Management of WPW Syndrome and AVRT in Infants

Definitions & Epidemiology

WPW syndrome is defined as the presence of a ventricular pre‑excitation pattern on ECG (short PR interval with a delta wave) plus documented supraventricular tachycardia or SVT‑consistent symptoms; the most common tachyarrhythmia in this setting is orthodromic atrioventricular re‑entrant tachycardia (AVRT). [AHA] 1
The WPW pattern (asymptomatic pre‑excitation) refers to the ECG finding of a short PR interval and delta wave without any documented arrhythmia or related symptoms. [AHA] 1
AVRT is a re‑entrant tachycardia that requires an accessory pathway linking atrium and ventricle; orthodromic AVRT accounts for 90‑95 % of cases and presents with a narrow QRS complex, whereas antidromic AVRT accounts for ≈5 % and presents with a wide, maximally pre‑excited QRS. [AHA] 4
In children, the average age of first AVRT symptom onset is 8 years, but presentations can occur in infancy; among individuals < 21 years with a WPW pattern, 64 % are symptomatic at presentation and an additional 20 % develop symptoms during follow‑up. [AHA] [1][6]

First‑line acute therapy is vagal stimulation (e.g., applying an ice‑cold wet towel to the infant’s face) followed immediately by intravenous adenosine if the maneuver fails. [AHA] [7][8]
Adenosine terminates orthodromic AVRT in ≈95 % of cases and provides diagnostic confirmation of the tachycardia mechanism. [AHA] [5][8]
In hemodynamically unstable infants, synchronized cardioversion should be performed without delay when vagal maneuvers or adenosine are ineffective or not feasible. [AHA] [7][9]
For hemodynamically stable orthodromic AVRT that does not respond to adenosine, synchronized cardioversion is recommended; intravenous β‑blockers, diltiazem, or verapamil may be considered only with extreme caution in infants. [AHA] [7][9]

AV nodal‑blocking agents (digoxin, verapamil, diltiazem, β‑blockers) must be avoided in pre‑excited atrial fibrillation because they can precipitate ventricular fibrillation. [ESC] [9][10]
Verapamil is specifically contraindicated in infants with WPW due to the risk of catastrophic cardiovascular collapse. [ESC] 10
Digoxin is absolutely contraindicated in WPW at any age, as it shortens the refractory period of the accessory pathway and may facilitate rapid ventricular rates during atrial fibrillation. [ESC] 10
In stable pre‑excited atrial fibrillation, intravenous ibutilide or procainamide is recommended; immediate synchronized cardioversion is indicated if the patient is unstable. [AHA] [7][9]

β‑blockers are recommended as first‑line prophylactic agents in infants with WPW syndrome, provided the accessory pathway does not conduct rapidly anterogradely (a condition that should be confirmed when possible). [AHA] 11
If β‑blocker therapy fails, flecainide is an effective second‑line option, achieving arrhythmia control in ≈69 % of pediatric series. [AHA] 11
Propafenone, often combined with a β‑blocker, has shown no recurrence of tachycardia in a small cohort (10 patients) over a mean follow‑up of 9 ± 6 months. [AHA] 11

Catheter ablation (radio‑frequency or cryoablation) is now the treatment of choice for symptomatic WPW syndrome, offering high acute success rates and an excellent safety profile in experienced centers. [AHA] 4

The 10‑year risk of SCD in patients with a manifest accessory pathway is estimated at 0.15‑0.24 %; the risk is highest during the first two decades of life. [AHA] [4][7]
Factors that increase SCD risk include a history of symptomatic tachycardia, the presence of multiple accessory pathways, and a shortest pre‑excited R‑R interval < 250 ms during atrial fibrillation. [AHA] [4][5]
Childhood SCD incidence is approximately 0.5 %; cardiac arrest may be the first manifestation of WPW‑related disease. [ESC] 10
A complete 2‑dimensional echocardiogram is recommended in every infant with a pre‑excitation pattern to exclude structural heart disease. [ESC] 10
Congenital heart disease is present in up to 45 % of infants with right‑sided accessory pathways, with associated anomalies including Ebstein’s anomaly, L‑transposition of the great arteries, hypertrophic cardiomyopathy, and cardiac tumors. [ESC] 10
Transesophageal programmed stimulation can be employed for risk stratification in selected patients when non‑invasive assessment is insufficient. [ESC] 10

Never use digoxin in WPW syndrome; two reported infant deaths underscore its absolute contraindication. [ESC] 10
Never administer verapamil to infants with WPW because of the documented risk of cardiovascular collapse. [ESC] 10
Do not confuse the WPW pattern (ECG finding alone) with WPW syndrome (pattern + clinical arrhythmia); management strategies differ markedly. [AHA] 1
Avoid AV nodal blockers in wide‑complex tachycardias or pre‑excited atrial fibrillation, as they may precipitate ventricular fibrillation. [AHA] [9][10]
Do not assume a benign course; approximately 0.2 % of patients present with sudden cardiac death as the initial manifestation. [AHA] [1][6]