[Wolff-Parkinson-White syndrome in Ebstein's anomaly].

The abnormal development of the tricuspid valve in patients with Ebstein's anomaly results in several activation abnormalities including delayed intraatrial conduction, right bundle branch block, and ventricular preexcitation. In the present review, the aim was to define the ECG characteristics before and after ablation of an accessory A-V pathway in patients with Ebstein's anomaly. In a series of 224 patients studied at the Instituto Nacional de Cardiologia "Ignacio Chávez", Sixty-four patients (28%) had documented tachycardia. Thirty-three patients with recurrent tachycardia were found to have a single right-sided AP that was successfully ablated. Only 21 of 33 patients (62%), had typical of ECG pattern of preexcitation. In addition, none of the patients had an ECG pattern of RBBB during sinus rhythm. Radiofrequency catheter ablation resulted in appearance of RBBB in 94% patients. The absence of RBBB in patients with Ebstein's anomaly and recurrent tachycardia had a 98% sensitivity and 92% specificity for the diagnosis of an AP. One third of patients with Ebstein's anomaly and symptomatic tachyarrhythmias have minimal or absent ECG features of ventricular preexcitation. In these patients, the absence of RBBB pattern is a strong predictor of an AP.