What is the role of Amiodarone in the treatment of Atrioventricular Nodal Reentrant Tachycardia (AVNRT)?

Role of Amiodarone in the Treatment of AVNRT

Amiodarone should be considered only as a third-line therapy for AVNRT in patients who are not candidates for catheter ablation and who have failed or cannot tolerate first-line and second-line medications. 1

First-Line Treatment Options

1. Catheter ablation of the slow pathway is the recommended first-line therapy for symptomatic AVNRT

   • Success rates of 95-97% with low complication rates
   • Potentially curative, eliminating need for chronic medication 1

2. Calcium channel blockers

   • Oral verapamil or diltiazem are first-line pharmacological options
   • Well-tolerated and effective for ongoing management 1
   • Contraindicated in patients with systolic heart failure

3. Beta blockers

   • Effective for ongoing management
   • Good safety profile 1

Second-Line Treatment Options

For patients who cannot take or do not respond to first-line medications:

1. Class Ic antiarrhythmics (flecainide, propafenone)

   • Contraindicated in structural heart disease or coronary artery disease 1

2. Sotalol or dofetilide

   • May be reasonable for ongoing management
   • Can be used in patients with structural heart disease
   • Require inpatient monitoring due to risk of QT prolongation and torsades de pointes 1

Amiodarone's Position in AVNRT Treatment

For Acute Management:

• Intravenous amiodarone may be considered only when other therapies are ineffective or contraindicated 1
• The 2020 ESC guidelines have downgraded amiodarone's recommendation for acute management of narrow-QRS tachycardias 1

For Chronic Management:

• Oral amiodarone "may be reasonable" (Class IIb recommendation) for ongoing treatment of AVNRT 1
• Reserved as a third-line therapy due to potential adverse effects 1
• Should only be used in patients who:
  1. Are not candidates for catheter ablation
  2. Have failed or cannot tolerate first-line agents (beta blockers, diltiazem, verapamil)
  3. Have failed or cannot tolerate second-line agents (flecainide, propafenone, sotalol, dofetilide) 1

Efficacy of Amiodarone in AVNRT

• Amiodarone is effective in suppressing AVNRT during outpatient follow-up 1
• One study showed that IV amiodarone (5 mg/kg over 10 minutes) terminated AVNRT in 7 out of 9 patients 2
• Long-term oral amiodarone therapy (200-400 mg daily) prevented recurrence and reinducibility of AVNRT 2
• Amiodarone works by:
  • Depressing both anterograde and retrograde limbs of the reentrant circuit in acute settings
  • Prolonging refractoriness and depressing conduction through the retrograde fast pathway with chronic use 2

Limitations and Risks of Amiodarone

• Significant potential for adverse effects with long-term use 1, 3
• Side effects occur in up to 93% of patients on long-term therapy 3
• Major concerns include:
  • Pulmonary toxicity
  • Thyroid dysfunction
  • Hepatotoxicity
  • Corneal microdeposits
  • Cutaneous reactions
  • Neurological effects (tremor, ataxia)
  • Cardiovascular effects (bradycardia, QT prolongation) 4, 3
• Requires careful monitoring and follow-up 4

Current Guideline Recommendations

The 2020 ESC guidelines have downgraded amiodarone's role in SVT management and no longer recommend it for:

• Acute management of narrow-QRS tachycardias
• Acute treatment of focal atrial tachycardia
• Acute treatment of AVNRT 1

Conclusion

While amiodarone can be effective for AVNRT, its use should be limited to specific situations where safer alternatives cannot be used due to its significant side effect profile. Catheter ablation remains the definitive treatment of choice for symptomatic AVNRT, with calcium channel blockers and beta blockers as the preferred pharmacological options.