None — Heart Transplants
A heart transplant is the removal of a diseased heart and replacement with a donor heart from someone who has just died (the donor). According to the Organ Procurement and Transplantation Network (OPTN), 2,334 heart transplants were performed in the U.S. last year. 90 percent of patients requiring a heart transplant have end-stage heart failure (a condition in which the heart is too weak to pump blood to meet the needs of the body). Other common reasons for a heart transplant include severe angina, serious heart defects, and life-threatening abnormal heart rhythms.
A heart transplant is a life-saving option for patients. However, there aren't enough donor hearts to meet the demand. Currently, more than 3,100 people are on the transplant waiting list for a donor heart.
Survival after a Heart Transplant
According to the National Heart, Lung and Blood Institute, more than 88 percent of heart transplant patients survive at least one year and 50 percent survive 10 years or longer. One of the greatest risks of organ transplantation is rejection of the donor organ. Rejection occurs when the body's immune system detects the donor heart as foreign tissue and mounts an attack to "protect" the recipient's body. An acute rejection occurs within several days of the transplant. Chronic rejection is a slow type of rejection that occurs over several weeks to months. This type of rejection is very serious because it causes widespread damage to the coronary arteries (those that feed the heart muscle).
There are ways to reduce the risk of rejection. Initially, doctors perform blood and tissue matches to ensure the donor and recipient are compatible. This increases the likelihood that the recipient's immune system will accept the donor heart.
The second important step in reducing the risk for rejection is use of immunosuppressive medication. These drugs decrease the activity of the immune system, reducing its ability to attack the donor organ. Patients generally take the medication for the rest of their lives, though the doses may be tapered with time. The treatment reduces the risk for rejection, but increases the risk for infection. So doctors must balance the need for protecting the donor organ against protecting the overall health of the patient.
Rejection Warning: The Biopsy
Another important step in preserving transplanted hearts is patient monitoring. If rejection can be caught at early stages, doctors can often take steps to halt the process. However, when rejection occurs, patients often don't have any symptoms. Currently, doctors rely on a biopsy of the tissue samples from the donor heart to look for evidence of rejection.
A biopsy is done by making a tiny incision into the neck to access the right internal jugular vein. An alternative approach is made through the femoral vein in the groin. Next, using X-rays for guidance, a special catheter, called a bioptome, is inserted into the vein and fed to the right ventricle (lower chamber). Tiny pinchers at the end of the bioptome grasp small samples of tissue along the inner wall of the heart's chamber. David Baran, M.D., Transplant Research Director at Newark Beth Israel Medical Center in Newark, NJ, says doctors typically take a total of four to five samples from different areas of the heart to increase the likelihood of detecting rejection. The tissue samples are then sent to a lab for analysis. Baran says the presence of lymphocytes, specialized white blood cells, is a sign of organ rejection.
Biopsies are an important tool in the management of a heart transplant patient. The risk of rejection is greatest soon after transplant. Therefore, doctors may perform as many as 12 to 14 biopsies in the first year, then 2 to 3 a year thereafter. But the procedures carry their own set of risks. Some of the complications associated with biopsy include potential bleeding outside the heart and damage to the tricuspid valve (the valve that separates the upper and lower chambers on the right side of the heart). In addition, with time, biopsy becomes a little more difficult. Scar tissue in the neck area from previous incisions can make it harder to cleanly access the vein. In addition, scarring occurs in the areas inside the right ventricle where previous biopsies have been taken. So doctors must be careful to obtain biopsy samples from untouched areas of the heart to obtain "healthy" tissue.
AlloMap®
Some physicians are using another method to detect rejection of donor hearts, called AlloMap® Molecular Expression Testing. AlloMap uses a blood test to look for genetic markers associated with rejection. A recent clinical trial, called Invasive Monitoring Attenuation through Gene Expression (IMAGE), compared the outcomes of patients receiving AlloMap against a group receiving standard biopsies. The study found the patients monitored with the AlloMap test had similar rates of rejection, graft failure (i.e., loss of function in the transplanted heart) and death as those who received conventional biopsies. Thus, the AlloMap test was just as effective as the biopsy. In addition, patients receiving the AlloMap were able to have fewer biopsies/year.
Recently, Aetna, Inc., a major health insurance carrier, recognized the value of the test and has determined it as "medically necessary" for heart transplant patients. Baran says AlloMap will not replace biopsy for detection of heart transplant rejection. However, it may be able to greatly reduce the number of biopsies needed by patients. According to Baran the test is unable to determine the severity of rejection, so patients who show potential rejection, will still need to undergo a biopsy.
For information about AlloMap® Molecular Expressing Testing, click here.
For information or statistics on heart transplants:
American Society of Transplantation National Heart, Lung and Blood Institute Organ Procurement and Transplantation Network United Network for Organ Sharing