23-44: Wolff-Parkinson-White Syndrome

ECG Findings

• Normal P waves

• Shortened PR interval

• Prolonged QRS interval

• Delta waves (slurring of the initial upstroke of R wave)

Pearls

1. Accessory tracts from the atria to the ventricles lead to depolarization of ventricles without using the AV node as the primary connecting route.

2. Tachycardia associated with WPW may be mistaken for VT. Suspect WPW if the QRS complex is wide and tachycardia is extreme (ventricular rate > 240).

3. Do not treat irregular atrial tachycardias (atrial fibrillation) in the setting of WPW with AV nodal blocking agents (calcium channel blockers, β-blockers, digoxin). This may lead to unopposed ventricular stimulation through the accessory tract and may worsen the tachycardia.

4. Procainamide and cardioversion are accepted methods for conversion of a tachycardia associated with WPW.

5. Depolarization via the accessory pathway may produce “pseudo-Q waves.”