Feeney ME, et al. - The authors assessed the difference in response to ventricular rate control with intravenous (IV) metoprolol compared to IV diltiazem in patients taking chronic beta-blocker therapy who present to the emergency department (ED) in atrial fibrillation (AF) with rapid ventricular rate (RVR). In patients in AF with RVR on chronic beta-blocker therapy, the use of IV diltiazem was correlated with a higher rate of successful response to rate control compared to IV metoprolol. However, the difference between groups was not statistically significant.