This study aimed to evaluate the clinical features of patients with septum primum malposition, imaging tools used for diagnosis, and their effects on the surgical approach.

Patients diagnosed with septum primum malposition in our paediatric cardiac centre between 1 January, 2015 and 1 January, 2019 were included in the study. In all patients, the age, reason for admission, transthoracic echocardiography, cardiac multidetector CT angiography findings, and subsequent surgical data were evaluated.

Fifteen patients were diagnosed with septum primum malposition during the study period. The median age was 12 months (2 months–10 years). Six patients were left isomeric, and the rest were situs solitus; 80% of the patients (n = 12) had additional secundum atrial septal defect. There was cardiac pathology in 46% of the patients (n = 7) in addition to the abnormal pulmonary venous drainage, ventricular septal defect (n = 3), left ventricularhypoplasia (n = 2), cortriatriatum sinister (n = 2), double outlet right ventricle (n = 1), and atrioventricular septal defect (n = 1). There was bilateral superior caval vein in three patients, right-sided superior caval vein in 11 patients, and left-sided superior caval vein in one patient. All three patients with total abnormal pulmonary venous drainage were left atrial isomeric. There were differences between the results of transthoracic echocardiography and CT angiographies in two patients. The surgical strategy was changed in three patients after the preoperative diagnosis of septum primum malposition.

Septum primum malposition should be kept in mind during the imaging of complex CHDs specifically during the segmental analysis of the pathologies with heterotaxy syndromes; it should be differentiated from other aetiologies of abnormal pulmonary venous drainage as accurate diagnosis would facilitate the ideal surgery in these complex pathologies requiring a detailed preoperative preparation.