Retrograde fast pathway ablation with the EnSite NavX mapping system for slow-fast atrioventricular node reentrant tachycardia and a prolonged PR interval during sinus rhythm.

An 84-year-old male had experienced palpitations. He was transported to our hospital for treatment of palpitations. A 12-lead electrocardiogram (ECG) showed regular tachycardia with a wide QRS complex of 153 bpm, and the P wave was not clear. The ECG after the tachycardia stopped showed a sinus rhythm, and there was a prolonged PR interval of 312 ms and complete right bundle branch block. We recorded a prolonged AH interval (235 ms) in electrophysiology study (EPS). As for the St-A interval (185 ms) by consecutive pacing from the right ventricular apex, it was short in comparison with the anterograde conduction. As a result of detailed EPS, we diagnosed the tachycardia as slow-fast atrioventricular nodal reentrant tachycardia. The anterograde conduction depended on the slow pathway (SP), and the fast pathway (FP) was considered to have only retrograde conduction. It was thought that a complete atrioventricular block been caused by the SP ablation. Therefore we carried out FP ablation with three-dimensional computed tomography and the EnSite NavX mapping system (St. Jude Medical, St Paul, MN, USA), which was superior in space resolution power, and were able to effect a radical cure without complications.