Incidence and risk factors for mortality in infants awaiting heart transplantation in the USA

Impact of the Pediatric ABO Policy Change on Listings, Transplants, and Outcomes for Children Younger Than 2 Years Listed for Heart Transplantation in the United States

BACKGROUND

We assessed the impact of the liberalized ABO pediatric policy change on candidate characteristics and outcomes for children undergoing heart transplant (HT).

METHODS AND RESULTS

Children <2 years undergoing HT with ABO strategy reported at listing and HT from December 2011 to November 2020 to the Scientific Registry of Transplant Recipients database were included. Characteristics at listing, HT, and outcomes during the waitlist and post-transplant were compared before the policy change (December 16, 2011 to July 6, 2016), and after the policy change (July 7, 2016 to November 30, 2020). The percentage of ABO-incompatible (ABOi) listings did not increase immediately after the policy change (P = .93); however, ABOi transplants increased by 18% (P < .0001). At listing, both before and after the policy change, ABOi candidates had higher urgency status, renal dysfunction, lower albumin, and required more cardiac support (intravenous inotropes, mechanical ventilation) than those listed ABO compatible (ABOc). On multivariable analysis, there were no differences in waitlist mortality between children listed as ABOi and ABOc before the policy change (adjusted hazard ratio [aHR] 0.80, 95% confidence interval [CI] 0.61-1.05, P = .10) or after the policy change (aHR 1.2, 95% CI 0.85-1.6, P = .33). Post-transplant graft survival was worse for ABOi transplanted children before the policy change (aHR 1.8, 95% CI 1.1-2.8, P = .014), but not significantly different after the policy change (aHR 0.94, 95% CI 0.61-1.4, P = .76). After the policy change, ABOi listed children had significantly shorter waitlist times (P < .05).

CONCLUSIONS

The recent pediatric ABO policy change has significantly increased the percentage of ABOi transplantations and decreased waitlist times for children listed ABOi. This change in policy has resulted in broader applicability and actual performance of ABOi transplantation with equal access to ABOi or ABOc organs, and thus eliminated the potential disadvantage of only secondary allocation to ABOi recipients.

Applying the Hybrid Concept as a Bridge to Transplantation in Infants Without Hypoplastic Left Heart Syndrome

Therapies to support small infants in decompensated heart failure that are failing medical management are limited. We have used the hybrid approach, classically reserved for high-risk infants with single ventricle physiology, in patients with biventricular physiology with left ventricular failure. This approach secures systemic circulation, relieves left atrial hypertension, protects the pulmonary vasculature, and allows the right ventricle to support cardiac output. This approach can be used as a bridge to transplantation in select individuals. Infants without single ventricle congenital heart disease who were treated with the hybrid approach between 2008 and 2021 were included in analysis. Eight patients were identified. At the time of hybrid procedure, the median weight was 3.2 kg (range 2.4-3.6 kg) and the median age was 18 days (range 1-153 days). Seventy five percent were mechanically ventilated and 88% were on inotropic support. The median duration from hybrid procedure to transplant was 63 days (range 4-116 days). All patients experienced a good outcome (delisted for improvement or transplanted). The hybrid procedure is an appropriate therapeutic bridge to transplantation in a carefully selected subset of critically ill infants without single ventricle congenital heart disease in whom alternate therapies may confer increased risk for morbidity and mortality.

Weight Matching in Infant Heart Transplantation: A National Registry Analysis

BACKGROUND

Infants account for a significant proportion of pediatric heart transplantation but also suffer from a high waitlist mortality. Donor oversizing by weight-based criteria is common practice in transplantation and is prevalent in this group. We sought to analyze the impact of oversizing on outcomes in infants.

METHODS

Infant heart transplantations reported to the United Network for Organ Sharing from January 1994 to September 2019 were retrospectively analyzed. 2384 heart transplantation recipients were divided into quintiles (Q1-Q5) on the basis of donor-to-recipient weight ratio (DRWR). Multivariate Cox regression was used to estimate the effect of DRWR. The primary end point was graft survival at 1 year.

RESULTS

The median DRWR for each quintile was 0.90 (0.37-1.04), 1.17 (1.04-1.29), 1.43 (1.29-1.57), 1.74 (1.58-1.97), and 2.28 (1.97-5.00). Pairwise comparisons showed improved survival for Q3 and Q4 over each of the bottom 2 quintiles and the top quintile. Regression analyses found that Q3 and Q4 were protective against graft failure compared with the bottom 2 quintiles. There was no difference in hazard among the top 3 quintiles. Significant covariates included primary diagnosis, ischemia time, serum bilirubin level, transplantation year, mechanical ventilation at transplantation, and extracorporeal membrane oxygenation at transplantation. Sex, female-to-male transplantation, and mechanical circulatory support at transplantation were not significant in univariate analyses.

CONCLUSIONS

Modest oversizing by DRWR (1.29-1.97) is associated with increased survival and lower risk in infant heart transplantation. Additional investigation is needed to establish best practices for size matching in this population.

Increasing donor-recipient weight mismatch in infant heart transplantation is associated with shorter waitlist duration and no increased morbidity or mortality

OBJECTIVES

Infants awaiting paediatric heart transplantation (PHT) experience long waitlist duration and high mortality due to donor shortage. Using the United Network for Organ Sharing database, we explored if increasing donor-recipient weight ratio (DRWR) >2.0 (recommended cutoff) was associated with adverse outcomes.

METHODS

Between 2007 and 2020, 1392 infants received PHT. We divided cohort into 3 groups: A (DRWR ≤1.0, n = 239, 17%), B (DRWR 1.0-2.0, n = 947, 68%), C (DRWR >2.0, n = 206, 15%). Group characteristics and PHT outcomes were analysed.

RESULTS

DRWR ranged between 0.5 and 4.1. Underlying pathology (congenital versus cardiomyopathy), gender, race, renal function and mechanical circulatory support were comparable between groups. Group C patients were more likely to be ventilated, to receive ABO blood group (ABO)-incompatible heart and to have longer donor ischaemic time. Waitlist duration was significantly shorter for group C (33 vs 50 days, P < 0.1). Early outcomes for groups A, B and C were the following (respectively): operative death (6%, 4%, 3%, P = 0.29), primary graft dysfunction (5%, 3%, 3%, P = 0.30), renal failure (10%, 7%, 7%, P = 0.42) and stroke (3%, 4%, 1%, P = 0.36). The DRWR group was not associated with operative death in either congenital (odds ratio (OR) = 0.819, 95% confidence interval (CI) = 0.523-1.282) or cardiomyopathy (OR = 1.221, 95% CI = 0.780-1.912) patients and only significant factor was pre-PHT extracorporeal membrane oxygenation (OR = 4.400, 95% CI = 2.761-7.010). Additionally, survival at 1 year (87%, 87%, 85%, P = 0.80) and 5 years (76%, 78%, 77%, P = 0.80) was comparable between the DRWR groups.

CONCLUSIONS

Infants who received PHT with DRWR >2.0, up to 4.1, experienced shorter waitlist duration with no demonstrable increase in peri-transplant complications, operative or late mortality. Historic practice to avoid DRWR > 2.0 due to complications (e.g. hypertension-related stroke, graft dysfunction, death) is not currently supported in infants and stretching DRWR acceptance criteria would decrease PHT waitlist duration and potentially improve waitlist complications and mortality.

An in vitro comparison of intra-operative isohemagglutinin and human leukocyte antigen removal techniques in pediatric heart transplantation

BACKGROUND

Highly sensitized pediatric patients awaiting heart transplantation experience longer wait times and thus higher waitlist mortality. Similarly, children less than 2 years of age have increased waitlist times and mortality when compared to their older peers. To improve the likelihood of successful transplantation in these patients, various strategies have been utilized, including peri-operative plasmapheresis. However, limited data exists comparing plasmapheresis techniques for antibody reduction. This study's aim was to compare the in vitro magnitude of isohemagglutinin titers (IT) and human leukocyte antigen (HLA) antibody removal and the time required between membrane-based plasmapheresis (MP) and centrifuge-based plasmapheresis (CP) incorporated into the extracorporeal (EC) circuit.

METHODS

Two MP (Prismaflex) and two CP (Spectra Optia, Terumo BCT) circuits were incorporated into four separate EC circuits primed with high titer, highly sensitized type O donor whole blood. Assays were performed to determine baseline IT and anti-HLA antibodies and then at 30-minute increments until completion of the run (two plasma volume exchanges) at two hours.

RESULTS

There was a decrease in anti-A and anti-B IgM and IgG titers with both MP and CP. Mean anti-A and anti-B titer reduction was by 4.625 titers (93.7% change) and 4.375 titers (93.8% change) using MP and CP, respectively. At 2 h of apheresis, CP reduced 62.5% of all ITs to ≤ 1:4, while MP reduced 50% of ITs to ≤ 1:4. Additionally, reduction of anti-HLA class II antibody to mean fluorescence intensity (MFI) <3000 was achieved with both MP and CP. At 2 h of apheresis, CP reduced MFI by 2-3.5 fold and MP reduced MFI by 1.7-2.5 fold. Both demonstrated similar hemolytic and thrombotic profiles.

CONCLUSIONS

In this in vitro plasmapheresis model of IT and anti-HLA antibody reduction, both MP and CP incorporated into the EC circuit can be used quickly and effectively to reduce circulating antibodies. While CP may have some greater efficiency, further study is necessary to verify this in vivo.

Pediatric risk to orthotopic heart transplant (PRO) score: Insights from United Network for Organ Sharing (UNOS) waitlist mortality findings

BACKGROUND

Pediatric heart transplant candidates on the waitlist have the highest mortality rate among all solid organ transplants. A risk score incorporating a candidate's individual risk factors may better predict mortality on the waitlist and optimize organ allocation to the sickest of those awaiting transplant.

METHODS

Using the United Network for Organ Sharing (UNOS) database, we evaluated a total of 5542 patients aged 0-18 years old on the waitlist for a single, first time, heart transplant from January 2010 to June 2019. We performed a univariate analysis on two-thirds (N = 3705) of these patients to derive the factors most associated with waitlist mortality or delisting secondary to deterioration within 1 year. Those with a p <0.2 underwent a multivariate analysis and the resulting factors were used to build a prediction model using the Fine-Grey model analysis. This predictive scoring model was then validated on the remaining one-third of the patients (N = 1852).

RESULTS

The Pediatric Risk to OHT (PRO) scoring model utilizes the following unique patient variables: blood type, diagnosis of congenital heart disease, weight, presence of ventilator support, presence of inotropic support, extracorporeal membrane oxygenation (ecmo) status, creatinine level, and region. A higher score indicates an increased risk of mortality. The PRO score had a predictive strength of 0.762 as measured by area under the ROC curve at 1 year.

CONCLUSION

The PRO score is an improved predictive model with the potential to better assess mortality for patients awaiting heart transplant.

Cardioprotective Actions of a Glucagon-like Peptide-1 Receptor Agonist on Hearts Donated After Circulatory Death

Background Heart transplantation with a donation after circulatory death (DCD) heart is complicated by substantial organ ischemia and ischemia-reperfusion injury. Exenatide, a glucagon-like peptide-1 receptor agonist, manifests protection against cardiac ischemia-reperfusion injury in other settings. Here we evaluate the effects of exenatide on DCD hearts in juvenile pigs. Methods and Results DCD hearts with 15-minutes of global warm ischemia after circulatory arrest were reperfused ex vivo and switched to working mode. Treatment with concentration 5-nmol exenatide was given during reperfusion. DCD hearts treated with exenatide showed higher myocardial oxygen consumption (exenatide [n=7] versus controls [n=7], over 60-120 minutes of reperfusion, P<0.001) and lower cardiac troponin-I release (27.94±11.17 versus 42.25±11.80 mmol/L, P=0.04) during reperfusion compared with controls. In working mode, exenatide-treated hearts showed better diastolic function (dp/dt min: -3644±620 versus -2193±610 mm Hg/s, P<0.001; Tau: 15.62±1.78 versus 24.59±7.35 milliseconds, P=0.02; lateral e' velocity: 11.27 ± 1.46 versus 7.19±2.96, P=0.01), as well as lower venous lactate levels (3.17±0.75 versus 5.17±1.44 mmol/L, P=0.01) compared with controls. Higher levels of activated endothelial nitric oxide synthase (phosphorylated to total endothelial nitric oxide synthase levels: 2.71±1.16 versus 1.37±0.35, P=0.02) with less histological evidence of endothelial damage (von Willebrand factor expression: 0.024±0.007 versus 0.331±0.302, pixel/μm, P=0.04) was also observed with exenatide treatment versus controls. Conclusions Acute treatment of DCD hearts with exenatide limits myocardial and endothelial injury and improves donor cardiac function.

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.

Not all durations of preheart transplant mechanical ventilation portend inferior post-transplant survival in children

BACKGROUND

Mechanical ventilation prior to pediatric heart transplantation predicts inferior post-transplant survival, but the impact of ventilation duration on survival is unclear.

METHODS

Data from the United Network for Organ Sharing and Pediatric Health Information System were used to identify pediatric (<18 years) heart transplant recipients from 2003 to 2020. Patients ventilated pretransplant were first compared to no ventilation, then ventilation durations were compared across quartiles of ventilation (≤1 week, 8 days-5 weeks, >5 weeks).

RESULTS

At transplant, 11% (511/4506) of patients required ventilation. Ventilated patients were younger, had more congenital heart disease, more urgent listing-status, and greater rates of nephropathy, TPN-dependence, and inotrope and ECMO requirements (p < .001 for all). Post-transplant, previously ventilated patients experienced longer ventilation durations, ICU and hospital stays, and inferior survival (all p < .001). Hospital outcomes and survival worsened with longer pretransplant ventilation. One-year and overall survival were similar between the no-ventilation and ≤1 week groups (p = .703 & p = .433, respectively) but were significantly worse for ventilation durations >1 week (p < .001). On multivariable analysis, ventilation ≤1 week did not predict mortality (HR 0.98 [95% CI 0.85-1.43]), whereas ventilation >1 week did (HR: 1.18 [1.01-1.39]).

CONCLUSIONS

Longer pretransplant ventilation portends worse outcomes, although only ventilation >1 week predicts mortality. These findings can inform pretransplant prognostication.

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.

Waitlist and posttransplant outcomes of critically ill infants awaiting heart transplantation managed without ventricular assist device support

BACKGROUND

Infants listed for heart transplant are at high risk for waitlist mortality. While waitlist mortality for children has decreased in the current era of increased ventricular assist device use, outcomes for small infants supported by ventricular assist device remain suboptimal. We evaluated morbidity and survival in critically ill infants listed for heart transplant and managed without ventricular assist device support.

METHODS

Critically ill infants (requiring ≥1 inotrope and mechanical ventilation or ≥2 inotropes without mechanical ventilation) listed between 2008 and 2019 were included. During the study period, infants were managed primarily medically. Mechanical circulatory support, specifically extracorporeal membrane oxygenation, was utilized as "rescue therapy" for decompensating patients.

RESULTS

Thirty-two infants were listed 1A, 66% with congenital heart disease. Median age and weight at listing were 2.2 months and 4.4 kg, with 69% weighing <5 kg. At listing, 97% were mechanically ventilated, 41% on ≥2 inotropes, and 25% under neuromuscular blockade. Five patients were supported by ECMO after listing. A favorable outcome (transplant or recovery) was observed in 84%. One-year posttransplant survival was 92%. Infection was the most common waitlist complication occurring in 75%. Stroke was rare, occurring in one patient who was supported on ECMO. Renal function improved from listing to transplant, death, or recovery (eGFR 70 vs 87 ml/min/1.73m² , p = .001).

CONCLUSION

A strategy incorporating a high threshold for mechanical circulatory support and acceptance of prolonged mechanical ventilation and neuromuscular blockade can achieve good survival and morbidity outcomes for critically ill infants listed for heart transplant.

Pediatric heart transplantation: The past, the present, and the future

Heart transplantation (HTx) has a storied past, with origins dating back to the early twentieth century and the first pediatric orthotopic heart transplant performed in 1967 on a neonate with Ebstein abnormality. Today, approximately 500 pediatric HTx are performed annually, with survival times now measured in decades rather than days or weeks. In large part, advances in immunosuppression, critical care, dedicated transplant teams and mechanical circulatory support have paved the way for improvements in waitlist mortality and post-transplant survival, with future directions including the development of intracorporeal ventricular assist devices (VADs) for small children, expanding/standardizing donor criteria, and xenotransplantation.

The Waiting List Mortality of Pediatric Heart Transplantation Candidates in Korea before the Pediatric Ventricular Assist Device Era

BACKGROUND

Despite advancements in heart transplantation for pediatric patients in Korea, the waiting list mortality has not been reported. Therefore, we investigated the waiting list mortality rate and factors associated with patient mortality.

METHODS

We reviewed the medical records of pediatric patients who were registered for heart transplantation at three major hospitals in Korea from January 2000 to January 2020. All patients who died while waiting for heart transplantation were investigated, and we identified the waiting list mortality rate, causes of mortality and median survival periods depending on the variable risk factors.

RESULTS

A total of 145 patients received heart transplantations at the three institutions we surveyed, and the waiting list mortality rate was 26%. The most common underlying diseases were cardiomyopathy (66.7%) and congenital heart disease (30.3%). The leading causes that contributed to death were heart failure (36.3%), multi-organ failure (27.2%), and complications associated with extracorporeal membrane oxygenation (ECMO) (25.7%). The median survival period was 63 days. ECMO was applied in 30 patients. The different waiting list mortality percentages according to age, cardiac diagnosis, use of ECMO, and initial Korean Network of Organ Sharing (KONOS) level were determined using univariate analysis, but age was the only significant factor associated with waiting list mortality based on a multivariate analysis.

CONCLUSION

The waiting list mortality of pediatric heart transplantation candidates was confirmed to be considerably high, and age, underlying disease, the application of ECMO, and the initial KONOS level were the factors that influenced the survival period.

Ethical and practical dilemmas in cardiac transplantation in infants: a literature review

The waiting time in infants for a cardiac transplant remains high, due to the scarcity of donors. Consequently, waiting list morbidity and mortality are higher than those in other age groups. Therefore, the decision to list a small infant for cardiac transplantation is seen as an ethical dilemma by most physicians. This review aims to describe outcomes, limitations, and ethical considerations in infant heart transplantation. We used Medline and Embase as data sources. We searched for publications on infant (< 1 year) heart transplantation, bridge-to-transplant and long-term outcomes, and waiting list characteristics from January 2009 to March 2021. Outcome after cardiac transplant in infants is better than that in older children (1-year survival 88%), and complications are less frequent (25% CAV, 10% PTLD). The bridge-to-transplant period in infants is associated with increased mortality (32%) and decreased transplantation rate (43%). This is mainly due to MCS complications or the limited MCS options (with 51% mortality in infancy). Outcomes are worse for infants with CHD or in need of ECMO-support.Conclusion: Infants listed for cardiac transplantation have a high morbidity and mortality, especially in the period between diagnosis and transplantation. For those who receive cardiac transplant, the outlook is encouraging. Unfortunately, despite growing experience in VAD, mortality in children < 10 kg and children with CHD remains high. After transplantation, patients carry a psychological burden and there is a probability of re-transplantation later in life, with decreased outcomes compared to primary transplantation. These considerations are seen as an important ethical dilemma in many centers, when considering cardiac transplantation in infants (< 1 year). What is Known: • For infants, waitlist mortality remains high. In the pediatric population, MCS reduces the waiting list mortality. What is New: • Outcomes after infant cardiac transplantation are better than other age groups; however, MCS options remain limited, with persistently high waiting list mortality. • Future developments in MCS and alternative options to reduce waiting list mortality such as ABO-incompatible transplantation and pulmonary artery banding are encouraging and will improve ethical decision-making when an infant is in need of a cardiac transplant.

Hospital outcomes for pediatric heart transplant recipients undergoing tracheostomy: A multi-institutional analysis

Tracheostomy is associated with increased mortality and resource utilization in children with CHD. However, the prevalence and hospital outcomes of tracheostomy in children with HTx are not known. We describe the prevalence and compare the post-HTx hospital outcomes of pediatric patients with Pre-TT and Post-TT to those without tracheostomy. A multi-institutional retrospective cohort study was performed using the Pediatric Health Information System database. Hospital mortality, mediastinitis, LOS, and costs were compared among patients with Pre-TT, Post-TT, and no tracheostomy. Pre-TT was identified in 29 (1.1%) and Post-TT was identified in 41 (1.6%) of 2603 index HTx hospitalizations. Patients with Pre-TT were younger and more likely to have CHD, a non-cardiac birth defect, or an airway anomaly compared to those without Pre-TT. Pre-TT was not independently associated with increased post-HTx in-hospital mortality. Age at HTx < 1 year, CHD, and Post-TT were associated with increased in-hospital mortality. Pre-TT that occurred during the HTx hospitalization and Post-TT were associated with increased resource utilization. Tracheostomy was not associated with mediastinitis.

Interplay between donor and recipient factors impacts outcomes after pediatric heart transplantation: An analysis from the united network for organ sharing database

BACKGROUND

Donor utilization rates continue to be low for pHT, however, efforts to expand the donor acceptance criteria have shown mixed results in single-institution studies in pediatric and adult transplantation. Purpose of this study is to assess impact of individual and cumulative donor risk factors on transplant outcomes as well as the interplay between donor and recipient risk factors as it relates to transplant outcomes.

METHOD

We analyzed pHT UNOS data (2008-2018) to compare the recipient characteristics, donor characteristics, and outcomes based on donor ejection fraction of less than 50% (low EF) and or ischemic time of greater than 4 hours (prolonged IT).

RESULTS

A total of 4345 pHT were performed of which 1309 (30.1%) were with prolonged IT and 122 (2.8%) in low EF. Additionally, 58 (1.3%) were performed with both low EF and prolonged IT (combined risk). Rest (2856 patients, 65.7%) was considered low risk. Recipients of combined risk were more likely to be younger, have post-surgical congenital heart disease, be on ECMO or ventilator but less likely on VAD (all P < .01) compared with any other group. Waitlist time was significantly lower for low EF (mean 39 days, 15-109) or combined risk group (36 days, range 15-80) compared with other groups (60 days, range 23-125) (P = .01). 1-year mortality was 8% in low-risk group, 12% in prolonged IT, 14% in reduced EF, and 28% in combined risk patients (P < .01). Number of treated rejections in one year were significantly higher in prolonged IT and combined risk group compared to other groups (P < .01). When stratified by recipient risk, there was no difference in outcomes for low risk, prolonged IT, or low EF groups; however, there were significant survival differences for high-risk recipient versus low-risk recipient in each donor group.

CONCLUSION

Lower EF donors performed similar to prolonged IT donor, but were uncommonly used. Acceptance of risk was common in recipients deemed higher risk for waitlist mortality and led to shorter wait times. Caution should be used in accepting combined risk transplants. The recipient risk factors have significant impact on outcomes across all donor risk groups and further analysis will help balance the waitlist mortality with post-transplant outcomes.

The use of mechanical assist devices in the pediatric population

The last two decades have witnessed an expansion in the devices, support strategies, and outcomes for pediatric patients who require mechanical circulatory support. The use of large registries that house data on these devices and the development of shared learning networks have provided clinicians with the ability to critically assess outcomes for emerging and existing technology. The purpose of this review is to provide the reader with perspective on the most contemporary devices utilized for pediatric mechanical circulatory support. It will examine existing support strategies and the most contemporary outcomes regarding these devices including those in high risk patients.

Pediatric cardiac waitlist mortality-Still too high

Cardiac transplantation for children with end-stage cardiac disease with no other medical or surgical options is now standard. The number of children in need of cardiac transplant continues to exceed the number of donors considered "acceptable." Therefore, there is an urgent need to understand which recipients are in greatest need of transplant before becoming "too ill" and which "marginal" donors are acceptable in order to reduce waitlist mortality. This article reviewed primarily pediatric studies reported over the last 15 years on waitlist mortality around the world for the various subgroups of children awaiting heart transplant and discusses strategies to try to reduce the cardiac waitlist mortality.

Pediatric Ventricular Assist Device Support in the Netherlands

Background:

This study aimed to evaluate the changes in heart transplantation (HTx) waiting list mortality following the introduction of the Berlin Heart EXCOR (BH EXCOR) in the Netherlands, as well as the occurrence of adverse events in these children.

Methods:

A retrospective, single-center study was conducted including all pediatric patients (≤18 years) awaiting HTx. Patients were grouped in two eras based on availability of the BH EXCOR in our center, era I (1998-2006; not available) and era II (2007 to July 31, 2018; available).

Results:

In total, 87 patients were included, 15 in era I and 72 in era II. Extracorporeal membrane oxygenator support was required in 1 (7%) patient in era I and in 13 (18%) patients in era II. Overall mortality (7/15 in era I vs 16/72 in era II; 47% vs 22%, P = .06) and transplantation rates (8/15 in era I vs 47/72 in era II; 53% vs 65%, P = .39) did not differ significantly. Eleven (39%) patients of the pediatric ventricular assist device (VAD) population died, with the predominant cause being cerebrovascular accidents (CVAs) in eight (29%) patients. Furthermore, 14 (50%) of the pediatric VAD patients survived to transplantation. Adverse events most frequently occurring in VAD patients included CVA in 14 (50%), mostly (68%) within 30 days after VAD implantation, and bleeding requiring rethoracotomy in 14 (50%), all within 30 days after VAD implantation.

Conclusions:

The introduction of the BH EXCOR has positively impacted the survival of pediatric patients with end-stage heart failure in our center. The predominant cause of death changed from end-stage heart failure in era I to CVA in era II. We emphasize the need for large prospective registry–based studies.

The First Pediatric Heart Transplantation Bridged by a Durable Left Ventricular Assist Device in Korea

Treatment options for children with end-stage heart failure are limited. We report the first case of a successful pediatric heart transplantation bridged with a durable left ventricular assist device in Korea. A 10-month-old female infant with dilated cardiomyopathy and left ventricular non-compaction was listed for heart transplantation. During the waiting period, the patient’s status deteriorated. Therefore, we decided to provide support with a durable left ventricular assist device as a bridge to transplantation. The patient was successfully bridged to heart transplantation with effective support and without any major adverse events.

Expanding the donor pool for congenital heart disease transplant candidates by implementing 3D imaging-derived total cardiac volumes

BACKGROUND

Heart transplant waitlist mortality remains high in infants <1 year of age and among those with CHD. Currently, the median accepted donor-to-recipient weight percentage is approximately 130% of the recipient's weight. We hypothesized that patients with CHD may accept a larger organ using novel 3D-derived imaging data to estimate donor and recipient TCV.

METHODS

A single-center, retrospective study was performed using CT data for 13 patients with CHD and 94 control patients. 3D visualization software was used to create digital 3D heart models that provide an estimate of TCV. In addition, echocardiograms obtained prior to cross-sectional imaging were reviewed for presence of ventricular chamber dilation.

RESULTS

Sixty-two percent (8/13) of patients with CHD had 3D-derived TCV resulting in a weight that was >130% larger than their actual weight. This was seen in single-ventricle patients following Blalock-Taussig shunt and Fontan palliation, and patients with biventricular repair. Of those, 75% (6/8) had reported moderate-to-severe ventricular chamber dilation by echocardiogram or cardiac magnetic resonance imaging.

CONCLUSIONS

In a large portion of patients with CHD, 3D-derived TCV place the recipient at a higher listing weight than their actual weight. We propose obtaining cross-sectional imaging to better assess TCV in a recipient, which may increase the donor range for CHD recipients and improve organ utilization in pediatrics.

ISHLT consensus statement on donor organ acceptability and management in pediatric heart transplantation

The number of potential pediatric heart transplant recipients continues to exceed the number of donors, and consequently the waitlist mortality remains significant. Despite this, around 40% of all donated organs are not used and are discarded. This document (62 authors from 53 institutions in 17 countries) evaluates factors responsible for discarding donor hearts and makes recommendations regarding donor heart acceptance. The aim of this statement is to ensure that no usable donor heart is discarded, waitlist mortality is reduced, and post-transplant survival is not adversely impacted.

Paediatric heart transplantation: an update

Heart transplantation is a standard treatment for selected paediatric patients with end-stage heart disease. With improvement in surgical techniques, organ procurement and preservation strategies, immunosuppressive drugs, and more sophisticated monitoring strategies, survival following transplantation has increased over time. However, rejection, infection, renal failure, post-transplant lymphoproliferative disease and post-transplant cardiac allograft vasculopathy still preclude long-term survival. Therefore, continued multidisciplinary scientific efforts are needed for future gains. This review focuses on the current status, outcomes and ongoing challenges including patient selection, indications and contraindications, national and international survivals, post-transplant complications and quality of life.

Pediatric heart transplantation in the current era

PURPOSE OF REVIEW

To provide an international perspective and current review of pediatric heart transplantation (PHTx).

RECENT FINDINGS

Waitlist survival and long-term outcomes in PHTx continue to improve. Strategies to maximize donor pool utilization include ABO incompatible listing for infants and expanded donor-to-recipient weight ranges. However, there is a high degree of practice variation internationally, from listing strategies and donor acceptance practices to chronic immunosuppression regimens, long-term graft surveillance, and consideration for retransplantation.

SUMMARY

Common indications for PHTx include end-stage congenital heart disease and cardiomyopathy. Current median graft survival among PHTx recipients ranges from 13 to 22 years. Common morbidities include infection, rejection, renal dysfunction, coronary allograft vasculopathy, and posttransplant lymphoproliferative disease. International registry data, collaborative initiatives to standardize management, and multicenter studies continue to improve knowledge and advancement of the field.

Berlin Heart EXCOR® pediatric ventricular assist device in a patient with Sotos syndrome: a case report

Introduction

Berlin Heart EXCOR® pediatric ventricular assist device is a mechanical circulatory support device currently used in pediatric patients. Sotos syndrome is a well-described multiple anomaly syndrome characterized by overgrowth, distinctive craniofacial appearance, cardiac abnormalities, and variable learning disabilities.

Case presentation

We describe a 7-year-old female Caucasian child with classic Sotos syndrome features subjected to implantation of Berlin Heart EXCOR® pediatric biventricular assist device mechanical support. A heart transplant was carried out after a support time of 459 days. After 5 years of follow-up, our patient is clinically stable and the performance of the transplanted heart is excellent.

Conclusion

This case confirms that Berlin Heart EXCOR® pediatric ventricular assist device can provide satisfactory and safe circulatory support for children with end-stage heart diseases, even in those with Sotos syndrome. The syndrome is not a contraindication to implantation, since the complications are the same as those observed in patients without the syndrome and the prognosis is not affected by the disease.

iPhone in the Management of the Berlin Heart EXCOR Ventricular Assist Device

Berlin Heart Inc. EXCOR is an extracorporeal pneumatically pulsatile ventricular assist device approved for use in pediatric age group since 2011 in the United States. It is a well-established life-saving therapy for the bridge to heart transplant or to provide circulatory support in a transplanted patient. The most commonly reported problem was "membrane defect" in a postmarketing major device reporting. In general, the filling and emptying of the pump can be easily visualized, but the interobserver variability exist. In this first novel report, we used the iPhone slow motion video to quantify and compare the differences in filling and emptying that positively impacted the management of the Berlin Heart. This is an initial exploratory concept that will need further studies to validate this bedside tool.

Pediatric marginal donor hearts: Trends in US national use, 2005-2014

Pediatric patients awaiting heart transplant face high mortality rates due to donor organ shortages, including non-use of marginal donor hearts. We examined national trends in pediatric marginal donor heart use over time. UNOS data were queried for heart donors <18 years from 2005 to 2014. The proportion of donor hearts considered marginal was determined using previously cited marginal characteristics: left ventricular ejection fraction (LVEF) <50%, use of ≥2 inotropes, cerebrovascular death, CDC high-risk status, and eGFR < 30 mL/min/1.73 m² . Disposition of donor hearts was determined and stratified by marginal donor status. Of 6778 pediatric hearts offered from 2005 to 2014, 2373 (35.0%) were considered marginal. Non-use of marginal donor hearts was significantly higher than that of donor hearts without any marginal characteristics (59.5% vs 20.3%, P < .001). In particular, LVEF < 50% and donor inotropes were associated with high rates of organ non-use among pediatric donors. Yet, non-use of marginal donor organs decreased from 67% to 48% from 2005 to 2014 (P < .001). Although the proportion of pediatric donor hearts used for pediatric patients has increased, more than half of donor hearts are declined for use in pediatric recipients due, in part, to perceived marginal status.

Prelisting predictions of early postoperative survival in infant heart transplantation using classification and regression tree analysis

Infants listed for heart transplantation experience high waitlist and early post-transplant mortality, and thus, optimal allocation of scarce donor organs is required. Unfortunately, the creation and validation of multivariable regression models to identify risk factors and generate individual-level predictions are challenging. We sought to explore the use of data mining methods to generate a prediction model. CART analysis was used to create a model which, at the time of listing, would predict which infants listed for heart transplantation would survive at least 3 months post-transplantation. A total of 48 infants were included; 13 died while waiting, and six died within 3 months of heart transplant. CART analysis identified RRT, blood urea nitrogen, and hematocrit as terminal nodes with alanine transaminase as an intermediate node predicting death. No patients listed on RRT (n = 10) survived and only three of 12 (25%) patients listed on ECLS survived >3 months post-transplant. CART analysis overall accuracy was 83%, with sensitivity of 95% and specificity 76%. This study shows that CART analysis can be used to generate accurate prediction models in small patient populations. Model validation will be necessary before incorporation into decision-making algorithms used to determine transplant candidacy.

Neonatal heart transplantation

Neonatal heart transplantation was developed and established in the 1980's as a durable modality of therapy for complex-uncorrectable heart disease. Patients transplanted in the neonatal period have experienced unparalleled long-term survival, better than for any other form of solid-organ transplantation. However, the limited availability of neonatal and young infant donors has restricted the indications and applicability of heart transplantation among newborns in the current era. Indications for heart transplantation include congenital heart disease not amenable to other forms of surgical palliation, and cardiomyopathy, including some primary tumors. Use of ABO-incompatible transplants, and organs with prolonged cold ischemic time or marginal function have all been associated with good outcomes in infants. These extended strategies to increase the donor pool may also someday include donation after determination of circulatory death and the use of anencephalic donors. The operative techniques for donors and recipients of neonatal heart transplantation are unique and have been well-described. Immunosuppression protocols for neonates need not include induction and are largely steroid-free. Newborn and young infant transplant recipients have fewer episodes of rejection, less coronary allograft vasculopathy, less post-transplant lymphoproliferative disease and less renal dysfunction than their older counterparts. Long-term outcomes have been very encouraging in terms of graft survival, patient survival, and quality of life. Our review highlights the history, current indications, techniques and outcomes of heart transplantation in this immunologically-privileged subset of patients.

Toward the Virtual Benchmarking of Pneumatic Ventricular Assist Devices: Application of a Novel Fluid-Structure Interaction-Based Strategy to the Penn State 12 cc Device

The pediatric use of pneumatic ventricular assist devices (VADs) as a bridge to heart transplant still suffers for short-term major complications such as bleeding and thromboembolism. Although numerical techniques are increasingly exploited to support the process of device optimization, an effective virtual benchmark is still lacking. Focusing on the 12 cc Penn State pneumatic VAD, we developed a novel fluid-structure interaction (FSI) model able to capture the device functioning, reproducing the mechanical interplay between the diaphragm, the blood chamber, and the pneumatic actuation. The FSI model included the diaphragm mechanical response from uniaxial tensile tests, realistic VAD pressure operative conditions from a dedicated mock loop system, and the behavior of VAD valves. Our FSI-based benchmark effectively captured the complexity of the diaphragm dynamics. During diastole, the initial slow diaphragm retraction in the air chamber was followed by a more rapid phase; asymmetries were noticed in the diaphragm configuration during its systolic inflation in the blood chamber. The FSI model also captured the major features of the device fluid dynamics. In particular, during diastole, a rotational wall washing pattern is promoted by the penetrating inlet jet with a low-velocity region located in the center of the device. Our numerical analysis of the 12 cc Penn State VAD points out the potential of the proposed FSI approach well resembling previous experimental evidences; if further tested and validated, it could be exploited as a virtual benchmark to deepen VAD-related complications and to support the ongoing optimization of pediatric devices.

Asynchronous Pumping of a Pulsatile Ventricular Assist Device in a Pediatric Anastomosis Model

BACKGROUND

Both pulsatile and continuous flow ventricular assist devices are being developed for pediatric congenital heart defect patients. Pulsatile devices are often operated asynchronously with the heart in either an "automatic" or a fixed beat rate mode. However, most studies have only investigated synchronized ejection.

METHODS

A previously validated viscoelastic blood solver is used to investigate the parameters of pulsatility, power loss, and graft failure in a pediatric aortic anastomosis model.

RESULTS

Pulsatility was highest with synchronized flow and lowest at a 90° phase shift. Power loss decreased at 90° and 180° phase shifts but increased at a 270° phase shift. Similar regions of potential intimal hyperplasia and graft failure were seen in all cases but with phase-shifted ejection leading to higher wall shear stress on the anastomotic floor and oscillatory shear index on the anastomotic toe.

CONCLUSION

The ranges of pulsatility and hemodynamics that can result clinically using asynchronous pulsatile devices were investigated in a pediatric anastomosis model. These results, along with the different postoperative benefits of pump modulation, can be used to design an optimal weaning protocol.

Improved Survival While Waiting and Risk Factors for Death in Pediatric Patients Listed for Cardiac Transplantation

Our aim is to determine (a) the effect of changes in pre-transplant management and era of listing on survival of children listed for HTx and (b) risk factors for death while waiting. This retrospective study included all children listed between 1/1993 and 12/2009 at our center. Survival was determined using survival analysis and competing outcomes modeling. There were 254 listed patients of whom 144 (57%) had congenital heart disease, 208 (82%) were status 1, 52 used ECMO (20%), and 28 used ventricular assist device support (VAD) (11%) beginning in 2005. Overall mortality while waiting was 17% at 6 months, and 69% underwent transplant. Seven of 95 patients (7%) died waiting after 2004 compared to 36 of 159 (23%) before. ECMO and earlier year of listing were significant risk factors (p < 0.001) for wait-list mortality, whereas mortality was significantly lower (p = 0.002) after availability of VADs. Race, gender, blood type, and congenital diagnosis were not significant risk factors for death. Survival in pediatric patients listed for HTx has improved significantly in the current era at our institution. The availability of pediatric VADs has had a significant impact on survival while waiting in children listed for transplantation.

Acute kidney injury after heart transplant in young children: risk factors and outcomes

BACKGROUND

Critical illness following heart transplantation can include acute kidney injury (AKI). Study objectives were to define the epidemiology of, risk factors for, or impact on outcomes of AKI after pediatric heart transplant.

METHODS

Using data from a prospective study of 66 young children, we evaluated: (1) post-operative AKI rate (by pediatric modified RIFLE criteria); (2) pre, intra, and early post-operative AKI risk factors using stepwise logistic regression (3) effect of AKI on short-term outcomes (ventilation and length of pediatric intensive care unit (PICU) stay) using stepwise multiple regression.

RESULTS

AKI occurred in 73 % of children. Pre-transplant ventilation and higher baseline estimated creatinine clearance (eCCl) were independent risk factors for AKI. Pre-operative inotrope use was associated with reduced risk of AKI. Tacrolimus level emerged as important in multivariable risk prediction. Children with AKI had a longer duration of ventilation and length of pediatric intensive care unit (PICU) stay, with AKI being an independent predictor.

CONCLUSIONS

AKI was common after heart transplant and associated with more complicated early post-transplant course. Lower baseline eCCl was associated with lower incidence of AKI; this merits further investigation. The association of pre-operative inotropes with less AKI may reflect a pathophysiological mechanism or be a surrogate for clinical factors and management prior to transplant. Avoiding high tacrolimus levels may be a modifiable risk factor for AKI.

Hemodynamics in a Pediatric Ascending Aorta Using a Viscoelastic Pediatric Blood Model

Congenital heart disease is the leading cause of infant death in the United States with over 36,000 newborns affected each year. Despite this growing problem there are few mechanical circulatory support devices designed specifically for pediatric and neonate patients. Previous research has been done investigating pediatric ventricular assist devices (PVADs) assuming blood to be a Newtonian fluid in computational fluid dynamics (CFD) simulations, ignoring its viscoelastic and shear-thinning properties. In contrast to adult VADs, PVADs may be more susceptible to hemolysis and thrombosis due to altered flow into the aorta, and therefore, a more accurate blood model should be used. A CFD solver that incorporates a modified Oldroyd-B model designed specifically for pediatric blood is used to investigate important hemodynamic parameters in a pediatric aortic model under pulsatile flow conditions. These results are compared to Newtonian blood simulations at three physiological pediatric hematocrits. Minor differences are seen in both velocity and wall shear stress (WSS) during early stages of the cardiac cycle between the Newtonian and viscoelastic models. During diastole, significant differences are seen in the velocities in the descending aorta (up to 12%) and in the aortic branches (up to 30%) between the two models. Additionally, peak WSS differences are seen between the models throughout the cardiac cycle. At the onset of diastole, peak WSS differences of 43% are seen between the Newtonian and viscoelastic model and between the 20 and 60% hematocrit viscoelastic models at peak systole of 41%.

Continuous and Pulsatile Pediatric Ventricular Assist Device Hemodynamics with a Viscoelastic Blood Model

To investigate the effects of pulsatile and continuous pediatric ventricular assist (PVAD) flow and pediatric blood viscoelasticity on hemodynamics in a pediatric aortic graft model. Hemodynamic parameters of pulsatility, along with velocity and wall shear stress (WSS), are analyzed and compared between Newtonian and viscoelastic blood models at a range of physiological pediatric hematocrits using computational fluid dynamics. Both pulsatile and continuous PVAD flow lead to a decrease in pulsatility (surplus hemodynamic energy, ergs/cm(3)) compared to healthy aortic flow but with continuous PVAD pulsatility up to 2.4 times lower than pulsatile PVAD pulsatility at each aortic outlet. Significant differences are also seen between the two flow modes in velocity and WSS. The higher velocity jet during systole with pulsatile flow leads to higher WSSs at the anastomotic toe and at the aortic branch bifurcations. The lower velocity but continuous flow jet leads to a much different flow field and higher WSSs into diastole. Under a range of physiological pediatric hematocrit (20-60%), both velocity and WSS can vary significantly with the higher hematocrit blood model generally leading to higher peak WSSs but also lower WSSs in regions of flow separation. The large decrease in pulsatility seen from continuous PVAD flow could lead to complications in pediatric vascular development while the high WSSs during peak systole from pulsatile PVAD flow could lead to blood damage. Both flow modes lead to similar regions prone to intimal hyperplasia resulting from low time-averaged WSS and high oscillatory shear index.

Modern Outcomes of Mechanical Circulatory Support as a Bridge to Pediatric Heart Transplantation

BACKGROUND

Pediatric patients awaiting orthotopic heart transplantation frequently require bridge to transplantation (BTT) with mechanical circulatory support. Posttransplant survival outcomes and predictors of mortality have not been thoroughly described in the modern era using a large-scale analysis.

METHODS

The United Network for Organ Sharing database was reviewed to identify pediatric heart transplant recipients from 2005 through 2012. Patients were stratified into three groups: extracorporeal membrane oxygenation (ECMO), ventricular assist device (VAD), and direct transplantation (DTXP). The primary outcome was posttransplant survival.

RESULTS

Two thousand seven hundred seventy-seven pediatric patients underwent orthotopic heart transplantation. There were 617 patients who required BTT with mechanical circulatory support (22.2%), of whom there were 428 VAD BTT (69.4%) and 189 ECMO BTT (30.6%). An increase in VAD use was observed during the study period (p < 0.0001). Compared with DTXP, patients in the ECMO BTT group had a lower median age (<1 versus 5 years; p < 0.0001) and were significantly smaller (8 versus 14 kg; p < 0.001), whereas patients in the VAD BTT group were older (8 versus 5 years; p = 0.0002) and larger (24 versus 14 kg; p < 0.001). Actuarial survival was greater in the DTXP group compared with ECMO BTT, but similar to VAD BTT at 30 days and 1, 3, and 5 years. However, this survival difference was lost after censoring the first 4 months after transplant. In multivariable analysis, when restricted to the first 4 months of survival, independent predictors for mortality were ECMO BTT, age, diagnosis, and functional status, whereas VAD BTT was not.

CONCLUSIONS

Pediatric patients with DTXP or VAD BTT have equivalent posttransplant survival. However, those requiring ECMO BTT have inferior early posttransplant survival compared with those receiving DTXP.

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.

Effects of Cardiopulmonary Support With a Novel Pediatric Pump-Lung in a 30-Day Ovine Animal Model

The scarcity of donor organs has led to the development of devices that provide optimal long-term respiratory or cardiopulmonary support to bridge recipients as they wait for lung and/or heart transplantation. This study was designed to evaluate the 30-day in vivo performance of the newly developed pediatric pump-lung (PediPL) for cardiopulmonary support using a juvenile sheep model. The PediPL device was placed surgically between the right atrium and descending aorta in eight sheep (25.4-31.2 kg) and evaluated for 30 days. Anticoagulation was maintained with continuous heparin infusion (activated clotting time 150-200 s). The flow rate was measured continually, and gas transfer was measured daily. Plasma free hemoglobin, platelet activation, hematologic data, and blood biochemistry were assessed twice a week. Sheep were euthanized after 30 days. The explanted devices were examined for gross thrombosis. Six sheep survived for 30-32 days. During the study, the oxygen transfer rate of the devices was 54.9 ± 13.2 mL/min at a mean flow rate of 1.14 ± 0.46 L/min with blood oxygen saturation of 95.4% ± 1.7%. Plasma free hemoglobin was 8.2 ± 3.7 mg/dL. Platelet activation was 5.35 ± 2.65%. The animals had normal organ chemistries except for surgery-related transient alterations in kidney and liver function. Although we found some scattered thrombi on the membrane surfaces of some explanted devices during the necropsy, the device function and performance did not degrade. The PediPL device was capable of providing cardiopulmonary support with long-term reliability and good biocompatibility over the 30-day duration and offers the potential option for bridging pediatric patients with end-stage heart or lung disease to heart and/or lung transplantation.