What are the chemical cardioversion options for atrial fibrillation?

Chemical Cardioversion Options for Atrial Fibrillation

For chemical cardioversion of atrial fibrillation, flecainide, dofetilide, propafenone, and intravenous ibutilide are the Class I recommended agents, with drug selection based primarily on the presence or absence of structural heart disease. 1

First-Line Agents by Clinical Context

Patients WITHOUT Structural Heart Disease or Ischemic Heart Disease

Flecainide and propafenone are the preferred first-line agents for pharmacological cardioversion in patients with no structural heart disease. 1

• Flecainide IV: 1.5–2 mg/kg over 10 minutes 1
• Flecainide oral: 200–300 mg single dose 1
• Propafenone IV: 1.5–2 mg/kg over 10 minutes 1
• Propafenone oral: 450–600 mg single dose 1

Key risks: Hypotension, atrial flutter with 1:1 conduction (potentially life-threatening), and QT prolongation. 1 These agents must be strictly avoided in patients with ischemic heart disease or significant structural heart disease due to increased mortality risk. 1

Patients WITH Structural Heart Disease or Ischemic Heart Disease

Amiodarone is the recommended agent when structural heart disease is present. 1

• Amiodarone IV: 5–7 mg/kg over 1–2 hours, followed by 50 mg/hour to a maximum of 1.0 g over 24 hours 1
• Oral maintenance: 100–200 mg daily 1

Important limitations: Amiodarone has delayed conversion to sinus rhythm (typically 8–12 hours), making it less suitable for urgent cardioversion. 1 However, it provides the advantage of simultaneous ventricular rate control. 1 Risks include phlebitis, hypotension, and bradycardia/AV block. 1

Ibutilide: Highly Effective but Requires Careful Monitoring

Ibutilide is a Class I recommended agent with superior efficacy, particularly for atrial flutter (63% conversion rate vs 31% for atrial fibrillation). 1, 2

• Dosing: 1 mg IV over 10 minutes, followed by a second 1 mg dose over 10 minutes after waiting 10 minutes if AF persists 1, 2
• Weight-adjusted dosing: 0.01 mg/kg if patient weighs <60 kg 2

Conversion typically occurs within 30 minutes of infusion start (70% of successful conversions), with the latest conversions seen at 90 minutes. 2, 3

Critical safety concern: Ibutilide carries a 3–4% risk of polymorphic ventricular tachycardia/torsades de pointes, requiring cardioversion in approximately 1.7% of patients. 1, 2, 3 Strict contraindications include: QT prolongation, hypokalemia, severe left ventricular hypertrophy, and low ejection fraction. 1 Continuous cardiac monitoring is mandatory during and for at least 4 hours after administration. 2

Vernakalant: Rapid Conversion with Specific Contraindications

Vernakalant offers rapid cardioversion with 51.7% efficacy at 90 minutes (superior to amiodarone's 5.7% in head-to-head comparison). 1

• Dosing: 3 mg/kg IV over 10 minutes, followed by 2 mg/kg over 10 minutes after waiting 15 minutes if needed 1

Absolute contraindications: Systolic blood pressure <100 mmHg, recent (<30 days) acute coronary syndrome, NYHA Class III-IV heart failure, QT interval prolongation (uncorrected QT >440 ms), and severe aortic stenosis. 1 Risks include hypotension, non-sustained ventricular arrhythmias, and QT/QRS prolongation. 1

"Pill-in-the-Pocket" Strategy for Selected Patients

For patients with infrequent symptomatic paroxysmal AF and no structural heart disease, single-dose oral flecainide (200–300 mg) or propafenone (450–600 mg) can be self-administered at home after safety has been established in a hospital setting. 1

This approach provides patient autonomy and is practical, though marginally less effective than hospital-based cardioversion. 1

Dofetilide: Effective but Requires Specialized Monitoring

Dofetilide is a Class I recommended agent for pharmacological cardioversion, but requires in-hospital initiation with continuous QT monitoring due to torsades de pointes risk. 1 This limits its practical use for acute cardioversion in most emergency settings.

Agents to Avoid for Acute Cardioversion

Digoxin, beta-blockers, and calcium channel blockers (verapamil, diltiazem) are ineffective for acute cardioversion and should not be used for rhythm conversion. 1 These agents are appropriate only for rate control, not rhythm control. 1

In patients with pre-excitation (WPW syndrome), digoxin, nondihydropyridine calcium channel blockers, and amiodarone are absolutely contraindicated as they can facilitate rapid AV conduction and precipitate ventricular fibrillation. 1 Procainamide or ibutilide are the preferred agents in this population. 1

Critical Anticoagulation Requirements

For AF ≥48 hours or unknown duration, therapeutic anticoagulation for at least 3 weeks before and 4 weeks after cardioversion is mandatory, regardless of whether chemical or electrical cardioversion is used. 1

For AF <48 hours with high stroke risk, IV heparin, LMWH, or direct oral anticoagulant should be administered before or immediately after cardioversion, followed by long-term anticoagulation. 1 The alternative is transesophageal echocardiography to exclude left atrial thrombus, allowing immediate cardioversion with concurrent anticoagulation. 1

Predictors of Successful Chemical Cardioversion

Factors favoring successful conversion include: shorter arrhythmia duration (<30 days shows 42-50% conversion vs 16-31% for chronic AF), atrial flutter rather than fibrillation, normal left atrial size, and younger age in women. 2, 4 Recent-onset AF (<48 hours) has significantly higher conversion rates with all agents. 1, 2

When Chemical Cardioversion Fails

If pharmacological cardioversion is unsuccessful, electrical cardioversion should be performed, which has >90% success rates. 1 Pre-treatment with antiarrhythmic drugs (amiodarone, sotalol, ibutilide, or vernakalant) can improve electrical cardioversion efficacy. 1