Intracardiac total anomalous pulmonary venous return or septum primum malposition? Complete repair in left atrial isomerism.

Total anomalous pulmonary venous return due to septum primum malposition is a poorly understood condition despite being very common in left atrial isomerism or polysplenia syndrome. Due to the leftward displacement of the septum primum, either the two right pulmonary veins or all four pulmonary veins can drain abnormally into the right atrium, despite their correct position. In other words, the four pulmonary veins (or the two right pulmonary veins), looking from outside the heart, return at the back of the atrium in the normal position. Nevertheless, from the inside of the heart, two or all four pulmonary veins drain into the right atrium due to the leftward displacement of the septum primum. As an example, we report a 5-month-old patient with severe malposition of the septum primum and consequent total anomalous pulmonary venous drainage into the right atrium. The patient underwent surgical correction with resection of the malpositioned septum primum and reconstruction of a normal interatrial septation with a pericardial patch.