What is the next treatment of choice for supraventricular tachycardia (SVT) in an infant with heart failure that has not responded to 2 doses of adenosine?

Management of Refractory Supraventricular Tachycardia in an Infant with Heart Failure

For an infant with heart failure and supraventricular tachycardia (SVT) not responding to two doses of adenosine, synchronized electrical cardioversion is the next treatment of choice. 1

Treatment Algorithm for Refractory SVT in Infants

First-Line Approach: Synchronized Cardioversion

1. Immediate synchronized cardioversion at 0.5-1 J/kg 1
   • If unsuccessful, increase to 2 J/kg 1
   • Use sedation if possible before cardioversion 1
   • This is particularly important in the setting of heart failure, as rapid termination of the arrhythmia is critical to prevent further hemodynamic deterioration

Second-Line Pharmacological Options (if cardioversion fails or is delayed):

1. Procainamide:

   • Administer 15 mg/kg IV/IO via slow infusion 1
   • Evidence suggests procainamide has a significantly higher success rate with equal adverse effects compared to amiodarone for refractory SVT 1
   • Monitor for hypotension, which occurs due to vasodilation rather than decreased myocardial contractility 1

2. Amiodarone (if procainamide unavailable):

   • Administer via slow IV infusion with careful hemodynamic monitoring 1
   • Dosing: 5 mg/kg IV/IO 1
   • Be aware of potential adverse effects including bradycardia, hypotension, and cardiovascular collapse 1
   • FDA label indicates amiodarone is primarily indicated for ventricular arrhythmias rather than SVT 2

Important Considerations and Precautions

Heart Failure Complications

• The presence of heart failure significantly increases the urgency for termination of SVT
• Prolonged SVT can worsen heart failure, creating a dangerous cycle 1
• Rapid restoration of sinus rhythm is essential to improve cardiac output

Medication Precautions

• Avoid verapamil in infants as it can cause severe hypotension, bradycardia, and heart block leading to hemodynamic collapse and death 1
• Monitor closely during administration of any antiarrhythmic medication, particularly in the setting of heart failure
• Be prepared to provide hemodynamic support with vasopressors if needed during medication administration

Post-Conversion Management

• Once sinus rhythm is achieved, initiate maintenance therapy to prevent recurrence
• Consider digoxin and/or beta-blockers for long-term management 1
• For infants with recurrent episodes, amiodarone may be considered for maintenance therapy 3

Evidence Quality and Considerations

The recommendation for synchronized cardioversion as the next step is based on high-quality guidelines from the American Heart Association and American College of Cardiology 1. While some evidence suggests that higher doses of adenosine might be effective in refractory cases 4, the presence of heart failure necessitates the most rapid and reliable method of terminating the arrhythmia, which is synchronized cardioversion.

The choice between procainamide and amiodarone as pharmacological alternatives is based on a Level of Evidence 2 pediatric comparison study showing procainamide's superior efficacy with similar safety profile 1.

In the specific context of an infant with heart failure and SVT refractory to adenosine, prioritizing rapid restoration of sinus rhythm through synchronized cardioversion represents the approach most likely to reduce morbidity and mortality.