrial fibrillation (or flutter), and attenuate the QT interval prolongation associated with ibutilide, and so lowers the rate of polymorphic ventricular tachycardia. 

References:

Tercius AJ, Kluger J, Coleman CI, White CM. Intravenous magnesium sulfate enhances the ability of intravenous ibutilide to successfully convert atrial fibrillation or flutter. Pacing Clin Electrophysiol 2007; 30:1331.

Patsilinakos S, Christou A, Kafkas N, et al. Effect of high doses of magnesium on converting ibutilide to a safe and more effective agent. Am J Cardiol 2010; 106:673.