Clinical Manifestations of Wolff-Parkinson-White Syndrome
Wolff-Parkinson-White syndrome can present with a spectrum of clinical manifestations ranging from asymptomatic pre-excitation to life-threatening arrhythmias, with sudden cardiac death occurring at a rate of approximately 0.15% per year due to atrial fibrillation degenerating into ventricular fibrillation. 1
Electrocardiographic Features
The classic ECG findings in WPW syndrome include:
- PR interval less than 0.12 seconds
- Delta wave (slurring of initial segment of QRS complex)
- QRS complex widening (duration greater than 0.12 seconds)
- Secondary repolarization changes (ST segment-T wave changes directed opposite to delta wave) 2
Symptomatic Presentations
Tachyarrhythmias
- Atrioventricular reentrant tachycardia (AVRT): Most common arrhythmia in WPW syndrome
- Pre-excited atrial fibrillation: Occurs in up to 50% of patients with WPW 3
- Atrial flutter
- Ventricular fibrillation: Most serious complication, can lead to sudden cardiac death
Symptoms During Arrhythmic Episodes
- Palpitations
- Dizziness
- Presyncope
- Syncope
- Chest discomfort
- Dyspnea
- Anxiety
- Diaphoresis
- Fatigue
- Polyuria (due to atrial natriuretic peptide release during tachycardia)
Asymptomatic Presentation
Approximately 50% of patients with WPW ECG pattern have no history of arrhythmias 1. However, it's important to note that sudden cardiac death may be the first manifestation of the disease in some patients.
Risk Factors for Sudden Cardiac Death
Patients at higher risk for sudden cardiac death typically demonstrate:
- History of symptomatic tachycardia
- Short RR intervals (<250 ms) between pre-excited beats during atrial fibrillation
- Multiple accessory pathways
- Posteroseptally located pathways 1, 4
Associated Conditions
While most patients with WPW syndrome have normal cardiac anatomy, it may be associated with:
- Ebstein's anomaly (2-4% of cases)
- Other congenital heart diseases
- Systemic diseases 5
Reduced Exercise Capacity
For some specific locations of accessory pathways with overt anterograde conduction, there might be:
- Reduction in exercise capacity
- Decreased LV systolic performance due to anomalous LV depolarization 5
Age and Sex Distribution
WPW syndrome affects approximately 0.1-0.3% of the general population 5, 2. It is more common in males, with studies showing male preponderance (63%) among asymptomatic patients 1.
Clinical Course
The natural history of WPW syndrome varies:
In observational cohorts of asymptomatic patients who did not undergo catheter ablation:
- Regular supraventricular tachycardia or benign atrial fibrillation develops in 0-16%
- Malignant atrial fibrillation develops in 0-9%
- Ventricular fibrillation develops in 0-2% (mostly children) 1
In one prospective study, 11% of initially asymptomatic patients developed arrhythmic events over a median follow-up of 67 months, with potentially life-threatening arrhythmias in 17 of these patients 1
Diagnostic Pitfalls
- WPW pattern on ECG may mimic pseudo diaphragmatic (inferior) myocardial infarction 6
- Intermittent pre-excitation can make diagnosis challenging
- Pre-excited atrial fibrillation may be misdiagnosed, leading to inappropriate treatment that could induce ventricular fibrillation 3
Early recognition of WPW syndrome is crucial, as appropriate risk stratification and treatment can significantly reduce morbidity and mortality from life-threatening arrhythmias.