TIMING OF SINGLE-LUNG TRANSPLANTATION FOR PRIMARY PULMONARY-HYPERTENSION

Single lung transplantation has been advocated as a definitive treatme nt for primary pulmonary hypertension. Because of reports of improved survival in some patients with vasodilators and anticoagulants, the ti ming of referral for single lung transplantation needs to be examined. Survival in primary pulmonary hypertension was estimated, with the us e of a proportional hazards model, from data obtained from the Nationa l Institutes of Health registry on primary pulmonary hypertension. Wai ting times for single lung transplantation, obtained from the United N etwork for Organ Sharing, were found to follow an exponential distribu tion. Under the assumption that waiting time and survival are independ ent, a model was developed to estimate the probability of surviving to single lung transplantation, depending on the waiting time for a sing le lung transplantation, and the delay in transplant referral. Example s were computed with hemodynamic data from the National Institutes of Health registry on primary pulmonary hypertension: waiting times of 6, 12, 18, and 24 months and delays in single lung transplantation refer ral of 0, 1, 2, and 3 years. For a waiting time of 6 months, the chanc e of surviving to single lung transplantation with a 3-year delay vari es from 19% for a patient with a mean pulmonary artery pressure of 80 mm Hg to 72% for a patient with a mean pulmonary artery pressure of 41 mm Hg. For a waiting time of 24 months and a 3-year delay in single l ung transplantation referral, this probability varies from 14% (mean p ulmonary artery pressure 80 mm Hg) to 59% (mean pulmonary artery press ure 41 mm Hg). Patients with primary pulmonary hypertension should be evaluated for their acute response to vasodilators. In patients who do not respond, the timing of referral for single lung transplantation s hould be influenced by the patient's estimated survival without single lung transplantation and their chance of surviving and receiving a si ngle lung transplantation, depending on the delay in transplantation r eferral.