Aortic atresia associated with the right atrial isomeric form of situs ambiguus.

A case is described which had the right isomeric form of situs ambiguus. A common atrial chamber was found with bilateral appendages of right morphology and bilateral superior venae cavae entered the chamber. It communicated through a common atrioventricular valve with a sole ventricular chamber of morphologically right ventricular type which gave rise anteriorly to the pulmonary trunk. There was aortic atresia, the coronary arteries and head and arm arteries being fed in retrograde fashion by a ductus arteriosus. It is emphasized that while aortic atresia is exceedingly rare in situs ambiguus of right isomeric type, it can exist. The case also exhibits the advantages to be gained from categorizing atrial situs on the basis of atrial morphology.