This one book on famous deaths said Gambino died on the floor after having a heart attack just as the OP said. It said he decided to make some spaghetti while watching the game but dropped dead in his basement.

Of course the same book said Gambino was Vito Genovese's underboss so that should tell you what the author knew about Gambino and how little fact checking he must of did. .

https://books.google.com/books?id=oKPy-RAh3O8C&pg=PA6