Abstract

Two newborn babies with an intact atrial septum are described. In one, the two components of the atrial septum appeared to have become fused after relatively normal initial development; the left side of this heart was hypoplastic. In the other baby the formation of the atrial septum appeared to have been completely anomalous; this heart showed mitral atresia, absence of the left ventricle, and transposition of the great vessels. There was also pulmonary lymphangiectasis in the second case, and it is suggested that this was due to the cardiac malformation obstructing pulmonary venous drainage.