Wolff-Parkinson-White syndrome

The Wolff-Parkinson-White pattern is a preexcitation syndrome characterised by the presence of an accessory conduction pathway which bypasses the AV node, called the bundle of Kent. The AV node delays the conduction to the ventricles, but people with WPW have this accessory pathway which doesn’t have this built-in delay, so this accessory pathway causes the depolarisation of the ventricles to occur earlier. This is apparent on the ECG as the “delta wave”, which is where the QRS complex gets a small “head start” at the expense of the PQ interval. The delta wave causes the QRS complex to be wider than normal. However, the delta wave pattern on the ECG may be intermittent. As such, the characteristic ECG findings are the follows:

• Shortened PQ/PR interval (< 120 ms)
• Presence of delta wave
• Widened QRS complex

Wolff-Parkinson-White syndrome is characterised by the presence of WPW pattern and the occurrence of paroxysmal tachycardia. WPW syndrome occurs in as little as 2% of people with WPW pattern. The remaining 98% are asymptomatic.

Treatment

Asymptomatic people with WPW pattern rarely require treatment, although treatment should be considered if they develop an episode of paroxysmal tachycardia, usually atrioventricular reciprocating/reentry tachycardia (AVRT) or pre-excited atrial fibrillation.

Once terminated, the patient should receive therapy to prevent recurrence of the paroxysmal tachycardia. The first choice is catheter ablation of the accessory pathway. Oral flecainide or propafenone are second line options.