Trends in pediatric donor heart discard rates and the potential use of unallocated hearts for allogeneic valve transplantation

Innovative strategies to increase cardiac donor availability

Heart transplantation is a life-saving procedure for many people throughout the world. Data shows that in 2024, there was an increase in the volume of adult heart transplantation in the United States even as there was a decrease in the volume of pediatric heart transplantation to the lowest volume in a decade. Organ availability remains a major limiting factor affecting transplant volume. This mandates that innovation must take place to increase the supply of donor organs. While some strategies such as donation after cardiac death, hepatitis C virus + transplantation, and ABO-incompatible transplantation have increased the pool for donation, it still falls short of meeting the demand. Other proposed strategies include splitting the donor heart to provide multiple partial heart transplants, domino partial heart transplantation, changes in legislation including opt-out legislation, and xenotransplantation. Further evolution and refinement of these strategies will make a meaningful impact on patients awaiting life-saving heart transplants.

Challenges in the Development and Evaluation of Pediatric Heart Valve Technologies

BACKGROUND

In October 2022, the Heart Valve Collaboratory and United States Food and Drug Administration convened a global multidisciplinary workshop to address the unmet clinical need to promote and accelerate the development of pediatric-specific heart valve technologies.

METHODS

The Pediatric Heart Valve Global Multidisciplinary Workshop was convened in October 2022. Key stakeholders, including expert clinicians in pediatric cardiology and cardiac surgery, valve manufacturers, engineers, and scientists were assembled to review the current state of the art, discuss unique challenges in the premarket and postmarket evaluation of pediatric valve therapies, and highlight emerging technologies that show potential to address some of the key unmet needs of children with valve disease.

RESULTS

The workshop highlighted the tremendous clinical need to develop a new framework for developing and evaluating pediatric-specific heart valve therapies.

CONCLUSIONS

This report summarizes the proceedings of the workshop and outlines the key considerations for developing a new framework for evaluating novel pediatric heart valve therapies.

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.

Cryopreservation of biological materials: applications and economic perspectives

Cryopreservation is a transformative technology that allows for the long-term storage of biological materials by cooling them to extremely low temperatures at which metabolic and biochemical processes are effectively slowed or halted. Cryopreservation utilizes various techniques to minimize ice crystal formation and cellular damage during freezing and thawing processes. This technology has broad applications in the fields of medicine, agriculture, and conservation, spanning across stem cell research, reproductive and regenerative medicine, organ transplantation, and cell-based therapies, each with significant economic implications. While current techniques and their associated costs present certain challenges, ongoing research advancements related to cryoprotectants, cooling methods, and automation promise to enhance efficiency and accessibility, potentially broadening the technology's impact across various sectors. This review focuses on the applications of cryopreservation, research advancements, and economic implications, emphasizing the importance of continued research to overcome the current limitations.

Domino partial heart transplantation

Heart valve replacement in pediatric cardiothoracic surgery poses problems because conventional heart valve implants do not have the ability to grow. This mandates serial reoperations for implant exchanges until an adult-size implant can fit. Partial heart transplantation eliminates these reoperations because the transplanted valves grow. However, partial heart transplantation competes with heart transplantation for a limited supply of donor hearts. This is a critical barrier to the progress of the field. Domino partial heart transplantation is a new surgical technique that overcomes this barrier by capitalizing cardiectomy hearts from heart transplant recipients for partial heart transplantation. This surgical technique has the potential to transform pediatric heart valve replacement by greatly expanding the cardiac donor pool, increasing the time available for matching donors with recipients and simplifying the logistics of donation. As a result, the number of domino partial heart transplants is expected to exceed the number of partial heart transplants from deceased donors.

Indications and Practical Considerations for Partial Heart Transplantation

Partial heart transplantation is a new approach to deliver growing heart valve substitutes for children. The rationale for partial heart transplantation is that the valves contained in heart transplants grow. Partial heart transplants differ from heart transplants because only the part of the heart containing the necessary valve is transplanted, while the native ventricles are preserved. Preserving the native ventricles eliminates the risk of graft ventricular dysfunction and allows for utilization of donor hearts with ventricular dysfunction. Here we outline practical considerations for partial heart transplantation, including indications, sources for donor hearts, graft procurement, graft preservation, implantation, recipient immunosuppression, and reimbursement. This invited expert review is intended to help clinical teams implement partial heart transplantation.

Partial heart transplantation: Growing heart valve implants for children

Heart valves serve a vital hemodynamic function to ensure unidirectional blood flow. Additionally, native heart valves serve biological functions such as growth and self-repair. Heart valve implants mimic the hemodynamic function of native heart valves, but are unable to fulfill their biological functions. We developed partial heart transplantation to deliver heart valve implants that fulfill all functions of native heart valves. This is particularly advantageous for children, who require growing heart valve implants. This invited review outlines the past, present and future of partial heart transplantation.

Partial Heart Transplantation - How to Change the System

Partial heart transplantation is the first clinically successful approach to deliver growing heart valve implants. To date, 13 clinical partial heart transplants have been performed. However, turning partial heart transplantation into a routine procedure that is available to all children who would benefit from growing heart valve implants poses formidable logistical challenges. Firstly, a supply for partial heart transplant donor grafts needs to be developed. This challenge is complicated by the scarcity of donor organs. Importantly, the donor pools for orthotopic heart transplants, partial heart transplants and cadaver homografts overlap. Secondly, partial heart transplants need to be allocated. Factors relevant for equitable allocation include the indication, anatomical fit, recipient clinical status and time on the wait list. Finally, partial heart transplantation will require regulation and oversight, which only recently has been undertaken by the Food and Drug Administration, which regulates human cellular and tissue-based products. Overcoming these challenges will require a change in the system. Once this is achieved, partial heart transplantation could open new horizons for children who require growing tissue implants.