I have seen news about millions of heart attack victims make it to a hospital and still be alive. Yes, a minority of heart attack victims die very quickly as happened to my brother.
Break in the main Aorta? Very rare to make it to hospital surgery in time. Once the blood pressure has dropped dangerously low, the brain dies quickly from lack of oxygen circulating to the brain.
Many present with chest and back pain. If unstable when they arrive, vast majority don’t make it. If reasonably healthy, and stable, about 85-90% survive if cardiac surgery available for dissections. Most cardiac arrhythmia patients die suddenly, unless if cpr and defibrillators around. Ventricular arrhythmia very lethal very fast.