Can I wear a back brace without it harming my pacemaker?
It's not going to hurt your pacemaker (nothing will that doesn't kill you first) but, depending on the style and coverage, any straps may be uncomfortable.
Anything that will not put pressure on the pacemaker's area should be fine.
You know you're wired when...
You can feel your fingers and toes again.
It's much better to live with a pacemaker than to risk your life without one.