My father survived this. No brain damage. Lived a few more years, until 74. The heart wasn't pumping at normal rates because of damage. Do to hip problems (arthritis) also had problems walking. Eventually Developed a blood clot in a leg. Initially survived the blood clot. But the medication given to thin out the blood clot caused bleeding on his liver. Somehow the Hospital missed the bleeding until it was too late. The operating room was also busy (Canada), so no intervention could be performed. Wasn't allowed to see him because of covid rules. Possibly been able to advocate for him if I was in his room, and saw his worsening condition.

They can save your life in a hospital, but just as easily kill you by mistake or side effect of whatever intervention they are doing. Also, walking (or being able to walk) is very important for longevity.

But the speed of the first response of the cardiac arrest is what matters. Since the brain is without oxygen. Assuming the person makes it to a hospital alive, they'll cool off the body to prevent brain damage. For every minute you survive, your odds get better.