TOP6: Ambulatory Extra Corporeal Membrane Oxygenation as a Bridge to Lung Transplant

Background: Mechanical circulatory support, including both veno-venous (VV) and veno-arterial (VA) extra corporeal membrane oxygenation (ECMO), is being used more frequently to bridge critically ill patients to lung transplant (LTX). This study evaluates post LTX survival outcomes of patients bridged by ECMO. Methods: The United Network for Organ Sharing (UNOS) thoracic organ transplant database was queried for patients aged >/= 18 years between year 2016 and 2021 to identify pre-transplant patients supported by ECMO. Patients supported by both VA and VV-ECMO were excluded. The patients initially classified in VA-ECMO and VV-ECMO cohorts and further classified as ambulatory (AMB) and non-ambulatory (nAMB) within their respective ECMO cohorts. Each cohort was controlled against the non-ECMO patients. Univariate statistical tests as well as Kaplan-Meier survival curves were used for analysis. Results: Of total 14,369 LTX patients, 13,470 were non-ECMO, 702 were VV-ECMO (44% AMB, 56% nAMB) and 197 were VA-ECMO (47% AMB, 53% nAMB). Table 1A (non-ECMO v. AMB VV-ECMO v. nAMB VV-ECMO at time of LTX) and 1B (non-ECMO v. AMB VA-ECMO v. nAMB VA-ECMO at time of LTX) shows higher age (62 v. 52 v. 50) lower O2 requirement (4 v. 15 v. 10), LAS (44 v. 88 v. 89) and lesser likelihood of COVID etiology (1% v. 22% v. 6%) in non-ECMO group compared to VV-ECMO and VA-ECMO. Within the ECMO groups AMB and nAMB patients were comparable except idiopathic fibrosis was more common in nAMB. The 1-year post LTX survival between non-ECMO and AMB VV-ECMO was comparable (88% v. 88%, p=0.66) which was better than nAMB VV-ECMO patients (88% v. 88% v. 81% (nAMB VV-ECMO), p<.01, F1A). The 1-year (71% v. 78% v. 88%) survival was better for AMB VA-ECMO patients than nAMB VA-ECMO patients, and better for non-ECMO patients than AMB VA-ECMO patients (p<.01, F1B). A Cox proportional hazard model showed that compared to non-ECMO patients, the nAMB VV-ECMO patients (HR = 1.25, p=0.02) had higher risk of post LTX mortality whereas post LTX risk for AMB VV-ECMO patients (HR = 0.95, p=0.71) was similar. Conclusion: Although ambulatory VV-ECMO patients have higher LAS and O2 requirements at time of transplant, their post LTX survival is comparable to the non-ECMO patients. Survival amongst the VA-ECMO patients continued to be poor compared to the non-ECMO patients irrespective of their ambulatory status. Strategies to ambulate ECMO patients could be associated better post LTX outcomes. Figure 1. Survival by ECMO ambulationTable 1. Patient Characteristics at time of LTX