Pulmonary hypertension (PH) in patients with chronic obstructive pulmonary disease (COPD) was associated with higher mortality rates after bilateral lung transplantation (transplantation of both lungs), but not after single lung transplantation (LTx), according to a new study of the United Network for Organ Sharing (UNOS) database.
The study, “Adverse outcomes associated with pulmonary hypertension in chronic obstructive pulmonary disease after bilateral lung transplantation,” was published in the journal Respiratory Medicine.
PH often accompanies severe end-stage COPD, but the rate at which PH occurs in patients with COPD is not known.
A total of 3,362 first-time LTx recipients with a COPD diagnosis who underwent lung transplant between May 2005 and September 2013 were identified in the UNOS Registry thoracic database. UNOS is the private, non-profit organization that manages the organ transplant system in the U.S.
Of the total patients identified, 54 percent (1,686) met the diagnostic criterion for PH with an average pulmonary artery pressure (mPAP) of 25 mmHg or more, determined by right heart catheterization (RHC). Among these patients, 653 underwent a single LTx, and 1,033 were bilateral LTx recipients.
The study found that the mortality risk was increased with higher mPAP in bilateral LTx patients with COPD who also had PH, so that an increase of 10 mmHg in mPAP was linked to a 10 percent increase in the chances of dying after the double transplant. This was not observed in patients undergoing a single LTx.
The study also revealed that risk factors for post-LTx mortality included: Being of black ethnicity, of older age at the time of the transplantation, of greater body mass index (a measure of body fat), scoring lower in the six-minute walk distance test (a test assessing exercise capacity), having higher levels of Class 1 panel reactive antibody (PRA; an estimation of a person’s potential reactivity to a donated organ), having a greater initial lung allocation score (the UNOS priority rating for a lung transplant), and having received extracorporeal membrane oxygenation (ECMO) support (use of an artificial lung).
“In conclusion, we found an association between elevated mPAP and increased risk of mortality after bilateral LTx, but not after single LTx, in patients with COPD.” the researchers wrote.
“These findings may have implications regarding allocation of donor lung allografts to patients with COPD, particularly with coexisting PH or a history of increasing mPAP while awaiting LTx. Further work is needed to understand the mechanisms by which PH exerts a long-term influence on mortality in LTx recipients with COPD and why this influence is mitigated among recipients of single LTx,” the team concluded.