Intravenous (IV) procainamide and ibutilide are two commonly used medications for the cardioversion of emergency department (ED) patients with recent onset (<48 hours) atrial fibrillation (AF) and atrial flutter (AFL;either = AF/AFL) across North America. It is unclear which medication is preferable. No trials have compared these agents for this indication and North American societyguidelines offer contradictory recommendations: procainamide is the drug of choice in the Canadian guideline, where ibutilide is not recommended; the converse is true in U.S. guidelines. Issues of effectiveness, safety, and ease of use may contribute to drug selection. Ibutilide carries a black-box warning for the risk for torsadede pointes (polymorphic ventricular tachycardia [VT]) and requires at least 4h of monitoring, making it riskier and more cumbersome to administer than procainamide.