Impact of Extracorporeal Membrane Oxygenation Bridging Duration on Lung Transplant Outcomes

Abstract

Background: We sought to characterize the association between venovenous extracorporeal membrane oxygenation (VV-ECMO) bridging duration and outcomes in patients listed for lung transplantation.

Methods: A retrospective observational study was conducted using the Organ Procurement and Transplantation Network (OPTN) database to identify adults (aged ≥18 years) who were listed for lung transplantation between 2016 and 2020 and were bridged with VV-ECMO. Patients were then stratified into groups, determined by risk inflection points, depending on the amount of time spent on pretransplant ECMO: group 1 (≤5 days), group 2 (6-10 days), group 3 (11-20 days), and group 4 (>20 days). Waiting list survival between groups was analyzed using Fine-Gray competing risk models. Posttransplant survival was compared using Cox regression.

Results: Of 566 eligible VV-ECMO bridge-to-lung-transplant patients (median age, 54 years, 49% men), 174 (31%), 124 (22%), 130 (23%), and 138 (24%) were categorized as groups 1, 2, 3, and 4, respectively. Overall, median duration of VV-ECMO was 10 days (interquartile range, 1-211 days), and 178 patients (31%) died on the waiting list. In the Fine-Gray model, compared with group 1, patients bridged with longer ECMO durations in group 2 (subdistribution hazard ratio [SHR], 2.95; 95% CI, 1.63-5.35), group 3 (SHR, 3.96; 95% CI, 2.36-6.63), and group 4 (SHR, 4.33; 95% CI, 2.59-7.22, all P < .001) were more likely to die on the waiting list. Of 388 patients receiving a transplant, pretransplant ECMO duration was not associated with 1-year survival in Cox regression.

Conclusions: Prolonged duration of ECMO bridging was associated with worse waiting list mortality but did not impact survival after lung transplant. Prioritization of very early transplantation may improve waiting list outcomes in this population.

Figure 1.

CONSORT diagram. ECMO=extracorporeal membrane oxygenation, VA=venoarterial, VV=venovenous, COVID-19=coronavirus disease of 2019. *Age at time of lung transplant listing. **t=1,148 days, likely due to coding discrepancies resulting from multiple ECMO runs starting prior to listing

Figure 2.

Fine-Gray competing risks model for waitlist mortality or clinical deterioration leading to waitlist removal, with transplant or improvement as competing risks. Model covariates included age, sex, body mass index (BMI), Lung Allocation Score (LAS), tobacco use, diabetes, UNOS-defined diagnosis group, overall waitlist time, and transplant center region. Compared to Group 1 patients, those in Group 2 (HR:1.28 , 95%CI:0.51–3.20), Group 3 (HR:1.41, 95%CI:0.64–3.08) and Group 4 (HR:1.59, 95% CI:0.67–3.77) had higher risk of waitlist mortality. VV=venovenous, ECMO=extracorporeal membrane oxygenation.

Figure 3.

Restricted cubic spline of Fine-Gray model with waitlist mortality or clinical deterioration as a primary composite outcome with transplantation or clinical improvement as competing risks. Splines were generated out to (A) 200 and (B) 30 days for better visualization, with panel B representing the purple cut-out in panel A. The hazard of waitlist mortality is substantially lower in those transplanted prior to 10 days of ECMO support compared to those with longer durations, however, the hazard stabilizes after around 20 days of support. SHR=sub-hazard ratio, VV=venovenous, ECMO=extracorporeal membrane oxygenation.

Figure 4.

Cox proportional hazards regression of lung transplant recipients bridged with VV-ECMO. VV-ECMO duration was not associated with 12-month mortality. VV=venovenous, ECMO=extracorporeal membrane oxygenation, BMI=body mass index, LAS=lung allocation score.