Epidemiology
According to the registry of the International Society of Heart and Lung Transplantation (ISHLT), presently the worldwide procedural frequency is ~3,200 per year. The proportion of patients transplanted with IPF has increased constantly during recent years. Twenty-three percent of more than 34,000 recipients transplanted worldwide between 1995 and 2011 had a diagnosis of IPF (3.4% had other forms of pulmonary fibrosis). With implementation of the lung allocation score (LAS) in the United States in May 2005, which balances the estimated risk of death on the waiting list and predicted survival probability after transplantation, LTx for IPF increased from 23.9% of all transplantations in 2004 to 33.1% in 2007, and IPF has become the most frequent disease for which LTx is performed in the United States. In 2010, the proportion of reported transplants worldwide for IPF was nearly equal to that reported for emphysema.
Numbers of patients transplanted for PAH have, however, progressively fallen worldwide. PH accounts for just 3% of all indications during recent years compared with 12% twenty years ago. The advent of effective targeted medical therapy for PAH and the continued worldwide problem of donor lung shortage have led to significant reductions in the numbers of patients with PAH undergoing transplantation. Nevertheless, the long-term outcomes of medically treated patients remain uncertain, and transplantation will remain an important mode of therapy for those who fail such therapy. Studies indicate up to 25% of patients with idiopathic PAH may fail to improve on disease-targeted therapy, and the prognosis of patients who remain in World Health Organization (WHO)-functional class (FC) III or IV remains poor.