In a 6-year-old child patient, transthoracic echocardiography revealed a large saccular structure (with anechogenic content) in the left atrium, near the fossa ovalis, and diagnosis of the left atrial septal pouch was made. The left atrial septal pouch is a kangaroo pouch-like structure on the left side of the interatrial septum, opened into the left atrial cavity without a connection between the left and right atria. It occurs when the foramen ovale is absent but the septum primum and septum secundum are only partially fused. The left atrial septal pouch is believed to be present in 47% of population. In many cases, the pocket on the atrial septum is small and it could not be detected by transthoracic echocardiography. Our description is uncommon because we diagnosed a very large septal pouch. Based on our knowledge, this is the youngest reported case of the left atrial septal pouch and the longest follow-up described in this type of congenital heart malformation.
Keywords: LASP; Left atrial septal pouch; cardiac mass; children; echocardiography; interatrial septum.