Emerging science in paediatric heart transplantation: donor allocation, biomarkers, and the quest for evidence-based medicine

Partial Heart Transplantation: Early Experience With Pediatric Heart Valve Replacements That Grow

Heart valve replacement in children is fraught with long-term morbidity and mortality rates, largely because conventional implants lack the capacity to grow with the child. Partial heart transplantation presents a potential solution by transplanting only specific segments of a donor heart, thereby providing a living and growing heart valve implant. This approach harnesses the full spectrum of cardiac tissues, which, when freshly procured and supported by immunosuppression, can integrate as functional and potentially growth-capable tissue. This state-of-the-art review discusses the history and development of partial heart transplantation, its indications, recent clinical experiences, regulation, and future directions.

Perceptions of pediatric deceased donor consent: A survey of organ procurement organizations

BACKGROUND

Children awaiting transplantation face a high risk of waitlist mortality due to a shortage of pediatric organ donors. Pediatric donation consent rates vary across Organ Procurement Organizations (OPOs), suggesting that some OPOs might utilize more effective pediatric-focused donor recruitment techniques than others. An online survey of 193 donation requestor staff sheds light on the strategies that OPO staff utilize when approaching potential pediatric deceased organ donors.

METHODS

In collaboration with the Association of Organ Procurement Organizations, the research team contacted the executive directors and medical directors of all 57 of the OPOs in the US. Of these, 51 OPOs agreed to participate, and 47 provided contact information for donation requestor staff. Of the 379 staff invited to participate in the survey, 193 provided complete responses.

RESULTS

Respondents indicated more comfort approaching adult donors than pediatric donors, and they endorsed approach techniques that were interpersonal and emotional rather than professional and informative. Respondents were accurate in their perceptions about which donor characteristics are associated with consent. However, respondents from OPOs with high consent rates (according to data from the Scientific Registry of Transplant Recipients), and those from OPOs with low consent rates were very similar in terms of demographics, training, experience, and reported techniques.

CONCLUSIONS

Additional research is needed to better determine why some OPOs have higher consent rates than others and whether the factors that lead to high consent rates in high-performing OPOs can be successful when implemented by lower-performing OPOs.

Predictors of Deceased Organ Donation in the Pediatric Population

BACKGROUND

A shortage of donor organs represents the major barrier to the success of solid organ transplantation. This is especially true in the pediatric population for which the number of organ donors has decreased over time. With this study, we aimed to assess the factors associated with deceased organ donor consent in the pediatric population and determine the variability in consent rates across organ procurement organizations (OPOs).

METHODS

All eligible pediatric deaths were identified from the Scientific Registry of Transplant Recipients (2008-2019). The rate of organ donor consent was determined, and multivariable logistic regression was used to assess the factors independently associated with successful donor recruitment. The probability of donor consent was determined for each OPO after adjusting for patient demographics.

RESULTS

A total of 11 829 eligible pediatric deaths were approached to request consent for organ donation. Consent was successful in 8816 (74.5%) subjects. Consent rates are lower in the pediatric population compared with young adults and are directly related to patient age such that eligible infant deaths have the lowest rate of successful donor consent. There is significant variability in donor consent rates across OPOs, independent of population demographic differences.

CONCLUSIONS

OPO is predictive of pediatric deceased organ donor consent independent of demographic differences, with some regions having consistently higher consent rates than others. Sharing best practices for pediatric deceased donor recruitment may be a strategy to increase organ availability in the pediatric population.

Pediatric heart transplantation: how to manage problems affecting long-term outcomes?

Since the initial International Society of Heart Lung Transplantation registry was published in 1982, the number of pediatric heart transplantations has increased markedly, reaching a steady state of 500-550 transplantation annually and occupying up to 10% of total heart transplantations. Heart transplantation is considered an established therapeutic option for patients with end-stage heart disease. The long-term outcomes of pediatric heart transplantations were comparable to those of adults. Issues affecting long-term outcomes include acute cellular rejection, antibody-mediated rejection, cardiac allograft vasculopathy, infection, prolonged renal dysfunction, and malignancies such as posttransplant lymphoproliferative disorder. This article focuses on medical issues before pediatric heart transplantation, according to the Korean Network of Organ Sharing registry and as well as major problems such as graft rejection and cardiac allograft vasculopathy. To reduce graft failure rate and improve long-term outcomes, meticulous monitoring for rejection and medication compliance are also important, especially in adolescents.

Variability in donor selection among pediatric heart transplant providers: Results from an international survey

There is considerable variability in donor acceptance practices among adult heart transplant providers; however, pediatric data are lacking. The aim of this study was to assess donor acceptance practices among pediatric heart transplant professionals. The authors generated a survey to investigate clinicians' donor acceptance practices. This survey was distributed to all members of the ISHLT Pediatric Council in April 2018. A total of 130 providers responded from 17 different countries. There was a wide range of acceptable criteria for potential donors. These included optimal donor-to-recipient weight ratio (lower limit: 50%-150%, upper limit: 120%-350%), maximum donor age (25-75 years), and minimum acceptable left ventricular EF (30%-60%). Non-US centers demonstrated less restrictive donor selection criteria and were willing to accept older donors (50 vs 35 years, P < 0.001), greater size discrepancy (upper limit weight ratio 250% vs 200%, P = 0.009), and donors with a lower EF (45% vs 50%, P < 0.001). Recipient factors were most influential in the decision to accept marginal donors including recipients requiring ECMO support, ventilator support, and highly sensitized patients with a negative XM. However, programmatic factors impacted the decision to decline marginal donors including recent programmatic mortalities and concerns for programmatic restrictions from regulatory bodies. There is significant variation in donor acceptance practices among pediatric heart transplant professionals. Standardization of donor acceptance practices through the development of a consensus statement may help to improve donor utilization and reduce waitlist mortality.

Precision monitoring of immunotherapies in solid organ and hematopoietic stem cell transplantation

Pharmacological immunotherapies are a key component of post-transplant therapy in solid-organ and hematopoietic stem cell transplantation. In current clinical practice, immunotherapies largely follow a one-size fits all approach, leaving a large portion of transplant recipients either over- or under-immunosuppressed, and consequently at risk of infections or immune-mediated complications. Our goal here is to review recent and rapid advances in precision and genomic medicine approaches to monitoring of post-transplant immunotherapies. We will discuss recent advances in precision measurements of pharmacological immunosuppression, measurements of the plasma and gut microbiome, strategies to monitor for allograft injury and post-transplant malignancies via circulating cell-free DNA, and comprehensive measurements of the B and T cell immune cell repertoire.

Neonatal tolerance: applicability to solid organ transplantation

PURPOSE OF REVIEW

The phenomenon of tolerance induced during immunologic immaturity has been explored for more than 60 years. Although direct application of neonatal tolerance to organ transplantation in human newborns is limited, exploiting discrete components of neonatal immaturity is proving fruitful.

RECENT FINDINGS

Two reviews comprehensively considered features and impact of neonatal tolerance as described in the 1950s. Recent imaging studies in mice demonstrated complex functional interactions especially of donor regulatory T cells with emerging neonatal immune components. The propensity of the developing immune system toward tolerance rather than immunity to non-self carbohydrates in ABO-incompatible transplantation was shown using glyconanotechnology tools to have exquisite specificity, and is associated with age-related changes in the B-cell compartment and complement components. Discarded infant thymus was found to be a source of abundant therapeutic regulatory T cells. Erythroid precursors transiently present in newborn mice and humans were shown to have immunosuppressive properties that may contribute to a tolerogenic environment.

SUMMARY

Neonatal tolerance has profound impact on immunology well beyond transplantation. Continued exploration of mechanisms underlying the malleability of the developing immune system and exploitation of particular components are leading to tools for immune manipulation beyond infancy.