In the two decades since the performance of the first human heart transplant in December 1967, the procedure has changed from an experimental operation to an established an experimental operation to an established treatment for advanced heart disease.
In 1983, a major barrier to the success of transplantation- rejection of the donor organ by the patient-was overcome. The drug cyclosporine was introduced to suppress rejection of a donor heart or heart/lung by the patient's body. Cyclosporine and other medications to control refection have significantly improved the survival of transplant patients. About 80 percent of heart transplant patients survive 1 year or more. About 60 percent of heart/lung transplants live at least 1 year after surgery. Research is under way to develop even better ways to control transplant rejection and improve survival.
However, there is a shortage of donor hearts for transplantation. Many members of the public are not aware of the need of organ donation. Up to 30 percent of patients waiting for a transplant die, before a donor heart becomes available.
When a donor heart becomes available, tests are first done to find out the donor's blood type and whether there is evidence of infection, such as HIV, which causes AIDS. Matching the blood type helps to prevent the body from rejecting the donor heart. The size of the donor heart should be relatively proportional to the size of the recipient's body size, but an exact match is unnecessary. A transplantation can be carried out regardless of the difference between the recipient and donor in terms of gender and size.
The patient who is next on the waiting list and have the same blood type as the donor, this patient will be notified to come to the hospital in time for the heart transplantation. Once the heart is removed from the donor, it can only remain outside the body for 4 to 6 hours before the transplantation must be completed.
During the operation, the patient is placed on a heart/lung machine. This machine allows surgeons to bypass the blood flow to the heart and lungs. The machine pumps the blood throughout the rest of the body, removing carbon dioxide and replacing it with oxygen needed by body tissues. Doctors remove the patient's heart except for the back walls of the atria, the heart's upper chambers. The backs of the atria on the new heart are opened and the heart is sewn into place. A similar process is followed in heart/lung transplants, except doctors remove the heart and lung are attached first, followed by the heart.
Surgeons then connect the blood vessels and allow blood to flow through the heart and lungs. As the heart warms up, it begins beating. Sometimes, surgeons must start the heart with an electrical shock. All the connected blood vessels and heart chambers must be checked for leaks before removing the patient from the heart/lung machine.
Patients are usually able to recover a few days after surgery, and if there are no signs of the body immediately rejecting the organs, patients are allowed to go home within 2 weeks.
Development After A Transplant
The body's immune system recognises and defends itself against foreign substances such as bacteria or viruses. It also recognises an organ from another person as a foreign substance and attempts to destroy it. The medications thus supress the immune system to minimise the chances that it will attack the new heart.
That is why, after a heart transplant, patients must take medications to suppress the immune system, minimising the chances that it will attack the new heart. These medications, which must be taken for life, can cause significant side effects, including hypertension, fluid retention, tremors, excessive hair growth , and possible kidney damage. To combat these problems, additional drugs are often prescribed. A transplanted heart functions differently from the old one. Because the nerves leading to the heart are cut during the operation, the transplanted heart beats faster (about 100 to 110 beats per minute). The new heart also responds more slowly to exercise and doesn't increase its rare as quickly as before.
Also because the nerves have been cut in the transplanted heart, transplant recipients do not usually feel chest pains if their coronary arteries are not supplying enough oxygen to the heart muscle. Therefore, tests must be performed yearly to look for possible narrowing of the coronary arteries.
The body's immune system protects the body from infection. Cells of the immune system move throughout the body, checking for anything that looks foreign or different from the body's own cells. Immune cells recognize the transplanted organ as different from the rest of the body and attempt to destroy it; when the body's immune system attacks the donor heart, it is said to be "rejecting" the organ. This may occur anytime after the operation but, most often they occur within the first few months. This is called rejection.
To prevent rejection, patients receive immunosuppressants, drugs that suppress the immune system so that the new organ is not damaged.
ęCopyright TQ Team 25896, 1999. The Circulatory System- Online Learning.