Is there a role for amiodarone in supraventricular tachycardia (SVT)?

Role of Amiodarone in Supraventricular Tachycardia (SVT)

Amiodarone should not be used as first-line therapy for SVT but may be considered for refractory cases when administered as a slow IV infusion with careful hemodynamic monitoring.

First-Line Management of SVT

Adenosine is the preferred first-line medication for SVT with a palpable pulse, based on extensive evidence demonstrating its effectiveness 1. The management algorithm for SVT should follow this sequence:

1. Vagal maneuvers - First attempt if patient is hemodynamically stable
2. Adenosine IV - First-line pharmacological therapy
3. Synchronized cardioversion - For hemodynamically unstable patients
4. Alternative medications - For refractory cases:
   • Verapamil (in older children/adults, contraindicated in infants)
   • Procainamide
   • Amiodarone (as last resort)

Amiodarone's Limited Role in SVT

Amiodarone should be reserved for refractory SVT cases that have failed to respond to first-line treatments. Its use in SVT is supported by limited evidence:

• One randomized prospective study and 15 small case series showed amiodarone was effective for supraventricular tachyarrhythmias, though most studies involved postoperative junctional tachycardia rather than typical SVT 1
• In a study of 85 patients with SVT refractory to multiple antiarrhythmic agents, amiodarone showed efficacy regardless of the underlying electrophysiologic mechanism 2

Significant Concerns with Amiodarone Use

Amiodarone carries substantial risks that limit its utility in SVT:

• High incidence of adverse effects: 71% of children treated with amiodarone experienced cardiovascular side effects 1
• Serious acute complications: Bradycardia, hypotension, cardiovascular collapse, and polymorphic VT have been reported 1
• Long-term toxicity: Pulmonary toxicity, hypothyroidism, and other adverse effects occur in approximately 50-59% of patients on long-term therapy 3, 4
• Poor long-term tolerability: Despite effectiveness, few patients tolerate amiodarone long-term, with only 19% of patients remaining on therapy at 50 months 4

Appropriate Administration When Indicated

If amiodarone is used for refractory SVT:

• Administer as a slow IV infusion with careful hemodynamic monitoring 1
• Consider pretreatment with a vasopressor to prevent hypotension 5
• Monitor for acute adverse effects including bradycardia and hypotension 1
• Use the Captisol-based formulation when available, as it has fewer hemodynamic side effects than the polysorbate-containing formulation 5

Established Role in Ventricular Arrhythmias

While amiodarone has limited utility in SVT, it has a well-established role in ventricular arrhythmias:

• First-line antiarrhythmic for VF/pulseless VT unresponsive to CPR, defibrillation, and vasopressor therapy 1, 5
• Preferred over lidocaine for refractory VF, with superior rates of hospital admission 5
• Effective for stable wide-complex tachycardias, particularly in patients with impaired left ventricular function or heart failure 1

Clinical Pitfalls to Avoid

• Do not use amiodarone as first-line therapy for SVT - adenosine is more effective with fewer side effects
• Do not administer amiodarone rapidly - this increases risk of hypotension and cardiovascular collapse
• Do not use in infants without extreme caution - they are particularly vulnerable to hemodynamic side effects
• Do not continue long-term without monitoring for pulmonary, thyroid, and other toxicities
• Do not use for SVT when the patient has a pre-excited atrial fibrillation - may accelerate ventricular response

In conclusion, while amiodarone has a definitive role in managing ventricular arrhythmias, its use in SVT should be limited to carefully selected cases of refractory SVT where other treatments have failed.