What would happen, I wonder, if one or more states decided to change their constitutions to define persons to be protected under their laws as all human beings possessing a heartbeat and/or a brainwave?    If Virginia can explicitly exclude the unborn from personhood, surely other states can do the opposite.  

Just as same-sex marriage was not specified within the U.S. Constitution, so is the definition of what makes a person not specified.  When several states began to assert that they had the right to determine what defines marriage within their borders,  which was upheld by SCOTUS,  so, it seems to me, that a state could do the same thing with personhood.