(TMZ) Sylvester Stallone's son, Sage Stallone, died from a heart attack ... and no drugs were found in his system ... TMZ has learned.The L.A. County Coroner has determined Sage died from natural causes. As for why he had a heart attack, we're told there was evidence of heart disease.
A source connected with the Coroner tells TMZ ... it was "unusual" for a person Sage's age -- 36 -- to have such advanced coronary problems, but that's what killed him.
Sage's body was found July 13, but he may have been dead days earlier. more on this story
