1.Definition and rationale of partial heart transplantation
Partial heart transplantation (PHT) represents an innovative concept within cardiac transplant surgery, designed to provide valvular substitutes capable of growth in pediatric patients. The technique also includes the potential transplantation of other viable structures, such as atrial tissue, for pulsatile support in Fontan circulation.
PHT addresses the urgent need for valve replacement in children while avoiding the multiple reoperations inherent to conventional prostheses. Its biological foundation lies in the principle of growth—transplanted valves maintain the ability to grow and remodel through the preservation of viable cells. This requires meticulous graft management, including ABO compatibility, controlled ischemic times, and appropriate immunosuppression to preserve valve integrity and function during somatic growth.
Several terms have been used to describe the procedure, each emphasizing different aspects:
– Partial heart transplantation: analogous to total heart transplantation, requiring a donor heart, transplant team, and immunosuppression. It is the preferred term in the literature, intuitively reflecting the nature of the intervention.
– Allogeneic cardiac valve transplantation: highlights the allogeneic source of the graft, distinguishing it from autologous procedures such as the Ross operation.
– Living homograft: underscores the biological viability of the implanted tissue, contrasting with cryopreserved or acellular homografts.
2.Advantages of PHT
Unlike total heart transplantation, PHT preserves the native ventricles. This reduces surgical risk, prevents donor ventricular dysfunction, and minimizes postoperative morbidity. It also broadens the potential donor pool, as hearts with impaired ventricular function but intact valves, or domino hearts, may be suitable.
The risk of acute rejection is lower, since the recipient’s native ventricles remain unaffected. Moreover, PHT grafts exhibit superior ischemic tolerance, maintaining viability for several days compared with only a few hours in total transplantation.
3.Limitations of conventional valvular substitutes in children
Pediatric valve replacement faces major anatomical and biological constraints: neonatal valves are extremely small, and currently available implants do not accommodate somatic growth.
Bioprostheses and homografts lack viable cells, cannot grow or self-repair, degenerate rapidly, and often require multiple reoperations, with mortality rates reaching up to 40% in infants with aortic valve replacement.
Mechanical valves require lifelong anticoagulation, with an annual thrombotic or hemorrhagic risk ≥1%, and are contraindicated in the pulmonary position.
The Ross procedure, while biological, is complex, carries significant mortality, and is feasible only when the pulmonary valve is normal. It also entails dual valvular risk: aortic (dilatation of the pulmonary autograft under systemic pressure) and pulmonary (repeat reoperations due to lack of growth of the replacement valve).
PHT thus emerges as a biological alternative capable of growth, self-repair, and long-term durability without the risks of anticoagulation or repeated reintervention.
A comparison between PHT and conventional prosthetic substitution (homograft) is summarized below:
| Characteristic | Partial heart transplantation (PHT) | Homograft |
| Donor type | Organ donor with viable tissue and intact circulation (ICU) | Cadaveric tissue donor from tissue bank with early cellular necrosis |
| ABO typing | Required to maintain viability and prevent rejection | Not required, as the tissue is acellular |
| Recipient immunosuppression | Required to preserve functional graft cells | Not required due to minimal immunogenicity |
| Preservation time | Days, under controlled cold ischemia | Years, through long-term cryopreservation |
4.Indications for PHT
PHT is indicated when the potential benefits of valvular growth and self-repair outweigh the risks associated with immunosuppression.
- Primary indication: infants requiring replacement of the systemic semilunar valve and unsuitable for the Ross procedure.
Specific conditions include:
– Truncus arteriosus
– Congenital aortic stenosis
– Pulmonary atresia
– D-transposition of the great arteries with left ventricular outflow tract obstruction - Fontan assistance: transplantation of atrial tissue for pulsatile support.
- Other indications: pediatric patients for whom mechanical or bioprosthetic complications are to be avoided.
COMMENTARY:
This review presents partial heart transplantation as a paradigm shift in pediatric cardiac surgery, based on the selective transplantation of viable tissue capable of growth and self-repair. Its essence lies in preserving native ventricular function, optimizing clinical outcomes, and expanding donor utilization. PHT offers a biological, durable solution that reduces infant mortality, prevents successive reoperations, and makes better use of available donor hearts.
Despite its promise, PHT remains an emerging technique facing regulatory, logistical, and technical challenges. From a regulatory standpoint, there is still no established legal framework or allocation policy.
Logistically, donor procurement remains a critical issue. Hearts excluded from total transplantation due to ventricular dysfunction could be utilized if valve morphology is preserved. Furthermore, domino transplantation—using the explanted heart from a total transplant recipient as a partial graft—significantly increases donor availability.
Technically, graft retrieval requires careful handling to maintain cellular viability, with multiple viable grafts obtainable from a single heart. Cold storage preserves functionality for several days, and advances in cryopreservation could further extend graft availability. Implantation techniques resemble those used for homografts, facilitating adoption by experienced surgical teams. Immunosuppression follows standard pediatric transplant protocols, although native ventricular preservation limits the functional consequences of rejection. Emerging noninvasive monitoring tools—such as donor-derived cell-free DNA and gene expression profiling—are being explored, as endomyocardial biopsy is not feasible in this context.
According to the IDEAL framework (Idea, Development, Exploration, Assessment, and Long-term Study), PHT is currently in the developmental phase. Future efforts should focus on prospective multicenter studies, standardized quality indicators, comparative outcomes versus the Ross procedure and other substitutes, and long-term registry data.
Research directions include expanding indications to atrioventricular and atrial tissues, optimizing preservation to create “ready-to-use” grafts, enhancing immune monitoring, and minimizing immunosuppressive burden.
In conclusion, partial heart transplantation represents a biological and surgical innovation that merges immunologic, logistical, and functional advantages. Rooted in the principles of total heart transplantation but offering distinct benefits, it may redefine the long-term management of pediatric valvular disease: a living, adaptable, and durable valve. Its success will depend on institutional collaboration, clear donation and preservation protocols, and safe strategies for immunosuppression and follow-up.
REFERENCE:
Rajab TK, Kalfa DM, Mery CM, Emani SM, Reemtsen BL. Indications and Practical Considerations for Partial Heart Transplantation. Ann Thorac Surg. 2025 Oct;120(4):620-630. doi: 10.1016/j.athoracsur.2025.01.037.
