The casino most likely didn't know he was having a heart attack. If they did know, he would have been dragged out of the casino so that they will not have any responsibility for his death. Incidents like this don't happen often but I do think casinos have clinics to respond to such incidents.
If the guy was sitting looking at the table for a minute, without moving, the dealer should've asked if he's ok. Imagine you work at a restaurant and one guy looks like he's asleep at the table. You want to wake him up and ask if he's ok, as you don't want him to vomit there, or fall down and cut his head. I've seen this happen when a drunk guy wasn't feeling too well at the pub and went to the bathroom probably to puke. He came out all dizzy and cut his forehead. There was a lot of blood and they had to call an ambulance.
We're not machines at work and we shouldn't act like ones. IMO it was the dealer's fault.