Wolff-Parkinson-White and Pre-excitation

Wolff-Parkinson-White (WPW) is the best known form of ventricular pre-excitation, in which an extra electrical connection, an accessory pathway, lets the signal bypass the atrioventricular node.

It matters in sport because, although uncommon, it is one of the few causes of sudden cardiac death (SCD) in young people that is often curable. Pre-excitation is seen in about 0.1 to 0.3% of the general population.

The WPW pattern is the electrocardiogram (ECG) finding alone; WPW syndrome is the pattern together with an arrhythmia. The sport and exercise medicine (SEM) clinician meets it through screening, palpitations or an incidental ECG, and recognises it, refers for risk assessment and advises on activity.

Normally the only route from atria to ventricles is the atrioventricular (AV) node, which slows the signal. In WPW an accessory pathway connects atrium to ventricle directly and conducts faster, so part of the ventricle is activated early. On the ECG this gives a short PR interval, a slurred QRS upstroke (the delta wave) and a broad QRS.

The pathway also creates a circuit:

• •Atrioventricular re-entrant tachycardia (AVRT): an impulse travels down one route and back up the other, giving a fast, regular rhythm and the usual palpitations.
• •Pre-excited atrial fibrillation (AF): rarer but dangerous. Without the AV node's slowing, a fast-conducting pathway can drive the ventricles very fast and degenerate into ventricular fibrillation (VF).

The risk depends largely on how quickly the accessory pathway can conduct.