Regional variation in survival before and after pediatric heart transplantation--an analysis of the UNOS database

Waitlist Outcomes for Pediatric Heart Transplantation in the Current Era: An Analysis of the Pediatric Heart Transplant Society Database

BACKGROUND

Waitlist mortality (WM) remains elevated in pediatric heart transplantation. Allocation policy is a potential tool to help improve WM. This study aims to identify patients at highest risk for WM to potentially inform future allocation policy changes.

METHODS

The Pediatric Heart Transplant Society database was queried for patients <18 years of age indicated for heart transplantation between January 1, 2010 to December 31, 2021. Waitlist mortality was defined as death while awaiting transplant or removal from the waitlist due to clinical deterioration. Because WM is low after the first year, analysis was limited to the first 12 months on the heart transplant list. Kaplan-Meier analysis and log-rank testing was conducted to compare unadjusted survival between groups. Cox proportional hazard models were created to determine risk factors for WM. Subgroup analysis was performed for status 1A patients based on body surface area (BSA) at time of listing, cardiac diagnosis, and presence of mechanical circulatory support.

RESULTS

In total 5974 children met study criteria of which 3928 were status 1A, 1012 were status 1B, 963 were listed status 2, and 65 were listed status 7. Because of the significant burden of WM experienced by 1A patients, further analysis was performed in only patients indicated as 1A. Within that group of patients, those with smaller size and lower eGFR had higher WM, whereas those patients without congenital heart disease or support from a ventricular assist device (VAD) at time of listing had decreased WM. In the smallest size cohort, cardiac diagnoses other than dilated cardiomyopathy were risk factors for WM. Previous cardiac surgery was a risk factor in the 0.3 to 0.7 m2 and >0.7 m2 BSA groups. VAD support was associated with lower WM other than in the single ventricle cohort, where VAD was associated with higher WM. Extracorporeal membrane oxygenation and mechanical ventilation were associated with increased risk of WM in all cohorts.

CONCLUSIONS

There is significant variability in WM among status-1A patients. Potential refinements to current allocation system should factor in the increased WM risk we identified in patients supported by extracorporeal membrane oxygenation or mechanical ventilation, single ventricle congenital heart disease on VAD support and small children with congenital heart disease, restrictive cardiomyopathy, or hypertrophic cardiomyopathy.

Association of Heart Transplant Volume with Presence of Lung Transplant Programs and Heart Transplant's SRTR One-year Survival Rating

BACKGROUND

 Several factors affect heart transplant (HTx) and lung transplant (LTx) program outcomes. Variabilities in institutional and community characteristics have been shown to influence survival. At present, half of HTx centers in the United States do not possess a concomitant LTx program. This study sought to better understand the characteristics of HTx with and without LTx programs.

METHODS

 Nationwide transplant data were collected from the Scientific Registry of Transplant Recipients (SRTR) in August 2020. SRTR star rating ranges from tier 1 (lowest) to tier 5 (highest). HTx volumes and SRTR star ratings for survival were compared between the centers with heart-only (H0) programs and the centers with heart-lung (HL) programs.

RESULTS

 SRTR star ratings were available for 117 transplant centers with one or more HTx reported. The median number of HTx performed over 1 year was 16 (interquartile range [IQR]: 2-29). The number of HL centers (n = 67, 57.3%) were comparable to H0 centers (n = 50, 42.7%; p = 0.14). The HTx volume at the HL centers (28 [IQR: 17-41]) exceeded the HTx volume at the H0 centers (13 [IQR: 9-23]; p < 0.01), but were comparable to the LTx volume at the HL centers (31 [IQR: 16-46]; p = 0.25). The median HTx one-year survival rating was 3 (IQR: 2-4) at both the H0 and HL centers (p = 0.85). The HTx and LTx volumes were positively associated with the respective 1-year survivals (p < 0.01).

CONCLUSION

 While the presence of an LTx program is not directly associated with HTx survival, it has a positive association with the HTx volume. The HTx and LTx volumes are positively associated with the 1-year survival.

Disparities in lung transplantation in children

Lung transplantation is a recognized therapy for end-stage respiratory failure in children and young people. It is only available in selected countries and is limited by access to suitable organs. Data on disparities in access and outcomes for children undergoing lung transplantation are limited. It is clear from data from studies in adults, and from studies in other solid organ transplants in children, that systemic inequities exist in this field. While data relating specifically to pediatric lung transplantation are relatively sparse, professionals should be aware of the risk that healthcare systems may result in disparities in access and outcomes following lung transplantation in children.

Symptomatic presentation influences outcomes in pediatric restrictive cardiomyopathy

Introduction

Children with restrictive cardiomyopathy (RCM) traditionally have a poor prognosis, with most patients either dying or requiring heart transplantation within 2 years of diagnosis. The development of symptoms in RCM suggests advanced disease. However, as screening practices evolve and lead to diagnosis of early disease, identifying appropriate timing of transplant listing becomes increasingly important. In this context we compared outcomes of children with RCM presenting with clinical symptoms to those asymptomatic at initial presentation.

Methods

This retrospective cohort study included 25 patients with RCM presenting to a quaternary care center between 2001 and 2018. Times to transplantation, death, and a composite outcome of adverse cardiac events (CPR, cardioversion, inotropic support, mechanical ventilation, mechanical support, or heart transplant) were compared between those symptomatic and asymptomatic at presentation.

Results

At 2 years following diagnosis, patients asymptomatic at presentation had a significantly better transplant-free survival at 57% compared to 17% for symptomatic patients (p = 0.03). Those asymptomatic at diagnosis also had significantly improved cardiac event-free survival at 71% compared to symptomatic patients at 25% (p = 0.01). In multivariable analysis, cardiac symptoms at presentation remained an independent risk factor for heart-transplant or death [hazard ratio 5.17 (1.28-20.85), p = 0.02].

Conclusion

Patients with RCM who are symptomatic at time of diagnosis have significantly worse transplant-free survival and cardiac event-free survival. Given current practice variability in timing of transplant listing, the presence of any cardiac symptoms is an important negative prognostic marker and should prompt urgent transplant listing.

A systematic review of social determinants of health in pediatric organ transplant outcomes

BACKGROUND

Equitable access to pediatric organ transplantation is critical, although risk factors negatively impacting pre- and post-transplant outcomes remain. No synthesis of the literature on SDoH within the pediatric organ transplant population has been conducted; thus, the current systematic review summarizes findings to date assessing SDoH in the evaluation, listing, and post-transplant periods.

METHODS

Literature searches were conducted in Web of Science, Embase, PubMed, and Cumulative Index to Nursing and Allied Health Literature databases.

RESULTS

Ninety-three studies were included based on pre-established criteria and were reviewed for main findings and study quality. Findings consistently demonstrated disparities in key transplant outcomes based on racial or ethnic identity, including timing and likelihood of transplant, and rates of rejection, graft failure, and mortality. Although less frequently assessed, variations in outcomes based on geography were also noted, while findings related to insurance or SES were inconsistent.

CONCLUSION

This review underscores the persistence of SDoH and disparity in equitable transplant outcomes and discusses the importance of individual and systems-level change to reduce such disparities.

A comprehensive strategy in donor acceptance: Impact on pediatric waitlist and heart transplant outcomes

Significant inter- and intra-center practice variability is present in pediatric donor heart acceptability. This may contribute to variation in the donor refusal rate and may impact waitlist time, morbidity, mortality, and transplant rates. In order to reduce practice variability, our center developed and implemented a comprehensive strategy regarding donor acceptance in September 2017. The aim of this study was to assess the impact of this strategy on waitlist time and outcomes as well as early post-transplant outcomes. We performed a single-center, retrospective analysis of all pediatric (<18 years) patients listed for single-organ heart transplant at our center from September 2015 to September 2018. Patients were divided into those listed before (Group 1) and after implementation of the comprehensive strategy (Group 2). The primary end-point was waitlist time. Secondary end-points included waitlist removal due to death or clinical deterioration, donor refusals per listed patient, early post-transplant outcomes (graft failure, mechanical ventilation time, inotropic support, length of hospital stay) and 1-year post-transplant survival. Of 78 listed patients, 54 were transplanted (29 in Group 1), 9 were removed due to death or clinical deterioration (7 in Group 1) and 15 were removed due to clinical improvement (12 in Group 1). The waitlist time was significantly shorter in Group 2 (17 days, IQR 7-53) vs Group 1 (90 days, IQR 14-162); P = .006. The number of donor refusals was lower in Group 2 (1, IQR 0-2.2) vs Group 1 (4, IQR 2-19); P < .001. The percentage of refused donors with normal function (Left ventricular ejection fraction > 50%) was lower in Group 2 vs Group 1 (53% vs 84%; P < .001). Difference in removal from the waitlist for death or deterioration in Group 2 vs Group 1 (n = 2, 7% vs n = 7, 20%, P = .18) did not reach statistical significance. There was no difference in post-transplant outcomes between groups. The waitlist time and donor refusals significantly decreased after implementation of a comprehensive donor acceptance strategy without impacting transplant outcomes. This analysis supports the need for a comprehensive approach to donor organ acceptance within a pediatric transplant center.

Pediatric cardiac waitlist mortality-Still too high

Cardiac transplantation for children with end-stage cardiac disease with no other medical or surgical options is now standard. The number of children in need of cardiac transplant continues to exceed the number of donors considered "acceptable." Therefore, there is an urgent need to understand which recipients are in greatest need of transplant before becoming "too ill" and which "marginal" donors are acceptable in order to reduce waitlist mortality. This article reviewed primarily pediatric studies reported over the last 15 years on waitlist mortality around the world for the various subgroups of children awaiting heart transplant and discusses strategies to try to reduce the cardiac waitlist mortality.

Behavioral economics-A framework for donor organ decision-making in pediatric heart transplantation

The high discard rate of pediatric donor hearts presents a major challenge for children awaiting heart transplantation. Recent literature identifies several factors that contribute to the disparities in pediatric donor heart usage, including regulatory oversight, the absence of guidelines on pediatric donor heart acceptance, and variation among transplant programs. However, a likely additional contributor to this issue are the behavioral factors influencing transplant team decisions in donor offer scenarios, a topic that has not yet been studied in detail. Behavioral economics and decision psychology provide an excellent foundation for investigating decision-making in the pediatric transplant setting, offering key insights into the behavior of transplant professionals. We conducted a systematic review of published literature in pediatric heart transplant related to behavioral economics and the psychology of decision-making. In this review, we draw on paradigms from these two domains in order to examine how existing aspects of the transplant environment, including regulatory oversight, programmatic variation, and allocation systems, may precipitate potential biases surrounding donor offer decisions. Recognizing how human decision behavior influences donor acceptance is a first step toward improving utilization of potentially viable pediatric donor hearts.

ISHLT consensus statement on donor organ acceptability and management in pediatric heart transplantation

The number of potential pediatric heart transplant recipients continues to exceed the number of donors, and consequently the waitlist mortality remains significant. Despite this, around 40% of all donated organs are not used and are discarded. This document (62 authors from 53 institutions in 17 countries) evaluates factors responsible for discarding donor hearts and makes recommendations regarding donor heart acceptance. The aim of this statement is to ensure that no usable donor heart is discarded, waitlist mortality is reduced, and post-transplant survival is not adversely impacted.

Center Variation in Hospital Costs for Pediatric Heart Transplantation: The Relationship Between Cost and Outcomes

There are limited published data addressing the costs associated with pediatric heart transplantation and no studies evaluating the variation in costs across centers. We aimed to describe center variation in pediatric heart transplant costs and assess the association of transplant hospitalization costs with patient outcomes. Using a linkage between the Pediatric Health Information System and Scientific Registry of Transplant Recipients databases, hospital costs were assessed for patients (< 18 years of age) undergoing heart transplantation (2007-2016). Severity-adjusted patient costs were calculated using generalized linear mixed-effects models with a random hospital intercept. Center variation in hospital cost was described after adjusting for the predicted risk of in-hospital mortality. Post-transplant survival was compared between low- and high-cost centers using Cox proportional hazard models. A total of 2156 patients were included from 24 centers. There was 3.7-fold variation in transplant hospitalization costs across centers, ranging from $329,477 to $1,226,507. Patients transplanted at high-cost centers have a higher predicted risk of in-hospital mortality (8.1% vs. 6.1%, p < 0.001). Both early (p = 0.008) and long-term (p = 0.003) post-transplant survival were better in patients transplanted at low-cost centers. Transplant at low-cost centers was associated with improved post-transplant survival, independent of patient-specific risk (adjusted hazard ratio 0.72; 95%CI 0.57-0.92, p = 0.008). There is wide variation in cost for pediatric heart transplant inpatient care among U.S. centers with low-cost centers demonstrating the best patient survival. Differences in patient populations likely contribute to these findings, but cannot account for all the variation seen. This suggests that variability in the delivery of care across centers may influence post-transplant survival.

Regional variation in the use of 1A status exceptions for pediatric heart transplant candidates: is this equitable?

The use of status exceptions (SE) was recently publicized as a strategy to reduce waitlist times for children awaiting heart transplant (HTx). The aim of this study was to assess SE use across UNOS regions and compare survival in patients listed using a SE to those listed by standard criteria. The OPTN database was queried for all pediatric patients listed for HTx (2000-2014). SE use was compared across UNOS regions. Survival curves were generated and compared using the log-rank test. 1A SE use is uncommon, being utilized in 108 of 4587 pediatric 1A listings (2.4%). There is significant variability in SE use across UNOS regions (0.7%-16.4% of 1A listings, P < .001). Waitlist survival is significantly higher in candidates listed using a 1A SE compared to those listed by standard criteria (P = .001) and is similar to 1B listings. Regional variation in 1A SE use has the potential to introduce bias into a system designed to be equitable. Waitlist survival in patients listed using a SE is similar to those listed status 1B, suggesting these patients may not require 1A status. Careful review of pediatric heart allocation policies is needed to optimize patient outcomes and ensure a fair and unbiased allocation system.

A contemporary review of paediatric heart transplantation and mechanical circulatory support

Improvements in the care of children with cardiomyopathy, CHDs, and acquired heart disease have led to an increased number of children surviving with advanced heart failure. In addition, the advent of more durable mechanical circulatory support options in children has changed the outcome for many patients who otherwise would have succumbed while waiting for heart transplantation. As a result, more children with end-stage heart failure are being referred for heart transplantation, and there is increased demand for a limited donor organ supply. A review of important publications in the recent years related to paediatric heart failure, transplantation, and mechanical circulatory support show a trend towards pushing the limits of the current therapies to address the needs of this growing population. There have been a number of publications focussing on previously published risk factors perceived as barriers to successful heart transplantation, including elevated pulmonary vascular resistance, medication non-adherence, re-transplantation, transplantation of the failed Fontan patient, and transplantation in an infant or child bridged with mechanical circulatory support. This review will highlight some of these key articles from the last 3 years and describe recent advances in the understanding, diagnosis, and management of children with end-stage heart disease.

Use of short-term circulatory support as a bridge in pediatric heart transplantation

BACKGROUND

Heart transplantation is considered the gold standard therapy for the advanced heart failure, but donor shortage, especially in pediatric patients, is the main limitation for this procedure, so most sick patients die while waiting for the procedure.

OBJECTIVE

To evaluate the use of short-term circulatory support as a bridge to transplantation in end-stage cardiomyopathy.

METHODS

Retrospective clinical study. Between January 2011 and December 2013, 40 patients with cardiomyopathy were admitted in our Pediatric Intensive Care Unit, with a mean age of 4.5 years. Twenty patients evolved during hospitalization with clinical deterioration and were classified as Intermacs 1 and 2. One patient died within 24 hours and 19 could be stabilized and were listed. They were divided into 2 groups: A, clinical support alone and B, implantation of short-term circulatory support as bridge to transplantation additionally to clinical therapy.

RESULTS

We used short-term mechanical circulatory support as a bridge to transplantation in 9. In group A (n=10), eight died waiting and 2 patients (20%) were transplanted, but none was discharged. In group B (n=9), 6 patients (66.7%) were transplanted and three were discharged.The mean support time was 21,8 days (6 to 984 h). The mean transplant waiting list time was 33,8 days. Renal failure and sepsis were the main complication and cause of death in group A while neurologic complications were more prevalent en group B.

CONCLUSION

Mechanical circulatory support increases survival on the pediatric heart transplantation waiting list in patients classified as Intermacs 1 and 2.

Creation of a quantitative score to predict the need for mechanical support in children awaiting heart transplant

BACKGROUND

Due to the availability of new devices, the use of ventricular assist devices (VADs) in children has been increasing; however, patient selection and optimal timing of device implantation in this population remains uncertain.

METHODS

A retrospective review of the United Network for Organ Sharing dataset identified 5,200 listings without mechanical circulatory support (MCS) for isolated pediatric heart transplant, 1995 to 2012. Patients were randomly divided into a derivation and validation cohort. A multivariable logistic regression model predicting the likelihood of death or need for MCS within 60 days was built using the derivation cohort and tested in the validation cohort. A simplified score (PedsMCS score) was developed and evaluated for accuracy.

RESULTS

The predictive model consisted of variables present at listing (age, albumin level, creatinine clearance, serum bilirubin, mechanical ventilation, and inotropic support). It had good predictive ability (C statistic 0.7304) within the validation cohort. The simplified PedsMCS score was also predictive (C statistic 0.7217) and there was a strong correlation between predicted and expected outcomes (r=0.91, p<0.0001). Patients with PedsMCS score 16 or greater had a significantly higher risk of death or MCS within 2 months (36.6%) than those with low scores (<6) (1.5%, p<0.0001). A single point increase in PedsMCS score was associated with a 16.7% increase in the risk of death or MCS with 2 months (p<0.0001).

CONCLUSIONS

We have developed and validated a simplified score to predict the need for MCS based on risk factors present at listing. This will provide more accurate prognostication in children awaiting heart transplant, and may improve patient selection.