Study 1: This was a prospective double blind, randomized trial located in a single ED in Bursa, Turkey. Patients were eligible if they were 18 years or older with afib with ventricular rate greater than or equal to 120 bpm and systolic BP greater than or equal to 95mm Hg. Exclusion criteria were hx of allergic reaction to diltiazem or metoprolol, CHF (NYHA class IV), systolic BP <95mm Hg, sick sinus syndrome, 2nd or 3rd degree AV block, pre-excitation syndromes, ventricular rate > 220BPM, QRS>0.08s, unstable angina pectoris, acute MI, hyperthyroid, temperature >38 degrees Celsius, HBG <11g/dl, asthma, COPD, DM, PVD, pregnancy, history of use of diltiazem, verapamil, digoxin, B-blockers, theophylline or B mimetics within the last 5 days. The objective was to compare the effectiveness of diltiazem vs metoprolol in management of afib with RVR in the ED. The patients were randomly assigned to IV diltiazem 0.25 mg/kg (maximum 25 mg) or metoprolol 0.15 mg/kg (maximum 10 mg). The patient’s heart rate (with a rhythm strip at least 30 s long) and blood pressures were measured and recorded by a blinded observer at 2, 5, 10, 15, and 20 minutes to evaluate the effect of the treatment. Successful treatment was defined as achievement of a ventricular rate <100/min or a decrease in ventricular rate by 20% (<120/min at least) or conversion to sinus rhythm. Twenty patients were randomized to receive diltiazem and twenty were randomized to receive metoprolol. A significant decrease in the ventricular rate was observed in both treatment groups at 2 minutes (p <0.01), however diltiazem had a statistically significantly greater success rate at two minutes.  90% of patients in the diltiazem group achieved rate control and 80% of patients in the metoprolol group achieved rate control – this difference was not statistically significant (p>0.05). None of the patients had hypotension.  

Study 2: This was a prospective, double-blind, randomized trial that took place at a single adult emergency department. The objective of the study was to determine whether metoprolol or diltiazem was more effective at achieving rate control in adult patients with afib with RVR in the emergency department. A convenience sample of patients 18 or older presenting with afib with a ventricular rate greater than or equal to 120bpm and systolic blood pressure greater than or equal to 90mm Hg were eligible. Exclusion criteria included SBP <90, ventricular rate >220, QRS >0.100s, second or third degree AV block, temp >38 C, STEMI, hx of NYHA Class IV heart failure, active wheezing with a hx of bronchial asthma or COPD, prehospital administration of diltiazem or other AV nodal blocking agent, hx of cocaine or methamphetamine use in the previous 24 hours, hx of drug reaction to metoprolol or diltiazem, hx of sick sinus syndrome or pre-excitation syndrome, hbg <11, pregnancy or breastfeeding.  Patients were randomly assigned, in a 1:1 ratio, to receive diltiazem 0.25 mg/kg (to a maximum dose of 30 mg) or metoprolol 0.15 mg/kg (to a maximum dose of 10 mg). If the primary endpoint was not achieved at time 15 min, then a second escalation dose was administered of either diltiazem 0.35 mg/kg (to a maximum dose of 30 mg), or metoprolol 0.25 mg/kg (to a maximum dose of 10 mg). The primary efficacy outcome measure was HR < 100 bpm within 30 min of drug administration. The primary safety outcome measures were HR < 60 bpm and SBP < 90 mm Hg. Twenty four patients were randomized to diltiazem and 28 were randomized to metoprolol. In the first 5 min, 50.0% of the diltiazem group and 10.7% of the metoprolol group reached the target HR of <100 bpm (p< 0.005). By 30 min, 95.8% of the diltiazem group and 46.4% of the metoprolol group reached the target HR of <100 bpm (p< 0.0001). There was no difference between the groups in regards to hypotension or bradycardia.  

Conclusions: Diltiazem appears to work faster and may have better efficacy than metoprolol in obtaining rate control in patients in afib with RVR. However, both studies were very small and had a large number of exclusion criteria which makes these studies difficult to apply to the average patient coming into the ED with afib. There likely needs to be more studies with larger sample sizes and fewer exclusion criteria. After reading these studies, I will likely try to use diltiazem more, but it is reassuring that in regards to safety, both medications appear to be equally safe.  

References: 

1.       Demircan C, Cikriklar HI, Engindeniz Z, et al. Comparison of the effectiveness of intravenous diltiazem and metoprolol in the management of rapid ventricular rate in atrial fibrillation. Emergency Medicine Journal 2005;22:411-414. 

2. Fromm C, et al. Diltiazem vs. Metoprolol in the Management of Atrial Fibrillation or Flutter with Rapid Ventricular Rate in the Emergency Department, The Journal of Emergency Medicine, Volume 49, Issue 2,2015, Pages 175-182, ISSN 0736-4679.