Ventricular septal defect with mobile tricuspid valve pouch mimicking tetralogy of Fallot.

A newborn with partial deletion of the long arm of chromosome six presented with cyanosis at birth. Initial studies suggested the diagnosis of tetralogy of Fallot and the infant underwent a Waterston shunt procedure with subsequent clinical improvement. The infant subsequently died of unrelated causes. Autopsy revealed a ventricular septal defect and a dysplastic pouchlike structure related to an anomalous tricuspid valve leaflet which obstructed right ventricular outflow. Classical anatomic findings of tetralogy of Fallot were absent. Clinical and echocardiographic findings that would be expected to aid early diagnosis of future cases are presented.