Partial heart transplantation (PHT) has emerged as a pioneering approach for treating infants with irreparable heart valve dysfunction. However, the scarcity of suitable donors presents a significant bottleneck to its widespread application. This study introduces and evaluates the novel use of domino and split-root procedures within PHT. We describe 6 pediatric cardiac patients who underwent either domino or split-root PHT at our institution. From May to August 2023, our team successfully executed 3 domino and 3 split-root PHTs, including 1 procedure that involved interinstitutional collaboration. These cases highlight the procedural feasibility and the potential for broader application. The implementation of PHT represents a significant advance in pediatric heart care. Domino and split-root techniques within the PHT framework have the potential to substantially increase both donor availability and recipient capacity. These strategies usher in a new era of organ stewardship through addressing the challenge of donor organ shortage.

The gut microbiome has been shown to play a significant role in solid organ transplantation, potentially influencing graft function and patient outcomes. Dysbiosis, characterized by reduced microbial diversity and an increase in pathogenic taxa, has been linked to higher incidences of allograft rejection, graft dysfunction, and post-transplant mortality. Several studies suggest that the gut microbiome might be able to serve as both a biomarker and a therapeutic target, potentially guiding personalized immunosuppressive therapies and other interventions to improve outcomes after solid organ transplantation. As summarized in this review, clinical studies have shown that specific microbial shifts correlate with adverse outcomes, including acute rejection and chronic allograft dysfunction. As research surrounding the relationship between the gut microbiome and solid organ transplant progresses, the integration of microbial analysis into clinical practice has the potential to revolutionize post-transplant care, offering new avenues to improve graft survival and patient quality of life. This review aims to provide a comprehensive overview of the relationship between gut microbial dysbiosis and transplantation outcomes, emphasizing the impact on kidney, liver, lung, and heart transplant recipients.

Partial heart transplantation is a new approach to deliver growing heart valve implants. Partial heart transplants differ from heart transplants because only the part of the heart containing the necessary heart valve is transplanted. This allows partial heart transplants to grow, similar to the valves in heart transplants. However, the transplant biology of partial heart transplantation remains unexplored. This is a critical barrier to progress of the field. Without knowledge about the specific transplant biology of partial heart transplantation, children with partial heart transplants are empirically treated like children with heart transplants because the valves in heart transplants are known to grow. In order to progress the field, an animal model for partial heart transplantation is necessary. Here, we contribute our surgical protocol for partial heart transplantation in growing piglets. All aspects of partial heart transplantation, including the donor procedure, the recipient procedure, and recipient perioperative care are described in detail. There are important nuances in the conduct of virtually all aspects of open heart surgery that differs in piglets from humans. Our surgical protocol, which is based on our experience with 34 piglets, will allow other investigators to leverage our experience to seek fundamental knowledge about the nature of partial heart transplants. This is significant because the partial heart transplant model in piglets is complex and very resource intensive.

Implantation of cultured allogeneic thymus tissue (CTTI) into athymic human recipients generates functional recipient-derived naïve T cells that are tolerant to donor. Currently, CTTI is always performed with 12 - 21 days of thymus procurement to avoid culture-related changes that could be detrimental to its reconstitution potential. We demonstrate here that cultured thymus tissue can be cryopreserved and still maintain its viability and reconstitution potential. Implantation of cryopreserved cultured rat thymus tissue (cCTTI) under the renal capsule of congenitally athymic rats results in colonization of the thymus implant with T cell progenitors and population of the periphery with genetically-recipient naïve T cells. Similarly, cCTTI of porcine thymus into the quadriceps muscle of thymectomized T cell-depleted pigs results in full reconstitution of the implanted thymus. Human thymus tissues that are similarly cultured and cryopreserved continue to meet the same implantation quality criteria as freshly cultured thymus tissue. Clinical trials are warranted to test the potential of cCTTI to decouple the current links between time of procurement and implantation. This would extend the benefits of immune reconstitution and tolerance induction to a broader range of patients.

Background: This study describes the illness burden in the first year of life for children with single-ventricle heart disease, using the metric of days alive and out of hospital to characterize morbidity and mortality.Methods: This is a retrospective single-centre study of single-ventricle patients born between 2005 and 2021 who had their initial operation performed at our institution. Patient demographics, anatomical details, and hospitalizations were extracted from our institutional single-ventricle database. Days alive and out of hospital were calculated by subtracting the number of days hospitalized from number of days alive during the first year of life. A multivariable linear regression with stepwise variable selection was used to determine independent risk factors associated with fewer days alive and out of hospital.Results: In total, 437 patients were included. Overall median number of days alive and out of hospital in the first year of life for single-ventricle patients was 278 days (interquartile range 157–319 days). In a multivariable analysis, low birth weight (<2.5kg) (b = −37.55, p = 0.01), presence of a dominant right ventricle (b = −31.05, p = 0.01), moderate-severe dominant atrioventricular valve regurgitation at birth (b = −37.65, p < 0.05), index hybrid Norwood operation (b = −138.73, p < 0.01), or index heart transplant (b = −158.41, p < 0.01) were all independently associated with fewer days alive and out of hospital.Conclusions: Children with single-ventricle heart defects have significant illness burden in the first year of life. Identifying risk factors associated with fewer days alive and out of hospital may aid in counselling families regarding expectations and patient prognosis.