Wolff-Parkinson-White syndrome

Definition
Wolff–Parkinson–White syndrome is a cardiac conduction disorder characterized by the presence of an accessory pathway (bundle of Kent) between the atria and ventricles, leading to episodes of tachyarrhythmia due to pre-excitation of the ventricles. It is a form of pre-excitation syndrome and can be congenital.

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Pathophysiology

• In normal conduction, impulses travel from the sinoatrial (SA) node → atrioventricular (AV) node → His–Purkinje system → ventricles

• In WPW, an accessory pathway bypasses the AV node, allowing impulses to travel directly from atria to ventricles

• This causes ventricular pre-excitation (early activation of ventricles)

• Can lead to atrioventricular reentrant tachycardia (AVRT) via re-entry circuits involving the accessory pathway and AV node

• In atrial fibrillation, the accessory pathway may conduct impulses rapidly to the ventricles, risking ventricular fibrillation

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Causes and Risk Factors

• Congenital: Abnormal persistence of embryonic myocardial tissue between atria and ventricles

• May occur sporadically or as part of syndromes (e.g., Ebstein anomaly)

• Family history (rare familial forms with autosomal dominant inheritance)

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Clinical Features

• Symptoms (intermittent or persistent):

  • Palpitations (most common)

  • Dizziness or lightheadedness

  • Syncope

  • Shortness of breath

  • Chest pain

• Severe presentations:

  • Sudden cardiac arrest (rare)

  • Very rapid ventricular rates in atrial fibrillation/flutter

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ECG Characteristics (when in sinus rhythm)

• Short PR interval (<120 ms)

• Wide QRS complex (>120 ms)

• Delta wave: Slurred upstroke at the beginning of QRS complex

• ST–T wave changes (secondary repolarization abnormalities)

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Diagnosis

• 12-lead ECG: Pathognomonic findings (short PR, delta wave) in sinus rhythm

• Holter monitoring: Detects intermittent pre-excitation or tachyarrhythmias

• Electrophysiological study: Maps accessory pathway location and properties

• Exercise testing may help in risk assessment (loss of pre-excitation with increased heart rate suggests lower risk)

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Treatment

1. Acute management of tachyarrhythmia in WPW

   • Orthodromic AVRT (narrow-complex tachycardia):

     • Vagal maneuvers (Valsalva, carotid sinus massage)

     • Adenosine (if vagal maneuvers fail and no contraindications)

   • Antidromic AVRT (wide-complex tachycardia):

     • Treat like ventricular tachycardia if uncertain; procainamide or ibutilide if confirmed WPW

   • Atrial fibrillation with WPW (urgent situation):

     • Avoid AV nodal–blocking agents (adenosine, beta-blockers, calcium channel blockers, digoxin) because they may increase conduction through the accessory pathway

     • Use procainamide or ibutilide; consider electrical cardioversion if unstable

2. Chronic management

   • Asymptomatic with WPW pattern: Risk stratification with electrophysiological study

   • Symptomatic or high-risk:

     • Catheter ablation of the accessory pathway is the definitive treatment (success rate >95%, low recurrence)

   • Antiarrhythmic drugs (e.g., flecainide, propafenone) may be used if ablation is not an option

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Prognosis

• Many individuals remain asymptomatic for life

• Risk of sudden cardiac death is low but higher in those with rapid conduction in atrial fibrillation

• Early detection and appropriate management significantly reduce risk

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Prevention and Lifestyle Advice

• Avoid stimulants that can precipitate tachycardia (e.g., caffeine, cocaine, amphetamines)

• In known WPW with symptoms, avoid drugs that block AV node unless instructed by a specialist

• Inform healthcare providers before starting any cardiac medication