The diagnosis and treatment of complete anomalous pulmonary venous drainage.

Anomalous pulmonary venous drainage, expressed in the simplest of terms, means that pulmonary veins fail to enter the left auricle. If one or two pulmonary veins fail to enter the left side of the heart there may be no outward signs of cardiac disability and the patient leads a relatively normal life. Even if one half of the oxygenated blood enters directly or by venous channels into the right auricle there may be very few symptoms. However, more than half the venous drainage from the lungs entering the right side of the heart will constitute some disability, and total anomalous pulmonary venous drainage in which no pulmonary veins enter the left atrium is usually accompanied by a poor prognosis and death in infancy. In order to survive there must be an intracardiac communication, usually intra-atrial, in the form of a patent foramen ovale or intra-auricular septal defect. The intracardiac shunt is obviously from right to left, and survival beyond infancy will depend largely on the size of this communication between the two auricles. An embryological study of this lesion is interesting since it concerns not only the rudimentary systemic venous return but also the venous return of the lungs. In early developmental stages, the lungs, which are considered to develop by division of the foregut, are drained by umbilico-vitelline veins which in turn enter the systemic pre-cardinal and post-cardinal veins. The post-cardinal veins unite to form the inferior vena cava and the pre-cardinal veins the right superior vena cava. While these systemic channels are becoming delineated into the normal situation, a channel from the sinal atrial region of the primitive heart tube outpouches to become the left atrium which grows towards the lungs and develops a communication which eventually forms the normal pulmonary venous drainage. If one were to postulate that, at the stage at which the pre-cardinal veins are busy disappearing and the