An atrial septum indicates the wall that separates the right and left upper chambers of the heart has a bulge do to a weak tissue structure. If the aneurysm bursts, there will be blood flow between the chambers. Yes, it can burst, and if that occurs a patch can be attached to close the hole. No color flow means the wall continues to separate chambers.
Treatment would be to reduce and keep intra heart pressures as low as possible, and monitored for any progression.