Well that got dark really fast.... I don't think the karma from keeping the ovens gave him a bad heart though, could have been a bad ticker that he never got checked out, bad diet habits, stress from running a diner, no exercise, etc., etc.... I suspect that if they had kept those ovens or returned them the heart attack would have still happened.
Yeah, but it didn't happen really fast, like @bigjnyc says...after all, @Mac'nCheese said it took years.I thought they were going to say "dropped one on their foot...", but was so, so much darker that that.
And, @collin_, beware...you might have a heart attack or lose a toe or something as a result of keeping the watches. (;