Wolff–parkinson–white (Wpw) Syndrome

Wolff–parkinson–white (Wpw) Syndrome is a topic covered in the 5-Minute Emergency Consult.

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Basics

Description

  • 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: 2nd 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.

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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