Why can't hearts be restarted after natural death?

[schrod's dog]

If someone dies in a hospital a member of medical staff tries to brings their heart back to life, sometimes this works. Why if someone dies of nateral causes can't their heart be braught back to life after a while?

 

[hypatia]

When a heart stops beating, blood ceases to flow to the brain. The heart muscle cells are being starved of vital blood and oxygen and have been dieing sense the heart has stopped.
Heart muscle cells produce the electrical impulses that make our hearts beat. As more of these cells die, the impulses will starte to go out of sync. Making normal heart patterns impossible to maintain.
Even after a short period of time{say 20 minutes}, when blood is returned to a normal flow, the brain begins to swell. Blood has begun to clot, causing blockages body wide.
At this point, the other organs fail to function. So while they may be able to start the heart, the person would be living in a comatose/ vegetative state, only with the aid of machines, never regaining a quality of life.

 

[Dale]

My understanding is that it is all about time. Every cell requires a certain amount of energy in order to maintain its integrity, even without serving its normal function. Some cells (e.g. bone) are "built strong" so they only fall apart very slowly when they lose energy. Others cells (e.g. skeletal muscle) have a good amount of energy stored. But heart and brain cells do not. They have no reserves and are rather delicate, so they only last about 8 minutes or so without blood flow.

If someone dies in a hospital a member of the medical staff can get there in less than 1 minute, so the heart and brain cells are still alive and can be restored to normal function. But outside if it takes too long to get there then the cells in the heart and brain cells are dead and cannot be revived.