Partial heart transplantation: Current applications and management

Abstract

Partial heart transplantation (PHT) represents a novel surgical strategy that leverages donor cardiac tissue to address complex congenital and acquired valvar lesions while preserving growth capacity. This narrative review describes the conceptual framework and technical considerations of PHT and reports short-term outcomes across a spectrum of applications based on small observational cohorts and case reports. Early clinical results, predominantly from a single institution, demonstrate favorable valve function, promising growth, and few complications. We outline key elements of pre-transplant evaluation, donor selection, and surgical technique, and discuss post-transplant outcomes, immunosuppression management, long-term potential, and unresolved aspects of immunosuppression and long-term outcomes to inform best practices and guide broader adoption of this emerging therapy.

Key Words: Partial heart transplantation; Heart valve diseases; Immunosuppression; Congenital heart defects; Pediatrics

Core Tip: Partial heart transplantation is a promising surgical innovation to treat pediatric heart valve dysfunction. The short-term outcomes are encouraging, demonstrating valvular growth and function with low rate of complications.

INTRODUCTION

Children with valvular heart disease have historically represented a challenging clinical conundrum in pediatric cardiology. Congenital aortic valve disease comprises up to 6% of all congenital heart disease, and other systemic outflow tract anomalies account for at least another 2% of all congenital heart disease[1-3]. Though there are multiple options for heart valve replacement in children, each has specific drawbacks. Mechanical valves are durable but often are too large for younger patients and require anticoagulation. Bioprosthetic valves avoid the need for anticoagulation, but they are similarly size-limited and fail over time due to degeneration. Valved homografts do not require anticoagulation and are not immunogenic, but they do not grow with patients. In fact, up to 44% of all homografts implanted in infants require surgical reintervention within 2 years of implantation[4]. The Ross procedure is an option in aortic valve stenosis, but it is a technically challenging procedure, and the implanted conduit does not grow. The majority of neonates and infants who undergo the Ross procedure require surgical reintervention, typically replacement of the right ventricular outflow tract conduit, in childhood with a median time to reintervention of 6 years[5]. These options all necessitate reintervention as the child grows into adulthood. In the last several years, partial heart transplantation (PHT) has evolved as a new technique to replace heart valves with a living donor valve[6,7]. The promise of this technique is a valve that may grow with the patient; direct comparisons of PHT to the traditional surgical options mentioned above have not yet been performed. Though still in its infancy, this procedure may provide an alternate option for the management of valvular heart disease in pediatrics. There is not yet published data regarding the optimal long-term immunosuppression, durability, and function of these partial heart transplants. The objective of this narrative review is to summarize the theoretic basis, current clinical practice, available outcomes, and future applications of PHT.

METHODOLOGY

A retrospective review of the literature was conducted to identify research relevant to the pre-clinical and clinical basis, the current clinical practice and outcomes, and future directions of PHT. PubMed and Web of Science databases were queried using search terms “partial heart transplant*”, “partial heart”, “living root”, and “living allogenic heart valve”. Only peer-reviewed, English-language results were included, and results were limited to full-length articles published in 2020 or later. Reference review was also utilized to identify additional related articles. Final search date was June 20, 2026. Articles with reported clinical outcomes in humans were prioritized over articles reporting pre-clinical outcomes. Where no evidence was identified and the authors’ institutional practical was deemed pertinent, this was included with clear distinction. The evidence was synthesized in a narrative review format to incorporate the theoretical basis [including pertinent pre-clinical and orthotopic heart transplant (OHT) outcomes], current clinical practice and outcomes, and institutional practice.

DEFINITION AND THEORY

PHT is the implantation of living cardiac tissue, typically a semilunar valve and its associated tissue, into a recipient. Allografts are harvested from a heart that otherwise would not have been allocated for heart transplant. In traditional OHT, the heart valves contained in the allografts grow and continue to function well[8]. This serves as the biological basis for the promise of valve growth and function over time in PHT. If these valves continue to grow and function alongside the patient’s somatic growth, reintervention or valve replacement may be delayed or even rendered unnecessary.

The theoretical basis of valve growth is based on observation of semilunar valves in orthotopic heart transplantation and porcine models of PHT. Heart valves are thought to have a degree of immune privilege, making them less susceptible to inflammatory response and dysfunction when implanted[9]. An observational study of semilunar valve function in OHT recipients demonstrated valve annulus growth with minimal valve dysfunction[8]. Even in standard OHT grafts that experience myocardial rejection, semilunar valve function is typically unaffected[10]. Preclinical porcine models also confirm valve growth and preserved function after implantation[11,12].

HISTORY

The first partial heart transplant in a human was described in 2022 in a neonate with persistent truncus arteriosus and irreparable truncal valve dysfunction[6]. In that case, both an aortic and pulmonary PHT were implanted. Over 12 months following the procedure, both implanted semilunar valves demonstrated annular growth and excellent function. Since that time, interest in and uptake of the procedure has increased, though it is not yet widely adopted. Duke University has performed over 40 partial heart transplants since the first one in 2022 for a variety of indications, and multiple other institutions nationally and internationally have also begun to offer PHT to their patients[13-16].

INDICATIONS

Indications for PHT are broad and still evolving (Table 1). For pediatric patients, PHT should be considered if the benefit of valve growth and self-repair outweighs the risk of immunosuppression[17]. Broadly, any instance of semilunar valve dysfunction or need for replacement may be suitable for PHT. Of particular utility is neonatal and infantile need for semilunar valve replacement, as these patients will experience the most somatic growth over time after surgical repair. Truncus arteriosus is a specific indication well suited for this procedure, as the patient will require at minimum a conduit in the pulmonary position. If the patient also has irreparable truncal valve dysfunction, a PHT can be placed in both the pulmonary and aortic position[7]. Congenital aortic stenosis that is not responsive to balloon angioplasty may be treated with replacement of the disease valve with a living aortic root. Alternatively, a “living Ross” procedure may be considered. This procedure consists of a pulmonary valve autograft in the aortic position akin to a traditional Ross operation, with the addition of a living pulmonary root placed in the pulmonary position[18]. A third indication is tetralogy of Fallot with severe pulmonary stenosis/atresia or absent pulmonary valve, adding a living pulmonary root in the pulmonary position instead of a traditional conduit.

Table 1 Common indications for partial heart transplantation by position.

Aortic position	Pulmonary position
Truncus arteriosus with irreparable truncal valve[6]	Tetralogy of Fallot with pulmonary stenosis/atresia or absent pulmonary valve[7,14]
Critical aortic stenosis[7]	Living Ross procedure[16]
Bicuspid aortic valve with stenosis/insufficiency[14]	Pulmonary valve dysplasia[14]
Left ventricular outflow tract obstruction[7]	Right ventricular outflow tract obstruction requiring valved conduit[7]

Published recommended indications for partial heart transplantation in aortic and pulmonary outflow tracts, divided by specific indication or disease.

Several additional patient-specific factors are worth consideration when determining suitability of PHT. If the risk of future reoperation is deemed to be prohibitively high, PHT may be favored as there is a theoretical benefit of eliminating the need for reoperation. Additionally, patients and providers considering mechanical valve replacement may find the bleeding risk, dietary restrictions, or activity restrictions of anticoagulation too restrictive for quality of life. In these instances, PHT may provide a more acceptable alternative[17].

PRE-TRANSPLANT EVALUATION AND DONOR SELECTION

Evaluation and consideration for PHT is not as extensive as traditional OHT. There are few, if any, absolute contraindications to PHT specifically. Patients and families should be counseled on the risks of immunosuppression and the uncertain long-term outcomes. If immunosuppression is contraindicated for a patient, alternatives to PHT should be strongly considered.

Potential donors should undergo screening with echocardiography to ensure normal valve function prior to transplantation. In contrast to OHT, donor ventricular function is irrelevant in evaluation[7]. Valve size should be appropriate for patient sizes, and patients may tolerate mild oversizing of valves if necessary.

REGULATION AND ORGAN EQUITY

The selection of donors and organ equity for this procedure remains an area of ongoing exploration. Currently, PHT is regulated in the United States by the Food and Drug Administration as human cells, tissues, or cellular or tissue-based products (HCT/Ps)[19]. This contrasts with traditional heart transplantation, which is regulated under the Department of Health and Human Services and the Organ Procurement and Transplantation Network. Through regulation under the HCT/Ps framework, the PHT grafts do not have the same allocation prioritization system as traditional OHT and indeed are regulated entirely independently of OHTs. A national consortium to assist in donor-recipient matching to ensure equity and utility would likely be useful as this procedure grows in popularity[20]. Though some have suggested that regulation similarly to traditional heart transplantation as a vascular composite allograft is more appropriate, the current regulatory framework as HCT/Ps prevents the ethical dilemma of deciding to allocate an available graft to either traditional OHT or PHT[15,21].

Organ equity and availability are of utmost importance. PHT improves organ stewardship and efficiency through the use of both domino hearts and split roots[22]. Domino heart transplantation is a series of procedures that can be utilized starting with patients on the heart transplant waiting list with one or two functional semilunar valves. When those patients undergo OHT, the aortic and/or pulmonary root from the cardiectomy heart may be used for PHT in a second patient[22]. In this case, a heart that otherwise would have been unused may be salvaged for partial heart transplant. A single center review evaluating cardiectomy hearts in OHT recipients for partial heart transplant suggested the majority of these hearts have at least one semilunar valve suitable for transplantation[23]. These otherwise discarded hearts may now be utilized, furthering the OHT donation impact[15].

The split root procedure (Figure 1) maximizes one donor heart that is not viable for conventional OHT. If this heart has two viable roots, they are split up and implanted into two separate recipients[22]. This procedure has the obvious advantage of improving organ availability by using one donor heart for two recipients and has been shown to be successful both within one institution and by splitting the roots between two separate institutions[22].

Figure 1 Partial heart transplantation with split root procedure. Conceptual schematic depicting split-root partial heart transplantation. Illustrated by Megan Llewellyn, MSMI; copyright Duke University; with permission under a CC BY-ND 4.0 License. Citation: Aykut B, Overbey DM, Medina CK, Omer TM, Rajab TK, Ngeve SM, Beckerman Z, Turek JW. Partial Heart Transplantation Promotes Organ Stewardship: Domino Hearts and Split Roots. Ann Thorac Surg Short Rep 2025; 3: 86-91 [PMID: 40098863 DOI: 10.1016/j.atssr.2024.07.033]. Published by Elsevier Inc.[22].

Further, many pediatric hearts evaluated for conventional transplant are not recovered. Approximately 40% of hearts offered for pediatric transplantation are not utilized for reasons including myocardial dysfunction, infection concerns, donor medical comorbidities, size mismatch, and possible ischemia time, among others[24,25]. A significant number of these have viable valves and could be utilized for PHT[26]. Again, in this case, these are hearts not suitable for OHT that might otherwise go unused.

TECHNICAL CONSIDERATIONS

Donor hearts must first be identified that have normal valve function and are of appropriate size for implantation in the recipient. To date, there are not published recommendations regarding optimal size matching between donor and recipient roots, and further work to identify optimal size matching is critical. Our institution’s practice is to accept pulmonary PHTs with a pulmonary valve annulus size from a z score of 0 (which corresponds to the mean valve annular diameter of a healthy child with the same body surface area) to a Z score of +3.0 (which corresponds to a valve annulus measurement 3 standard deviations above the mean of pulmonary valve annular diameters of healthy children with the same body surface area) based on recipient size and aortic roots from equal to recipient size up to 5 mm larger. Upon identification of a donor heart, it is procured in typical fashion and then the partial heart transplant graft (or grafts) is removed from the remainder of the donor heart. The technique for procuring the pulmonary valve and root is similar to the technique used for pulmonary autograft excision in the Ross procedure. Broadly speaking, aortic root procurement is similar, though the anterior leaflet of the mitral valve is removed as well due to its fibrous continuity with the aortic valve. The coronary ostia are also ligated in aortic root procurement[17].

Following procurement, the graft must be preserved until implantation. Unlike orthotopic heart transplantation, primary graft dysfunction is not a concern in PHT due to the preservation of native ventricles and myocardium. Porcine model studies demonstrate that cryopreserved PHT graft tissue retains metabolic activity and growth potential for far longer than standard OHT grafts with cellular viability demonstrated after 7 days in storage[11]. Based on these pre-clinical results, grafts may remain in static cold storage longer than is tolerated for OHT. Increasingly tolerated cold storage times may theoretically widen the catchment area for donor-recipient matching and allow for non-urgent implantation.

Finally, the surgical implantation is technically similar to homograft valve replacement[6]. One advantage of this procedure is the ability to modify the donor graft to fit the needs of the recipient. Variable lengths of main pulmonary artery and aortic root tissue may be procured to uniquely meet the recipient’s needs, depending on underlying anatomy. Though a novel procedure, the PHT procurement, preservation, and implantation are based on existing techniques and do not require significant alterations of skills or techniques for experienced pediatric cardiothoracic surgeons.

IMMUNOSUPPRESSION AND POST-TRANSPLANT CARE

The medical care of patients following PHT remains an area of active investigation. Initially, immunosuppression protocols were based on ABO-incompatible orthotopic heart transplantation and have evolved with increased experience[6]. The most recent published immunosuppression protocol from our institution recommends glucocorticoid induction followed by an initial maintenance phase with mycophenolate and tacrolimus at goal trough levels lower than standard for orthotopic heart transplantation[14]. Partial heart transplants in the aortic position continue mycophenolate for longer duration than those in the pulmonary position and are on oral steroids postoperatively for a short duration due to higher pressures and theoretical risk for wear/injury[14]. After one year, immunosuppression is reduced to tacrolimus monotherapy with goal trough levels 4-8 ng/mL for both aortic and pulmonary PHTs[14]. Table 2 outlines the key similarities and differences of immunosuppression based on root position. No comparative effectiveness trial of different immunosuppression regimens and their effect on valve function have been completed to date.

Table 2 Immunosuppression for partial heart transplantation[14].

	Aortic position	Pulmonary position
Intraoperative immunosuppression	Yes	Yes
Postoperative steroids	Yes	No
Mycophenolate	1 year	4-8 weeks
Tacrolimus	Indefinitely	Indefinitely

Institutional immunosuppression protocol reported by Overbey et al[14] for immunosuppression divided by implanted valve position.

The long-term requirement for immunosuppression in these patients remains uncertain. There is evidence that heart valves exhibit immune privilege, and, in cases of orthotopic heart transplantation with rejection, the semilunar valves are spared[9,10]. Thus, more data and long-term follow-up is required to determine the need for long-term immunosuppression. Interestingly, one reported patient required discontinuation of immunosuppression due to infection unrelated to the PHT operation. In follow up, the PHT semilunar valve continues to demonstrate growth and normal function nearly 2 years later[14,15].

These patients are monitored serially with clinical examination, laboratory evaluation, electrocardiogram, and echocardiogram following PHT in collaboration with a primary cardiologist and a transplant cardiologist.

OUTCOMES

Reported outcomes following PHT are generally favorable, though limited by the small number of patients who have undergone the procedure, the small number of institutions currently performing PHT, and the relative newness of this surgical technique. Table 3 characterizes the published case reports and cohorts describing PHT. The largest reported cohort of PHT includes 19 patients at our institution[14]. These results demonstrate statistically significant semilunar valve annular growth (P < 0.001 for aortic and pulmonary valve, P = 0.004 for pulmonary valves alone) and leaflet length change (P < 0.001 for aortic and pulmonary valve, P = 0.004 for pulmonary valves alone) as well as subjectively acceptable function of the implanted valves by echocardiography with no significant stenosis or regurgitation in short-term follow up[14]. These findings of annular growth and leaflet length change suggest true valve growth rather than isolated annular dilation with no adverse effects on valve function. In this cohort, complications included one patient who developed mediastinitis from an unrelated operation, one patient who developed a respiratory Group B Streptococcus infection, and 2 patients who developed kidney injury requiring modulation of immunosuppression. One patient required balloon angioplasty of the branch pulmonary arteries and subsequent reoperation for calcification and stenosis of a cryopreserved homograft tissue patch that was added as a hood in the right ventricular outflow tract at the time of PHT in the pulmonary position, though the PHT tissue appeared viable at the time of reoperation[14]. Figure 2 demonstrates preoperative and postoperative echocardiogram findings of a neonate with truncus arteriosus and an irreparable truncal valve who underwent partial heart transplant in both the aortic and pulmonary positions.

Figure 2 Echocardiographic findings before and after partial heart transplantation in a neonate with truncus arteriosus and an irreparable truncal valve, which are representative of this patient. A: Apical image of the truncal valve (white arrow) in late diastole demonstrating qualitatively severe insufficiency (orange jet); B: Apical image of the surgically implanted partial heart on postoperative day 7 with aortic valve (white arrow) in the aortic position in late diastole demonstrating qualitatively trivial insufficiency (red jet). Informed consent was obtained for use of anonymized images.

Table 3 Reported partial heart transplantation patient cohorts.

Ref.	Number of patients	Center	Patient ages (years)	Root position	Follow-up duration reported	Clinical outcomes reported	Reoperation (%)	Potential cohort overlap	Adverse events
Wacker et al[16], 2026	1	Geneva University Hospitals	12	Aortic and pulmonary	Not reported	Valve function	0	No	None reported
Kesseli et al[18], 2025	1	Duke University	3	Pulmonary	12 days	Valve function	0	Yes (Turek et al[6])	Headache due to tacrolimus
Turek et al[6], 2024	1	Duke University	0	Aortic and pulmonary	1 year	Valve function and growth	0	Yes (Kesseli et al[18], Overbey et al[14])	None reported
Kalfa et al[13], 2025	2	Columbia University	0-3	Aortic and pulmonary	15-17 months	Valve function and growth, immunosensitization	0	No	None reported
Overbey et al[14], 2025	19	Duke University	0-adult (oldest in 30-35 years old age range)	Aortic and pulmonary	11-154 weeks	Valve function and growth	10.50	Yes (Turek et al[6])	Infection, postoperative arrhythmia, reoperation kidney injury

Published case reports, case series, and cohort study include short-term follow-up and information on clinical outcomes and adverse effects. There were no reported deaths in any of the above cohorts.

A smaller case series of 2 patients from Columbia University demonstrated similar valve growth and function, though one patient progressed to mild-moderate valve regurgitation over the follow-up period[13]. Interestingly, both of these patients developed human leukocyte antigen class I/II donor-specific antibodies (DSAs) with low mean fluorescence intensity but donor-derived cell-free DNA (cfDNA) levels remained clinically insignificant[13]. To date, the clinical implications of DSAs and cfDNA have not been evaluated in this small population.

The reported in vivo outcomes are inherently limited by small sample sizes and lack of long-term outcomes due the novelty of this procedure. Published outcome data is descriptive, not comparative, in nature which limits generalizability. As with the development and implementation of any new procedure, there is risk of selection bias in patients undergoing PHT. Due to the limited evidence with small case series and case reports with overlapping cohorts, no definitive conclusions can be drawn, and the risk of bias is present. At this time, PHT is limited to several centers and is not widely available. This necessarily limits procedural access geographically and limits both reported outcomes as well as generalizability. Despite these limitations, there is early suggestion of encouraging results warranting further innovation and evaluation.

LONG-TERM POTENTIAL

Clearly, the long-term outcomes of PHT remain to be seen, though initial experience is encouraging at specialized centers. The early evidence of continued valve growth with somatic growth underpins a hope for decreasing or even eliminating the need for reoperation. Patients have been maintained on less immunosuppression compared to traditional heart transplant recipients, based on the immune privilege of heart valves and lack of valve dysfunction with OHT rejection. The risk of long-term immunosuppression complications, including infection, renal dysfunction, and post-transplant lymphoproliferative disorder is unknown and should be included as a potential risk when counseling families regarding PHT. In the case that immunosuppression must be discontinued due to intolerable complications, the graft may be rendered effectively a homovital homograft akin to what was described in the late 20^th century with adult aortic root replacements[27]. To date, no published cost effectiveness analysis of partial heart transplant relative to other options for valve repair or replacement exists. However, if the need for reintervention and subsequent hospitalization is reduced or eliminated, the long-term cost of PHT may be lower than other therapeutic options, even when accounting for long-term cost of immunosuppression and monitoring. This cost effectiveness analysis, if performed in the future, will aid clinicians and families in determining the optimal procedure when multiple options are clinically reasonable. Continued multicenter follow-up of these patients is essential to determine the safety, efficacy, and complications of the procedure and associated immunosuppression. Further, long-term comparative studies of PHT with traditional surgical alternatives such as valve repair or replacement, homograft implantation, and the Ross operation will allow for identification of the best candidates for PHT relative to its surgical alternatives.

OTHER PHT APPLICATIONS

The scope of PHT has the potential to expand beyond semilunar valve replacement. Atrioventricular valve replacement is a logical extension of the current practice, and porcine models of atrioventricular valve PHT have demonstrated feasibility and growth[28,29]. The surgical technique of managing the subvalvar apparatus remains a challenge; however, one pediatric partial heart atrioventricular valve transplant has been performed to date in the mitral position[15]. Tissue transplantation with the possibility of growth to treat conditions such as pulmonary vein stenosis or pulmonary atresia represents another possible expansion of PHT indications[15,20].

CONCLUSION

PHT, in its early stages, is a promising technique best suited at this time for semilunar valve replacement in the pediatric population. Thus far, short-term follow up of these valves has shown growth and function in vivo following transplantation, with utility in a variety of congenital heart diseases with minimal complications. Theory based on immune privilege of heart valve and OHT experience suggests immunosuppression requirements are decreased compared to OHT, and more data on the host immune response to PHT is needed to ascertain the true long-term requirements for immunosuppression. Domino transplantation and split root transplantation provide maximal organ utility and efficiency without competition for organs that may be used for standard heart transplantation. In time, PHT may shift the paradigm for heart valve dysfunction in pediatrics from a disease with few good options to one with a durable surgical repair option with limited risk, should long-term outcomes prove favorable.