Pulmonary arterial hypertension (PAH) patients referred for transplant typically have an inadequate response to guideline-directed therapies, are at intermediate-to-high risk of death (with 1-year mortality exceeding 10%), or have conditions like pulmonary capillary hemangiomatosis (PCH) or pulmonary veno-occlusive disease (PVOD) that respond poorly to medical treatment.¹ A critical question in PAH transplantation remains unresolved – given the long-standing cardiac consequences of high right ventricular (RV) afterload and poor RV/left ventricular (LV) function, should patients receive a bilateral lung transplant or heart-lung transplants? How do their survival outcomes differ? At the ERS Congress 2024, Dr. Baharan Zarrabian, a pulmonologist from the Mayo Clinic, addressed important findings regarding transplant options and compared the survival outcomes in these groups of patients with PAH.¹ 

This retrospective cohort, multicenter study analyzed data from the United Network for Organ Sharing (UNOS) database, which included patients who had undergone heart-lung and bilateral lung transplantation across all transplant centers in the United States (US) between June 2004 and September 2022.¹ Patients with pre-existing congenital or structural heart abnormalities and those with a LV assist device, total artificial heart and an intra-aortic balloon pump in place at the time of transplant were excluded.¹ Four a priori sensitivity sub-cohorts were defined to evaluate survival outcomes by PAH severity and definition, based on the cardiac index (CI): Group 1 (CI<2.0), group 2 (2.0<CI<2.5), group 3 (CI>2.5) and group 4 (transplant recipients with full availability of hemodynamic data at the time of transplant which was inclusive of mean pulmonary arterial pressure [mPAP] ≥20mmHg, pulmonary vascular resistance [PVR] ≥3 Wood units and a pulmonary capillary wedge pressure [PCWP] ≤15mmHg). The primary endpoints were survival at 1 and 5 years, while secondary endpoints included pre-transplant characteristics and post-transplant outcomes.¹ 

The study analyzed a total of 914 adult PAH patients; 84.9% (n=776) received bilateral lung transplants, and 15.1% (n=138) underwent heart-lung transplants.¹ Patients with bilateral lung transplant were older (49 vs. 41 years, p<0.001) and had a lower incidence of requiring dialysis prior to transplant (2.1% vs. 7.3%, p=0.003).¹ No significant differences were observed in 1-year (84.6% vs. 88.1%, p=0.28), 5-year (58.6% vs. 56.2%, p=0.71) or 10-year (47.1% vs. 41.4%, p=0.52) survival rates between the bilateral lung and heart-lung transplant groups, which closely aligned with the Organ Procurement and Transplantation Network (OPTN) and the Scientific Registry of Transplant Recipients (OPTN/SRTR) annual data report from 2022.¹ Similar findings were observed across all sensitivity subcohorts (p>0.05).¹ Rates of acute rejection prior to discharge were also similar (11.5% vs. 10.9%, p=0.90).¹ Despite a higher proportion of bilateral lung transplant patients requiring extracorporeal membrane oxygenation (ECMO) (24.2% vs. 10.8%, p=0.02) or remaining intubated at 72 hours postoperatively (43.0% vs. 23.9%, p<0.001), these factors did not result in worse long-term outcomes.¹ Key differences between the groups included higher CI (2.4 vs. 2.2, p=0.02) and a lower pulmonary capillary wedge pressure (11mmHg vs. 13mmHg, p<0.001) in the bilateral lung transplant group, while heart-lung transplant recipients experienced shorter ischemic times (3.8 vs. 5.5 hours, p<0.001).¹ 

In conclusion, the study highlights that bilateral lung transplants may be a viable option for PAH patients, offering similar survival rates to heart-lung transplants.