Rapid desensitization through immunoadsorption during cardiopulmonary bypass. A novel method to facilitate human leukocyte antigen incompatible heart transplantation.

BACKGROUND: Anti-human leukocyte antigen (HLA)-antibody production represents a major barrier to heart transplantation, limiting recipient compatibility with potential donors and increasing the risk of complications with poor waiting-list outcomes. Currently there is no consensus to when desensitization should take place, and through what mechanism, meaning that sensitized patients must wait for a compatible donor for many months, if not years. We aimed to determine if intraoperative immunoadsorption could provide a potential desensitization methodology. METHODS: Anti-HLA antibody-containing whole blood was added to a Cardiopulmonary bypass (CPB) circuit set up to mimic a 20 kg patient undergoing heart transplantation. Plasma was separated and diverted to a standalone, secondary immunoadsorption system, with antibody-depleted plasma returned to the CPB circuit. Samples for anti-HLA antibody definition were taken at baseline, when combined with the CPB prime (on bypass), and then every 20 min for the duration of treatment (total 180 min). RESULTS: A reduction in individual allele median fluorescence intensity (MFI) to below clinically relevant levels (<1000 MFI), and in the majority of cases below the lower positive detection limit (<500 MFI), even in alleles with a baseline MFI >4000 was demonstrated. Reduction occurred in all cases within 120 min, demonstrating efficacy in a time period usual for heart transplantation. Flowcytometric crossmatching of suitable pseudo-donor lymphocytes demonstrated a change from T cell and B cell positive channel shifts to negative, demonstrating a reduction in binding capacity. CONCLUSIONS: Intraoperative immunoadsorption in an ex vivo setting demonstrates clinically relevant reductions in anti-HLA antibodies within the normal timeframe for heart transplantation. This method represents a potential desensitization technique that could enable sensitized children to accept a donor organ earlier, even in the presence of donor-specific anti-HLA antibodies.

Three decades of collaboration through the Pediatric Heart Transplant Society Registry: A journey through registry data with a highlight on children with single ventricle anatomy.

BACKGROUND: The Pediatric Heart Transplant Society (PHTS) Registry was founded 30 years ago as a collaborative effort among like-minded providers of this novel life-saving technique for children with end-stage heart failure. In the intervening decades, the data from the Registry have provided invaluable knowledge to the field of pediatric heart transplantation. This report of the PHTS Registry provides a comprehensive look at the data, highlighting both the longevity of the registry and one unique aspect of the PHTS registry, allowing for exploration into children with single ventricle anatomy. METHODS: The PHTS database was queried from January 1, 1993 to December 31, 2019 to include pediatric (age < 18 years) patients listed for HT. For our analysis, we primarily analyzed patients by era. The early era was defined as children listed for HT from January 1, 1993 to December 31, 2004; middle era January 1, 2005 to December 31, 2009; and recent era January 1, 2010 to December 31, 2019. Outcomes after listing and transplant, including mortality and morbidities, are presented as unadjusted for risk, but compared across eras. RESULTS: Since 1993, 11 995 children were listed for heart transplant and entered into the PHTS Registry with 9755 listed during the study period. The majority of listings occurred within the most recent era. Waitlist survival improved over the decades as did posttransplant survival. Other notable changes over time include fewer patients experiencing allograft rejection or infection after transplant. Waitlist and posttransplant survival have changed dramatically in patients with single ventricle physiology and significantly differ by stage of single ventricle palliation. SUMMARY: Key points from this PHTS Registry summary and focus on patients with single ventricle congenital heart disease in particular, include the changing landscape of candidates and recipients awaiting heart transplant. There is clear improvement in waitlist and transplant outcomes for children with both cardiomyopathy and congenital heart disease alike.

Pathogen and human NDPK-proteins promote AML cell survival via monocyte NLRP3-inflammasome activation.

A history of infection has been linked with increased risk of acute myeloid leukaemia (AML) and related myelodysplastic syndromes (MDS). Furthermore, AML and MDS patients suffer frequent infections because of disease-related impaired immunity. However, the role of infections in the development and progression of AML and MDS remains poorly understood. We and others previously demonstrated that the human nucleoside diphosphate kinase (NDPK) NM23-H1 protein promotes AML blast cell survival by inducing secretion of IL-1ß from accessory cells. NDPKs are an evolutionary highly conserved protein family and pathogenic bacteria secrete NDPKs that regulate virulence and host-pathogen interactions. Here, we demonstrate the presence of IgM antibodies against a broad range of pathogen NDPKs and more selective IgG antibody activity against pathogen NDPKs in the blood of AML patients and normal donors, demonstrating that in vivo exposure to NDPKs likely occurs. We also show that pathogen derived NDPK-proteins faithfully mimic the catalytically independent pro-survival activity of NM23-H1 against primary AML cells. Flow cytometry identified that pathogen and human NDPKs selectively bind to monocytes in peripheral blood. We therefore used vitamin D3 differentiated monocytes from wild type and genetically modified THP1 cells as a model to demonstrate that NDPK-mediated IL-1ß secretion by monocytes is NLRP3-inflammasome and caspase 1 dependent, but independent of TLR4 signaling. Monocyte stimulation by NDPKs also resulted in activation of NF-κB and IRF pathways but did not include the formation of pyroptosomes or result in pyroptotic cell death which are pivotal features of canonical NLRP3 inflammasome activation. In the context of the growing importance of the NLRP3 inflammasome and IL-1ß in AML and MDS, our findings now implicate pathogen NDPKs in the pathogenesis of these diseases.

Lung transplantation in an 18-month-old with donor specific antibodies - The use of intraoperative, targeted plasma exchange.

BACKGROUND: Sensitised patients undergoing Human Leukocyte Antigen-incompatible transplantation are at increased risk of hyperacute rejection and may be predisposed to antibody-mediated rejection, chronic lung allograft dysfunction and higher mortality. CASE: We present a case of primary lung transplantation in the setting of late identification of donor specific antibodies treated with intraoperative target plasma exchange. The patient was treated with fresh human plasma to a final volume of 1.5 times the patient's systemic circulation. From a pre-transplant mean fluorescence intensity of 5002, donor-specific antibodies were undetectable following plasma exchange on single antigen bead assay. CONCLUSIONS: This method represents a potential desensitisation technique for use in the intraoperative period.

Clinical approach to antibody-mediated rejection from the pediatric heart transplant society.

OBJECTIVE: 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.

Exploring the Possible Impact of Echocardiographic Diastolic Function Parameters on Outcome in Paediatric Dilated Cardiomyopathy.

Diastolic dysfunction is an important determinant for prognosis and survival in several paediatric heart diseases. We aimed to explore its possible impact on outcome in children with dilated cardiomyopathy. From 2006 to 2016, children less than 18 years old with dilated cardiomyopathy were retrospectively enrolled. Echocardiographic diastolic function parameters and child outcomes were analysed. Of 43 children aged 0.2 to 16.1 years old referred with dilated cardiomyopathy, 8 patients required cardiac transplant or mechanical assist devices (18%), 24 had persistently abnormal left ventricular function and/or dilatation (56%) and 11 patients recovered (26%). There was no significant difference in mitral velocities on Tissue Doppler Imaging, mitral valve inflow velocities, isovolumic relaxation time, left atrial area z-score and mitral lateral E/e' ratios between patients with recovery and patients with disease progression or persistently abnormal ventricular function and/or dilation. This is the first study on childhood dilated cardiomyopathy to address individual echocardiographic diastolic function parameters and their association to recovery. In this study, echocardiographic parameters for diastolic function did not predict recovery.

Cardiac care of children with dystrophinopathy and females carrying DMD-gene variations.

OBJECTIVE: We provide succinct, evidence-based and/or consensus-based best practice guidance for the cardiac care of children living with Duchenne muscular dystrophy (DMD) as well as recommendations for screening and management of female carriers of mutations in the DMD-gene. METHODS: Initiated by an expert working group of UK-based cardiologists, neuromuscular clinicians and DMD-patient representatives, draft guidelines were created based on published evidence, current practice and expert opinion. After wider consultation with UK-cardiologists, consensus was reached on these best-practice recommendations for cardiac care in DMD. RESULTS: The resulting recommendations are presented in the form of a succinct care pathway flow chart with brief justification. The guidance signposts evidence on which they are based and acknowledges where there have been differences in opinion. Guidelines for cardiac care of patients with more advanced cardiac dystrophinopathy at any age have also been considered, based on the previous published work of Quinlivan et al and are presented here in a similar format. The recommendations have been endorsed by the British Cardiovascular Society. CONCLUSION: These guidelines provide succinct, reasoned recommendations for all those managing paediatric patients with early or advanced stages of cardiomyopathy as well as females with cardiac dystrophinopathy. The hope is that this will result in more uniform delivery of high standards of care for children with cardiac dystrophinopathy, so improving heart health into adulthood through timely earlier interventions across the UK.

Pediatric heart transplantation following donation after circulatory death, distant procurement, and ex-situ perfusion.

BACKGROUND: Limited availability of suitable donor hearts remains a challenge to pediatric heart transplantation, contributing to waitlist mortality. Controlled donation after circulatory death (DCD) has demonstrated success in adults. Early series of pediatric DCD heart transplantation using cold storage alone reported significant early mortality. We report a collaboration between 2 centers in the United Kingdom, combining expertise in adult DCD organ retrieval and pediatric transplantation. METHODS: This retrospective series comprises 6 children (4 male, all >20 kg) undergoing DCD heart transplantation at Great Ormond Street Hospital between 1 February and 30 September 2020, following retrieval with direct procurement and perfusion using portable normothermic machine perfusion by the Royal Papworth Hospital service. Baseline characteristics and 1-year follow-up were compared to 9 children who underwent donation after brain death (DBD) transplants contemporaneously. RESULTS: Mean DCD donor age was 24.67 years and mean DCD recipient age was 13.83 years. Mean functional warm ischemic time was 28.5 minutes and ex-situ heart perfusion time was 280 minutes. Median ICU and hospital stay were 9 and 17 days, respectively. All children survived to 1-year post-transplant. Survival and ICU and hospital stay were similar between the DCD and DBD cohorts. Performing DCD transplants resulted in a 66.7% increase in transplants for children >20 kg at GOSH during the study. CONCLUSIONS: This series demonstrates that DCD heart transplant can be performed safely with excellent short-term survival in children. Although the cohort is small, there was no significant difference in major outcomes compared to a DBD cohort.

Post-transplant lymphoproliferative disorder presenting as supraglottitis following pediatric heart transplantation treated with EBV-specific cytotoxic T-lymphocytes.

We present the case of a 4 year-old boy post heart transplantation who presented with signs and symptoms of critical airway obstruction and was initially diagnosed with infective supraglottitis. Following re-presentation and biopsy, this was confirmed as post-transplant lymphoproliferative disorder (PTLD) in an unusual site; laryngeal PTLD is rare. The patient failed standard therapy and ultimately was successfully treated with EBV-specific cytotoxic T lymphocytes (CTL). This case describes a rare presentation of PTLD which required a novel treatment approach including elective tracheostomy prior to CTL therapy. The treatment was successful and the patient was decannulated prior to discharge following 4 negative biopsies, the most recent 6 months following treatment completion. The case also highlights the importance of extra-vigilance in the post-transplant population and of a collaborative approach between multiple specialties across two separate countries including the transplant center and the referral center.

Learning networks in pediatric heart failure and transplantation.

BACKGROUND: Learning networks have emerged in medicine as a novel organizational structure that contains elements of quality improvement, education, and research with the goal of effecting rapid improvements in clinical care. In this article, the concept of a learning network is defined and highlighted in the field of pediatric heart failure and transplantation. METHODS: Learning networks are defined, with particular attention paid to the recent creation of the Advanced Cardiac Therapies Improving Outcomes Network (ACTION) for children with heart failure and those being supported with ventricular assist devices (VAD). RESULTS: The mission, goals, and organizational structure of ACTION are described, and recent initiatives promoted by ACTION are highlighted, such as stroke reduction initiatives, practice harmonization protocols, and use of ACTION data to support the recent US Food and Drug Administration approval of newer VAD for pediatric patients. CONCLUSIONS: The learning network, exemplified by ACTION, is distinguished from traditional clinical research collaboratives by contributions in research, quality improvement, patient-reported outcomes, and education, and serves as an effective vehicle to drive clinical improvement in the care of children with advanced heart failure.

Intraoperative anti-A/B immunoadsorption is associated with significantly reduced blood product utilization with similar outcomes in pediatric ABO-incompatible heart transplantation.

BACKGROUND: Intraoperative anti-A/B immunoadsorption (ABO-IA) was recently introduced for ABO-incompatible heart transplantation. Here we report the first case series of patients transplanted with ABO-IA, and compare outcomes with those undergoing plasma exchange facilitated ABO-incompatible heart transplantation (ABO-PE). METHODS: Data were retrospectively analysed on all ABO-incompatible heart transplants undertaken at a single centre between January 1, 2000 and June 1, 2020. Data included all routine laboratory tests, demographics and pre-operative characteristics, intraoperative details and post-operative outcomes. Primary outcome measures were volume of blood product transfusions, maximum post-transplant isohaemagglutinin titres, occurrence of rejection and graft survival. Secondary outcome measures were length of intensive care and hospital stay. Demographic and survival data were also obtained for ABO-compatible transplants during the same time period for comparison. RESULTS: Thirty-seven patients underwent ABO-incompatible heart transplantation, with 27 (73%) using ABO-PE and 10 (27%) using ABO-IA. ABO-IA patients were significantly older than ABO-PE patients (p < 0.001) and the total volume of blood products transfused during the hospital admission was significantly lower (164 [126-212] ml/kg vs 323 [268-379] ml/kg, p < 0.001). No significant differences were noted between methods in either pre or post-transplant maximum isohaemagglutinin titres, incidence of rejection, length of intensive care or total hospital stay. Survival comparison showed no significant difference between antibody reduction methods, or indeed ABO-compatible transplants (p = 0.6). CONCLUSIONS: This novel technique appears to allow a significantly older population than typical to undergo ABO-incompatible heart transplantation, as well as significantly reducing blood product utilization. Furthermore, intraoperative anti-A/B immunoadsorption does not demonstrate increased early post-transplant isohaemagglutinin accumulation or rates of rejection compared to ABO-PE. Early survival is equivalent between ABO-IA, ABO-PE and ABO-compatible heart transplantation.

Cell-Free DNA in Pediatric Solid Organ Transplantation Using a New Detection Method of Separating Donor-Derived from Recipient Cell-Free DNA.

BACKGROUND: The use of cell-free DNA (cfDNA) as a noninvasive biomarker to detect allograft damage is expanding rapidly. However, quantifying the low fraction of donor-derived cfDNA (ddcfDNA) is challenging and requires a highly sensitive technique. ddcfDNA detection through unique donor single nucleotide polymorphisms (SNPs) is a recent new approach, however there are limited data in pediatric solid organ transplant (SOT) recipients. METHODS: We developed an assay using a combination of 61 SNPs to quantify the ddcfDNA accurately using a custom R script to model for both the patient and donor genotypes requiring only a single sample from the allograft recipient. Performance of the assay was validated using genomic DNA (gDNA), cfDNA and donor samples where available. RESULTS: The R "genotype-free" method gave results comparable to when using the known donor genotype. applicable to both related and unrelated pairs and can reliably measure ddcfDNA (limit of blank, below 0.12%; limit of detection, above 0.25%; limit of quantification 0.5% resulting in 84% accuracy). 159 pediatric SOT recipients (kidney, heart, and lung) were tested without the need for donor genotyping. Serial sampling was obtained from 82 patients. CONCLUSION: We have developed and validated a new assay to measure the fraction of ddcfDNA in the plasma of pediatric SOT recipients. Our method can be applicable in any donor-recipient pair without the need for donor genotyping and can provide results in 48 h at a low cost. Additional prospective studies are required to demonstrate its clinical validity in a large cohort of pediatric SOT recipients.

The impact of home hemodialysis in children with severe cardiac failure.

When faced with patients with deteriorating cardiac disease, nephrologists tend to accept that heart disease is unmodifiable, accepting mediocrity and opting for stabilization. Likewise cardiac patients with persistent renal failure are presented with a poor renal prognosis and prepared for renal transplantation. We present three dialysis dependent children with moderate-to-severe cardiac failure in whom home hemodialysis normalized the cardiac function and restored renal function. These cases highlight the medical benefits of home hemodialysis in severe cardio-renal cases but not without acknowledgement of the resource, commitment, and safety challenges that accompanies them.

Surveillance for cardiac allograft vasculopathy: Practice variations among 50 pediatric heart transplant centers.

BACKGROUND: Coronary allograft vasculopathy (CAV) is a leading cause of mortality after heart transplantation (HT) in children. Variation in CAV screening practices may impact detection rates and patient outcomes. METHODS: Among 50 Pediatric Heart Transplant Society (PHTS) sites from 2001 to 2016, coronary evaluations were classified as angiography or non-invasive testing, and angiograms were designated as routine or symptom based. CAV detection rates stratified by routine vs symptom-based angiograms were calculated. Freedom from CAV and mortality after CAV diagnosis, stratified by study indication, were calculated. RESULTS: A total of 3,442 children had 13,768 coronary evaluations; of these, 97% (n = 13,012) were for routine surveillance, and only 3% (n = 333) were for cause. Over the study period, CAV was detected in 472 patients (14%). Whereas 58% (n = 29) of PHTS sites evaluate by angiography alone, 42% reported supplementing with a non-invasive test, although only 423 non-invasive studies were reported. Angiographic detection of CAV was higher for symptom-based testing than for routine testing (29% vs 4%, p < 0.0001), although routine testing identified a majority of cases (88%; n = 414). The 10-year freedom from CAV was 77% overall. Once CAV is detected, 5-year graft survival was 58%, with lower survival for patients diagnosed after symptoms angiogram than after routine angiogram (30% vs 62%; p < 0.0001). CONCLUSIONS: Development of a robust model for CAV risk should allow low-risk patients to undergo less frequent invasive angiography without adverse impact on CAV detection rates or outcomes.

Lessons of the month 3: ST-elevation myocardial infarction and left ventricular thrombus formation: an arterial thrombotic complication of severe COVID-19 infection.

We describe a case of an 82-year-old man who developed an anterior ST-elevation myocardial infarction (STEMI) and left ventricular thrombus while an inpatient following a diagnosis of severe COVID-19 infection (SARS-CoV-2). His D-dimer was significantly elevated at 12,525 ng/mL (normal range <243). He unfortunately died despite management with thrombolysis, warfarin and non-invasive ventilation. This case provides an example of a likely arterial thrombotic complication of severe COVID-19 infection. Clinicians should be aware of this possibility in such patients, with a severely prothrombotic state as a possible underlying aetiology. Further research is required to establish any causative link, pathophysiological mechanisms and whether modification to existing venous thromboembolism prophylaxis strategies may also reduce arterial thrombotic complications of severe COVID-19 infection.

The complication rate of intravascular ultrasound (IVUS) in a multicenter pediatric heart transplant population: A study of the international pediatric IVUS consortium.

BACKGROUND: Our purpose was to determine the complication rate from intravascular ultrasound (IVUS) in a large, multicenter cohort of pediatric heart transplant (PHT) patients. METHODS: We retrospectively reviewed all PHT who underwent IVUS at 5 institutions (2006-2014). Rates of major and minor complications were calculated. All adverse events (AE) were graded from 1 to 5 using a previously published AE severity scale. RESULTS: There were 1380 catheterizations in 505 patients and 32 AE (2.3%); 9 major (0.6%) and 23 AE (1.7%). The major AE attributed to IVUS were all coronary artery vasospasm (7). Major and minor AE rates directly related to IVUS were 0.5% and 0.7%, respectively. Minor AE possibly attributable to IVUS included excessive fluoroscopy (3) and transient ST segment changes (7). Of AE related to IVUS, only 3 were of moderate severity. The rest were ≤ minor in severity. There were no reports of coronary artery dissection or death. CONCLUSION: Most AE during routine PHT coronary evaluation with IVUS were minor and not directly related to the use of IVUS. The number of coronary related AE was similar to a registry-based report of coronary angiography alone. Efforts to minimize IVUS-related complications should be focused on preventing coronary artery vasospasm.

The National Institute of Allergy and Infectious Diseases and Scientific Societies Meeting on Research Training Efforts: Summary of Recommendations to Address Early-Stage Investigators.

A group of representatives from scientific societies and organizations met to discuss possible solutions for funding and retaining early-stage investigators in research that supports the National Institute of Allergy and Infectious Diseases research agenda. This article describes perspectives voiced during that meeting.

Cardiorespiratory Progression Over 5 Years and Role of Corticosteroids in Duchenne Muscular Dystrophy: A Single-Site Retrospective Longitudinal Study.

BACKGROUND: Corticosteroids (CSs) have prolonged survival and respiratory function in boys with Duchenne muscular dystrophy (DMD) when compared with CSs-naïve boys. RESEARCH QUESTION: The differential impact of frequently used CSs and their regimens on long-term (> 5 years) cardiorespiratory progression in children with DMD is unknown. STUDY DESIGN AND METHODS: This was a retrospective longitudinal study including children with DMD followed at Dubowitz Neuromuscular Centre, Great Ormond Street Hospital London, England, from May 2000 to June 2017. Patients enrolled in any interventional clinical trials were excluded. We collected patients' anthropometrics and respiratory (FVC, FVC % predicted and absolute FVC, and noninvasive ventilation requirement [NIV]) and cardiac (left ventricular shortening function [LVFS%]) function. CSs-naïve patients had never received CSs. Patients who were treated with CSs took either deflazacort or prednisolone, daily or intermittently (10 days on/10 days off) for > 1 month. Average longitudinal models were fitted for yearly respiratory (FVC % predicted) and cardiac (LVFS%) progression. A time-to-event analysis to FVC % predicted < 50%, NIV start, and cardiomyopathy (LVFS% < 28%) was performed in CS-treated (daily and intermittent) vs CS-naïve patients. RESULTS: There were 270 patients, with a mean age at baseline of 6.2 ± 2.3 years. The median follow-up time was 5.6 ± 3.5 years. At baseline, 263 patients were ambulant. Sixty-six patients were treated with CSs daily, 182 patients underwent CSs intermittent > 60% treatment, and 22 were CS-naïve patients. Yearly FVC % predicted declined similarly from 9 years (5.9% and 6.9% per year, respectively; P = .27) in the CSs-daily and CSs-intermittent groups. The CSs-daily group declined from a higher FVC % predicted than the CSs-intermittent group (P < .05), and both reached FVC % predicted < 50% and NIV requirement at a similar age, > 2 years later than the CS-naïve group. LVFS% declined by 0.53% per year in the CSs-treated group irrespective of the CSs regimen, significantly slower (P < .01) than the CSs-naïve group progressing by 1.17% per year. The age at cardiomyopathy was 16.6 years in the CSs-treated group (P < .05) irrespective of regimen and 13.9 years in the CSs-naïve group. INTERPRETATION: CSs irrespective of the regimen significantly improved respiratory function and delayed NIV requirement and cardiomyopathy.