New operations for truncus arteriosus repair using partial heart transplantation: Exploring the surgical design space with 3-dimensional printed heart models

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.

Evaluation of the Efficacy and Accuracy of Super-Flexible Three-Dimensional Heart Models of Congenital Heart Disease Made via Stereolithography Printing and Vacuum Casting: A Multicenter Clinical Trial

Three-dimensional (3D) printing is an advanced technology for accurately understanding anatomy and supporting the successful surgical management of complex congenital heart disease (CHD). We aimed to evaluate whether our super-flexible 3D heart models could facilitate preoperative decision-making and surgical simulation for complex CHD. The super-flexible heart models were fabricated by stereolithography 3D printing of the internal and external contours of the heart from cardiac computed tomography (CT) data, followed by vacuum casting with a polyurethane material similar in elasticity to a child's heart. Nineteen pediatric patients with complex CHD were enrolled (median age, 10 months). The primary endpoint was defined as the percentage of patients rated as "essential" on the surgeons' postoperative 5-point Likert scale. The accuracy of the models was validated by a non-destructive method using industrial CT. The super-flexible heart models allowed detailed anatomical diagnosis and simulated surgery with incisions and sutures. Thirteen patients (68.4%) were classified as "essential" by the primary surgeons after surgery, with a 95% confidence interval of 43.4-87.4%, meeting the primary endpoint. The product error within 90% of the total external and internal surfaces was 0.54 ± 0.21 mm. The super-flexible 3D heart models are accurate, reliable, and useful tools to assist surgeons in decision-making and allow for preoperative simulation in CHD.

The future of partial heart transplantation

Heart valve replacement in children is an unsolved problem in congenital cardiac surgery because state-of-the-art heart valve implants do not grow. This leads to serial repeat operations to replace outgrown heart valve implants. Partial heart transplantation is a new transplant that helps alleviate this problem by delivering growing heart valve implants. In the future, partial heart transplantation has the potential to complement conventional heart transplantation for treating children with congenital cardiac disease primarily affecting the heart valves.

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 Transplant in a Neonate With Irreparable Truncal Valve Dysfunction

Importance

The treatment of neonates with irreparable heart valve dysfunction remains an unsolved problem because there are no heart valve implants that grow. Therefore, neonates with heart valve implants are committed to recurrent implant exchanges until an adult-sized valve can fit.

Objective

To deliver the first heart valve implant that grows.

Design, Setting, and Participants

Case report from a pediatric referral center, with follow-up for more than 1 year. Participants were a recipient neonate with persistent truncus arteriosus and irreparable truncal valve dysfunction and a donor neonate with hypoxic-ischemic brain injury.

Intervention

First-in-human transplant of the part of the heart containing the aortic and pulmonary valves.

Main Outcomes and Measures

Transplanted valve growth and hemodynamic function.

Results

Echocardiography demonstrated adaptive growth and excellent hemodynamic function of the partial heart transplant valves.

Conclusions and Relevance

In this child, partial heart transplant delivered growing heart valve implants with a good outcome at age 1 year. Partial heart transplants may improve the treatment of neonates with irreparable heart valve dysfunction.

Donor supply for partial heart transplantation in the United States

BACKGROUND

Congenital heart disease (CHD) is the most common cause of birth defects worldwide. Valvular defects are a common form of CHDs, and, at this time, treatment options for children with unrepairable valve disease are limited. Issues with anticoagulation, sizing, and lack of growth in valve replacement options can lead to high mortality rates and incidence of reoperations. Partial heart transplantation, or transplantation of fresh valve allografts, has recently been described as a strategy to provide a durable and non-thrombogenic alternative to conventional prostheses and provide growth potential in pediatric patients.

METHODS

The United Network for Organ Sharing (UNOS) database was queried to analyze the number of pediatric donor hearts that were not recovered but had viable valves (n = 3565) between January 2010 and September 2021. Recoverable valves were grouped by donor age: infants (age < 1 year), toddlers (age ≥1 and <3 years), and children (age ≥3 and <18 years). Demographic characteristics of donors were analyzed between age groups.

RESULTS

Infants, toddlers, and children had a total of 344, 465, and 2756 hearts with recoverable valves, respectively, over the study period, representing an average of 29, 39, and 230 hearts with recoverable valves per year.

CONCLUSION

The results of our study identify the minimum donor supply for partial heart transplantation. The actual number is likely higher because it includes hearts not entered in the UNOS database and domino transplants from orthotopic heart transplant recipients. Partial heart transplantation is logistically feasible as there are recoverable valves available for all age groups, fulfilling a clinical need in pediatric patients with unrepairable valve disease.