Pre-excitation with syncope: a false lead?

An 18-year-old girl with pre-excitation presented with a history of recurrent syncope preceded by palpitation. The accessory pathway, which had a relatively long antegrade effective refractory period of 340 ms, was mapped and successfully ablated in the left lateral region. However, after ablation, she had reproducible sustained polymorphic ventricular tachycardia, which was found to be the cause of her syncope. Thus, alternate mechanisms of tachycardia need to be considered in patients with pre-excitation when the presentation is atypical.