Accessory Pathway in Ebstein's Anomaly: Absence of Evidence Is Not Evidence of Absence.

Electrocardiography has certainly great merit and is almost abnormal in most patients with Ebstein's anomaly. Incomplete or complete right bundle brunch block (RBBB) is seen in almost half of these patients. The absence of the expected RBBB during sinus rhythm in a patient with Ebstein's anomaly is a useful clue of pre-excitation in these patients.