What is the initial approach to chemical conversion for paroxysmal atrial fibrillation (AFib) in the emergency department (ED)?

Chemical Cardioversion for Paroxysmal Atrial Fibrillation in the Emergency Department

For paroxysmal atrial fibrillation in the emergency department, the initial approach to chemical cardioversion should be based on the patient's cardiac status, with class IC agents (flecainide or propafenone) as first-line therapy for patients without structural heart disease, and amiodarone or ibutilide for those with structural heart disease. 1

Initial Assessment and Risk Stratification

Before initiating chemical cardioversion, assess:

• Duration of AF (must be <48 hours for safe cardioversion without anticoagulation)
• Presence of structural heart disease
• Hemodynamic stability
• QT interval on ECG
• Serum electrolytes (especially potassium ≥4.0 mEq/L)
• Contraindications to specific antiarrhythmic medications

Algorithm for Chemical Cardioversion

For Patients WITHOUT Structural Heart Disease:

1. First-line agents: Class IC drugs (flecainide or propafenone)

   • Administer a beta-blocker or non-dihydropyridine calcium channel blocker 30 minutes before the class IC agent to prevent rapid AV conduction if atrial flutter develops 1
   • Monitor for QRS widening during administration

2. Second-line agents: Sotalol or ibutilide

   • Consider sotalol if baseline QT <450 ms and normal electrolytes 1
   • Ibutilide has shown 40-50% conversion rates within 90 minutes 2

3. Third-line agents: Amiodarone, disopyramide, procainamide, or quinidine 1

For Patients WITH Structural Heart Disease:

1. Heart Failure:

   • Amiodarone or dofetilide are preferred due to safety profile 1

2. Coronary Artery Disease:

   • Sotalol (first choice if no heart failure) 1
   • Amiodarone or dofetilide (second choice) 1

3. Hypertension without LVH:

   • Class IC agents (flecainide, propafenone) 1
   • If ineffective: amiodarone, dofetilide, or sotalol 1

4. Hypertension with LVH (wall thickness ≥1.4 cm):

   • Amiodarone (first choice due to lower proarrhythmic risk) 1

Specific Medication Considerations

• Ibutilide: More effective for atrial flutter (53-70% conversion) than atrial fibrillation (22-44%) 2

  • Monitor for QT prolongation and torsades de pointes
  • Conversion usually occurs within 30-90 minutes

• Amiodarone: Less effective for acute conversion but safer in structural heart disease

  • Longer conversion time compared to other agents 3
  • Loading regimens: 600 mg daily for 4 weeks or 1 g daily for 1 week 1

• Class IC agents: Highly effective but contraindicated in structural heart disease

  • "Pill-in-the-pocket" approach may be considered for subsequent episodes after successful and safe in-hospital trial 1

Important Caveats and Pitfalls

1. Proarrhythmic risk factors to assess before choosing an agent:

   • Female gender (higher risk with class IC agents) 1
   • QT prolongation
   • Electrolyte abnormalities
   • Bradycardia
   • Heart failure

2. Brugada syndrome: Avoid class I antiarrhythmic drugs as they may precipitate ventricular fibrillation 1

3. Recent research considerations: A 2019 study found that an electrical-first strategy resulted in shorter ED length of stay compared to chemical-first approach (3.5 vs 5.1 hours) 4

4. Anticoagulation: For AF <48 hours, immediate cardioversion can be performed without prior anticoagulation in patients without thromboembolic risk factors 1

5. Monitoring requirements: Continuous cardiac monitoring is essential during and after chemical cardioversion, with particular attention to:

   • PR interval (with flecainide, propafenone, sotalol, or amiodarone)
   • QRS duration (with flecainide or propafenone)
   • QT interval (with dofetilide, sotalol, amiodarone, or disopyramide) 1

By following this algorithm and considering the patient's specific cardiac status, chemical cardioversion of paroxysmal atrial fibrillation can be safely and effectively performed in the emergency department setting.