What is the preferred medication for conversion of atrial fibrillation (AFib) with rapid ventricular response (RVR), diltiazem or amiodarone?

Diltiazem is Superior to Amiodarone for Rate Control in Atrial Fibrillation with Rapid Ventricular Response

For patients with atrial fibrillation with rapid ventricular response (AFib with RVR), intravenous diltiazem is superior to amiodarone for achieving rapid ventricular rate control in hemodynamically stable patients. 1

First-Line Therapy Selection

Hemodynamically Stable Patients

• IV beta-blockers and nondihydropyridine calcium channel blockers such as diltiazem are the drugs of choice for acute rate control in most individuals with atrial fibrillation and rapid ventricular response. 2
• Diltiazem is FDA-approved specifically for temporary control of rapid ventricular rate in atrial fibrillation or atrial flutter. 3
• Diltiazem works by inhibiting calcium influx during membrane depolarization, slowing AV nodal conduction and prolonging AV nodal refractoriness. 3

Comparative Efficacy

• In a direct comparison study, intravenous diltiazem was significantly more effective than amiodarone for achieving ventricular rate control, with:
  • Shorter median time to rate control (3 hours vs. 7 hours, p=0.003)
  • Higher percentage of patients achieving rate control (90% vs. 74%)
  • Greater reduction in AF symptom frequency and severity
  • Shorter hospital stays (3.9 days vs. 4.7 days, p=0.038) 1

Dosing Considerations for Diltiazem

• Standard dosing: 0.25 mg/kg IV bolus over 2 minutes 3
• Low-dose strategy (≤0.2 mg/kg) may be equally effective with lower risk of hypotension 4
• Doses ≥0.13 mg/kg achieve heart rate control more quickly than lower doses 5
• Continuous infusion (5-15 mg/hour) may be needed after initial bolus 2

Special Populations and Considerations

Heart Failure Patients

• Traditional teaching suggests avoiding diltiazem in heart failure due to negative inotropic effects
• However, recent research suggests diltiazem may be as safe as metoprolol in heart failure patients with AFib with RVR, with more rapid heart rate reduction 6
• For patients with heart failure, guidelines still recommend:
  • Digoxin and amiodarone as preferred agents for rate control 2
  • Beta blockers as preferred agents due to favorable effects on morbidity and mortality 2

When to Use Amiodarone

• Amiodarone should be considered for rate control when:
  • Patient has systolic heart failure and beta blockers are contraindicated or ineffective 2
  • Other measures for rate control are unsuccessful or contraindicated 2
  • The patient is critically ill or has tenuous hemodynamic stability 2

Important Cautions

• Avoid both diltiazem and amiodarone in patients with pre-excited atrial fibrillation (e.g., WPW syndrome) as they may cause paradoxical increase in ventricular response 2
• Amiodarone has potential for significant toxicity including pulmonary fibrosis, hepatic injury, and proarrhythmia with long-term use 2
• Diltiazem should be used with caution in patients with depressed ejection fraction due to negative inotropic effects 2

Implementation in Clinical Practice

• For hemodynamically unstable patients with AFib with RVR, immediate electrical cardioversion is recommended regardless of medication choice 2
• For stable patients, follow a protocol-driven approach to diltiazem administration to maximize safety and efficacy 7
• Monitor blood pressure closely after diltiazem administration, as hypotension is the most common adverse effect 4
• Have emergency equipment readily available when administering either medication 3

Bottom Line

Diltiazem should be the first-line agent for rate control in hemodynamically stable patients with AFib with RVR without heart failure, as it achieves more rapid and effective rate control than amiodarone with fewer long-term adverse effects. Reserve amiodarone for patients with heart failure or when other rate control strategies have failed.