What is the preferred medication between diltiazem (Diltiazem) and metoprolol (Metoprolol) for atrial fibrillation with rapid ventricular response (AFib RVR)?

Diltiazem vs Metoprolol for Atrial Fibrillation with Rapid Ventricular Response

For patients with atrial fibrillation with rapid ventricular response (AFib RVR), metoprolol is the preferred medication for patients with heart failure or reduced ejection fraction (LVEF <40%), while diltiazem is preferred for patients with preserved ejection fraction (LVEF ≥40%) due to better and faster rate control. 1, 2

Decision Algorithm Based on Patient Characteristics

For Patients with LVEF <40% or Heart Failure:

• First choice: Metoprolol (start with smallest effective dose)
  • Initial IV dose: 2.5-5.0 mg IV bolus (up to 3 doses)
  • Maintenance: 25-100 mg BID orally
• Consider adding digoxin if inadequate control
• For hemodynamic instability or severely reduced LVEF, amiodarone is an option

For Patients with LVEF ≥40% (Normal Heart Function):

• First choice: Diltiazem
  • Initial IV dose: 15-25 mg IV bolus
  • Maintenance: 60-120 mg TID or 120-360 mg daily (modified release)
• Alternative: Metoprolol with similar dosing as above
• Add digoxin if inadequate control

Evidence Supporting These Recommendations

Efficacy Considerations

• Diltiazem achieves rate control faster than metoprolol in patients with preserved ejection fraction 3, 4
• In one study, rate control was achieved in 56% of the diltiazem group versus 36% of the metoprolol group (p = 0.04) 4
• However, in ICU patients, metoprolol had a lower failure rate than amiodarone and was superior to diltiazem in achieving rate control at 4 hours 5

Safety Considerations

• Recent meta-analysis (2024) showed metoprolol was associated with 26% lower risk of adverse events compared to diltiazem (10% vs 19%, RR 0.74) 6
• Both medications cause similar systolic blood pressure reduction (18 ± 22 mmHg for diltiazem vs 14 ± 15 mmHg for metoprolol) 4
• Clinically relevant hypotension rates are similar between groups (14% vs 16%) 4

Contraindications and Cautions

• Diltiazem and other non-dihydropyridine calcium channel blockers should be avoided in patients with heart failure due to systolic dysfunction or reduced LVEF due to negative inotropic effects 1
• Beta-blockers should be initiated cautiously in patients with AFib and heart failure who have reduced ejection fraction 1
• For patients with bronchospasm or COPD, diltiazem is preferred over beta-blockers 2

Target Heart Rate and Monitoring

• Initial resting heart rate target should be <110 bpm 1
• Long-term target: 60-100 beats per minute at rest and 90-115 beats per minute during moderate exercise 2
• Monitor heart rate response, blood pressure, symptoms of heart failure, renal function, and electrolytes within one week of initiating therapy 2

Important Clinical Pearls

• In patients with WPW syndrome, both digoxin and calcium channel blockers are contraindicated as they may facilitate anterograde conduction along the accessory pathway during AF, potentially resulting in acceleration of ventricular rate or ventricular fibrillation 1
• For patients with inadequate rate control on monotherapy, combination therapy with digoxin plus either beta-blocker or calcium channel blocker is recommended 2
• Amiodarone should be considered only when other measures are unsuccessful or contraindicated 1, 2

By following this algorithm, clinicians can optimize rate control in AFib RVR while minimizing adverse effects based on patient-specific characteristics, particularly left ventricular function.