Cardiac preexcitation syndrome caused by an accessory atrioventricular pathway (Bundle of Kent) that bypasses the AV node; characterized by a short PR interval and a slurred "delta" wave on ECG.
Common cause of paroxysmal SVT in young patients and can lead to life-threatening arrhythmias (pre-excited atrial fibrillation can degenerate into ventricular fibrillation). Recognizing WPW is critical because certain medications (AV nodal blockers) can precipitate ventricular fibrillation.
Typically a young patient with sudden episodes of palpitations or tachycardia that start and stop abruptly (AV reentrant tachycardia). Most have structurally normal hearts.
Baseline ECG in sinus rhythm shows short PR interval (<120 ms) and a delta wave (slurred upstroke at the start of a slightly widened QRS complex).
Episodes can be triggered by exercise, stress, caffeine, or alcohol. Rarely, WPW presents as atrial fibrillation with an irregular, wide QRS tachycardia at very high rates (pre-excited AF).
Remember the WPW triad: short PR, delta wave, and widened QRS (fusion of normal and preexcited ventricular activation).
Distinguish orthodromic AVRT (regular narrow-complex SVT utilizing the AV node antegradely) from antidromic AVRT (regular wide-complex SVT with antegrade conduction via the accessory pathway). Treat narrow SVT like typical AVNRT (vagal maneuvers, adenosine), but wide-complex SVT should be treated with caution (consider it could be VT or antidromic AVRT).
Pre-excited atrial fibrillation (irregularly irregular wide-complex tachycardia in WPW) is a medical emergency – avoid AV node blockers and use procainamide or immediate cardioversion.
wide-complex tachycardia; in older patients or those with structural heart disease
Acute SVT (orthodromic AVRT): start with vagal maneuvers (Valsalva, carotid massage); if unsuccessful, give IV adenosine to terminate the reentrant circuit. If unstable, perform synchronized cardioversion.
Pre-excited AF or wide complex tachycardia: procainamide IV is the drug of choice to restore normal rhythm (or use IV ibutilide); avoid AV nodal blockers (beta-blockers, calcium channel blockers, digoxin, adenosine) as they can precipitate ventricular fibrillation. Urgent cardioversion if hemodynamically unstable.
Long-term: Definitive treatment is radiofrequency catheter ablation of the accessory pathway (curative in >95% of cases). Antiarrhythmic medications (e.g. class IC or III) are second-line if not ablating.
The accessory pathway in WPW is often called the Bundle of Kent.
Atrial fibrillation in WPW (pre-excited AF): presents as an extremely rapid, irregular tachycardia and can deteriorate into ventricular fibrillation (sudden cardiac death). Never give AV node–blocking drugs in this scenario.
WPW patients with syncope or episodes of atrial fibrillation (especially if the accessory pathway has a short refractory period) are at higher risk for SCD and should be referred for urgent evaluation (possible ablation).
Patient with palpitations → obtain ECG (look for WPW pattern: short PR, delta wave).
If WPW pattern is present: assess symptoms and risk. Asymptomatic patients without high-risk features can be observed with follow-up; symptomatic or high-risk patients should be referred to electrophysiology for risk stratification and possible ablation.
Acute tachyarrhythmia in WPW: if unstable → immediate cardioversion; if stable, determine rhythm: regular narrow SVT (treat with vagal maneuvers, adenosine) vs wide/irregular SVT (treat as WPW with AF – use procainamide, no AV nodal blockers).
Young adult with episodic palpitations and a delta wave on ECG → Wolff-Parkinson-White syndrome (accessory pathway causing AVRT).
Patient with WPW develops atrial fibrillation with very fast, irregular wide QRS complexes → pre-excited AF (risk of ventricular fibrillation).
Case 1
A 25‑year‑old man experiences sudden episodes of a racing heartbeat that resolve spontaneously.
12-lead ECG demonstrating the classic WPW pattern (short PR interval, delta wave at the start of a widened QRS).
