Lung Transplant Outcomes Group Research Articles

Long-term air pollution exposure and the risk of primary graft dysfunction after lung transplantation

Background: Primary graft dysfunction (PGD) contributes substantially to both short and long-term mortality after lung transplantation but the mechanisms that lead to PGD are not well understood. Exposure to ambient air pollutants is associated with adverse events during waitlisting for lung transplantation, and chronic lung allograft dysfunction but its association with PGD has not been studied. We hypothesized that long-term exposure of the lung donor and recipient to high levels of ambient air pollutants would increase the risk of PGD in lung transplant recipients. Methods: Using data from 1428 lung transplant recipients and their donors enrolled in the Lung Transplant Outcomes Group (LTOG) observational cohort study, we evaluated the association between the development of PGD and zip-code based estimates of long-term exposure to six major air pollutants (ozone, nitrogen dioxide, sulfur dioxide, carbon monoxide, PM2.5 and PM10) in both the lung donor and the lung recipient. Exposure estimates used daily EPA air pollutant monitoring data and were based on the geographic centroid of the each subject’s residential zip code. Associations were tested in both univariable and multivariable models controlling for known PGD risk factors. Results: We did not find strong associations between air pollutant exposures in either the donor or the recipient and PGD. Conclusions: Exposure to ambient air pollutants, at the levels observed in this study, may not be sufficiently harmful to prime the donor lung or the recipient to develop PGD particularly when considering the robust associations with other established PGD risk factors.

Body mass index and mortality following primary graft dysfunction: A Lung Transplant Outcomes Group study

Higher body mass index (BMI) increases risk of developing primary graft dysfunction (PGD) after lung transplantation; whether BMI is associated with decreased survival after PGD is unknown. We utilized the Lung Transplant Outcomes Group (LTOG) cohort of 1,538 subjects from 2011-2018. We evaluated the association between pre-operative BMI and graft survival among subjects with severe PGD using Cox proportional hazards models with linear splines. Models were stratified by center and adjusted for sex, age, lung allocation score, and diagnosis. PGD developed in 383 subjects. Among subjects with PGD, low BMI was associated with increased mortality while high BMI was not associated with differential mortality, compared to normal BMI. Results were similar for 90-day and 1-year survival. While high BMI increases risk of developing PGD, it does not appear to be associated with survival after PGD. Future work should focus on PGD prevention rather than PGD management in patients with obesity.

Contemporary trends in PGD incidence, outcomes, and therapies.

We sought to describe trends in extracorporeal membrane oxygenation (ECMO) use, and define the impact on PGD incidence and early mortality in lung transplantation. Patients were enrolled from August 2011 to June 2018 at 10 transplant centers in the multi-center Lung Transplant Outcomes Group prospective cohort study. PGD was defined as Grade 3 at 48 or 72 hours, based on the 2016 PGD ISHLT guidelines. Logistic regression and survival models were used to contrast between group effects for event (i.e., PGD and Death) and time-to-event (i.e., death, extubation, discharge) outcomes respectively. Both modeling frameworks accommodate the inclusion of potential confounders. A total of 1,528 subjects were enrolled with a 25.7% incidence of PGD. Annual PGD incidence (14.3%-38.2%, p=.0002), median LAS (38.0-47.7 p=.009) and the use of ECMO salvage for PGD (5.7%-20.9%, p=.007) increased over the course of the study. PGD was associated with increased 1 year mortality (OR 1.7 [95% C.I. 1.2, 2.3], p=.0001). Bridging strategies were not associated with increased mortality compared to non-bridged patients (p=.66); however, salvage ECMO for PGD was significantly associated with increased mortality (OR 1.9 [1.3, 2.7], p=.0007). Restricted mean survival time comparison at 1-year demonstrated 84.1 days lost in venoarterial salvaged recipients with PGD when compared to those without PGD (ratio 1.3 [1.1, 1.5]) and 27.2 days for venovenous with PGD (ratio 1.1 [1.0, 1.4]). PGD incidence continues to rise in modern transplant practice paralleled by significant increases in recipient severity of illness. Bridging strategies have increased but did not affect PGD incidence or mortality. PGD remains highly associated with mortality and is increasingly treated with salvage ECMO.

Validation of a Simple to Use PGD Prediction Algorithm

<h3>Purpose</h3> Primary graft dysfunction (PGD) is the leading cause of early morbidity and mortality after lung transplantation. We previously developed an easy to use PGD predictive model utilizing the Lung Transplant Outcomes Group (LTOG) cohort. We therefore sought to demonstrate the net benefit of the model at an external site as a measure of model generalizability. <h3>Methods</h3> We tested external validation in a well-phenotyped lung transplant cohort from Washington University in St. Louis (WashU) for a PGD predictive model based on lung allocation score, body mass index, pulmonary arterial pressure, recipient total lung capacity, donor and recipient age and gender, donor mode of death, and donor distance to transplant center. We primarily employed decision curve analysis (DCA) to quantify the net benefit of the predictive model and also assessed model discrimination using the c-statistic and calibration using the Hosmer-Lemeshow (H-L) test. <h3>Results</h3> The incidence of PGD at WashU was lower than in the LTOG cohort (7% vs 25%); the validation model accounts for the differences in PGD incidence. The model demonstrated good discrimination (c-statistic=0.67) and calibration (H-L p=0.2, where non-significant p-value is good calibration). DCA describes whether the model performs better than alternatives of classifying everyone (or no one) as high PGD risk as well as the net benefit of the model across a range of decision thresholds. The DCA (Figure 1) shows that the predictive model demonstrates significant net benefit in the PGD incidence range 2-15%, incorporating the PGD incidence seen in the WashU cohort. <h3>Conclusion</h3> Our simple to implement PGD predictive model demonstrates excellent net benefit, even at centers with differing PGD incidence than the discovery cohort centers. This model can be used to identify recipients at high and low risk for PGD across a range of transplant centers, allowing treatment teams to be prepared for post-transplant complications and identify patients for potential enrollment in targeted intervention studies based on patient risk.

Circulating Coagulation Regulator Levels After Lung Transplantation Are Associated with Acute Kidney Injury

<h3>Purpose</h3> Acute kidney injury (AKI) is a common morbidity after lung transplantation, with postoperative rates up to 65%. Since microvascular coagulation contributes to AKI in preclinical models, we hypothesized that post-reperfusion circulating levels of the coagulation regulators plasminogen activator inhibitor-1 (PAI-1), protein C, and resistin, an inhibitor of protein C, would be associated with AKI. <h3>Methods</h3> The study population included 189 recipients enrolled from 7/2017-6/2019 in the 5-center Lung Transplant Outcomes Group Acute Kidney Injury (LTOG-AKI) prospective cohort study. We used Cuzick's nonparametric test of trend to examine the associations of plasma PAI-1, resistin, and protein C levels at 6 and 24 hours post-reperfusion with AKI severity (grouping stages 2-3) over the first 7 days post-transplant. We staged AKI using Kidney Disease Improving Global Outcomes creatinine criteria. We constructed ordinal logistic regression models of the association of each biomarker with AKI stage adjusting for preoperative biomarker levels, age, gender, chronic kidney disease, and transplant diagnosis. <h3>Results</h3> AKI stage 1 occurred in 45 (24%) and stage 2-3 in 50 (26%) patients. Hospital mortality was substantially higher in stage 2-3 AKI (18% vs 2% for both no AKI and stage 1 AKI, p=0.001). Plasma PAI-1 and resistin levels at 6h were associated with AKI stage (p<0.001, p=0.001, respectively), with similar findings at 24h (p<0.001, p=0.006, respectively). Protein C levels at 6h decreased with higher AKI stage (p=0.016). Six-hour PAI-1 and protein C remained associated with AKI stage in multivariable models, while the 6h resistin-AKI stage association was attenuated, particularly by adjustment for age and preoperative resistin levels (<b>Figure 1</b>). <h3>Conclusion</h3> Plasma levels of coagulation regulators at 6h post-lung transplant are associated with AKI stage and may offer insight into pathophysiologic mechanisms contributing to high AKI rates in this population.

Plasma Neutrophil Gelatinase-Associated Lipocalin to Predict Acute Kidney Injury After Lung Transplantation: A Multicenter Cohort Study

<h3>Purpose</h3> Post-operative acute kidney injury (AKI) occurs in up to 65% of lung transplant recipients and is associated with chronic kidney disease and mortality. Plasma neutrophil gelatinase-associated lipocalin (pNGAL) is a biomarker of early structural kidney damage that has improved prediction of AKI compared with clinical variables alone in non-transplant patient populations. We sought to determine the association of pNGAL with AKI after lung transplantation and whether it could improve AKI prediction. <h3>Methods</h3> We included 189 lung transplant recipients enrolled in the prospective 5-center Lung Transplant Outcomes Group Acute Kidney Injury (LTOG-AKI) cohort study from 7/2017 - 6/2019. We tested pNGAL levels pre-transplant and at 6 and 24 hours post-reperfusion. We defined AKI using Kidney Disease Improving Global Outcomes creatinine criteria during the first 7 post-op days. We tested associations of pNGAL and clinical variables with AKI using the Wilcoxon rank-sum test. We constructed logistic regression models to predict AKI using pNGAL alone, clinical variables alone, and pNGAL plus clinical variables. <h3>Results</h3> AKI developed in 95 (50%) patients (45 (24%) stage 1, 21 (11%) stage 2, 29 (15%) stage 3), occurring a median of 2 (IQR 1-3) days post-op. pNGAL levels at 6h (p=0.001) and 24h (p<0.001) were significantly associated with AKI. Over 90% of 6h pNGAL levels were >150 ng/ml, the cut-off typically used to denote high risk of AKI in non-transplant populations. A model including clinical variables of recipient age and gender, transplant diagnosis and type, and lung allocation score had an area under the receiver operating characteristics (auROC) curve higher than pNGAL alone (Figure 1). Adding pNGAL to the clinical model did not improve the auROC curve. Model results were similar when defining AKI as stage 2-3 only. <h3>Conclusion</h3> Early post-lung transplant pNGAL levels were associated with AKI but did not add to clinical variables in predicting AKI.

Predicting PGD after Lung Transplantation

<h3>Purpose</h3> Primary graft dysfunction (PGD) is the leading cause of early morbidity and mortality after lung transplantation. Prior studies highlight the role of donor smoking in poor post-transplant outcomes. We therefore aimed to identify clinical risk factors for PGD after lung transplantation, more accurately assess the impact of donor smoking, and develop an accurate, generalizable PGD prediction model. <h3>Methods</h3> We performed a 10-center prospective cohort study of patients in the Lung Transplant Outcomes Group from 2012-2018. PGD was defined as grade 3 PGD at 48 or 72 hours after lung reperfusion. We defined donor smoking history by clinical documentation, UNOS-reported donor smoking, or donor cotinine >9 mg/ml from urine collected at organ procurement. Building on our prior PGD prediction models, multivariable logistic regression was used to identify PGD risk factors and develop regularized predictive models with a simple user interface (R shiny). <h3>Results</h3> Of 1180 patients, 26% developed PGD and 633 (53%) received an organ from a previously smoking donor. The PGD predictive model included novel predictors of center and donor distance plus recipient age, lung allocation score (LAS), body mass index, pulmonary artery pressure, sex, and indication for transplant; donor age, sex, mechanism of death, and donor distance; and interaction terms for LAS and donor distance. The interface allows for real-time assessment of PGD risk for any donor/recipient combination. The predictive model offers decision making benefit in the PGD risk range of 0.15-0.5. Donor smoking was associated with increased risk of PGD but not patient mortality (Figure 1). <h3>Conclusion</h3> We developed a clinically applicable PGD predictive algorithm based on modern lung transplant practices to aid in transplant decision making, post-transplant care, and to facilitate development of enriched PGD treatment trials. Donor smoking is a risk factor for PGD development but is not associated with increased mortality, potentially because of a lower risk phenotype of PGD occurring in smoking donor recipients.

Rising PGD Incidence Parallels Increased Recipient Disease Severity

<h3>Purpose</h3> Priority on waitlist urgency over post-transplant survival has decreased waitlist mortality with no appreciable change in short to mid-term survival. We sought to define the effects of increased pressure to transplant sicker candidates on PGD incidence and mortality as a leading indicator for long-term effects. <h3>Methods</h3> We used the multi-center prospective Lung Transplant Outcomes Group cohort study, designed to identify risk factors for PGD and mortality. Patients were enrolled from August 2011 to June 2018 at 10 centers. PGD was graded based on the 2016 PGD consensus ISHLT guidelines. Specifically, PGD was defined as grade 3 PGD (PaO2 /FiO2 ratio <200) at 48 or 72 hours after allograft reperfusion. Patients on ECMO post-transplant were graded as PGD only if there was evidence of parenchymal infiltrates on chest radiograph. <h3>Results</h3> 1,528 subjects were enrolled with a 25.6% incidence of PGD overall. PGD incidence increased from 14.3% to 38.2% over the course of the study. From 2012 to 2018, the median LAS increased from 38.7 to 42.9 and the use of ECMO salvage increased from 5.7% to 20.9% (Fig.1a). PGD was associated with mortality overall (p=0.0001, Fig.1b). Bridging strategies were not associated with mortality (p=0.66); however, salvage ECMO for PGD was significantly associated with mortality (HR 2.1 [1.6; 2.8]; p<0.0001). Restricted mean survival time comparison at 1-year demonstrated 101 days lost in VA salvaged recipients when compared to those without PGD and 29 days for VV. Effects on mortality increased over time (Fig1c). <h3>Conclusion</h3> Severity of illness continues to rise in modern surgical practice paralleled by significant increases in PGD incidence. Bridging strategies have increased but appear safe. PGD is highly associated with mortality and is increasingly treated with salvage ECMO. Though early mortality associated with salvage strategies is low, 1-year survival is significantly reduced. Given the increase in use of salvage ECMO, further work is needed on evaluating 2016 PGD definition.

Risk of primary graft dysfunction following lung transplantation in selected adults with connective tissue disease-associated interstitial lung disease

Previous studies have reported similarities in long-term outcomes following lung transplantation for connective tissue disease-associated interstitial lung disease (CTD-ILD) and idiopathic pulmonary fibrosis (IPF). However, it is unknown whether CTD-ILD patients are at increased risk of primary graft dysfunction (PGD), delays in extubation, or longer index hospitalizations following transplant compared to IPF patients. We performed a multicenter retrospective cohort study of CTD-ILD and IPF patients enrolled in the Lung Transplant Outcomes Group registry who underwent lung transplantation between 2012 and 2018. We utilized mixed effects logistic regression and stratified Cox proportional hazards regression to determine whether CTD-ILD was independently associated with increased risk for grade 3 PGD or delays in post-transplant extubation and hospital discharge compared to IPF. A total of 32.7% (33/101) of patients with CTD-ILD and 28.9% (145/501) of patients with IPF developed grade 3 PGD 48-72 hours after transplant. There were no significant differences in odds of grade 3 PGD among patients with CTD-ILD compared to those with IPF (adjusted OR 1.12, 95% CI 0.64-1.97, p = 0.69), nor was CTD-ILD independently associated with a longer post-transplant time to extubation (adjusted HR for first extubation 0.87, 95% CI 0.66-1.13, p = 0.30). However, CTD-ILD was independently associated with a longer post-transplant hospital length of stay (median 23 days [IQR 14-35 days] vs17 days [IQR 12-28 days], adjusted HR for hospital discharge 0.68, 95% CI 0.51-0.90, p = 0.008). Patients with CTD-ILD experienced significantly longer postoperative hospitalizations compared to IPF patients without an increased risk of grade 3 PGD.

4167 Peri-transplant Lung Microbiome Reveal Oral Bacteria, Pepsin And Inflammatory Markers Co-associate With Primary Graft Dysfunction, Implicating Aspiration As A Potential Contributor

OBJECTIVES/GOALS: Primary graft dysfunction (PGD) is acute lung injury in the first three days after lung transplant. Patients that experience PGD have increased mortality and an increased risk of chronic lung allograft dysfunction. The pathogenesis is thought to be an ischemia-reperfusion injury but is incompletely understood and there are no specific therapies. We investigated the role of the microbiome in PGD and associations with inflammation and markers of aspiration. METHODS/STUDY POPULATION: We collected airway lavage samples from lung transplant donors before procurement and recipients after reperfusion. We extracted DNA, amplified the bacterial 16S rRNA gene, and sequenced on the Illumina MiSeq platform. QIIME2 and Deblur were used for bioinformatic analysis. R packages were used for downstream analysis and visualizations. The host response was quantified using the Milipore 41-plex Luminex and an ELISA for pepsin. Clinical data was collected by the Penn Lung Transplant Outcomes Group. PGD was assessed by degree of hypoxemia and chest X-ray findings in the 72 hours after transplant. RESULTS/ANTICIPATED RESULTS: There was no significant difference in alpha diversity (Shannon index, p = 0.51), biomass (via comparison of 16S amplicon PicoGreen, p = 0.6), or beta diversity (Weighted UniFrac, p = 0.472, PERMANOVA) between subjects with PGD grade 3 (n = 36) and those that did not (n = 96). On taxonomic analysis, we found an enrichment of Prevotella in donor and recipient lungs that went on to develop PGD (p = 0.05). To follow up this finding we measured immune response and pepsin concentrations in recipient lungs. We found elevated levels in 35/41 cytokines measured in subjects that developed PGD as well as an elevation in pepsin and a correlation between pepsin concentration and Prevotella relative abundance (Figure 1). Additionally, Prevotella relative abundance had statistically significant positive correlations with multiple cytokines such as IL-6 (Pearson’s = 0.26, p = 0.009) and eotaxin (Pearson’s = 0.24, p = 0.016). DISCUSSION/SIGNIFICANCE OF IMPACT: There is an enrichment of oral anerobes in lung allografts that eventually develop PGD. This is associated with elevated levels of pepsin and markers of inflammation. These lines of evidence suggest aspiration contributes to priming the allograft for PGD.

Implications of ECMO Bridging and Salvage Strategies on Mortality and PGD

ECMO is increasingly used for bridging and salvage therapies in lung transplantation, with favorable short-term results. Mid- to long-term outcomes of ECMO use for bridging and salvage are incompletely understood, as is effect on PGD risk; therefore, we sought to define the effects of these strategies on mortality and PGD. The Lung Transplant Outcomes Group study is a multi-center prospective cohort study designed to identify risk factors for PGD and mortality. Patients were enrolled from August 2011 to June 2018. The effect of pre-operative (bridging) and post-operative (salvage) ECMO on Grade 3 PGD incidence and long-term survival were assessed using time-to-event analyses adjusted for center. 1,537 subjects were enrolled with a 17.0% incidence of PGD on day 3 and an 18.9% mortality overall. PGD was associated with mortality (p=0.0001, Fig. 1a). ECMO bridging and salvage strategies increased over time (Fig. 1b). 138 (9%) subjects had bridging ECMO and 275 (17.9%) had salvage ECMO. PGD was associated with bridging strategies (p=0.001). PGD incidence in bridged patients (50.7%) exceeded non-bridged (42.2%). Bridging was not associated with mortality overall (p=0.70, Fig. 1c); however, if PGD developed after transplant using a bridging strategy, there was a significant increase in mortality (HR 1.8 [1.3; 2.61]; p=0.0007). About 45% of patients bridged with ECMO required salvage after transplant. ECMO use for salvage was highly associated with mortality (HR 2.1 [1.6; 2.8]; p<0.0001, Fig. 1d). Use of the ISHLT Revised definition identifies Grade 3 PGD as highly associated with mortality in the ECMO bridging and salvage era. ECMO use is increasing for both bridging and salvage strategies. ECMO bridging strategies do not seem to increase mortality in lung transplant patients unless Grade 3 PGD subsequently develops. ECMO salvage after transplant is associated with increased risk of mortality; however, it is likely used only in the severest cases, thus indication bias is likely present.

Dectin-1 genetic deficiency predicts chronic lung allograft dysfunction and death.

BACKGROUNDInnate immune activation impacts lung transplant outcomes. Dectin-1 is an innate receptor important for pathogen recognition. We hypothesized that genotypes reducing dectin-1 activity would be associated with infection, graft dysfunction, and death in lung transplant recipients.METHODSWe assessed the rs16910526 CLEC7A gene polymorphism Y238X, which results in dectin-1 truncation, in 321 lung allograft recipients at a single institution and in 1,129 lung allograft recipients in the multicenter Lung Transplant Outcomes Group (LTOG) cohort. Differences in dectin-1 mRNA, cytokines, protein levels, immunophenotypes, and clinical factors were assessed.RESULTSY238X carriers had decreased dectin-1 mRNA expression (P = 0.0001), decreased soluble dectin-1 protein concentrations in bronchoalveolar lavage (P = 0.008) and plasma (P = 0.04), and decreased monocyte surface dectin-1 (P = 0.01) compared with wild-type subjects. Y238X carriers had an increased risk of fungal pathogens (HR 1.17, CI 1.0-1.4), an increased risk of graft dysfunction or death (HR 1.6, CI 1.0-2.6), as well increased mortality in the UCSF cohort (HR 1.8, CI 1.1-3.8) and in the LTOG cohort (HR 1.3, CI 1.1-1.6), compared with wild-type CLEC7A subjects.CONCLUSIONIncreased rates of graft dysfunction and death associated with this dectin-1 polymorphism may be amplified by immunosuppression that drives higher fungal burden from compromised pathogen recognition.FUNDINGThe UCSF Nina Ireland Program for Lung Health Innovative Grant program, the Clinical Sciences Research & Development Service of the VA Office of Research and Development, and the Joel D. Cooper Career Development Award from the International Society for Heart and Lung Transplantation.

Collagen type-V is a danger signal associated with primary graft dysfunction in lung transplantation

BackgroundPrimary graft dysfunction (PGD) is the leading cause of early mortality after lung transplantation. Anti-collagen type-V (col(V)) immunity has been observed in animal models of ischemia-reperfusion injury (IRI) and in PGD. We hypothesized that collagen type-V is an innate danger signal contributing to PGD pathogenesis. MethodsAnti-col(V) antibody production was detected by flow cytometric assay following cultures of murine CD19+ splenic cells with col.(V). Responding murine B cells were phenotyped using surface markers. RNA-Seq analysis was performed on murine CD19+ cells. Levels of anti-col(V) antibodies were measured in 188 recipients from the Lung Transplant Outcomes Group (LTOG) after transplantation. ResultsCol(V) induced rapid production of anti-col(V) antibodies from murine CD19+ B cells. Subtype analysis demonstrated innate B-1 B cells bound col.(V). Col(V) induced a specific transcriptional signature in CD19+ B cells with similarities to, yet distinct from, B cell receptor (BCR) stimulation. Rapid de novo production of anti-col(V) Abs was associated with an increased incidence of clinical PGD after lung transplant. ConclusionsThis study demonstrated that col.(V) is an rapidly recognized by B cells and has specific transcriptional signature. In lung transplants recipients the rapid seroconversion to anti-col(V) Ab is linked to increased risk of grade 3 PGD.

Reactive Oxygen Species activate the NLRP3 Inflammasome in a model of lung transplant

BackgroundLung transplant involves a period of storage (ischemia) followed by the transplant (reattachment or reperfusion) event. The resultant ischemia‐reperfusion (I/R) injury, clinically known as primary graft dysfunction (PGD), is the most common cause for post‐transplant failure. Indeed, studies have shown that the poor outcome of lung transplant is primarily due to PGD that drives morbidity and mortality in ~30% of lung transplant recipients. We showed earlier, that one of the pivotal events with lung I/R associated with transplant is the production of reactive oxygen species (ROS). We also showed that this ROS generation is not the result of hypoxia‐deoxygenation as the lung oxygen supply is not compromised with stop or restart of blood flow. ROS produced with lung I/R reflects “flow” sensitive endothelial signaling that triggers NADPH oxidase‐2 (NOX2) activation. We postulated that injury with transplant was caused due to ROS initiated inflammation signaling. Among the inflammatory moieties of interest to us was the NOD like receptor protein 3 (NLRP3 inflammasome), which has been reported to be a major cause of cell death with I/R in systemic organs via pathways that were anoxia/hypoxia dependent. Could NLRP3 be activated by normoxic lung I/R as well? To answer this, we investigated NLRP3 activation and the mechanism of its regulation with lung I/R. Our hypothesis was that NOX2 activated with I/R regulates the NLRP3 inflammasome which in turn is a major driver of graft injury (PGD).MethodsMice (wild type and NOX2 null) were subjected lung I/R by hilar clamp and NLRP3 inflammasome activation measured by monitoring the colocalization of NLRP3 with its adaptor molecule ASC. Lung Injury was monitored by indices such as lipid peroxidation, isoprostanes and lung wet to dry ratio. The correlation between NLRP3 and PGD in post‐transplant human subjects was assessed by monitoring plasma NLRP3 and PGD outcome (obtained from Lung Transplant Outcomes Group Database).ResultsWe observed a ROS dependent increase in NLRP3 activation post lung I/R. We also found that NLRP3 blockade significantly reduced lung injury. Additionally, post‐transplant (human) recipients with detectable NLRP3 protein in plasma developed PGD.ConclusionThe NLRP3 inflammasome is regulated via NOX2 induced ROS production and plays a crucial role in injury with I/R. It can thus be considered as a risk factor with PGD.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Risk Factors for Primary Graft Dysfunction in Patients with Cystic Fibrosis Receiving Lung Transplants

Purpose The primary driver of poor outcomes in the early stages of lung transplantation is primary graft dysfunction (PGD). Patients with cystic fibrosis (CF) have unique physiology and demographics compared to other lung transplant recipients. Therefore, we sought to identify risk factors for PGD in the CF patient population undergoing lung transplantation. Methods We utilized clinical data on lung transplant recipients with CF and their donors from the Lung Transplant Outcomes Group cohort, a multi-center prospective cohort study of PGD pathogenesis. The primary outcome was grade 3 PGD within the first 72 hours after transplantation. Potential covariates were identified in univariate analysis and assessed for collinearity. Independent PGD risk factors were identified using multivariate logistic regression. A sensitivity analysis was performed using grade 3 PGD 48 to 72 hours after transplantation. Results We identified 195 patients with CF who received lung transplants between August 2014 and June 2018 across ten centers. Grade 3 PGD developed in 80 subjects (41%). Risk factors for PGD in CF patients based on the multivariable model were white donor race (odds ratio [OR]: 2.6, 95% confidence interval [CI]: 1.4-5.1), any positive panel reactive antibodies (PRA) (OR: 2.2, 95% CI: 1.0-4.7), recipient female gender (OR: 2.1, 95% CI: 1.1-3.9), intraoperative cardiopulmonary bypass use (OR: 2.2, 95% CI: 1.2-4.2), increasing lung allocation score (LAS) (OR: 1.2 per 10 point increase in LAS, 95% CI: 1.0-1.4), and ECMO (extracorporeal membrane oxygenation) bridge to transplant (OR: 2.7, 95% CI: 1.1-6.7). LAS and ECMO were assessed in separate models due to their collinearity. Mean pulmonary artery pressure at the time of transplant was included as a potential confounder. Similar findings were seen in a more severe phenotype of PGD that developed 48 to 72 hours after transplant. Conclusion The CF population is often considered to be at low risk of PGD, however we observed a relatively high rate of PGD in this study. Any positive PRA, female recipient gender, intraoperative bypass, increasing LAS, and ECMO are PGD risk factors that have been identified non-CF transplant populations. We validated these risk factors in recipients with CF. White donor race is a novel risk factor that has not been previously identified in lung transplant recipients with another primary diagnosis.

Incidence, risk factors, and clinical implications of post-operative delirium in lung transplant recipients

Delirium significantly affects post-operative outcomes, but the incidence, risk factors, and long-term impact of delirium in lung transplant recipients have not been well studied. We analyzed 155 lung transplant recipients enrolled in the Lung Transplant Outcomes Group (LTOG) cohort at a single center. We determined delirium incidence by structured chart review, identified risk factors for delirium, determined whether plasma concentrations of 2 cerebral injury markers (neuron-specific enolase [NSE] and glial fibrillary acidic protein [GFAP]) were associated with delirium, and determined the association of post-operative delirium with 1-year survival. Fifty-seven (36.8%) patients developed post-operative delirium. Independent risk factors for delirium included pre-transplant benzodiazepine prescription (relative risk [RR] 1.82; 95% confidence interval [CI] 1.08 to 3.07; p = 0.025), total ischemic time (RR 1.10 per 30-minute increase; 95% CI 1.01 to 1.21; p = 0.027), duration of time with intra-operative mean arterial pressure <60 mm Hg (RR 1.07 per 15-minute increase; 95% CI 1.00 to 1.14; p = 0.041), and Grade 3 primary graft dysfunction (RR 2.13; 95% CI 1.27 to 3.58; p = 0.004). Ninety-one (58.7%) patients had plasma available at 24 hours. Plasma GFAP was inconsistently detected, whereas NSE was universally detectable, with higher NSE concentrations associated with delirium (risk difference 15.1% comparing 75th and 25th percentiles; 95% CI 2.5 to 27.7; p = 0.026). One-year mortality appeared higher among delirious patients, 12.3% compared with 7.1%, but the difference was not significant (p = 0.28). Post-operative delirium is common in lung transplant recipients, and several potentially modifiable risk factors deserve further study to determine their associated mechanisms and predictive values.

Quantitative Evidence for Revising the Definition of Primary Graft Dysfunction after Lung Transplant.

Primary graft dysfunction (PGD) is a form of acute lung injury that occurs after lung transplantation. The definition of PGD was standardized in 2005. Since that time, clinical practice has evolved, and this definition is increasingly used as a primary endpoint for clinical trials; therefore, validation is warranted. We sought to determine whether refinements to the 2005 consensus definition could further improve construct validity. Data from the Lung Transplant Outcomes Group multicenter cohort were used to compare variations on the PGD definition, including alternate oxygenation thresholds, inclusion of additional severity groups, and effects of procedure type and mechanical ventilation. Convergent and divergent validity were compared for mortality prediction and concurrent lung injury biomarker discrimination. A total of 1,179 subjects from 10 centers were enrolled from 2007 to 2012. Median length of follow-up was 4 years (interquartile range = 2.4-5.9). No mortality differences were noted between no PGD (grade 0) and mild PGD (grade 1). Significantly better mortality discrimination was evident for all definitions using later time points (48, 72, or 48-72 hours; P < 0.001). Biomarker divergent discrimination was superior when collapsing grades 0 and 1. Additional severity grades, use of mechanical ventilation, and transplant procedure type had minimal or no effect on mortality or biomarker discrimination. The PGD consensus definition can be simplified by combining lower PGD grades. Construct validity of grading was present regardless of transplant procedure type or use of mechanical ventilation. Additional severity categories had minimal impact on mortality or biomarker discrimination.

Clinical Risk Factors and Prognostic Model for Primary Graft Dysfunction after Lung Transplantation in Patients with Pulmonary Hypertension.

Pulmonary hypertension from pulmonary arterial hypertension or parenchymal lung disease is associated with an increased risk for primary graft dysfunction after lung transplantation. We evaluated the clinical determinants of severe primary graft dysfunction in pulmonary hypertension and developed and validated a prognostic model. We conducted a retrospective cohort study of patients in the multicenter Lung Transplant Outcomes Group with pulmonary hypertension at transplant listing. Severe primary graft dysfunction was defined as PaO2/FiO2 ≤200 with allograft infiltrates at 48 or 72 hours after transplantation. Donor, recipient, and operative characteristics were evaluated in a multivariable explanatory model. A prognostic model derived using donor and recipient characteristics was then validated in a separate cohort. In the explanatory model of 826 patients with pulmonary hypertension, donor tobacco smoke exposure, higher recipient body mass index, female sex, listing mean pulmonary artery pressure, right atrial pressure and creatinine at transplant, cardiopulmonary bypass use, transfusion volume, and reperfusion fraction of inspired oxygen were associated with primary graft dysfunction. Donor obesity was associated with a lower risk for primary graft dysfunction. Using a 20% threshold for elevated risk, the prognostic model had good negative predictive value in both derivation and validation cohorts (89.1% [95% confidence interval, 85.3-92.8] and 83.3% [95% confidence interval, 78.5-88.2], respectively), but low positive predictive value. Several recipient, donor, and operative characteristics were associated with severe primary graft dysfunction in patients with pulmonary hypertension, including several risk factors not identified in the overall transplant population. A prognostic model with donor and recipient clinical risk factors alone had low positive predictive value, but high negative predictive value, to rule out high risk for primary graft dysfunction.

Diastolic Dysfunction Increases the Risk of Primary Graft Dysfunction after Lung Transplant.

Primary graft dysfunction (PGD) is a significant cause of early morbidity and mortality after lung transplant and is characterized by severe hypoxemia and infiltrates in the allograft. The pathogenesis of PGD involves ischemia-reperfusion injury. However, subclinical increases in pulmonary venous pressure due to left ventricular diastolic dysfunction may contribute by exacerbating capillary leak. To determine whether a higher ratio of early mitral inflow velocity (E) to early diastolic mitral annular velocity (é), indicative of worse left ventricular diastolic function, is associated with a higher risk of PGD. We performed a retrospective cohort study of patients in the Lung Transplant Outcomes Group who underwent bilateral lung transplant at our institution between 2004 and 2014 for interstitial lung disease, chronic obstructive pulmonary disease, or pulmonary arterial hypertension. Transthoracic echocardiograms obtained during evaluation for transplant listing were analyzed for E/é and other measures of diastolic function. PGD was defined as PaO2/FiO2 less than or equal to 200 with allograft infiltrates at 48 or 72 hours after reperfusion. The association between E/é and PGD was assessed with multivariable logistic regression. After adjustment for recipient age, body mass index, mean pulmonary arterial pressure, and pretransplant diagnosis, higher E/é and E/é greater than 8 were associated with an increased risk of PGD (E/é odds ratio, 1.93; 95% confidence interval, 1.02-3.64; P = 0.04; E/é >8 odds ratio, 5.29; 95% confidence interval, 1.40-20.01; P = 0.01). Differences in left ventricular diastolic function may contribute to the development of PGD. Future trials are needed to determine whether optimization of left ventricular diastolic function reduces the risk of PGD.

The relationship between plasma lipid peroxidation products and primary graft dysfunction after lung transplantation is modified by donor smoking and reperfusion hyperoxia

Donor smoking history and higher fraction of inspired oxygen (FIO2) at reperfusion are associated with primary graft dysfunction (PGD) after lung transplantation. We hypothesized that oxidative injury biomarkers would be elevated in PGD, with higher levels associated with donor exposure to cigarette smoke and recipient hyperoxia at reperfusion. We performed a nested case-control study of 72 lung transplant recipients from the Lung Transplant Outcomes Group cohort. Using mass spectroscopy, F2-isoprostanes and isofurans were measured in plasma collected after transplantation. Cases were defined in 2 ways: grade 3 PGD present at day 2 or day 3 after reperfusion (severe PGD) or any grade 3 PGD (any PGD). There were 31 severe PGD cases with 41 controls and 35 any PGD cases with 37 controls. Plasma F2-isoprostane levels were higher in severe PGD cases compared with controls (28.6 pg/ml vs 19.8 pg/ml, p = 0.03). Plasma F2-isoprostane levels were higher in severe PGD cases compared with controls (29.6 pg/ml vs 19.0 pg/ml, p = 0.03) among patients reperfused with FIO2 >40%. Among recipients of lungs from donors with smoke exposure, plasma F2-isoprostane (38.2 pg/ml vs 22.5 pg/ml, p = 0.046) and isofuran (66.9 pg/ml vs 34.6 pg/ml, p = 0.046) levels were higher in severe PGD compared with control subjects. Plasma levels of lipid peroxidation products are higher in patients with severe PGD, in recipients of lungs from donors with smoke exposure, and in recipients exposed to higher Fio2 at reperfusion. Oxidative injury is an important mechanism of PGD and may be magnified by donor exposure to cigarette smoke and hyperoxia at reperfusion.