Hidden Conduction, Overt Risk: A Case of Wolff-Parkinson-White Syndrome Unmasked.

Wolff-Parkinson-White syndrome, though previously diagnosed and without prior arrhythmic events, may remain clinically quiescent until atrial fibrillation with rapid antegrade conduction over an accessory pathway precipitates a potentially life threatening arrhythmia. We present a teaching case of a 46-year-old man who developed abrupt onset wide-complex tachycardia with ventricular rates exceeding 280 beats per minute on postoperative day three following thoracic surgery. Electrocardiography demonstrated an irregularly irregular rhythm with marked beat-to beat QRS variability and very short RR intervals, favoring atrial fibrillation with preexcitation rather than ventricular tachycardia or rate-related aberrancy. This case is used to illustrate key electrocardiographic features that distinguish pre-excited atrial fibrillation from other causes of wide-complex tachycardia and to review evidence based management principles in hemodynamically stable patients, including the selection of therapies that target accessory pathway conduction while avoiding atrioventricular nodal blockade.