Wolff-Parkinson-White syndrome

Definition

In Wolff-Parkinson-White (WPW) syndrome, an accessory pathway connects atrium and ventricle, circumventing the AV node. When the pathway conducts antegradely, part of the ventricular myocardium is activated early (pre-excitation): short PR interval (below 120 ms), slurred QRS upstroke (delta wave) and widened QRS complex. Pre-excitation together with paroxysmal tachycardias defines manifest WPW syndrome.

Classification

• Manifest WPW syndrome: antegrade conduction over the pathway, pre-excitation on the resting ECG
• Concealed pathway: conducts only retrogradely; the resting ECG is normal, orthodromic tachycardia is still possible, but there is no risk of rapid conduction of atrial fibrillation
• About 5 % of people with an accessory pathway have multiple pathways.
• Permanent junctional reciprocating tachycardia (PJRT): rare, near-incessant form via a usually posteroseptal pathway that conducts only retrogradely and very slowly; may cause tachycardia-induced cardiomyopathy

Occurrence & epidemiology

Atrioventricular reentrant tachycardia (AVRT) is the most common tachycardia in WPW syndrome and accounts for about 20–30 % of all paroxysmal supraventricular tachycardias in adults. In children, AVRT is relatively more common than AV nodal reentrant tachycardia.

Clinical features

Tachycardia mechanisms

• Orthodromic AV reentrant tachycardia (AVRT), about 95 % of AVRT: antegrade conduction via the AV node, retrograde via the accessory pathway; narrow QRS complexes
• Antidromic AVRT (less common): reentry in the opposite direction, antegrade via the accessory pathway; wide QRS complexes

Typical are sudden-onset, sudden-offset, rapid, regular palpitations, often with dyspnea, chest discomfort or light-headedness. Attacks last seconds to hours. Most affected people become symptomatic in young adulthood or middle age.

If atrial fibrillation occurs with manifest pre-excitation, the rate-limiting effect of the AV node is lost; ventricular rates of sometimes 200–300/min can degenerate into ventricular fibrillation and sudden death. This is an emergency.

Diagnosis

• Resting ECG: short PR interval, delta wave and widened QRS complex with a manifest pathway; normal with a concealed pathway
• ECG during tachycardia (orthodromic AVRT): rapid, regular narrow-complex tachycardia; the retrograde P wave always follows the QRS complex and lies in the first half of the RR interval (RP shorter than PR), negative in II, III and aVF
• Antidromic AVRT: wide QRS complexes, because the ventricles are activated exclusively via the accessory pathway
• Atrial fibrillation with WPW: irregular, very rapid wide-complex tachycardia with varying QRS width
• Previous ECGs are reviewed for signs of pre-excitation; ambulatory ECG and electrophysiological study clarify the location and properties of the pathway.

Keep learning in the app

Further reading (open access)

1. MSD Manual Professional: Reentrant (Paroxysmal) Supraventricular Tachycardias (PSVT)
2. MSD Manual Professional: Atrial Fibrillation and Wolff-Parkinson-White Syndrome
3. StatPearls: Wolff-Parkinson-White Syndrome
4. Pre-Excited Atrial Fibrillation in Wolff-Parkinson-White (WPW) Syndrome (Rev Cardiovasc Med 2024, PMC11263991)

Cross-references