Occurrence of intermittent Wolff-Parkinson-White syndrome during intravenous sedation

Patients with intermittent Wolff-Parkinson-White (WPW) syndrome, defined as intermittent loss of the delta waves, can show occasional conduction through the accessory pathway. WPW syndrome often causes paroxysmal supraventricular tachycardia or atrial fibrillation. However, it may be difficult to identify the abnormalities preoperatively because of their only intermittent occurrence. We report a case in which exogenously administered epinephrine and an autonomic imbalance may have precipitated the abrupt occurrence and disappearance of the delta waves.