Wolff–parkinson–white (Wpw) Syndrome

Basics

Syndrome resulting from the presence of an abnormal (accessory) pathway that bypasses the AV node (Kent bundles) between the atria and ventricles
Wolff–Parkinson–White (WPW) pattern on the ECG is defined by a short PR interval and a Δ-wave reflecting early conduction (pre-excitation):
- Accessory pathways occur in 0.1–0.3% of the population
WPW syndrome requires ECG evidence of the accessory pathway and related tachycardia
Accessory pathways:
- Small bands of tissue that failed to separate during development:
  - Left lateral (free wall) accessory pathway: Most common
  - The posteroseptal region of the AV groove: Second most common location
  - Right free wall
  - Anteroseptal
Conduction in WPW may be antegrade, retrograde, or both
Orthodromic re-entrant tachycardia is the most common (70%):
- Impulse travels antegrade from the atria down the AV node to the ventricle and then retrograde up the accessory pathway
- This re-entrant tachycardia is a narrow complex rhythm unless a bundle branch block or intraventricular conduction delay is present
Antidromic is less common (30%):
- Impulse travels antegrade down the accessory pathway and retrograde through the AV node resulting in a wide quasi-random signal (QRS) complex
Sudden death occurs in 1 per 1,000 patient-years in persons with known ventricular pre-excitation

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