Contributor: Aaron Lessen, MD Educational Pearls: Atrial fibrillation is an irregular heart rhythm that sometimes requires rate control in setting of rapid ventricular response (RVR) Calcium channel blocker and beta blockers are the most frequently used medications to block the AV node and slow down the heart rate in atrial fibrillation with RVR If a patient is on one of these agents at home, the IV form should be used first Recent systematic review and meta-analysis found 3 trials addressing which medication to use to control heart rate in atrial fibrillation with RVR with a total of 150 patients Found diltiazem, a CCB, was 4x more likely to reduce heart rate than metoprolol 50% of patients had a normal heart rate at 21 minutes with diltiazem versus 22% in those who received metoprolol Both agents had a similar decrease in blood pressure after administration References Jafri SH, Xu J, Warsi I, Cerecedo-Lopez CD. Diltiazem versus metoprolol for the management of atrial fibrillation: A systematic review and meta-analysis. Am J Emerg Med. 2021 Oct;48:323-327. doi: 10.1016/j.ajem.2021.06.053. Epub 2021 Jun 30. PMID: 34274577. Summarized by John Spartz, MS4 | Edited by Erik Verzemnieks, MD   The Emergency Medical Minute is excited to announce that we are now offering AMA PRA Category 1 credits™ via online course modules. To access these and for more information, visit our website at https://emergencymedicalminute.org/cme-courses/ and create an account.  Donate to EMM today!