If underlying cause of cardiomegaly is resolved, does heart return to normal?
This is somewhat difficult to answer based on the limited info but, yes, to a degree. Just like any muscle that has grown to larger than normal dimentions, once it is no longer worked so hard, the muscle gradually reduces in size to something more suited to the work it is now required to do. As a quick example, if you work out with weights to build your biceps and they get larger, but then stop working those muscles later on, they will gradually reduce in size. The question as to will the heart get back to normal, well, thats difficult to say, it may not get all the way back to its original size, but hypertrophy of the heart muscle reduces its pumping effectiveness and reducing its size by any measure is an improvement. I hope this has been helpful.