Early outcomes for low-risk pediatric heart transplant recipients and steroid avoidance: A multicenter cohort study (Clinical Trials in Organ Transplantation in Children - CTOTC-04)

Pediatric heart transplantation: Looking forward after five decades of learning

Heart transplantation has become the standard of care for pediatric patients with end-stage heart disease throughout the world. Since the first transplant was performed in 1967, the number of transplants has grown dramatically with 13 449 pediatric heart transplants being reported to The International Society of Heart and Lung Transplant (ISHLT) between January 1992 and June 30, 2018. Outcomes have consistently improved over the last few decades, specifically short-term outcomes. Most recent survival data demonstrate that recipients who survive to 1-year post-transplant have excellent long-term survival with more than 60% of those who were transplanted as infants being alive 25 years later. Nonetheless, the rates of graft loss beyond the first year have remained relatively constant over time; driven primarily by our poor understanding and lack of treatments for chronic allograft vasculopathy (CAV). Acute rejection, CAV, graft failure, and infection continue to be the major causes of death within the first 5 years post-transplant. In addition, renal dysfunction, malignancy, and the need for re-transplantation remain as significant issues that require close follow-up. Looking forward, key challenges include improving donor utilization rates (including donation after cardiac death (DCD) and the use of ex vivo perfusion devices), the development of non-invasive biomarkers for rejection, efforts to mitigate the long-term effects of immunosuppression, and prevention of CAV. It is not possible to cover the entire evolution of pediatric heart transplantation over the last five decades, but in this review, we hope to touch on key observations, lessons learned, and practice changes that have advanced the field, as well as glance ahead to the next decade.

Medium-term Outcomes in Pediatric Heart Transplant Recipients Managed Using a Steroid Avoidance Immune Suppression Protocol

BACKGROUND

Short-term outcomes using steroid avoidance immune suppression are encouraging in pediatric heart transplant (HT) recipients at low risk of antibody-mediated rejection. We assessed medium-term outcomes in pediatric HT recipients initiated on a steroid avoidance protocol at our institution using surveillance biopsies.

METHODS

All primary HT recipients during 2006-2020 who did not have a donor-specific antibody were eligible for immune suppression consisting of 5-d Thymoglobulin/steroid induction followed by a tacrolimus-based, steroid-free regimen. We assessed freedom from graft failure (death or retransplant), acute rejection, posttransplant lymphoproliferative disease, and cardiac allograft vasculopathy.

RESULTS

Overall, 150 of 181 primary HT recipients were eligible for steroid avoidance regimen. Their median age was 8.7 y, 41% had congenital heart disease, 23% were sensitized, and 35% were on a mechanical support. The median follow-up was 6.1 y. Eleven patients (8%) were on maintenance steroids at discharge and 13% at 1 y. Graft survival was 94% at 1 y and 87% at 5 y. Freedom from rejection was 73% at 1 y and 64% at 5 y. Freedom from posttransplant lymphoproliferative disease was 96% at 1 y and 95% at 5 y. Freedom from moderate cardiac allograft vasculopathy was 94% at 5 y. Eight patients developed diabetes. Estimated glomerular filtration rate was <60 mL/min/1.73 m 2 in 5% of the cohort at 5 y.

CONCLUSIONS

Pediatric HT recipients at low risk of antibody-mediated rejection have excellent medium-term survival and relatively low incidence of posttransplant morbidities when managed using a steroid avoidance immune suppression protocol.

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.

Trends in Contemporary Use of Ventricular Assist Devices in Children Awaiting Heart Transplantation and Their Outcomes by Race/Ethnicity

This retrospective study included children aged ≤18 years who had durable ventricular assist devices (VADs) as a bridge to transplantation from the United Network Organ Sharing (UNOS) database between 2011 and 2020. We evaluated 90 day waitlist mortality and 1 year posttransplant mortality after VAD implantation in children stratified by race/ethnicity: Black, White, and Others. The VAD was used in a higher proportion of Black children listed for heart transplantation (HT) (26%) versus Other (25%) versus White (22%); p < 0.01. Black children had Medicaid health insurance coverage (67%) predominantly at the time of listing for HT. There was no significant overall difference in waitlist survival among the three groups supported with VAD at the time of listing (log-rank p = 0.4). On the other hand, the 90 day waitlist mortality after the VAD implantation at listing and while listed was the lowest among Black (6%) compared with White (13%) and Other (14%) ( p < 0.01). The multivariate regression analysis showed that Other race (hazard ratio [HR], 2.29; p < 0.01), Black race (HR, 2.13; p < 0.01), use of mechanical ventilation (HR, 1.72; p = 0.01), and Medicaid insurance (HR, 1.54; p = 0.04) were independently associated with increased 1 year posttransplant mortality. In conclusion, Black children had more access to durable VAD support than White children. The 90 day waitlist mortality was significantly lower in Black children compared with White and Other after VAD implantation. However, Black and Other racial/ethnic children with VAD at transplant had higher 1 year posttransplant mortality than White children. Future studies to elucidate the reasons for these disparities are needed.

Racial and socioeconomic disparities in pediatric heart transplant outcomes in the era of anti-thymocyte globulin induction

BACKGROUND

Black race is associated with worse outcomes across solid organ transplantation. Augmenting immunosuppression through antithymocyte globulin (ATG) induction may mitigate organ rejection and graft loss. We investigated whether racial and socioeconomic outcome disparities persist in children receiving ATG induction.

METHODS

Using the Pediatric Heart Transplant Society registry, we compared outcomes in Black and White children who underwent heart transplant with ATG induction between 2000 and 2020. The primary outcomes of treated rejection, rejection with hemodynamic compromise (HC), and graft loss (death or re-transplant). We explored the association of these outcomes with race and socioeconomic disparity, assessed using a neighborhood deprivation index [NDI] score at 1-year post-transplant (high NDI score implies more socioeconomic disadvantage).

RESULTS

The study cohort included 1,719 ATG-induced pediatric heart transplant recipients (22% Black, 78% White). There was no difference in first year treated rejection (Black 24.5%, White 28.1%, p = 0.2). During 10 year follow up, the risk of treated rejection was similar; however, Black recipients were at higher risk of HC rejection (p = 0.009) and graft loss (p = 0.02). Black recipients had a higher mean NDI score (p < 0.001). Graft loss conditional on 1-year survival was associated with high NDI score in both White and Black recipients (p < 0.0001). In a multivariable Cox model, both high NDI score (HR 1.97, 95% CI 1.23-3.17) and Black race (HR 2.22, 95% CI 1.40-3.53) were associated with graft loss.

CONCLUSION

Black race and socioeconomic disadvantage remain associated with late HC rejection and graft loss in children with ATG induction. These disparities represent important opportunities to improve long term transplant outcomes.

Relationship between donor fraction cell-free DNA and clinical rejection in heart transplantation

BACKGROUND

Clinical rejection (CR) defined as decision to treat clinically suspected rejection with change in immunotherapy based on clinical presentation with or without diagnostic biopsy findings is an important part of care in heart transplantation. We sought to assess the utility of donor fraction cell-free DNA (DF cfDNA) in CR and the utility of serial DF cfDNA in CR patients in predicting outcomes of clinical interest.

METHODS

Patients with heart transplantation were enrolled in two sequential, multi-center, prospective observational studies. Blood samples were collected for surveillance or clinical events. Clinicians were blinded to the results of DF cfDNA.

RESULTS

A total of 835 samples from 269 subjects (57% pediatric) were included for this analysis, including 28 samples associated with CR were analyzed. Median DF cfDNA was 0.43 (IQR 0.15, 1.36)% for CR and 0.10 (IQR 0.07, 0.16)% for healthy controls (p < .0001). At cutoff value of 0.13%, the area under curve (AUC) was 0.82, sensitivity of 0.86, specificity of 0.67, and negative predictive value of 0.99. There was serial decline in DF cfDNA post-therapy, however, those with cardiovascular events (cardiac arrest, need for mechanical support or death) showed significantly higher levels of DF cfDNA on Day 0 (2.11 vs 0.31%) and Day 14 (0.51 vs 0.22%) compared to those who did not have such an event (p < .0001).

CONCLUSION

DF cfDNA has excellent agreement with clinical rejection and, importantly, serial measurement of DF cfDNA predict clinically significant outcomes post treatment for rejection in these patients.

Heart Transplantation in Children With Down Syndrome

Background

Children with Down syndrome (DS) have a high risk of cardiac disease that may prompt consideration for heart transplantation (HTx). However, transplantation in patients with DS is rarely reported. This project aimed to collect and describe waitlist and post– HTx outcomes in children with DS.

Methods and Results

This is a retrospective case series of children with DS listed for HTx. Pediatric HTx centers were identified by their participation in 2 international registries with centers reporting HTx in a patient with DS providing detailed demographic, medical, surgical, and posttransplant outcome data for analysis. A total of 26 patients with DS were listed for HTx from 1992 to 2020 (median age, 8.5 years; 46% male). High‐risk or failed repair of congenital heart disease was the most common indication for transplant (N=18, 69%). A total of 23 (88%) patients survived to transplant. All transplanted patients survived to hospital discharge with a median posttransplant length of stay of 22 days. At a median posttransplant follow‐up of 2.8 years, 20 (87%) patients were alive, 2 (9%) developed posttransplant lymphoproliferative disorder, and 8 (35%) were hospitalized for infection within the first year. Waitlist and posttransplant outcomes were similar in patients with and without DS (P=non‐significant for all).

Conclusions

Waitlist and post‐HTx outcomes in children with DS selected for transplant listing are comparable to pediatric HTx recipients overall. Given acceptable outcomes, the presence of DS alone should not be considered an absolute contraindication to HTx.

Emergency Department Management of Pediatric Heart Transplant Recipients: Unique Immunologic and Hemodynamic Challenges

BACKGROUND

Since the first heart transplant in 1967, there has been significant progress in this field of cardiac transplantation. Approximately 600 pediatric heart transplants are performed every year worldwide. With the increasing number of pediatric heart transplant patients, and given the few tertiary care pediatric transplant centers, adult and pediatric emergency department (ED) providers are increasingly engaged in the care of pediatric heart transplant recipients in the ED.

OBJECTIVE

The aim of this article is to review common ED scenarios pertinent to the pediatric heart transplant patients.

DISCUSSION

There are complications unique to this population, such as rejection, opportunistic infections, and medication side effects, that require special considerations, and it is helpful for the emergency medicine (EM) provider to have knowledge about them.

CONCLUSIONS

The unique immunological challenges in these patients, including rejection and medication side effects and opportunistic infections, make this population fragile, and the knowledge of these challenges is helpful for EM providers.

Current status of glucocorticoid usage in solid organ transplantation

Glucocorticoids (GCs) have been the mainstay of immunosuppressive therapy in solid organ transplantation (SOT) for decades, due to their potent effects on innate immunity and tissue protective effects. However, some SOT centers are reluctant to administer GCs long-term because of the various related side effects. This review summarizes the advantages and disadvantages of GCs in SOT. PubMed and Scopus databases were searched from 2011 to April 2021 using search syntaxes covering “transplantation” and “glucocorticoids”. GCs are used in transplant recipients, transplant donors, and organ perfusate solution to improve transplant outcomes. In SOT recipients, GCs are administered as induction and maintenance immunosuppressive therapy. GCs are also the cornerstone to treat acute antibody- and T-cell-mediated rejections. Addition of GCs to organ perfusate solution and pretreatment of transplant donors with GCs are recommended by some guidelines and protocols, to reduce ischemia-reperfusion injury peri-transplant. GCs with low bioavailability and high potency for GC receptors, such as budesonide, nanoparticle-mediated targeted delivery of GCs to specific organs, and combination use of dexamethasone with inducers of immune-regulatory cells, are new methods of GC application in SOT patients to reduce side effects or induce immune-tolerance instead of immunosuppression. Various side effects involving different non-targeted organs/tissues, such as bone, cardiovascular, neuromuscular, skin and gastrointestinal tract, have been noted for GCs. There are also potential drug-drug interactions for GCs in SOT patients.

Impact of induction strategy change on first-year rejection in pediatric heart transplantation at a single center-From postoperative basiliximab to either postoperative anti-thymocyte globulin or preoperative basiliximab

BACKGROUND

Our pediatric heart transplant center transitioned from post-bypass basiliximab (BAS) induction to either anti-thymocyte globulin (ATG) or pre-bypass BAS. The purpose of this study was to compare first-year rejection rates before and after this change.

METHODS

A single-center retrospective analysis was conducted of pediatric heart transplant recipients from 2010 to 2019. Primary outcome was first-year rejection. Bivariate analysis, Kaplan-Meier curves, and multivariable regression were performed across eras.

RESULTS

Forty-three early era patients (55%) received post-bypass BAS, and 35 late era patients (45%) received pre-bypass BAS (n = 17) or ATG (n = 18). First-year rejection decreased in the late era (31% vs 53%, p = .05). This finding was more pronounced after excluding infants (38% vs 73%, p = .006). Late era was associated with a decreased likelihood of rejection (all cohort OR 0.19, 95% CI 0.05-0.66; infants excluded OR 0.17, 95% CI 0.04-0.61). No differences in post-transplant lymphoproliferative disease, donor-specific antibody, or infection were observed.

CONCLUSIONS

Fewer late era patients receiving ATG or pre-bypass BAS induction had first-year rejection compared to the early era patients receiving standard post-bypass BAS induction. This programmatic shift in induction strategy was readily achievable and potentially effective in reducing first-year rejection.

Selected 2019 Highlights in Congenital Cardiac Anesthesia

This article is a review of the highlights of pertinent literature published in 2019, which is of interest to the pediatric cardiac anesthesiologist. After a search of the United States National Library of Medicine PubMed database, several topics emerged in which significant contributions were made in 2019. The authors of this manuscript considered the following topics noteworthy and were included in this review: advances in pediatric heart transplantation, blood management in pediatric cardiac surgery, the impact of nutrition on outcomes in congenital heart surgery, and the use of vasopressin in patients after Fontan palliation.