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Résumé Objectifs La pandémie de COVID-19 a influé sur la santé mentale de la population. Les familles des enfants qui ont des vulnérabilités en matière de santé ont été démesurément touchées par les politiques liées à la pandémie et les perturbations aux services, car elles s’appuient beaucoup sur le système de soins de santé et de services sociaux. Les chercheurs ont établi les répercussions de la pandémie de COVID-19 sur les enfants ayant des vulnérabilités en matière de santé physique et des incapacités, les familles et les professionnels de la santé. Méthodologie Des enfants ayant diverses vulnérabilités en matière de santé (transplantation cardiaque, affections respiratoires, anémie falciforme, trouble du spectre de l’autisme, troubles de santé mentale et approche de la fin de vie en raison d’une série de causes sous-jacentes), leurs parents et leurs professionnels de la santé ont participé à des entrevues semi-structurées. Les chercheurs ont utilisé des méthodes d’analyse qualitative et en ont extrait les thèmes liés aux effets et les recommandations en vue d’améliorer la pratique. Résultats Au total, 262 participants (30 enfants, 76 parents, 156 professionnels de la santé) ont été interviewés. Les enfants ont décrit leur solitude et leur isolement, les parents, leur épuisement, et les professionnels de la santé, la pression ressentie et un sentiment de détresse morale. Les thèmes reflétaient les effets de la pandémie sur la santé mentale des enfants, des familles et des professionnels de la santé, de même que les ressources insuffisantes pour soutenir la santé mentale, les influences organisationnelles et politiques qui ont façonné la prestation des services et les recommandations pour améliorer la prestation de ces services. Conclusion Les restrictions sanitaires imposées par la pandémie et les modifications aux soins ont eu de profondes répercussions sur la santé mentale des enfants qui ont des vulnérabilités en matière de santé, les familles et les professionnels de la santé. Les recommandations incluent la rédaction et l’adoption d’information ciblée sur la pandémie et la mise en œuvre de services de soutien en santé mentale. Ces résultats amplifient la nécessité de renforcer les capacités, y compris des stratégies proactives et la planification de mesures d’atténuation du risque dans l’éventualité d’une future pandémie.

Identification of differences in medication adherence by sex or organ type may help in planning interventions to optimize outcomes. We compared immunosuppressive medication adherence between males and females, and between kidney, liver and heart transplant recipients.This multicenter study of prevalent kidney, liver and heart transplant recipients 14-25 years assessed adherence 3 times (0, 3, 6 months post-enrollment) with the BAASIS self-report tool. At each visit, participants were classified as adherent if they missed no doses in the prior 4 weeks and non-adherent otherwise. Adherence was also assessed using the coefficient of variation (CV) of tacrolimus trough levels; CV 30% was classified as adherent. We used multivariable mixed effects logistic regression models adjusted for potential confounders to compare adherence by sex and by organ.Across all visits, males (n = 150, median age 20.4 years, IQR 17.2-23.3) had lower odds of self-reported adherence than females (n = 120, median age 19.8 years, IQR 17.1-22.7) (OR 0.41, 95% CI 0.21-0.80) but higher odds of adherence by tacrolimus CV (OR 2.50, 95% CI 1.30-4.82). No significant differences in adherence (by self-report or tacrolimus CV) were noted between the 184 kidney, 58 liver, and 28 heart recipients.Females show better self-reported adherence than males but greater variability in tacrolimus levels. Social desirability bias, more common in females than males, may contribute to better self-reported adherence among females. Higher tacrolimus variability among females may reflect biologic differences in tacrolimus metabolism between males and females rather than sex differences in adherence. There were no significant differences in adherence by organ type.

This document is designed to outline the definition, pathogenesis, diagnostic modalities and therapeutic measures to treat antibody-mediated rejection in children postheart transplant METHODS: Literature review was conducted by a Pediatric Heart Transplant Society (PHTS) working group to identify existing pediatric and adult studies on antibody-mediated rejection (AMR). In addition, the centers participating in PHTS were asked to submit their approach to diagnosis and management of pediatric AMR. This document synthesizes information gathered from both these sources to highlight a practical approach to diagnosing and managing a child with AMR postheart transplant. This document may not represent the practice at all centers in the PHTS and serves as a starting point to understand an approach to this clinical scenario.

Teenagers experience high rates of rejection and organ failure after heart transplantation due to non-adherence to medications, poor transition into adult care, and difficulties communicating with adults including healthcare providers. This project aimed to creatively bridge this gap-including teenage patients, their parents, and healthcare providers in the development of a new resource meant to motivate teenage heart-transplant-patients to take interest and ownership of their long-term health.Four teenage heart-transplanted patients, four parents, and three healthcare providers provided insight into relevant content for an educational resource through semi-standardized questionnaires and interviews. Their input guided the style and substance of the resource developed under the supervision of Fine Arts professors and the pediatric heart transplant team.Parents and healthcare providers were concerned about teenagers' health choices and lack of perspective while patients were more bothered by parental nagging and being careful about infections than worrying about post-transplant risks. The resource that was developed therefore used subtlety within a narrative medium: a graphic novel that involved mutant worms, secret plots, and daring escapes, to address identified medical concerns and encouragements without triggering teenage resistance to instruction.The discrepancies between the priorities of healthcare providers, parents, and teenage heart-transplant-patients illustrate the significance of basing resource-development on input from the target population. We developed the first graphic novel written for teenage heart-transplant-patients with patient input and interdisciplinary cooperation, using the subtlety of a narrative medium as a model for integrating medical content within an appealing, motivational, patient-centered, and age-appropriate resource.

Summary Background ABO-incompatible heart transplantation increases donor availability in young children and is evolving into standard of care in children younger than 2 years. Previous smaller studies suggest similar outcomes to ABO-compatible heart transplantation, but persisting alterations of the immune system in ABO-incompatible recipients might increase the risk of some infections or benefit the graft owing to reduced HLA reactivity. We aimed to assess long-term outcomes in young children after they received ABO-incompatible or ABO-compatible heart transplantation. Methods In this multicentre, prospective cohort study, we analysed data from the Pediatric Heart Transplant Society registry to compare children who received ABO-incompatible or ABO-compatible heart transplantation before age 2 years between Jan 1, 1999, and June 30, 2018. Given significantly different clinical demographics between the two groups, we also matched each ABO-incompatible recipient to two ABO-compatible recipients using propensity score matching. We assessed patient and graft survival, coronary allograft vasculopathy, malignancy, acute rejection (any episode resulting in augmentation of immunosuppression), and infections (requiring intravenous antibiotic or antiviral therapy or life-threatening infections treated with oral therapy). Findings We included 2206 children who received a heart transplant before age 2 years, with 11 332·6 patient-years of cumulative observation time. Children who received an ABO-incompatible transplant (n=364) were younger and a larger proportion had congenital heart disease and ventilator and mechanical circulatory support than the ABO-compatible recipients (n=1842). After matching, only differences in blood group (more O in ABO-incompatible and more AB in ABO-compatible groups) and use of polyclonal induction therapy with anti-thymocyte globulins persisted. The two matched groups had similar post-transplantation graft survival (p=0·74), freedom from coronary allograft vasculopathy (p=0·75), and malignancy (p=0·51). ABO-incompatible recipients showed longer freedom from rejection (p=0·0021) in the overall cohort, but not after matching (p=0·48). Severe infections (p=0·0007), bacterial infections (p=0·0005), and infections with polysaccharide encapsulated bacteria (p=0·0005) that share immunological properties with blood group antigens occurred less frequently after ABO-incompatible heart transplantation. Interpretation ABO-incompatible heart transplantation for children younger than 2 years is a clinically safe approach, with similar survival and incidences of rejection, coronary allograft vasculopathy, and malignancy to ABO-compatible recipients, despite higher-risk pre-transplant profiles. ABO-incompatible transplantation was associated with less bacterial infection, particularly encapsulated bacteria, suggesting that the acquired immunological changes accompanying ABO tolerance might benefit rather than jeopardise transplanted children. Funding Pediatric Heart Transplant Society.

The COVID-19 pandemic has had deleterious impacts on pediatric patients and families, as well as the healthcare providers who have attended to their care needs.In this qualitative study, children with a cardiac transplant, as well as their families and healthcare providers were interviewed to explore the impact of the COVID-19 pandemic on pediatric care, as well as on patients' and their families' daily lives. Participants were recruited from a children's hospital in western Canada. Fifteen caregiving parents of transplanted children, 2 young patients, and 8 healthcare providers participated in interviews.Findings highlighted how families and their healthcare providers experienced pandemic-related shifts. Themes highlighted experiences, which entailed (1) initially hearing about the COVID-19 pandemic; (2) learning about their new reality; (3) adjusting to the pandemic; (4) adjusting to shifts in pediatric services; (5) evolving a view on the future, and (6) offering recommendations for cardiac care in a pandemic.Study implications emphasize the need to critically reflect on, and advance, methods of helping young patients and their families in pandemic circumstances, and supporting healthcare providers.

VAD support for early graft failure after HTx is a rare event in pediatrics.We retrospectively describe our single-center experience with post-HTx VAD support in a cohort of patients transplanted between 01/05 and 12/20.Nine patients underwent VAD insertion in the early post-HTx period [median age 6.1 years (Range 0.3-20.3), median weight 17.6 kg (Range 3.5-65.0), and congenital heart disease (67%)]. Of the nine patients with early graft failure, almost half (44%) were implanted after 2015 and all of these patients had a pre-HTx plan for possible post-transplant VAD insertion. Time to VAD implant was a median of 0 day (Range 0-11). Total time on VAD support was a median of 12 days (Range 3.0-478.0). Two-thirds (n = 6; 67%) of the patients were weaned from support, retransplanted (11%) and two patients died (22%). In all of the patients where post-HTx VAD was anticipated there was 100% survival.In this small patient series, post-HTx VAD was a useful measure in selected patients especially with pre-HTx planning. However, more shared experiences to verify these findings are needed.

Objectives The COVID-19 pandemic has impacted mental health at a population level. Families of children with health vulnerabilities have been disproportionately affected by pandemic-related policies and service disruptions as they substantially rely on the health and social care system. We elicited the impact of the COVID-19 pandemic on children with health and disability-related vulnerabilities, their families, and their health care providers (HCPs). Methods Children with diverse health vulnerabilities (cardiac transplantation, respiratory conditions, sickle cell disease, autism spectrum disorder, mental health issues, and nearing the end of life due to a range of underlying causes), as well as their parents and HCPs, participated in semi-structured interviews. Data were analyzed using qualitative content analysis in determining themes related to impact and recommendations for practice improvement. Results A total of 262 participants (30 children, 76 parents, 156 HCPs) were interviewed. Children described loneliness and isolation; parents described feeling burnt out; and HCPs described strain and a sense of moral distress. Themes reflected mental health impacts on children, families, and HCPs, with insufficient resources to support mental health; organizational and policy influences that shaped service delivery; and recommendations to enhance service delivery. Conclusion Children with health vulnerabilities, their families and HCPs incurred profound mental health impacts due to pandemic-imposed public health restrictions and care shifts. Recommendations include the development and application of targeted pandemic information and mental health supports. These findings amplify the need for capacity building, including proactive strategies and mitigative planning in the event of a future pandemic.

BACKGROUND There are challenges in achieving and maintaining therapeutic tacrolimus levels after solid organ transplantation (SOT). The purpose of this genome-wide association study (GWAS) was to generate an integrated clinical and genetic prediction model for tacrolimus levels in pediatric SOT. METHODS In a multicenter prospective observational cohort study (2015-18), children

CD25, the alpha chain of the IL-2 receptor, is expressed on activated effector T cells that mediate immune graft damage. Induction immunosuppression is commonly used in solid organ transplantation and can include antibodies blocking CD25. However, regulatory T cells (Tregs) also rely on CD25 for their proliferation, survival, and regulatory function. Therefore, CD25-blockade may compromise Treg protective role against rejection. We analysed in vitro the effect of basiliximab (BXM) on the viability, phenotype, proliferation and cytokine production of Treg cells. We also evaluated in vivo the effect of BXM on Treg in thymectomized heart transplant children receiving BXM in comparison to patients not receiving induction therapy. Our results show that BXM reduces Treg counts and function in vitro by affecting their proliferation, Foxp3 expression, and IL-10 secretion capacity. In pediatric heart-transplant patients, we observed decreased Treg counts and a diminished Treg/Teff ratio in BXM-treated patients up to 6-month after treatment, recovering baseline values at the end of the 12-month follow up period. These results reveal that the use of BXM could produce detrimental effects on Tregs, and support the evidence suggesting that BXM induction could impair the protective role of Tregs in the period of highest incidence of acute graft rejection.

Atopic disorders are more common in children after heart transplant (HTx). We hypothesized that HTx at an early age and thymus excision (TE) affect development of T and B cells, especially regulatory T cells (Tregs), which help maintain tolerance.In this single-center study including 24 patients transplanted between 2013 and 2018, we investigated lymphocyte patterns in relation to these factors using flow cytometry. Clinical data were collected from standardized questionnaires and medical charts. Patients were stratified into TE and non-TE groups as well as patients with and without post-transplant atopy development/worsening.64% of TE patients experienced new or worsening asthma/eczema post-transplant compared to 20% of non-TE patients. TE patients had higher total Treg proportions (CD4+CD25+CD127lo) than non-TE patients (p = .043), but borderline significantly lower naïve Tregs (CD45RA+CD27-) (p = .057). Memory CD4+ T cells were higher in TE patients in trend (p = .084). Total Tregs did not differ between atopic/nonatopic groups, although naïve Tregs were significantly lower in atopic patients (p = .028). Memory CD4+ T cells were higher in atopic patients in trend (p = .082). IgM+IgD+ B cells were higher in nonatopic patients in trend (p = .064).New/worsening atopy is more common in thymectomized HTx children and is associated with alterations in T-cell profiles. Avoiding TE may prevent these alterations and reduce incidence of atopy post-HTx.

Purpose Children with cardiomyopathy are at risk of heart failure with reduced physical activity (PA) as a cardinal manifestation. Clinical assessment of PA in children is challenging due to the limited validity of subjective reports. The aim of the study was to compare accelerometery measurement with parental report and to identify factors associated with movement behavior (PA, sedentary time, steps per day). Method Fifteen patients with cardiomyopathy (mean, 9.7 years; 64% male) were asked to wear an Actigraph GT3X accelerometer in Edmonton, Canada. Demographics, clinical characteristics, parental-reported PA, and health-related quality of life data were also collected. Results Participants engaged in a median of 38 minutes of moderate-vigorous PA per day with higher levels in boys versus girls (73.9 [25.03, 78.91] vs 4.13 [2.53, 37.67] minutes, P = .03). Children participating in recreational sports showed a higher level of moderate-vigorous PA (73.92 min/d) compared with those who did not participate (73.9 vs 22.7 min/d, P = .05), and positive family outlook on the child's health was associated with less sedentary time (P = .04). Conclusion Accelerometer measurement in children with cardiomyopathy is an achievable and more objective measure of PA compared with parental report alone and highlighted low levels of PA among these children.

Background Ventricular assist device (VAD) therapy has become an important tool for end-stage heart failure. VAD therapy has increased survival but is associated with complications including the development of human leukocyte antigen (HLA) antibodies. We sought to determine the incidence of HLA antibody development post-VAD insertion, across the age spectrum, in patients receiving leukocyte-reduced blood products, with standardized HLA antibody detection methods and to investigate factors associated with antibody development. Methods This was a retrospective analysis of all patients who underwent durable VAD placement between 2005 and 2014. Inclusion criteria included availability of pre- and post-VAD HLA antibody results. Associations between HLA antibody development in the first-year postimplant and patient factors were explored. Results Thirty-nine adult and 25 pediatric patients made up the study cohort. Following implant, 31% and 8% of patients developed new class I and class II antibodies. The proportion of newly sensitized patients was similar in adult and pediatric patients. The class I HLA panel reactive antibody only significantly increased in adults. Pre-VAD sensitization, age, sex (pediatrics), and transfusion were not associated with the development of HLA antibodies. Conclusions In a cohort of VAD patients receiving leukocyte-reduced blood products and standardized HLA antibody testing, roughly one-third developed new class I antibodies in the first-year postimplant. Adults showed significantly increased class I panel reactive antibody following VAD support. No patient-related factors were associated with HLA antibody development. Larger prospective studies are required to validate these findings and determine the clinical impact of these antibodies following VAD insertion.

Background We aimed to identify care processes and structures that were independently associated with higher medication adherence among young transplant recipients. Methods We conducted a prospective, observational cohort study of 270 prevalent kidney, liver, and heart transplant recipients 14-25 years old. Patients were ≥3 months post-transplant, ≥2 months post-discharge, and followed in one of 14 pediatric or 14 adult transplant programs in Canada. Patients were enrolled between June 2015 and March 2018 and followed for 6 months. Adherence was assessed at baseline, 3, and 6 months using the BAASIS© self-report tool. Patients were classified as adherent if no doses were missed in the prior 4 weeks. Transplant program directors and nurses completed questionnaires regarding care organization and processes. Results Of the 270 participants, 99 were followed in pediatric programs and 171 in adult programs. Median age was 20.3 years, and median time since transplant was 5 years. At baseline, 71.5% were adherent. Multivariable mixed effects logistic regression models with program as a random effect identified two program-level factors as independently associated with better adherence: minimum number of prescribed blood draws per year for those >3 years post-transplant (per 1 additional) (OR 1.12 [95% CI 1.00, 1.26]; p = .047), and average time nurses spend with patients in clinic (per 5 additional minutes) (OR 1.15 [1.03, 1.29]; p = .017). Conclusion Program-level factors including protocols with a greater frequency of routine blood testing and more nurse time with patients were associated with better medication adherence. This suggests that interventions at the program level may support better adherence.

Retransplantation is rare and associated with worse survival and more morbidity. The study aim is to describe an updated cohort of pediatric retransplants, determine if there has been an era effect on outcomes, and understand if identified trends are explained by changes in patient selection.Pediatric Heart Transplant Society database analysis of retransplantation patients18 years of age (Era 1: 1993-2001, Era 2: 2002-2010, Era 3: 2011-2018). Multivariate analysis identified risk factors for graft loss. Multiphase parametric hazard modeling was used to depict era and risk factor effect.Survival was lower (p.0001) for retransplant (n = 222) compared to primary transplant (n = 6548) (median 9.3 vs 20.2 years). Median survival increased from Era 1 to 2 (4.8 vs 9.3 years; p.0001) with no incremental change in Era 3. Era 2 and 3 retransplants had a longer inter-transplant interval (p.0001), were less frequently for early graft failure (p = .0004) or acute rejection (p = .007), more frequently from a ventricular assist device (p = .0014), and less frequently from extracorporeal membrane oxygenation (p = .0024). Predictors of graft loss included Era 1 (HR 10.55, p = .001), congenital heart disease (HR 4.42, p = .01), inter-transplant interval1 year (HR 5.34, p = .002), and mechanical support (ventricular assist device HR 7.47, p = .0042; extracorporeal membrane oxygenation HR 10.09, p.0001). For each 1-year increase in inter-transplant interval, graft loss risk decreased by 1.15 (p = .0002). Retransplantation was associated with more rejection, infection, and allograft vasculopathy.Graft survival has improved in pediatric retransplants making it a viable option in select patients. Retransplantation should be avoided in the setting of early graft failure especially requiring mechanical support.

Background/objectives: Determination of Cytomegalovirus (CMV) status in solid organ transplant (SOT) candidates is essential to stratify risk of post-transplant CMV disease. Passive transfusion-acquired antibodies can make serologic determination of CMV status unreliable. We evaluated 3 assays, not affected by passive antibodies (PA), in assignment of CMV status: quantification of CMV-specific CD4 + T-cells (CMV-TC) and exhausted CD27-CD28- CD4 + T-cells, and detection of CMV DNA with Nucleic Acid Amplification Testing (NAAT). Study design: We enrolled 50 adults awaiting SOT and 50 immunocompetent age-matched controls, and collected a throat swab, urine, saliva and blood sample on each. Using flow cytometry CD4 + T-cells were phenotypically analyzed for expression of CD27 and CD28 and CMV-specific CD4 + T-cells were identified by CD69 expression and intracellular IFN-γ quantification after stimulation with CMV-antigen lysate. CMV NAAT was performed on all specimens using real-time PCR. CMV serology (CMV IgG) was determined by enzyme immunoassay. Subjects were considered to have potential PA if they received blood products within 2 months of collection. Results: The CMV-TC assay discriminated between CMV-seropositive and seronegative SOT candidates without PA well (sensitivity 79%, specificity 93%) while the CD27-CD28-CD4 + T-cell assay had good sensitivity (86%) but specificity of 74%. Detection of CMV DNA was uncommon in CMV-seropositive SOT candidates (2/21). Conclusions: Given its high specificity, the CMV-TC assay is valuable in confirming true-positive CMV status in seropositive SOT candidates with PA, while use of CD27-CD28-CD4 + T-cell analysis is limited by moderate specificity. Detection of CMV DNA is of limited value in assignment of CMV status in adults.

Background Ventricular assist devices (VADs) are commonly used as a bridge to transplantation but may yield HLA sensitization. We evaluated the prevalence of HLA antibody (Ab) sampling pre- and post-VAD placement in pediatric and adult patients and notification of VAD status to the HLA laboratory. Methods All pediatric and adult patients who received a first-time VAD between 2005 and 2013 were included in this single-center retrospective review. Data were collected from the University of Alberta Hospital histocompatibility laboratory's information system and a local VAD database. Results In total, 106 patients were included (40 pediatric, median 3.0 years [interquartile range, 0.3-10.7]; 66 adult, 55.0 years [46.8-61.2]). HLA Ab sampling within 1-month pre-VAD occurred in 70% of pediatric and 79% of adult recipients (P = .215). Testing within 1 month of VAD placement occurred in 89% of pediatric and 67% of adult recipients (P = .012). For those with HLA Ab sampling within 30 days postimplant, notification to the HLA laboratory of VAD status occurred in 19 of 27 (70%) pediatric and 24 of 33 (73%) adult patients (P = .533). Of patients transplanted post VAD with HLA Ab samples collected, 12 of 28 (43%) and 13 of 38 (34%) adult recipients did not have notification of VAD status to the HLA laboratory (P = .322). Conclusions There were inconsistencies in HLA Ab sampling and communication to the HLA laboratory surrounding VAD placement. Standardization of both HLA Ab assessment frequency after VAD implantation and communication regarding changes in clinical status and the occurrence of key sensitizing events such as VAD placement are imperative as patients await transplantation.

Background Freedom from rejection in pediatric heart transplant recipients is highly variable across centers. This study aimed to assess the center variation in methods used to diagnose rejection in the first-year post-transplant and determine the impact of this variation on patient outcomes. Methods The PHTS registry was queried for all rejection episodes in the first-year post-transplant (2010-2019). The primary method for rejection diagnosis was determined for each event as surveillance biopsy, echo diagnosis, or clinical. The percentage of first-year rejection events diagnosed by surveillance biopsy was used to approximate the surveillance strategy across centers. Methods of rejection diagnosis were described and patient outcomes were assessed based on surveillance biopsy utilization among centers. Results A total of 3985 patients from 56 centers were included. Of this group, 873 (22%) developed rejection within the first-year post-transplant. Surveillance biopsy was the most common method of rejection diagnosis (71.7%), but practices were highly variable across centers. The majority (73.6%) of first rejection events occurred within 3-months of transplantation. Diagnosis modality in the first-year was not independently associated with freedom from rejection, freedom from rejection with hemodynamic compromise, or overall graft survival . Conclusions Rejection in the first-year after pediatric heart transplant occurs in 22% of patients and most commonly in the first 3 months post-transplant. Significant variation exists across centers in the methods used to diagnose rejection in pediatric heart transplant recipients, however, these variable strategies are not independently associated with freedom from rejection, rejection with hemodynamic compromise, or overall graft survival.

BACKGOUND: B cells contribute to chronic transplant rejection by producing donor-specific antibodies and promoting T cell response, but how these processes are regulated at the transcriptional level remains unclear. Herein, we investigate the role of transcription factor interferon regulatory factor 4 (IRF4) in controlling B cell response during chronic transplant rejection. METHODS: We generated the Irf4(gfp) reporter mice to determine IRF4 expression in B cell lineage. We then used mice with B cell-specific IRF4 deletion to define the role of IRF4 in B cell response after NP-KLH immunization or allogeneic heart transplantation. In particular, graft survival and histology, as well as B and T cell responses, were evaluated after transplantation. RESULTS: IRF4 is dynamically expressed at different stages of B cell development and is absent in germinal center (GC) B cells. However, IRF4 ablation in the B cell lineage primarily eliminates GC B cells in both naïve and NP-KLH immunized mice. In the transplantation setting, IRF4 functions intrinsically in B cells and governs allogeneic B cell responses at multiple levels, including GC B cell generation, plasma cell differentiation, donor-specific antibody production, and support of T cell response. B cell-specific IRF4 deletion combined with transient CTLA4-Ig treatment abrogates acute and chronic cardiac allograft rejection in naïve recipient mice but not in donor skin-sensitized recipients. CONCLUSIONS: B cells require IRF4 to mediate chronic transplant rejection. IRF4 ablation in B cells abrogates allogeneic B cell responses and may also inhibit the ability of B cells to prime allogenic T cells. Targeting IRF4 in B cells represents a potential therapeutic strategy for eliminating chronic transplant rejection.

Purpose Patient-reported outcome measures (PROMs) are standardized instruments used to collect data about the subjective assessment of medical care from the patient perspective. Implementing PROMs within pediatric clinical settings has gained increasing importance as health services prioritize patient-centred pediatric care. This study explores the perspectives of pediatric solid organ transplant patients, caregivers, and healthcare practitioners (HCPs) on implementing PROMs into clinical practice. Methods Qualitative description methods were used to elicit stakeholder perspectives. Semi-structured interviews were conducted across five Canadian transplant centres. Purposive sampling was used to obtain maximum variation across age, gender, and transplant program for all participants, as well as discipline for HCPs. Results The study included a total of 63 participants [patients (n = 20), caregivers (n = 22) and HCPs (n = 21)]. Nearly all participants endorsed the implementation of PROMs to enhance pediatric transplant clinical care. Three primary roles for PROMs emerged: (1) to bring a transplant patient’s overall well-being into the clinical care conversation; (2) to improve patient communication and engagement; and, (3) to inform the practice of clinical pediatric transplant care. Insights for effective implementation included completing electronic PROMs remotely and prior to clinical appointments by patients who are eight to 10 years of age or older. Conclusions This study contributes to current research that supports the use of PROMs in clinical pediatric care and guides their effective implementation into practice. Future directions include the development, usability testing, and evaluation of a proposed electronic PROM platform that will inform future research initiatives.

AIM To describe the clinical and hemodynamic characteristics of Fontan failure in children listed for heart transplant. METHODS In a nested study of the Pediatric Heart Transplant Society, 16 centers contributed information on Fontan patients listed for heart transplant between 2005and 2013. Patients were classified into four mutually exclusive phenotypes: Fontan with abnormal lymphatics (FAL), Fontan with reduced systolic function (FRF), Fontan with preserved systolic function (FPF), and Fontan with "normal" hearts (FNH). Primary outcome was waitlist and post-transplant mortality. RESULTS 177 children listed for transplant were followed over a median 13 (IQR 4-31) months, 84 (47%) were FAL, 57 (32%) FRF, 22 (12%) FNH, and 14 (8%) FPF. Hemodynamic characteristics differed between the 4 groups: Fontan pressure (FP) was most elevated with FPF (median 22, IQR 18-23, mmHg) and lowest with FAL (16, 14-20, mmHg); cardiac index (CI) was lowest with FRF (2.8, 2.3-3.4, L/min/m2). In the entire cohort, 66% had FP >15 mmHg, 21% had FP >20 mmHg, and 10% had CI

Background Pediatric patients undergoing heart transplant have a number of factors predisposing them to become fluid-overloaded, including capillary leak syndrome. Capillary leak and FO are associated with organ injury and may influence both short- and long-term outcomes. This study aimed to 1) determine the extent, timing, and predictors of post-operative FO and 2) investigate the association of FO with clinically important outcomes. Methods Between 2000 and 2012, 70 children less than 6 years old had a heart transplant at our institution. This was a secondary analysis of data from an ongoing prospective cohort study. Results FO, defined as cumulative fluid balance greater than 10% of body weight in the first 5 post-operative days, occurred in 16/70 patients (23%); 7 of these had more than 20% FO. Shorter donor ischemic time and longer cardiopulmonary bypass time were independently associated with increased risk of FO. FO >20% was a statistically significant independent predictor of mortality (P = .005), ventilation time, and PICU length of stay. There was no statistically significant association between identified neurodevelopment domains and FO. Conclusions Our single-center experience demonstrates that FO was common after pediatric heart transplant and was associated with worse clinical outcomes. FO is a potentially modifiable factor, and research is needed to better determine risk factors and whether intervention to reduce FO can improve outcomes in pediatric heart transplant patients.

Like other recipients of health care services, pediatric patients and their families/caregivers have been profoundly impacted by health care shifts and broader societal restrictions associated with the COVID-19 pandemic. An online roundtable discussion was facilitated with 7 pediatric clinicians and investigators of a current study examining the impacts of COVID-19 on pediatric care at multiple Canadian sites. Discussants represented a range of pediatric specialities: developmental disability, mental health, cardiac transplantation, respiratory medicine, hematology, and palliative care. We offer the transcript of the roundtable in which discussants reflected on clinical and programmatic experiences of the pandemic, including perceived impacts on children receiving care and their families, potential opportunities for improved health care delivery, impacts on health care providers, and recommendations as we move toward easing restrictions and pandemic recovery. Discussants convey a range of considerations that may have varying relevance for pediatric specialities in terms of practice and program planning.

BACKGROUND There is limited information about HRQL after pediatric heart transplantation at a young age. METHODS Prospective follow-up study of children who received a heart transplant at age ≤4 years. HRQL was assessed using the PedsQLTM 4.0 at age 4.5 years. This cohort was compared with healthy children, children with CHD, and with chronic conditions. Peri-operative factors associated with HRQL were also explored. RESULTS Of 66 eligible patients, 15 (23%) died prior to the HRQL assessment and 2 (3%) were lost to follow-up, leaving 49 patients. Indication for transplantation was CHD in 27 (55%) and CMP in 22 (45%). Median age (IQR) at transplant was 9 (5-31) months. HRQL was significantly lower in transplanted children compared to population norms (65.3 vs 87.3, P

Purpose Socioeconomic disparities negatively impacts outcomes in heart transplantation (HTx). However, the impact of insurance status and the social construct of race in pediatric patients has not been well studied. Methods The Pediatric Heart Transplant Society registry was queried between January 1, 2000- December 31, 2019. Patients were stratified by insurance status: US government (USG), US private (USP) and Single Payer (SP, UK & Canada) and race (black, white, other). Patients with a selection of more than one race were classified as other. Outcomes after HTx were assessed by Kaplan Meier log rank test including graft survival, time to first cardiac allograft vasculopathy (CAV), rejection, hemodynamic compromised (HC) rejection, and malignancy. Results 5879 children underwent HTx with insurance status as follows: 2800 USG (48%), 2431 USP (41%) and 648 SP (11%). Race breakdown included: 4086 white, 1052 black and 936 other. At 10 years post-transplant, graft survival (65.8% USG, 72.6% USP, 77% SP, p= .0005), time to first CAV (73.5% USG, 77.7% USP, 94.6% SP, p Conclusion In this multinational analysis of pediatric HTx patients, USG was associated with worse post-HTx outcomes. When stratified by race, graft survival was worse in black patients with USG and USP insurance. Both insurance and the social construct of race contribute to worse outcomes post heart transplant and may represent disparity in access to care and other racial bias. These results highlight the importance of further work in this area.

Purpose There are limited data reporting outcomes of children with trisomy 21 undergoing heart transplantation (HTx). This project reports the waitlist and post-HTx outcomes of children with trisomy 21. Methods This is a retrospective cohort study of children with trisomy 21 listed for or who underwent HTx at 11 centers within North America and internationally. Demographic, medical, surgical, and post-HTx outcome data were collected and described. Results Twenty-one patients with trisomy 21 were listed for HTx from 1992 through 2019 (median age 8.5y, 43% male, 52% white). High-risk or failed repair of congenital heart disease was the indication for transplant in 16 (76%) patients with atrioventricular septal defect being the most common (N=12). Other diagnoses included dilated cardiomyopathy in 4 patients (secondary to anthracyclines in 2) and myocarditis in 1 patient. A total of 18 (86%) patients survived to transplant. Of this group, support at the time of transplant included inotropes (N=10, 56%), ventricular assist device (N=7, 39%), and mechanical ventilation (N=2, 11%). No patients required post-operative extracorporeal membrane oxygenation or dialysis. All centers reported the use of standard immunosuppression without alterations secondary to trisomy 21. All transplanted patients survived to hospital discharge with a median post-HTx length of stay of 19d. With a median follow-up of 2.9y, 16 (89%) patients were alive, 5 (28%) had rejection within the 1st year post-HTx, 2 (11%) developed post-transplant lymphoproliferative disorder (PTLD), and 7 (39%) were hospitalized for infection within the 1st year post-HTx. For the two post-HTx mortalities, the causes of death were 1) coronary allograft vasculopathy at 22y post-HTx and 2) multiple episodes of rejection and PTLD at 1.5y post-HTx (Figure). Conclusion Waitlist and intermediate post-HTx outcomes are acceptable in children with trisomy 21. The presence of trisomy 21 should not be an absolute contraindication to heart transplantation in the appropriate clinical setting.

Background Glutaraldehyde (GA) treatment of allografts used for arch reconstruction prevents the immunologic sensitization that occurs with untreated allografts, but its use may cause tissue changes that predispose to recurrent obstruction. The objective was to determine whether GA treatment of allografts used in Norwood procedures increases the risk of recurrent aortic obstruction. Methods All infants who underwent a Norwood procedure between 2000 and 2015 were included. Cryopreserved pulmonary allografts were used for all arch reconstructions; starting in 2005 all were treated with GA before use. Complete follow-up was obtained, including survival, transplantation, and all repeat procedures. Competing risks analyses were used to assess for differences in aortic reintervention over time. Results Two hundred six infants (132 male) were included. There were 60 deaths and 14 transplantations; 5-year transplantation-free survival was 71.9%. GA treatment of patches (n = 142, 68.9%) was not predictive of death (hazard ratio [HR] 1.38, 95% confidence interval [CI]: 0.61 to 3.08). Fifty-five patients had at least one aortic reintervention and 31 patients (15.0%) required surgical aortic reintervention. At 1-year, freedom from all aortic reintervention was similar between patients with and without treated patches, but freedom from surgical aortic reintervention was lower in the treated group (87.6% versus 95.3%, p = 0.0256). GA treatment was not associated with the combined end point of catheter-based or surgical reintervention but was associated with specific need for surgical reintervention (HR 4.05, 95% CI: 1.19 to 13.77). Conclusions GA treatment is associated with increased late surgical aortic reintervention. The advantages of decreased sensitization with GA treatment need to be balanced against the risk of aortic reobstruction.

Heart transplantation from ABO incompatible (ABOi) donors has evolved into a progressively accepted therapy in young children. We assessed the recent practice of ABOi listing impact on waitlist and post-transplant outcomes.Using the Pediatric Heart Transplant Society registry, we compared clinical presentation, waitlist parameters, and post-transplant survival of children2 years of age listed for ABOi vs ABO compatible (ABOc) heart transplant between January 2010 and June 2018 with sub-analysis of blood group O recipients.Among 2,039 patients, ABOi listing increased significantly with time from 49% (2010) to 72% (2017). ABOi-listed patients had lower age and body surface area, and higher proportion of congenital heart disease, mechanical ventilation, and high urgency status (all p0.01). Use of mechanical circulatory support was similar between groups. Of 1,288 patients reaching transplant, 239 (18.6%) received an ABOi organ (15%-40%/year). Death while waiting, removal from the waitlist, and waitlist survival were similar between groups. Time to transplant was significantly shorter for ABOi listing in blood group O patients (p0.02), approaching significance (p = 0.057) for all blood groups. Post-transplant survival was similar except for lower survival of patients listed ABOc but transplanted ABOi. These patients showed increasing need for mechanical circulatory support and high urgency listing while waiting.In the current era, primary listing for ABOi heart transplant has become routine for the majority of children2 years old, resulting in shorter waitlist time, especially in blood group O. Post-transplant survival is similar despite ABOi-listed children still showing a higher risk profile.

Passive antibodies, maternal or transfusion-acquired, make serologic determination of pretransplant cytomegalovirus (CMV) status unreliable. We evaluated 3 assays unaffected by passive antibodies, in assignment of CMV infection status in children awaiting solid organ transplant and in controls: (1) CMV nucleic acid amplification testing (NAAT), (2) quantification of CMV-specific CD4+ T cells, and (3) quantification of CD27-CD28-CD4+ T cells. Our results highlight that CMV NAAT, from urine and oropharynx, is useful in confirming positive CMV status. Detection of CMV-specific CD4+ T cells was sensitive and specific in children >18 months but was less sensitive in children

Background Despite age-related differences in biology, physiology, and behavior, transplant immunosuppression is not tailored by age. This likely contributes to high graft failure and posttransplant complications. We present the aims, design, and methods of the Pediatric Outcomes in Transplant: PersOnaliSing Immunosuppression To ImproVe Efficacy Study aimed at personalizing posttransplant immunosuppression in children and young adults. Methods In this prospective observational cohort study, we recruited pediatric and young adult solid organ transplant, pediatric allogeneic hematopoietic stem cell transplant recipients, and matched living and deceased organ donors from 14 transplant centers across Canada. Clinical data, questionnaires, biospecimens, and pharmacy records were collected at serial time points: (1) to identify genetic and host immune factors that influence immunosuppression dose requirements across different ages and transplant types, (2) to identify viral-host interactions that increase susceptibility to Epstein-Barr virus infection, and (3) to define care processes and structures associated with medication adherence in adolescents and young adults. Results From 2015 to 2018, 1662 new and prevalent transplant recipients were screened, 1166 were recruited for the various aims, including 370 liver, 445 kidney, 277 heart, 19 lung, 19 multiple, and 36 hematopoietic stem cell transplant transplants. Twelve percent were younger than 2 years, 30% were 2 to 10 years, 42% were 10 to 18 years, and 16% were 18 to 24 years at enrollment. Nine hundred thirty-one consented to participation in aims 1 and 2 (90% consent rate), 287 to aim 3 (82% consent rate). Biospecimens collected included 898 for DNA, 276 for immunoassays, and 717 for biomarker studies. Seventy percent participants have completed follow-up; 30% are pending study completion. Conclusions The design of this national multicenter cross-organ network helped maximize recruitment of a large patient cohort for studying age and organ-related differences in immunosuppression needs that would not otherwise be feasible. Leveraging the unique clinical, biological, environmental, and behavioral characteristics of this cohort will help develop precision medicine strategies for individualizing posttransplant immunosuppression.

The importance of B cell and antibody-mediated immune response in the acute and long-term persistence of transplanted solid organs has become increasingly evident in recent years. A variety of therapeutic innovations target antibodies directed toward HLA or blood groups (ABO) to allow better allocation and posttransplant longevity of organs. Antibodies originate from plasma cells (PCs), which are terminally differentiated B cells. Long-term production and persistence of these antibodies is partly due to fast reactivation of previously generated memory B cells; however, there is increasing evidence that some differentiated PCs can persist independently in the bone marrow for years or even decades, producing specific antibodies or even experiencing regeneration without proliferation without need to be replaced by newly differentiating B cells. This review outlines the currently presumed pathways of differentiation, antibody, and memory generation on both B-cell and PC levels. On this background, current therapeutic concepts for antibody reduction before and after solid organ transplantation are considered, to better understand their mechanisms, possible synergisms, and specific risks. Specific differences in regards to ABO versus HLA antibodies as well as practical relevance for generation of desensitization and posttransplant antibody-directed therapy protocols are discussed.

Background. Despite age-related differences in biology, physiology, and behavior, transplant immunosuppression is not tailored by age. This likely contributes to high graft failure and posttransplant complications. We present the aims, design, and methods of the Pediatric Outcomes in Transplant: PersOnaliSing Immunosuppression To ImproVe Efficacy Study aimed at personalizing posttransplant immunosuppression in children and young adults. Methods. In this prospective observational cohort study, we recruited pediatric and young adult solid organ transplant, pediatric allogeneic hematopoietic stem cell transplant recipients, and matched living and deceased organ donors from 14 transplant centers across Canada. Clinical data, questionnaires, biospecimens, and pharmacy records were collected at serial time points: (1) to identify genetic and host immune factors that influence immunosuppression dose requirements across different ages and transplant types, (2) to identify viral-host interactions that increase susceptibility to Epstein-Barr virus infection, and (3) to define care processes and structures associated with medication adherence in adolescents and young adults. Results. From 2015 to 2018, 1662 new and prevalent transplant recipients were screened, 1166 were recruited for the various aims, including 370 liver, 445 kidney, 277 heart, 19 lung, 19 multiple, and 36 hematopoietic stem cell transplant transplants. Twelve percent were younger than 2 years, 30% were 2 to 10 years, 42% were 10 to 18 years, and 16% were 18 to 24 years at enrollment. Nine hundred thirty-one consented to participation in aims 1 and 2 (90% consent rate), 287 to aim 3 (82% consent rate). Biospecimens collected included 898 for DNA, 276 for immunoassays, and 717 for biomarker studies. Seventy percent participants have completed follow-up; 30% are pending study completion. Conclusions. The design of this national multicenter cross-organ network helped maximize recruitment of a large patient cohort for studying age and organ-related differences in immunosuppression needs that would not otherwise be feasible. Leveraging the unique clinical, biological, environmental, and behavioral characteristics of this cohort will help develop precision medicine strategies for individualizing posttransplant immunosuppression.

Purpose ABO-incompatible (ABOi) heart transplantation (HTx) has become a standard approach for infants with low isohemagglutinin titers (ISO). ABOi HTx may also be safe for older pediatric patients with altered immune response, however, thresholds are yet to be defined. Methods Data on management, clinical course and ISO were analyzed from two patients undergoing ABOi HTx beyond infancy. Results A 4-yr old ABO-O girl with hypoplastic left heart syndrome developed refractive protein-losing enteropathy, effusions and edema shortly after Fontan palliation, in the context of AV valve regurgitation and ventricular dysfunction. She was listed for HTx and deemed high-risk due to elevated pulmonary vascular resistance, HLA sensitization (cPRA 81 %), and need for ventilatory support. Despite her age, ISO titers were only moderately high (anti-A 1:32; anti-B 1:16); she underwent ABOi HTx (donor ABO-B) with plasmapheresis, ATG and methylprednisolone induction which was expanded for rituximab and IVIG. She required temporary right ventricular support and dialysis after HTx. Immunosuppression was maintained with tacrolimus and mycophenolate mofetil (MMF), modified during the clinical course to now receiving sirolimus / MMF for the past 6 years. Her B-ISO titres never exceeded 1:2 post-transplant. She remains free of rejection and graft vasculopathy now 9.5 years post-HTx. Another 4-yr old ABO-O girl with microdeletion 22q11 syndrome, pulmonary atresia, ventricular septal defect and MAPCAs sustained coronary artery injury resulting in ventricular dysfunction, requiring ECMO followed by milrinone dependency. She was listed for HTx and was highly HLA sensitized (cPRA 92%). Desensitisation was initiated with rituximab and IVIG; her A-ISO (peak anti-A 1:128) dropped to 1:16 at which point her listing was opened to ABOi. She received an ABOi HTx (donor ABO-A) at age 5 11/12 years, not crossing donor-specific HLA antibodies, receiving plasma exchange, ATG induction and methylprednisolone. Maintenance therapy included tacrolimus and MMF. She remains free of rejection now 1.5 years post-HTx with anti-A titre never exceeding 1:4. Conclusion ABOi HTx can be performed safely in selected older pediatric patients if ISO are low even secondary to immune manipulation. This approach may offer a long-term HTx option for older children who are highly sensitized or in urgent need of transplantation.