Outcomes of heart transplantation in children with previously palliated hypoplastic left heart syndrome

OBJECTIVES

Paediatric heart transplantation in children who fail multistage palliation for hypoplastic left heart syndrome is associated with challenges related to immune, clinical or anatomic risk factors. We review current outcomes and risk factors for survival following heart transplantation in this challenging patient population.

METHODS

The United Network for Organ Sharing transplantation database was merged with Paediatric Health Information System database to identify children who received heart transplantation following prior palliation for hypoplastic left heart syndrome. Multivariable Cox analysis of outcomes and factors affecting survival was performed.

RESULTS

Our cohort included 849 children between 2009 and 2021. The median age was 1044 days (interquartile range 108-3535), and the median weight was 13 kg (interquartile range 7-26). Overall survival at 10 years following heart transplantation was 71%, with most of the death being perioperative. On multivariable analysis, risk factors for survival included Black race (hazard ratio = 1.630, P = 0.0253), blood type other than B (hazard ratio = 2.564, P = 0.0052) and male donor gender (hazard ratio = 1.367, P = 0.0483). Recipient age, the use of ventricular assist device or extracorporeal membrane oxygenation were not significantly associated with survival. Twenty-four patients underwent retransplantation, and 10-year freedom from retransplantation was 98%. Rejection before hospital discharge and within 1 year from transplantation was 20% and 24%, respectively, with infants having lower rejection rates.

CONCLUSIONS

Compared with existing literature, the number of children with prior hypoplastic left heart syndrome palliation who receive heart transplantation has increased in the current era. Survival following transplantation in this patient population is acceptable. Most of the death is perioperative. Efforts to properly support these patients before transplantation might decrease early mortality and improve overall survival.

Heart Transplantation after Univentricular Palliation: Improved Outcomes and Increased Complexity

AIM

Heart transplantation (HT) in patients with failing univentricular circulation is often challenging. This is compounded by the ever-increasing number of patients with prior Norwood-type reconstruction of the aorta, large aortic root, and often dense adhesions from multiple prior operations. We aimed to elucidate differences in outcomes of HT in patients with prior univentricular palliations, with and without prior Norwood-type aortic arch reconstruction (ArchRec).

METHODS

All patients who underwent HT for failed univentricular palliation during the 1990-2022 period were included in the study.

RESULTS

Of 45 patients, 18 had undergone ArchRec. Hospital mortality improved in the recent era (17.4% before 2006 vs 0% after 2006; p=0.11), despite a higher proportion of patients with ArchRec (17.4% before 2006 vs 60.8% after 2006, p=0.002). Patients with ArchRec had a higher number of prior cardiac surgeries (4.1±1.5 vs 3.2±1.3, p=0.04), longer cardiopulmonary bypass time (320±23 vs 242±21 min, p=0.02), more concomitant arch reconstruction (33.3% vs 0%, p=0.02), greater need for post-HT extracorporeal membrane oxygenation (33.3% vs 3.7%; p=0.01) and longer hospital stay (37.1±30.5 days vs 23.6±11.8 days, p=0.04). Freedom from death or retransplantation for all patients was 91%, 73%, 67%, and 53% at 1, 5, 10, and 15-years, respectively. Prior ArchRec, Fontan procedure, and earlier eras were not risk factors for death.

CONCLUSIONS

The outcomes of HT after univentricular palliation have improved in recent times and low operative mortality can be achieved. Despite increased complexity, good similar outcomes can be achieved in patients with and without prior arch reconstruction regardless of the palliation stage.

Palliated Hypoplastic Left Heart Syndrome Patients Experience Superior Waitlist and Comparable Post-Heart Transplant Survival to Non-Single Ventricle Congenital Heart Disease Patients

Congenital heart disease (CHD) is a well-established risk factor for inferior waitlist and post-heart transplant survival in children. Differences in outcomes between CHD subgroups are understudied. The present study compared outcomes for palliated hypoplastic left heart syndrome (HLHS) patients to other non-single ventricle CHD (non-SVCHD) and non-CHD patients. United Network for Organ Sharing was used to identify children (age < 18) listed for heart transplant in the United States between 2016 and 2021. CHD sub-diagnoses were only available for United Network for Organ Sharing status 1a after 2015, thereby defining the cohort. Waitlist outcomes were studied using competing-risk time-to-event analysis for transplantation, mortality/decompensation, and alive-on-waitlist. Multivariable Cox proportional hazards regression analyses were used to identify factors associated with inferior post-transplant survival. Patients included: palliated-HLHS (n = 477), non-SVCHD (n = 686), and non-CHD (n = 1261). At listing, Palliated-HLHS patients were older than non-SVCHD (median 2-year [IQR 0-8] vs median 0-year [0-3], respectively) and younger than non-CHD (median 7-year [0-14]) (P < 0.001 vs both), and were more likely to be white (P < 0.01 vs both). Upon time-to-event analysis, rates of waitlist mortality/decompensation rates were greater among non-SVCHD than palliated-HLHS. Post-transplant survival was comparable between palliated-HLHS and non-SVCHD (P = 0.920) but worse compared to non-CHD (P < 0.001). Both palliated-HLHS (HR 2.40 [95% CI 1.68-3.42]) and non-SVSCHD (2.04 [1.39-2.99]) were independently associated with post-transplant mortality. Palliated-HLHS patients with heart failure experience significantly worse post-transplant outcomes than non-CHD but, compared to other CHD patients, experience superior waitlist and comparable post-transplant survival. While a high-risk cohort, HLHS patients can achieve gratifying waitlist and post-transplant survival.

Infants Who Require Total Parenteral Nutrition and Paralytics at Time of Heart Transplant Experience Inferior Post-Transplant Mortality

Background: Infants experience the worst one-year post-heart transplant (HTx) survival of any other pediatric group. Although mechanical ventilatory (MV) requirement at the time of transplant is an established predictor of post-transplant mortality, the impacts of commonly co-utilized support modalities such as total parenteral nutrition (TPN)-dependence and paralytics are understudied. Methods: All infant HTx recipients from 2003 to 2020 in both the United Network for Organ Sharing and Pediatric Health Information System databases were identified (n = 1344) and categorized depending upon support requirement at the time of transplant—none (59%), MV-only (10%), MV + Paralytics (2%), TPN-dependence-only (15%), MV + TPN (10%), and MV + Paralytics + TPN (4%). The primary study aim was to characterize the impact of TPN-dependence and paralytics on one-year post-transplant survival (PTS). Results: Compared to no-support, supported infants were generally at higher risk and more ill at transplant, with greater rates of congenital heart disease, renal and hepatic dysfunctions, and inotrope requirements. Post-transplant hospital outcomes were inferior among supported patients; all support groups experienced longer post-transplant MV, intensive care unit, and hospital lengths of stay (all P < .05 vs no-support). Upon multivariable analysis, each support modality independently predicted 1-year mortality (MV vs no-MV: 1.54 [1.10-2.14]; MV + Paralytics vs neither: 2.02 [1.25-3.27]; TPN vs no-TPN: 1.53 [1.10-2.13]; P < .01 for all), whereas no-support was protective (HR 0.66 [95% CI 0.48-0.91]). Conclusions: Infants who require paralytics and/or who are TPN-dependent at the time of HTx experience worse one-year PTS. Such knowledge can assist in risk-stratification, and the identification of patients who would benefit from pretransplant optimization.

Complications and management of functional single ventricle patients with Fontan circulation: From surgeon's point of view

Fontan surgery by step-wise completing the isolation of originally mixed pulmonary and systemic circulation provides an operative approach for functional single-ventricle patients not amenable to biventricular repair and allows their survival into adulthood. In the absence of a subpulmonic pumping chamber, however, the unphysiological Fontan circulation consequently results in diminished cardiac output and elevated central venous pressure, in which multiple short-term or long-term complications may develop. Current understanding of the Fontan-associated complications, particularly toward etiology and pathophysiology, is extremely incomplete. What's more, ongoing efforts have been made to manage these complications to weaken the Fontan-associated adverse impact and improve the life quality, but strategies are ill-defined. Herein, this review summarizes recent studies on cardiac and non-cardiac complications associated with Fontan circulation, focusing on significance or severity, etiology, pathophysiology, prevalence, risk factors, surveillance, or diagnosis. From the perspective of surgeons, we also discuss the management of the Fontan circulation based on current evidence, including post-operative administration of antithrombotic agents, ablation, pacemaker implantation, mechanical circulatory support, and final orthotopic heart transplantation, etc., to standardize diagnosis and treatment in the future.

Failures of the Fontan System in Univentricular Hearts and Mortality Risk in Heart Transplantation: A Systematic Review and Meta-Analysis

The Fontan procedure (FP) is the standard surgical treatment for Univentricular heart diseases. Over time, the Fontan system fails, leading to pathologies such as protein-losing enteropathy (PLE), plastic bronchitis (PB), and heart failure (HF). FP should be considered as a transitional step to the final treatment: heart transplantation (HT). This systematic review and meta-analysis aims to establish the risk of death following HT according to the presence of FP complications. There was a total of 691 transplanted patients in the 18 articles, immediate survival 88% (n = 448), survival from 1 to 5 years of 78% (n = 427) and survival from 5.1 to 10 years of 69% (n = 208), >10 years 61% (n = 109). The relative risk (RR) was 1.12 for PLE (95% confidence interval [CI] = 0.89-1.40, p = 0.34), 1.03 for HF (0.7-1.51, p = 0.88), 0.70 for Arrhythmias (0.39-1.24, p = 0.22), 0.46 for PB (0.08-2.72, p = 0.39), and 5.81 for CKD (1.70-19.88, p = 0.005). In patients with two or more failures, the RR was 1.94 (0.99-3.81, p = 0.05). After FP, the risk of death after HT is associated with CKD and with the presence of two or more failures.

Systemic Venous Reconstructions During Pediatric Heart Transplantation

BACKGROUND

Congenital heart disease continues to be an important indication for pediatric heart transplantation (HT) and is often complicated by systemic venous anomalies. The need for reconstruction, surgical technique used, as well as the outcomes of these have limited documentation.

METHODS

Descriptive, retrospective study of patients transplanted at Emory University between 2006 and 2017. We reviewed surgical data, follow-up, and interventions for patients necessitating venous reconstruction during transplantation.

RESULTS

A total of 179 transplants were performed during the time period of which 74 (41%) required systemic venous reconstruction. Mean age at transplant was 6.3 (±6.16) years, and 74.3% of these patients carried a diagnosis of single ventricle; 51 (68.9%) of 74 patients required pulmonary artery reconstruction at the time of HT. Forty patients required superior vena caval reconstruction, while 22 patients required inferior vena caval reconstruction due to prior palliation or anomaly. Venous anomalies along with other anatomic features necessitated biatrial transplantation in four patients. Posttransplant evaluation revealed systemic venous stenosis in 14 (18.9%) of 74 patients. Eight (10.8%) patients required 12 interventions for the systemic veins. Patients with bilateral Glenn anastomosis prior to transplant were at high risk for the development of stenosis and needing interventions. Systemic venous complications were uncommon in those with native systemic veins without Glenn or Fontan procedure.

CONCLUSION

Systemic venous reconstruction needs are high in pediatric HT. Posttransplant stenosis and the need for interventions are relatively common. Current techniques for systemic venous reconstruction for complex congenital heart disease patients may deserve further review to optimize these outcomes.

The Improved Prognosis of Hypoplastic Left Heart: A Population-Based Register Study of 343 Cases in England and Wales

Background: Hypoplastic Left Heart Syndrome (HLHS) is a severe congenital heart defect (CHD) characterised by the underdevelopment of the left side of the heart with varying levels of hypoplasia of the left atrium, mitral valve, left ventricle, aortic valve and aortic arch. In the UK, age 12 survival for cases born between 1991 and 1993 was 21%. UK survival estimates corresponding to cases born between 2000 and 2015 were improved at 56%, but survival was examined up to age five only. Contemporary long-term survival estimates play a crucial role in counselling parents following diagnosis. The aim of this study was to report survival estimates up to age 15 for children born with HLHS or hypoplastic left ventricle with additional CHD in England and Wales between 1998 and 2012. Methods: Cases of HLHS notified to four congenital anomaly registers in England and Wales during 1998-2012, matched to Office for National Statistics mortality information, were included. Kaplan-Meier survival estimates to age 15 were reported. Cox regression models were fitted to examine risk factors for mortality. Results: There were 244 cases of HLHS and 99 cases of hypoplastic left ventricle co-occurring with other CHD, with traced survival status. Kaplan-Meier survival estimates for HLHS were 84.4% at age 1 week, 76.2% at 1 month, 63.5% at age 1 year, 58.6% at age 5 years, 54.6% at age 10 years, and 32.6% to age 15 years. The Kaplan-Meier survival estimates for cases of hypoplastic left ventricle co-occurring with additional CHD were 90.9% at age 1 week, 84.9% at 1 month, 73.7% at age 1 year, 67.7% to age 5 years, 59.2% to age 10 years, and 40.3% to age 15 years. Preterm birth (p = 0.007), low birth weight (p = 0.005), and female sex (p = 0.01) were associated with mortality. Conclusions: We have shown that prognosis associated with HLHS in the twenty first century exceeds that of many previous population-based studies, likely due to improvements in intensive care technologies and advances in surgical techniques over the last few decades.

Fate of patients with single ventricles who do not undergo the Fontan procedure

BACKGROUND

The Fontan procedure, the last of a series of palliative operations for patients born with single ventricles, is associated with a significant late burden of complications. There are other strategies for patients who are suboptimal candidates for Fontan completion, however the long-term outcomes of these different surgical options have not been clearly elucidated. We performed a systematic literature review to establish the current role of other treatment approaches besides the Fontan procedure.

METHODS

MEDLINE and Embase databases were systematically searched for articles describing the long-term outcomes of patients with single ventricles who have not received the Fontan procedure.

RESULTS

A total of 36 articles met all inclusion criteria. There is a scarcity of contemporary data on the non-Fontan cohort. Historical studies provided a significant contribution.

CONCLUSIONS

Long-term survival in unoperated patients with single ventricles is possible under the rare conditions of having balanced hemodynamics. Up to half of patients may survive on only a systemic-to-pulmonary artery shunt or bidirectional cavopulmonary shunt for over 20 years with reasonable functional status. In patients with a failing single ventricle, the bidirectional cavopulmonary shunt is an excellent bridge to heart transplantation and may provide better post-transplant survival than those with a Fontan circulation. Currently, the Fontan procedure continues to be the best definitive palliation for patients born with single ventricle lesions. However, for those with borderline indications, other strategies should be carefully considered.

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.

Hybrid stage 1 palliation as a bridge to cardiac transplantation in patients with high-risk single ventricle physiology

BACKGROUND

The hybrid stage 1 palliation for hypoplastic left heart syndrome (HLHS) was first described in 1993 as a bridge to heart transplant for HLHS. There are limited data on this strategy as primary heart transplantation for HLHS has become less common.

METHODS

This is an observational, single-center study comparing pre- and post-transplant outcomes of patients listed for transplant following hybrid palliation with those following surgical stage 1 palliation.

RESULTS

From 2004 to 2017, 21 patients underwent hybrid palliation as a bridge to heart transplant and 28 patients were listed for transplant following surgical stage 1 palliation or aortic arch repair and pulmonary artery band placement. Premature birth and the presence of genetic or anatomic abnormalities were more common in the hybrid group. Need for extracorporeal membrane oxygenation (ECMO) support and ventricular dysfunction was more common in the surgical group. There was a trend toward shorter waitlist times in the surgical cohort (36 days vs 70 days, P = 0.06). There was no difference in waitlist mortality (19% vs 21%, P = 0.61). Survival at 1 and 5 years post-transplant was similar for the hybrid and surgical cohorts (5-year survival, 80% vs 85%, P = 0.94, respectively). There was no difference in the number of post-transplant interventions.

CONCLUSIONS

Although the hybrid patients represented a higher risk cohort and demonstrated longer wait times, the waitlist and post-transplant mortality was equivalent between the two groups. For high-risk patients, the hybrid palliation as a bridge to transplant appears to be a reasonable strategy.

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 failure after the Norwood procedure: An analysis of the Single Ventricle Reconstruction Trial

BACKGROUND

Heart failure results in significant morbidity and mortality in young children with hypoplastic left heart syndrome (HLHS) after the Norwood procedure.

METHODS

We studied subjects enrolled in the prospective Single Ventricle Reconstruction (SVR) Trial who survived to hospital discharge after a Norwood operation and were followed up to age 6 years. The primary outcome was heart failure, defined as heart transplant listing after Norwood hospitalization, death attributable to heart failure, or symptomatic heart failure (New York Heart Association [NYHA] Class IV). Multivariate modeling was undertaken using Cox regression methodology to determine variables associated with heart failure.

RESULTS

Of the 461 subjects discharged home following a Norwood procedure, 66 (14.3%) met the criteria for heart failure. Among these, 15 died from heart failure, 39 were listed for transplant (22 had a transplant, 12 died after listing, and 5 were alive and not yet transplanted), and 12 had NYHA Class IV heart failure but were never listed. The median age at heart failure identification was 1.28 (interquartile range 0.30 to 4.69) years. Factors associated with early heart failure included post-Norwood lower fractional area change, need for extracorporeal membrane oxygenation, non-Hispanic ethnicity, Norwood perfusion type, and total support time (p < 0.05).

CONCLUSIONS

By 6 years of age, heart failure developed in nearly 15% of children after the Norwood procedure. Although transplant listing was common, many patients died from heart failure before receiving a transplant or without being listed. Shunt type did not impact the risk of developing heart failure.

Identifiable Risk Factors and Miscalculations During Listing for Pediatric Heart Transplantation

The objective of this study is to describe identifiable risk factors, complications, and pitfalls while listing pediatric patients for heart transplantation, which is the standard of care for end-stage heart disease in children. Since the introduction of cyclosporine in the 1980s, the management in pediatric heart transplantation has shown consistent improvement, mainly because of technological advances and the integration of multidisciplinary teams in the field. However, the complexity of this patient population makes medical providers vulnerable to complications as a result of undesirable mistakes. Transplant survival is impacted negatively when mistakes from health-care providers compound the high-risk status of the patient. The identification of multiple risk factors and undesirable miscalculations may help transplant teams make decisions before allocating organs, intervene or minimize morbidity, and provide the best quality of life to recipients.