Dreaded arrhythmia in association with WPW syndrome (Wolff-Parkinson-White syndrome) is: 1. Orthodromic atrioventricular re-entrant tachycardia (Orthodromic AVRT) 2. Antidromic atrioventricular re-entrant tachycardia (Antidromic AVRT) 3. Atrial fibrillation 4.