Immunologic risk stratification of pediatric heart transplant patients by combining HLA-EMMA and PIRCHE-II.

Human leukocyte antigen (HLA) molecular mismatch is a powerful biomarker of rejection. Few studies have explored its use in assessing rejection risk in heart transplant recipients. We tested the hypothesis that a combination of HLA Epitope Mismatch Algorithm (HLA-EMMA) and Predicted Indirectly Recognizable HLA Epitopes (PIRCHE-II) algorithms can improve risk stratification of pediatric heart transplant recipients. Class I and II HLA genotyping were performed by next-generation sequencing on 274 recipient/donor pairs enrolled in the Clinical Trials in Organ Transplantation in Children (CTOTC). Using high-resolution genotypes, we performed HLA molecular mismatch analysis with HLA-EMMA and PIRCHE-II, and correlated these findings with clinical outcomes. Patients without pre-formed donor specific antibody (DSA) (n=100) were used for correlations with post-transplant DSA and antibody mediated rejection (ABMR). Risk cut-offs were determined for DSA and ABMR using both algorithms. HLA-EMMA cut-offs alone predict the risk of DSA and ABMR; however, if used in combination with PIRCHE-II, the population could be further stratified into low-, intermediate-, and high-risk groups. The combination of HLA-EMMA and PIRCHE-II enables more granular immunological risk stratification. Intermediate-risk cases, like low-risk cases, are at a lower risk of DSA and ABMR. This new way of risk evaluation may facilitate individualized immunosuppression and surveillance.

Molecular events contributing to successful pediatric cardiac transplantation in HLA sensitized recipients.

Antibodies to HLA resulting in positive cytotoxicity crossmatch are generally considered a contraindication for cardiac transplantation. However, cardiac transplantations have been performed in children by reducing the Abs and modifying immunosuppression. To identify mechanisms leading to allograft acceptance in the presence of Abs to donor HLA, we analyzed priming events in endothelial cells (EC) by incubating with sera containing low levels of anti-HLA followed by saturating concentration of anti-HLA. Pre-transplant sera were obtained from children with low levels of Abs to HLA who underwent transplantation. EC were selected for donor HLA and exposed to sera for 72 h (priming), followed by saturating concentrations of anti-HLA (challenge). Priming of EC with sera induced the phosphatidylinositol 3-kinase/Akt mediated by the BMP4/WNT pathway and subsequent challenge with panel reactive antibody sera increased survival genes Bcl2 and Heme oxygenase-1, decreased adhesion molecules, induced complement inhibitory proteins and reduced pro-inflammatory cytokines. In contrast, EC which did not express donor HLA showed decreased anti-apoptotic genes. Primed EC, upon challenge with anti-HLA, results in increased survival genes, decreased adhesion molecules, induction of complement inhibitory proteins, and downregulation of pro-inflammatory cytokines which may result in accommodation of pediatric cardiac allografts despite HLA sensitization.

The Influence of Race and Common Genetic Variations on Outcomes After Pediatric Heart Transplantation.

Significant racial disparity remains in the incidence of unfavorable outcomes following heart transplantation. We sought to determine which pediatric posttransplantation outcomes differ by race and whether these can be explained by recipient demographic, clinical, and genetic attributes. Data were collected for 80 black and 450 nonblack pediatric recipients transplanted at 1 of 6 centers between 1993 and 2008. Genotyping was performed for 20 candidate genes. Average follow-up was 6.25 years. Unadjusted 5-year rates for death (p = 0.001), graft loss (p = 0.015), acute rejection with severe hemodynamic compromise (p = 0.001), late rejection (p = 0.005), and late rejection with hemodynamic compromise (p = 0.004) were significantly higher among blacks compared with nonblacks. Black recipients were more likely to be older at the time of transplantation (p < 0.001), suffer from cardiomyopathy (p = 0.004), and have public insurance (p < 0.001), and were less likely to undergo induction therapy (p = 0.0039). In multivariate regression models adjusting for age, sex, cardiac diagnosis, insurance status, and genetic variations, black race remained a significant risk factor for all the above outcomes. These clinical and genetic variables explained only 8-19% of the excess risk observed for black recipients. We have confirmed racial differences in survival, graft loss, and several rejection outcomes following heart transplantation in children, which could not be fully explained by differences in recipient attributes.

Elevated ST2 Distinguishes Incidences of Pediatric Heart and Small Bowel Transplant Rejection.

Elevated serum soluble (s) suppressor of tumorigenicity-2 is observed during cardiovascular and inflammatory bowel diseases. To ascertain whether modulated ST2 levels signify heart (HTx) or small bowel transplant (SBTx) rejection, we quantified sST2 in serially obtained pediatric HTx (n = 41) and SBTx recipient (n = 18) sera. At times of biopsy-diagnosed HTx rejection (cellular and/or antibody-mediated), serum sST2 was elevated compared to rejection-free time points (1714 ± 329 vs. 546.5 ± 141.6 pg/mL; p = 0.0002). SBTx recipients also displayed increased serum sST2 during incidences of rejection (7536 ± 1561 vs. 2662 ± 543.8 pg/mL; p = 0.0347). Receiver operator characteristic (ROC) analysis showed that serum sST2 > 600 pg/mL could discriminate time points of HTx rejection and nonrejection (area under the curve [AUC] = 0.724 ± 0.053; p = 0.0003). ROC analysis of SBTx measures revealed a similar discriminative capacity (AUC = 0.6921 ± 0.0820; p = 0.0349). Quantitative evaluation of both HTx and SBTx biopsies revealed that rejection significantly increased allograft ST2 expression. Pathway and Network Analysis of biopsy data pinpointed ST2 in the dominant pathway modulated by rejection and predicted tumor necrosis factor-α and IL-1ß as upstream activators. In total, our data indicate that alloimmune-associated pro-inflammatory cytokines increase ST2 during rejection. They also demonstrate that routine serum sST2 quantification, potentially combined with other biomarkers, should be investigated further to aid in the noninvasive diagnosis of rejection.

Cost-effectiveness of pediatric heart transplantation across a positive crossmatch for high waitlist urgency candidates.

Allosensitized children listed with a requirement for a negative prospective crossmatch have high mortality. Previously, we found that listing with the intent to accept the first suitable organ offer, regardless of the possibility of a positive crossmatch (TAKE strategy), results in a survival advantage from the time of listing compared to awaiting transplantation across a negative crossmatch (WAIT). The cost-effectiveness of these strategies is unknown. We used Markov modeling to compare cost-effectiveness between these waitlist strategies for allosensitized children listed urgently for heart transplantation. We used registry data to estimate costs and waitlist/posttransplant outcomes. We assumed patients remained in hospital after listing, no positive crossmatches for WAIT, and a base-case probability of a positive crossmatch of 47% for TAKE. Accepting the first suitable organ offer cost less ($405 904 vs. $534 035) and gained more quality-adjusted life years (3.71 vs. 2.79). In sensitivity analyses, including substitution of waitlist data from children with unacceptable antigens specified during listing, TAKE remained cost-saving or cost-effective. Our findings suggest acceptance of the first suitable organ offer for urgently listed allosensitized pediatric heart transplant candidates is cost-effective and transplantation should not be denied because of allosensitization status alone.

Comparison of listing strategies for allosensitized heart transplant candidates requiring transplant at high urgency: a decision model analysis.

Allosensitized children who require a negative prospective crossmatch have a high risk of death awaiting heart transplantation. Accepting the first suitable organ offer, regardless of the possibility of a positive crossmatch, would improve waitlist outcomes but it is unclear whether it would result in improved survival at all times after listing, including posttransplant. We created a Markov decision model to compare survival after listing with a requirement for a negative prospective donor cell crossmatch (WAIT) versus acceptance of the first suitable offer (TAKE). Model parameters were derived from registry data on status 1A (highest urgency) pediatric heart transplant listings. We assumed no possibility of a positive crossmatch in the WAIT strategy and a base-case probability of a positive crossmatch in the TAKE strategy of 47%, as estimated from cohort data. Under base-case assumptions, TAKE showed an incremental survival benefit of 1.4 years over WAIT. In multiple sensitivity analyses, including variation of the probability of a positive crossmatch from 10% to 100%, TAKE was consistently favored. While model input data were less well suited to comparing survival when awaiting transplantation across a negative virtual crossmatch, our analysis suggests that taking the first suitable organ offer under these circumstances is also favored.

The future direction of the adult heart allocation system in the United States.

Ensuring equitable and fair organ allocation is a central charge of the United Network for Organ Sharing (UNOS) as the Organ Procurement and Transplantation Network (OPTN) through its contract with the Department of Health and Human Services (DHHS). The OPTN/UNOS Board initiated a reassessment of the current allocation system. This paper describes the efforts of the OPTN/UNOS Heart Subcommittee, acting on behalf of the OPTN/UNOS Thoracic Organ Transplantation Committee, to modify the current allocation system. The Subcommittee assessed the limitations of the current three-tiered system, outcomes of patients with status exceptions, emerging ventricular assist device (VAD) population, options for improved geographic sharing and status of potentially disenfranchised groups. They analyzed waiting list and posttransplant mortality rates of a contemporary cohort of patient groups at risk, in collaboration with the Scientific Registry of Transplant Recipients to develop a proposed multi-tiered allocation scheme. This proposal provides a framework for simulation modeling to project whether candidates would have better waitlist survival in the revised allocation system, and whether posttransplant survival would remain stable. The tiers are subject to change, based on further analysis by the Heart Subcommittee and will lead to the development of a more effective and equitable heart allocation system.

Successful heart transplantation from a donor with Ullrich congenital muscular dystrophy.

Heart transplantation is the most effective therapy for children with end-stage heart disease; however, its use is limited by the number of donor organs available. This shortage may be further compounded by concerns about organ quality, leading to refusal of potential donor organ offers. We report on the successful transplantation and 5-year follow-up of a heart from a donor with Ullrich congenital muscular dystrophy (UCMD). The candidate was critically ill at the time of the transplant and the donor organ was declined repeatedly on the match run list due to concerns about organ quality, despite having normal cardiac function by echocardiography on minimal inotropic support. We believe the diagnosis of "muscular dystrophy" in the donor combined with a lack of understanding about the specifics of the diagnosis of UCMD enabled our candidate to receive a primary offer for this organ. We are unaware of any previous reports of the use of a heart from a donor with UCMD for orthotopic heart transplantation in adults or children.

A 16-year multi-institutional study of the role of age and EBV status on PTLD incidence among pediatric heart transplant recipients.

The objective was to determine the incidence and hazard for posttransplant lymphoproliferative disease (PTLD) in a study of 3170 pediatric primary heart transplants between 1993 and 2009 at 35 institutions in the Pediatric Heart Transplant Study. 147 of 151 reported malignancy events were classified as PTLD. Overall freedom from PTLD was 98.5% at 1 year, 94% at 5 years and 90% at 10 years. Freedom from PTLD was lowest in children (ages 1 to < 10 years) versus infants (<1 year) and adolescents (10 to < 18 years) with children at highest risk for PTLD with a relative risk of 2.4 compared to infants and 1.7 compared to adolescents. Positive donor EBV status was a strong risk factor for PTLD in the seronegative recipient, but risk magnitude was dependent on recipient age at the time of transplantation. Nearly 25% of EBV seronegative recipients of EBV+ donors at ages 4-7 at transplantation developed some form of PTLD. The overall risk for PTLD declined in the most recent transplant era (2001-2009, p = 0.003). These findings indicate that EBV status and the age of the recipient at the time of transplantation are important variables in the development of PTLD in the pediatric heart transplant recipient.

Total anomalous pulmonary venous connection: impact of prenatal diagnosis.

OBJECTIVES: To investigate whether prenatal screening is effective in the detection of total anomalous pulmonary venous connection (TAPVC) and to identify common prenatal features. METHODS: This was a retrospective collaborative study involving 19 pediatric cardiac centers in the UK, Ireland and Sweden. Cases with TAPVC born between January 1, 1998 and December 31, 2004, and prenatally diagnosed cases whose estimated dates of delivery were within this time frame, were identified. Cases with functionally univentricular circulation or atrial isomerism were excluded. All available data and stored images were reviewed. RESULTS: Four-hundred and twenty-four cases with TAPVC were identified prenatally or postnatally, of whom eight (1.9%) had a prenatal diagnosis of TAPVC. Median gestational age at fetal diagnosis was 26 + 6 (range, 22 + 4 to 32 + 0) weeks. Six further fetuses with TAPVC had an abnormality diagnosed on prenatal ultrasound, but not the TAPVC. This included other congenital heart defects (four cases) and isolated pleural effusion (two cases). Seventeen (4.0%) of the 422 liveborn infants had a first-degree relative with congenital heart disease; and six of 17 had a sibling with TAPVC. Two died in utero. Of the liveborn infants diagnosed prenatally with TAPVC, none required urgent intervention for pulmonary venous obstruction and all were alive and well at a median of 2.3 (range, 1.0-7.0) years after surgical repair. CONCLUSION: Prenatal diagnosis of TAPVC is infrequent using current screening methods. Where there is a family history of TAPVC, specialized fetal echocardiography at 20 and 28 weeks' gestation may be indicated.

Heart transplantation in the United States, 1999-2008.

This article features 1999-2008 trends in heart transplantation, as seen in data from the Organ Procurement and Transplantation Network (OPTN) and the Scientific Registry of Transplant Recipients (SRTR). Despite a 32% decline in actively listed candidates over the decade, there was a 20% increase from 2007 to 2008. There continues to be an increase in listed candidates diagnosed with congenital heart disease or retransplantation. The proportion of patients listed as Status 1A and 1B continues to increase, with a decrease in Status 2 listings. Waiting list mortality decreased from 2000 through 2007, but increased 18% from 2007 to 2008; despite the increase in waiting list death rates in 2008, waiting list mortality for Status 1A and Status 1B continues to decrease. Recipient numbers have varied by 10% over the past decade, with an increased proportion of transplants performed in infants and patients above 65 years of age. Despite the increase in Status 1A and Status 1B recipients at transplant, posttransplant survival has continued to improve. With the rise in infant candidates for transplantation and their high waiting list mortality, better means of supporting infants in need of transplant and allocation of organs to infant candidates is clearly needed.

Pulmonary vein stenosis: the UK, Ireland and Sweden collaborative study.

OBJECTIVE: To describe clinical features, morphology, management and outcome of pulmonary vein stenosis (PVS) in childhood. DESIGN AND SETTING: Retrospective international collaborative study involving 19 paediatric cardiology centres in the UK, Ireland and Sweden. PATIENTS: Cases of PVS presenting between 1 January 1995 and 31 December 2004 were identified. Cases where pulmonary veins connected to a morphological left atrium were included. Functionally univentricular hearts and total anomalous pulmonary venous connection were excluded. All available data and imaging were reviewed. RESULTS: 58 cases were identified. In 22 cases (38%) there was premature delivery. 46 (79%) had associated cardiac lesions; 16 (28%) had undergone previous cardiac surgery before PVS diagnosis. 16 children (28%) had a syndrome or significant extracardiac abnormality. 36 presented with unilateral disease of which 86% was on the left. Where there was adequate sequential imaging, disease progression was shown with discrete stenosis leading to diffusely small pulmonary veins. Collateral vessels often developed. 13 patients had no intervention. Initial intervention was by catheter in 17 and surgery in 28. Overall 3-year survival was 49% (95% CI 35% to 63%) with patients undergoing initial surgical intervention having greater freedom from death or re-intervention (hazard ratio 0.44, 95% CI 0.2 to 0.99, p = 0.023). CONCLUSIONS: PVS is a complex disease of uncertain cause and frequently associated with prematurity. Early intervention may be indicated to deter irreversible secondary changes.

Chronic high Epstein-Barr viral load state and risk for late-onset posttransplant lymphoproliferative disease/lymphoma in children.

Increased use of serial EBV-PCR monitoring after pediatric transplantation has led to the identification of asymptomatic patients who carry very high viral loads over prolonged periods. The significance of this high-load state is unknown. We speculated that this state may identify patients at high risk for development of late PTLD/lymphoma. We reviewed data on 71 pediatric heart recipients who had serial viral load monitoring since 1997. Chronic high-load state was defined as the presence of >16,000 genome copies/mL whole blood on > or =50% of samples over at least 6 months. Among 20 high-load carriers (eight following prior PTLD, seven with prior symptomatic EBV infection, five without previous EBV disease), 9 (45%) developed late-onset PTLD 2.5-8.4 years posttransplant (including with four Burkitt's lymphoma). Among 51 controls with low (n = 39) or absent (n = 12) loads, only 2 (4%; p < 0.001 absent/low vs. high load) developed late PTLD/lymphoma. By multivariable analysis, high-load carrier state (OR = 12.4, 95% CI 2.1-74.4) and prior history of PTLD (OR = 10.7, 95% CI 1.9-60.6) independently predicted late PTLD. A chronic high EBV-load state is not benign and is a predictor of de novo or recurrent PTLD.

IMPDH1 gene polymorphisms and association with acute rejection in renal transplant patients.

Inosine 5'-monophosphate dehydrogenase 1 (IMPDH1) catalyzes the rate-limiting step of the de novo pathway for purine synthesis and is a major target of the immunosuppressive drug mycophenolic acid (MPA). Few variants of the IMPDH1 gene have been reported. The objective of this study was to identify and characterize IMPDH1 variants to determine whether genetic variation contributes to differences in MPA response and toxicity in transplant patients. Seventeen genetic variants were identified in the IMPDH1 gene with allele frequencies ranging from 0.2 to 42.7%. In this study, 191 kidney transplant patients who received mycophenolate mofetil were genotyped for IMPDH1. Two single-nucleotide polymorphisms, rs2278293 and rs2278294, were significantly associated with the incidence of biopsy-proven acute rejection in the first year post-transplantation. Future studies of the multifactorial nature of acute rejection must consider IMPDH1 polymorphisms in MPA-treated patients.

Heart retransplantation.

Retransplants comprise only a small minority (3-4%) of heart transplants, however outcome following retransplantation is compromised. Risk factors for a poor outcome following retransplantation include retransplantation early (<6 months) after primary transplant, retransplantation for acute rejection or early allograft failure, and retransplantation in an earlier era. The incidence of rejection and infection is similar following primary transplant and retransplantation. The compromised outcomes and risk factors for a poor outcome are similar in adult and pediatric heart retransplantation. However, due to the short half-life of the transplanted heart, it is an expectation that patients transplanted in childhood may require retransplantation. Based on the data available and the opinion of the working group, indications for heart retransplantation are (i) chronic severe cardiac allograft vasculopathy with symptoms of ischemia or heart failure (should be considered) or asymptomatic moderate or severe left ventricular dysfunction (may be considered) or (ii) chronic graft dysfunction with symptoms of progressive heart failure in the absence of active rejection. Patients with graft failure due to acute rejection with hemodynamic compromise, especially <6 months post-transplant, are inappropriate candidates for retransplantation. In addition, guidelines established for primary transplant candidacy should be strictly followed.

Pediatric transplantation in the United States, 1995-2004.

This article reviews trends in pediatric solid organ transplantation over the last decade, as reflected in OPTN/SRTR data. In 2004, children younger than 18 years made up nearly 3% of the 86,378 candidates for organ transplantation and nearly 7% of the 27,031 organ transplant recipients. Children accounted for nearly 14% of the 7152 deceased organ donors. The transplant community recognizes important differences between pediatric and adult organ transplant recipients, including different etiologies of organ failure, surgical procedures that are more complex or technically challenging, effects of development on the pharmacokinetic properties of common immunosuppressants, unique immunological aspects of transplant in the developing immune system and increased susceptibility to posttransplant complications, particularly infectious diseases. For these reasons, and because of the impact of end-stage organ failure on growth and development, the transplant community has generally provided pediatric candidates with special consideration in the allocation of deceased donor organs. Outcomes following kidney, liver and heart transplantation in children often rank among the best. This article emphasizes that the prospects for solid organ transplantation in children, especially those aged 1-10 years are excellent. It also identifies themes warranting further consideration, including organ availability, adolescent survival and challenges facing pediatric transplant clinical research.

Pulmonary artery growth fails to match the increase in body surface area after the Fontan operation.

OBJECTIVE: To evaluate the growth of the pulmonary arteries after a Fontan procedure. DESIGN: Retrospective review. SETTING: Two paediatric cardiology tertiary care centres. PATIENTS: 61 children who underwent a modified Fontan operation and had angiography suitable for assessment of pulmonary artery size before the Fontan procedure and during long term follow up. An atriopulmonary connection (APC) was present in 23 patients (37.7%) and a total cavopulmonary connection (TCPC) was present in 38 (62.3%). Postoperative angiograms were performed 0.5-121 months (median 19 months) after the Fontan operation. MAIN OUTCOME MEASURE: Growth of each pulmonary artery measured just before the first branching point. The diameter was expressed as a z score with established nomograms used to standardise for body surface area. RESULTS: The mean change in the preoperative to postoperative z scores of the right pulmonary artery was -1.06 (p = 0.004). The mean change in the preoperative to postoperative z scores of the left pulmonary artery was -0.88 (p = 0.003). Changes in the preoperative to postoperative z scores were more pronounced in the patients undergoing APC than TCPC, especially for the right pulmonary artery. CONCLUSION: After the Fontan operation, growth of the pulmonary arteries often fails to match the increase in body surface area.

Pulmonary atresia with intact ventricular septum: predictors of early and medium-term outcome in a population-based study.

OBJECTIVES: Pulmonary atresia with intact ventricular septum is a form of congenital heart disease usually associated with right-heart hypoplasia, with considerable morphologic heterogeneity and often poor outlook. Ascertainment of risk factors for poor outcome is an important step if an improvement in outcome is to be achieved. METHODS: The UK and Ireland Collaborative study of Pulmonary Atresia with Intact Ventricular Septum is an ongoing population-based study of all patients born with this disease from 1991 through 1995. All available clinical, morphologic, and investigative variables were directly reviewed, and risk factor analysis was performed for poor outcome. RESULTS: One hundred eighty-three patients presented with pulmonary atresia with intact ventricular septum. Fifteen underwent no procedure, and all died. Of the remainder, 67 underwent a right ventricular outflow tract procedure (catheter or surgical), 18 underwent an outflow tract procedure with shunt, and 81 underwent a systemic-to-pulmonary shunt alone. One- and 5-year survival was 70.8% and 63.8%, respectively. Results from Cox proportional hazards model analysis showed that low birth weight (P = .024), unipartite right ventricular morphology (P = .001), and the presence of a dilated right ventricle (P < .001) were independent risk factors for death. The presence of coronary artery fistulae, right ventricular dependence, or the tricuspid valvar z score did not prove to be risk factors for death. After up to 9 years of follow-up, 29% have achieved a biventricular repair, 3% a so-called one-and-a-half ventricular repair, and 10.5% a univentricular repair, with 16.5% still having a mixed circulation (41% died). CONCLUSIONS: This population-based study has shown which features at presentation place an infant in a high-risk group. This is important information for counseling in fetal life and for surgical strategy after birth.