*To answer your question, Laura - I think that the main difference between Rachel's heart and other right isomerism cases, is the aorta. Usually it has two branches - one main branch carries blood to the body and the other carries blood to the lungs. In her case, the aorta is one branch with tiny arteries leading off of the aorta. (plus it is not in the usual position)
First, what a normal heart looks like....
And now, here's Rachel's heart:
You can see a few notes we jotted down later - as well as a food stain - we carried it around alot in those early days to help us explain her heart's anatomy to people.