The accessory pathway is a thin filamentous tissue resulting from failure of atria and ventricles to completely separate; multiple pathways may exist in approximately 10% of patients. Associated congenital anomalies are seen in 7%-20% of patients, and about 10% of patients with Ebstein anomaly possess an aberrant pathway.
The accessory pathway predisposes patients to various supraventricular arrhythmias including atrioventricular reentrant tachycardia (AVRT), atrial fibrillation (AF), and atrial flutter. Extremely rapid ventricular rates sometimes seen in this setting can result in hemodynamic instability and degeneration to ventricular fibrillation.
Symptoms may include palpitations and/or syncope, chest pain, and sudden cardiac arrest, although most patients remain asymptomatic with incidental finding of the characteristic ECG pattern.
I45.6 – Pre-excitation syndrome
74390002 – Wolff-Parkinson-White pattern
Differential Diagnosis & Pitfalls
- Lown-Ganong-Levine syndrome – Short PR interval on ECG but normal QRS complexes.
- Ectopic atrial rhythm
- Myocardial infarction – Negative delta wave can mimic a Q wave of myocardial infarction.
- Frequent premature ventricular beats – Infrequently occurring alternate WPW or persistent WPW beats may be misdiagnosed as frequent premature ventricular contractions or idioventricular rhythm.
- Hypertrophic cardiomyopathy – Can also cause widened QRS and short PR. Look for typical systolic murmur on examination.