Wolff Parkinson White Syndrome

Wolff Parkinson White (WPW) syndrome is pre excitation from an accessory atrioventricular pathway (bundle of Kent) coupled with tachyarrhythmias.

ECG pre excitation prevalence 0.1 to 0.3%; symptomatic WPW syndrome less. Associated with Ebstein anomaly, hypertrophic cardiomyopathy (PRKAG2), familial forms.

Arrhythmias: orthodromic AVRT (narrow complex, anterograde via AV node, retrograde via accessory pathway; 80%), antidromic AVRT (wide complex), pre excited atrial fibrillation (can conduct rapidly to ventricles, potentially degenerating to ventricular fibrillation).

Sudden death risk about 0.1 to 0.6% per year, with ventricular fibrillation sometimes the first presentation in young people; risk higher with short anterograde refractory period of the pathway (under 250 ms), multiple pathways, and inducible AVRT.

• Palpitations from early adulthood, sudden onset and offset; lightheadedness, dyspnoea, chest pain, syncope.
• Many are asymptomatic with an incidental ECG finding.
• Rapid irregular wide complex tachycardia in pre excited AF: haemodynamic collapse or syncope.

• Resting ECG: short PR interval (under 120 ms), delta wave (slurred QRS upstroke), wide QRS (over 110 ms), secondary ST T changes. Location by delta wave polarity (Arruda algorithm).
• Intermittent pre excitation and abrupt loss with exercise suggest a low risk pathway.
• Holter monitoring and exercise testing.
• Electrophysiology study: accessory pathway location, shortest pre excited RR interval during AF (250 ms or less is high risk), inducible AVRT; risk stratification for asymptomatic athletes and high risk occupations.
• Echocardiography to exclude Ebstein anomaly and cardiomyopathy.

Acute

• Orthodromic AVRT (narrow complex): vagal manoeuvres, adenosine 6 to 12 mg IV, verapamil or diltiazem, cardioversion if unstable.
• Pre excited atrial fibrillation (irregular, wide complex, rapid): avoid AV nodal blockers (adenosine, verapamil, diltiazem, beta blockers, digoxin, amiodarone IV), which may precipitate ventricular fibrillation. Give procainamide 15 to 17 mg/kg IV over 30 to 60 minutes (maximum infusion 50 mg/min) or ibutilide 1 mg IV, or flecainide; immediate synchronised cardioversion (100 to 200 J) if unstable.
• Antidromic AVRT: procainamide or cardioversion.

Definitive

• Catheter ablation of the accessory pathway: first line for symptomatic WPW, success 95 to 98%, complication under 1% (heart block with septal pathways). Recommended for athletes, high risk occupations, and asymptomatic patients with high risk electrophysiological features.
• Pharmacological: flecainide 100 mg twice daily or propafenone 150 to 300 mg three times daily (structurally normal hearts), sotalol, amiodarone when ablation is not feasible; beta blockers or calcium channel blockers only in patients with concealed pathways or low risk intermittent pre excitation.
• Asymptomatic pre excitation: observation versus electrophysiology study; children under 8 years can be monitored; ablation in children with symptoms, structural disease or high risk.
• Pregnancy: procainamide or flecainide for acute episodes; ablation with minimal fluoroscopy.
• Sudden death prevention is a principal aim of ablation.