Wooster L, O’Connor MJ, Zhang X, Mavroudis CD, Maeda K, Ahmed H, Edwards J, Lin KY, Wittlieb-Weber C, Rossano J, Edelson JB. Circulation. 2025 Jan 9. doi: 10.1161/CIRCULATIONAHA.124.072335. Online ahead of print. PMID: 39781913
Take-home Points:
- The changes by the Organ Procurement and Transplant Network (OPTN) in the United States for organ allocation have had varying impacts across pediatric and adult populations with cardiomyopathy and congenital heart disease (CHD)
- While overall waitlist mortality improved, benefits were not uniform. Pediatric CHD and adult cardiomyopathy patients saw improvements, whereas adults with CHD did not.
- Changes in mechanical support use, specifically increased ventricular assist device (VAD) use in children and more frequent use of intra-aortic balloon pumps (IABP) in adults, likely reflect shifts in prioritization criteria under the new system.
Commentary from Dr. David M. Leone, section editor of ACHD Journal Watch:
Introduction:
Heart transplantation (HT) remains the only definitive therapy for patients with advanced, medically refractory heart failure. In response to ongoing disparities in waitlist outcomes and to better align transplant priority with medical urgency, the Organ Procurement and Transplantation Network (OPTN) implemented policy changes to heart allocation in 2016 for pediatric patients and in 2018 for adults. These revisions deprioritized stable patients on inotropes and chronic mechanical support (e.g., durable ventricular assist devices), while elevating those on temporary support modalities like extra-corporeal mechanical oxygenation (ECMO) or intra-aortic balloon pump (IABP). Although intended to reduce waitlist mortality, the impact of these changes across populations with differing heart failure etiologies, particularly those with congenital heart disease (CHD) has not been fully understood. This study evaluates the differential effect of these allocation changes on pediatric and adult patients with CHD and cardiomyopathy, two distinct populations with divergent trajectories and options for mechanical support.
Study Design:
This was a retrospective cohort study utilizing the United Network for Organ Sharing (UNOS) database. The authors identified pediatric (<18 years) and adult (18–50 years) patients listed for HT between 2011–2021 for pediatrics and 2015–2021 for adults. The study period was divided into pre- and post-allocation change eras. Diagnosis codes were used to group patients by CHD or cardiomyopathy.
The primary analysis utilized a competing risk model, which accounts for the possibility that patients are either transplanted or removed from the list due to clinical deterioration or death. This statistical framework is essential when interpreting waitlist outcomes, particularly in high-risk groups such as adults with CHD, who may be more likely to become too sick for transplant before organ availability. Cardiomyopathy patients were used as an internal comparison group given their larger numbers and relatively well-established outcomes under the new system.
Key Finding
- Study population: 11,637 patients were included, comprising 2882 pediatric CHD, 2348 pediatric cardiomyopathy, 594 adult CHD, and 5813 adult cardiomyopathy patients
- Waitlist mortality reduction was significant for:
- Infants with CHD (HR 0.75, 95% CI 0.57–0.99)
- Children with CHD (HR 0.61, 95% CI 0.43–0.86)
- Adults with cardiomyopathy (HR 0.60, 95% CI 0.44–0.81)
- No significant mortality reduction was seen in:
- Infants or children with cardiomyopathy
- Adults with CHD
- Mechanical circulatory support trends:
- Increased VAD use in pediatric CHD post-policy change
- Increased use of temporary devices (e.g., IABP, ECMO) in adults, particularly those with cardiomyopathy
- Sensitization concerns were raised for CHD patients, especially adults, who may have increased wait times or be less likely to receive organs due to alloantibody formation
- There was an increase in HT in minority race children with CHD following changes in allocation
Strengths:
- Large national cohort with detailed stratification by age and diagnosis and tens of thousands of patients
- Use of cardiomyopathy as a comparative reference group enhanced interpretability
- Rigorous competing risk survival methodology accounts for key clinical realities
Limitations:
- Exclusion of multi-organ transplant candidates (e.g., heart-liver in Fontan patients) limits generalizability to some of the highest-risk CHD subgroups
- No detailed data on donor pool expansion strategies (e.g., donation after circulatory death and hepatis C positive donors)
- Sensitization status and its role in allocation or waitlist attrition were not fully explored
Discussion:
This study provides critical insight into how changes in transplant allocation policy have affected different patient populations. Importantly, while pediatric CHD patients benefited from the revised system, adults with CHD, especially those with complex anatomy or multiple prior sternotomies, did not experience the same improvement in waitlist mortality. This discrepancy highlights the limitations of a system originally designed around acquired heart failure and mechanical support access, which may not reflect the nuanced risks faced by adult congenital heart disease patients.
The increasing reliance on temporary mechanical support devices in adults with cardiomyopathy aligns with the policy’s intended prioritization of those with high short-term risk. However, such devices are often not feasible in adult CHD patients due to anatomical or physiological constraints. Meanwhile, the rise in VAD use among children with CHD may reflect improved technology and experience, although the long-term impact remains to be seen.
This study also raises questions about whether pediatric and adult allocation systems should remain bifurcated. The arbitrary age cutoffs may disadvantage certain adolescent and young adult CHD patients whose physiology does not match the adult allocation assumptions.
Conclusion:
The OPTN allocation changes have improved waitlist mortality overall, but the benefit has not been equitably distributed. Adults with congenital heart disease remain at elevated risk, underscoring the need for a more tailored allocation framework that accounts for diagnosis-specific limitations in mechanical support and sensitization status. Future policy iterations should explore bridging the pediatric-adult divide and better incorporate congenital-specific factors into prioritization criteria.
