RESUMEN
Pre-excitation syndrome (PES) is a congenital abnormality in which there is conduction through accessory pathway in addition to atrioventricular (AV) node between the atria and the ventricles. Conduction through accessory pathway is without any delay and; hence, results in early excitation of ventricles. This dual connection provides substrate for atrioventricular reciprocating tachycardia (AVRT), a type of supra-ventricular tachycardia. Wolf-Parkinson-White (WPW) syndrome is the commonest form of PES. PES with third degree AV block or complete heart block (CHB) is a rare association. We report here a case of 37-year male with surface ECG findings consistent with PES who presented with syncope. The combination of pre-excitation on ECG with syncope usually draws attention towards tachy-arrhythmias. However, ECG monitoring revealed CHB with intermittent conduction through accessory pathway. It highlights the critical evaluation of PES patients with syncope because therapeutic strategy is entirely different. This case was managed with dual chamber pacemaker implantation instead of accessory pathway ablation.