I personally have never visited in major offline casino, so I do not have an idea or any personal experience on how prepared they are for unpredicted emergencies most especially in the health area, but then I agree with you, the casino is a place where people go to, spend much time sitting or moving around, some addicted gamblers can stay in the casino from morning till the evening, so I personally consider it common sense for such a business to have some medical stuffs, like a first aid box and possibly a medical staff on standby, just in case something comes up that has to do with health, yeah, health issues is something that does not happen frequently in gambling areas like in the casino, but then, it's not foolish for the casino to prepare for such emergencies as no one can tell when or where such a thing might happen.
Well, it's about laws and regulations in the end... here in Serbia, many companies have mandatory First Aid training. I have that every year once or twice, but it's just the first aid, that first reaction can save someone's life... but sometimes even the speed can't help. If anyone is destined to leave, that's it.
Having a full medical team ready for health emergencies is a big bonus wherever they are. But it's on the government to make some rules about it, and then casinos and all other big resorts will have it. When they earn millions they should be able to spend some money on this as well.