It won't.

Simply.

It can't.

You can engineer the most skookum circuit on earth out of the most magically wonderful biomaterials but you can't engineer people that won't reject them. If you gave me a kidney I'd spend the rest of my life hopped up on all sorts of immunosuppressants so that I could keep it alive, functional and in my body. That's a 1:1 replacement, blood type and all biomarkers matching perfectly, and the body still knows it ain't natural. There's a reason we autotransfuse over blood transfusion: even though blood is simple compared to a kidney, and even though it only lasts about three months, our own stuff is our own stuff and other people's stuff is THE INVADER.

You've got a pacemaker. There's stuff you can't do because of it, and there's regularly scheduled maintenance that is a fundamental part of your life. It's a lot less than it was even ten years ago, and your quality of life with that pacemaker kicks the shit out of your quality of life without, but it still isn't as good as my quality of life. That's not really the pacemaker's fault. It could be 100% certified alien technology and it'd still have to touch your heart to do its job, and your heart doesn't like to be touched.

You're young. That won't be your last pacemaker. The next one is going to be even more awesome. But it's still going to have to touch your heart, and your heart is going to be a little less responsive because it will have built up plaques and biofilms and scar tissue against pacemakers. And it will still not be quite as awesome as a healthy heart with no pacemaker because an implant is a compromise between added functionality and added damage.

The damage is never going away. It's not a problem of technology, it's a problem of anatomy and biology and even if we were to Man After Man our way into some T-1000 transhumanist future all we'd do is shift the playing field to T-1000-opportunistic microbes.