Transition of orthodromic tachycardia into atrioventricular nodal tachycardia during radiofrequency ablation of an accessory pathway

We report a patient with Wolff-Parkinson-White syndrome, in whom orthodromic atrioventricular reciprocating tachycardia directly passed over to atrioventricular nodal re-entrant tachycardia during radiofrequency ablation of the accessory pathway. After the accessory pathway ablation, there were no tachycardia recurrences.