What medication is given in the ER for atrial fibrillation (AFib) with rapid ventricular response (RVR)?

Emergency Department Management of Atrial Fibrillation with Rapid Ventricular Response

For hemodynamically stable patients with AFib and RVR in the ER, intravenous diltiazem (0.25 mg/kg over 2 minutes) or metoprolol (2.5-5 mg IV bolus) are first-line agents, with diltiazem demonstrating superior efficacy for rapid rate control. 1

Immediate Assessment: Hemodynamic Stability

Unstable patients (decompensated heart failure, ongoing myocardial ischemia, or hypotension) require immediate electrical cardioversion, not pharmacologic rate control. 1

For hemodynamically stable patients, proceed with pharmacologic rate control using the algorithm below.

First-Line Pharmacologic Options

Beta-Blockers (Intravenous)

• Metoprolol tartrate: 2.5-5 mg IV bolus over 2 minutes, may repeat up to 3 doses (maximum 15 mg total) 1, 2
• Esmolol: 500 mcg/kg IV bolus over 1 minute, followed by 50-300 mcg/kg/min infusion 1
• Propranolol: 1 mg IV over 1 minute, may repeat every 2 minutes up to 3 doses 1

Beta-blockers are particularly effective in high adrenergic states (postoperative AFib, thyrotoxicosis) 1

Calcium Channel Blockers (Intravenous)

• Diltiazem: 0.25 mg/kg IV over 2 minutes; may repeat with 0.35 mg/kg after 15 minutes if needed, then 5-15 mg/hour continuous infusion 1, 2
• Verapamil: 5-10 mg IV over ≥2 minutes, may repeat twice, then 5 mg/hour infusion (maximum 20 mg/hour) 1

Diltiazem demonstrates 1.8 times greater likelihood of achieving rapid rate control compared to metoprolol (95% CI 1.2-2.6), making it the preferred agent when rapid control is essential. 3

Comparative Efficacy

Low-dose diltiazem (≤0.2 mg/kg) achieves similar rate control (70.5% success) compared to standard dosing (77.1%) but with significantly lower hypotension risk (18% vs 34.9%, adjusted OR 0.39) 4. Consider starting with lower diltiazem doses to minimize hypotension while maintaining efficacy.

Critical Contraindications

Absolute Contraindications to Rate-Control Agents

Never use digoxin, calcium channel blockers, or amiodarone in patients with pre-excitation syndromes (Wolff-Parkinson-White) as they may paradoxically accelerate ventricular response and precipitate ventricular fibrillation. 1, 2

• Calcium channel blockers: Contraindicated in decompensated heart failure with reduced ejection fraction (HFrEF) 1, 2
• Beta-blockers: Avoid in severe asthma, decompensated heart failure, advanced heart block 1

Pre-Excitation Management

For AFib with RVR in the setting of accessory pathways, intravenous procainamide is the drug of choice 5. Electrical cardioversion remains appropriate for unstable patients.

Alternative Agents

Digoxin

• Loading: 0.25-0.5 mg IV over several minutes, may repeat 0.25 mg every 6 hours (maximum 1.5 mg/24 hours) 1
• Onset: 60 minutes or longer 1

Digoxin as monotherapy is generally ineffective for acute rate control in AFib with RVR due to delayed onset 5. Consider only as adjunctive therapy or in sedentary patients with heart failure 6, 2.

Amiodarone

• Dosing: 150-300 mg IV over 1 hour, then 10-50 mg/hour infusion 1
• Class IIa recommendation (Level of Evidence C) 1

Amiodarone has delayed onset (days) and should be reserved for patients with contraindications to beta-blockers and calcium channel blockers 1.

Monitoring and Target Heart Rate

• Lenient control: Resting heart rate <110 bpm 6, 2
• Strict control: Resting heart rate <80 bpm 6, 2

Monitor blood pressure, heart rate, and cardiac rhythm continuously during IV administration. 1 Assess for excessive bradycardia or hypotension between doses when using bolus dosing 6.

Common Pitfalls to Avoid

1. Using rate-control agents in pre-excitation: This can cause life-threatening ventricular arrhythmias 1, 2
2. Calcium channel blockers in HFrEF: May precipitate cardiogenic shock 1
3. Relying on digoxin monotherapy: Ineffective for acute rate control 5
4. Ignoring anticoagulation: All AFib patients require stroke risk assessment and appropriate anticoagulation unless contraindicated 2

Transition to Oral Therapy

Once acute rate control is achieved:

• Metoprolol tartrate: 25-100 mg twice daily 1
• Metoprolol succinate: 50-400 mg once daily 1, 6
• Diltiazem extended-release: 120-360 mg once daily 1

Verify adequate rate control with 24-hour Holter monitoring or exercise testing after discharge to ensure control during activity, not just at rest. 2, 7