WPW Syndrome - How to Read ECG

Raja Selvaraj, JIPMER

Introduction

What is WPW syndrome?

  • Constellation of findings in patients with an accessory pathway with bidirectional conduction
  • Delta wave and short PR = preexcitation = antegrade conduction
  • Palpitations / tachycardia = Orthodromic AVRT = retrograde conduction
  • WPW pattern / preexcitation pattern

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ECG findings

Main ECG findings

  • Short PR interval
  • Delta wave

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The delta wave

  • Slurring of the initial part of the QRS
  • Fusion between conduction from pathway and AV conduction system
  • May be negative as well as positive
  • Contribution to QRS dependent on degree of fusion

Delta wave

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Localization - Not important

  • V1 delta = ventricle of origin
  • Inferior leads = superior / inferior

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Differentiate delta wave from others

  • Short PR
  • Old MI
  • Slurring

Middle aged male with Rheumatic MS

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Management

Problems

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Risk of sudden death

  • Rapid ventricular rate during atrial arrhythmias
  • AV node behaves as natural defense
  • AP - short refractory period, rapid conduction

Middle aged male with MS

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The low risk patient

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When to refer ?

  • Any patient with suspect / obvious preexcitation
  • Especially when history of palpitations
  • Urgently if there is history of syncope / preexcited AF

Management of ORT

  • Adenosine
  • Other AV nodal blocking drugs

Management of preexcited AF

  • Adenosine / beta blockers / calcium channel blockers should not be given
  • Amiodarone - (not considered safe)
  • Procainamide
  • DC cardioversion

Ablation

  • Curative treatment for pathways in all locations
  • Success rate > 95% with low recurrence rate
  • Low risk of complications