Unmasked superoparaseptal pathway conduction due to atrial fibrillation in a patient with left ventricular dysfunction. Rapid recovery after successful radiofrequency ablation.

We report the case of a 56-year-old woman with newly diagnosed atrial fibrillation (AF) and severe left ventricular (LV) dysfunction caused by rapid conduction via an accessory pathway (AP), mimicking left bundle branch block, as the first clinical manifestation of Wolff-Parkinson-White (WPW) syndrome. Electrical cardioversion of the AF revealed a short PR interval and a delta wave, which was positive in leads I, II, aVL, and V2 and negative in lead V1 with a transition zone between V1 and V2. Radiofrequency catheter ablation of a superoparaseptal pathway was accompanied by rapid recovery from LV systolic dysfunction.