Impact of the 2016 revision of US Pediatric Heart Allocation Policy on waitlist characteristics and outcomes

Contemporary outcomes of pediatric cardiac transplantation with a positive retrospective crossmatch

BACKGROUND

A positive crossmatch (+ XM) has traditionally been associated with adverse outcomes following pediatric heart transplantation. However, more recent studies suggest that favorable intermediate-term outcomes may be achieved despite a + XM. This study's hypothesis is that children with a + XM have similar long-term survival, but higher rate of complications such as rejection, coronary allograft vasculopathy (CAV), and infection, compared to patients with a negative (-) XM.

METHODS

The Pediatric Heart Transplant Society Registry (PHTS) database was queried from 2010-2021 for all patients <18 years of age with a known XM. Baseline demographics were compared between + XM and - XM groups using appropriate parametric and non-parametric group comparisons. Cox Proportional Hazards Modeling was used to identify risk factors for post-transplant graft loss, rejection, and CAV.

RESULTS

Of 4599 pediatric heart transplants during the study period, XM results were available for 3914 (85%), of which 373 (9.5%) had a + XM. Univariate analysis showed lower 10-year survival for patients with + XM (HR = 1.3, p = .04). Multivariate analyses revealed no significant difference in 10-year survival in the 2 groups; however, time to first rejection (p = .0001) remained significantly shorter in the + XM group.

CONCLUSIONS

Pediatric patients transplanted across a + XM experience earlier rejection; however, after multivariate adjustment, + XM is not independently associated with intermediate-term graft loss. The risk of heart transplantation against a + XM must be balanced with the ongoing risk of waitlist mortality.

Racial and socioeconomic disparities in status exceptions for pediatric heart transplant candidates under the current U.S. Pediatric Heart Allocation Policy

BACKGROUND

The 2016 revision of the US Pediatric Heart Allocation Policy developed stringent rules for priority status creating impetus for clinicians to seek status exceptions. We hypothesized there may be differential status exceptions based on race and socioeconomic status (SES) contributing to disparities in waitlist outcomes.

METHODS

The Scientific Registry for Transplant Recipients was queried for children listed for heart transplant from 2012 to 2020. Waitlist status & mortality with regards to race and neighborhood SES were stratified by listing before (Era 1) or after (Era 2) the policy change.

RESULTS

The use of both 1A and 1B exceptions (E) increased in Era 2. In Era 1, there was no association between patient race or neighborhood SES on use of 1A(E) or 1B(E) when controlling for age and diagnosis. In Era 2, neither race nor neighborhood SES were associated with 1A(E), but both were associated with 1B(E): non-Hispanic (NH) Black children and those from low- and middle-SES neighborhoods were significantly less likely to be listed 1B(E). In Era 1, there were no significant differences in waitlist mortality based on race at any waitlist status; in Era 2, NH Black children had higher waitlist mortality when initially listed 1B or 2.

CONCLUSIONS

Since the 2016 policy change, racial disparities in waitlist mortality have worsened among children initially listed with lower priority status. Unequal use of 1B exceptions, which lower waitlist mortality, may explain some of these disparities. Recently implemented standardized pediatric exception guidance has the potential to improve equity.

Racial disparity exists in the utilization and post-transplant survival benefit of ventricular assist device support in children

PURPOSE

Children of minority race and ethnicity experience inferior outcomes postheart transplantation (HTx). Studies have associated ventricular assist device (VAD) bridge-to-transplant (BTT) with similar-to-superior post-transplant-survival (PTS) compared to no mechanical circulatory support. It is unclear whether racial and ethnic discrepancies exist in VAD utilization and outcomes.

METHODS

The United Network for Organ Sharing (UNOS) database was used to identify 6,121 children (<18 years) listed for HTx between 2006 and 2021: black (B-22% of cohort), Hispanic (H-21%), and white (W-57%). VAD utilization, outcomes, and PTS were compared between race/ethnicity groups. Multivariable Cox proportional analyses were used to study the association of race and ethnicity on PTS with VAD BTT, using backward selection for covariates.

RESULTS

Black children were most ill at listing, with greater proportions of UNOS status 1A/1 (p < 0.001 vs H & W), severe functional limitation (p < 0.001 vs H & W), and greater inotrope requirements (p < 0.05 vs H). Non-white children had higher proportions of public insurance. VAD utilization at listing was: B-11%, H-8%, W-8% (p = 0.001 for B vs H & W). VAD at transplant was: B-24%, H-21%, W-19% (p = 0.001 for B vs H). At transplant, all VAD patients had comparable clinical status (functional limitation, renal/hepatic dysfunction, inotropes, mechanical ventilation; all p > 0.05 between groups). Following VAD, hospital outcomes and one-year PTS were equivalent but long-term PTS was significantly worse among non-whites-(p < 0.01 for W vs B & H). On multivariable analysis, black race independently predicted mortality (hazard ratio 1.67 [95% confidence interval 1.22-2.28]) while white race was protective (0.54 [0.40-0.74]).

CONCLUSIONS

Pediatric VAD use is, seemingly, equitable; the most ill patients receive the most VADs. Despite similar pretransplant and early post-transplant benefits, non-white children experience inferior overall PTS after VAD BTT.

Impact of Weight on Ventricular Assist Device Outcomes in Dilated Cardiomyopathy Patients in Pediatric Centers: An ACTION Registry Study

Ventricular assist device (VAD) options vary for children in different weight groups. This study evaluates contemporary device usage and outcomes for children based on weight. Data from the Advanced Cardiac Therapies Improving Outcomes Network (ACTION) registry were examined for patients with dilated cardiomyopathy (DCM) in 4 weight cohorts: <8 kg, 8-20 kg, 21-40 kg, and >40 kg, for devices implanted 3/2013-10/2020. Adverse event rates and ultimate outcome (deceased, alive on device, transplanted, or ventricular recovery) were analyzed. 222 DCM patients were identified with 24% in cohort 1, 23% in cohort 2, 15% in cohort 3, and 38% in cohort 4. Of 272 total implants, paracorporeal pulsatile devices were most common (95%) in cohorts 1 and 2 and intracorporeal continuous devices (81%) in cohorts 3 and 4. Stroke was noted in 17%, 12%, 6%, and 4% of cohorts, respectively (Cohort 1 vs. 4 and 2 vs. 4 - p = 0.01; other comparisons - not significant). Incidences of major bleeding, device malfunction, and infection was not different. All cohorts had >90% positive outcomes. Stroke incidence was higher in smaller cohorts, but other outcomes were similar. Positive outcomes were attained in over 90% across all weight groups, demonstrating excellent outcomes using current VADs in this DCM population.

Impact of 2016 UNOS pediatric heart allocation policy changes on VAD utilization, waitlist, and post-transplant survival outcomes in children with CHD versus Non-CHD

AIMS

We analyzed the impact of the revised pediatric heart allocation policy on types of ventricular assist device (VAD) utilization, and waitlist (WL) and post-heart transplant (HT) survival outcomes in congenital heart disease (CHD) versus non-CHD patients before (Era-1) and after (Era-2) pediatric heart allocation policy implementation.

METHODS

We retrospectively reviewed the UNOS database from December 16, 2011, through March 31, 2021, for patients < 18 years old and listed for primary HT. We compared the differences observed between Era-1 and Era-2.

RESULTS

5551 patients were listed for HT, of whom 2447(44%) were in Era-1 and 3104(56%) were in Era-2. CHD patients were listed as status 1A unchanged, but the number of patients listed as status 1B decreased in Era-2, whereas the number of non-CHD patients listed as status 1A decreased, but status 1B increased. In Era-2 compared to Era-1, both temporary (1% to 4%, p < .001) and durable VAD (13.6% to 17.8%, p < .001) utilization increased, and the transplantation rate per 100-patient years increased in both groups. The median WL period for CHD patients increased marginally from 70 to 71 days (p = .06), whereas for non-CHD patients it decreased from 61 to 54 days (p < .001). Adjusted 90-day WL survival increased from 84% to 88%, p = .016 in CHD, but there was no significant change in non-CHD patients (p = .57). There was no significant difference in 1-year post-HT survival in CHD and non-CHD patients between Era-1 and Era-2.

CONCLUSIONS

In summary, after the revised heart allocation policy implementation, temporary and durable VAD support increased, HT rate increased, waitlist duration marginally increased in the CHD cohort and decreased in the non-CHD cohort, and 90-day WL survival probability improved in children with CHD without significant change in 1-year post-HT outcomes. Future studies are needed to identify changes to the policy that may further improve the listing criteria to improve WL duration and post-HT survival.

Deceased donor organ allocation in pediatric transplantation: A historical narrative

BACKGROUND

Since the earliest clinical successes in solid organ transplantation, the proper method of organ allocation for children has been a contentious subject. Over the past 30-35 years, the medical and social establishments of various countries have favored some degree of preference for children on the respective waiting lists. However, the specific policies to accomplish this have varied widely and changed frequently between organ type and country.

METHODS

Organ allocation policies over time were examined. This review traces the reasons behind and the measures/principles put in place to promote early deceased donor transplantation in children.

RESULTS

Preferred allocation in children has been approached in a variety of ways and with varying degrees of commitment in different solid organ transplant disciplines and national medical systems.

CONCLUSION

The success of policies to advantage children has varied significantly by both organ and medical system. Further work is needed to optimize allocation strategies for pediatric candidates.

Barriers and misconceptions of ex situ heart perfusion in pediatric donation

BACKGROUND

Despite efforts, pediatric HTx candidates continue to have high waitlist mortality due to limited donor availability. However, there is a significant number of offered hearts not used due to concerns of viability. ESHP is a method for continuous perfusion of the donor heart that allows assessment and extended out-of-body time. It is imperative to understand healthcare stakeholders' perspectives on ESHP for implementation. Therefore, the aims of this qualitative study were to: (1) Explore pediatric stakeholders' perspectives toward ESHP; and (2) Identify barriers to widespread adoption of this technology.

METHODS

Virtual focus groups were completed with pediatric HTx healthcare professional stakeholders. Following transcription of audio-recordings, the material was analyzed using content analysis.

RESULTS

Four focus groups were completed with 17 participants, representing 12 institutions and three countries. Focus groups revealed varied understanding of both current and potential uses of ESHP. Participants did see the potential benefits of extending out-of-body time for and the ability to evaluate donor heart quality. However, concerns were expressed relating to patient selection, wait-list times, post-HTx outcomes, adverse events, and technical issues. These were felt to be important to understand in order to justify the costs of ESHP and impact on the healthcare system.

CONCLUSIONS

This project represents the first qualitative formative evaluation of ESHP in pediatrics. The knowledge gained from stakeholders will form the basis for education initiatives, clinical trial design, and roll-out of new ESHP technologies designed for pediatrics.

Donor-specific antibodies after heart transplantation for Fontan-associated protein-losing enteropathy

BACKGROUND

Despite ubiquitous exposure to sensitizing events, most Fontan PLE patients have low panel reactive antibodies (PRA). To assess whether they are at risk for donor-specific antibody (DSA) memory response following heart transplantation (HT) when their PLE resolves, DSA profiles, incidence of rejection, and graft outcomes in Fontan recipients with and without PLE were compared.

METHODS

Patient characteristics, appearance of newly detected DSA (nDSA), and graft outcomes were compared between patients with and without PLE using Wilcoxon rank-sum and Chi-squared tests. DSA burden was quantified using titers and time to nDSA, incidence of rejection, and graft outcomes were compared using Kaplan-Meier curves and the log-rank test.

RESULTS

Characteristics of patients with and without PLE were similar. Lymphocyte and albumin levels were lower in the PLE group, and flow PRA were comparable. Graft failure, CAV, and ACR were similar between the two groups, but AMR occurred more frequently in the PLE group (p = .03). Nearly 50% of PLE patients experienced class II nDSA by 1-year post-HT, compared to 30% of non-PLE patients, but this difference was statistically not significant. Antibody burden did not differ between groups.

CONCLUSIONS

In this cohort, PLE was associated with AMR within the first-year post-HT, despite no significant difference in nDSA. Small patient numbers limited statistical comparison of nDSA in this cohort. PLE may be a risk factor for AMR post-HT, and the possibility of a clinically important DSA memory response remains. Larger studies are necessary to better understand these preliminary findings.

Worsening racial disparity in waitlist mortality for pediatric heart transplant candidates since the 2016 Pediatric Heart Allocation Policy revision

BACKGROUND

The US Pediatric Heart Allocation Policy (PHAP) was revised in March 2016, with the goal of reducing waitlist mortality. We evaluated the hypothesis that these changes, which increased status exceptions, have worsened racial disparities in waitlist outcomes.

METHODS

Children in the Pediatric Heart Transplant Study database listed for first heart transplant from January 2012 - June 2020 were included and stratified by listing before (Era 1) or after (Era 2) the PHAP revision.

RESULTS

A total of 4,089 children were listed during the study period. Compared with white children (n = 2648), non-white children (n = 1441) were more likely to have an underlying diagnosis of cardiomyopathy in both eras. Waitlist mortality was similar in white and non-white children in Era 1, but comparatively worse for non-white children in Era 2. In multivariable analysis controlling for diagnosis, age, and severity markers, non-white children had a significantly higher waitlist mortality only in Era 2 (Era 1: sHR 1.22 [95%CI 0.90 - 1.66] vs. Era 2: sHR 1.57 [95%CI 1.17 - 2.10]).

CONCLUSIONS

Widening racial disparities in waitlist mortality may be an unintended consequence of the 2016 PHAP revision. Additional analyses may inform the degree to which this policy vs. unrelated changes in care differentially contribute to these disparities.

Waitlist Outcomes for Children With Congenital Heart Disease: Lessons Learned From Over 5000 Heart Transplant Listings in the United States

BACKGROUND

We evaluated the impact of pediatric heart-allocation policy changes over time and the approval of the Berlin ventricular assist device (VAD) on waitlist (WL) outcomes for children with congenital heart disease (CHD).

METHODS

The Scientific Registry of Transplant Recipients database was evaluated to include all children (age < 18) with CHD and cardiomyopathy (CMP) on the WL between 1999 and 2019, divided into 4 eras: Era 1 (1999-2008); Era 2 (2009-2011); Era 3 (2012-2016); and Era 4 (2016-2019). WL characteristics and survival outcomes were evaluated for patients with CHD over time and were compared to those with CMP listed currently (Era 4).

RESULTS

We included 5185 children with CHD on the WL during the study period; 1999 (39%) were listed in Era 1; 693 (13%) in Era 2; 1196 (23%) in Era 3; and 1297 (25%) in Era 4. Compared to the CHD WL in eras 1 and 2, those in Era 4 were less likely to be infants (48% vs 49% vs 43%), on mechanical ventilation (30% vs 26% vs 19%), on extracorporeal membrane oxygenation (15% vs 9.7% vs 6.2%), and were more likely to be on a VAD (2.4% vs 2.2% vs 6.0%) (P < .05 for all). WL survival improved in children with CHD from Era 1 to Era 4 (P < .001). However, in Era 4, children with CHD had lower WL survival than those with CMP (P < .001).

CONCLUSION

Children with CHD are increasingly being listed with less advanced heart failure, and they have had improved WL survival over time; however, WL outcomes remain inferior to those with CMP. Advances in pediatric medical and VAD therapy may improve future WL outcomes.

Pediatric heart transplant waiting times in the United States since the 2016 allocation policy change

We describe waiting times for pediatric heart transplant (HT) candidates after the 2016 revision to the US allocation policy. The OPTN database was queried for pediatric HT candidates listed between 7/2016 and 4/2019. Of the 1789 included candidates, 65% underwent HT, 14% died/deteriorated, 8% were removed for improvement, and 13% were still waiting at the end of follow-up. Most candidates were status 1A at HT (81%). Median wait times differ substantially by listing status, blood type, and recipient weight. The likelihood of HT was lower in candidates <25 kg and in those with blood type O; The <25 kg, blood type O subgroup experiences longer wait times and higher wait list mortality. For status 1A candidates, median wait times were 108 days (≤25 kg, blood type O), 80 days (≤25 kg, non-O), 47 days (>25 kg, O), and 24 days (>25 kg, non-O). We found that centers with more selective organ acceptance practices, based on a lower median Pediatric Heart Donor Assessment Tool (PH-DAT) score for completed transplants, experience longer status 1A wait times for their listed patients. These data can be used to counsel families and to select appropriate advanced heart failure therapies to support patients to transplant.

Transplantation for pulmonary arterial hypertension with congenital heart disease: Impact on outcomes of the current therapeutic approach including a high-priority allocation program

Patients with end-stage pulmonary arterial hypertension due to congenital heart disease have limited access to heart-lung transplantation or double-lung transplantation. We aimed to assess the effects of a high-priority allocation program established in France in 2007. We conducted a retrospective study to compare waitlist and posttransplantation outcomes before versus after implementation of the high-priority allocation program. We included 67 consecutive patients (mean age at listing, 33.2 ± 10.5 years) with pulmonary arterial hypertension due to congenital heart disease listed for heart-lung transplantation or double-lung transplantation from 1997 to 2016. At one month, the incidences of transplantation and death before transplantation were 3.5% and 24.6% in 1997-2006, 4.8% and 4.9% for patients on the regular list in 2007-2016, and 41.2% and 7.4% for patients listed under the high-priority allocation program (p < .001 and p = .0001, respectively). Overall survival was higher in patients listed in 2007-2016 (84.2% and 61.2% at 1 and 10 years vs. 36.8% and 22.1%, p = .0001). Increased incidence of transplantation, decreased waiting list mortality, and improved early and long-term outcomes were observed in patients with pulmonary arterial hypertension due to congenital heart disease listed for transplantation in the recent era, characterized by implementation of a high-priority allocation program.

A coordinated approach to improving pediatric heart transplant waitlist outcomes: A summary of the ACTION November 2019 waitlist outcomes committee meeting

The number of children needing heart transplantation continues to rise. Although improvements in heart failure therapy, particularly durable mechanical support, have reduced waitlist mortality, the number of children who die while waiting for a suitable donor organ remains unacceptably high. Roughly, 13% of children and 25% of infants on the heart transplant waitlist will not survive to transplantation. With this in mind, the Advanced Cardiac Therapies Improving Outcomes Collaborative Learning Network (ACTION), through its Waitlist Outcomes Committee, convened a 2-day symposium in Ann Arbor, Michigan, from 2-3 November 2019, to better understand the factors that contribute to pediatric heart transplant waitlist mortality and to focus future efforts on improving the organ allocation rates for children needing heart transplantation. Using improvement science methodology, the heart failure-transplant trajectory was broken down into six key steps, after which modes of failure and opportunities for improvement at each step were discussed. As a result, several projects aimed at reducing waitlist mortality were initiated.

Rehospitalization Following Pediatric Heart Transplantation: Incidence, Indications, and Risk Factors

Rehospitalization following pediatric heart transplantation is common. However, existing data remain somewhat limited. Using a novel linkage between administrative and clinical databases, pediatric heart transplant (HT) recipients from 29 centers who survived to discharge were retrospectively reviewed to determine the frequency, timing of, and indication for all-cause rehospitalizations in the year following transplant discharge. Of 2870 pediatric HT recipients, 1835 (63.9%) were rehospitalized in the first year post-discharge (5429 total readmissions). Rehospitalization rates varied significantly across centers (46% to 100%) and were inversely correlated to center transplant volume (r² 0.25, p < 0.01). The median number of rehospitalizations per patient was 2 (IQR 1-4) and the median time to first rehospitalization was 29 days (IQR 9-99 days). Independent risk factors for rehospitalization included younger age at HT (HR 0.99, 95% CI 0.97-0.99), congenital heart disease (HR 1.2, 95% CI 1.1-1.4), listing status 1B at transplant (HR 1.3, 95% CI 1.1-1.5), and post-transplant complications including rejection prior to discharge (HR 1.5 95% CI 1.3-1.8) and chylothorax (HR 1.3, 95% CI 1.0-1.6). Cardiac diagnoses were the most common indication for rehospitalization (n = 1600, 29.5%), followed by infection (n = 1367, 25.2%). These findings may serve to guide the development of interventions aimed at reducing post-HT hospitalizations.