The identification of a WPW impose to evaluate the potential risk of sudden cardiac death. The risk depends on the duration of the refractory period of the accessory pathway. If the preexcitation disappears when the patient is stressed on a treadmill, there is no risk of sudden death. If it does not, an electrophysiological study will have to be performed to measure the refractory period of the accessory pathway. If a risk of sudden death is present (refractory period < 220 ms), the accessory pathway has to be ablated using radiofrequency.