Ventricular tachycardia Pre-excited atrial fibrillation Antidromic atrioventricular re-entrant tachycardia Aberrant conduction during atrial fibrillation Answer Case resolution The ECG shows a wide QRS complex tachycardia with irregular RR intervals, delta waves and no P waves, findings suggestive of Wolff-Parkinson-White syndrome with pre-excited atrial fibrillation (AF) (figure 1). Pre-excited AF should be suspected in the presence of a wide and irregular QRS complex tachycardia, especially with an unusually high frequency (compared with non- excited AF); an initial slurred upstroke or downstroke of the QRS (epicardial activation); QRS complexes exhibiting varying morphology (varying degrees of fusion due to activation over both the accessory pathway (AP) and the atrioventricular (AV) node); or positive precordial concordance (entirely positive R wave in all precordial leads with no R/S complexes).1 All these findings can be seen in this case (figure 2). Management of asymptomatic arrhythmias: a European heart rhythm association (EHRA) consensus document, endorsed by the heart failure association (HFA), heart rhythm Society (HRS), Asia Pacific heart rhythm Society (APHRS), cardiac arrhythmia Society of southern Africa (CASSA), and Latin America heart rhythm Society (LAHRS).