What is the difference between Wolff-Parkinson-White (WPW) syndrome and Lown-Ganong-Levine (LGL) syndrome in terms of electrocardiogram (ECG) changes, causes, and management strategies?

Wolff-Parkinson-White vs Lown-Ganong-Levine Syndrome: Key Differences

WPW syndrome and LGL syndrome are both pre-excitation syndromes with short PR intervals, but WPW features a delta wave and wide QRS complex due to an accessory pathway bypassing the AV node, while LGL syndrome shows a short PR interval with a normal narrow QRS complex, likely due to enhanced AV nodal conduction or a James bundle. 1, 2

ECG Changes

Wolff-Parkinson-White Syndrome

• PR interval <0.12 seconds 1
• Delta wave (slurring of initial QRS segment) - the pathognomonic feature 1
• Wide QRS complex >0.12 seconds 1
• Secondary ST-T wave changes that are discordant (opposite direction) to the major delta wave and QRS complex 1
• The degree of pre-excitation varies based on relative conduction through the AV node versus the accessory pathway 3
• Intermittent pre-excitation (abrupt loss of delta wave) indicates a longer accessory pathway refractory period and lower risk 3

Lown-Ganong-Levine Syndrome

• Short PR interval 2
• Narrow, pointed, positive P wave 2
• Normal narrow QRS complex (no delta wave) 2
• Tendency to respiratory arrhythmia 2

Causes and Pathophysiology

WPW Syndrome

• Accessory pathway (Bundle of Kent) creates a direct electrical connection between atria and ventricles, bypassing the AV node 1
• Prevalence of 0.15-0.25% in general population 3
• Higher prevalence (0.55%) in first-degree relatives, suggesting genetic component 3
• Associated conditions include:
  • Ebstein's anomaly (increases sudden death risk) 3
  • Multiple accessory pathways 3
  • Familial WPW (rare but high sudden death risk) 3
  • MELAS syndrome or LEOPARD syndrome 4

LGL Syndrome

• James bundle or short AV conduction pathway with small heart 2
• Enhanced AV nodal conduction 2
• Commonly affects young women with autonomic dystonia 2
• Associated with paroxysmal tachycardia tendency 2

Management Strategy

WPW Syndrome - Definitive Treatment

Catheter ablation is the first-line definitive therapy for symptomatic WPW patients, particularly those with syncope, documented AF, or short bypass tract refractory period (<250 ms). 3, 5

Indications for Catheter Ablation (Class I)

• Symptomatic patients with AF and WPW syndrome 3
• Syncope due to rapid heart rate 3
• Short bypass tract refractory period (<250 ms) 3
• Success rates: 88-95% primary success, 93-98.5% final success after repeat procedures 5
• Complication rates: 1-2% with experienced operators 5
• Procedure duration: approximately 4.5 hours 5

WPW Syndrome - Acute Management

Hemodynamically Unstable AF with Rapid Ventricular Response

Immediate electrical cardioversion is mandatory to prevent ventricular fibrillation. 3

Hemodynamically Stable Pre-excited AF

• Intravenous procainamide or ibutilide for wide QRS complex (≥120 ms) 3
• Alternative agents: quinidine, disopyramide, amiodarone (Class IIb) 3

Critical Contraindications (Class III)

Never administer AV nodal blocking agents in WPW with pre-excited AF: 3

• Digoxin - contraindicated 3
• Diltiazem - contraindicated 3
• Verapamil - contraindicated 3
• Beta-blockers - contraindicated (ineffective and may cause hemodynamic compromise) 3

These agents increase AV nodal refractoriness, encouraging preferential conduction over the accessory pathway, potentially accelerating ventricular response and precipitating ventricular fibrillation 3

Narrow QRS Tachycardia in WPW

• Intravenous adenosine may be used when QRS <120 ms, indicating anterograde conduction through AV node 3

WPW Syndrome - Risk Stratification

High-risk features for sudden cardiac death: 3, 6

• Shortest pre-excited R-R interval <250 ms during AF 3, 6
• History of symptomatic tachycardia 3, 6
• Multiple accessory pathways 3, 6
• Ebstein's anomaly 3, 6
• Familial WPW 3, 6

Sudden cardiac death incidence: 0.15-0.39% over 3-10 years follow-up 3, 6

LGL Syndrome - Management

The provided evidence does not contain specific management guidelines for LGL syndrome. Based on the clinical description, management would focus on:

• Treatment of paroxysmal tachycardia episodes when symptomatic 2
• Management of autonomic dystonia 2

Common Pitfalls

Critical mistake: Administering AV nodal blockers (digoxin, calcium channel blockers, beta-blockers) in WPW with AF can be fatal. 3 These agents block the AV node, forcing conduction exclusively through the accessory pathway, potentially causing ventricular fibrillation and cardiac arrest 3

WPW can mimic other conditions on ECG: bundle branch block, ventricular hypertrophy, or ischemic heart disease, leading to misdiagnosis 7

Asymptomatic WPW carries risk: In approximately 50% of WPW cardiac arrest cases, sudden death is the first manifestation 3, 6