The ECG shown here is from a 68 year old female with Ebstein’s anomaly in which there is downward displacement of a malformed tricuspid valve into the right ventricle and frequently an atrial septal defect. The ECG shows ventricular pre-excitation with a negative delta wave in lead aVR and a positive delta wave in leads 1, aVL V5 and V6. This results in a QRS complex that simulates left bundle branch block with left axis deviation and localizes the bypass tract to the right lateral region of the AV ring, This is the typical location of the bypass tract in the 5-10% of patients with Ebstein’s anomaly who also have WPW.