Spirometric Obstructive Lung Function Pattern Early After Lung Transplantation

Shah P, Mathew J, Kong H, Charya A, Luikart H, Aryal S, Nathan SD, Orens JB, Khush KK, Kyoo Jang M, Agbor-Enoh S. Baseline Lung Allograft Dysfunction After Bilateral Lung Transplantation Is Associated With an Increased Risk of Death: Results From a Multicenter Cohort Study

Background

A prior single-center, retrospective cohort study identified baseline lung allograft dysfunction (BLAD) as a risk factor for death in bilateral lung transplant recipients. In this multicenter prospective cohort study, we test the association of BLAD with death in bilateral lung transplant recipients, identify clinical risk factors for BLAD, and assess its association with allograft injury on the molecular level.

Methods

This multicenter, prospective cohort study included 173 bilateral lung transplant recipients that underwent serial pulmonary function testing and plasma collection for donor-derived cell-free DNA at prespecified time points. BLAD was defined as failure to achieve ≥80% predicted for both forced expiratory volume in 1 s and forced vital capacity after lung transplant, on 2 consecutive measurements at least 3 mo apart.

Results

BLAD was associated with increased risk of death (hazard ratio, 1.97; 95% confidence interval [CI], 1.05-3.69; P = 0.03) but not chronic lung allograft dysfunction alone (hazard ratio, 1.60; 95% CI, 0.87-2.95; P = 0.13). Recipient obesity (odds ratio, 1.69; 95% CI, 1.15-2.80; P = 0.04) and donor age (odds ratio, 1.03; 95% CI, 1.02-1.05; P = 0.004) increased the risk of developing BLAD. Patients with BLAD did not demonstrate higher log10(donor-derived cell-free DNA) levels compared with no BLAD (slope [SE]: -0.0095 [0.0007] versus -0.0109 [0.0007]; P = 0.15).

Conclusions

BLAD is associated with an increased risk of death following lung transplantation, representing an important posttransplant outcome with valuable prognostic significance; however, early allograft specific injury on the molecular level does not increase the risk of BLAD, supporting further mechanistic insight into disease pathophysiology.

Significance of Best Spirometry in the First Year After Bilateral Lung Transplantation: Association With 3-Year Outcomes

BACKGROUND

Spirometry is the cornerstone of monitoring allograft function after lung transplantation (LT). We sought to determine the association of variables on best spirometry during the first year after bilateral LT with 3-year posttransplant survival.

METHODS

We reviewed charts of patients who survived at least 3 months after bilateral LT (n = 157; age ± SD: 54 ± 13 y, male:female = 91:66). Best spirometry was calculated as the average of 2 highest measurements at least 3 weeks apart during the first year. Airway obstruction was defined as forced expiratory volume in 1-second (FEV1)/forced vital capacity (FVC) ratio <0.7. Survival was compared based on the ventilatory defect and among groups based on the best FEV1 and FVC measurements (>80%, 60%-80%, and <60% predicted). Primary outcome was 3-year survival.

RESULTS

Overall, 3-year survival was 67% (n = 106). Obstructive defect was uncommon (7%) and did not have an association with 3-year survival (72% versus 67%, P = 0.7). Although one-half patients achieved an FVC>80% predicted (49%), 1 in 5 (19%) remained below 60% predicted. Irrespective of the type of ventilatory defect, survival worsened as the best FVC (% predicted) got lower (>80: 80.8%; 60-80: 63.3%; <60: 40%; P < 0.001). On multivariate logistic regression analysis, after adjusting for age, gender, transplant indication, and annual bronchoscopy findings, best FVC (% predicted) during the first year after LT was independently associated with 3-year survival.

CONCLUSIONS

A significant proportion of bilateral LT patients do not achieve FVC>80% predicted. Although the type of ventilatory defect on best spirometry does not predict survival, failure to achieve FVC>80% predicted during the first year was independently associated with 3-year mortality.

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.

Prophylactic Azithromycin Therapy After Lung Transplantation: Post hoc Analysis of a Randomized Controlled Trial

Prophylactic azithromycin treatment has been demonstrated to improve freedom from bronchiolitis obliterans syndrome (BOS) 2 years after lung transplantation (LTx). In the current study, we re-evaluated the long-term effects of this prophylactic approach in view of the updated classification system for chronic lung allograft dysfunction (CLAD). A retrospective, intention-to-treat analysis of a randomized controlled trial comparing prophylactic treatment with placebo (n = 43) versus azithromycin (n = 40) after LTx was performed. Graft dysfunction (CLAD), graft loss (retransplantation, mortality), evolution of pulmonary function and functional exercise capacity were analyzed 7 years after inclusion of the last study subject. Following LTx, 22/43 (51%) patients of the placebo group and 11/40 (28%) patients of the azithromycin group ever developed CLAD (p = 0.043). CLAD-free survival was significantly longer in the azithromycin group (p = 0.024). No difference was present in proportion of obstructive versus restrictive CLAD between both groups. Graft loss was similar in both groups: 23/43 (53%) versus 16/40 (40%) patients (p = 0.27). Long-term pulmonary function and functional exercise capacity were significantly better in the azithromycin group (p < 0.05). Prophylactic azithromycin therapy reduces long-term CLAD prevalence and improves CLAD-free survival, pulmonary function, and functional exercise capacity after LTx.

Rapid porcine lung decellularization using a novel organ regenerative control acquisition bioreactor

To regenerate discarded lungs that would not normally be used for transplant, ex vivo reseeding after decellularization may produce organs suitable for clinical transplantation and therefore close the donor gap. Organ regenerative control acquisition (Harvard Biosciences, Holliston, MA), a novel bioreactor system that simulates physiological conditions, was used to evaluate a method of rapid decellularization. Although most current decellularization methods are 24-72 hours, we hypothesized that perfusing porcine lungs with detergents at higher pressures for less time would yield comparable bioscaffolds suitable for future experimentation. Methods involved perfusion of 1% Triton X-100 (Triton) and 0.1% sodium dodecyl sulfate at varied physiological flow rates. Architecture of native and decellularized lungs was analyzed with hematoxylin and eosin (H&E) staining, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Dry gas and liquid ventilation techniques were introduced. Our 7 hour decellularization procedure removes nuclear material while maintaining architecture. Bioscaffolds have the microarchitecture for reseeding of stem cells. Hematoxylin and eosin staining suggested removal of nuclear material, whereas SEM and TEM imaging demonstrated total removal of cells with structural architecture preserved. This process can lead to clinical implementation, thereby increasing the availability of human lungs for transplantation.

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.

A new classification system for chronic lung allograft dysfunction

Although survival after lung transplantation has improved significantly during the last decade, chronic rejection is thought to be the major cause of late mortality. The physiologic hallmark of chronic rejection has been a persistent fall in forced expiratory volume in 1 second associated with an obstructive ventilatory defect, for which the term bronchiolitis obliterans syndrome (BOS) was defined to allow a uniformity of description and grading of severity throughout the world. Although BOS was generally thought to be irreversible, recent evidence suggests that some patients with BOS may respond to azithromycin with > 10% improvement in their forced expiratory volume in 1 second. In addition, a restrictive form of chronic rejection has recently been described that does not fit the strict definition of BOS as an obstructive defect. Hence, the term chronic lung allograft dysfunction (CLAD) has been introduced to cover all forms of graft dysfunction, but CLAD has yet to be defined. We propose a definition of CLAD and a flow chart that may facilitate recognition of the different phenotypes of CLAD that can complicate the clinical course of lung transplant recipients.