The field of lung transplantation has seen steady progress over the past two decades and is now widely accepted as a treatment option for end-stage lung disease. According to the Organ Procurement and Transplantation Network (OPTN), there have been approximately 10,000 lung transplants performed in the United States. Although the list of candidates for lung transplantation is steadily growing, as is the number of transplantation centers, the annual transplant rate is leveling off due to a limited number of donors. As a result, the waiting time for lung transplant can be up to 2 years.
Chronic obstructive pulmonary disease or emphysema (including alpha-1-antitrypsin deficiency) has been the underlying disease process in nearly half of all lung transplants. Cystic fibrosis, idiopathic pulmonary fibrosis, and primary pulmonary hypertension are all disease states that primarily affect the lungs, and are also common reasons for lung transplant. Other causes include sarcoidosis (a disease in which lung tissue develops a granulomatosis or scar-like consistency), bronchiectasis (destruction of the bronchial tubes in the lungs from severe infection), occupational lung disease, Eisenmenger’s syndrome (a congenital heart condition which leads to low oxygen levels in blood and elevated red blood cell counts), and rejection of a prior lung transplant.
Lung transplant has been shown to improve lung function and quality of life in all of these diseases, but the procedure does carry significant risk of mortality. Therefore, there are strict guidelines for referring a patient for lung transplant. Specific diseases have their own prognostic criteria used in deciding whether a transplant is appropriate, but general indications for transplant include advanced disease with life expectancy of 2-3 years, unsuccessful medical therapy, severe functional limitation, and poor quality of life. Absolute contraindications to transplant include current smoking, active malignancy, HIV infection, and severe impairment of other organs.
There are four major types of lung transplantation: heart-lung transplantation, single-lung transplant, bilateral lung transplant, and living donor lobe transplant. Heart-lung transplant was the first procedure to have long-term success, and it is now primarily used in patients with Eisenmenger’s syndrome or with concurrent severe cardiac dysfunction. Single-lung transplant is the most commonly used technique and has been successful for most types of lung disease except cystic fibrosis. Bilateral transplantation is the preferred method for cystic fibrosis and bronchiectasis, in which both lungs must be removed due to infection. Finally, one technique that is gaining support due to the limited supply of donor lungs is the transplantation of lower lobes from living donors. Cystic fibrosis is the most common disease for which this procedure has been used.
Despite advances in surgical techniques, immunosuppressive therapies, and infection prophylaxis, survival rates after lung transplantation are significantly lower than for other solid organ transplants. Data reported from OPTN for lung transplants performed between 1995 and 2000 show a 1-year survival of 75.4% for men and 76.4% for women and a 3-year survival of 57% for both sexes. Complications from lung transplant include airway complications, rejection, infection, and malignancy. The most important causes of mortality following the time period just after surgery (perioperative period) are acute rejection and infections. The greatest threat to long-term survival is bronchiolitis obliterans, a form of chronic tissue rejection found in up to 60-70% of patients who survive 5 years. The cause of bronchiolitis obliterans is not entirely known, but proposed mechanisms include HLA mismatching (incomplete or imperfect genetic match of the graft tissue to the patient tissue), viral infection (cytomegalovirus), decreased oxygen to the airway (airway ischemia), and problems related to the immune system. Currently, the only definitive treatment for chronic rejection is retransplantation.
SEE ALSO: Acquired immunodeficiency syndrome, Chronic obstructive pulmonary disease, Lung disease
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