Atrial aneurysms occur in the walls of the heart's upper chambers, which are called atria. When an atrial aneurysm is present, a sac forms that bulges or balloons out of an atria. An atrial septal aneurysm, is an aneurysm that occurs in the wall between the two chambers. These aneurysms often fail to produce any symptoms, despite the fact that their presence constitutes a significant danger. Was this term used by your physician, or was this self diagnosed?
I would see a cardiologist to just make sure, an aneurysmal interatrial septum should be looked into as it is a bulge in the heart wall, I am surprised your doctor did not refer you to a specialist.