I don't think so. There was a "molten pit" reference or two in the RotJ novel, which has certain implications regarding the screenplay. But it wasn't in the movie as presented. I don't know what early Lucas's or popular opinion was on the origin of Vader's breathing problems. The only contemporary SW material I have is some Mad and Cracked reprints, and they probably just chalk it up to asthma.

Here's a great line from the SW novel:

"How," he asked slowly, "did my father die?"

Kenobi hesitated, and Luke sensed that the old man had no wish to talk about this particular matter. Unlike Owen Lars, however, Kenobi was unable to take refuge in a comfortable lie.

"He was betrayed and murdered," Kenobi declared solemnly, "by a very young Jedi named Darth Vader."

I actually like Kenobi as a conniving old bastard -- I think it fits better with the theme of youthful rebellion -- but something about this line tickled me. I suppose true believers would insist that Obi-wan's lie was uncomfortable, so it all fits together just like it was planned to.