"Remember last year?" he finally asked. "Remember how I had to...give up...some of my life-force to save Jimmy?"
"Of course. I was terrified, seeing that machine suck away...whatever it was...years of your life, your life-force, however you want to word it."
"And then, about a month later?"
"Deathstroke," she immediately replied.
He nodded in affirmation. "Deathstroke."
"What does...?"
He cut her off before she could ask the question. "Dr. Klein has a theory. He thinks that those two events, especially so close together, put a strain on my body. Well, more of a strain than he suspected at the time. That strain, he believes, weakened my heart."
Aha! I KNEW his battle with Deathstroke was the culprit -- at least partly.
"Unless I receive a heart transplant, I'll die."

Oh no... Who can give Superman a heart transplant? I just hope he doesn't die... I know you warned us, but, oh man... OK, let me think of a way out of this... my best hope would be a clone of Clark, like in Vatman -- even though, technically, a Clark/Superman would have to die.

Even worse, yet possibly more viable, would be an alt-Clark...sacrificing himself because he can't find his Lois and has no will to live...

OK, I really hope it doesn't go that dark...
And I really hope there's some light at the end of this seemingly dark, dark tunnel...