RESUMO
Radiofrequency ablation is the interventional therapy of choice for the definitive cure of patients with tachycardias facilitated by accessory pathways. Ablation of an accessory pathway at sites close to the His bundle is inevitably associated with an increased risk of causing complete atrioventricular block. Here we describe the case of a patient with pre-excitation syndrome and episodes of supraventricular tachycardia, in whom an electrophysiological study identified an accessory pathway so close to the His bundle that discrete sites between the pathway and the His bundle were extremely difficult to find. After a first, unsuccessful attempt at ablation the patient developed incessant supraventricular tachycardia. The accessory pathway was successfully ablated in a second session using high power radiofrequency current, although this entailed a great increase in the risk of causing complete atrioventricular block.