Wolff–Parkinson–White syndrome

Background

• Abbreviation: WPW
• Congenital pre-excitation syndrome
• Presence of an accessory electrical pathway between atria and ventricles predisposing to supraventricular tachycardia
• Associated with certain genetic predispositions, Ebstein anomaly, and hypokalemic periodic paralysis

Type A

• Delta wave and QRS complex predominantly upright in precordial leads
• Dominant R wave (greater than S amplitude) in V1 may have appearance of right bundle branch block

Type B

• Delta wave and QRS complex predominantly negative in V! and V2
• Delta wave and QRS complex predominantly positive in other precordial leads
• Appearance of left bundle branch block

Orthodromic Type

• Most common variant (~95% of cases)
• Accessory pathway (Kent bundles) allows retrograde reentry conduction
• QRS narrow (delta wave absent)
  • Referred to as 'concealed' accessory pathway
• May see ST depression, TWI
• Rate 150-250 bpm

Antidromic Type

• Least common variant (~5% of cases)
• Accessory pathway used for anterograde conduction
• QRS wide, delta wave present
• Rate 160-220 bpm, regular

Atrial Fibrillation and Flutter

• Atrial fibrillation in up to 20% of patients with WPW
  • Irregular rhythm, wide QRS complexes
  • Changing QRS complexes in shape and morphology
  • Axis remains stable as opposed to polymorphic VT
• Atrial flutter in ~7% of patients with WPW
  • Similar features to atrial fibrillation with WPW
  • Except regular rhythm
  • Easily mistaken for monomorphic ventricular tachycardia
  • Note that if unclear, always safest to assume VT and treat with shock
• Treatment with AV nodal blocking agents (adenosine, beta-blockers, calcium-channel blockers, amiodarone, digoxin) may incite ventricular fibrillation or ventricular tachycardia
• "Manifest WPW" = degeneration into VT or VF

Clinical Features

• Suspect in any patient with ventricular rate >300

Infants

• Irritability, feeding intolerance
• CHF
• Intercurrent febrile illness

Children

• Chest pain, palpitations
• Shortness of breath
• Syncope/near-syncope

Adults

• Sudden onset "racing heart"

Differential Diagnosis

Palpitations

• Arrhythmias:
  • Narrow-complex tachycardias
  • Wide-complex tachycardias
  • AV blocks
    • Second Degree AV Block Type I (Wenckeback)
    • Second Degree AV Block Type II
    • Third Degree AV Block
  • Premature atrial contraction
  • Premature junctional contraction
  • Premature ventricular contraction
  • Sick sinus syndrome
  • Wandering atrial pacemaker
• Non-arrhythmic cardiac causes:
  • Acute coronary syndrome
  • Cardiomyopathy
  • Congenital heart disease
  • Congestive heart failure (CHF)
  • Mitral valve prolapse
  • Pacemaker complication
  • Pericarditis
  • Myocarditis
  • Valvular disease
• Psychiatric causes:
  • Panic attack
  • Anxiety
  • Somatic Symptom Disorder
• Drugs and Medications:
  • Alcohol
  • Caffeine
  • Drugs of abuse (e.g. cocaine)
  • Medications (e.g. digoxin, theophylline)
  • Tobacco
• Misc
  • Anemia
  • Hyperthyroidism
    • Thyroid storm
  • Pulmonary embolism
  • Dehydration
  • Sepsis
  • Pheochromocytoma

Evaluation

Workup

• ECG

Evaluation

Although the ECG and an electrophysiology study are diagnostic, the characteristic features are not always seen on ECG

• Short PR interval - <0.12sec
  • Due to loss of normal AV node conduction delay
  • Differentiate from premature junctional complex
• Delta wave / slurred upstroke
  • Due to early activation of ventricular myocardium
• QRS duration > 0.10 sec
  • Represents a fusion beat
• Dominant R wave in V1, Type A WPW
  • Left sided accessory pathway
• Dominant S wave in V1, Type B WPW
  • Right sided accessory pathway
• Tall R waves in V1-V3 with T wave inversion
  • Mimic RVH
• "Negative" delta waves in III and aVF
  • Appear as pseudo-infarct Q waves
  • Mimics prior inferior infarct

Management

Orthodromic

Treat like paroxysmal SVT

• Unstable
  • Cardioversion (synchronized)
  • Adult: 50-100 J
  • Peds: 0.5-2 J/kg
• Stable
  • Calcium channel blockers, beta-blockers, procainamide, or adenosine
  • Procainamide safe irrespective of type of pathway conduction

Antidromic

Treat like ventricular tachycardia

• Synchronized cardioversion
  • Adult: 50-100 J
  • Peds: 0.5-2 J/kg
  • Procainamide: 20-50mg/min IV over 30min (up to 17mg/kg, hypotension, or 50% widening of QRS complex); mainenance 1-4 mg/min
    • Avoid if prolong QT or CHF
  • Amiodarone with 'ABCD' drugs ie adenosine, beta-blockers, calcium-channel blockers, digoxin
• Wide-complex, irregular (presumed preexcited A-fib)
  • Unsynchronized cardioversion (200J)

Atrial Fibrillation and Atrial Flutter

• Stable
  • Procainamide 20-50 mg/min until arrhythmia suppressed
  • Synchronized cardioversion, 100 - 200 J
• Unstable - synchronized cardioversion
  • Consider higher joule dosage and frequency of repeats than for stable
• Avoid AV nodal blocking agents

Disposition

Discharge

• Consider if dysrhythmia was easily terminated and can arrange outpatient EP study with possible RF catheter ablation
• Consider consulting cardiologist regarding outpatient beta-blockers vs. more potent medications (amiodarone, sotalol, flecainide, etc.)

Admit

• Patients with chest pain, CHF, electrolyte imbalance, or required cardioversion
• Syncope
• Uncertain diagnosis (wide-complex tachycardia)
• Significant associated structural heart disease (MVP, cardiomyopathy)
• Family history of Sudden cardiac death
• Atrial flutter or atrial fibrillation

See Also

• Paroxysmal supraventricular tachycardia
• Atrial fibrillation (main)
• Atrial fibrillation with RVR
• Tachycardia (narrow)
• Tachycardia (wide)

External Links

WPW with AFIB