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Internal Medicine

Wolff-Parkinson-White Syndrome

Cover image: Wolff-Parkinson-White syndrome (WPW) is a pre-excitation syndrome of intermittent tachycardia that results from an accessory pathway (the bundle of Kent) directly connecting the atria and the ventricles. The anomalous pathway allows electrical activity to bypass the AV node to produce pre-excitation. WPW has characteristic ECG findings of a short PR interval, wide QRS complex, and the delta wave (slurred upstroke in the QRS complex). The condition is associated with atrioventricular reentrant tachycardia (AVRT) and atrial fibrillation. | MedComic/Jorge Muniz

Cardiac conduction system disorder characterized by abnormal accessory conduction pathways between the atria and the ventricles.

  • Newborns & infants > adults (∴ accessory pathways represent embryologic remnants)

History

Frank Norman Wilson (1890–1952) became the first to describe the condition in 1915. Alfred M. Wedd (1887–1967) was the next to describe the condition in 1921. Cardiologists Louis Wolff (1898–1972), John Parkinson (1885–1976) and Paul Dudley White (1886–1973) are credited with the definitive description of the disorder in 1930.

Wolff-Parkinson-White (WPW) syndrome was first described in 1930 in a landmark article in the American Heart Journal, in which the authors reported a case series of 11 otherwise healthy patients with electrocardiogram (ECG) findings of a short PR interval and “bundle branch block” morphology who also suffered from paroxysmal supraventricular tachycardia (SVT) or atrial fibrillation (AF). Shortly after the description, electrophysiologists were able to elucidate the relationship between accessory pathways and reentrant SVT. However, it was not until nearly 40 years later that rapid conduction of AF was identified as the mechanism of sudden death.

Louis Wolff, Sir John Parkinson and Paul Dudley White, who discovered the phenomenon that later would be called the WPW syndrome.

Etiology

Associated with structural heart disease:

  • Ebstein anomaly
  • Hypertrophic cardiomyopathy
Graphic representation of the bundle of Kent in Wolff–Parkinson–White syndrome | By Tom Lück – Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=12841683

Complications

The Calgary Guide | http://calgaryguide.ucalgary.ca/
  • Supraventricular tachydysrhythmias
  • Sudden cardiac death (SCD) (rare)

Diagnosis

Noninvasive methods (for risk stratification in asymptomatic cases):

  • Holter monitor (records electrical properties of heart over an extended period, typically 24-48 hours)
  • Echocardiogram (rule out structural heart disease associated with WPW)

Electrophysiologic (EP) studies (elucidate accessory pathway properties in symptomatic cases):

  • Intracardiac catheterization
  • Transesophageal studies

ECG findings:

  • Characteristic findings:
    • Delta wave (slurred upstroke in the QRS complex)
    • Short PR interval < 120 ms
    • Widened QRS complex > 120 ms
      • Due to depolarization of the ventricles via accessory pathway
  • Other (subtle) findings:
    • Left-axis deviation
    • Abnormal Q waves (leads V5 & V6)
    • ST-segment depression
    • T-wave changes
Characteristic ECG findings in WPW. Note the presence of a short PR interval (<120 ms) and delta wave (slurred upstroke of the QRS complex). ECG, electrocardiogram. | Rao, A. L., Salerno, J. C., Asif, I. M., & Drezner, J. A. (2014). Evaluation and management of wolff-Parkinson-white in athletes. Sports Health, 6(4), 326–332. https://doi.org/10.1177/1941738113509059

Management

Transcatheter ablation (first-line treatment):

  • Radiofrequency ablation (RFA) ± cryoablation (GOLD STANDARD)
    • Extinguishing accessory pathways and lower recurrence rate

Medical management:

Prevent arrhythmias & slow ventricular response
  • Procainamide (Class IA antiarrhythmic)
  • Amiodarone (Class III antiarrhythmic)

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