Since the initialDelta is only used to prime the stack, I would instead call the argument "dv" and reassign to it in the while loop.  That way we only have one type of DeltaVisit (the active object) in scope and its less likely we'll use the wrong one.

Sometimes assigning to an argument is evil, and sometimes its good.  I think this sort of algorithm is one of those times where its good to reuse the argument variable.