So, it usually stands for "intact ventricular septum". Often it's mentioned with PA. So it would read PA/IVS. Is that what you are referring to? In this case, it means the ventricular septum is intact or doesn't have a hole in it. It also can mean interventricular septum. This is part of the heart. It's part of the conduction system and works with the mechanical function of both ventricles.
If you gave more info, I might be able to help more.