Wolff–Parkinson–White (Wpw) Syndrome

Basics

Description

  • Syndrome resulting from the presence of an abnormal (accessory) electrical pathway between the atria and ventricles that bypasses the AV node
  • Wolff–Parkinson–White (WPW) pattern on the ECG is defined by a short PR interval with a slurred QRS upstroke (Δ-wave) reflecting early conduction to the ventricles (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
  • Conduction in WPW may be antegrade, retrograde, or both
  • Orthodromic reentrant 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 reentrant 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 from the atria down the accessory pathway and retrograde through the AV node resulting in a wide QRS complex
  • Sudden death occurs in 1 per 1000 patient-years in persons with known ventricular pre-excitation

Etiology

  • Idiopathic:
    • Unknown mechanism in most cases, with familial predisposition
  • Rarely inherited as an autosomal dominant trait
  • Associated in rare cases with a familial hypertrophic cardiomyopathy

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