Pediatric transplantation, 1994-2003

Ethical considerations in pediatric solid organ transplantation

Solid organ transplantation is now an accepted therapeutic modality for children and teenagers suffering from a wide variety of complex medical conditions. Unfortunately, patients continue to die while on the organ waiting list as there remains an imbalance between the number of recipients listed for transplantation and the number of donors available. The organ allocation process continues to generate ethical questions and debates. In this publication, we discuss some of the most frequently reported ethical matters in the field of pediatric solid organ transplantation.

Cardiac Overexpression of XIN Prevents Dilated Cardiomyopathy Caused by TNNT2 ΔK210 Mutation

TNNT2 mutation is associated with a range of cardiac diseases, including dilated cardiomyopathy (DCM). However, the mechanisms underlying the development of DCM and heart failure remain incompletely understood. In the present study, we found the expression of cardiac XIN protein was reduced in TNNT2-ΔK210 hESCs-derived cardiomyocytes and mouse heart tissues. We further investigated whether XIN protects against TNNT2 mutation-induced DCM. Overexpression of the repeat-containing isoform XINB decreased the percentage of myofilaments disorganization and increased cell contractility of TNNT2-ΔK210 cardiomyocytes. Moreover, overexpression of XINB by heart-specific delivery via AAV9 ameliorates DCM remodeling caused by TNNT2-ΔK210 mutation in mice, revealed by partially reversed cardiac dilation, systolic dysfunction and heart fibrosis. These results suggest that deficiency of XIN may play a critical role in the development of DCM. Consequently, our findings may provide a new mechanistic insight and represent a therapeutic target for the treatment of idiopathic DCM.

Ten-year appraisal of pediatric renal allograft biopsies: Points to ponder

There is paucity of literature on pediatric renal allograft biopsy (RAB) evaluation. We present RAB findings of pediatric renal transplantation (RT) and correlate with outcome. This is a 10-year retrospective study of diagnostic RAB of children <12 years divided in to three groups: Group 1 (n = 9): less than haplo-match living donor RT (LDRT), Group 2 (n = 32): greater than or equal to haplo-match LDRT, and Group 3 (n = 7): deceased donor RT. Demographics, biopsy findings, survival, and serum creatinine (SCr) were evaluated. Statistical analysis was performed using IBM SPSS Statistics version 20.0. The most common findings were antibody-mediated rejection (ABMR) observed in 77.7%, 45%, and 71.5% and T-cell-mediated rejections (TCMRs) in 33.3%, 52.5%, and 42.9% in Groups 1, 2, and 3, respectively. Recurrent oxalosis was seen in 5% in Group 2. Death-censored graft survival was 100% at 1 year and 43.8% from 5 to 9 years in Group 1; 93.5%, 76.6%, 56.5%, and 14.4% at 1, 5, 10, and 15 years in Group 2; 100% at one year; and 71.4% from 5 to 12 years in Group 3. No patient appeared after 9 years in Group 1 and after 12 years in Group 3. In Group 1, the mean SCr (mg/dL) was 1.06 ± 0.45, 2.12 ± 1.87, and 1.39 at 1, 5, and 9 years; 1.35 ± 0.97, 1.73 ± 1.15, and 2.49 ± 1.64 in Group 2; and 1.15 ± 1.24, 1.43 ± 0.1, and 1.18 ± 0.06, respectively, in Group 3 at 1, 5, and 10 years posttransplant. ABMR followed by TCMR was the most common injury in all the groups. Group 1 had more rejections than others.

Cytomegalovirus Experience in Pediatric Kidney Transplantation in 26 Years' Time

INTRODUCTION

In this study,we investigated the presence of cytomegalovirus (CMV) infection in kidney transplanted children and its effect on kidney dysfunction.

MATERIAL AND METHODS

One hundred thirty-five pediatric renal transplant patients were included in this study. The presence of CMV infection, CMV risk status, and other clinical features of the patients were evaluated retrospectively.

RESULTS

Fifty-three percent of all patients and 68.8% of patients with CMV were male. The mean age was 12 years in all patients and CMV groups. According to the CMV risk classification, 40.9% of the patients with CMV infection/disease were in the high-risk group (CMV D+R-). In CMV risk groups, the presence of CMV infection/disease was similar. Cold ischemia time, male sex (patients and donors), deceased donor, higher HLA-mismatches, and cumulative antithymocyte globulin dose were found as risk factors for CMV infection/disease. Acute rejection/graft failure was observed in 27% of all patients. CMV infection has no effect on rejection/graft failure and survival.

DISCUSSION

The frequency and risk factors of CMV in renal transplant children in our study were consistent with the literature.

CONCLUSIONS

CMV infection was found in one-fifth of our patients and the majority (71.9%) of them developed infection in the first 6 months. In one-third of our patients acute rejection/graft failure was observed. There was no effect of CMV infection on rejection/graft failure and survival in pediatric patients with proper and effective treatment.

Access to Transplantation for Undocumented Pediatric Patients

Clinicians in the United States today regularly face dilemmas about health disparities. Many patients and families cannot afford the medical care that doctors recommend. These problems are most stark when the medical care that is needed is lifesaving and expensive and involves scarce resources. Transplants are the best example of this. The most ethically disturbing situations occur when an undocumented immigrant child needs a transplant. We present such a case and analyze the ethical, legal, and policy issues that arise.

Facilitating the transition of young people with long-term conditions through health services from childhood to adulthood: the Transition research programme

Background

As young people with long-term conditions move from childhood to adulthood, their health may deteriorate and their social participation may reduce. ‘Transition’ is the ‘process’ that addresses the medical, psychosocial and educational needs of young people during this time. ‘Transfer’ is the ‘event’ when medical care moves from children’s to adults’ services. In a typical NHS Trust serving a population of 270,000, approximately 100 young people with long-term conditions requiring secondary care reach the age of 16 years each year. As transition extends over about 7 years, the number in transition at any time is approximately 700.

Objectives

Purpose – to promote the health and well-being of young people with long-term conditions by generating evidence to enable NHS commissioners and providers to facilitate successful health-care transition. Objectives – (1) to work with young people to determine what is important in their transitional health care, (2) to identify the effective and efficient features of transitional health care and (3) to determine how transitional health care should be commissioned and provided.

Design, settings and participants

Three work packages addressed each objective. Objective 1. (i) A young people’s advisory group met monthly throughout the programme. (ii) It explored the usefulness of patient-held health information. (iii) A ‘Q-sort’ study examined how young people approached transitional health care. Objective 2. (i) We followed, for 3 years, 374 young people with type 1 diabetes mellitus (150 from five sites in England), autism spectrum disorder (118 from four sites in England) or cerebral palsy (106 from 18 sites in England and Northern Ireland). We assessed whether or not nine proposed beneficial features (PBFs) of transitional health care predicted better outcomes. (ii) We interviewed a subset of 13 young people about their transition. (iii) We undertook a discrete choice experiment and examined the efficiency of illustrative models of transition. Objective 3. (i) We interviewed staff and observed meetings in three trusts to identify the facilitators of and barriers to introducing developmentally appropriate health care (DAH). We developed a toolkit to assist the introduction of DAH. (ii) We undertook a literature review, interviews and site visits to identify the facilitators of and barriers to commissioning transitional health care. (iii) We synthesised learning on ‘what’ and ‘how’ to commission, drawing on meetings with commissioners.

Main outcome measures

Participation in life situations, mental well-being, satisfaction with services and condition-specific outcomes.

Strengths

This was a longitudinal study with a large sample; the conditions chosen were representative; non-participation and attrition appeared unlikely to introduce bias; the research on commissioning was novel; and a young person’s group was involved.

Limitations

There is uncertainty about whether or not the regions and trusts in the longitudinal study were representative; however, we recruited from 27 trusts widely spread over England and Northern Ireland, which varied greatly in the number and variety of the PBFs they offered. The quality of delivery of each PBF was not assessed. Owing to the nature of the data, only exploratory rather than strict economic modelling was undertaken.

Results and conclusions

(1) Commissioners and providers regarded transition as the responsibility of children’s services. This is inappropriate, given that transition extends to approximately the age of 24 years. Our findings indicate an important role for commissioners of adults’ services to commission transitional health care, in addition to commissioners of children’s services with whom responsibility for transitional health care currently lies. (2) DAH is a crucial aspect of transitional health care. Our findings indicate the importance of health services being commissioned to ensure that providers deliver DAH across all health-care services, and that this will be facilitated by commitment from senior provider and commissioner leaders. (3) Good practice led by enthusiasts rarely generalised to other specialties or to adults’ services. This indicates the importance of NHS Trusts adopting a trust-wide approach to implementation of transitional health care. (4) Adults’ and children’s services were often not joined up. This indicates the importance of adults’ clinicians, children’s clinicians and general practitioners planning transition procedures together. (5) Young people adopted one of four broad interaction styles during transition: ‘laid back’, ‘anxious’, ‘wanting autonomy’ or ‘socially oriented’. Identifying a young person’s style would help personalise communication with them. (6) Three PBFs of transitional health care were significantly associated with better outcomes: ‘parental involvement, suiting parent and young person’, ‘promotion of a young person’s confidence in managing their health’ and ‘meeting the adult team before transfer’. (7) Maximal service uptake would be achieved by services encouraging appropriate parental involvement with young people to make decisions about their care. A service involving ‘appropriate parental involvement’ and ‘promotion of confidence in managing one’s health’ may offer good value for money.

Future work

How might the programme’s findings be implemented by commissioners and health-care providers? What are the most effective ways for primary health care to assist transition and support young people after transfer?

Study registration

This study is registered as UKCRN 12201, UKCRN 12980, UKCRN 12731 and UKCRN 15160.

Funding

The National Institute for Health Research Programme Grants for Applied Research programme.

Pediatric Renal Transplantation: Evaluation of Long-Term Outcomes and Comparison to Adult Population

BACKGROUND

In Europe, pediatric transplantation accounts for only about 4% of all kidney transplantations performed. The aim of our work is to evaluate the evolution of pediatric renal transplantation in our department over time, but also to compare this special population with the adult one.

METHODS

We evaluated all pediatric renal transplantations performed in our department between January 1981 and December 2016. We performed the analysis of clinical, analytical, and surgical factors to look for predictive factors of graft loss or decrease of survival. In addition, we performed a comparative study of pediatric and adult populations and an evaluation of the evolution of pediatric renal transplantation in our department over time.

RESULTS

We evaluated 101 renal transplantations performed in patients younger than 18 years. Pediatric transplantations corresponded to 3.4% of all renal transplantations performed in our department. The rate of living donors was 12%. Donors of grafts for the pediatric population were significantly younger than in the adult population. The increase in donor age was associated with lower renal graft survival rates. Acute rejections were more frequent in the pediatric population. Eleven pediatric recipients (10.9%) died in the follow-up period. Renal graft survival in the pediatric population was 94.8%, 77.4%, and 66.5% at 1, 5, and 10 years, respectively. There was no significant difference in graft survival in the pediatric and adult population. The pediatric overall survival rate at 1, 5 and 10 years was 97.9%, 96.8%, and 91.9%, respectively.

CONCLUSION

Pediatric renal transplantation presents results identical to those identified in adults.

Improved Survival While Waiting and Risk Factors for Death in Pediatric Patients Listed for Cardiac Transplantation

Our aim is to determine (a) the effect of changes in pre-transplant management and era of listing on survival of children listed for HTx and (b) risk factors for death while waiting. This retrospective study included all children listed between 1/1993 and 12/2009 at our center. Survival was determined using survival analysis and competing outcomes modeling. There were 254 listed patients of whom 144 (57%) had congenital heart disease, 208 (82%) were status 1, 52 used ECMO (20%), and 28 used ventricular assist device support (VAD) (11%) beginning in 2005. Overall mortality while waiting was 17% at 6 months, and 69% underwent transplant. Seven of 95 patients (7%) died waiting after 2004 compared to 36 of 159 (23%) before. ECMO and earlier year of listing were significant risk factors (p < 0.001) for wait-list mortality, whereas mortality was significantly lower (p = 0.002) after availability of VADs. Race, gender, blood type, and congenital diagnosis were not significant risk factors for death. Survival in pediatric patients listed for HTx has improved significantly in the current era at our institution. The availability of pediatric VADs has had a significant impact on survival while waiting in children listed for transplantation.

Is it Ethical to Prioritize Patients for Organ Allocation According to Their Values about Organ Donation?

Because the supply of deceased donor organs fails to meet demand, patients needing a transplant frequently have lengthy waits or die while waiting. In an effort to reduce waiting times, the concept of “preferred status” has emerged. In the United States, preferred status has taken the form of a community of individuals called LifeSharers. Using directed donation, this group aims to facilitate priority organ allocation to its members—people who have agreed to be organ donors. Such preferred status programs increase societal awareness about organ donation and transplantation, but they are not without ethical controversy, as some term them “clubs.” In the case of LifeSharers, the potential to increase the pool of deceased donor organs is a worthy goal that would benefit the community of patients awaiting transplantation, not just LifeSharers members.

Usability testing of the Internet program: "Teens Taking Charge: Managing My Transplant Online"

Adolescents with SOT demonstrate high rates of medication non-adherence and higher rates of graft loss compared to all other age groups. Self-management interventions encompass information-based material designed to achieve disease-related learning and changes in the participant's knowledge and skill acquisition, while providing social support. These interventions have had some success in chronic disease populations by reducing symptoms and promoting self-efficacy and empowerment. Using findings from a needs assessment, an Internet-based self-management program, Teens Taking Charge: Managing My Transplant Online, for youth with SOT was developed. This program contains information on transplant, self-management and transition skills, and opportunities for peer support. The purpose of this study was to determine the usability and acceptability of the initial three modules (Medication and Vaccines; Diet after Transplant; and Living with a Transplant Organ) of the online program from the perspectives of youth with SOT. Participants were recruited from SOT clinics at a large pediatric tertiary care center in Canada. Three iterative cycles (seven patients per iteration) of usability testing took place to refine the Web site prototype. Study procedures involved participants finding items from a standardized list of features and talking aloud about issues they encountered, followed by a semi-structured interview to generate feedback about what they liked and disliked about the program. All 21 patients (mean age = 14.9 yr) found the Web site content to be trustworthy, they liked the picture content, and they found the videos of peer experiences to be particularly helpful. Participants had some difficulties finding information within submodules and suggested a more simplistic design with easier navigation. This web-based intervention is appealing to teenagers and may foster improved self-management with their SOT. Nine additional teen and two parent modules are being developed, and the completed Web site will undergo usability testing. In the future, a randomized control trial will determine the feasibility and effectiveness of this online self-management program on adherence, self-efficacy, and transition skills.

Loss of pediatric kidney grafts during the "high-risk age window": insights from pediatric liver and simultaneous liver-kidney recipients

Pediatric kidney transplant recipients experience a high-risk age window of increased graft loss during late adolescence and early adulthood that has been attributed primarily to sociobehavioral mechanisms such as nonadherence. An examination of how this age window affects recipients of other organs may inform the extent to which sociobehavioral mechanisms are to blame or whether kidney-specific biologic mechanisms may also exist. Graft loss risk across current recipient age was compared between pediatric kidney (n = 17,446), liver (n = 12,161) and simultaneous liver-kidney (n = 224) transplants using piecewise-constant hazard rate models. Kidney graft loss during late adolescence and early adulthood (ages 17-24 years) was significantly greater than during ages <17 (aHR = 1.79, 95%CI = 1.69-1.90, p < 0.001) and ages >24 (aHR = 1.11, 95%CI = 1.03-1.20, p = 0.005). In contrast, liver graft loss during ages 17-24 was no different than during ages <17 (aHR = 1.03, 95%CI = 0.92-1.16, p = 0.6) or ages >24 (aHR = 1.18, 95%CI = 0.98-1.42, p = 0.1). In simultaneous liver-kidney recipients, a trend towards increased kidney compared to liver graft loss was observed during ages 17-24 years. Late adolescence and early adulthood are less detrimental to pediatric liver grafts compared to kidney grafts, suggesting that sociobehavioral mechanisms alone may be insufficient to create the high-risk age window and that additional biologic mechanisms may also be required.

National trends over 25 years in pediatric kidney transplant outcomes

OBJECTIVE

To investigate changes in pediatric kidney transplant outcomes over time and potential variations in these changes between the early and late posttransplant periods and across subgroups based on recipient, donor, and transplant characteristics.

METHODS

Using multiple logistic regression and multivariable Cox models, graft and patient outcomes were analyzed in 17,446 pediatric kidney-only transplants performed in the United States between 1987 and 2012.

RESULTS

Ten-year patient and graft survival rates were 90.5% and 60.2%, respectively, after transplantation in 2001, compared with 77.6% and 46.8% after transplantation in 1987. Primary nonfunction and delayed graft function occurred in 3.3% and 5.3%, respectively, of transplants performed in 2011, compared with 15.4% and 19.7% of those performed in 1987. Adjusted for recipient, donor, and transplant characteristics, these improvements corresponded to a 5% decreased hazard of graft loss, 5% decreased hazard of death, 10% decreased odds of primary nonfunction, and 5% decreased odds of delayed graft function with each more recent year of transplantation. Graft survival improvements were lower in adolescent and female recipients, those receiving pretransplant dialysis, and those with focal segmental glomerulosclerosis. Patient survival improvements were higher in those with elevated peak panel reactive antibody. Both patient and graft survival improvements were most pronounced in the first posttransplant year.

CONCLUSIONS

Outcomes after pediatric kidney transplantation have improved dramatically over time for all recipient subgroups, especially for highly sensitized recipients. Most improvement in graft and patient survival has come in the first year after transplantation, highlighting the need for continued progress in long-term outcomes.

Mortality after pediatric kidney transplantation in England--a population-based cohort study

The aim of this study was to explore mortality after pediatric kidney transplantation in England over the last decade. We used data from HES to select all kidney transplant procedures performed in England between April 2001 and March 2012. Data linkage analysis was performed with the ONS to identify all deaths occurring among this study cohort. Data for 1189 pediatric recipients were compared to 17 914 adult recipients (number of deaths, 33 vs. 2052, respectively, p < 0.001), with median follow-up 4.4 yr (interquartile range 2.2-7.3 yr). There was no difference in mortality within the pediatric cohort; age 0-1 (n = 25, patient survival 100.0%), age 2-5 (n = 198, patient survival 96.0%), age 6-12 (n = 359, patient survival 97.5%), and age 13-18 (n = 607, patient survival 97.4%), respectively (p = 0.567). The most common causes of death were renal (n = 8, 24.2%), infection (n = 6, 18.2%), and malignancy (n = 5, 15.2%). All deaths from malignancy were secondary to PTLD. In a fully adjusted Cox regression model, only white ethnicity was significantly associated with risk of pediatric mortality post-kidney transplantation (hazard ratio 2.7, 95% confidence interval [1.0-7.3], p = 0.047). To conclude, this population-based cohort study confirms low mortality after pediatric kidney transplantation with short follow-up.

Induced pluripotent stem cell-derived cardiomyocytes for cardiovascular disease modeling and drug screening

Human induced pluripotent stem cells (hiPSCs) have emerged as a novel tool for drug discovery and therapy in cardiovascular medicine. hiPSCs are functionally similar to human embryonic stem cells (hESCs) and can be derived autologously without the ethical challenges associated with hESCs. Given the limited regenerative capacity of the human heart following myocardial injury, cardiomyocytes derived from hiPSCs (hiPSC-CMs) have garnered significant attention from basic and translational scientists as a promising cell source for replacement therapy. However, ongoing issues such as cell immaturity, scale of production, inter-line variability, and cell purity will need to be resolved before human clinical trials can begin. Meanwhile, the use of hiPSCs to explore cellular mechanisms of cardiovascular diseases in vitro has proven to be extremely valuable. For example, hiPSC-CMs have been shown to recapitulate disease phenotypes from patients with monogenic cardiovascular disorders. Furthermore, patient-derived hiPSC-CMs are now providing new insights regarding drug efficacy and toxicity. This review will highlight recent advances in utilizing hiPSC-CMs for cardiac disease modeling in vitro and as a platform for drug validation. The advantages and disadvantages of using hiPSC-CMs for drug screening purposes will be explored as well.

Modeling heart disease in a dish: from somatic cells to disease-relevant cardiomyocytes

A scientific milestone that has tremendously impacted the cardiac research field has been the discovery and establishment of human-induced pluripotent stem cells (hiPSC). Key to this discovery has been uncovering a viable path in generating human patient and disease-specific cardiac cells to dynamically model and study human cardiac diseases in an in vitro setting. Recent studies have demonstrated that hiPSC-derived cardiomyocytes can be used to model and recapitulate various known disease features in hearts of patient donors harboring genetic-based cardiac diseases. Experimental drugs have also been tested in this setting and shown to alleviate disease phenotypes in hiPSC-derived cardiomyocytes, further paving the way for therapeutic interventions for cardiac disease. Here, we review state-of-the-art methods to generate high-quality hiPSC and differentiate them towards cardiomyocytes as well as the full range of genetic-based cardiac diseases, which have been modeled using hiPSC. We also provide future perspectives on exploiting the potential of hiPSC to compliment existing studies and gain new insights into the mechanisms underlying cardiac disease.

Development and validation of a new statistical model for prognosis of long-term graft function after pediatric kidney transplantation

BACKGROUND

No adequate statistical model has been established to estimate future glomerular filtration rate (GFR) in children after kidney transplantation (KTX). Equations based on simple linear regression analysis as used in adults are not established in children.

METHODS

An optimal prognostic model of GFR was generated for 63 children at 3-7 years after KTX. The main regression model for prediction of the log-transformed GFR (logGFR) included the mean monthly change of GFR in the period 3-24 months after KTX (∆GFR), the baseline GFR at 3 months (bGFR), and an intercept. Additionally, we investigated if the inclusion of cofactors leads to more precise predictions. The model was validated by leave-one-out cross-validation for years 3-7 after KTX. Prognostic quality was determined with the mean squared error (MSE) and mean absolute error (MAE). Results were compared with the simple linear regression model used in adults.

RESULTS

The following statistical model was calculated for every prognosis year (i = 3, …, 7):[Formula: see text] [Formula: see text] Comparison of the new statistical model and the simple linear model for adults led to relevantly lower MSEs and MAEs for the new model (year 7: New model: MSE 0.1, MAE 0.3/adult model: MSE 1069, MAE 18). The benefit of inclusion of cofactors was not relevant.

CONCLUSIONS

This statistical model is able to predict long-term graft function in children with very high precision.

Age at graft loss after pediatric kidney transplantation: exploring the high-risk age window

BACKGROUND AND OBJECTIVE

The risk of graft loss after pediatric kidney transplantation increases during late adolescence and early adulthood, but the extent to which this phenomenon affects all recipients is unknown. This study explored interactions between recipient factors and this high-risk age window, searching for a recipient phenotype that may be less susceptible during this detrimental age interval.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

With use of Scientific Registry of Transplant Recipients data from 1987 to 2010, risk of graft loss across recipient age was quantified using a multivariable piecewise-constant hazard rate model with time-varying coefficients for recipient risk factors.

RESULTS

Among 16,266 recipients, graft loss during ages ≥17 and <24 years was greater than that for both 3-17 years (adjusted hazard ratio [aHR], 1.61; P<0.001) and ≥24 years (aHR, 1.28; P<0.001). This finding was consistent across age at transplantation, sex, race, cause of renal disease, insurance type, pretransplant dialysis history, previous transplant, peak panel-reactive antibody (PRA), and type of induction immunosuppression. The high-risk window was seen in both living-donor and deceased-donor transplant recipients, at all levels of HLA mismatch, regardless of centers' pediatric transplant volume, and consistently over time. The relationship between graft loss risk and donor type, PRA, transplant history, insurance type, and cause of renal disease was diminished upon entry into the high-risk window.

CONCLUSIONS

No recipient subgroups are exempt from the dramatic increase in graft loss during late adolescence and early adulthood, a high-risk window that modifies the relationship between typical recipient risk factors and graft loss.

Non-viral infections in children after renal transplantation

Renal transplantation has long been recognised as the gold standard treatment for children with end-stage renal failure. There has been an improvement over the years in patient and renal allograft survival because of improved immunosuppression, surgical techniques and living kidney donation. Despite reduced acute allograft rejection rates, non-viral infections continue to be a serious complication for paediatric renal transplant recipients (RTR). The risk of infections in RTR is determined by the pre-transplantation immunisation status, post-transplant exposure to potential pathogens and the amount of immunosuppression. The greatest risk of life-threatening and Cytomegalovirus infections is during the first 6 months post-transplant owing to a high immunosuppressive burden. The potential sources of bacterial infections are donor derived, transplant medium fluid, peritoneal and haemodialysis catheter and transplant ureteric stent. Urinary tract infections are frequent in patients with lower urinary tract dysfunction and can result in renal allograft damage. This review outlines the incidence, timing, risk factors, prevention and treatment of non-viral infections in paediatric RTR by critically reviewing current immunosuppressive regimens, their risk-benefit ratio in order to optimise renal allograft survival with reduced rates of rejection and infectious complications.

Patient-specific induced pluripotent stem cells as a model for familial dilated cardiomyopathy

Characterized by ventricular dilatation, systolic dysfunction, and progressive heart failure, dilated cardiomyopathy (DCM) is the most common form of cardiomyopathy in patients. DCM is the most common diagnosis leading to heart transplantation and places a significant burden on healthcare worldwide. The advent of induced pluripotent stem cells (iPSCs) offers an exceptional opportunity for creating disease-specific cellular models, investigating underlying mechanisms, and optimizing therapy. Here, we generated cardiomyocytes from iPSCs derived from patients in a DCM family carrying a point mutation (R173W) in the gene encoding sarcomeric protein cardiac troponin T. Compared to control healthy individuals in the same family cohort, cardiomyocytes derived from iPSCs from DCM patients exhibited altered regulation of calcium ion (Ca(2+)), decreased contractility, and abnormal distribution of sarcomeric α-actinin. When stimulated with a β-adrenergic agonist, DCM iPSC-derived cardiomyocytes showed characteristics of cellular stress such as reduced beating rates, compromised contraction, and a greater number of cells with abnormal sarcomeric α-actinin distribution. Treatment with β-adrenergic blockers or overexpression of sarcoplasmic reticulum Ca(2+) adenosine triphosphatase (Serca2a) improved the function of iPSC-derived cardiomyocytes from DCM patients. Thus, iPSC-derived cardiomyocytes from DCM patients recapitulate to some extent the morphological and functional phenotypes of DCM and may serve as a useful platform for exploring disease mechanisms and for drug screening.

Primer on renal transplantation

Renal transplantation transforms chronically ill children with end stage renal disease (ESRD) into near normal resulting in improvement in nutrition, growth, neurodevelopment and quality of life, and is the goal of therapy. However, the benefits of transplantation come at a price of life-long treatment with immunosuppressive medications, increased risk of infections and malignancy. Children younger than 10 y of age have the best, and adolescents have the worst 5-y graft survival likely due to non-adherence with medications in the adolescents. Long-term complications include ongoing issues related to chronic kidney disease (CKD) and cardiovascular morbidity and mortality contributing to graft loss and shortened life expectancy, thus limiting the success of organ transplantation. Therefore, appropriate management of CKD and cardiovascular issues should be integral to the care of pediatric transplant patients. The other ongoing challenges include organ shortage, prevention and treatment of late acute rejections and chronic graft dysfunction, discovering reliable noninvasive immune monitoring tools, improving adherence, psychosocial rehabilitation, and the elusive goal of tolerance.

The challenges and opportunities for transitional care research

The provision of healthcare for young people with solid organ transplants as they move into adult-centered services has received increasing attention over recent years particularly as non-adherence and graft loss increase after transfer. Despite medical advances and that transitional care is now well established on national and international health agendas, progress in the research arena has unfortunately been slow. The aims of this paper are to consider why this is and discuss the particular challenges facing clinical researchers working within the area.

[Concept to improve adherence in adolescents following renal transplantation: vision or reality?]

Transition to adult care is a generic issue for subspecialties dealing with chronic illness and has received little attention to date. The transition from pediatric to adult care for renal transplant recipients is recognized as a high-risk period for poor graft outcome associated with more than 20% graft loss. Non-adherence to immunosuppressive medications is one of the most important factors contributing to graft loss during this period. Transition is, therefore, a concern of both pediatric and adult providers, and medical improvements in this area will require more effective collaboration at this interface. This report explores medical and psychological risk factors and barriers during the transition process. In addition, a specially developed coaching concept for young adults is presented intended to assist adolescents with early childhood end-stage renal disease in the transition from pediatric to adult care.

Mitogenic cardiomyopathy: a lethal neonatal familial dilated cardiomyopathy characterized by myocyte hyperplasia and proliferation

Pediatric cardiomyopathies are a heterogenous group of conditions of which dilated cardiomyopathies are the most common clinicomorphologic subtype. However, the etiology and pathogenesis of many cases of dilated cardiomyopathies remain unknown. We describe a series of 5 cases of a rare but clinically and histologically distinctive dilated cardiomyopathy that was uniformly lethal in early infancy. The 5 cases include 2 pairs of siblings. There was parental consanguinity in 1 of the 2 pairs of siblings. Death occurred in early infancy (range, 22-67 days; mean, 42 days) after a short history of general lethargy, decreased feeding, respiratory distress, or cyanosis. There was no specific birth or early neonatal problems. Autopsy revealed congestive cardiac failure and enlarged, dilated hearts with ventricular dilatation more pronounced than atrial dilatation, and endocardial fibroelastosis. Histology showed prominent hypertrophic nuclear changes of cardiac myofibers and markedly increased myocyte mitotic activity including occasional atypical mitoses. Immunohistochemical staining for Mib1 showed a markedly increased proliferative index of 10% to 20%. Ancillary investigations, including molecular studies, did not reveal a primary cause for the cardiomyopathies. This distinctive dilated cardiomyopathy characterized by unusual histologic features of myocyte nuclear hypertrophy and marked mitotic activity is lethal in early infancy. Its occurrence in 2 pairs of siblings suggests familial inheritance. Although the underlying molecular pathogenesis remains to be elucidated, it is important to recognize this distinctive entity for purposes of genetic counseling.

Outcomes in children with intestinal failure following listing for intestinal transplant

PURPOSE

The purpose of this study was to describe the population of pediatric patients waiting for intestinal transplant and to evaluate the risk of death or transplant by specific disease states.

METHODS

We studied the United Network for Organ Sharing (UNOS) database (Jan 1,1991 to 5/16/08) for patients 21 years old or younger at first listing for intestinal transplant and examined their age, sex, weight, and diagnoses. Time to list removal was summarized with cumulative incidence curves. Multinomial logistic regression was used to compare relative risk ratios for removal from the list for transplant, death, or other reasons.

RESULTS

We identified 1712 children listed for intestinal transplant (57% male, 51% <1 year, weight 8.1 kg [IQR, 6.1-14.1] at listing). Median age and weight at transplant (n = 852) were 1 year (IQR, 1-5) and 10 kg (IQR, 6.5-16.3). Regression analysis demonstrated significant differences in outcomes among disease conditions (P < .001). Compared to the gastroschisis group, the relative risk ratio for death versus transplant was higher in the necrotizing enterocolitis group (P = .015), lower in the short gut syndrome group (P = .001), and not different in the volvulus group (P = .94) after adjustment for weight and sex.

CONCLUSIONS

We conclude that the relative risk of transplant vs death varies significantly by the disease condition of the patient.

Increasing incidence of new-onset diabetes after transplant among pediatric renal transplant patients

BACKGROUND

Risk of new-onset diabetes after transplant (NODAT) is well characterized for adults but much less understood in pediatric transplant. This study examines the incidence and risk factors of NODAT in pediatric renal transplant patients.

METHODS

The incidence of NODAT over the first 3 years after transplant was examined with the United States Renal Data System data for primary renal transplant recipients (ages 0-21 years, transplanted between 1995 and 2004) with Medicare primary. Patients had no evidence of diabetes before transplant. We estimated the cumulative incidence rate and used Cox proportional hazards regression to identify the risk factors for NODAT. Propensity scores were calculated for immunosuppression choice to adjust for potential confounding factors.

RESULTS

Two thousand one hundred sixty-eight recipients with valid immunosuppression records and without pretransplant evidence of diabetes were included. Unadjusted, cumulative NODAT incidence at 3 years posttransplant was 7.1%. Significant factors for increased risk of NODAT included cytomegalovirus D+/R- serostatus (adjusted hazard ratio [aHR]=1.60), age 13 to 18 years (aHR=2.18), age 19 to 21 years (aHR=2.60), body mass index more than or equal to 30 kg/m (aHR=2.17), and use of tacrolimus (aHR=1.51). We failed to find any significant relationships between NODAT and graft failure or death.

CONCLUSIONS

Although the incidence of NODAT among patients aged 0 to 21 years is lower than that for adult patients, it is higher than suggested by earlier research and may represent an increase over time. The lack of association between NODAT and graft or failure death has important implications for posttransplant care. A clearer understanding of risk factors can help guide posttransplant monitoring and clinical decision making.

ANKRD1, the gene encoding cardiac ankyrin repeat protein, is a novel dilated cardiomyopathy gene

OBJECTIVES

We evaluated ankyrin repeat domain 1 (ANKRD1), the gene encoding cardiac ankyrin repeat protein (CARP), as a novel candidate gene for dilated cardiomyopathy (DCM) through mutation analysis of a cohort of familial or idiopathic DCM patients, based on the hypothesis that inherited dysfunction of mechanical stretch-based signaling is present in a subset of DCM patients.

BACKGROUND

CARP, a transcription coinhibitor, is a member of the titin-N2A mechanosensory complex and translocates to the nucleus in response to stretch. It is up-regulated in cardiac failure and hypertrophy and represses expression of sarcomeric proteins. Its overexpression results in contractile dysfunction.

METHODS

In all, 208 DCM patients were screened for mutations/variants in the coding region of ANKRD1 using polymerase chain reaction, denaturing high-performance liquid chromatography, and direct deoxyribonucleic acid sequencing. In vitro functional analyses of the mutation were performed using yeast 2-hybrid assays and investigating the effect on stretch-mediated gene expression in myoblastoid cell lines using quantitative real-time reverse transcription-polymerase chain reaction.

RESULTS

Three missense heterozygous ANKRD1 mutations (P105S, V107L, and M184I) were identified in 4 DCM patients. The M184I mutation results in loss of CARP binding with Talin 1 and FHL2, and the P105S mutation in loss of Talin 1 binding. Intracellular localization of mutant CARP proteins is not altered. The mutations result in differential stretch-induced gene expression compared with wild-type CARP.

CONCLUSIONS

ANKRD1 is a novel DCM gene, with mutations present in 1.9% of DCM patients. The ANKRD1 mutations may cause DCM as a result of disruption of the normal cardiac stretch-based signaling.

Long-term outcome after renal transplantation in childhood

The purpose of this article is to review: 1. Factors influencing long-term outcome data after transplantation 2. Patient survival overall, the effect of recipient age and donor type, causes of death, comparison of mortality after transplantation with that on dialysis, and effect of pre-emptive transplantation and race 3. Transplant survival overall, and the effect of recipient and donor age, donor type, pre-emptive transplantation, recurrent diseases, human leukocyte antigen (HLA) matching, immunosuppression, concordance, hypertension, bladder dynamics and type of donor nephrectomy 4. Final height and obesity 5. Psycho-social outcome.

Gated myocardial perfusion scintigraphy in children with myocarditis: can it be considered as an indicator of clinical outcome?

PURPOSE

Myocarditis is an inflammation of the heart muscle and represents a challenge for diagnosis and treatment. On account of the lack of sensitivity and specificity of routine cardiac tests, there is a need for accurate diagnostic imaging. The aim of this study is to review the role of gated 99Tc-methoxyisobutylisonitrile myocardial perfusion scintigraphy (G-MPS) in the diagnosis and follow-up of the patients with myocarditis in comparison with gallium scintigraphy.

MATERIALS AND METHODS

Thirteen patients with a clinical diagnosis of myocarditis were included in the study. All underwent rest G-MPS and the images were then evaluated by quantitative perfusion single-photon emission computed tomography and quantitative gated single photon emission computed tomography software program. Visual evaluation of perfusion was performed as well as analysis of motion with thickening function [expressed as summed rest score, summed motion score, and summed thickening score (STS)] with calculation of ejection fraction (EF) and lung-to-heart (L/H) ratio. Eight patients underwent 67Ga scintigraphy. Clinical, echocardiography, and cardiac enzymes (creatinine kinase-MB, myoglobulin, troponin T, brain natriuretic peptide) data were gathered from the patients' charts. Clinical outcome was grouped according to prognosis. Spearman's correlation (SC) test was used for comparison analysis.

RESULTS

Myocardial perfusion defects were observed in eight patients. Perfusion defects in the left ventricle involve a mean of 7.25% (range: 1-11%), whereas wall motion abnormality on G-MPS was more prominent, which showed to be a better marker for myocardial inflammation and necrosis. The 67Ga scintigraphy findings were normal in all, but two. The G-MPS EF (33+/-21%) was slightly lower than the echocardiography EF (40+/-15%), but with close correlation (SC coefficient: 0.635). Comparison of scintigraphic findings with clinical parameters showed that summed motion score with G-MPS EF and STS with L/H ratios were highly correlated (0.932 and 0.622, respectively). The maximum brain natriuretic peptide and L/H ratio with STS were highly correlated with the patients' outcomes (SC coefficient: -0.621, 0.821, and 0.579, respectively), as well.

CONCLUSION

Tc-methoxyisobutylisonitrile G-MPS is therefore helpful in providing additional diagnostic and prognostic information in patients with myocarditis.

Survival advantage of pediatric recipients of a first kidney transplant among children awaiting kidney transplantation

The mortality rate in children with ESRD is substantially lower than the rate experienced by adults. However, the risk of death while awaiting kidney transplantation and the impact of transplantation on long-term survival has not been well characterized in the pediatric population. We performed a longitudinal study of 5961 patients under age 19 who were placed on the kidney transplant waiting list in the United States. Of these, 5270 received their first kidney transplant between 1990 and 2003. Survival was assessed via a time-varying nonproportional hazards model adjusted for potential confounders. Transplanted children had a lower mortality rate (13.1 deaths/1000 patient-years) compared to patients on the waiting list (17.6 deaths/1000 patient-years). Within the first 6 months of transplant, there was no significant excess in mortality compared to patients remaining on the waiting list (adjusted Relative Risk (aRR) = 1.01; p = 0.93). After 6 months, the risk of death was significantly lower: at 6-12 months (aRR = 0.37; p < 0.001) and at 30 months (aRR 0.26; p < 0.001). Compared to children who remain on the kidney transplant waiting list, those who receive a transplant have a long-term survival advantage. With the potential for unmeasured bias in this observational data, the results of the analysis should be interpreted conservatively.

Should pediatric patients wait for HLA-DR-matched renal transplants?

Graft survival rates from deceased donors aged 35 years or less among all primary pediatric kidney transplant recipients in the United States between 1996 and 2004 were retrospectively examined to determine the effect of HLA-DR mismatches on graft survival. Zero HLA-DR-mismatched kidneys had statistically comparable 5-year graft survival (71%), to 1-DR-mismatched kidneys (69%) and 2-DR-mismatched kidneys (71%). When compared to donors less than 35 years of age, the relative rate of allograft failure was 1.32 (p = 0.0326) for donor age greater than or equal to age 35. There was no statistical increase in the odds of developing a panel-reactive antibody (PRA) greater than 30% at the time of second waitlisting, based upon the degree of HLA-A, -B or -DR mismatch of the first transplant, nor was there a 'dose effect' when more HLA antigens were mismatched between the donor and recipient. Therefore, pediatric transplant programs should utilize the recently implemented Organ Procurement and Transplantation Network's (OPTN)allocation policy, which prioritizes pediatric recipients to receive kidneys from deceased donors less than 35 years of age, and should not turn down such kidney offers to wait for a better HLA-DR-matched kidney.

A national conference to determine research priorities in pediatric solid organ transplantation

The need for evidence-based practice guidelines requires high quality, carefully controlled clinical research trials. This multidisciplinary conference attempted to: identify urgent clinical and research issues, identify obstacles to performing clinical trials, develop concepts for organ-specific and all-organ research and generate a report that would serve as a blueprint for future research initiatives. A few themes became evident. First, young children present a unique immunologic environment which may lead to tolerance, therefore, including young children in immunosuppression withdrawal and tolerance trials may increase the potential benefits of these studies. Second, adolescence poses significant barriers to successful transplantation. Non-adherence may be insufficient to explain poorer outcomes. More studies focused on identification and prevention of non-adherence, and the potential effects of puberty are required. Third, the relatively naive immune system of the child presents a unique opportunity to study primary infections and alloimmune responses. Finally, relatively small numbers of transplants performed in pediatric centers mandate multicenter collaboration. Investment in registries, tissue and DNA repositories will enhance productivity. The past decade has proven that outcomes after pediatric transplantation can be comparable to adults. The pediatric community now has the opportunity to design and complete studies that enhance outcomes for all transplant recipients.

Waiting before birth: outcomes after fetal listing for heart transplantation

Following fetal diagnosis of a profound heart defect, transplantation (HTx) is an alternative to pregnancy termination or neonatal surgical palliation. Retrospective review of the cardiac and transplant databases of fetal listings for HTx between 1990 and July 2006 was undertaken to describe outcomes after listing. We identified 26 fetal listings (of 269 total listings). Diagnoses included congenital heart disease (n = 24) and cardiomyopathy (n = 2). Seven patients were delisted after birth: in five cases parents opted for surgical palliation, two clinically improved. One patient died wait-listed (stillborn). Time wait-listed as a fetus ranged from 1-41 days (median 19 days). Eighteen patients underwent HTx (median weight 2.8 kg, range 2.1-10.9 kg); median days wait-listed after birth was 22 (4 h-123 days). Two fetuses were surgically delivered at 36 weeks gestation when a donor organ became available; 11 were transplanted as neonates (<30 days). The median age at HTx was 1 month (4 h-2.6 months). Fetal listing for HTx increases the potential window of opportunity for a donor organ to become available; patients had low wait-list mortality and a fair intermediate-term outcome. Well-defined criteria for eligibility for fetal listing and priority allocation to infants over fetuses seem rational approaches for centers that offer fetal listing.

Acquired Nonneoplastic Neonatal and Pediatric Diseases

The lung biopsy is an established procedure to procure a pathologic diagnosis in a child with a suspected pneumonic process of undetermined etiology. Improvements in pediatric anesthesia and surgery have reduced the operative complications to a minimum. A biopsy can usually be taken through a small intercostal incision when localization is not especially important in a patient with diffuse changes (see Chapter 1). The alternative method for tissue sampling is the endoscopic transbronchial biopsy. There is less risk to the patient, but the specimen is smaller and crush artifacts from the instrument are more common.

Pediatric transplantation in the United States, 1996-2005

Solid organ transplantation is accepted as a standard lifesaving therapy for end-stage organ failure in children. This article reviews trends in pediatric transplantation from 1996 to 2005 using OPTN data analyzed by the Scientific Registry of Transplant Recipients. Over this period, children have contributed significantly to the donor pool, and although the number of pediatric donors has fallen from 1062 to 900, this still accounts for 12% of all deceased donors. In 2005, 2% of 89,884 candidates listed for transplantation were less than 18 years old; in 2005, 1955 children, or 7% of 28,105 recipients, received a transplant. Improvement in waiting list mortality is documented for most organs, but pretransplant mortality, especially among the youngest children, remains a concern. Posttransplant survival for both patients and allografts similarly has shown improvement throughout the period; in most cases, survival is as good as or better than that seen in adults. Examination of immunosuppressive practices shows an increasing tendency across organs toward tacrolimus-based regimens. In addition, use of induction immunotherapy in the form of anti-lymphocyte antibody preparations, especially the interleukin-2 receptor antagonists, has increased steadily. Despite documented advances in care and outcomes for children undergoing transplantation, several considerations remain that require attention as we attempt to optimize transplant management.

Pediatric staff perspectives on organ donation after cardiac death in children

OBJECTIVES

The aims of this project were to describe whether pediatric clinical staff members believe that a donation after cardiac death (DCD) program could be consistent with the mission and core values of a children's hospital and to identify what staff consider essential to the acceptability of such a program.

DESIGN

Qualitative study.

SETTING

Children's hospital.

SUBJECTS

Pediatric clinical staff.

INTERVENTIONS

Data were gathered from pediatric clinical staff during eight focus groups conducted in a children's hospital in March and April 2005.

MEASUREMENTS AND MAIN RESULTS

Eighty-eight staff members participated. Six major themes emerged from qualitative analysis of the data: a) identifying children who could be candidates for DCD; b) considering the best interests of the dying child; c) approaching parents about DCD; d) preparing parents for their child's DCD; e) doing DCD well; and f) maintaining program integrity. Themes were used to construct a conceptual framework describing a model pediatric DCD program. Pediatric staff voiced numerous concerns. However, they identified "making it happen for families" who voice a desire to participate in organ donation as the primary reason for program adoption.

CONCLUSIONS

This study provides a framework for understanding pediatric staff perspectives on DCD programs in children. Results suggest several possible elements that may be helpful in framing interdisciplinary dialogue and informing institutional practices in the design of a pediatric DCD program.

Health insurance considerations for adolescent transplant recipients as they transition to adulthood

The advent of improved immunosuppression and enhanced allograft outcomes has resulted in a growing number of patients taking expensive immunosuppression medications for the rest of their lives. Healthcare costs for the majority of transplantation procedures in the USA currently are covered by Medicare, but coverage ends for outpatient immunosuppression medications 36-44 months after transplantation. Two or three immunosuppressive agents typically are included in post-transplant regimens with a total annual cost that can exceed 13,000 dollars. This represents a significant financial burden for families no matter if they have adequate health insurance coverage because of co-payment obligations. Evidence suggests that some patients have reduced immunosuppression doses because of an inability to afford their medication, increasing the risk of graft failure. The purpose of this article was to review these and other issues pertaining to medical insurance coverage and transplantation, particularly for adolescent recipients as they transition to adulthood.

Outcomes of Pediatric Patients Bridged to Heart Transplantation from Extracorporeal Membrane Oxygenation Support

Extracorporeal membrane oxygenation (ECMO) is used as a salvage therapy in children with irreversible myocardial failure who may be candidates for heart transplantation (HTx) (at the Hospital for Sick Children). We retrospectively assessed outcomes of children wait-listed for HTx from ECMO, and risk factors for patients (pts) bridged to HTx from January 1990 through December 2005. Of 205 patients supported with cardiac ECMO, 46 were wait-listed for HTx. Sixteen patients died before HTx: eight died while wait-listed on ECMO; eight were delisted (clinical deterioration; all died); five were delisted (improved), and 25 (54%) underwent HTx from ECMO. Of 25 patients who underwent HTx (median age 7.0 years [10 days to 17 years]), 13 had myocarditis or cardiomyopathy, and 12 had congenital heart disease. Median ECMO duration was 6.7 days (3-18 days). Median follow-up was 4.3 years (0.2-10.6 years). Four patients died <1 week post-HTx, and 21 survived until hospital discharge (84%). Post-transplant survival was 67% and 52% at 1 and 5 years, respectively. Risk factors for early death were older age, higher body surface area, higher creatinine before and during ECMO, fungal infections, and exposure to blood products. In summary, few risk factors preclude HTx candidacy from ECMO. The impact of newer assist technology on ECMO, wait-list mortality, and HTx outcomes remains to be elucidated.

Inherited surfactant protein-B deficiency and surfactant protein-C associated disease: clinical features and evaluation

The pulmonary surfactant is a mixture of phospholipids and proteins synthesized, packaged, and secreted by alveolar type II cells that lowers surface tension and prevents atelectasis at end-expiration. A tightly regulated, complex metabolic cycle involves all components of the pulmonary surfactant. Disorders of surfactant metabolism that have a genetic basis are rare, but causes of respiratory dysfunction in infants and children emerge. Recessive loss of function mutations in surfactant protein-B (SP-B) gene lead to respiratory failure that is lethal in the newborn period while single allelic mutations in the surfactant protein-C (SP-C) gene cause interstitial lung disease of varying severity and age of onset. The genetic basis, mechanisms, clinical presentation and outcome, diagnostic approach and limited therapeutic options for disease due to mutations the SP-B and SP-C genes will be described in detail in this article. These disorders provide insights into some of the distinct mechanisms that disrupt the surfactant metabolic cycle and cause respiratory disease in infants and children.

Pediatric living donor lobar lung transplantation

Living donor lobar lung transplantation (LDLLT) was developed in order to mitigate the growing competition for deceased donor (DD) lungs and resultant increase in waiting list mortality. Because each of the two donor lobes serves as an entire lung for the recipient, donors who are taller than the recipient are preferred. Therefore LDLLT is particularly well suited for pediatric recipients for whom adults serve as donors. Although long-term outcomes after LDLLT reported by the Organ Procurement and Transplantation Network (OPTN) are worse compared with DD recipients, overall pediatric outcomes as well as single center reports from the most experienced programs are more promising. Particularly encouraging are the findings that bronchiolitis obliterans (OB) is less frequent or less severe in LDLLT recipients in comparison to DD recipients. Moreover, outcomes may be improved by careful selection of donors to ensure adequately sized donor lobes and minimization of infectious risks. Although no donor deaths have been reported, there is a moderate risk of significant short-term complications. Long-term follow-up has not been reported. The use of LDLLT has decreased in recent years, and the recent change by the OPTN to an urgency/benefit allocation system for DD lungs in patients 12 yr and older may further reduce the demand. Nonetheless, we anticipate that LDLLT will continue to be utilized in select circumstances, particularly in children under 12 where access to DD organs remains challenging.