In a Las Vegas casino, that's where. According to a recent (unlinkable) article in The Wall Street Journal, around 1,800 people, including gamblers and hotel employees, have had their heartbeats restarted in Vegas casinos over the last nine years. It all began when a Vegas-based paramedic named Richard Hardman had the idea for a life-saving program. He noticed how often he and other rescuers were called in to treat heart attack victims and how there was always a security guard standing there, looking helpless and with no idea what to do.
Hardman went to executives of the Boyd Group, a company that owns many Vegas hotels, and proposed that they not only have defibrillators handy but that security guards and other staffers be trained how to use them. This was a much more involved process than it sounds because it involved studying the problem and compiling data on it and then the concerns of attorneys had to be addressed and local "good samaritan" laws had to be changed. Eventually, a pilot program was started and the first time it saved someone's life, other casinos saw the publicity and wanted in.
Across the country, among people who suffer cardiac arrest in public places, the survival rate is under 10%. In Vegas hotels, it's 53% and if the defibrillators are applied within three minutes of the collapse, that number goes up to 74%. Today in most casinos, there are enough defibrillators strategically dispersed — and enough people qualified to use them — that three minutes is quite possible.
So that's the answer to the question I asked earlier. Unfortunately, we do not have stats on how many people had heart attacks just because they were in Vegas casinos. But between the smoke and the buffets and the Blackjack dealers who can draw five cards to a 21 and beat your twenty, I'm guessing the number is high.