system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why can't we revive a deceased person by making their heart beat again (e.g. by using an artificial heart)?
gpt
Sometimes we can. People have their hearts restarted or put on a bypass machine until they can heal or have surgery. Usually you have to be lucky enough to be in a hospital when that happens however. If your heart stops your brain is going to have about 3 mins before brain damage sets in. After 9 minutes the brain is essentially dead and revival isn't possible.