What is the most appropriate initial treatment for a child presenting with acute supraventricular tachycardia?

Treatment of Pediatric SVT

Adenosine is the most appropriate initial treatment for a child presenting with acute supraventricular tachycardia, regardless of whether hemodynamic stability is explicitly stated. 1, 2

Algorithmic Approach to Pediatric SVT

Step 1: Immediate Assessment

• If the child shows ANY signs of hemodynamic instability (shock, altered mental status, cardiovascular compromise), proceed directly to synchronized cardioversion at 0.5-1 J/kg without attempting pharmacologic interventions 1, 3
• If stability is uncertain or the child appears stable, proceed with pharmacologic management 1

Step 2: First-Line Pharmacologic Treatment

• Adenosine is the drug of choice (Class I recommendation) for pediatric SVT with effectiveness rates of 90-95% 1, 2, 4
• Dosing: 0.1 mg/kg rapid IV/IO bolus (maximum first dose 6 mg), followed by 0.2 mg/kg if needed (maximum second dose 12 mg) 2, 5
• Administer as a rapid push followed immediately by a saline flush 6, 4
• Important caveat: Infants respond poorly to the first dose of adenosine—only 1 of 17 infants responded to initial dosing in one study, with young age associated with decreased response 7

Step 3: If Adenosine Fails (Refractory SVT)

• Second and third doses of adenosine should be attempted before declaring treatment failure—most patients require mean doses of 173-249 µg/kg to achieve conversion 5
• Refractory SVT occurs in approximately 15% of cases, more frequently in infants 7
• For truly refractory cases, procainamide or amiodarone given by slow IV infusion with careful hemodynamic monitoring may be considered 1, 2

Step 4: Synchronized Cardioversion

• Reserved for hemodynamically unstable patients or when pharmacologic therapy fails 1
• Dosing: 0.5-1 J/kg, increasing to 2 J/kg if the first attempt is unsuccessful 1, 3

Why the Other Options Are Incorrect

Amiodarone (Option A)

• Not first-line for SVT—reserved for refractory cases only 1, 2
• 71% of children experience cardiovascular side effects (bradycardia, hypotension, cardiovascular collapse) that are dose-related 1, 2
• Most pediatric data involves postoperative junctional tachycardia, limiting generalizability to typical SVT 1, 2

Cardioversion (Option C)

• Only indicated as first-line if the patient is hemodynamically unstable 1, 3
• Since stability wasn't stated in this question, you must assume the child is stable enough to attempt adenosine first 1
• Synchronized cardioversion is rarely performed for acute SVT in practice—only 3 of 179 episodes in one large series 7

Beta Blocker (Option D)

• Not appropriate for acute SVT management—beta blockers are used for long-term prophylaxis in older children and adolescents, not acute conversion 2
• No role in emergency department treatment of acute SVT episodes 1

Critical Pitfalls to Avoid

• Never use verapamil in infants—it is absolutely contraindicated due to risk of severe hypotension, bradycardia, heart block, hemodynamic collapse, and death 1, 2
• Do not assume wide-complex tachycardia is SVT with aberrancy—always obtain a 12-lead ECG to differentiate from ventricular tachycardia before administering adenosine 8, 3
• Avoid AV nodal blocking agents (digoxin, calcium channel blockers, beta-blockers) if pre-excitation (Wolff-Parkinson-White) is suspected, as they can precipitate ventricular fibrillation 2
• Be prepared for reinitiation—SVT recurs within 5 seconds in approximately 11% of successfully converted cases, requiring repeat dosing 4

Practical Considerations

• Adenosine can be administered via intraosseous route if IV access is difficult, with successful conversion documented in pediatric cases 6
• Higher doses than traditionally recommended are often necessary—mean effective doses of 173 µg/kg (range up to 300 µg/kg) are reported in real-world practice 5
• Most patients (66%) can be discharged home from the emergency department after successful conversion without requiring intensive care admission 5

Answer: B - Adenosine