Metoprolol vs Diltiazem in rate control of Afib

Question:

  • Is metoprolol and diltiazem similar in their efficacy in Afib rate control?

Study design

  • Prospective, randomized, double-blind study to compare the effectiveness of intravenous metoprolol with that of diltiazem in achieving rate control in adult ED patients with rapid AFF.

Population

  • Adult patients > 18 yo presenting with ECG of Afib with HR > 120 and SBP > 90
  • Exclusion:
    SBP < 90 mm Hg, ventricular rate $ 220 bpm, QRS > 0.100 s, second- or third-degree atrioventricular (AV) block, temperature > 38.0C, acute ST elevation myocardial infarction, known history of New York Heart Association Class IV heart failure or active wheezing with a history of bronchial asthma or chronic obstructive pulmonary disease (COPD). In addition, patients were excluded if there was prehospital administration of diltiazem or any other AV nodal blockading agent, a history of cocaine or methamphetamine use in the 24 hours before arrival, a history of allergic reaction to diltiazem or metoprolol, a history of sick sinus or pre-excitation syndrome, a history of anemia with hemoglobin < 11.0 g/dL, pregnancy, or breastfeeding.

Intervention:

  • Patients were randomly assigned, in a 1:1 ratio, to receive diltiazem administered parenterally at a dose of 0.25 mg/kg (to a maximum dose of 30 mg) or metoprolol administered at a dose of 0.15 mg/kg (to a maximum dose of 10 mg).
  • The time at which the first dose was administered was denoted as time 0 (baseline). If the primary endpoint was not achieved at time 15 min, then a second escalation dose was administered. If the patient had been enrolled in the diltiazem group, the escalation dose was 0.35 mg/kg (to a maximum dose of 30 mg), and for patients enrolled in the metoprolol group, the escalation dose was 0.25 mg/kg (to a maximum dose of 10 mg).

Outcomes:

  • The primary efficacy outcome measure was HR < 100 bpm within 30 min of drug administration.
    – The study team, monitored each subject’s SBP and DBP and HR at time 0, 5, 10, 15, 20, 25, and 30 min.
  • The primary safety outcome measures were HR < 60 bpm and SBP < 90 mm Hg.

Results

  • By 30 min, 95.8% of the diltiazemgroup and 46.4% of the metoprolol group reached the target HR of <100 bpm (p < 0.0001).
  • The mean decrease in HR for the diltiazem group was more rapid and substantial than that of the metoprolol
    group.
    – The mean HR for the metoprolol group did not reach the target of <100 bpm at any time during the 30-min study period.
  • There was no difference between the groups with respect to hypotension (SBP < 90 mm Hg) and bradycardia (HR < 60 bpm).

Comments:

  1. The researchers estimated that 200 patients were needed to prove non-inferiority between metoprolol and diltiazem. But the final sample size was only 52 patients.
  2. More patients with a history of Afib in metoprolol (39%) vs diltiazem group (29%); also less patients with new onset of Afib in metoprolol (60.7%) vs diltiazem group (70.8%) In addition, there is also more patients with COPD history in metoprolol (11%) vs diltiazem group (4%). Metoprolol group perhaps represent patient population with more difficult to control Afib.
  3. In 15 minutes, ~30% of the metoprolol group patients reach primary endpoint, therefore escalation doses will be used in the other 70%. Although there is no significant difference between metoprolol and diltiazem group with respect to hypotension and bradycardia, keep in mind that this is small sample size.
    – 5 patients with metoprolol group vs 1 patient in diltiazem group have hypotension.

Conclusion:

  • Diltiazem seems to be better than metoprolol in the treatment of Afib with RVR.
  • However, this is a small sample size and metoprolol group perhaps represent population with a more difficult to treat Afib.

Reference:

DILTIAZEM VS. METOPROLOL IN THE MANAGEMENT OF ATRIAL FIBRILLATION OR FLUTTER WITH RAPID VENTRICULAR RATE IN THE EMERGENCY DEPARTMENT. Christian Fromm, MD, FAAEM, FACEP, Salvador J. Suau, MD, FACEP, Victor Cohen, PHARMD, Antonios Likourezos, MA, MPH, Samantha Jellinek-Cohen, PHARMD, Jonathan Rose, MD, FACEP, and John Marshall, MD, FACEP. The Journal of Emergency Medicine 2015:49(2);175–182

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