Changing indications for pediatric heart transplantation: complex congenital heart disease

Mechanical circulatory support in patients with congenital heart disease: a European Registry for Patients with Mechanical Circulatory Support (EUROMACS) study

OBJECTIVES

This study aims to explore characteristics and clinical outcomes of patients with congenital heart disease (CHD) in the European Registry for Patients with Mechanical Circulatory Support (EUROMACS).

METHODS

This is a retrospective study of EUROMACS participants receiving MCS as bridge-to-transplant, possible bridge-to-transplant, or rescue therapy/bridge-to-recovery from 2011 to 2023 (n = 5340). Adult and paediatric cohorts were analysed separately. The primary outcome was mortality on MCS; secondary outcomes included recovery, transplant and complications including bleeding, cerebrovascular events, and sepsis.

RESULTS

Among adult patients, mortality at 1-year was 33.3% among the CHD cohort vs 22.1% in the non-CHD cohort. Adult CHD patients had higher hazards of mortality within the first year after MCS implantation [hazard ratios 1.98, 95% confidence interval (CI) 1.35-2.91, P < 0.001] and bleeding events (subdistribution hazard ratios 2.10, 95% CI 1.40-3.16, P < 0.001) compared with non-CHD patients. Both associations remained significant after accounting for multiple mediators. Among paediatric patients, mortality at 1 year was 22.1% in the CHD cohort vs 17.3% in the non-CHD cohort (hazard ratios 1.39, 95% CI 0.83-2.32, P = 0.213).

CONCLUSIONS

Adult and paediatric patients with CHD on MCS have higher adverse event risk compared with non-CHD MCS patients, though children did not have greater risk of mortality. As the number of CHD patients requiring advanced heart failure management continues to grow, these findings can enhance informed decision-making.

CLINICAL TRIAL REGISTRATION NUMBER

Registry name: EUROMACS.

Echocardiographic assessment of pediatric heart transplantation: A single-center experience in China

BACKGROUND

Pediatric heart transplant (HT) has become the standard of care for end-stage heart failure in children worldwide. Serial echocardiographic evaluations of graft anatomy and function during follow-up are crucial for post-HT management. However, evolution of cardiac structure and function after pediatric HT has not been well described, especially during first year post-HT. This study aimed to characterize the evolution of cardiac structure and function after pediatric HT and investigate the correlation between biventricular function with adverse clinical outcomes.

METHODS

A single-center retrospective study of echocardiographic data obtained among 99 pediatric HT patients was conducted. Comprehensive echocardiographic examination was performed in all patients at 1-, 3-, 6-, 9- and 12-months post-HT. We obtained structural, functional and hemodynamic parameters from both left- and right-side heart, such as left ventricular stroke volume (LVSV), left ventricular ejection fraction (LVEF), right ventricular fractional area change (RVFAC), etc. The cardiac evolution of pediatric HT patients during first post-HT year was described and compared between different time points. We also explored the correlation between cardiac function and major adverse transplant events (MATEs).

RESULTS

1) Evolution of left heart parameters: left atrial length, mitral E velocity, E/A ratio, LVSV and LVEF significantly increased while mitral A velocity significantly decreased over the first year after HT (P < .05). Compared with 1 month after HT, interventricular septum (IVS) and left ventricular posterior wall (LVPW) decreased at 3 months but increased afterwards. (2) Evolution of right heart parameters: right ventricular base diameter and mid-diameter; right ventricular length diameter, tricuspid E velocity, E/A ratio, tricuspid annular velocity e' at free wall, and RVFAC increased, while tricuspid A velocity decreased over the first year after HT (P < .05). (3) Univariate logistic regression model suggests that biventricular function parameters at 1-year post-HT (LVEF, RVFAC, tricuspid annular plane systolic excursion and tricuspid lateral annular systolic velocity) were associated with MATEs.

CONCLUSION

Gradual improvement of LV and RV function was seen in pediatric HT patients within the first year. Biventricular function parameters associated with MATEs. The results of this study pave way for designing larger and longer follow-up of this population, potentially aiming at using multiparameter echocardiographic prediction of adverse events.

Research Gaps in Pediatric Heart Failure: Defining the Gaps and Then Closing Them Over the Next Decade

Given the numerous opportunities and the wide knowledge gaps in pediatric heart failure, an international group of pediatric heart failure experts with diverse backgrounds were invited and tasked with identifying research gaps in each pediatric heart failure domain that scientists and funding agencies need to focus on over the next decade.

Heart transplantation surgery in children and young adults with congenital heart disease

BACKGROUND

Pediatric cardiac transplantation remains a surgical challenge as a variety of cardiac and vessel malformation are present in patients with congenital heart disease (CHD). Despite limited availability and acceptability of donor hearts, the number of heart transplantations remains on a stable level with improved survival and quality of life.

OBSERVATION

As treatment options for CHD continue to improve and the chances of survival increase, more adult CHD patients are listed for transplantation. This review focuses on the clinical challenges and modified techniques of pediatric heart transplantations.

CONCLUSION

Not only knowledge of the exact anatomy, but above all careful planning, interdisciplinary cooperation and surgical experience are prerequisites for surgical success.

Morbidity and Mortality of Heterotopic Partial Heart Transplantation in Rodent Models

Unrepairable congenital heart valve disease is an unsolved problem in pediatric cardiac surgery because there are no growing heart valve implants. Partial heart transplantation is a new type of transplant that aims to solve this problem. In order to study the unique transplant biology of partial heart transplantation, animal models are necessary. This study aimed to assess the morbidity and mortality of heterotopic partial heart transplantation in rodent models. This study assessed two models. The first model involved transplanting heart valves from donor animals into the abdominal aortic position in the recipient animals. The second model involved transplanting heart valve leaflets into the renal subcapsular position of the recipient animals. A total of 33 animals underwent heterotopic partial heart transplantation in the abdominal aortic position. The results of this model found a 60.61% (n = 20/33) intraoperative mortality rate and a 39.39% (n = 13/33) perioperative mortality rate. Intraoperative mortality was due to vascular complications from the procedure, and perioperative mortality was due to graft thrombosis. A total of 33 animals underwent heterotopic partial heart transplantation in the renal subcapsular position. The results of this model found a 3.03% (n = 1/33) intraoperative mortality rate, and the remaining 96.97% survived (n = 32/33). We conclude that the renal subcapsular model has a lower mortality rate and is technically more accessible than the abdominal aortic model. While the heterotopic transplantation of valves into the abdominal aortic position had significant morbidity and mortality in the rodent model, the renal subcapsular model provided evidence for successful heterotopic transplantation.

Long-Term Risk of Heart Failure-Related Death and Heart Transplant After Congenital Heart Surgery in Childhood (from the Pediatric Cardiac Care Consortium)

We aimed to describe the longitudinal risk of advanced heart failure (HF) leading to death, heart transplantation, or ventricular assist device (VAD) placement after congenital heart surgery (CHS) and how it varies across the spectrum of congenital heart disease. We linked the records of patients who underwent first CHS in the Pediatric Cardiac Care Consortium between 1982 and 2003 with the United States National Death Index and Organ Procurement and Transplantation Network databases. Primary outcome was time from CHS discharge to HF-related death, heart transplant, or VAD placement, analyzed with proportional hazards models accounting for competing mortality. In 35,610 patients who survived a first CHS, there were 799 HF deaths, transplants, or VADs over a median of 23 years (interquartile range, 19 to 27). Cumulative incidence at 25 years was 2.3% (95% confidence interval [CI] 2.1% to 2.4%). Compared to mild 2-ventricle defects, the adjusted subhazard ratio for moderate and severe 2-ventricle defects was 3.21 (95% CI 2.28 to 4.52) and 9.46 (95% CI 6.71 to 13.3), respectively, and for single-ventricle defects 31.8 (95% CI 22.2 to 45.6). Systemic right ventricle carried the highest risk 2 years after CHS (subhazard ratio 2.76 [95% CI 2.08 to 3.68]). All groups had higher rates of HF-related death compared with the general population (cause-specific standardized mortality ratio 56.1 [95% CI 51.0 to 61.2]). In conclusion, the risk of advanced HF leading to death, transplantation, or VAD was high across the spectrum of congenital heart disease. While severe defects carry the highest risk, those with mild disease are still at greater risk than the general population.

Attitudes to Cardiac Xenotransplantation by Pediatric Heart Surgeons and Physicians

Background:

Cardiac transplantation in early childhood is limited by scarcity of organ donors. Advances in cardiac xenotransplantation (XTx) research suggest that xenografts may one day represent an alternative to allografts. We sought to determine the attitudes among surgeons and cardiologists in the field of pediatric cardiac transplantation toward the potential use of XTx if this clinical option were to become a reality.

Methods:

A Likert-scale anonymous survey addressing the use of XTx in pediatric patients was sent to members of the Congenital Heart Surgeons (CHS) Society and the Pediatric Heart Transplant Society. Results were described and compared between the two surgeon/physician groups.

Results:

Ninety-two CHS and 42 pediatric transplant cardiologists (PTC) responded (N = 134). The potential acceptance of XTx was high in both groups, assuming risks and results were similar to those of cardiac allotransplantation (88% CHS vs 81% PTC; P = .07). When asked if they would recommend a xenograft, if the results were anticipated to be inferior to those of cardiac allotransplantation, as a bridge to a human heart, potential acceptance fell dramatically but remained higher among CHS than PTC (41% vs 17%, p 0.02). Approximately only one-third of CHS and half of PTC preferred primary cardiac XTx for hypoplastic left heart syndrome if there was no waitlist time and had similar outcomes to allotransplantation.

Conclusions:

Our findings suggest that potential acceptance of XTx by CHS and PTC would not be a major barrier if XTx demonstrated similar outcomes to allotransplantation. Acceptance by other congenital heart stakeholders remains to be investigated.

Update on pediatric heart failure

PURPOSE OF REVIEW

This review highlights recent advances in the diagnosis and management of children with heart failure. We emphasize the clinical approach to patient care in the areas of acute decompensated heart failure, chronic heart failure, and failure of the patient with single ventricle physiology.

RECENT FINDINGS

Important guidelines regarding the recognition and management of heart failure in children have been proposed and adopted, providing guidance for early recognition and ongoing management. Early diuresis, and avoidance of excessive inotropic agent use, in favor of milrinone as an inotropic-vasodilator agent, are emphasized. Close monitoring of airway pressures to improve ventricular filling, and extubation to positive pressure or high-flow nasal cannula therapy are also important. Chronic heart failure therapy requires combination treatment with diuretics, and the three major classes of drugs. Management of the failing Fontan requires attention to the hepatic, pulmonary and lymphatic circulations.

SUMMARY

Improved outcomes in children with heart failure are possible. Inherent in this success is the engagement of an interdisciplinary team-based approach to care, with early recognition and escalation of care for specific patients who are not improving as predicted.

The Case for Cardiac Xenotransplantation in Neonates: Is Now the Time to Reconsider Xenotransplantation for Hypoplastic Left Heart Syndrome?

Neonatal cardiac transplantation for hypoplastic left heart syndrome (HLHS) is associated with excellent long-term survival compared to older recipients. However, heart transplantation for neonates is greatly limited by the critical shortage of donor hearts, and by the associated mortality of the long pre-transplant waiting period. This led to the development of staged surgical palliation as the first-line surgical therapy for HLHS. Recent advances in genetic engineering and xenotransplantation have provided the potential to replicate the excellent results of neonatal cardiac allotransplantation while eliminating wait-list-associated mortality through genetically modified pig-to-human neonatal cardiac xenotransplantation. The elimination of the major pig antigens in addition to the immature B-cell response in neonates allows for the potential to induce B-cell tolerance. Additionally, the relatively mature neonatal T-cell response could be reduced by thymectomy at the time of operation combined with donor-specific pig thymus transplantation to "reprogram" the host's T-cells to recognize the xenograft as host tissue. In light of the recent significantly increased graft survival of genetically-engineered pig-to-baboon cardiac xenotransplantation, we propose that now is the time to consider devoting research to advance the potential clinical application of cardiac xenotransplantation as a treatment option for patients with HLHS. Employing cardiac xenotransplantation could revolutionize therapy for complex congenital heart defects and open a new chapter in the field of pediatric cardiac transplantation.

Variations in Criteria and Practices for Heart Transplantation Listing Among Pediatric Transplant Cardiologists

Ethical issues in pediatric heart transplantation (Htx) include resource allocation, benefit, and burden assessment in high-risk recipients, and informed consent. Practice patterns and decision-making was investigated using an internet survey with 47-multiple choice items and vignette-based questions. Of 43 pediatric Htx cardiologists contacted, 28 (65%) responded. Respondents reported that an overall median 1-month survival of 73% (range 50-100%), 1-year survival of 70% (range 50-85%), 5-year survival of 50% (range 40-85%), and 10-year survival of 50% (range 25-85%) was adequate to offer Htx. Based on vignettes presented, 100% of those surveyed would offer Htx to a straightforward 12-year old with end-stage dilated cardiomyopathy and a 7-year old with hypoplastic left heart syndrome with protein losing enteropathy. Thirty percent of physicians would offer Htx to a patient status post a Fontan procedure with mutliple co-morbidities. Seventy-five percent of physicians would offer Htx despite proven non-adherence. Considerable variability exists in the practice patterns of pediatric heart transplant cardiologists with regards to decision-making while evaluating patients for listing. Disagreements among pediatric Htx cardiologists exist when there are concerns for non-adherence and associated multiple co-morbidities. Further work is needed to understand these variations and develop consensus for pediatric Htx organ allocation.

An approach to induction of tolerance to pig cardiac xenografts in neonates

There is a continuing need for donor hearts for infants with complex congenital heart defects. The transplantation of hearts from neonatal pigs would be an alternative to human organs, particularly if donor-specific immunological tolerance could be achieved. The great majority of infant humans do not make natural (preformed) antibodies against triple-knockout (TKO) pigs (that do not express any of the three known pig antigens against which humans have natural anti-pig antibodies). The transplantation of a heart from a TKO pig into an infant would therefore minimize any risk of early antibody-mediated rejection, and, with adequate immunosuppressive therapy, prolonged graft survival may well be achieved. Total host thymectomy (commonly carried out at the time of orthotopic heart transplantation in this age group) ± residual T-cell depletion and donor-specific pig thymus tissue transplantation might induce T-cell tolerance and allow immunosuppressive therapy to be discontinued (if there is in vitro evidence of T-cell and B-cell nonresponsiveness to donor-specific pig cells). Even if tolerance were not achieved, with continuing immunosuppressive therapy, the graft would likely "bridge" the patient until a suitable allograft became available or be associated with prolonged xenograft function.

Heart transplantation for adults with congenital heart disease: current status and future prospects

Increased survival rates after corrective or palliative surgery for complex congenital heart disease (CHD) in infancy and childhood are now being coupled with increased numbers of patients who survive to adulthood with various residual lesions or sequelae. These patients are likely to deteriorate in cardiac function or end-organ function, eventually requiring lifesaving treatment including heart transplantation. Although early and late outcomes of heart transplantation have been improving for adult survivors of CHD, outcomes and pretransplant management could still be improved. Survivors of Fontan procedures are a vulnerable cohort, particularly when single ventricle physiology fails, mostly with protein-losing enteropathy and hepatic dysfunction. Therefore, we reviewed single-institution and larger database analyses of adults who underwent heart transplantation for CHD, to enable risk stratification by identifying the indications and outcomes. As the results, despite relatively high early mortality, long-term results were encouraging after heart transplantation. However, further investigations are needed to improve the indication criteria for complex CHD, especially for failed Fontan. In addition, the current system of status criteria and donor heart allocation system in heart transplantation should be arranged as suitable for adults with complex CHD. Furthermore, there is a strong need to develop ventricular assist devices as a bridge to transplantation or destination therapy, especially where right-sided circulatory support is needed.

Current challenges in pediatric heart transplantation for congenital heart disease

PURPOSE OF REVIEW

Pediatric heart transplantation is an established therapy for end-stage cardiac disease without suitable medical or surgical options. However, transplantation for congenital heart disease carries an incremental risk that challenges the pediatric transplant team on multiple levels.

RECENT FINDINGS

With improved outcomes following palliative and corrective congenital cardiac surgery, cardiac transplantation has decreased in recent years as a primary therapy. Nevertheless, congenital heart disease remains the most common indication for cardiac transplantation during infancy. Primary transplantation in infancy is selectively recommended for severe systemic ventricular dysfunction, severe atrioventricular valve insufficiency, and occlusive coronary artery anomalies, particularly with single ventricle physiology. Wait-list mortality remains highest for infants with prior palliative surgery and patients with failing Fontan physiology, both of whom have limited options for effective mechanical circulatory support. The sensitized patient carries an increased risk with prolonged wait times, although virtual cross-matches and single bead assays for donor-specific antigens have facilitated the transplant process. Early and late survival after transplantation for congenital heart disease remain inferior to cardiomyopathy, with prior Fontan procedure as a major risk factor. However, among survivors at 6 months, late outcomes are generally excellent. Major late causes of death include allograft vasculopathy, post-transplant lymphoproliferative disease, and acute rejection. Noncompliance with medications remains a major risk for teenage mortality.

SUMMARY

Despite the myriad of evolving challenges, pediatric heart transplantation for congenital heart disease enjoys routine short and long-term success at experienced centers for the vast majority of such patients without other options.

Stem cell therapy and tissue engineering for correction of congenital heart disease

This review article reports on the new field of stem cell therapy and tissue engineering and its potential on the management of congenital heart disease. To date, stem cell therapy has mainly focused on treatment of ischemic heart disease and heart failure, with initial indication of safety and mild-to-moderate efficacy. Preclinical studies and initial clinical trials suggest that the approach could be uniquely suited for the correction of congenital defects of the heart. The basic concept is to create living material made by cellularized grafts that, once implanted into the heart, grows and remodels in parallel with the recipient organ. This would make a substantial improvement in current clinical management, which often requires repeated surgical corrections for failure of implanted grafts. Different types of stem cells have been considered and the identification of specific cardiac stem cells within the heterogeneous population of mesenchymal and stromal cells offers opportunities for de novo cardiomyogenesis. In addition, endothelial cells and vascular progenitors, including cells with pericyte characteristics, may be necessary to generate efficiently perfused grafts. The implementation of current surgical grafts by stem cell engineering could address the unmet clinical needs of patients with congenital heart defects.