ABSTRACT
In 2005, the number of lung transplants performed in the USA reached 1405, the greatest number since the origin of the UNOS registry.1 The number of single lung transplantations has been rela tively constant internationally for almost a decade, but there has been a gradual increase in the number of double lung transplantations.22 The volume of double lung transplants in 2004, over 1000, was twice that in 1994. The five-year graft survival rate for lung transplants in the U.S. is approximately 48%,12 similar to the five-year survival rate of 49% reported by the ISHLT.22 Similar to the survival trends observed in heart transplant recipients, the short-term survival rates in lung transplant recipients have improved over time but the gain has been concentrated in the first year after transplantation. Beyond the first year the survival slopes parallel those of earlier eras of lung transplantation (Fig. 4). In those who survive more than five years, bronchiolitis obliterans or bronchiolitis obliterans syndrome is preva lent. It affects up to 60% of lung transplant recipients who survive 10 years. Bronchiolitis obliterans accounts for 26.5% of all deaths in lung transplant recipients who survive beyond five years of transplantation. Other causes of death include infections in 18%, graft failure due to unknown causes in 17%, malignancy in 12%, cardiovascular diseases in 5.2%.22 Bronchiolitis obliterans, which was first reported among re cipients of heart-lung transplants at Stanford University who developed a progressive deterioration in forced expiratory volume in one second (FEV-1), is characterized by an inflammatory and fibrogenic process affecting the membranous and respiratory bronchioles and leading to cicatricial luminal narrowing and severe obstructive airways disease.23 It is one of the most important factors limiting long-term survival among lung transplant recipients.24 A prior history of acute rejection, pres ence of HLA-specific antibodies, exposure to environmental irritants and toxins, infections, airway ischemia, aspiration of gastrointestinal contents, preexisting connective tissue disorders, radiation injury and a variety of other donor and recipient factors have been implicated in the pathogenesis of this condition, suggesting a combined role for im munologic and non-immunologic injury as the underlying mechanism for chronic graft loss.23 25
It is evident from these data that long-term graft survival rates have reached a plateau in recent years, despite substantial improvements in short-term graft survival. The incidence of late graft failure in kidney, liver, heart and lung transplant recipients has remained at about 3% to 5% per year over the past decade. Since chronic allograft rejection is not the only underlying cause for graft loss in these cases, this incident rate defines the upper limit of rate of chronic allograft loss due to chronic rejection.26
