Report of the ISHLT Working Group on Primary Lung Graft Dysfunction, part I: Definition and grading-A 2016 Consensus Group statement of the International Society for Heart and Lung Transplantation. J Heart Lung Transplant. 2017;36:1097-1103. [PMID: 28942784 DOI: 10.1016/j.healun.2017.07.021]

Outcomes of controlled DCDD lung transplantation after thoraco-abdominal vs abdominal normothermic regional perfusion: The Spanish experience

BACKGROUND

Thoraco-abdominal normothermic regional perfusion (TA-NRP) has emerged as a strategy for evaluating and recovering the heart in controlled donation after the circulatory determination of death (cDCDD). However, its impact on lung grafts remains largely unknown. We aimed to assess the impact of TA-NRP on the outcomes of recipients of cDCDD lungs.

METHODS

This is a retrospective, multicenter, nationwide study describing the outcomes of cDCDD lung transplants (LTs) performed in Spain from January 2021 to November 2023. Patients were divided in 2 groups based on the recovery technique: TA-NRP with the simultaneous recovery of the heart vs abdominal NRP (A-NRP) without simultaneous heart recovery. The primary endpoint was the incidence of Primary Graft Dysfunction (PGD) grade 3 at 72 hours. Secondary endpoints included the overall incidence of PGD, days on mechanical ventilation, intensive care unit (ICU) and hospital length of stay, early survival rates, and mid-term outcomes.

RESULTS

Two hundred and eighty three cDCDD LTs were performed during the study period, 28 (10%) using TA-NRP and 255 (90%) using A-NRP. No differences were observed in the incidence of PGD grade 3 at 72 hours between the TA-NRP and the A-NRP group (0% vs 7.6%; p = 0.231), though the overall incidence of PGD was significantly lower with TA-NRP (14.3% vs 41.5%; p = 0.005). We found no significant differences between the groups regarding other post-transplant outcome variables.

CONCLUSIONS

TA-NRP allows the simultaneous recovery of both the heart and the lungs in the cDCDD scenario with appropriate LT outcomes comparable to those observed with the A-NRP approach.

Key predictors of long-term survival after lung transplantation in Japan

BACKGROUND

Lung transplantation (LTx) is essential for treating end-stage lung diseases in Japan, achieving favorable long-term survival despite donor shortages. However, factors associated with long-term survival after transplantation remain unclear. This study aims to identify key predictors influencing post-transplant outcomes.

METHODS

A retrospective analysis was conducted on LTx recipients at Tohoku University Hospital from 2000 to 2019, with a follow-up period of five years to 2024. Recipients were categorized into short survivors (<5 years) and long survivors (≥5 years). The analysis focused on recipient demographics, donor characteristics, surgical factors, and post-transplant outcomes.

RESULTS

Of 124 recipients, 36 were short survivors, and 88 were long survivors. Long-term survivors were younger, with a lower prevalence of patients aged 55 years and older. Additionally, fewer long-term survivors received lungs from critically marginal donors compared to short-term survivors. CMV serology was a significant factor, with a higher incidence of CMV disease observed in short-term survivors.

CONCLUSION

The study identified younger age, selective donor use, and CMV status as key predictors associated with long-term survival after LTx in Japan. The findings underscore the importance of targeted CMV management strategies and suggest that future multicenter studies with larger, more diverse populations are needed to confirm these results and further enhance long-term survival outcomes.

Lung Transplantation From Donors With a History of Substance Use

BACKGROUND

Substance use is common among lung transplant donors, but concerns persist about graft damage. Stimulant drugs such as cocaine and methamphetamine can induce pulmonary arterial hypertension, while smoked products such as cannabis and crack cocaine can produce airway and parenchymal diseases. We sought to characterize donor substance use at our center and evaluate the associations with recipient survival as well as chronic lung allograft dysfunction (CLAD), severe primary graft dysfunction (PGD3), and baseline lung allograft dysfunction (BLAD).

METHODS

We studied patients with double lung transplants in our program between 2004 and 2016, including a history of donor substance use with nine pre-specified agents. We modeled the association with time to death or retransplant, CLAD, severe PGD, and BLAD.

RESULTS

Of 473 recipients, 186 (39%) received lungs from a donor with a history of substance use with at least one of the pre-specified substances. There was no overall relationship between donor substance use and any outcome. Heavy donor smoking was associated with an increased risk of death or retransplant (hazard ratio 1.47; p = 0.032), PGD3 (odds ratio [OR]: 2.13; p = 0.014), and BLAD (OR 2.56; p < 0.001). Donor crack cocaine use (n = 24) was also associated with worse survival (HR 2.16; 95% CI 1.16-3.66; p = 0.017) but not CLAD or BLAD. We noted no CLAD associations with any drug.

CONCLUSION

A history of donor substance use was common and in general not associated with worse outcomes, aside from heavy donor smoking. These findings may have implications for allocation and post-transplant graft dysfunction.

Allogeneic mesenchymal stromal cell therapy on primary graft dysfunction after lung transplantation

Background

Primary graft dysfunction (PGD) is common in lung transplantation affecting 15-30% of recipients. It represents a multifactorial injury to the transplanted lung within the first 72 hours after transplantation.We aimed to investigate clinical safety and efficacy of allogeneic adipose tissue-derived stromal cells (ASCs), as an add-on therapy in patients undergoing double lung transplantation.

Methods

Single center, double-blinded, investigator-initiated randomized phase I/II study with intravenous infusion of either ASCs or placebo within two hours after lung transplantation. A total of 31 patients were included and randomized 1:1:1 to either 200 million or 100 million ASCs, or placebo infusion.The primary endpoint was difference in PGD grade 72 hours after transplantation between groups.

Results

No significant differences in PGD were seen between the 3 groups 72 hours after lung transplantation (P=0.426). Combined ASC groups compared to placebo group did not show any difference in PGD 72 hours after transplantation (P=0.252). A reduced progression in PGD from day 1 to day 3 and day 2 to day 3 was observed between the ASC treated patients and patients in the placebo group (P=0.034 and P=0.034, respectively). There were no significant differences in number of serious adverse events or in secondary endpoints such as kidney function, lung function, or quality-of-life between groups.

Conclusions

Intravenous infusion of allogeneic ASCs in patients immediately after double lung transplantation was safe. The therapy did not show statistic difference in PGD between groups 72 hours after lung transplantation.

Clinical trial registration information

EudraCT number 2019-004848-30 and NCT04714801.

Lower tidal volume ventilation post-bilateral lung transplantation is associated with ventilator-free days

BACKGROUND

There is limited evidence regarding the effect of invasive mechanical ventilation practice post-bilateral lung transplantation. Invasive mechanical ventilation practice may be associated with prolonged ventilation, particularly when referenced to donor anthropometrics.

METHODS

This was a single-centre retrospective cohort study that included consecutive adult bilateral lung transplant recipients between 2015 and 2021 who were ventilated for a minimum of 24 h post-surgery. Lower and higher tidal volume sub-groups were defined for mean and maximum values indexed to both donor and recipient predicted body weight over the first 72 h. The primary outcome was ventilator-free days in the first 28 days, and this was analysed using the Wilcoxon rank sum test and a competing risks regression. We used a Cox proportional hazards model to examine the relationship of ventilator-free days and tidal volume and 90-day survival.

RESULTS

The cohort included 111 recipients, and the median ventilator-free days for the entire cohort was 25 (21-26). Lower tidal volume indexed to donor predicted body weight after 48 and 72 h was associated with more ventilator-free days (25 (23-26) vs. 24 (17-26), p = .04 and 24 (21-25) vs. 20 (14-24), p = .02) and increased cumulative incidence of successful extubation (sub-distribution hazard ratio 1.54 (1.07-2.20), p = .02 and SHR 1.87 (1.07-3.27), p = .03). Ventilator-free days and lower tidal volume were associated with increased 90-day survival.

CONCLUSIONS

Lower tidal volume ventilation indexed to donor predicted body weight is associated with more ventilator-free days post-bilateral lung transplantation.

EDITORIAL COMMENT

Postoperative ventilation with lower tidal volume indexed to the donor's predicted body weight was associated with more ventilator-free days in patients undergoing bilateral lung transplantation. No difference was found between lower versus higher tidal volume ventilation for other patient-important outcomes. The results highlight the need for larger prospective clinical trials.

Activation of anti-donor CD8 alloimmune response in clinically diagnosed acute rejection early after living-donor lobar lung transplantation and its impact on outcome

BACKGROUND

The characteristics and prognostic impacts of early graft infiltration after lung transplantation and clinically diagnosed acute rejection remain unclear. Furthermore, the alloimmune response status in lung transplantation remains uninvestigated.

METHODS

In this retrospective cohort study, we evaluated 92 living-donor lobar lung transplantations (LDLLT) to establish the effect of graft infiltration-diagnosed as acute rejection-within one-month post-transplantation (cAR), on chronic lung allograft dysfunction (CLAD)-free LDLLT survival. The alloimmune response was evaluated using the carboxyfluorescein diacetate succinimidyl ester (CFSE)-mixed lymphocyte reaction (MLR) in lymphocytes isolated from donor and recipient blood one week after LDLLT. The anti-donor proliferation of CD4+ and CD8+ T cells was determined using flow cytometry.

RESULTS

cAR was observed in 54 (58.7 %) patients who underwent LDLLT. The median postoperative day of cAR occurrence was 7 days (ranging between 5 and 28 days). Only one episode of cAR occurred in 51 patients (94.4 %). CLAD-free survival was significantly lower in patients who underwent cAR, especially within 2 years after LDLLT (p = 0.016). Thirteen CFSE-MLR assays were performed in seven consecutive LDLLT cases (six bilateral and one unilateral LDLLT). Increased anti-donor proliferation of CD8+ T cells, but not CD4+ T cells, was associated with cAR, irrespective of human leukocyte antigen (HLA) class I mismatch.

CONCLUSION

Early lung graft infiltration after LDLLT increases the risk of the early development of CALD. Augmented anti-donor CD8 + response was also associated with graft infiltration, which could not be predicted from HLA mismatches but could be monitored using MLR in LDLLT.

Outcomes of Donor/Recipient Size-mismatched Lung Transplantation

BACKGROUND

Donor/recipient (D/R) size matching is crucial to achieve proper organ allocation and outcome for lung transplantation (LT). However, studies in this regard have not shown consistent results. We analyzed the results of size-mismatched LT focusing on primary graft dysfunction (PGD) and survival.

METHODS

A total of 446 patients underwent LT between January 2010 and December 2022. After exclusion, the patients were divided into 3 groups according to the donor/recipient size; D/R ratio >120% was grouped as Over (n = 87), 120%≥D/R ratio≥80% was grouped as Normal (n = 271), 80%>D/R was grouped as Under (n = 19). Early and long-term outcomes were analyzed.

RESULTS

Recipient height, weight, and proportion of male were the highest in the Under group, followed by the Normal and Over groups (P < 0.001). The ratio of extracorporeal membrane oxygenation weaning in the operating room was highest in the Under group, followed by the Normal and Over groups (P : 0.04). The proportions of PGD grade 3 within 48 h and 72 h were highest in the Over group, followed by the Normal and Under groups (P : 0.007 and 0.016, respectively). There was no statistical difference in the pulmonary function test results between the groups at 12 months postoperative follow-up. The 5-year survival rate did not differ among the groups (60.9% vs 56.8% vs 54.7%, Under vs Normal vs Over, P : 0.833) CONCLUSIONS: Although oversized D/R-matched LT demonstrated late recovery during the early postoperative period, their long-term results were non-inferior in terms of the D/R size ratio.

Post Lung Transplant Primary Graft Dysfunction

Primary graft dysfunction (PGD) is a major source of morbidity and mortality following lung transplantation, presenting as acute lung injury within 72 hours post-transplantation. Despite advances in surgical techniques and perioperative care, the complex interplay of donor, recipient, and perioperative factors contributes to its development, underscoring the multifactorial nature of PGD. Clinical management of recipients with PGD relies on supportive care strategies, including lung-protective ventilation, inhaled nitric oxide, and extracorporeal membrane oxygenation (ECMO). Severe cases of PGD may result in significant short- and long-term adverse outcomes, including early mortality. Even for patients who recover from PGD, there is also an associated increased risk of chronic lung allograft dysfunction, further compounding its clinical impact. This review provides a brief review of current knowledge regarding PGD, detailing risk factors, diagnostic criteria, and management approaches while identifying critical gaps in understanding its pathophysiology. Ongoing research is essential to develop innovative therapeutic strategies and improve outcomes for lung transplant recipients.

The Spectrum of Mitral Regurgitation in Lung Transplant Recipients: A Systematic Review

Mitral regurgitation (MR) in lung transplant (LTx) recipients is a rare but complex cardiopulmonary phenomenon. The overlap between symptoms of MR and post-LTx complications, such as primary graft dysfunction, complicates its diagnosis and management. This systematic review aims to characterize the incidence, pathophysiology, presentation, and management of MR in LTx patients. We conducted a literature search in PubMed, Web of Science, Scopus, and Embase. The search yielded 133 studies, of which 11 were included. Data regarding MR development, clinical presentation, echocardiographic findings, and management strategies were extracted and analyzed. Perioperative MR, occurring during or immediately post-LTx, was frequently attributed to the systolic anterior motion of the mitral valve (MV) occurring in the setting of hypovolemia and/or inotrope usage. Later postoperative MR, on the other hand, was associated with reverse ventricular remodeling and mitral annular dilation, although some variability in the literature was present. Preexisting MR or ventricular dysfunction, elongated MV leaflets, and bilateral LTx procedure appeared to be risk factors for MR development. Management was dependent on the timing of MR and its pathophysiology, where systolic anterior motion-related MR was treated with medical therapy, whereas postoperative MR often required MV interventions. In conclusion, the diagnosis of MR in LTx patients is complicated by its symptomatic overlap with other post-LTx complications. Echocardiographic monitoring in patients with preexisting MR, regardless of severity, is essential for early identification and management. Further research is needed to better understand the underlying mechanisms and refine management strategies for MR in this population.

Computed Tomography-Based Body Composition is Related to Perioperative Morbidity in Older Lung Transplant Recipients

BACKGROUND

 In older patients, a limited physical reserve is considered a contraindication for lung transplantation (LTx). Herein, we aimed to establish a computed tomography (CT)-based quantification of physical reserve in older patients scheduled for transplantation.

METHODS

 This retrospective study included patients older than 60 years who received LTx. Semiautomatic measurements of the mediastinal fat area and the dorsal muscle group area in pretransplantation CT scans were performed, and normalized data were correlated with clinical parameters.

RESULTS

 Patients (n = 108) were assigned into three groups (Musclehighfatlow [n = 25], Musclelowfathigh [n = 24], and other combinations [n = 59]). The Musclelowfathigh group had a significantly increased risk of wound infections (p = 0.002) and tracheostomy (p = 0.001) compared with Musclehighfatlow patients. The median length of intensive care unit stay (25 vs. 3.5 days; p = 0.002) and the median length of hospital stay (44 vs. 22.5 days; p = 0.013) post-LTx were significantly prolonged in the Musclelowfathigh group. Significantly more patients in this group had a prolonged ventilation time (11 vs. 0; p < 0.001).

CONCLUSION

 Body composition parameters determined in pretransplant chest CT scans in older LTx candidates might aid in identifying high-risk patients with a worse perioperative outcome after LTx.

Post-lung transplant outcomes of connective tissue disease-related interstitial lung diseases compared with idiopathic interstitial pneumonia: a single-center experience in Japan

OBJECTIVES

The aim of this study was to investigate the outcomes of lung transplantation for connective tissue disease-related interstitial lung disease (CTD-ILD) conducted at our institution, compared with those for idiopathic interstitial pneumonias (IIPs).

METHODS

We retrospectively reviewed patients with CTD-ILD and IIPs who underwent lung transplantation at our hospital from July 2015 to October 2023. We compared patients' backgrounds, early complications within 28 days post-transplant (CTCAE grade 3 or higher), postoperative courses, and prognoses between the two groups.

RESULTS

The CTD-ILD group (n = 19) and the IIPs group (n = 56) were compared. The CTD-ILD group had significantly higher preoperative use of corticosteroids and antifibrotic agents, mean pulmonary arterial pressure, anti-human leukocyte antigen antibody positivity, and donor age (p < 0.05). In addition, the CTD-ILD group had significantly longer operation times (579.0 vs 442.5 min), longer stays in the intensive care unit (17.0 vs 9.0 days) and hospital (58.0 vs 44.0 days); required more tracheostomies (57.9 vs 25.0%); and experienced more respiratory (52.6 vs 25.0%) and gastrointestinal (42.1 vs 8.9%) complications (p < 0.05). However, there were no significant differences in overall survival, nor chronic lung allograft dysfunction (CLAD)-free survival between the two groups.

CONCLUSION

Perioperative complications, notably respiratory and gastrointestinal complications, were prevalent after lung transplantation among CTD-ILD patients. Despite this, long-term survival rates were comparable to those observed in IIP cases.

Time on the waiting list is an independent risk factor for day-90 mortality after lung transplantation

BACKGROUND

The waitlist deaths of transplantation candidates based on their time on the waiting list (TWL) have already been studied, but the short-term mortality and early complications of lung transplant (LT) recipients based on their TWL have not been specifically studied. The first aim of this study was to assess the relationship between increased TWL and short-term mortality in LT recipients.

METHODS

In this observational, monocentric, retrospective study, all patients who underwent LT between January 2016 and August 2022 at Bichat Claude Bernard Hospital, Paris were analyzed. Univariate analysis (chi2 test, Mann-Whitney test, Fisher's exact test) and multivariate analysis (logistic regression) were performed. Ninety-days and one-year survival were studied (Kaplan-Meier curves, log-rank test). p < 0.05 indicated statistical significance.

RESULTS

242 LT patients were analyzed. The median TWL was 100 (43-229) days. Postoperative complications, including septic shock (36 versus 18%, p = 0.002), grade 3 primary graft dysfunction (31 versus 20%, p < 0.001), and KDIGO3 acute kidney injury (8 versus 25%, p < 0.001), were more common in the prolonged TWL (pTWL) group (>100 days) than in the short TWL group (≤100 days). The duration of hospitalization in the ICU was longer (18 [11-34] versus 13 [9-23] days, p = 0.02) in the pTWL group. According to our multivariate analysis, TWL was an independent risk factor for 90-days mortality (OR 1.02, 95% CI [1.00-1.04]; p = 0.032).

CONCLUSION

TWL was an independent risk factor for 90-days mortality after LT. Receiving LT after more than 100 days on the waitlist exposes to increased postoperative complications.

Feasibility and Safety of Ex Vivo Delivery of Rituximab to Lung Allografts in Transplant Recipients at High Risk for Epstein-Barr Virus-associated Posttransplant Lymphoproliferative Disorder

Background

Ex vivo lung perfusion (EVLP) offers a novel platform for delivering targeted therapies directly to donor lungs before transplantation, potentially reducing systemic side effects. Our study evaluated the feasibility and safety of rituximab delivery to donor lungs from Epstein-Barr virus (EBV)-seropositive donors for transplantation into EBV-seronegative recipients (D+/R-) to reduce the risk of EBV-associated posttransplant lymphoproliferative disorder (PTLD), which remains a major obstacle in the transplant setting.

Methods

A pilot study was conducted involving 5 EBV-seronegative lung transplant recipients. Donor lungs were perfused with 500 mg rituximab during EVLP for 3-4 h. Primary outcomes included safety and feasibility, assessed by monitoring lung function during perfusion, posttransplant complications, and graft dysfunction. Secondary outcomes included EBV DNAemia, PTLD incidence, peripheral B-cell frequencies, EBV blood transcripts, and rituximab serum levels.

Results

Rituximab delivery via EVLP was feasible and safe, with no significant deviations in lung function or adverse events linked to treatment. One patient experienced primary graft dysfunction. Peripheral B-cell counts were reduced immediately posttransplant and remained low in some patients, whereas others rebounded over the weeks posttransplant, and serum rituximab levels were undetectable after 2 wk. Three patients developed EBV DNAemia and 2 developed PTLD within 2 y, although PTLD lesions were not observed in transplanted lungs.

Conclusions

EVLP-based rituximab delivery is a feasible and promising strategy for targeting donor-transmitted EBV with minimal systemic exposure. Although the findings suggest potential clinical benefit, the development of PTLD in extrathoracic sites underscores the need for further optimization and larger studies to evaluate efficacy and refine the intervention.

The United Kingdom's experience of controlled donation after circulatory death direct procurement of lungs with concomitant abdominal normothermic regional perfusion with an analysis of short-term outcomes

BACKGROUND

Abdominal Normothermic Regional Perfusion (A-NRP) improves outcomes for transplanted abdominal organs from Donation after Circulatory Death (DCD) donors. Concerns have been raised about the effect of A-NRP on lungs procured during multi-organ donation. We present the UK experience of performing direct procurement (DRP) of lungs from DCD donors with A-NRP.

METHODS

Retrospective analysis of all 487 UK DCD lung donors between 1 April 2011 and 31 December 2023. Organ transplantation rate and30-day, 90-day and 1-year survival rates were compared between DRP of DCD lungs, DRP of DCD lungs with A-NRP and DBD lungs. PGD rates were compared between DCD lungs with and without A-NRP.

RESULTS

Three hundred ninety-seven DCD donors resulted in a lung transplant (22 retrieved by DRP with A-NRP). There was no difference in lung transplantation rates between DRP and DRP with A-NRP. Of the 390 first adult-only lung transplants performed from DCD donors, there was no significant difference in 30-day, 90-day and 1-year survival between DRP of DCD lungs and DRP with A-NRP. There was a significant difference in survival between standard DCD donors and DBD donors at 30-days and 90-days, but not 1 year. There was no significant difference in grade 3 PGD rates at 72 hours post-implantation for DCD lungs with or without A-NRP.

CONCLUSION

In the UK experience, use of A-NRP is not detrimental to procurement of DCD lungs. We advocate the use of this technique until further studies can explore the safety and efficacy of thoraco-abdominal NRP for lungs in multi-organ retrieval.

Extracorporeal membrane oxygenation after lung transplant: An ELSO registry analysis

BackgroundThe use of extracorporeal membrane oxygenation (ECMO) has expanded and is now widely applied to perioperative care in lung transplant. Respiratory failure after lung transplant is a clinical challenge where ECMO plays a critical role.MethodsThe Extracorporeal Life Support Organization registry was queried for patients 18 years and older who were treated with ECMO after lung transplant in 2010-2022. ECMO runs for more than 24 hours after lung transplant were included regardless of the timing of initiation. Univariable analyses were performed to compare procedural and patient characteristics across ECMO eras. Multivariable logistic regression was performed to identify predictors of surviving to discharge.ResultsOne-thousand nine-hundred and sixty-six patients met the inclusion criteria, and 1422 patients (72.3%) survived to discharge. The number of ECMO runs steadily increased throughout the study period, with a trend of improving survival. Higher annual center volume (Odds Ratio[OR]: 0.97, p < 0.001), longer ECMO duration (OR 1.01/day, p < 0.001), veno-arterial mode (OR 2.28, p < 0.001), initiation of ECMO >72 hours after transplant (OR 3.93, p < 0.001), and ventilator duration >5 days (1.55, p = 0.035) were associated with higher probability of survival to discharge.ConclusionsECMO after lung transplant has expanded over the last 12 years along with improved survival. The data suggest a potential benefit of early ECMO initiation in this patient population. High ECMO volume was associated with better outcomes, and expertise in ECMO is considered essential in lung transplant centers.

Exploring the Association Between Torquetenovirus Viral Load and Immunosuppressive Drug Exposure in Lung Transplantation

To improve lung transplant recipient (LungTx) outcome, it would be of great interest to measure the net state of immunosuppression to avoid both infection and rejection. Measurement of Torquetenovirus load (TTV load) has been proposed as a biomarker to monitor solid organ transplantation, but its relationship with immunosuppressive drugs, particularly mycophenolic acid (MPA), is not well understood. We performed a prospective study of 53 LungTx, measuring TTV load before transplantation, at week 3, and at month 3. Tacrolimus and MPA doses and levels were recorded, and an area under the MPA curve (AUC-MPA) was calculated at the third month. LungTx in the fourth quartile of TTV load at the third week and the third month exhibited a low risk of acute rejection (OR 0.113, 95% CI 0.013-0.953, p = 0.045) and a high risk of opportunistic infection from month 3 to 6 (OR 15.200, 95% CI 1.525-151.511, p = 0.020), respectively. TTV load was weakly related to tacrolimus trough level at month 3 (rho = 0.283, p = 0.040). Neither MPA blood levels nor AUC-MPA were related to TTV load, although only patients with a reduction in MPA dose from month 1 to 3 showed a smaller increase in TTV load (0.86, IQR 2.58 log10 copies/mL vs. 2.26, IQR 3.02 log10 copies/mL, p = 0.026). In conclusion, TTV load in LungTx is only partially related to exposure to immunosuppressive drugs. Other variables, such as inflammation, immunosenescence, and frailty, may influence the overall level of immunosuppression and TTV load.

Respiratory compliance related to prognostic of lung transplant patients with veno‑venous extracorporeal membrane oxygenation support

Veno-venous extracorporeal membrane oxygenation (VV-ECMO) plays an important role in the perioperative care of critically ill lung transplant patients. However, the factors predicting prognosis are unclear. This study assessed the association between static respiratory compliance (Crs) and outcomes of lung transplant patients receiving VV-ECMO in terms of 90-day mortality. Data were retrospectively collected for patients that underwent lung transplantation with VV-ECMO support during 2022-2023. Patients were divided into two groups according to the early postoperative Crs: lower Crs (Crs < 25 ml/cmH2O) and higher Crs (Crs ≥ 25 ml/cmH2O). Differences in patient characteristics and prognosis were then compared between the two groups. Receiver operating characteristic (ROC) curve analysis was used to evaluate the value of Crs for predicting 90-day mortality and univariate Cox proportional hazard model analysis was performed to estimate risk of Crs. Data were available for a total of 85 patients, including 50 (58.8%) patients in the higher Crs group and 35 (41.2%) patients in the lower Crs group. A lower Crs was significantly associated with a longer postoperative ECMO duration (hours, 42 vs. 24; P = 0.022), longer postoperative ventilator time (days, 3.7 vs. 2.0; P = 0.003), higher application of continuous renal replacement therapy (CRRT) (20.0% vs. 6.0%; P = 0.049), higher incidence of pneumonia (42.9% vs. 20.0%; P = 0.023), and higher 90-day mortality (22.9% vs. 6.0%; P = 0.023). The area under the curve of Crs for predicting 90-day mortality was 0.661 (P = 0.034). A higher Crs was a protective factor (hazard ratio = 0.925 [0.870-0.984)] P = 0.014). For lung transplant patients receiving VV-ECMO support, Crs < 25 ml/cmH2O is associated with more complications and higher 90-day mortality. As Crs is easily obtained at the bedside, it may be useful for predicting prognosis and guiding patient management.

Cell-free DNA in ex-vivo lung perfusate is associated with low-quality lungs and lung transplant outcome

BACKGROUND

Cell-free DNA (cfDNA) in ex-vivo lung perfusion (EVLP) perfusate has been shown to potentially reflect lung injury; however, the relationship between cfDNA concentration with clinical EVLP lung outcomes has not been elucidated.

METHODS

A discovery cohort of n = 100 clinical EVLP cases and a validation cohort (n = 50) were used in this single-center, retrospective cohort study. cfDNA was extracted and quantified from perfusate samples. The concentration of cfDNA at 1 hour and the change in cfDNA concentration per hour of EVLP in the transplanted and declined groups were compared by univariable and multivariable logistic regression. cfDNA was introduced as an additional factor in a machine-learning algorithm to predict lung utilization and postoperative outcome and the performance evaluated.

RESULTS

Significantly higher cfDNA concentrations were observed in the declined group than in the transplanted group (1 hour: p < 0.001; delta/hour: p = 0.031). Multivariable analysis among the 1 hour factors showed that [cfDNA 1 hour] (OR 4.27, p = 0.010) was an independent prognostic factor. Increases in [cfDNA 1 hour], [cfDNA delta/hour], and both showed that both initial [cfDNA] and increases in [cfDNA] over time were independently correlated with the probability of a lung being declined. The validation analysis also confirmed higher [cfDNA 1 hour] in the declined group than in the transplanted group (p = 0.010). Addition of [cfDNA] features improved the performance of a machine-learning algorithm used to predict donor lung utilization.

CONCLUSIONS

The cfDNA concentration in EVLP perfusate correlates with the rate of decline of lungs for transplant from EVLP.

Adoption of a semi-elective lung transplantation practice by safely extending cold ischemic times

OBJECTIVE

Lung transplantation is a complex surgical procedure performed by specialized teams. Practice changes to eliminate overnight lung transplants were implemented at our center and patient outcomes were evaluated.

METHODS

Patient and donor organ selection were performed in the standard fashion. All donors with a crossclamp after 6 pm matched to any of our listed recipients-independent of their surgical complexity or risk-were kept in a temperature-controlled iceless cooler from procurement to recipient implant. All recipients had a 7 am in-room start. Data were prospectively collected and compared with a cohort of recipients from the previous fifteen months.

RESULTS

In total, 82 transplants were performed at a single academic institution between July 1, 2022, and January 7, 2024, 22% of which included allografts with extended ischemic times using the iceless cooler (n = 18) with a median average temperature of 6.81 °C. Median ischemic times were 13.9 (12.5-15.6) hours, more than twice the length of ischemic times in the standard group (n = 64, 6.8 [6.1-7.4] hours). Postoperative outcomes were similar between groups, including postoperative intensive care unit duration (12 vs 9 days in the standard group), length of stay (24 vs 20 days), primary graft dysfunction grade (17% vs 20%), postoperative extracorporeal membrane oxygenation (22% vs 20%), and 6-month survival (94% vs 91%).

CONCLUSIONS

Donor lungs preserved in an iceless cooler were successfully transplanted after extended cold ischemic times. Adoption of a semielective transplant strategy can be successfully implemented without compromising patient outcomes. Additional advantages may be gleaned through daytime transplantation with standard transplant surgical teams rather than overnight, on-call, teams.

The effect of rewarming ischemia on tissue transcriptome and metabolome signatures: A clinical observational study in lung transplantation

BACKGROUND

In lung transplantation (LuTx), various ischemic phases exist, yet the rewarming ischemia time (RIT) during implantation has often been overlooked. During RIT, lungs are deflated and exposed to the body temperature in the recipient's chest cavity. Our prior clinical findings demonstrated that prolonged RIT increases the risk of primary graft dysfunction. However, the molecular mechanisms of rewarming ischemic injury in this context remain unexplored. We aimed to characterize the rewarming ischemia phase during LuTx by measuring organ temperature and comparing transcriptome and metabolome profiles in tissue obtained at the end versus the start of implantation.

METHODS

In a clinical observational study, 34 double-LuTx with ice preservation were analyzed. Lung core and surface temperature (n = 65 and 55 lungs) were measured during implantation. Biopsies (n = 59 lungs) were wedged from right middle lobe and left lingula at start and end of implantation. Tissue transcriptomic and metabolomic profiling were performed.

RESULTS

Temperature increased rapidly during implantation, reaching core/surface temperatures of 21.5°C/25.4°C within 30 minutes. Transcriptomics showed increased proinflammatory signaling and oxidative stress at the end of implantation. Upregulation of NLRP3 and NFKB1 correlated with RIT. Metabolomics indicated elevated levels of amino acids, hypoxanthine, uric acid, and cysteineglutathione disulfide alongside decreased levels of glucose and carnitines. Arginine, tyrosine, and 1-carboxyethylleucine showed a correlation with incremental RIT.

CONCLUSIONS

The final rewarming ischemia phase in LuTx involves rapid organ rewarming, accompanied by transcriptomic and metabolomic changes indicating proinflammatory signaling and disturbed cell metabolism. Limiting implantation time and cooling of the lung represent potential interventions to alleviate rewarming ischemic injury.

Lung allograft dysbiosis associates with immune response and primary graft dysfunction

BACKGROUND

Lower airway enrichment with oral commensals has been previously associated with severe primary graft dysfunction (PGD) after lung transplantation (LT). We aimed to determine whether this dysbiotic signature is present across all PGD severity grades and whether it is associated with a distinct host inflammatory endotype.

METHODS

Lower airway samples from 96 LT recipients were used to evaluate the lung allograft microbiota via 16S rRNA gene sequencing. Bronchoalveolar lavage (BAL) cytokine concentrations and cell differential percentages were compared across PGD grades. In a subset of samples, we evaluated the lower airway host transcriptome using RNA sequencing methods.

RESULTS

Differential analyses demonstrated lower airway enrichment with supraglottic-predominant taxa (SPT) in moderate and severe PGD. Dirichlet multinomial mixtures modeling identified 2 distinct microbial clusters. A greater percentage of subjects with moderate-severe PGD than no PGD were identified within the dysbiotic cluster (C-SPT, 48% and 29%, respectively) though this did not reach statistical significance (p = 0.06). PGD severity associated with increased BAL neutrophil concentration (p = 0.03) and correlated with BAL concentrations of MCP-1/CCL2, IP-10/CXCL10, IL-10, and TNF-α (p < 0.05). Furthermore, signatures of dysbiosis correlated with neutrophils, MCP-1/CCL-2, IL-10, and TNF-α (p < 0.05). C-SPT exhibited differential expression of TNF, SERPINE1, MPO, and MMP1 genes and upregulation of MAPK pathways, host signling associated with neutrophilic inflammation.

CONCLUSIONS

Lower airway dysbiosis within the lung allograft is associated with a neutrophilic inflammatory endotype, an immune profile commonly recognized as the hallmark for PGD. These data highlight a putative role of lower airway microbial dysbiosis in the pathogenesis of this syndrome.

Xenotransplantation of mitochondria: A novel strategy to alleviate ischemia-reperfusion injury during ex vivo lung perfusion

BACKGROUND

Ischemia-reperfusion injury (IRI) plays a crucial role in the development of primary graft dysfunction (PGD) following lung transplantation. A promising novel approach to optimize donor organs before transplantation and reduce the incidence of PGD is mitochondrial transplantation.

METHODS

In this study, we explored the delivery of isolated mitochondria in 4 hours ex vivo lung perfusion (EVLP) before transplantation as a means to mitigate IRI. To provide a fresh and viable source of mitochondria, as well as to streamline the workflow without the need for donor muscle biopsies, we investigated the impact of autologous, allogeneic, and xenogeneic mitochondrial transplantation. In the xenogeneic settings, isolated mitochondria from mouse liver were utilized while autologous and allogeneic sources came from pig skeletal muscle biopsies.

RESULTS

Treatment with mitochondrial transplantation increased the P/F ratio and reduced pulmonary peak pressure of the lungs during EVLP, compared to lungs without any mitochondrial transplantation, indicating IRI mitigation. Extensive investigations using advanced light and scanning electron microscopy did not reveal evidence of acute rejection in any of the groups, indicating safe xenotransplantation of mitochondria.

CONCLUSIONS

Future work is needed to further explore this novel therapy for combating IRI in lung transplantation, where xenotransplantation of mitochondria may serve as a fresh, viable source to reduce IRI.

Differentially expressed microRNAs in pre-transplant lung biopsies target immune checkpoint proteins and can predict primary graft dysfunction in lung transplantation

Lung transplantation (LTx) significantly improves outcomes for patients with end-stage respiratory failure. However, primary graft dysfunction (PGD) remains one of the most relevant hurdles. Although PGD is attributed to ischemia-reperfusion injury (IRI), immune responses, primarily T cell-mediated, may play a pivotal role in its pathogenesis. Additionally, innate immune activation following IRI links PGD to adaptive alloimmunity, highlighting the impact of early events on LTx outcomes. Immune checkpoints (ICPs) such as PD-1/PD-L1, CD40/CD40LG, and OX40/OX40L, regulate post-LTx T cell responses, and dysregulation of microRNAs (miRNAs) has been implicated in altering ICP expression, influencing the amplification of immune responses. In this preliminary study, we used the taqMan low-density array (TLDA) cards to investigate miRNA dysregulation's prognostic potential as a PGD marker in pre-transplant back-table lung biopsies. Our analysis revealed differential miRNA expression in donor lung tissues, potentially associated with PGD onset, targeting immune regulatory pathways. Specifically, deregulated miRNAs targeted key ICP proteins, including PD-L1, CD40LG, and OX40L. Moreover, the differential expression of these miRNAs was observed in grafts with future PGD compared to grafts without PGD, suggesting a potential prognostic benefit and a possible role for lung tissue miRNAs in the onset of early graft dysfunction. These findings provide a basis for future investigations into their mechanistic roles and therapeutic potential for PGD. Although based on a limited number of cases, our results imply that miRNAs might be involved in early graft dysfunction. While requiring validation in larger cohorts, our data raise the possibility that the evaluation of the aforementioned markers during the pre-transplant phase, might offer a prognostic benefit in monitoring the onset of PGD. Additionally, the use of compounds that can modulate the function of these molecules could be evaluated for the management of LTx patients.

The comparative impact of central vs. peripheral VA-ECMO cannulation on postoperative graft dysfunction in lung transplantation: a retrospective analysis

Background

Lung transplantation (LTx) is the definitive treatment for end-stage pulmonary diseases, with venoarterial extracorporeal membrane oxygenation (VA-ECMO) used as a common perioperative support. However, it remains unclear if central (cVA-ECMO) or peripheral (pVA-ECMO) cannulation routes yield better outcomes in postoperative prognosis. This study compares the impact of these two cannulation strategies on primary graft dysfunction (PGD) incidence in LTx patients.

Methods

A retrospective analysis was performed on 153 LTx patients supported with VA-ECMO at the Wuxi Lung Transplant Center (January 2019-March 2023). Patients were divided into central (n = 31) and peripheral (n = 91) groups. Data included recipient/donor demographics, preoperative status, and follow-up outcomes. The primary outcome was PGD within 72 h after reperfusion, whereas secondary outcomes included in-hospital mortality, 1-year survival, renal support needs, ventilation duration, intensive care unit (ICU) stay, and biochemical markers.

Results

PGD incidence was significantly higher in the peripheral group, with longer ECMO duration, ventilation, and ICU stay. Central VA-ECMO showed advantages in in-hospital mortality and 1-year survival rates.

Conclusion

Central VA-ECMO cannulation may reduce postoperative complications and improve survival for LTx recipients. Prospective studies are needed to confirm these findings and refine perioperative ECMO management.

Developing approaches to incorporate donor-lung computed tomography images into machine learning models to predict severe primary graft dysfunction after lung transplantation

Primary graft dysfunction (PGD) is a common complication after lung transplantation associated with poor outcomes. Although risk factors have been identified, the complex interactions between clinical variables affecting PGD risk are not well understood, which can complicate decisions about donor-lung acceptance. Previously, we developed a machine learning model to predict grade 3 PGD using donor and recipient electronic health record data, but it lacked granular information from donor-lung computed tomography (CT) scans, which are routinely assessed during offer review. In this study, we used a gated approach to determine optimal methods for analyzing donor-lung CT scans among patients receiving first-time, bilateral lung transplants at a single center over 10 years. We assessed 4 computer vision approaches and fused the best with electronic health record data at 3 points in the machine learning process. A total of 160 patients had donor-lung CT scans for analysis. The best imaging-only approach employed a 3D ResNet model, yielding median (interquartile range) areas under the receiver operating characteristic and precision-recall curves of 0.63 (0.49-0.72) and 0.48 (0.35-0.6), respectively. Combining imaging with clinical data using late fusion provided the highest performance, with median areas under the receiver operating characteristic and precision-recall curves of 0.74 (0.59-0.85) and 0.61 (0.47-0.72), respectively.

Early Prone Positioning As a Rescue Therapy for Moderate-to-severe Primary Graft Dysfunction After Bilateral Lung Transplant

OBJECTIVES

Primary graft dysfunction (PGD) affects survival after lung transplant (LT). The current hypothesis was that prone positioning (PP), proposed as a rescue maneuver to treat refractory hypoxemia due to PGD, may improve LT outcomes, especially when applied early.

DESIGN

Bilateral LT recipients developing moderate-to-severe PGD within 24 hours from intensive care unit admission were enrolled. From January 2020 to November 2021, patients developing PGD after LT were turned prone between 24 and 48 hours after diagnosis, only in case of radiological or oxygenation worsening ("late PP" group). After November 2021, patients were routinely turned prone within 24 hours from PGD diagnosis ("early PP"). A propensity score-weighted analysis, adjusted for clinically relevant covariates, was applied.

SETTING

Intensive care unit.

PARTICIPANTS

Bilateral LT recipients.

INTERVENTIONS

Early PP, late PP, or supine position.

MEASUREMENTS AND MAIN RESULTS

130 LT patients were screened and 67 were enrolled. A total of 25 (37%) recipients were treated in the supine position, 24 (36%) in early PP, and 18 (27%) in late PP. After propensity score weighting, both supine treatment (estimated effect for 1 ventilator-free day = 8.23, standard error: 2.97, p = 0.007) and early PP treatment (estimated effect = 9.42, standard error: 2.59, p < 0.001) were associated with greater 28-day ventilator-free days than late PP treatment (reference). Compared with late PP, early PP was also associated with better oxygenation, driving pressure, and static respiratory system compliance. Compared with supine recipients, the early PP group showed better oxygenation at 72 hours after PGD diagnosis.

CONCLUSIONS

Early PP in LT recipients with moderate-to-severe PGD seems to be associated with better 28-day ventilator-free days, oxygenation, and driving pressure than late PP.

Disturbed sleep after lung transplantation is associated with worse patient-reported outcomes and chronic lung allograft dysfunction

Background

Many lung transplant recipients fail to derive the expected improvements in health-related quality of life (HRQL) and survival. Sleep may represent an important, albeit rarely examined, factor associated with lung transplant outcomes.

Methods

Within a larger cohort study, 141 lung transplant recipients completed the Medical Outcomes Study Sleep Problems Index (SPI) Revised scale along with a broader survey of patient-reported outcome (PRO) measures and frailty assessment. From the SPI, we also derived an insomnia-specific subscale. Potential perioperative risk factors for disturbed sleep were derived from medical records. We investigated associations between perioperative predictors on SPI and insomnia and associations between SPI and insomnia on PROs and frailty by linear regressions, adjusting for age, sex, and lung function. We evaluated the associations between SPI and insomnia on time to chronic lung allograft dysfunction (CLAD) and death using Cox models, adjusting for age, sex, and transplant indication.

Results

Post-transplant hospital length of stay >30 days was associated with worse sleep by SPI and insomnia (SPI: p = 0.01; insomnia p = 0.02). Worse sleep by SPI and insomnia was associated with worse depression, cognitive function, HRQL, physical disability, health utilities, and Fried Frailty Phenotype frailty (all p < 0.01). Those in the worst quartile of SPI and insomnia exhibited an increased risk of CLAD (hazard ratio [HR] 2.18; 95% confidence interval [CI]: 1.22-3.89; p = 0.01 for SPI and HR 1.96; 95%CI 1.09-3.53; p = 0.03 for insomnia). Worsening in SPI but not insomnia was also associated with mortality (HR: 1.29; 95%CI: 1.05-1.58; p = 0.01).

Conclusions

Poor sleep after lung transplant appears associated with PROs, frailty, CLAD, and death. Clarifying the nature of this association may have important screening implications.

L-Alanyl-L-Glutamine Alleviated Ischemia-Reperfusion Injury and Primary Graft Dysfunction in Rat Lung Transplants

BACKGROUND

Concern of ischemia-reperfusion injury reduces utilization of donor lungs. We hypothesized adding L-alanyl-L-glutamine (L-AG) to preservation solution may protect donor lungs from ischemia-reperfusion injury through its multiple cytoprotective effects.

METHODS

A lung transplantation cell culture model was used on human lung epithelial cells and pulmonary microvascular endothelial cells, and the effects of adding different concentrations of L-AG on basic cellular function were tested. Rat donor lungs were preserved at 4 °C with 8 mmol/L L-AG for 12 h followed by 4 h reperfusion or monitored for 3 d. Lung function, lung histology, inflammation, and cell death biomarker were tested. Computerized tomography scan was used and metabolomic analysis was performed on lung tissues.

RESULTS

Cold preservation with L-AG improved cell viability and inhibited apoptosis in cell culture. Rat donor lungs treated with L-AG during cold storage showed decreased peak airway pressure, higher dynamic compliance and oxygenation ability, reduced lung injury, apoptosis, and oxidative stress during reperfusion. L-AG treatment significantly changed 130 metabolites during reperfusion, with enhanced amino acid biosynthesis and tricarboxylic acid cycle. Furthermore, cold storage with L-AG decreased primary graft dysfunction grade, improved oxygenation, reduced pulmonary atelectasis, sign of infection, and pneumothorax in a rat left lung transplant 3-d survival model.

CONCLUSIONS

Adding L-AG to cold preservation solution reduced lung injury and alleviated primary graft dysfunction by inhibiting inflammation, oxidative stress, and cell death with modified metabolic activities.

Loss of Nr4a1 ameliorates endothelial cell injury and vascular leakage in lung transplantation from circulatory-death donor

BACKGROUND

Ischemia-reperfusion injury (IRI) stands as a major trigger for primary graft dysfunction (PGD) in lung transplantation (LTx). Especially in LTx from donation after cardiac death (DCD), effective control of IRI following warm ischemia (WIRI) is crucial to prevent PGD. This study aimed to identify the key factors affecting WIRI in LTx from DCD.

METHODS

Previously reported RNA-sequencing dataset of lung WIRI was reanalyzed to identify nuclear receptor subfamily 4 group A member 1 (NR4A1) as the immediate early gene for WIRI. Dynamics of NR4A1 expression were verified using a mouse hilar clamp model. To investigate the role of NR4A1 in WIRI, a mouse model of LTx from DCD was established using Nr4a1 knockout (Nr4a1-/-) mice.

RESULTS

NR4A1 was located around vascular cells, and its protein levels in the lungs increased rapidly and transiently during WIRI. LTｘ from Nr4a1-/- donors significantly improved pulmonary graft function compared to wild-type donors. Histological analysis showed decreased microvascular endothelial cell death, neutrophil infiltration, and albumin leakage. Evans blue permeability assay demonstrated maintained pulmonary microvascular barrier integrity in grafts from Nr4a1-/- donors, correlating with diminished pulmonary edema. However, NR4A1 did not significantly affect the inflammatory response during WIRI, and IRI was not suppressed when a wild-type donor lung was transplanted into the Nr4a1-/- recipient.

CONCLUSIONS

Donor NR4A1 plays a specialized role in the positive regulation of endothelial cell injury and microvascular hyperpermeability. These findings demonstrate the potential of targeting NR4A1 interventions to alleviate PGD and improve outcomes in LTx from DCD.

Association of Inflammatory Profile During Ex Vivo Lung Perfusion With High-Grade Primary Graft Dysfunction: A Systematic Review and Meta-Analysis

PGD3 is the manifestation of ischemia-reperfusion injury which results from inflammation and cell death and is associated with poor outcome. This systematic-review and meta-analysis of non-randomized controlled trials on patients undergoing Ltx with reconditioned lungs via EVLP, aims to assess the association between the levels of proinflammatory biomarkers during EVLP and PGD3 development within the firsts 72 h post-Ltx. Biomarkers were categorized by timing (1-hour, T0 and 4-hours, Tend from EVLPstart) and by their biological function (adhesion molecules, chemokines, cytokines, damage-associated-molecular-patterns, growth-factors, metabolites). We employed a four-level mixed-effects model with categorical predictors for biomarker groups to identify differences between patients with PGD3 and others. The single study and individual measurements were considered random intercepts. We included 8 studies (610 measurements at T0 and 884 at Tend). The pooled effect was 0.74 (p = 0.021) at T0, and 0.90 (p = 0.0015) at Tend. The four-level model indicated a large pooled correlation between developing PGD3 at 72 h post-Ltx and inflammatory biomarkers values, r = 0.62 (p = 0.009). Chemokine group showed the strongest association with the outcome (z-value = 1.26, p = 0.042). Pooled panels of inflammation markers, particularly chemokines, measured at T0 or at Tend, are associated with the development of PGD3 within the first 72 h after Ltx.

Systematic Review Registration

https://osf.io/gkxzh/.

Machine Learning for Predicting Primary Graft Dysfunction After Lung Transplantation: An Interpretable Model Study

BACKGROUND

Primary graft dysfunction (PGD) develops within 72 h after lung transplantation (Lung Tx) and greatly influences patients' prognosis. This study aimed to establish an accurate machine learning (ML) model for predicting grade 3 PGD (PGD3) after Lung Tx.

METHODS

This retrospective study incorporated 802 patients receiving Lung Tx between July 2018 and October 2023 (640 in the derivation cohort and 162 in the external validation cohort), and 640 patients were randomly assigned to training and internal validation cohorts in a 7:3 ratio. Independent risk factors for PGD3 were determined by integrating the univariate logistic regression and least absolute shrinkage and selection operator regression analyses. Subsequently, 9 ML models were used to construct prediction models for PGD3 based on selected variables. Their prediction performances were further evaluated. Besides, model stratification performance was assessed with 3 posttransplant metrics. Finally, the SHapley Additive exPlanations algorithm was used to understand the predictive importance of selected variables.

RESULTS

We identified 9 independent clinical risk factors as selected variables. Among 9 ML models, the random forest (RF) model displayed optimal performance (area under the curve [AUC] = 0.9415, sensitivity [Se] = 0.8972, specificity [Sp] = 0.8795 in the training cohort; AUC = 0.7975, Se = 0.7520, Sp = 0.7313 in the internal validation cohort; and AUC = 0.8214, Se = 0.8235, Sp = 0.6667 in the external validation cohort). Further assessments on calibration and clinical usefulness indicated the promising applicability of the RF model in PGD3 prediction. Meanwhile, the RF model also performed best in terms of risk stratification for postoperative support (extracorporeal membrane oxygenation time: P < 0.001, mechanical ventilation time: P = 0.006, intensive care unit time: P < 0.001).

CONCLUSIONS

The RF model had the optimal performance in PGD3 prediction and postoperative risk stratification for patients after Lung Tx.

Unveiling the potential of lung transplantation for situs inversus

INTRODUCTION

Situs inversus is a rare congenital condition where the organs in the chest and abdomen are reversed, thus complicating surgeries such as lung transplantation. Kartagener syndrome (KS), associated with situs inversus, includes chronic sinusitis and bronchiectasis, which can progress to end-stage lung disease requiring transplantation. This review discusses the unique surgical considerations, technical challenges, and outcomes of lung transplantation in patients with situs inversus, particularly KS.

AREAS COVERED

The review highlights anatomical and physiological challenges in lung transplantation due to reversed organ positioning, requiring customized surgical approaches and intraoperative modifications. Preoperative imaging, anesthesia adjustments, and tailored surgical techniques are crucial for successful transplantation. Postoperative care focuses on managing complications such as primary graft dysfunction, infections, and anastomotic issues. Literature on survival rates, chronic lung allograft dysfunction, and quality of life is analyzed, indicating outcomes comparable to other lung transplant recipients.

EXPERT OPINION

Despite significant challenges, lung transplantation in patients with situs inversus and KS is feasible with outcomes similar to traditional cases. Advances in imaging, surgical planning, and minimally invasive techniques offer promise for improved outcomes. Ongoing research, collaboration, and ethical considerations are essential to optimizing care and expand treatment possibilities for this high-risk patient population.

Cannulation Configuration and Its Effects on Bridging to Lung Transplant: Analysis of the Extracorporeal Life Support Organization Registry

BACKGROUND

Donor stagnation and modification of lung allocation scores has resulted in a higher acuity of patient presentation before lung transplantation. Extracorporeal membrane oxygenation (ECMO) has been used as a bridge to lung transplant (BTT), although the effect of cannulation strategy on outcomes has not been well investigated. We analyzed contemporary data on ECMO BTT by using a large, international registry of patients.

METHODS

We used the Extracorporeal Life Support Organization registry to identify all adult patients from 2010 to 2022 undergoing ECMO as a BTT. Patients were stratified by venovenous or venoarterial support type.

RESULTS

A total of 1066 patients were identified. ECMO BTT increased over the study period (P < .001), as did survival to hospital discharge (P < .001), with an overall survival of 87.7%. Venovenous patients experienced fewer complications on ECMO, including dialysis (16.7% vs 25.3%, P = .006), stroke (1.4% vs 5.1%, P = .004), and limb ischemia (0.2% vs 3.4%, P < .001) and required ECMO less frequently in the postoperative period (41.0% vs 53.4%, P = .002) and for less time (4 days [interquartile range, 2-7 days] vs 5 days [interquartile range, 3-9 days], P = .01). In-hospital mortality was significantly lower for venovenous patients compared with venoarterial patients (11.0% vs 18.5%, P = .005). Increasing center volume of ECMO BTT was protective of in-hospital mortality (P < .001), with benefit observed after ∼45 total BTT intent cannulations.

CONCLUSIONS

ECMO BTT has resulted in improved posttransplant survival to discharge. Owing to a higher rate of complications and worsened mortality, thoughtful implementation of venoarterial ECMO in BTT should be undertaken when assessing patient candidacy.

Restoring discarded porcine lungs by ex vivo removal of neutrophil extracellular traps

BACKGROUND

By causing inflammation and tissue damage, neutrophil extracellular traps (NETs) constitute an underlying mechanism of aspiration-induced lung injury, a major factor of the low utilization of donor lungs in lung transplantation (LTx).

METHODS

To determine whether NET removal during ex vivo lung perfusion (EVLP) can restore lung function and morphology in aspiration-damaged lungs, gastric aspiration lung injury was induced in 12 pigs. After confirmation of acute respiratory distress syndrome, the lungs were explanted and assigned to NET removal connected to EVLP (treated) (n = 6) or EVLP only (nontreated) (n = 6). Hemodynamic measurements were taken, and blood and tissue samples were collected to assess lung function, morphology, levels of cell-free DNA, extracellular histones, and nucleosomes as markers of NETs, as well as cytokine levels.

RESULTS

After EVLP and NET removal in porcine lungs, PaO2/FiO2 ratios increased significantly compared to those undergoing EVLP alone (p = 0.0411). Treated lungs had lower cell-free DNA (p = 0.0260) and lower levels of extracellular histones in EVLP perfusate (p= 0.0260) than nontreated lungs. According to histopathology, treated lungs showed less immune cell infiltration and less edema compared with nontreated lungs, which was reflected in decreased levels of proinflammatory cytokines in EVLP perfusate and bronchoalveolar lavage fluid.

CONCLUSIONS

To conclude, removing NETs during EVLP improved lung function and morphology in aspiration-damaged donor lungs. The ability to remove NETs during EVLP could represent a new therapeutic approach for LTx and potentially expand the donor pool for transplantation.

Lung transplantation in pulmonary sarcoidosis

Sarcoidosis is a systemic inflammatory disease of unknown etiology and variable clinical course. Pulmonary sarcoidosis is the most common presentation and accounts for most morbidity and mortality related to sarcoidosis. While sarcoidosis generally has good outcomes, few patients experience chronic disease. A minority of patients progress to a specific phenotype of sarcoidosis referred to advanced pulmonary sarcoidosis (APS) which includes advanced fibrosis, pulmonary hypertension and respiratory failure, leading to high morbidity and mortality. In patients with advanced disease despite medical therapy, lung transplantation may be the last viable option for improvement in quality of life. Though post-transplant survival is similar to that of other end-stage lung diseases, it is imperative that patients are evaluated and referred early to transplant centers with experience in APS. A multidisciplinary approach and clinical experience are crucial in detecting the optimal timing of referral, initiating comprehensive transplantation evaluation and listing, discussing surgical approach, and managing perioperative and post-transplant care. This review article seeks to address these aspects of lung transplantation in APS.

Update on the immunological mechanisms of primary graft dysfunction and chronic lung allograft dysfunction

PURPOSE OF REVIEW

Primary graft dysfunction (PGD) and chronic lung allograft dysfunction (CLAD) are the leading causes of graft loss in lung transplant recipients. The development of mouse lung transplant models has allowed for the genetic dissection of cellular and molecular pathways that prevent graft survival. This review provides an overview into recent mechanistic insights into PGD and CLAD.

RECENT FINDINGS

Mouse orthotopic lung transplant models and investigations of human lung transplant recipeints have revealed new molecular and cellular targets that promote PGD and CLAD. Donor and recipient-derived innate immune cells promote PGD and CLAD. PGD is driven by communication between classical monocytes and tissue-resident nonclassical monocytes activating alveolar macrophages to release chemokines that recruit neutrophils. Products of cell damage trigger neutrophil NET release, which together with NK cells, antibodies and complement, that further promote PGD. The development of CLAD involves circuits that activate B cells, CD8 + T cells, classical monocytes, and eosinophils.

SUMMARY

Effective targeted management of PGD and CLAD in lung transplant recipient to improve their long-term outcome remains a critical unmet need. Current mechanistic studies and therapeutic studies in mouse models and humans identify new possibilities for prevention and treatment.

Real-time lung weight measurement during clinical ex vivo lung perfusion

BACKGROUND

Real-time lung weight (LW) measurement is a simple and noninvasive technique for detecting extravascular lung water during ex vivo lung perfusion (EVLP). We investigated the feasibility of real-time LW measurement in clinical EVLP as a predictor of transplant suitability and post-transplant outcomes.

METHODS

In our clinical acellular EVLP protocol, real-time LW was measured in 117 EVLP cases from June 2019 to June 2022. The estimated LW gain at each time point was calculated using a scale placed under the organ chamber. The lungs were classified into 4 categories based on LW adjusted for height and compared between suitable and unsuitable cases. The relationship between estimated LW gain and primary graft dysfunction was also investigated.

RESULTS

The estimated LW gain during the EVLP significantly correlated with the LW gain (post-EVLP LW and pre-EVLP LW) measured on the back table (R2 = 0.61, p < 0.01). In the adjusted LW categories 2 to 4, the estimated LW gain at 0-1 hour after EVLP was significantly higher in unsuitable cases than in suitable cases. The area under the curve for the estimated LW gain was ≥0.80. Primary graft dysfunction grades 0 to 1 had a significantly lower estimated LW gain at 60 minutes than grades 2 to 3 (-43 vs 1 g, p < 0.01).

CONCLUSIONS

Real-time lung measurements can predict transplant suitability and post-transplant outcomes by the early detection of extravascular lung water during the initial 1 hour of EVLP.

Amniotic fluid-derived mesenchymal stem cells reduce inflammation and improve lung function following transplantation in a porcine model

BACKGROUND

Lung transplantation is hindered by low donor lung utilization rates. Infectious complications are reasons to decline donor grafts due to fear of post-transplant primary graft dysfunction. Mesenchymal stem cells are a promising therapy currently investigated in treating lung injury. Full-term amniotic fluid-derived lung-specific mesenchymal stem cell treatment may regenerate damaged lungs. These cells have previously demonstrated inflammatory mediation in other respiratory diseases, and we hypothesized that treatment would improve donor lung quality and postoperative outcomes.

METHODS

In a transplantation model, donor pigs were stratified to either the treated or the nontreated group. Acute respiratory distress syndrome was induced in donor pigs and harvested lungs were placed on ex vivo lung perfusion (EVLP) before transplantation. Treatment consisted of 3 doses of 2 × 106 cells/kg: one during EVLP and 2 after transplantation. Donors and recipients were assessed on clinically relevant parameters and recipients were followed for 3 days before evaluation for primary graft dysfunction (PGD).

RESULTS

Repeated injection of the cell treatment showed reductions in inflammation seen through lowered immune cell counts, reduced histology signs of inflammation, and decreased cytokines in the plasma and bronchoalveolar lavage fluid. Treated recipients showed improved pulmonary function, including increased PaO2/FiO2 ratios and reduced incidence of PGD.

CONCLUSIONS

Repeated injection of lung-specific cell treatment during EVLP and post transplant was associated with improved function of previously damaged lungs. Cell treatment may be considered as a potential therapy to increase the number of lungs available for transplantation and the improvement of postoperative outcomes.

Extracorporeal membrane oxygenation as a bridge to transplant in severe pulmonary hypertension

OBJECTIVES

Severe pulmonary hypertension (PH) is the leading indication for a lung transplant in younger patients. Despite the availability of validated risk scores, their influence on lung allocation has been negligible, with continued reliance on decompensation and bridging with extracorporeal membrane oxygenation (ECMO).This single-centre, retrospective study assessed outcome of ECMO bridging in lung transplant for PH and evaluated short-term predictability of ECMO bridging.

METHODS

Patients with PH listed for a lung transplant between January 2010 and March 2023 were included. Peri- and postoperative courses were compared dependent upon ECMO bridging status. Bridging risk analysis within 90 days of re-evaluation included patients not requiring ECMO at listing, with listing parameters evaluated using a univariate Cox proportional hazard regression.

RESULTS

A total of 114/123 patients listed underwent lung transplant. Twenty-eight required ECMO bridging. No differences in primary graft dysfunction grade 3 at 72 h (30 vs 20%; P = 0.28) or graft survival (1 year: 82 vs 88%; 5 years: 54 vs 59%; P = 0.84) were evident. ECMO bridging resulted in longer intensive care unit stays post-transplant (P = 0.002) and higher rates of both re-thoracotomy (P = 0.049) and vascular complications (P = 0.031). Factors increasing 90-day ECMO risk included N-terminal pro-B-type natriuretic peptide (P < 0.001), 6-min walk distance (P = 0.03) and O2 requirement at rest (P = 0.006).

CONCLUSIONS

Lung transplant survival outcomes are not affected by ECMO bridging in patients with severe PH. It does, however, expose patients to additional risk, and efforts such as easy-to-measure parameters to pre-emptively identify patients requiring bridging to assist with effective allocation should be encouraged.

Dynamic associations between adverse events after lung transplantation and allograft ischaemic time

OBJECTIVES

The effect of allograft ischaemic time (AIT) on postoperative events after lung transplantation remains unclear. This study aims to assess the feasibility of extending the duration of AIT.

METHODS

The United Network for Organ Sharing database was queried for adult lung transplantation from 4 May 2005 to 30 June 2020. Patients were divided as per AIT into standard ischaemic time (<6 h) and prolonged ischaemic time (≥6 h) groups using propensity score matching and evaluated on a continuous scale using restricted cubic splines. The primary outcome was overall 1-year and 5-year survival.

RESULTS

Among 11 438 propensity-matched recipients, standard ischaemic time and prolonged ischaemic time showed no differences in overall 1-year (P = 0.29) or 5-year (P = 0.29) survival. Prolonged ischaemic time independently predicted early postoperative ventilator support for >48 h (OR = 1.33, 95% CI 1.22-1.44), dialysis (OR = 1.55, 95% CI 1.30-1.84), primary graft dysfunction (PGD; OR = 1.28, 95% CI 1.09-1.50), acute rejection (OR = 1.42, 95% CI 1.24-1.62), and interestingly, decreased 5-year bronchiolitis obliterans syndrome (HR = 0.91, 95% CI 0.85-0.97). In relative risk curves, 1-year mortality, prolonged ventilation, dialysis and PGD steadily increased per hour as AIT extended. The risk of acute rejection and 5-year bronchiolitis obliterans syndrome also showed significant changes between 5 and 8 h of AIT. In contrast, 5-year mortality remained constant despite rising AIT.

CONCLUSIONS

Prolonged AIT worsened early outcomes such as PGD, but improved bronchiolitis obliterans syndrome freedom at later time points. Despite this, both short- and long-term survival were similar between prolonged ischaemic time and standard ischaemic time patients. Dynamic risk changes in post-transplant events should be noted for prolonged ischaemia lung use.

Right Heart Recovery Post Lung Transplant With COVID-19-Related Acute Respiratory Distress Syndrome

Background: Right heart remodeling is noted in patients with severe COVID-19-associated acute respiratory distress syndrome (ARDS). There is limited information regarding right heart recovery following lung transplantation in this cohort. Methods: Retrospective review of institutional transplant database from June 2020 to June 2022 was performed at Northwestern University in Chicago, Illinois. Demographic, laboratory, histopathologic, lung transplant outcomes, and pre- and postoperative echocardiographic data were recorded and analyzed. Results: Of the 42 patients who underwent lung transplantation for COVID-19-related ARDS, 6 patients were excluded due to having either a single-lung transplant (n = 2), lobar transplant (n = 1), or dual-organ transplant (n = 1) or for missing postoperative TTE data (n = 2) and 36 were included in the study; there were no 90-day deaths, and the 1-year survival rate was 88.8%. Intraoperative hemodynamics data showed a mean pulmonary artery pressure of 49 ± 23 mm Hg. Preoperative echocardiography was evaluated at a median of 15.5 (10-34.3) (IQR) days preoperatively and 140 (108-201) days (IQR) postoperatively. RV size grade improved from an average of 1.7 ± 0.85 to 1.3 ± 0.6 (p < 0.05), while RV function improved from an average of 2.2 ± 1.2 to 1 ± 1 (p < 0.05). There was a reduction in RVSP from 46.5 ± 18 mmHg to 30.1 ± 7.8 mmHg (p < 0.05) and RV free wall strain showed improvement from -13.9 ± 6.1% to -18.5 ± 5.4% (p < 0.05). Conclusions: The results showed that the RV size and systolic function demonstrate improvement with normalization in a relatively short period following lung transplantation for patients with COVID-19-associated ARDS.

The impact of the EVLP on the lung microbiome and its inflammatory reaction

The pulmonary microbiome has emerged as a significant factor in respiratory health and diseases. Despite the sterile conditions maintained during ex vivo lung perfusion (EVLP), the use of antibiotics in the perfuse liquid can lead to dynamic changes in the lung microbiome. Here, we present the design of a study that aims to investigate the hypothesis that EVLP alters the lung microbiome and induces tissue inflammation. This pilot, prospective, controlled study will be conducted in two Spanish donor centers and will include seven organ donors after brain death or after controlled cardiac death. After standardized retrieval, the left lung will be preserved in cold storage and the right lung will be perfused with EVLP. Samples from bronchoalveolar lavage, perfusion and preservation solutions, and lung biopsies will be collected from both lungs and changes in lung microbiome and inflammatory response will be compared.

The Relationship Between Ex Vivo Lung Perfusion Strategies and Transplantation Outcomes: Insights From the United Network for Organ Sharing Data

BACKGROUND

Ex vivo lung perfusion (EVLP) can increase the donor pool by allowing high-risk lungs to be further evaluated for transplant. Several EVLP platforms are currently in use. This study examines whether different EVLP platforms have any association with post-transplant outcomes.

METHODS

The United Network for Organ Sharing registry was queried from February 28, 2018, to March 31, 2024, for adult double lung transplant recipients with EVLP data. EVLP platform was categorized as hospital EVLP, EVLP facility, mobile EVLP, or No EVLP. Recipients of EVLP lungs were statistically matched to recipients of No EVLP lungs on donor characteristics.

RESULTS

After matching, the final cohort included 1542 in the No EVLP group and 771 who received EVLP. Lungs placed on EVLP had significantly longer ischemic time than No EVLP (P < 0.001). Patients who received EVLP lungs had significantly longer post-transplant length of stay (≥25 d versus 21 d No EVLP, P < 0.001). Ischemic time (OR = 1.04, P = 0.008) and being in the ICU at the time of transplant (OR = 2.22, P < 0.001) were associated with higher rates of primary graft dysfunction (PGD3). After adjusting for hospital status and ischemic time, there was no association between the EVLP modality and PGD3. Subgroup analysis showed that DCD recipients did not have worse short- or long-term outcomes.

CONCLUSIONS

There is no relationship between EVLP modality, PGD3, and post-transplant survival after matching donor quality and adjusting for ischemic time. Work should continue to focus on reducing ischemic times so EVLP can continue to increase the donor pool while limiting adverse effects.

Impact of donor organ quality on recipient outcomes in lung transplantation: 14-Year single-center experience using the Eurotransplant lung donor score

Background

The use of extended-criteria donor (ECD) organs has increased in lung transplantation, but their impact on long-term outcomes remains unclear. This retrospective single-center study evaluates the impact of donor quality, as defined by the Eurotransplant (ET) lung donor score, on long-term graft function and survival.

Methods

Records of recipients transplanted between January 2010 and May 2023 were reviewed. Eurotransplant lung donor scores (ET scores) were retrospectively calculated from the corresponding donor reports. Outcomes were compared between recipients of donor lungs with an ET score of 6 (group 1), 7 and 8 (group 2), and 9 to 13 (group 3, ECD lungs). Median follow-up was 64 (30-104) months.

Results

In total, 280 (19%) patients were transplanted with ET score 6 lungs, 717 (48%) patients with ET scores 7 and 8 lungs, and 506 (34%) patients with ET scores 9 to 13 (ECD) lungs. The occurrence of primary graft dysfunction grade 3 at 72 hours (p = 0.672), duration of mechanical ventilation (p = 0.062), and in-hospital mortality (p = 0.713) did not differ between groups. Long-term graft survival (%) was lower in group 2 and 3 vs group 1 recipients (at 10 years: 51 and 48 vs 56, p = 0.052, respectively). Similarly, freedom from chronic lung allograft dysfunction (CLAD, %) was lower in group 2 and 3 vs group 1 recipients (at 10 years: 57 and 55 vs 63, p = 0.033, respectively). Donor smoking history was associated with worse CLAD-free survival (hazard ratio = 1.466, 95% confidence interval = 1.215-1.769, p < 0.001).

Conclusions

ECD lungs represented an important resource in lung transplantation. However, their use may be associated with a worse long-term graft and CLAD-free survival.

Hospital-free days in the first year after lung transplantation and subsequent survival

Background

Complications occurring during the first postoperative year after lung transplantation increase the risk of long-term mortality. These events often lead to prolonged and repeated hospitalizations. We sought to assess the relationship between days outside the hospital or hospital-free days (HFD) during the first post-transplant year among 1-year survivors and subsequent retransplant-free survival.

Methods

In a single-center study, we derived total inpatient days (initial transplant episode, readmission, and emergency room/observation) from the electronic medical record of lung transplant recipients who survived 1 year. The cohort was divided into HFD quartiles and Kaplan-Meier curves of subsequent transplant-free survival were compared with log-rank analysis. A Cox proportional hazards model was used to test the association of HFD with outcome and adjusted for selected variables.

Results

Among 238 patients, 42 deaths and 2 retransplants occurred after a median of 3.6 years post-transplant. The median HFD was 341 (interquartile range: 324, 348). Estimated transplant-free survival at 3 and 5 years post-transplant in the lowest quartile of HFD (79% and 56%, respectively) was considerably worse compared with the first quartile (98% and 94%; p < 0.01). Fewer HFD were associated with subsequent death or retransplant [hazard ratio: 0.90 (95% confidence interval: 0.85, 0.94; p < 0.001) for each 10-day increase] and remained significant after adjusting for several potentially confounding variables.

Conclusions

HFD during the first year after lung transplantation is a predictor of subsequent long-term outcomes and may be a useful surrogate marker for clinical trials during the early postoperative period.

A multicenter analysis of lung transplantation outcomes comparing donation after circulatory death and donation after brain death

Background

Donor organ shortage is a barrier to lung transplantation. Donation after circulatory death (DCD) may offer a solution, although it is underutilized. The objective of this study was to compare survival and other postoperative outcomes between DCD and donation after brain death (DBD).

Methods

We performed a multicenter analysis of Multi-Institutional Extracorporeal Life Support (ECLS) Registry data from 11 lung transplant centers in the United States and Europe. Demographics and clinical parameters were compared using chi-square test and Fisher's exact test. Survival was assessed by Kaplan-Meier curves and compared by log-rank test with propensity score matching.

Results

Of 1,585 patients included in the study, 135 (8.5%) received DCD lungs and 1,450 (91.5%) received DBD lungs. DCD recipients had higher rates of obstructive lung disease (p = 0.042), longer total ischemic time (p < 0.0001), and higher rates of primary graft dysfunction (PGD) at t0h (p < 0.0001) and t24h (p = 0.0005). PGD at t48h and t72h was not significantly different between DCD and DBD recipients. Ninety-day survival was lower among DCD recipients (91.2%) compared to DBD recipients (97.4%, p = 0.038). Survival was higher without ECLS (p = 0.014), whereas ex vivo lung perfusion (EVLP) (p = 0.47) did not affect survival.

Conclusions

Overall, our data showed excellent 90-day survival for DCD and DBD recipients, although DCD recipients had relatively lower survival. EVLP was not associated with survival, which may guide future strategies to optimize DCD utilization.