The pathway paradox: From syncope to tachycardia in Wolff-Parkinson-White syndrome

Abstract: A 53-year-old male with Wolff-Parkinson-White (WPW) syndrome presented with syncope due to complete heart block (CHB) and underwent dual-chamber pacemaker (DCPM) implantation. The patient developed incessant broad complex tachycardia post-implantation, initially diagnosed as endless loop tachycardia (ELT), which later transitioned to antidromic tachycardia. Electrophysiological study revealed an accessory pathway (AP), which was successfully ablated. The ablation unmasked a markedly prolonged HV interval. APs should not be relied upon as a consistent source of AV conduction, and they can mask underlying His-Purkinje disease. Additionally, APs can predispose to ELT and require ablation to prevent recurrent tachycardia.