A Systematic Review of Weight-Based Metoprolol for Acute Atrial Fibrillation with Rapid Ventricular Rate

Atrial fibrillation (AF) is the most common cardiac arrhythmia encountered in the emergency department (ED) and when patients present in acute AF with rapid ventricular rate (RVR), it can result in significant morbidity and mortality. Primary treatment modalities are aimed at rate control with the two most common agents being intravenous metoprolol and diltiazem. Some evidence suggests that diltiazem may be more effective at controlling rate in these patients; however, the dosing strategies, pharmacologic differences, and study designs may play a role in the observation of these differences. The purpose of this article is to review the evidence for using weight-based metoprolol in the treatment of AF with RVR. The vast majority of studies comparing metoprolol and diltiazem for the treatment of acute AF with RVR compare a flat dose of metoprolol to a weight-based dose of diltiazem. Following a comprehensive review, only two studies have compared a weight-based dosing strategy of intravenous (IV) metoprolol versus IV diltiazem for this disease state. Overall, the two studies only contained 94 patients and failed to meet power. Beyond differing dosing strategies, differences in pharmacokinetics between the two medications (like the onset of action and metabolism) could have played a role in the differences observed in the studies. Further studies are warranted to provide better guidance on which agent should be used in the treatment of acute AF with RVR.