OBJECTIVES: This study sought to investigate the prevalence of atrial septal aneurysms in the paediatric population and to define coexisting abnormalities and their incidence.BACKGROUND: Few papers refer to the prevalence of atrial septal aneurysms in childhood.METHODS: We enrolled a total of 4522 children aged more than 12 months who underwent a transthoracic echocardiography. Atrial septal aneurysm was defined as a protrusion of the interatrial septum or part of it >15 mm beyond the plane of the atrial septum or phasic excursion of the interatrial septum during the cardiorespiratory cycle of at least 15 mm in total amplitude and a diameter of the base of the aneurysm of at least 15 mm.RESULTS: Atrial septal aneurysms were found in 47 children (1.04%). They involved almost the entire septum in 14 patients (28.89%) and were limited to the fossa ovalis in 33 (71.11%). An atrial septal aneurysm was an isolated structural defect in 17 (35.56%). In 30 (64.44%) patients, it was associated with interatrial shunting - atrial septal defect and patent foramen ovale. At the echo follow-up after a year, no changes were recorded.CONCLUSIONS: Prevalence of atrial septal aneurysms is almost 1%. The most common abnormalities associated are interatrial shunts, that is, a patent foramen ovale and an atrial septal defect. From a medical point of view, it is suggested that no action is to be taken during childhood, as a child with an atrial septal aneurysm is not at increased risk compared with a child without one. Follow-up is scheduled on an individual basis.