1st- A heart shot is possible with that shot. I did it last year on a doe on the opener.
A brain shot is possible from almost ANY angle.............That doesn' t make it a good idea.
Why would anyone shoot at a deer that is right under your stand?? It has to leave in some direction right?? Wait for it to wander out 10 yards and take a quartering away or broadside shot. It is very unlikely that a deer that is right under your stand will be able to escape without presenting a shot opportunity better then what you described........and if he does...........Oh well, that' s why they call it hunting and not killing.