How do i get an open heart surgery scar to disappear?

You can't: Scars tend to fade with time, but never really go away. Some areas of the body tend to scar worse than others. Sternal wounds tend to scar a bit more than places like the face or neck. You can try things like silicone sheeting or steroid injections if your scar is hypertrophic.

Not possible: A plastic surgeon can sometimes revise a skin wound in order to make it less apparent.