According to hbo.com, Renata died of natural causes (a stroke).
The look of -- what was it exactly -- victory? that swept across Tony's face as he was leaving Hesh's place (after unceremoniously/cruelly dropping off the money he owed) was revelatory in countless ways.
It showed the depth of his jealousy over Hesh's (outwardly) normal/peaceful life. In other words, he was revelling in Hesh's pain. When you consider that Hesh was someone that he once "loved like a father" this shows just how far Tony has sunk. He was "given a second chance at life" in the form of a near death experience, and he is squandering it by sinking deeper and deeper into a hell that is mostly of his own making.
I know some people are not crazy about this final mini-season, but I think David Chase is nothing short of a genius. Making Tony (and many other characters) even less sympathetic and likable to his/their most loyal fans? To me, that's an act of profound screenwriting courage. Everything is falling apart. No one is safe. And their collective desperation/envy/hatred/pettiness/selfishness/emotional ugliness is downright palpable. A "pretty" and/or "happy" ending was never even remotely possible for this group of murdering/thieving/lying characters, so Chase appears to be taking them all down, one by one, and not in a "blaze of glory."
-hopeful