Myocardial fibers extending from the atrium to the ipsilateral ventricle across the mitral or tricuspid annulus (accessory pathway) pre-excite the ventricle.
WPW syndrome is restricted to symptomatic patients with a typical ECG abnormality; WPW pattern signifies an asymptomatic patient with typical ECG abnormalities.
Patients often present with AV re-entrant tachycardia, less commonly atrial fibrillation, and, rarely, sudden cardiac death.
Asymptomatic patients, except for those with specialized jobs (e.g., airline pilot, school bus driver), should not be treated but can be monitored for symptoms.
Minimally symptomatic patients may be treated with catheter ablation or medical therapy, either on a routine basis or as needed during symptomatic episodes.
Symptomatic patients usually undergo catheter ablation as first-line therapy.
Catheter ablation is highly effective with low risk and can be used either as initial therapy or for patients experiencing side effects or arrhythmia recurrences despite medical treatment.
Occurs when one or more strands of myocardial fibers capable of conducting electrical impulses (known as accessory pathways [APs] or bypass tracts) connect the atrium to the ipsilateral ventricle across the mitral or tricuspid annulus.  Conduction from the atrium reaches the adjacent ventricle earlier via the AP, and a part of the ventricle is pre-excited. The term "Wolff-Parkinson-White (WPW) syndrome" is restricted to symptomatic patients with a typical ECG abnormality, whereas the term "WPW pattern" signifies an asymptomatic patient with typical ECG abnormalities. 
Cardiac Electrophysiology Fellowship Program
Assistant Professor of Medicine
Perelman School of Medicine
University of Pennsylvania
DF declares that he has no competing interests.
Dr David Frankel would like to gratefully acknowledge Dr Mithilesh K. Das and Dr Douglas P. Zipes, the previous contributors to this monograph. MKD and DPZ declare that they have no competing interests.
Associate Professor of Medicine
Director of Electrophysiology
Johns Hopkins University School of Medicine
JEM declares that he has no competing interests.
The St. Luke's-Roosevelt Hospital Center
SM declares that he has no competing interests.
Cardiology Specialist Registrar
The James Cook University Hospital
AT declares that he has no competing interests.
Department of Medicine
Division of Cardiology
University of Florida College of Medicine
SH declares that he has no competing interests.
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