Do you call heads up in this situation?

Jbrochu has it right. Head's up is a game of cat and mouse. I would look for a spot to drop the hammer on this guy. Sometimes that spot never comes, in which case you eventually are pushing to take blinds or double up. Lot's of ways to win when head's up. Calling and hoping for a coin flip is not one of them that is going to get you consistent positive $EV results.