Amiodarone and Electrical Cardioversion
Amiodarone significantly increases the success rate of electrical cardioversion and prevents early recurrence of atrial fibrillation, making it the preferred antiarrhythmic agent for pre-treatment in patients with structural heart disease, heart failure, or when other agents are contraindicated. 1
Role in Electrical Cardioversion
Pre-Treatment Benefits
Amiodarone pre-treatment before electrical cardioversion substantially improves acute restoration of sinus rhythm and long-term maintenance. 2 The evidence demonstrates:
- Pre-treatment increases immediate cardioversion success by 22% (RR 1.22,95% CI 1.07-1.39) compared to no pre-treatment 2
- Spontaneous conversion occurs in 18-27% of patients during the loading phase before electrical cardioversion is even attempted 3, 1
- After failed initial cardioversion, amiodarone pre-treatment enables successful repeat cardioversion in approximately 59-88% of patients 3, 4
Optimal Dosing Strategy
The most effective regimens based on guideline evidence:
- Loading: 600-800 mg daily for 4 weeks or cumulative dose >6.0 g before cardioversion 5, 3
- Alternative rapid loading: 25-30 mg/kg as single oral dose achieves >85% conversion within 24 hours 6
- Maintenance: 200 mg daily after successful cardioversion 1, 5
Post-Cardioversion Maintenance
Amiodarone is superior to all other antiarrhythmic agents for maintaining sinus rhythm after cardioversion. 1
- 83% of patients remain in sinus rhythm at 6 months with amiodarone versus 43% with quinidine 1
- Median time to AF recurrence is 487 days with amiodarone versus 74 days with sotalol and 6 days with placebo 1
- At 12 months, 52-67% maintain sinus rhythm on low-dose maintenance therapy 5, 3
- Maintenance improves to 4.39-fold higher rates (RR 4.39,95% CI 2.99-6.45) compared to no treatment 2
Patient Selection Algorithm
First-Line Indications (Use Amiodarone)
Amiodarone should be the initial choice in patients with: 1
- Heart failure with reduced ejection fraction (LVEF ≤40%) - amiodarone has low proarrhythmic risk 1
- Severe left ventricular hypertrophy 1
- Coronary artery disease or previous myocardial infarction 1
- Failed initial cardioversion - enables successful repeat attempt 3
Second-Line Considerations
Use amiodarone cautiously as first-line in uncomplicated paroxysmal AF due to extracardiac toxicity risk, but it remains appropriate when other agents fail 1
Contraindications to Pre-Treatment
Do not use amiodarone for cardioversion in patients with: 1
- Sinus node dysfunction (unless pacemaker present)
- Atrioventricular conduction disturbances (unless pacemaker present)
- Prolonged QTc >500 ms
Mechanism of Benefit
Amiodarone enhances cardioversion success through multiple mechanisms: 1
- Reverses atrial electrical remodeling induced by chronic AF 1
- Suppresses atrial ectopy that triggers recurrence 1
- Reduces electrical threshold required for successful cardioversion 1
- Provides rate control if AF recurs, eliminating need for additional agents 1
Safety Profile
Short-term amiodarone for cardioversion is well-tolerated with minimal serious adverse effects. 2
- Non-serious adverse effects occur in only 3.4% of patients receiving short-term therapy 2
- 18% discontinuation rate occurs with long-term use (mean 468 days), primarily due to extracardiac toxicity 1
- No proarrhythmia observed in patients with compromised left ventricular function 5
- Cardioversion can be performed safely with standard precautions in amiodarone-treated patients 3
Critical Pitfalls
Mitral stenosis and very long-standing chronic AF predict amiodarone failure - logistic regression shows ineffectiveness in these subgroups 5
Higher doses (>1500 mg/day IV) are required for pharmacological cardioversion to be superior to placebo; lower doses are ineffective 6
Most conversions occur 6-8 hours after initiation - expect delayed rather than immediate effect 6
Side effects emerge with prolonged treatment - the 6-month safety advantage over quinidine diminishes with extended use 1