Ventricular preexcitation following catheter ablation of the His bundle in concealed WPW syndrome.

Catheter ablation of the His bundle is reported in a patient with drug-refractory supraventricular tachycardia meeting standard criteria of concealed WPW syndrome (conduction of the accessory atrioventricular pathway in retrograde direction only). After successful ablation of the His bundle, anterograde conduction along the accessory pathway, to our surprise, became apparent. During twelve months of follow-up, the patient was free of the tachycardia recurrences off antiarrhythmic drugs. While the clinical problem has been solved, the patient may--in case he should develop atrial fibrillation--present with rapid anterograde conduction via the accessory pathway. Based on this experience, better electrophysiologic protocols are needed to evaluate anterograde accessory pathway conduction properties in 'concealed' WPW syndrome, thus permitting one better to decide whether and which site of ablation should be chosen in drug-refractory cases.