Common situation, looking for comments on river

[TiltsMcFabulous]

Preflop: Hero is MP2 with Q[img]/images/graemlins/club.gif[/img], Q[img]/images/graemlins/diamond.gif[/img].
<font color="#666666">All folds, MP1 raises, Hero reraises, everyone else folds</font>.

Flop: 5[img]/images/graemlins/heart.gif[/img], J[img]/images/graemlins/club.gif[/img], 4[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
MP1 checks, Hero bets, MP1 calls

Turn: 5[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
MP1 checks, Hero bets, MP1 calls

River: A[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
MP1 bets, Hero ...?


What should Hero do?

~ Tilts