There are no stupid questions when you are looking for knowledge.
You can not survive without your heart. It pumps the blood throughout the entire body.
During a surgery like a heart transplant, they connect the body to a machine that "mimicks" the same function as the heart while the actual transplant is occuring.
If a person's heart stops from a heart attack
or something, the longer it takes to revive the person, the higher chance there is for brain damage
and eventually death to occur. Let's say a person is revived after 45 minutes of CPR...chances are there will be little to no brain activity left because of the damage that occured while the heart was not beating. That's why it's so important to act fast when a person is having a heart attack.