A heart transplant needs to be carried out as soon as possible after a donor heart becomes available.
The procedure is performed under general anaesthetic, where you're asleep. While it's carried out, a heart-lung bypass machine will be used to keep your blood circulating with oxygen-rich blood.
A cut is made in the middle of the chest. Your own heart is then removed, and the donor heart is connected to the main arteries and veins. The new heart should then begin beating normally.