Extracorporeal membrane oxygenation bridge to transplant in the era of the lung composite allocation score

Abstract

The lung composite allocation score (CAS) aims to improve waitlist outcomes for lung transplant candidates by prioritizing characteristics that reflect transplant urgency, including extracorporeal membrane oxygenation bridge to lung transplant (ECMO-BTT). Whether ECMO-BTT has been impacted by CAS is unknown. We analyzed the Organ Procurement and Transplant Network database to examine differences in ECMO-BTT utilization and characteristics and outcomes between transplant recipients who were transplanted one year before and one year after CAS implementation. Lung transplant recipients who received ECMO-BTT in the post-CAS era were younger (p < 0.01), more likely to be on ECMO at transplant listing rather than be initiated after (p < 0.05), and had shorter waitlist time (p < 0.01). Waitlist time was shorter in the post-CAS era among recipients (even non-ECMO) with high allocation scores only. This may have contributed to decreased use of ECMO-BTT in the post-CAS era (p = 0.03). One-year post-transplant survival did not differ between eras for ECMO-BTT patients, though was significantly better in the CAS era for non-ECMO-BTT patients (92% vs 90%, p < 0.01). We report initial results of ECMO-BTT utilization in the post-CAS era.

Keywords: Bridge-to-transplant; Composite allocation score; Extracorporeal membrane oxygenation; Lung transplantation; Waitlist time.

Figure 1

Waitlist time for lung transplant recipients between pre-CAS and CAS eras, stratified by allocation score percentile. We determined waitlist time between pre-CAS and CAS eras as a function of illness severity based on allocation score percentile for all lung transplant recipients during the study time period. For patients within the top 95th percentile of illness severity, median waitlist time was 15 days (IQR 7-35) during the pre-CAS era, and 11.5 days (IQR 4-35) during the CAS era, p < 0.05. Similarly, for patients within the 90th percentile median waitlist time was 18 days (IQR 8-40) pre-CAS vs 9.5 days (IQR 4-41) after CAS implementation, p < 0.01. Median waitlist time was 19 days (IQR 8-61) pre-CAS vs 13.5 days (IQR 4-55) post-CAS, p < 0.01, for patients within the top 75th percentile. For patients below the 50th percentile of illness severity, there was no difference in waitlist time between eras [25 days (IQR 9-76) pre-CAS vs 24 days (7-86) post-CAS, p = 0.36]. Therefore, CAS implementation is associated with a reduction in waitlist time for patients within the top 75th percentile of illness severity only.

Figure 2

KM 1-year survival for recipients with and without ECMO-BTT before and after CAS implementation. In the year preceding the introduction of CAS, there were a total of 2741 lung-only transplant recipients included in the OPTN STAR registry, of whom 212 required ECMO-BTT. One-year survival was 2274/2529 (90%) for those not requiring ECMO-BTT, and 175/212 (83%) for those receiving ECMO-BTT. Post-CAS, 1-year survival was 2626/2856 (92%) for patients without ECMO-BTT and 160/191 (84%) for ECMO-BTT recipients. Between eras there was no significant survival difference for ECMO-BTT (83% vs 84%, p = 0.79), though survival increased for patients not requiring ECMO-BTT (90% vs 92%, p < 0.01).