Amiodarone for Rapid Rate Atrial Fibrillation
Primary Recommendation
Intravenous amiodarone should be reserved as a second-line agent for rate control in AF with rapid ventricular response, used specifically when conventional agents (beta-blockers or calcium channel blockers) fail, are contraindicated, or in critically ill patients with hemodynamic instability or heart failure. 1
Clinical Decision Algorithm
Step 1: Assess Hemodynamic Stability and Cardiac Function
Hemodynamically unstable patients:
- Proceed directly to electrical cardioversion—do not delay for pharmacologic rate control 1, 2
- If cardioversion unavailable or unsuccessful, IV amiodarone is indicated for acute rate control 1, 3
Hemodynamically stable patients with preserved ejection fraction:
- First-line: IV beta-blockers (metoprolol, esmolol) or non-dihydropyridine calcium channel blockers (diltiazem, verapamil) 1, 2
- Target resting heart rate <80 bpm for symptomatic management 1
- Do not use amiodarone as first-line therapy 1
Patients with heart failure or reduced ejection fraction:
- First-line: IV digoxin or IV amiodarone (Class I recommendation) 1
- Avoid beta-blockers and calcium channel blockers in decompensated HF 1, 2
- IV amiodarone is specifically recommended for acute rate control in this population 1
When to Use Amiodarone
Appropriate Indications (Class IIa-IIb)
IV amiodarone is reasonable for:
- Critically ill patients without pre-excitation when conventional measures fail (Class IIa) 1
- Patients with severe LV dysfunction, HF, or hemodynamic instability 1
- Acute coronary syndrome with AF when severe LV dysfunction or HF present 1
- Rate control refractory to beta-blockers and calcium channel blockers 4
Oral amiodarone may be considered when:
- Other rate control measures are unsuccessful or contraindicated (Class IIb) 1
- Resting and exercise heart rate cannot be adequately controlled with standard agents 1, 2
Dosing Regimens
IV Amiodarone for Acute Rate Control
Loading dose:
- 150-300 mg IV over 10-30 minutes, followed by continuous infusion 5, 6
- Alternative: 10 mg/kg over 30 minutes (approximately 700 mg for 70 kg patient) 5
- Rate control typically occurs after first 300-400 mg 6
Maintenance infusion:
- 1 mg/min for 6 hours, then 0.5 mg/min for 18 hours 6
- Total dose typically 1,000 mg or more over 24 hours for optimal effect 6
- Do not give as one-time push alone—requires loading dose followed by continuous infusion 3
Oral loading (if transitioning):
- 800 mg/day for 6 weeks, then reduce to 600 mg/day maintenance 7
- High-dose oral loading can worsen hemodynamics in patients with recent HF decompensation or hypotension 1
Critical Contraindications
Absolute Contraindications
Never use amiodarone (IV or oral) in:
- Pre-excited AF (Wolff-Parkinson-White syndrome)—can accelerate ventricular response and cause ventricular fibrillation (Class III: Harm) 1, 2
- Use procainamide or ibutilide instead for pre-excited AF 1, 2
Expected Clinical Response
Timeline and Effects
Rate control:
- Most immediate and predictable response 6
- Ventricular rate reduction typically within 1 hour of loading dose 4
- Mean heart rate reduction of 37 beats/min in critically ill patients 4
Cardioversion to sinus rhythm:
- Less predictable—occurs in approximately 44-51% of patients 5
- When it occurs, typically requires 24 hours and total dose ≥1,000 mg 6
- Not superior to digoxin for pharmacologic cardioversion 5
Hemodynamic effects:
- Generally well tolerated in critically ill patients 1, 4
- May increase systolic blood pressure by ~24 mm Hg while reducing heart rate 4
- Improves cardiac output and pulmonary artery occlusive pressure 4
Monitoring Requirements
During IV Administration
Continuous monitoring required:
- Cardiac telemetry for heart rate and rhythm 4
- Blood pressure monitoring—watch for hypotension (though less common than with beta-blockers/CCBs) 4
- Assess for bradycardia, especially if combining with other AV nodal blockers 1
Long-term Monitoring (if continuing oral therapy)
Amiodarone causes significant toxicity in ~50% of patients on chronic therapy: 7
- Pulmonary function tests and chest X-ray (pulmonary fibrosis risk 5%) 1, 7
- Thyroid function tests (abnormalities in 6% of patients) 7
- Liver function tests (hepatic injury risk) 1
- Ophthalmologic examination (visual halos/blurring in 6%) 7
- Neurologic assessment (tremor/ataxia in 35%) 7
Critical Pitfalls to Avoid
Common Errors
Do not use amiodarone as first-line therapy in patients with preserved cardiac function:
- Beta-blockers and calcium channel blockers are more appropriate and safer 1, 2
- Amiodarone's significant toxicity profile makes it unsuitable for routine use 8
Do not combine with other AV nodal blockers without dose adjustment:
- Amiodarone increases effects of beta-blockers and digoxin 9
- Start beta-blockers at lower doses if adding to amiodarone 9
- Risk of severe bradycardia with combination therapy 1
Do not use in pre-excited AF:
- Can precipitate ventricular fibrillation 1
- Also avoid digoxin and calcium channel blockers in this setting 1
Do not underestimate long-term toxicity:
- Non-cardiovascular mortality may be increased with chronic amiodarone use 8
- Severe or fatal outcomes can occur years after initiation 8
- Consider catheter ablation or other antiarrhythmics in patients without significant structural heart disease 8
Comparison with Alternative Agents
Why Amiodarone is Second-Line
Beta-blockers and calcium channel blockers are preferred because:
- More rapid onset of action for rate control 5
- Better safety profile for acute use 1
- Lower risk of serious adverse effects 5
Amiodarone advantages in specific situations: