Emergence of bidirectional accessory pathway conduction in adulthood.

A 30-year-old woman presented with tachycardiomyopathy due to atrial flutter-fibrillation and underwent radiofrequency ablation of the AV node and VVIR pacemaker implantation. There was no evidence of any accessory pathway (AP) conduction during the AV nodal ablation or during chronic ventricular pacing. One year later, she had a transient preexcited tachycardia. A year after this, her ECG showed 1:1 AV conduction with preexcitation. Electrophysiologic study revealed a left lateral AP with anterograde and retrograde refractory periods of 280 and 240 msec, respectively. Successful radiofrequency ablation of the AP was performed. This case highlights a unique emergence of an AP in adult life.