Functional and computed tomographic evolution and survival of restrictive allograft syndrome after lung transplantation

Early chest CT abnormalities to predict the subsequent occurrence of chronic lung allograft dysfunction

INTRODUCTION

Chronic lung allograft dysfunction (CLAD) can take two forms: bronchiolitis obliterans syndrome (BOS) or restrictive allograft syndrome (RAS). The aim was to determine if chest-CT abnormalities after lung transplantation (LTx) could predict CLAD before respiratory functional deterioration.

MATERIALS AND METHODS

This monocentric retrospective study analyzed consecutive patients who underwent LTx from January 2015 to December 2018. Initial CT post-LTx (CTi) and a follow-up CT at least 9 months post-LTx (CTf) were reviewed. CLAD was defined as a persistent respiratory functional decline (> 20% of basal FEV1) outside acute episode. A Cox regression was performed in univariate, then in multivariate analysis (including features with p < 0.01 in univariate or of clinical importance) to determine risk factors for CLAD. Subgroup analyses were made for BOS, RAS, and death.

RESULTS

Among 118 LTx patients (median (min-max) 47 (18-68) years), 25 developed CLAD during follow-up (19 BOS). The median time to CLAD since LTx was 570 days [150-1770]. Moderate pulmonary artery stenosis (30-50%) was associated with the occurrence of CLAD on CTi (hazard ratio HR = 4.6, CI [1.6-13.2]) and consolidations and pleural effusion on CTf (HR = 2.6, CI [1.3-4.9] and HR = 4.5, CI [1.5-13.6] respectively). The presence of mosaic attenuation (HR = 4.1, CI [1.4-12.5]), consolidations (HR = 2.6, CI [1.3-5.4]), and pleural effusions (p = 0.01, HR = 5.7, CI [1.4-22.3]) were risk factors for BOS on CTf. The consolidations (p = 0.029) and pleural effusions (p = 0.001) were risk factors for death on CTf.

CONCLUSIONS

CTi and CTf in the monitoring of LTx patients could predict CLAD. Moderate pulmonary artery stenosis, mosaic pattern, parenchyma condensations, and pleural effusions were risk factors for CLAD.

CRITICAL RELEVANCE STATEMENT

There is a potential predictive role of chest CT in the follow-up of LTx patients for chronic lung allograft dysfunction (CLAD). Early chest CT should focus on pulmonary artery stenosis (risk factor for CLAD in this study). During the follow-up (at least 9 months post-LTx), parenchymal consolidations and pleural effusions were shown to be risk factors for CLAD, and death in subgroup analyses.

KEY POINTS

• Pulmonary artery stenosis (30-50%) on initial chest-CT following lung transplantation predicts CLAD HR = 4.5; CI [1.6-13.2]. • Pleural effusion and consolidations 1 year after lung transplantation predict CLAD and death. • Early evaluation of lung transplanted patients should evaluate pulmonary artery anastomosis.

Biomarkers for Chronic Lung Allograft Dysfunction: Ready for Prime Time?

Chronic lung allograft dysfunction (CLAD) remains a major hurdle impairing lung transplant outcome. Parallel to the better clinical identification and characterization of CLAD and CLAD phenotypes, there is an increasing urge to find adequate biomarkers that could assist in the earlier detection and differential diagnosis of CLAD phenotypes, as well as disease prognostication. The current status and state-of-the-art of biomarker research in CLAD will be discussed with a particular focus on radiological biomarkers or biomarkers found in peripheral tissue, bronchoalveolar lavage' and circulating blood' in which significant progress has been made over the last years. Ultimately, although a growing number of biomarkers are currently being embedded in the follow-up of lung transplant patients, it is clear that one size does not fit all. The future of biomarker research probably lies in the rigorous combination of clinical information with findings in tissue, bronchoalveolar lavage' or blood. Only by doing so, the ultimate goal of biomarker research can be achieved, which is the earlier identification of CLAD before its clinical manifestation. This is desperately needed to improve the prognosis of patients with CLAD after lung transplantation.

Characterization of chronic lung allograft dysfunction phenotypes using spectral and intrabreath oscillometry

Background: Chronic lung allograft dysfunction (CLAD) is the major cause of death beyond 2 years after lung transplantation and develops in 50% of all patients by 5 years post-transplant. CLAD is diagnosed on the basis of a sustained drop of 20% for at least 3 months in the forced expiratory volume (FEV₁), compared to the best baseline value achieved post-transplant. CLAD presents as two main phenotypes: bronchiolitis obliterans syndrome (BOS) is more common and has better prognosis than restrictive allograft syndrome (RAS). Respiratory oscillometry is a different modality of lung function testing that is highly sensitive to lung mechanics. The current study investigated whether spectral and intrabreath oscillometry can differentiate between CLAD-free, BOS- and RAS-CLAD at CLAD onset, i.e., at the time of the initial 20% drop in the FEV₁.

Methods: A retrospective, cross-sectional analysis of 263 double lung transplant recipients who underwent paired testing with oscillometry and spirometry at the Toronto General Pulmonary Function Laboratory from 2017 to 2022 was conducted. All pulmonary function testing and CLAD diagnostics were performed following international guidelines. Statistical analysis was conducted using multiple comparisons.

Findings: The RAS (n = 6) spectral oscillometry pattern differs from CLAD-free (n = 225) by right-ward shift of reactance curve similar to idiopathic pulmonary fibrosis whereas BOS (n = 32) has a pattern similar to obstructive lung disease. Significant differences were found in most spectral and intrabreath parameters between BOS, RAS, and time-matched CLAD-free patients. Post-hoc analysis revealed these differences were primarily driven by BOS instead of RAS. While no differences were found between CLAD-free and RAS patients with regards to spectral oscillometry, the intrabreath metric of reactance at end-inspiration (XeI) was significantly different (p < 0.05). BOS and RAS were differentiated by spectral oscillometry measure R5, and intrabreath resistance at end expiration, ReE (p < 0.05 for both).

Conclusion: Both spectral and intrabreath oscillometry can differentiate BOS-CLAD from CLAD-free states while intrabreath oscillometry, specifically XeI, can uniquely distinguish RAS-CLAD from CLAD-free. Spectral and intrabreath oscillometry offer complementary information regarding lung mechanics in CLAD patients to help distinguish the two phenotypes and could prove useful in prognostication.

Quantitative Multivolume Proton-Magnetic Resonance Imaging in Lung Transplant Recipients: Comparison With Computed Tomography and Spirometry

RATIONALE AND OBJECTIVES

Acute and chronic graft rejection remains the major problem in clinical surveillance of lung-transplanted patients and early detection of complications is of capital importance to allow the optimal therapeutic option. The aim of this study was to investigate the role of quantitative non contrast-enhanced magnetic resonance imaging (MRI) as a non-ionizing imaging modality to assess ventilation impairment in patients who have undergone lung transplantation, in comparison with quantitative computed tomography (CT) and spirometry.

MATERIALS AND METHODS

Ten lung-transplanted patients (39 ±12 years, forced-expiratory volume in 1 second (FEV1) = 81 ± 27%, forced vital capacity (FVC) = 87 ± 27%) were acquired in breath-hold at full-expiration and full-inspiration with 1.5T MRI and CT. Maps of expiratory-inspiratory difference in MR signal-intensity and CT-density were computed to estimate regional ventilation. Based on expiratory, inspiratory, and expiratory-inspiratory difference values, each pixel was classified as healthy (H), low ventilation (LV), air trapping (AT), and consolidation (C) and the percent extent of each class was quantified.

RESULTS

Overall, expiratory-inspiratory difference in MR signal-intensity correlated to CT-density (r = 0.64, p < 0.0001) and to FEV1 (ρ = 0.71, p = 0.02). The linear correlation between MRI and CT functional maps considering all the four classes is r = 0.93 (p < 0.0001). MRI percent volumes of H, AT, and C correlated to FEV1 %pred, with the highest correlation reported for AT (ρ = -0.82).

CONCLUSION

Results demonstrated a good agreement between MRI and CT ventilation imaging and between the corresponding percent volumes of lung damage. Quantitative MRI may represent an accurate non-ionizing imaging technique for longitudinal monitoring of lung transplant recipients.

Complications of Lung Transplantation: Update on Imaging Manifestations and Management

As lung transplantation has become the most effective definitive treatment option for end-stage chronic respiratory diseases, yearly rates of this surgery have been steadily increasing. Despite improvement in surgical techniques and medical management of transplant recipients, complications from lung transplantation are a major cause of morbidity and mortality. Some of these complications can be classified on the basis of the time they typically occur after lung transplantation, while others may occur at any time. Imaging studies, in conjunction with clinical and laboratory evaluation, are key components in diagnosing and monitoring these conditions. Therefore, radiologists play a critical role in recognizing and communicating findings suggestive of lung transplantation complications. A description of imaging features of the most common lung transplantation complications, including surgical, medical, immunologic, and infectious complications, as well as an update on their management, will be reviewed here. Keywords: Pulmonary, Thorax, Surgery, Transplantation Supplemental material is available for this article. © RSNA, 2021.

Quantitative inspiratory-expiratory chest CT to evaluate pulmonary involvement in pediatric hematopoietic stem-cell transplantation patients

Pulmonary complications following allogeneic hematopoietic stem-cell transplantation (HSCT) are a significant source of morbidity and complications may arise from a myriad of infectious and noninfectious sources. These complications may occur soon or many months post-transplantation and can have a broad range of outcomes. Surveillance for pulmonary involvement in the pediatric HSCT population can be challenging due to poor compliance with clinical pulmonary function testing, primarily spirometry, and there may be a role for clinical imaging to provide an additional means of monitoring, particularly in the era of clinical low-dose computed tomography (CT) protocols. In this single-site, retrospective study, a review of our institution's radiological and HSCT databases was conducted to assess the utility of a quantitative CT algorithm to describe ventilation abnormalities on high-resolution chest CT scans of pediatric HSCT patients. Thirteen non-contrast enhanced chest CT examinations acquired both in inspiration and expiration, from 12 deceased HSCT patients (median age at HSCT 10.4 years, median days of CT 162) were selected for the analysis. Also, seven age-matched healthy controls (median age 15.5) with non-contrast-enhanced inspiration-expiration chest CT were selected for comparison. We report that, compared to healthy age-matched controls, HSCT patients had larger percentages of poorly ventilated (median, 13.5% vs. 2.3%, p < .001) and air trapped (median 12.3% vs. 0%, p < .001) regions of lung tissue, suggesting its utility as a potential screening tool. Furthermore, there was wide variation within individual HSCT patients, supporting the use of multivolume CT and quantitative analysis to describe and phenotype post-transplantation lung involvement.

Lung Transplantation: CT Assessment of Chronic Lung Allograft Dysfunction (CLAD)

Chronic lung allograft rejection remains one of the major causes of morbi-mortality after lung transplantation. The term Chronic Lung Allograft Dysfunction (CLAD) has been proposed to describe the different processes that lead to a significant and persistent deterioration in lung function without identifiable causes. The two main phenotypes of CLAD are Bronchiolitis Obliterans Syndrome (BOS) and Restrictive Allograft Syndrome (RAS), each of them characterized by particular functional and imaging features. These entities can be associated (mixed phenotype) or switched from one to the other. If CLAD remains a clinical diagnosis based on spirometry, computed tomography (CT) scan plays an important role in the diagnosis and follow-up of CLAD patients, to exclude identifiable causes of functional decline when CLAD is first suspected, to detect early abnormalities that can precede the diagnosis of CLAD (particularly RAS), to differentiate between the obstructive and restrictive phenotypes, and to detect exacerbations and evolution from one phenotype to the other. Recognition of early signs of rejection is crucial for better understanding of physiopathologic pathways and optimal management of patients.

Lung Ultrasound to Phenotype Chronic Lung Allograft Dysfunction in Lung Transplant Recipients. A Prospective Observational Study

Background: Bronchiolitis obliterans syndrome (BOS) and restrictive allograft syndrome (RAS) are two distinct phenotypes of chronic lung allograft dysfunction (CLAD) in lung transplant (LTx) recipients. Contrary to BOS, RAS can radiologically present with a pleuroparenchymal fibroelastosis (PPFE) pattern. This study investigates lung ultrasound (LUS) to identify potential surrogate markers of PPFE in order to distinguish CLAD phenotype RAS from BOS. Methods: A prospective cohort study performed at a National Lung Transplantation Center during June 2016 to December 2017. Patients were examined with LUS and high-resolution computed tomography of the thorax (HRCT). Results: Twenty-five CLAD patients (72% males, median age of 54 years) were included, corresponding to 19/6 BOS/RAS patients. LUS-identified pleural thickening was more pronounced in RAS vs. BOS patients (5.6 vs. 2.9 mm) compatible with PPFE on HRCT. LUS-identified pleural thickening as an indicator of PPFE in RAS patients’ upper lobes showed a sensitivity of 100% (95% CI; 54–100%), specificity of 100% (95% CI; 82–100%), PPV of 100% (95% CI; 54–100%), and NPV of 100% (95% CI; 82–100%). Conclusion: Apical pleural thickening detected by LUS and compatible with PPFE on HRCT separates RAS from BOS in patients with CLAD. We propose LUS as a supplementary tool for initial CLAD phenotyping.

Lung Transplant Pathology: An Overview on Current Entities and Procedures

Alloimmune reactions are, besides various infections, the major cause for impaired lung allograft function following transplant. Acute cellular rejection is not only a major trigger of acute allograft failure but also contributes to development of chronic lung allograft dysfunction. Analogous to other solid organ transplants, acute antibody-mediated rejection has become a recognized entity in lung transplant pathology. Adequate sensitivity and specificity in the diagnosis of alloimmune reactions in the lung can only be achieved by synoptic analysis of histopathologic, clinical, and radiological findings together with serologic and microbiologic findings.

Noninvasive methods for detection of chronic lung allograft dysfunction in lung transplantation

Lung transplantation (LTx) is the only therapeutic option for end-stage lung diseases. Chronic lung allograft dysfunction (CLAD), which manifests as airflow restriction and/or obstruction, is the primary factor limiting the long-term survival of patients after surgery. According to histopathological and radiographic findings, CLAD comprises two phenotypes, bronchiolitis obliterans syndrome and restrictive allograft syndrome. Half of all lung recipients will develop CLAD in 5 years, and this rate may increase up to 75% 10 years after surgery owing to the paucity in accurate and effective early detection and treatment methods. Recently, many studies have presented noninvasive methods for detecting CLAD and improving diagnosis and intervention. However, the significance of accurately detecting CLAD remains controversial. We reviewed published studies that have presented noninvasive methods for detecting CLAD to highlight the current knowledge on clinical symptoms, spirometry, imaging examinations, and other methods to detect the disease.

Variation in Time to Peak Values for Different Lung Function Parameters After Double Lung Transplantation

BACKGROUND

Establishment of baseline values for forced expiratory volume in the first second (FEV₁), forced vital capacity (FVC), or total lung capacity (TLC) is required when diagnosing and phenotyping chronic lung allograft dysfunction after lung transplant. It is generally accepted that the baseline (peak) values of these parameters occur simultaneously, but this assumption has not been substantiated for TLC.

METHODS

All lung function measurements in all double lung transplant recipients from a single center in the period from 1992-2014 were included. Time to baseline FEV₁ was assessed according to standards from the International Society for Heart and Lung Transplantation, and time to peak FVC, TLC, and diffusion capacity for carbon monoxide were evaluated.

RESULTS

A total of 288 double lung transplants surviving more than 3 months after transplant were included. Baseline FEV₁ occurred at a median of 0.77 years post transplant and was statistically different from median times to the peak FVC (1.02 years), to peak TLC (1.37 years), and to peak diffusion capacity for carbon monoxide 1.04 years post transplant (all log-rank P < .001). At the time of baseline FEV1, FVC, and TLC were at a mean of 96% and 95% of their peak values, respectively.

CONCLUSION

The peak lung function is reached at different time points for different parameters post transplant with FEV₁ baseline occurring first. For most patients values of FVC and TLC obtained at time for baseline FEV₁ is a good estimate of peak values, but in a small percentage of patients this procedure may jeopardize phenotyping of chronic lung allograft dysfunction based solely on lung function parameters.

Imaging indications and findings in evaluation of lung transplant graft dysfunction and rejection

Lung transplantation is a treatment option in end-stage lung disease. Complications can develop along a continuum in the immediate or longer post-transplant period, including surgical and technical complications, primary graft dysfunction, rejection, infections, post-transplant lymphoproliferative disorder, and recurrence of the primary disease. These complications have overlapping clinical and imaging features and often co-exist. Time of onset after transplant is helpful in narrowing the differential diagnosis. In the early post transplantation period, imaging findings are non-specific and need to be interpreted in the context of the clinical picture and other investigations. In contrast, imaging plays a key role in diagnosing and monitoring patients with chronic lung allograft dysfunction. The goal of this article is to review primary graft dysfunction, acute rejection, and chronic rejection with emphasis on the role of imaging, pathology findings, and differential diagnosis.

Use of CT-SCAN score and volume measures to early identify restrictive allograft syndrome in single lung transplant recipients

BACKGROUND

Restrictive allograft syndrome (RAS) after lung transplantation (LTx) is associated with the poorer graft survival in patients with chronic lung allograft dysfunction (CLAD). Nevertheless, its diagnostic criteria have not been clearly defined after single-LTx (SLTx). Hence, we studied an SLTx cohort with CLAD to investigate the utility of both computed tomography (CT)-score/volume measures and functional spirometric criteria for the early identification of RAS in this population.

METHODS

We included 51 patients with SLTx (17 RAS, 17 bronchiolitis obliterans syndrome [BOS], and 17 stable condition). The criteria for RAS diagnosis in SLTx included forced vital capacity (FVC) <80% baseline (BL) or forced expiratory volume in 1 second (FEV1) <80% BL with an FEV1/FVC ratio^{unchanged or >0.7} and persistent CT-scan-lung opacities. We defined 4 time points (T): T-baseline, T-onset (first CT-scan-opacities), T-follow-up, and T-last.

RESULTS

In patients with RAS, the spirometric criteria for RAS at T-onset were reached in only 47% (FVC decline <80% BL [(29%] or FEV1 <80% BL/ratio^{unchanged or >0.7} [41%]), whereas at the same T-onset date, the graft CT-score increased to 5 (4-6) vs 1 (0-2) at baseline (p < 0.001) (CT - score ≥2 at T-onset in 100% and ΔCT - score ≥2 in 74% of patients with RAS), and the median CT-scan graft volume decreased to 1,722 ml (vs 1,796 ml at T-baseline, p = 0.003) (decreased CT-graft - volume <90% BL in 50% of patients). In contrast, in patients with BOS, CT-score/volume were unchanged at T-onset vs T-baseline (p = 0.8, p = 0.68, respectively).

CONCLUSION

Our results suggest that the use of a simple CT-score and to a lesser extent, CT-volume measures, might allow for the early identification and/or prediction of RAS in SLTx rather than functional criteria.

Pirfenidone in restrictive allograft syndrome after lung transplantation: A case series

Pirfenidone may attenuate the decline of pulmonary function in restrictive allograft syndrome (RAS) after lung transplantation. We retrospectively assessed all lung transplant recipients with RAS who were treated with pirfenidone for at least 3 months (n = 11) in our lung transplant center and report on their long-term outcomes following initiation of pirfenidone. Main outcome parameters included evolution of pulmonary function and overall survival. Pirfenidone appears to attenuate the decline in forced vital capacity and forced expiratory volume in 1 second. Notably, 3 patients were bridged to redo-transplantation with pirfenidone for 11 (5-12) months and are currently alive, while 3 other patients demonstrate long-term stabilization of pulmonary function after 26.6 (range 18.4-46.6) months of treatment. Median overall 3-year survival after RAS diagnosis was 54.5%. Subjective intolerance, mainly anorexia and nausea, necessitating pirfenidone dose de-escalation in 55% of patients, as well as calcineurin dose increase requirements with about 20% are important complications during pirfenidone treatment after lung transplantation. Our findings provide further evidence that pirfenidone appears to be safe and may attenuate the rate of decline in lung function in patients with RAS, but the actual clinical benefit cannot be assessed in the context of this study design and requires further investigation in a larger randomized trial.

Prognostic significance of early pulmonary function changes after onset of chronic lung allograft dysfunction

BACKGROUND

Chronic lung allograft dysfunction (CLAD), including the phenotypes of bronchiolitis obliterans syndrome (BOS) and restrictive CLAD (R-CLAD), represents the leading cause of late death after lung transplantation. Little is known, however, regarding the natural history or prognostic significance of pulmonary function changes after the onset of these conditions. We examined changes in forced expiratory volume in 1 second (FEV₁) and forced vital capacity (FVC) over the first 18 months after CLAD. We also sought to determine whether lung function changes occurring early after CLAD impact longer term outcomes.

METHODS

We performed a retrospective analysis of 216 bilateral lung recipients with CLAD, which included those with R-CLAD (n = 65) or BOS (n = 151). The course of FEV₁ and FVC after CLAD was described. Cox proportional hazards models were used to evaluate the impact of a ≥10% decline in FEV₁ or FVC within the first 6 months of CLAD on graft loss after that time.

RESULTS

Lung recipients with CLAD, whether BOS or R-CLAD, had the largest decreases in FEV₁ and FVC within the first 6 months after onset. Moreover, a decline in FEV₁ or FVC of ≥10% within the first 6 months after CLAD was associated with a significantly increased hazard for graft loss after that time (hazard ratio [HR] = 3.17, 95% confidence interval [CI] 1.56 to 6.42, p = 0.001, and HR = 2.80, 95% CI 1.66 to 4.70, p ≤ 0.001, respectively), an effect observed in both BOS and R-CLAD patients.

CONCLUSIONS

Early physiologic changes after CLAD were independently associated with graft loss. This suggests lung function changes after CLAD, specifically a ≥10% decline in FEV₁ or FVC, could be a surrogate measure of graft survival.

Human leukocyte antigens antibodies after lung transplantation: Primary results of the HALT study

Donor-specific antibodies (DSA) to mismatched human leukocyte antigens (HLA) are associated with worse outcomes after lung transplantation. To determine the incidence and characteristics of DSA early after lung transplantation, we conducted a prospective multicenter observational study that used standardized treatment and testing protocols. Among 119 transplant recipients, 43 (36%) developed DSA: 6 (14%) developed DSA only to class I HLA, 23 (53%) developed DSA only to class II HLA, and 14 (33%) developed DSA to both class I and class II HLA. The median DSA mean fluorescence intensity (MFI) was 3197. We identified a significant association between the Lung Allocation Score and the development of DSA (HR = 1.02, 95% CI: 1.001-1.03, P = .047) and a significant association between DSA with an MFI ≥ 3000 and acute cellular rejection (ACR) grade ≥ A2 (HR = 2.11, 95% CI: 1.04-4.27, P = .039). However, we did not detect an association between DSA and survival. We conclude that DSA occur frequently early after lung transplantation, and most target class II HLA. DSA with an MFI ≥ 3000 have a significant association with ACR. Extended follow-up is necessary to determine the impact of DSA on other important outcomes.

High-Resolution CT Findings of Obstructive and Restrictive Phenotypes of Chronic Lung Allograft Dysfunction: More Than Just Bronchiolitis Obliterans Syndrome

OBJECTIVE

The purpose of this article is to review the high-resolution CT characteristics of individual obstructive and restrictive chronic lung allograft dysfunction (CLAD) phenotypes to aid in making accurate diagnoses and guiding treatment.

CONCLUSION

Long-term survival and function after lung transplant are considerably worse compared with after other organ transplants. CLAD is implicated as a major limiting factor for long-term graft viability. Historically thought to be a single entity, bronchiolitis obliterans syndrome, CLAD is actually a heterogeneous group of disorders with distinct subtypes.

The aging lung: tissue telomere shortening in health and disease

Background

Telomere shortening has been associated with several lung diseases. However, telomere length is generally measured in peripheral blood leucocytes rather than in lung tissue, where disease occurs. Consequently, telomere dynamics have not been established for the normal human lung nor for diseased lung tissue. We hypothesized an age- and disease-dependent shortening of lung tissue telomeres.

Methods

At time of (re-)transplantation or autopsy, 70 explant lungs were collected: from unused donors (normal, n = 13) and patients with cystic fibrosis (CF, n = 12), chronic obstructive pulmonary disease (COPD, n = 11), chronic hypersensitivity pneumonitis (cHP, n = 9), bronchiolitis obliterans syndrome (BOS) after prior transplantation (n = 11) and restrictive allograft syndrome (RAS) after prior transplantation (n = 14). Lungs were inflated, frozen and then scanned using CT. Four tissue cores from distinct lung regions were sampled for analysis. Disease severity was evaluated using CT and micro CT imaging. DNA was extracted from the samples and average relative telomere length (RTL) was determined using real-time qPCR.

Results

The normal lungs showed a decrease in RTL with age (p < 0.0001). Of the diseased lungs, only BOS and RAS showed significant RTL decrease with increasing lung age (p = 0.0220 and p = 0.0272 respectively). Furthermore, we found that RTL showed considerable variability between samples within both normal and diseased lungs. cHP, BOS and RAS lungs had significant shorter RTL in comparison with normal lungs, after adjustment for lung age, sex and BMI (p < 0.0001, p = 0.0051 and p = 0.0301 respectively). When investigating the relation between RTL and regional disease severity in CF, cHP and RAS, no association was found.

Conclusion

These results show a progressive decline in telomere length with age in normal, BOS and RAS lungs. cHP, BOS and RAS lungs demonstrated shorter RTL compared to normal lungs. Lung tissue RTL does not associate with regional disease severity within the lung. Therefore, tissue RTL does not seem to fully reflect peripheral blood telomere length.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0794-z) contains supplementary material, which is available to authorized users.

Inhibition of T Cell Alloreactivity by Bronchial Epithelium Is Impaired in Lung Transplant Recipients, Through Pathways Involving TGF-β, IL-10 and HLA-G

BACKGROUND

Bronchiolitis obliterans syndrome (BOS) after lung transplantation (LTx) results from bronchial epithelial cell (BECs) damages, thought to be orchestrated by T cells primed by antigen-presenting cell presenting alloantigens. In this cell cross-talk, BECs are also suspected to play a pivotal immunosuppressive role in T cell alloreactivity. We studied the immunomodulating role of BECs in a human ex vivo model of allogeneic T cell response, both in healthy subjects and LTx recipients.

METHODS

BECs from 35 LTx recipients (n = 22 stable, n = 13 BOS) and healthy controls (n = 25) were cultured as primary cell cultures. Their inhibitory capacities through the involvement of tolerogenic molecules (HLA-G, TGF-β, and IL-10) were tested on a mixed lymphocyte reaction between antigen-presenting cells and recipient T cells.

RESULTS

Control BECs inhibited T cell alloproliferation by a mean of 53 ± 7%. This inhibitory effect of BECs was significantly reduced in the stable LTx group (24 ± 8%, P = 0.009), but not in the BOS TxP group (53 ± 10%, P = 0.97). Neutralization of HLA-G, TGF-β, and IL-10 partially restored T cell alloproliferation, arguing for their involvement in the immunosuppressive effect of BECs. BECs culture supernatant from stable LTx patients with impaired BEC properties showed a skewed Th2-type secretion profile (high IL-4/IFN-γ ratio).

CONCLUSIONS

The inhibitory properties of BECs are dysregulated in stable LTx recipients, which could suggest their instrumental role in the initiation of BOS process and potential targeted therapies.

Update in Chronic Lung Allograft Dysfunction

Chronic lung allograft dysfunction (CLAD) is the major limitation to posttransplant survival. This review highlights the evolving definition of CLAD, risk factors, treatment, and expected outcomes after the development of CLAD.

Chronic lung allograft dysfunction phenotypes and treatment

Chronic lung allograft dysfunction (CLAD) remains a major hurdle limiting long-term survival post lung transplantation. Given the clinical heterogeneity of CLAD, recently two phenotypes of CLAD have been defined [bronchiolitis obliterans syndrome (BOS) vs. restrictive allograft syndrome (RAS) or restrictive CLAD (rCLAD)]. BOS is characterized by an obstructive pulmonary function, air trapping on CT and obliterative bronchiolitis (OB) on histopathology, while RAS/rCLAD patients show a restrictive pulmonary function, persistent pleuro-parenchymal infiltrates on CT and pleuroparenchymal fibro-elastosis on biopsies. Importantly, the patients with RAS/rCLAD have a severely limited survival post diagnosis of 6-18 months compared to 3-5 years after BOS diagnosis. In this review, we will review historical evidence for this heterogeneity and we will highlight the clinical, radiological, histopathological characteristics of both phenotypes, as well as their risk factors. Treatment of CLAD remains troublesome, nevertheless, we will give an overview of different treatment strategies that have been tried with some success. Adequate phenotyping remains difficult but is clearly needed for both clinical and scientific purposes.

"White-Out" After Lung Transplantation: A Multicenter Cohort Description of Late Acute Graft Failure

Graft failure represents a leading cause of mortality after organ transplantation. Acute late-onset graft failure has not been widely reported. The authors describe the demographics, CT imaging-pathology findings, and treatment of patients presenting with the latter. A retrospective review was performed of lung transplant recipients at two large-volume centers. Acute late-onset graft failure was defined as sudden onset of bilateral infiltrates with an oxygenation index <200 without identifiable cause or concurrent extrapulmonary organ failure. Laboratory, bronchoalveolar lavage (BAL), radiology, and histology results were assessed. Between 2005 and 2016, 21 patients were identified. Median survival was 19 (IQR 13-36) days post onset. Twelve patients (57%) required intensive care support at onset, 12 (57%) required mechanical ventilation, and 6 (29%) were placed on extracorporeal life support. Blood and BAL analysis revealed elevated neutrophilia, with CT demonstrating diffuse ground-glass opacities. Transbronchial biopsy samples revealed acute fibrinoid organizing pneumonia (AFOP), organizing pneumonia, and diffuse alveolar damage (DAD). Assessment of explanted lungs confirmed AFOP and DAD but also identified obliterative bronchiolitis. Patients surviving to discharge without redo transplantation (n = 2) subsequently developed restrictive allograft syndrome. This study describes acute late-onset graft failure in lung allograft recipients, without known cause, which is associated with a dismal prognosis.

Pleuroparenchymal fibroelastosis: the prevalence of secondary forms in hematopoietic stem cell and lung transplantation recipients

PURPOSE

Pleuroparenchymal fibroelastosis (PPFE) is a rare form of interstitial pneumonia, characterized by elastotic fibrosis involving the pleura and subpleural parenchyma, predominantly in the upper lobes. PPFE can be either idiopathic or secondary and mostly occurs as a late complication of lung or hematopoietic stem cell transplantation (HSCT). The aim of this study was to evaluate the prevalence of secondary forms in transplant recipients.

METHODS

An expert thoracic radiologist retrospectively reviewed high-resolution computed tomography exams of 700 HSCT recipients and 53 lung transplant recipients from the database of the Radiology Department of S. Orsola-Malpighi Hospital dating back from 2007. For each case that radiologically fulfilled PPFE criteria, the following details were retrieved: clinical characteristics, laboratory and functional data, pathologic findings (obtained from one patient) and metabolic data (obtained from three patients).

RESULTS

Six cases clinically and radiologically consistent with PPFE were identified: two HSCT recipients (0.28%) and four lung transplant recipients (7.54%).

CONCLUSION

In this study, PPFE was strongly associated with lung transplants as a late complication, with a prevalence of 7.54%.

Airway remodelling in the transplanted lung

Following lung transplantation, fibrotic remodelling of the small airways has been recognized for almost 5 decades as the main correlate of chronic graft failure and a major obstacle to long-term survival. Mainly due to airway fibrosis, pulmonary allografts currently show the highest attrition rate of all solid organ transplants, with a 5-year survival rate of 58 % on a worldwide scale. The observation that these morphological changes are not just the hallmark of chronic rejection but rather represent a manifestation of a multitude of alloimmune-dependent and -independent injuries was made more recently, as was the discovery that chronic lung allograft dysfunction manifests in different clinical phenotypes of respiratory impairment and corresponding morphological subentities. Although recent years have seen considerable advances in identifying and categorizing these subgroups on the basis of clinical, functional and histomorphological changes, as well as susceptibility to medicinal treatment, this process is far from over. Since the actual pathophysiological mechanisms governing airway remodelling are still only poorly understood, diagnosis and therapy of chronic lung allograft dysfunction presents a major challenge to clinicians, radiologists and pathologists alike. Here, we review and discuss the current state of the literature on chronic lung allograft dysfunction and shed light on classification systems, corresponding clinical and morphological changes, key cellular players and underlying molecular pathways, as well as on emerging diagnostic and therapeutic approaches.

Phenotyping Chronic Lung Allograft Dysfunction Using Body Plethysmography and Computed Tomography

Restrictive subtype of chronic lung allograft dysfunction (CLAD) was recently described after lung transplantation. This study compares different definitions of a restrictive phenotype in CLAD patients and impact on survival. Eighty-nine CLAD patients out of 1191 screened patients (September 1987 to July 2012) were included as complete longitudinal lung volume measurements and chest computed tomography (CT) after CLAD onset was available. CT findings and lung volumes were quantified and survival was calculated for distinctive groups and predictive factors for worse survival were investigated. Graft survival in patients with total lung capacity (TLC) between 90% and 81% of baseline (BL) (n = 13, 15%) in CLAD course was similar to those with TLC >90% BL (n = 64, 56%; log-rank test p = 0.9). Twelve patients (13%) developed a TLC ≤80% BL and 10 (11%) had significant parenchymal changes on CT, of whom 6 (46%) also had TLC ≤80% BL. CT changes correlated with TLC ≤80% BL (Φ-coefficient = 0.48, p = 0.001). Patients with either TLC ≤80% or significant CT changes (n = 16, 18%) had a significantly reduced survival (log-rank p < 0.001). Forced vital capacity loss at CLAD onset was associated with poorer survival but did not correlate with the TLC or CT changes. A restrictive subtype of CLAD may be defined by either TLC ≤80% BL or severe parenchymal changes on chest CT.

Parametric Response Mapping of Bronchiolitis Obliterans Syndrome Progression After Lung Transplantation

Bronchiolitis obliterans syndrome (BOS) remains a major complication after lung transplantation. Air trapping and mosaic attenuation are typical radiological features of BOS; however, quantitative evaluation remains troublesome. We evaluated parametric response mapping (PRM, voxel-to-voxel comparison of inspiratory and expiratory computed tomography [CT] scans) in lung transplant recipients diagnosed with BOS (n = 20) and time-matched stable lung transplant recipients (n = 20). Serial PRM measurements were performed prediagnosis, at time of BOS diagnosis, and postdiagnosis (T_pre , T₀ , and T_post , respectively), or at a postoperatively matched time in stable patients. PRM results were correlated with pulmonary function and confirmed by microCT analysis of end-stage explanted lung tissue. Using PRM, we observed an increase in functional small airway disease (fSAD), from T_pre to T₀ (p = 0.006) and a concurrent decrease in healthy parenchyma (p = 0.02) in the BOS group. This change in PRM continued to T_post , which was significantly different compared to the stable patients (p = 0.0002). At BOS diagnosis, the increase in fSAD was strongly associated with a decrease in forced expiratory volume in 1 s (p = 0.011). Micro-CT confirmed the presence of airway obliteration in a sample of a BOS patient identified with 67% fSAD by PRM. We demonstrated the use of PRM as an adequate output to monitor BOS progression in lung transplant recipients.

Comprehensive Care of the Lung Transplant Patient

Lung transplantation has evolved into a life-saving treatment with improved quality of life for patients with end-stage respiratory failure unresponsive to other medical or surgical interventions. With improving survival rates, the number of lung transplant recipients with preexisting and posttransplant comorbidities that require attention continues to increase. A partnership between transplant and nontransplant care providers is necessary to deliver comprehensive and optimal care for transplant candidates and recipients. The goals of this partnership include timely referral and assistance with transplant evaluation, optimization of comorbidities and preparation for transplantation, management of common posttransplant medical comorbidities, immunization, screening for malignancy, and counseling for a healthy lifestyle to maximize the likelihood of a good outcome. We aim to provide an outline of the main aspects of the care of candidates for and recipients of lung transplants for nontransplant physicians and other care providers.

Predictors of survival in restrictive chronic lung allograft dysfunction after lung transplantation

BACKGROUND

Chronic lung allograft dysfunction (CLAD) is the main factor limiting long-term survival after lung transplantation. Besides bronchiolitis obliterans syndrome, a restrictive phenotype of CLAD (rCLAD) exists, which is associated with poor prognosis after diagnosis. However, survival determinants for rCLAD remain to be elucidated. Our aim in this study was to establish parameters predicting survival in patients with rCLAD.

METHODS

All patients diagnosed with rCLAD in 2 lung transplant centers were assessed in a retrospective manner. Various clinical parameters [demography, pulmonary function, bronchoalveolar lavage (BAL), histopathology, radiology and blood differentials] at rCLAD diagnosis were correlated with graft survival using unadjusted and adjusted analysis.

RESULTS

A total of 53 patients with rCLAD were included with a median graft survival after diagnosis of 1.1 years. Univariate analysis demonstrated that lower-lobe-dominant or diffuse infiltrates on chest computed tomography, presence of an identifiable trigger before rCLAD onset, lymphocytic bronchiolitis, increased BAL neutrophilia, increased BAL eosinophilia and increased blood eosinophils were associated with inferior graft survival after rCLAD diagnosis. Multivariate analysis confirmed the association of location of infiltrates and blood eosinophilia on graft survival.

CONCLUSION

In this study we have identified parameters associated with graft survival after rCLAD diagnosis that may be useful to predict prognosis.

What can happen after lung transplantation and the importance of the time since transplantation: radiological review of post-transplantation complications

Lung transplantation is the best treatment option in the final stages of diseases such as cystic fibrosis, pulmonary hypertension, chronic obstructive pulmonary disease, or idiopathic pulmonary fibrosis. Better surgical techniques and advances in immunosuppressor treatments have increased survival in lung transplant recipients, making longer follow-up necessary because complications can occur at any time after transplantation. For practical purposes, complications can be classified as early (those that normally occur within two months after transplantation), late (those that normally occur more than two months after transplantation), or time-independent (those that can occur at any time after transplantation). Many complications have nonspecific clinical and radiological manifestations, so the time factor is key to narrow the differential diagnosis. Imaging can guide interventional procedures and can detect complications early. This article aims to describe and illustrate the complications that can occur after lung transplantation from the clinical and radiological viewpoints so that they can be detected as early as possible.

Chronic lung allograft dysfunction: evolving practice

PURPOSE OF REVIEW

Chronic lung allograft dysfunction (CLAD) was recently introduced as an overarching term covering different phenotypes of chronic allograft dysfunction, including obstructive CLAD (bronchiolitis obliterans syndrome), restrictive CLAD (restrictive allograft syndrome) and graft dysfunction due to causes not related to chronic rejection. In the present review, we will highlight the latest insights and current controversies regarding the new CLAD terminology, underlying pathophysiologic mechanisms, diagnostic approach and possible treatment options.

RECENT FINDINGS

Different pathophysiological mechanisms are clearly involved in clinically distinct phenotypes of chronic rejection, as is reflected by differences in histology, allograft function and imaging. Therefore, not all CLAD patients may equally benefit from specific therapies.

SUMMARY

The recent introduction of CLAD importantly changed the clinical practice in lung transplant recipients. Given the relative low accuracy of the current diagnostic tools, future research should focus on specific biomarkers, more sensitive pulmonary function parameters and imaging techniques for timely CLAD diagnosis and phenotyping. Personalized or targeted therapeutic options for adequate prevention and treatment of CLAD are required.

Longitudinal Forced Vital Capacity Monitoring as a Prognostic Adjunct after Lung Transplantation

RATIONALE

After lung transplantation, spirometric values are routinely followed to assess graft function. FEV1 is used to characterize chronic allograft dysfunction, whereas the course of FVC change has been less acknowledged and rarely used.

OBJECTIVES

To better understand the temporal relationship and prognostic ability of FEV1 and FVC decline after lung transplantation.

METHODS

Serial FEV1 and FVC values were studied among 205 bilateral lung transplant recipients. Different decline patterns were characterized and evaluated for prognostic value via restricted mean modeling of mortality and times to other pertinent events.

MEASUREMENTS AND MAIN RESULTS

Baseline FEV1 was achieved earlier than baseline FVC (median, 296 vs. 378 d; P < 0.0001). Decline in FEV1 or FVC from their respective post-transplant baselines occurred in 85 patients (41%). Fifty-nine of 85 (69%) had an isolated FEV1 decline, with 80% later meeting the FVC decline criterion. This subsequent FVC decline was associated with worsening FEV1 and lower median survival. Twenty-five of 85 patients (29%) demonstrated concurrent FEV1 and FVC decline. Patients with concurrent decline had higher 1- and 5-year mortality rates (1-yr, 53% vs. 18%, P < 0.0001; 5-yr, 61% vs. 48%, P = 0.001). These patients were more likely to have rapid-onset of spirometry decline (P = 0.05) and lower FEV1% predicted (P = 0.04) at presentation.

CONCLUSIONS

FVC decline from its post-transplant baseline provides valuable prognostic information. Concurrent FEV1 and FVC decline identifies patients with fulminant, rapid deterioration and is the strongest clinical predictor of poor survival. Subsequent FVC decline in patients with an initial isolated FEV1 decline identifies disease progression and portends poor prognosis.

Low-dose computed tomography volumetry for subtyping chronic lung allograft dysfunction

BACKGROUND

The long-term success of lung transplantation is challenged by the development of chronic lung allograft dysfunction (CLAD) and its distinct subtypes of bronchiolitis obliterans syndrome (BOS) and restrictive allograft syndrome (RAS). However, the current diagnostic criteria for CLAD subtypes rely on total lung capacity (TLC), which is not always measured during routine post-transplant assessment. Our aim was to investigate the utility of low-dose 3-dimensional computed tomography (CT) lung volumetry for differentiating RAS from BOS.

METHODS

This study was a retrospective evaluation of 63 patients who had developed CLAD after bilateral lung or heart‒lung transplantation between 2006 and 2011, including 44 BOS and 19 RAS cases. Median post-transplant follow-up was 65 months in BOS and 27 months in RAS. The median interval between baseline and the disease-onset time-point for CT volumetry was 11 months in both BOS and RAS. Chronologic changes and diagnostic accuracy of CT lung volume (measured as percent of baseline) were investigated.

RESULTS

RAS showed a significant decrease in CT lung volume at disease onset compared with baseline (mean 3,916 ml vs 3,055 ml when excluding opacities, p < 0.0001), whereas BOS showed no significant post-transplant change (mean 4,318 ml vs 4,396 ml, p = 0.214). The area under the receiver operating characteristic curve of CT lung volume for differentiating RAS from BOS was 0.959 (95% confidence interval 0.912 to 1.01, p < 0.0001) and the calculated accuracy was 0.938 at a threshold of 85%.

CONCLUSION

In bilateral lung or heart‒lung transplant patients with CLAD, low-dose CT volumetry is a useful tool to differentiate patients who develop RAS from those who develop BOS.

Current views on chronic rejection after lung transplantation

Chronic lung allograft dysfunction (CLAD) was recently introduced as an overarching term mainly to classify patients with chronic rejection after lung transplantation, although other conditions may also qualify for CLAD. Initially, only the development of a persistent and obstructive pulmonary function defect, clinically identified as bronchiolitis obliterans syndrome (BOS), was considered as chronic rejection, if no other cause could be identified. It became clear in recent years that some patients do not qualify for this definition, although they developed a chronic and persistent decrease in FEV1 , without another identifiable cause. As the pulmonary function decline in these patients was rather restrictive, this was called restrictive allograft syndrome (RAS). In the present review, we will further elaborate on these two CLAD phenotypes, with specific attention to the diagnostic criteria, the role of pathology and imaging, the risk factors, outcome, and the possible treatment options.

Restrictive chronic lung allograft dysfunction: Where are we now?

Chronic lung allograft dysfunction (CLAD) remains a frequent and troublesome complication after lung transplantation. Apart from bronchiolitis obliterans syndrome (BOS), a restrictive phenotype of CLAD (rCLAD) has recently been recognized, which occurs in approximately 30% of CLAD patients. The main characteristics of rCLAD include a restrictive pulmonary function pattern with a persistent decline in lung function (FEV1, FVC and TLC), persistent parenchymal infiltrates and (sub)pleural thickening on chest CT scan, as well as pleuroparenchymal fibroelastosis and obliterative bronchiolitis on histopathologic examination. Once diagnosed, median survival is only 6 to 18 months compared with 3 to 5 years with BOS. In this perspective we review the historic evidence for rCLAD and describe the different diagnostic criteria and prognosis. Furthermore, we elaborate on the typical radiologic and histopathologic presentations of rCLAD and highlight risk factors and mechanisms. Last, we summarize some opportunities for further research including the urgent need for adequate therapy. In this perspective we not only assess the current knowledge, but also clarify the existing gaps in understanding this increasingly recognized complication after lung transplantation.