Wolff-Parkinson White

Question 1

What is WPW?

Answer 1

• Wolff-Parkinson White (WPW) syndrome is caused by a congenital accessory conducting pathway between the atria and ventricles leading to a atrioventricular re-entry tachycardia (AVRT)
• As the accessory pathway does not slow conduction AF can degenerate rapidly to VF

Question 2

What are ECG changes on WPW?

Answer 2

1. Short PR interval
2. Wide QRS complexes with a slurred upstroke - ‘delta wave’
3. Left axis deviation if right-sided accessory pathway*
4. Right axis deviation if left-sided accessory pathway*

*in the majority of cases, or in a question without qualification, Wolff-Parkinson-White syndrome is associated with left axis deviation

Question 3

How do you differentiate between type A and B WPW?

Answer 3

1. Type A (left-sided pathway): dominant R wave in V1
2. Type B (right-sided pathway): no dominant R wave in V1

**there is a rare type C WPW, WPW in which the delta waves are upright in leads V1-V4 but negative in leads V5-V6

Question 4

What is WPW associated with?

Answer 4

1. HOCM
2. Mitral valve prolapse
3. Ebstein’s anomaly
4. Thyrotoxicosis
5. Secundum ASD

Question 5

What is the managment of WPW?

Answer 5

1. Definitive treatment: radiofrequency ablation of the accessory pathway
2. Medical therapy: sotalol***, amiodarone, flecainide

***sotalol should be avoided if there is coexistent atrial fibrillation as prolonging the refractory period at the AV node may increase the rate of transmission through the accessory pathway, increasing the ventricular rate and potentially deteriorating into ventricular fibrillation