What is the presentation of Wolff-Parkinson-White (WPW) syndrome?

Clinical Presentation of Wolff-Parkinson-White Syndrome

Wolff-Parkinson-White syndrome presents with characteristic ECG findings of ventricular pre-excitation (delta wave, short PR interval <0.12 seconds, widened QRS >0.12 seconds) and may be either asymptomatic or symptomatic with tachyarrhythmias, palpitations, syncope, or in rare cases, sudden cardiac death. 1, 2

Electrocardiographic Features (Diagnostic Hallmarks)

The ECG diagnosis requires all of the following features present simultaneously:

• Delta wave - slurring of the initial QRS upstroke due to ventricular pre-excitation via the accessory pathway, which is the defining feature that must be present 3, 2
• PR interval <0.12 seconds - shortened due to bypass of the AV node 2, 4
• QRS complex widening >0.12 seconds - total duration prolonged from fusion of pre-excited and normally conducted ventricular activation 2, 4
• Secondary repolarization changes - ST segment and T wave changes directed opposite (discordant) to the major delta wave and QRS complex 2

Important caveat: A short PR interval alone without delta waves does not constitute WPW and may represent normal variant conduction or enhanced AV nodal conduction 3

Clinical Presentations: Asymptomatic vs Symptomatic

Asymptomatic Presentation (WPW Pattern)

• Approximately 50% of patients with the WPW ECG pattern remain asymptomatic throughout their lives, discovered incidentally on routine ECG or during pre-participation sports screening 1
• The prevalence of asymptomatic WPW pattern is 0.1-0.3% in the general population 1, 5
• Critical warning: Sudden cardiac death may be the first manifestation in approximately 50% of cardiac arrest cases in WPW patients, occurring even in previously asymptomatic individuals 3, 4
• Annual risk of sudden death in asymptomatic patients is low (0.15-0.2%) but not zero 6

Symptomatic Presentation (WPW Syndrome)

When symptoms occur, they are secondary to tachyarrhythmias and include:

• Palpitations - the most common symptom, representing episodes of supraventricular tachycardia occurring in the majority of symptomatic patients 3, 2
• Syncope or presyncope - particularly concerning symptoms indicating rapid conduction over the accessory pathway with risk of sudden death 6, 3, 4
• Dizziness during tachyarrhythmia episodes 3
• Chest pain during arrhythmic episodes, though less common 3
• Shortness of breath indicating hemodynamic compromise during tachyarrhythmias 3
• Fatigue, especially during activities like driving (57% of patients with supraventricular tachycardia experience episodes while driving) 3

Arrhythmic Manifestations

The tachyarrhythmias encountered in WPW patients include:

• Atrioventricular reciprocating tachycardia (AVRT) - accounts for 95% of reentrant tachycardias in WPW, typically narrow QRS complex with anterograde conduction through the AV node and retrograde through the accessory pathway 3, 7, 2
• Pre-excited atrial fibrillation - the most dangerous arrhythmia, occurring in 0-9% of asymptomatic patients and up to one-third of all WPW patients, characterized by wide QRS complexes with irregular rhythm 1, 3, 5
• Atrial flutter - less common but can conduct rapidly over the accessory pathway 2
• Ventricular fibrillation - occurs in 0-2% of asymptomatic patients when atrial fibrillation degenerates due to very rapid ventricular rates via the accessory pathway 1, 3

High-Risk Features Predicting Sudden Death

Specific characteristics identify patients at increased risk for life-threatening events:

• Shortest pre-excited RR interval <250 ms during atrial fibrillation - the strongest predictor of sudden cardiac death risk 1, 6, 3
• History of symptomatic tachycardia - increases sudden death risk, with symptomatic patients having 2.2% annual risk versus 0.15-0.2% in asymptomatic patients 1, 6
• Multiple accessory pathways - associated with higher risk 1, 3
• Posteroseptal pathway location - identified as higher risk 1
• Young age - highest risk appears in the first two decades of life, with sudden death occurring more frequently in exercising individuals 3, 4

Low-Risk Indicators

Certain findings suggest benign accessory pathway properties:

• Intermittent pre-excitation on resting ECG or ambulatory monitoring indicates low risk with 90% positive predictive value 1, 3
• Abrupt loss of pre-excitation during exercise testing suggests long accessory pathway refractory period and low sudden death risk 1, 3

Associated Structural Heart Disease

WPW may occur with concomitant cardiac abnormalities requiring evaluation:

• Ebstein's anomaly - congenital heart defect associated with increased risk 3, 5
• Hypertrophic cardiomyopathy 3
• PRKAG2-related familial WPW with glycogen storage cardiomyopathy 3
• Most patients (93-95%) have structurally normal hearts 1, 5

Special Population Considerations

Athletes

• WPW accounts for at least 1% of sudden death in athletes 4
• Risk of lethal arrhythmia appears higher in asymptomatic children than adults 4
• Sudden cardiac death is often the sentinel event in athletic individuals 4

Pediatric Patients

• Ventricular fibrillation occurs predominantly in children (0-2% of asymptomatic patients) 3
• Higher risk of sudden death in the first two decades of life 3

Common Diagnostic Pitfalls

• Left lateral accessory pathways may show minimal delta waves due to fusion with normal AV nodal conduction, potentially appearing as intermittent pre-excitation when actually continuously present 3
• Careful ECG inspection is necessary to ensure delta waves are truly absent rather than subtle 3
• Short PR interval without delta waves requires evaluation for other conditions like Lown-Ganong-Levine syndrome only if recurrent unexplained tachyarrhythmias occur 3