Thoracic organ transplantation

Bridge to Transplantation: Policies Impact Practices

Since the development of the first heart allocation system in 1988 to the most recent heart allocation system in 2018, the road to heart transplantation has continued to evolve. Policies were shaped with advances in temporary and durable left ventricular assist devices as well as prioritization of patients based on degree of illness. Herein, we review the changes in the heart allocation system over the past several decades and the impact of practice patterns across the United States.

Machine learning in lung transplantation: Where are we?

Lung transplantation has been accepted as a viable treatment for end-stage respiratory failure. While regression models continue to be a standard approach for attempting to predict patients' outcomes after lung transplantation, more sophisticated supervised machine learning (ML) techniques are being developed and show encouraging results. Transplant clinicians could utilize ML as a decision-support tool in a variety of situations (e.g. waiting list mortality, donor selection, immunosuppression, rejection prediction). Although for some topics ML is at an advanced stage of research (i.e. imaging and pathology) there are certain topics in lung transplantation that needs to be aware of the benefits it could provide.

The new allocation era and policy

Since the Department of Health and Human Services (DHHS) issued the Final Rule in 1998 as a guideline for organ transplantation and allocation policies, the lung allocation system has undergone two major changes. The first change came with the implementation of the lung allocation score (LAS) instead of waiting time as the primary determinant for donor lung allocation. The LAS model helped allocate donor lungs based on medical urgency and likelihood of post-transplant success. The LAS has been successful in prioritizing the sickest candidates and reducing waitlist mortality in line with the Final Rule mandates. However, the LAS model did not address geographic variability in donor lung supply and demand, leading to disparities in waiting list survival based on a patient’s listing location, which was inconsistent with the Final Rule. In an urgent response to a lawsuit filed by a patient demanding broader geographic access to lungs in November 2017, the second major change in lung allocation occurred when the primary allocation unit for donor lungs expanded from the local donation service area (DSA) to a 250-nautical mile radius around the donor hospital. The Organ Procurement and Transplantation Network has since undergone a review of the current organ allocation systems and has approved a continuous organ distribution framework to guide the creation of a new organ allocation system without rigid geographic borders. In this review, we will describe the history of lung allocation, the changes to the allocation system and their consequences, and the potential future of lung allocation policy in the U.S.

Pediatric Living Lung Donor Transplant Candidates: Psychiatric Status of Utilized and Non-Utilized Donors

Living donor lung (lobar) transplantation has greatly decreased in the past decade due to the success of the lung allocation score (LAS) system, instituted in 2005 by the Organ Procurement and Transplantation Network (OPTN). Between 1993 and 2006, 460 living lung donor transplants were performed in the United States with 369 donations occurring at the University of Southern California and Washington University in St. Louis. These two centers accounted for over 80% of all living donor lung transplants between 1994 and 2006. All potential donors received a psychological/psychiatric evaluation as part of the donor selection process, which is standard practice in the United States, Europe, and Asia. Utilized and non-utilized lung donors were compared in terms of their psychiatric history and present status. Results indicated that 31% (N = 54) of the total sample had a lifetime prevalence of a psychiatric disorder, which is less than that the 46% lifetime rate for the general population (Kessler in Arch Gen Psychiatry 62:593-602, 2005). This study did find that psychiatric history or status was not exclusion factor for transplant surgery in either group. This observation about psychiatric issues in potential living lung donors should be useful to transplant centers who utilize adult live donors of any solid organ type for pediatric recipients and in Japan where live donor lung transplants still represent a significant proportion of lung transplants (Date in J Thorac Dis 8: S631-S636, 2016).

Donor surfactant protein A2 polymorphism and lung transplant survival

PURPOSE

Gene polymorphisms of surfactant proteins, key players in lung innate immunity, have been associated with various lung diseases. The aim of this study was to investigate the potential association between variations within the surfactant protein (SP)-A gene of the donor lung allograft and recipient post-transplant outcome.

METHODS

Lung-transplant patients (n=192) were prospectively followed-up with pulmonary function tests, bronchoscopies with bronchoalveolar lavage and biopsies. Donor lungs were assayed for SP-A1 (6Aⁿ) and SP-A2 (1Aⁿ) gene polymorphism using the pyrosequencing method. Unadjusted and adjusted stratified Cox survival models are reported.

RESULTS

SP-A1 and SP-A2 genotype frequency and lung transplant recipient and donor characteristics as well as cause of death are noted. Recipients were grouped per donor SP-A2 variants. Individuals that received lungs from donors with the SP-A2 1A⁰ (n=102) versus 1A¹ variant (n=68) or SP-A2 genotype 1A⁰1A⁰ (n=54) versus 1A⁰A¹ (n=38) had greater survival at 1 year (log-rank p<0.025). No significant association was noted for SP-A1 variants. Stratified adjusted survival models for 1-year survival and diagnosis showed a reduced survival for 1A¹ variant and the 1A⁰1A¹ genotype. Furthermore, when survival was conditional on 1-year survival no significance was observed, indicating that the survival difference was due to the first year's outcome associated with the 1A¹ variant.

CONCLUSION

Donor lung SP-A gene polymorphisms are associated with post-transplant clinical outcome. Lungs from donors with the SP-A2 variant 1A¹ had a reduced survival at 1 year. The observed donor genetic differences, via innate immunity relate to the post-transplant clinical outcome.

Systematic review of using medical informatics in lung transplantation studies

BACKGROUND

Lung transplantation is one of the advanced treatment options performed even in patients suffering from end-stage lung disease. Due to the positive results of medical informatics in other fields of medicine, lung transplant researchers have also conducted remarkable studies to improve transplant outcomes. The main objective of this article was to review the current studies of health information technology used in lung transplantation.

METHODS

A systematic search was performed in four scientific databases (Web of Science, Scopus, Science Direct, and PubMed) from January 2000 to December 2018. The criteria for inclusion were included in any study describing the use of health information technology or medical informatics in terms of lung transplantation, English papers, and original researchers. The retrieved articles were accordingly screened based on the inclusion and exclusion criteria to select relevant studies. The survey and synthesis of included articles were conducted based on predefined classification.

RESULTS

Out of 263 articles, 27 studies met our inclusion criteria. All included studies involved the application of health information technology in lung transplantation. The types of health information technology methods applied in reviewed articles included mhealth (11.1 %), DSS (7.4 %), decision aid tools (7.4 %), telemedicine (22.2 %), AI methods (11.1 %), data mining (37 %), and patient education (3.7 %). The majority of studies (88.9 %) showed the positive impact of health information technology to enhance lung transplantation outcomes. Finally, the main approaches in different phases of lung transplantation processes were interpreted and summarized in the visual model.

CONCLUSION

This systematic review provides new insights regarding the application of medical informatics in the lung transplantation domain. The missing areas of medical informatics in the lung transplantation domain were recognized through this study.

Lung Allocation Score Thresholds Prioritize Survival After Lung Transplantation

BACKGROUND

The lung allocation score (LAS) prioritizes lung transplant (LTx) candidates with poor transplant-free survival and expected survival benefit from LTx. Although patients with the highest LAS have the shortest waiting time, mortality benefit is unclear in this group, raising criticism that the LAS inappropriately prioritizes critically ill candidates. We aim to identify a threshold above which increasing LAS values do not predict increasing survival benefit.

METHODS

The United Network for Organ Sharing Registry was queried for first-time adult LTx candidates with LAS ≥ 30 between May 2005 and December 2016. Survival was tracked from the time of listing through the posttransplant period and compared with survival while remaining on the waitlist, using proportional hazards regression. The survival benefit of LTx was modeled as a piecewise-constant time-dependent covariate, moderated by candidate LAS.

RESULTS

Of the overall cohort (N = 21,157), LTx was particularly protective for 365 patients with an initial LAS of 70 to 79 (hazard ratio of death after undergoing LTx relative to remaining on the waitlist, 0.2; 95% CI, 0.1-0.3). However, the survival benefit of LTx did not meaningfully increase for 1,042 patients listed with even higher LAS. Among patients with cystic fibrosis, the survival benefit of LTx was constant above an LAS of approximately 50.

CONCLUSIONS

Consistent survival benefit of LTx was observed among patients with an initial LAS of 70 and greater. This result supports equalizing priority for donor lung allocation for patients with LAS ≥ 70. A lower LAS threshold for maximum priority is indicated in patients with cystic fibrosis.

Lung transplant candidates with idiopathic pulmonary fibrosis and long-term pirfenidone therapy: Treatment feasibility influences waitlist survival

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a chronically progressive lung disease with exceptionally poor prognosis. While lung transplantation (LTx) is considered the last-resort therapeutic option, dismal waitlist mortality still hampers the salvage of patients with IPF. Pirfenidone, originally designed for IPF treatment, has increasingly been utilized. This study aimed to evaluate whether Pirfenidone could influence outcomes of patients with IPF on the Japanese LTx waitlist.

METHODS

This retrospective single-center cohort study included 25 consecutive patients with IPF who were registered as LTx candidates at our institution between July 1999 and August 2016. Patients with a history of pretransplant Pirfenidone therapy (Pirfenidone group) were compared with those with no history (non-Pirfenidone group).

RESULTS

In total, 6 (24%) patients received Pirfenidone as pretransplant therapy for 45.2 (range, 18.6-66.8) months. During the treatment period, the Pirfenidone group achieved a significant reduction in the decline rate of the forced vital capacity (-6.2% vs. -0.3%, p = 0.04) and a lower lung allocation score (31 vs. 41, p = 0.013) compared with the non-Pirfenidone group. The Pirfenidone group exhibited 100% waitlist survival three years after registration that was comparable to other indications, and 66% of the patients were still alive at the time of organ availability. No patient in the Pirfenidone group developed Pirfenidone-related surgical complications postoperatively.

CONCLUSIONS

Patients with IPF successfully managed with long-term Pirfenidone therapy achieved favorable outcomes after LTx registration, comparable to other patients with LTx indications. The tolerability to antifibrotic therapy can be a predictor of waitlist survival.

Selection of Patients for Initial Clinical Trials of Solid Organ Xenotransplantation

Several groups have reported extended survival of genetically engineered pig organs in nonhuman primates, varying from almost 10 months for life-supporting kidney grafts and more than 2 years for non-life-supporting heart grafts to less than 1 month for life-supporting liver and lung grafts. We have attempted to define groups of patients who may not have an option to wait for an allograft. These include kidney, heart, and lung candidates who are highly-allosensitized. In addition, some kidney candidates (who have previously lost at least 2 allografts from rapid recurrence of native kidney disease) have a high risk of further recurrence and will not be offered a repeat allotransplant. Patients with complex congenital heart disease, who may have undergone previous palliative surgical procedures, may be unsuitable for ventricular assist device implantation. Patients dying of fulminant hepatic failure, for whom no alternative therapy is available, may be candidates for a pig liver, even if only as a bridge until an allograft becomes available. When the results of pig organ xenotransplantation in nonhuman primates suggest a realistic potential for success of a pilot clinical trial, highly selected patients should be offered participation.

Health Locus of Control Predicts Survival after Lung Transplant

The purpose of this study was to assess whether health locus of control beliefs measured pre-transplant predicted survival after lung transplant. Participants were 100 patients who completed the Multidimensional Health Locus of Control scale before and after transplant. Cox proportional hazards regressions were used to investigate the relationship between each of the three subscales (IHLC, PHLC, CHLC) and survival time after transplant. After adjusting for age and medical diagnosis, participants with medium and high levels of IHLC had lower hazard ratios than those with low IHLC. Neither PHLC nor CHLC exhibited statistical differences in survival. Compared to patients with low IHLC, patients with medium and high levels of IHLC lived longer after lung transplant.

Impact of the lung allocation score on survival beyond 1 year

Implementation of the lung allocation score (LAS) in 2005 led to transplantation of older and sicker patients without altering 1-year survival. However, long-term survival has not been assessed and emphasizing the 1-year survival metric may actually sustain 1-year survival while not reflecting worsening longer-term survival. Therefore, we assessed overall and conditional 1-year survival; and the effect of crossing the 1-year threshold on hazard of death in three temporal cohorts: historical (1995-2000), pre-LAS (2001-2005) and post-LAS (2005-2010). One-year survival post-LAS remained similar to pre-LAS (83.1% vs. 82.1%) and better than historical controls (75%). Overall survival in the pre- and post-LAS cohorts was also similar. However, long-term survival among patients surviving beyond 1 year was worse than pre-LAS and similar to historical controls. Also, the hazard of death increased significantly in months 13 (1.44, 95% CI 1.10-1.87) and 14 (1.43, 95% CI 1.09-1.87) post-LAS but not in the other cohorts. While implementation of the LAS has not reduced overall survival, decreased survival among patients surviving beyond 1 year in the post-LAS cohort and the increased mortality occurring immediately after 1 year suggest a potential negative long-term effect of the LAS and an unintended consequence of increased emphasis on the 1-year survival metric.

The CCR5 chemokine receptor mediates vasoconstriction and stimulates intimal hyperplasia in human vessels in vitro

AIMS

The chemokine receptor CCR5 and its inflammatory ligands have been linked to atherosclerosis, an accelerated form of which occurs in saphenous vein graft disease. We investigated the function of vascular smooth muscle CCR5 in human coronary artery and saphenous vein, vascular tissues susceptible to atherosclerosis, and vasospasm.

METHODS AND RESULTS

CCR5 ligands were vasoconstrictors in saphenous vein and coronary artery. In vein, constrictor responses to CCL4 were completely blocked by CCR5 antagonists, including maraviroc. CCR5 antagonists prevented the development of a neointima after 14 days in cultured saphenous vein. CCR5 and its ligands were expressed in normal and diseased coronary artery and saphenous vein and localized to medial and intimal smooth muscle, endothelial, and inflammatory cells. [(125)I]-CCL4 bound to venous smooth muscle with KD = 1.15 ± 0.26 nmol/L and density of 22 ± 9 fmol mg(-1) protein.

CONCLUSIONS

Our data support a potential role for CCR5 in vasoconstriction and neointimal formation in vitro and imply that CCR5 chemokines may contribute to vascular remodelling and augmented vascular tone in human coronary artery and vein graft disease. The repurposing of maraviroc for the treatment of cardiovascular disease warrants further investigation.

The diagnostic value of gastroesophageal reflux disease (GERD) symptoms and detection of pepsin and bile acids in bronchoalveolar lavage fluid and exhaled breath condensate for identifying lung transplantation patients with GERD-induced aspiration

BACKGROUND

Gastroesophageal reflux disease (GERD) is thought to lead to aspiration and bronchiolitis obliterans syndrome after lung transplantation. Unfortunately, the identification of patients with GERD who aspirate still lacks clear diagnostic indicators. The authors hypothesized that symptoms of GERD and detection of pepsin and bile acids in the bronchoalveolar lavage fluid (BAL) and exhaled breath condensate (EBC) are effective for identifying lung transplantation patients with GERD-induced aspiration.

METHODS

From November 2009 to November 2010, 85 lung transplantation patients undergoing surveillance bronchoscopy were prospectively enrolled. For these patients, self-reported symptoms of GERD were correlated with levels of pepsin and bile acids in BAL and EBC and with GERD status assessed by 24-h pH monitoring. The sensitivity and specificity of pepsin and bile acids in BAL and EBC also were compared with the presence of GERD in 24-h pH monitoring.

RESULTS

The typical symptoms of GERD (heartburn and regurgitation) had modest sensitivity and specificity for detecting GERD and aspiration. The atypical symptoms of GERD (aspiration and bronchitis) showed better identification of aspiration as measured by detection of pepsin and bile acids in BAL. The sensitivity and specificity of pepsin in BAL compared with GERD by 24-h pH monitoring were respectively 60 and 45 %, whereas the sensitivity and specificity of bile acids in BAL were 67 and 80 %.

CONCLUSIONS

These data indicate that the measurement of pepsin and bile acids in BAL can provide additional data for identifying lung transplantation patients at risk for GERD-induced aspiration compared with symptoms or 24-h pH monitoring alone. These results support a diagnostic role for detecting markers of aspiration in BAL, but this must be validated in larger studies.

Pilot study exploring lung allograft surfactant protein A (SP-A) expression in association with lung transplant outcome

Primary graft failure and chronic lung allograft dysfunction (CLAD) limit lung transplant long-term outcomes. Various lung diseases have been correlated with surfactant protein (SP) expression and polymorphisms. We sought to investigate the role of SP expression in lung allografts prior to implantation, in relation to posttransplant outcomes. The expression of SP-(A, B, C, D) mRNA was assayed in 42 allografts. Posttransplant assessments include pulmonary function tests, bronchoscopy, broncho-alveolar lavage fluid (BALF) and biopsies to determine allograft rejection. BALF was assayed for SP-A, SP-D in addition to cytokines IL-8, IL-12 and IL-2. The diagnosis of CLAD was evaluated 6 months after transplantation. Lung allografts with low SP-A mRNA expression prior to implantation reduced survival (Log-rank p < 0.0001). No association was noted for the other SPs. Allografts with low SP-A mRNA had greater IL-2 (p = 0.03) and IL-12 (p < 0.0001) in the BALF and a greater incidence of rejection episodes (p = 0.003). Levels of SP-A mRNA expression were associated with the SP-A2 polymorphisms (p = 0.015). Specifically, genotype 1A1A(0) was associated with lower SP-A mRNA expression (p < 0.05). Lung allografts with low levels of SP-A mRNA expression are associated with reduced survival. Lung allograft SP-A mRNA expression appears to be associated with SP-A gene polymorphisms.

Donor surfactant protein D (SP-D) polymorphisms are associated with lung transplant outcome

Chronic lung allograft dysfunction (CLAD) is the major factor limiting long-term success of lung transplantation. Polymorphisms of surfactant protein D (SP-D), an important molecule within lung innate immunity, have been associated with various lung diseases. We investigated the association between donor lung SP-D polymorphisms and posttransplant CLAD and survival in 191 lung transplant recipients consecutively transplanted. Recipients were prospectively followed with routine pulmonary function tests. Donor DNA was assayed by pyrosequencing for SP-D polymorphisms of two single-nucleotide variations altering amino acids in the mature protein N-terminal domain codon 11 (Met(11) Thr), and in codon 160 (Ala(160) Thr) of the C-terminal domain. CLAD was diagnosed in 88/191 patients, and 60/191 patients have died. Recipients of allografts that expressed the homozygous Met(11) Met variant of aa11 had significantly greater freedom from CLAD development and better survival compared to those with the homozygous Thr(11) Th variant of aa11. No significant association was noted for SP-D variants of aa160. Lung allografts with the SP-D polymorphic variant Thr(11) Th of aa11 are associated with development of CLAD and reduced survival. The observed genetic differences of the donor lung, potentially with their effects on innate immunity, may influence the clinical outcomes after lung transplantation.

Impact of low donor to recipient weight ratios on cardiac transplantation

BACKGROUND

International Society of Heart and Lung Transplantation guidelines for adult heart transplantation (HT) suggest a donor to recipient body weight ratio (WR) of greater than 0.8. For female to male transplants, a WR of greater than 0.9 is recommended.

METHODS

The United Network for Organ Sharing database was examined for adult HT from 1999 to 2011. Controls with a WR of 0.9 or greater (normal donor to recipient weight ratio) were compared with patients with a WR of 0.6 to 0.89 (WRL) and a WR of less than 0.59 (WRVL). The primary measured outcome was survival.

RESULTS

Of the 21,928 patients undergoing HT, 14,592 (66.6%) were performed with a normal donor to recipient weight ratio, 7212 (32.9%) were performed with WRL, and 124 (0.6%) were performed with WRVL. In male donor to male recipient, male donor to female recipient, and female donor to female recipient HT, the use of WRL did not influence median survival (P = .3621) and was not associated with increased mortality (P = .7273). In female donor to male recipient HT, WRL was associated with decreased median survival (435 days, P = .0241) and was associated with increased mortality (hazard ratio, 1.201; P = .0383).

CONCLUSIONS

HT can be safely performed using WRL donors between sex-matched and male to female transplants. However, in female to male transplants, WRL donors are associated with decreased survival. Although clinical circumstances will guide decision making, consensus criteria may be revisited to liberalize the pool of acceptable donors in an era of unprecedented donor shortage.

Lung and heart allocation in the United States

Lung and heart allocation in the United States has evolved over the past 20-30 years to better serve transplant candidates and improve organ utilization. The current lung allocation policy, based on the Lung Allocation Score, attempts to take into account risk of death on the waiting list and chance of survival posttransplant. This policy is flexible and can be adjusted to improve the predictive ability of the score. Similarly, in response to the changing clinical phenotype of heart transplant candidates, heart allocation policies have evolved to a multitiered algorithm that attempts to prioritize organs to the most infirm, a designation that fluctuates with trends in therapy. The Organ Procurement and Transplantation Network and its committees have been responsive, as demonstrated by recent modifications to pediatric heart allocation and mechanical circulatory support policies and by ongoing efforts to ensure that heart allocation policies are equitable and current. Here we examine the development of US lung and heart allocation policy, evaluate the application of the current policy on clinical practice and explore future directions for lung and heart allocation.

Lung transplant for interstitial lung disease: outcomes before and after implementation of the united network for organ sharing lung allocation scoring system

OBJECTIVES

This study was undertaken to evaluate whether the adoption of the united network for organ sharing lung allocation score (LAS) was associated with significant changes in lung transplantation (LTX) outcomes for patients with interstitial lung disease (ILD) who underwent LTX at the University of Wisconsin Hospital and Clinics.

METHODS

Outcomes for 107 consecutive patients with various forms of ILD who underwent LTX between January 1993 and March 2009 were examined. Patients transplanted following the implementation of the LAS system (LAS, n = 56) were compared with those transplanted prior to LAS implementation (pre-LAS, n = 51) for whom LAS scores were calculated.

RESULTS

Patients with idiopathic pulmonary fibrosis (IPF) comprised the majority of patients with ILD. Recipients transplanted after the implementation of the LAS were significantly older (pre-LAS: 50.4 vs. LAS: 56.7 years, P < 0.01), required more supplemental oxygen (3 vs. 5 l/min, P < 0.01) and displayed lower cardiac index values (3.1 vs. 2.6 l/m(2), P < 0.01). The estimated LAS was significantly increased from 38.3 (pre-LAS) to 43.3 (LAS), P < 0.01. However, waiting time decreased from 266 to 78 days (P < 0.01). The rate of bilateral vs. single LTX was lower (35 vs. 16%, P = 0.02) for the post-LAS group. Cold ischaemic time was shorter in the post-LAS group (434 vs. 299 min, P < 0.01), and the length of hospital stay decreased from 24 to 11 days (P < 0.01). Hospital mortality (11 vs. 7%, P = 0.51) and post-transplant survival did not differ between the groups.

CONCLUSIONS

Post-transplant outcomes for patients with ILD or the subset of recipients with IPF were not adversely affected by the implementation of the LAS.

Laparoscopic fundoplication with or without pyloroplasty in patients with gastroesophageal reflux disease after lung transplantation: how I do it

INTRODUCTION

Several studies have confirmed that gastroesophageal reflux disease (GERD) in lung transplant patients is a risk factor for the development and progression of bronchiolitis obliterans syndrome (BOS), a form of rejection after lung transplantation. Moreover, numerous reports indicate that surgical correction of GERD may control the decline in lung function characteristic of BOS. Although laparoscopic fundoplication is an accepted treatment option for these patients with GERD, the surgical technique, which often includes a laparoscopic pyloroplasty, has not been standardized.

METHODS

The purpose of this article is to describe a step-by-step approach to the laparoscopic treatment of GERD in lung transplant patients. We also address specific technical concerns encountered in the surgical management of this high-risk patient population; we provide data on the safety of this operation; and we illustrate the evidence-based rationale for each technical step of the procedure.

Development of a predictive model for long-term survival after lung transplantation and implications for the lung allocation score

BACKGROUND

Improving long-term survival after lung transplantation can be facilitated by identifying patient characteristics that are predictors of positive long-term outcomes. Validated survival modeling is important for guiding clinical decision-making, case-mix adjustment in comparative effectiveness research and refinement of the lung allocation system (LAS).

METHODS

We used the registry of the International Society for Heart and Lung Transplantation (ISHLT) to develop and validate a predictive model of 5-year survival after lung transplantation. A total of 18,072 eligible cases were randomly split into development and validation datasets. Pre-transplant recipient variables considered included age, gender, diagnosis, body mass index, serum creatinine, hemodynamic variables, pulmonary function variables, viral status and comorbidities. Predictors were considered in a stepwise approach with the Akaike Information Criteria (AIC). Time-dependent receiver operator characteristic (ROC) curves assessed predictive ability. A 1-year conditional model and three models for disease subgroups were considered. ROC methods were used to characterize the predictive potential of the LAS post-transplant model at 1 and 5 years.

RESULTS

The baseline model included age, diagnosis, creatinine, bilirubin, oxygen requirement, cardiac output, Epstein-Barr virus status, transfusion history and diabetes history. Prediction of long-term survival was poor (area under the curve [AUC] = 0.582). Neither the 1-year conditional model (AUC = 0.573) nor models designed for separate diseases (AUC = 0.553 to 0.591) improved survival prediction. The predictive ability of the LAS post-transplant parameters was similar to that of our model (1-year AUC = 0.580 and 5-year AUC = 0.566).

CONCLUSIONS

Models developed from pre-transplant characteristics poorly predict long-term survival. Models for separate diseases and 1-year conditional models did not improve prediction. Better databases and approaches to predict survival are needed to improve lung allocation.

Increasing lung allocation scores predict worsened survival among lung transplant recipients

Implemented in 2005, the lung allocation score (LAS) aims to distribute donor organs based on overall survival benefits for all potential recipients, rather than on waiting list time accrued. While prior work has shown that patients with scores greater than 46 are at increased risk of death, it is not known whether that risk is equivalent among such patients when stratified by LAS score and diagnosis. We retrospectively evaluated 5331 adult lung transplant recipients from May 2005 to February 2009 to determine the association of LAS (groups based on scores of < or =46, 47-59, 60-79 and > or =80) and posttransplant survival. When compared with patients with LAS < or = 46, only those with LAS > or = 60 had an increased risk of death (LAS 60-79: hazard ratio [HR], 1.52; 95% confidence interval [CI], 1.21-1.90; LAS > or = 80: HR, 2.03; CI, 1.61-2.55; p < 0.001) despite shorter median waiting list times. This risk persisted after adjusting for age, diagnosis, transplant center volume and donor characteristics. By specific diagnosis, an increased hazard was observed in patients with COPD with LAS > or = 80, as well as those with IPF with LAS > or = 60.

Preemptive CD20+ B cell depletion attenuates cardiac allograft vasculopathy in cyclosporine-treated monkeys

Chronic rejection currently limits the long-term efficacy of clinical transplantation. Although B cells have recently been shown to play a pivotal role in the induction of alloimmunity and are being targeted in other transplant contexts, the efficacy of preemptive B cell depletion to modulate alloimmunity or attenuate cardiac allograft vasculopathy (CAV) (classic chronic rejection lesions found in transplanted hearts) in a translational model has not previously been described. We report here that the CD20-specific antibody (alphaCD20) rituximab depleted CD20+ B cells in peripheral blood, secondary lymphoid organs, and the graft in cynomolgus monkey recipients of heterotopic cardiac allografts. Furthermore, CD20+ B cell depletion therapy combined with the calcineurin inhibitor cyclosporine A (CsA) prolonged median primary graft survival relative to treatment with alphaCD20 or CsA alone. In animals treated with both alphaCD20 and CsA that achieved efficient B cell depletion, alloantibody production was substantially inhibited and the CAV severity score was markedly reduced. We conclude therefore that efficient preemptive depletion of CD20+ B cells is effective in a preclinical model to modulate pathogenic alloimmunity and to attenuate chronic rejection when used in conjunction with a conventional clinical immunosuppressant. This study suggests that use of this treatment combination may improve the efficacy of transplantation in the clinic.

A review of the potential applications and controversies of non-invasive testing for biomarkers of aspiration in the lung transplant population

Despite improvements in one-yr survival following lung transplantation, five-yr survival lags significantly behind the transplantation of other solid organs. The contrast in survival persists despite advancements in anti-rejection regimens, suggesting a non-alloimmune mechanism to chronic lung transplant failure. Notably, markers of aspiration have been demonstrated in bronchoalveolar lavage (BAL) fluid concurrent with bronchiolitis obliterans syndrome (BOS). This recent evidence has underscored gastroesophageal reflux (GER) and its associated aspiration risk as a non-alloimmune mechanism of chronic lung transplant failure. Given the suggested safety and efficacy of laparoscopic anti-reflux procedures in the lung transplant population, identifying those at risk for aspiration is of prime importance, especially concerning the potential for long-term improvements in morbidity and mortality. Conventional diagnostic methods for GER and aspiration, such as pH monitoring and detecting pepsin and bile salts in BAL fluid, have gaps in their effectiveness. Therefore, we review the applications and controversies of a non-invasive method of defining reflux injury in the lung transplant population: the detection of biomarkers of aspiration in the exhaled breath condensate. Only by means of assay standardization and directed collaboration may such a non-invasive method be a realization in lung transplantation.

Predicting the graft survival for heart-lung transplantation patients: an integrated data mining methodology

BACKGROUND

Predicting the survival of heart-lung transplant patients has the potential to play a critical role in understanding and improving the matching procedure between the recipient and graft. Although voluminous data related to the transplantation procedures is being collected and stored, only a small subset of the predictive factors has been used in modeling heart-lung transplantation outcomes. The previous studies have mainly focused on applying statistical techniques to a small set of factors selected by the domain-experts in order to reveal the simple linear relationships between the factors and survival. The collection of methods known as 'data mining' offers significant advantages over conventional statistical techniques in dealing with the latter's limitations such as normality assumption of observations, independence of observations from each other, and linearity of the relationship between the observations and the output measure(s). There are statistical methods that overcome these limitations. Yet, they are computationally more expensive and do not provide fast and flexible solutions as do data mining techniques in large datasets.

PURPOSE

The main objective of this study is to improve the prediction of outcomes following combined heart-lung transplantation by proposing an integrated data-mining methodology.

METHODS

A large and feature-rich dataset (16,604 cases with 283 variables) is used to (1) develop machine learning based predictive models and (2) extract the most important predictive factors. Then, using three different variable selection methods, namely, (i) machine learning methods driven variables-using decision trees, neural networks, logistic regression, (ii) the literature review-based expert-defined variables, and (iii) common sense-based interaction variables, a consolidated set of factors is generated and used to develop Cox regression models for heart-lung graft survival.

RESULTS

The predictive models' performance in terms of 10-fold cross-validation accuracy rates for two multi-imputed datasets ranged from 79% to 86% for neural networks, from 78% to 86% for logistic regression, and from 71% to 79% for decision trees. The results indicate that the proposed integrated data mining methodology using Cox hazard models better predicted the graft survival with different variables than the conventional approaches commonly used in the literature. This result is validated by the comparison of the corresponding Gains charts for our proposed methodology and the literature review based Cox results, and by the comparison of Akaike information criteria (AIC) values received from each.

CONCLUSIONS

Data mining-based methodology proposed in this study reveals that there are undiscovered relationships (i.e. interactions of the existing variables) among the survival-related variables, which helps better predict the survival of the heart-lung transplants. It also brings a different set of variables into the scene to be evaluated by the domain-experts and be considered prior to the organ transplantation.

Lung volume reduction surgery and lung transplantation in chronic obstructive pulmonary disease

Medical treatment of emphysema does not alter the natural progression of the disease. Surgical techniques are an attractive conceptual approach to treat hyperinflation in these patients. Lung volume reduction surgery and lung transplantation are appropriate therapeutic options for a selected population with emphysema. We will review the available evidence to support these approaches.

The new lung allocation system and its impact on waitlist characteristics and post-transplant outcomes

Historically, waiting time was the primary determinant of lung organ allocation in the United States. Under this system, waiting time grew progressively longer as the annual number of transplants reached a plateau, and every year, a considerable number of candidates died while waiting. In 2005, the lung allocation system changed; under the new system, priority for transplantation is determined by medical urgency and expected outcome. The lung allocation score is based on survival models that estimate waitlist and post-transplant survival, and reflects the net transplant benefit. Early evaluations of the new system indicate that waiting time has decreased, the total number of transplants has increased, waitlist mortality may be decreasing, and survival after transplantation remains unchanged. Over time, refinements in the lung allocation score will likely reduce waitlist mortality further and maintain or perhaps improve survival after transplantation.

Tolerance in Heart Transplantation: The Holy Grail, or an Attainable Goal?

The father of cardiac transplantation, Norman Shumway, famously predicted that tolerance was the future of the field, and always would be. Although his prediction remains true to date, significant progress has been made toward this goal, the "Holy Grail" for transplant clinicians. Current efforts are fueled by disappointing long-term outcomes associated with chronic immunosuppression, and the promise that partial or complete tolerance will impact long-term results favorably. This article provides a clinical definition of tolerance primarily based on lessons learned from animal heart allograft models. It reviews several promising strategies for inducing tolerance and detecting its presence through the use of biomarkers in peripheral blood or the graft, and outlines a possible path toward making this vision a clinical reality.

Differential Pulmonary Vein Gases Predict Primary Graft Dysfunction

BACKGROUND

Donor arterial blood gas measurements correlate poorly with lung allograft function in the recipient. We assessed the utility of reduced pulmonary vein gas (PVG) partial pressure of oxygen (PO2) in predicting the incidence of primary graft dysfunction.

METHODS

While the donor was ventilated with 100% oxygen, superior and inferior pulmonary veins were directly aspirated bilaterally and pulmonary venous PO2 measured. A PO2 of less than 300 mm Hg was considered subnormal. These values were assessed for predictive value in terms of primary graft dysfunction in univariate and multivariate analysis.

RESULTS

In 112 of the 201 lung and heart-lung transplants performed during the period January 2000 to December 2004, full PVGs were available for analysis. The number of pulmonary veins with sub-normal PVG correlated significantly with the incidence of severe primary graft dysfunction posttransplant in univariate (p = 0.01) and multivariate analysis (hazard ratio 2.35, p = 0.016). When analyzed separately, this correlation remained significant for recipients of single or bilateral transplants alone. No correlation existed between arterial PO2 at donor referral and incidence of primary graft dysfunction. Median duration of ventilation, intensive care unit stay, and 30-day and 90-day mortality were not significantly different for those with any subnormal PVG compared with those with all values in the normal range.

CONCLUSIONS

Differential PVGs are a useful tool in the assessment of donor lung function before procurement. It is a helpful indicator of whether preischemic dysfunction is localized or diffuse, and can be used to predict the extent to which ischemia and reperfusion will exacerbate any existing abnormality.

Marginal Lung Donors: A Diminishing Margin of Safety?

Lung donor shortages have resulted in the critical appraisal of cadaveric donor acceptability criteria and the gradual relaxation of once strict guidelines. Many centers have reported their results with these "extended criteria" donors and an increasing number of multicenter registry studies have also been published. The results have been contradictory and leave many questions unanswered. Important new data has however come to light since the last review of the subject by the International Society for Heart and Lung Transplantation Pulmonary Council. We review the current literature focusing on recent developments in the pursuit of an expanded lung donor pool with acceptable outcomes.

Association of clinical risk factors with functional status following lung transplantation

A fundamental goal of lung transplantation is the regaining of functional capacity, yet little is known about what factors are associated with the achievement of this goal. The aim of this study is to test the association of clinical risk factors with functional status 1 year following lung transplantation. We conducted a cohort study of 321 lung transplants and assessed functionality by the distance achieved during a standard 6-min walk test (6MWT). Preoperative recipient risk factors were evaluated for association with functional status and adjusted for confounding using multivariable linear regression models. In these multivariable analyses, recipient female gender (p<0.001), recipient pretransplant body mass index (BMI) of greater than 27 kg/m2 (p=0.017) and shorter pretransplant 6MWT distances (p=0.006) were independently associated with shorter distances achieved during 6MWT after lung transplant, while cystic fibrosis (CF) (p=0.003), and bilateral lung transplant (p=0.014) were independently associated with longer distances achieved. Approximately 51% of the variance in 6MWT distance was explained by these risk factors in the linear regression models (R2=0.51). These findings may have implications in patient counseling, selection, procedure choice, and may lead to interventions aimed at improving the functional outcomes of lung transplantation.

Cardiac procedures in lung transplant recipients do not increase mortality in selected patients

BACKGROUND

Associated comorbidities in potential lung transplant recipients may significantly impact operative morbidity and mortality. We undertook this review to specifically study whether patients who underwent associated cardiac procedures either before (as a prerequisite) or during their lung transplantation had different outcomes when compared with the overall cohort of lung transplant recipients.

METHODS

A retrospective chart review was performed of all patients who underwent lung transplantation at the University of Texas Health Science Center at San Antonio from January 1994 to June 2004. The records of these patients were analyzed for patient-days on the ventilator, hospital length of stay, operative morbidity and mortality, and long-term survival. The patients were then divided into two groups and compared: patients who had a cardiac intervention either prerequisite to or concurrent with their transplant (group C, n = 13) and patients who did not (group NC [no cardiac intervention], n = 120).

RESULTS

Although the median length of stay was longer in group C when compared with group NC, the number of patient-days on the ventilator and the operative morbidity and mortality were similar for both groups. Likewise, overall long-term survival was not significantly different (Kaplan-Meier method, p = 0.70).

CONCLUSIONS

Patients who are otherwise deemed to be good candidates for lung transplantation but are found to have an associated cardiac condition that could adversely affect their candidacy may still be considered for transplantation in selected cases if the cardiac abnormality can be addressed either before or during transplantation.

The effect of reflux and bile acid aspiration on the lung allograft and its surfactant and innate immunity molecules SP-A and SP-D

Gastro-esophageal reflux and related pulmonary bile acid aspiration were prospectively investigated as possible contributors to postlung transplant bronchiolitis obliterans syndrome (BOS). We also studied the impact of aspiration on pulmonary surfactant collectin proteins SP-A and SP-D and on surfactant phospholipids--all important components of innate immunity in the lung. Proximal and distal esophageal 24-h pH testing and broncho-alveolar lavage fluid (BALF) bile acid assays were performed prospectively at 3-month posttransplant in 50 patients. BALF was also assayed for SP-A, SP-D and phospholipids expressed as ratio to total lipids: phosphatidylcholine; dipalmitoylphosphatidylcholine; phosphatidylglycerol (PG); phosphatidylinositol; sphingomyelin (SM) and lysophosphatidylcholine. Actuarial freedom from BOS was assessed. Freedom from BOS was reduced in patients with abnormal (proximal and/or distal) esophageal pH findings or BALF bile acids (Log-rank Mantel-Cox p < 0.05). Abnormal pH findings were observed in 72% (8 of 11) of patients with bile acids detected within the BALF. BALF with high levels of bile acids also had significantly lower SP-A, SP-D, dipalmitoylphosphatidylcholine; PG and higher SM levels (Mann-Whitney, p < 0.05). Duodeno-gastro-esophageal reflux and consequent aspiration is a risk factor for the development of BOS postlung transplant. Bile acid aspiration is associated with impaired lung allograft innate immunity manifest by reduced surfactant collectins and altered phospholipids.

Lung Transplantation: Current Status and Challenges

The lung is an anatomically complex vital organ whose normal physiology depends on actively regulated ventilation and perfusion, and maintenance of a delicate blood-air barrier over a huge surface area in direct contact with a potentially hostile environment. Despite significant progress over the past 25 years, both short- and long-term outcomes remain significantly inferior for lung recipients relative to other "solid" organs. This review summarizes the current status of lung transplantation so as to frame the principle challenges currently facing end-stage lung-failure patients and the practitioners who care for them.

An Overview of Solid Organ Transplantation

Once a medical curiosity, solid organ transplantation is now a commonplace occurrence, with more than 27,000 procedures performed in the United States in 2004 alone. This article offers an overview of the various solid organ transplant procedures to provide a context within which subsequent articles on pulmonary complications can be viewed.

Thoracic organ transplantation in the United States, 1994-2003

Using OPTN/SRTR data, this article reviews the state of thoracic organ transplantation in 2003 and the previous decade. Time spent on the heart waiting list has increased significantly over the last decade. The percentage of patients awaiting heart transplantation for >2 years increased from 23% in 1994 to 49% by 2003. However, there has been a general decline in heart waiting list death rates over the decade. In 2003, the lung transplant waiting list reached a record high of 3,836 registrants, up slightly from 2002 and more than threefold since 1994. One-year patient survival for those receiving lungs in 2002 was 82%, a statistically significant improvement from 2001 (78%). The number of patients awaiting a heart-lung transplant, declining since 1998, reached 189 in 2003. Adjusted patient survival for heart-lung recipients is consistently worse than the corresponding rate for isolated lung recipients, primarily due to worse outcomes for heart-lung recipients with congenital heart disease. A new lung allocation system, approved in June 2004, derives from the survival benefit of transplantation with consideration of urgency based on waiting list survival, instead of being based solely on waiting time. A goal of the policy is to minimize deaths on the waiting list.

Long-term Pulmonary Function After Living-donor Lobar Lung Transplantation in Adults

BACKGROUND

Living-donor lobar lung transplantation was developed as an alternative to cadaveric transplantation. However, whether two pulmonary lobes provide comparable intermediate and long-term pulmonary function to full-sized bilateral cadaveric grafts in adults is unknown.

METHODS

An analysis of the pulmonary functions of 59 bilateral lobar and 43 bilateral cadaveric adult lung transplant recipients who survived more than 3 months after transplantation was performed.

RESULTS

Mean follow-up was 3.8 +/- 2.8 years. In lobar recipients, mean percent predicted forced vital capacity and forced expiratory volume in 1 second improved between 1 and 6 months after transplantation (42.5% +/- 13.4% and 46.9% +/- 14.0% at 1 month versus 63.6% +/- 14.1% and 64.5% +/- 13.7% at 6 months; p < 0.001 and <0.001, respectively). In cadaveric recipients, mean percent predicted forced vital capacity improved after transplantation (54.3% +/- 14.5% at 1 month versus 74.2% +/- 21.3% at 12 months; p < 0.01). As compared with the cadaveric group, mean percent predicted forced vital capacity and forced expiratory volume in 1 second were lower 1 and 3 months after transplantation in the lobar recipients (p = 0.001 at both times); however, by 6 months after transplantation, these values were comparable and remained so throughout the follow-up period. In a subset of lobar and cadaveric recipients, maximal exercise, heart rate, peak oxygen consumption, anaerobic oxygen consumption threshold, and ability to maintain oxygen saturation were also comparable.

CONCLUSIONS

In those adult recipients surviving more than 3 months after transplantation, lobar lung transplantation provides comparable intermediate and long-term pulmonary function and exercise capacity to bilateral cadaveric lung transplantation.