When a healthy person dies, their heart can still be used. The patient's diseased heart is removed and the healthy donor heart is then attached. The operation is complicated because so many blood vessels have to be detached and re-attached. While the operation is taking place, the patient is connected to a heart-lung machine that keeps their blood circulating. After the operation, there is still a risk that the patient's systems may reject the new heart.
Tissue types have to be perfectly matched in order for the transplant to be successful.
As a result, the number of transplants performed is quite low. Many patients do not survive the wait for a donor heart. Medical scientists have developed an artificial heart that may be used to keep the patient alive for a short time until a donor heart becomes available. Scientists have also experimented with transplanting an animal heart into a human. A team of medical scientists from Loma Linda University in California performed the operation.