The NavX system was used to guide mapping and successful ablation of a reciprocating antidromic tachycardia involving anterograde conduction over a nodo-fascicular fibre and retrograde conduction over the His bundle and AV node. This novel mapping system allowed visualization of the lower insertion site of the nodo-fascicular accessory pathway approximately 1.5-2 cm away from the tricuspid annulus in a three-dimensional reconstruction of the right atrium and right ventricle.