What’s the best next step in management for this pediatric patient?
A 17-year-old male with a history of Wolff-Parkinson-White syndrome awaiting ablation presents to the emergency department with palpitations. He is ambulatory to triage and talking comfortably with the nurse. His triage ECG is below.
ECG showing atrioventricular nodal reentrant tachycardia (nodal pathways) vs orthodromic atrioventricular reciprocating tachycardia (accessory pathways). The latter can be seen in pre-excitation conditions such as WPW. The narrow complex orthodromic AVRT makes it indistinguishable on standard 12 lead ECG from AVNRT. Both are treated with AV nodal blockade. This is notably different from wide complex antidromic AVRT (not pictured), which requires electrical cardioversion or procainamide.
Which of the following is the best next step in management?
- Adenosine
- Electrical cardioversion
- Metoprolol
- Procainamide
- Vagal maneuvers
Correct answer: E. Vagal maneuvers
The patient is experiencing orthodromic atrioventricular reciprocating tachycardia (AVRT), based on the narrow complex (<120ms) QRS complexes and the rate (slightly less than 300 based on boxes), which is all we are provided in the prompt. Narrow complex tachycardia, even with a history of WPW, is treated with AV nodal blockade. Since the patient is ambulatory and talking, he has a perfusing blood pressure. Certainly pads should be placed in anticipation of decompensation, but starting with vagal maneuvers is the best next step, just as it would be for SVT without a history of WPW, which would probably be atrioventricular nodal reentrant tachycardia.
Wide complex tachycardia in WPW must be treated with procainamide or electrical cardioversion and AV nodal blockade avoided. This is because the pathway is probably going retrograde through the AV node (antidromic rhythm creates wide complex) and blocking the AV node could send the pathway to a completely unchecked alternative route around it. See the illustration and ECG explanation below.
Incorrect answer choices:
Adenosine (Choice A) is the standard first medical therapy for SVT varieties (narrow complex or wide complex with aberrancy). Adenosine would be indicated if the vagal maneuvers fail. Initial dosing is 6mg by fast IV push, then 12mg if the 6mg fails.
Synchronized electrical cardioversion (Choice B) is indicated if the patient becomes hemodynamically unstable or if he fails adenosine and vagal maneuvers. Given the patient’s nontoxic appearance, electrical cardioversion is not the best first-line therapy, as it would expose the patient to the risks of procedural sedation and the cardioversion itself.
Metoprolol (Choice C) is a reasonable alternative to adenosine if a slower approach to cardioversion were chosen, but it is more often used for rate-controlling atrial fibrillation. It is not as effective as adenosine and has much slower time to effect.
Procainamide (Choice D) is the best medical therapy for antidromic AVRT, which would be wide complex.
