What is the definition or description of: atrial septal aneurysm?

Floppy septum: The atrial septum devides the right atrium (upper heart chamber) from the left. During developement in the womb, there is a large opening in this wall which closes soon after birth. The closure can be floppy or redundent, and may be referred to as aneurysm. This is benign and not the type of aneurysm that needs repair or is at risk to rupture.

Bulge inside heart: The atrial septum is similar to a wall separating t2 of the 4 chambers of the heart. An aneurysm is an enlargement or a bulge in that wall. It may or may not cause symptoms depending on how large it is. A small one may cause no trouble, but a large one might cause problems.