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

Subnormothermic Machine Perfusion of Neonatal and Small-Sized Pediatric Donor Hearts

Donor heart machine perfusion enables avoidance of prolonged cold ischemia, however the optimal temperature is yet to be elucidated. Given that maintenance of temperature beyond ambient levels demands significant energy, we sought to determine the suitability of room-temperature perfusion preservation of neonatal/pediatric-sized (5-20 kg) piglet donor hearts. A custom device was fabricated suitable for this purpose, with continuous readout of perfusion pressure, flow rate, temperature, and oxygen saturation. Oxygen delivery was automated to keep saturation above 90%. The perfusate consisted of a 1:1 mix of donor whole blood and modified Krebs-Henseleit solution with albumin. Donor hearts were procured from 5 kg (n = 5), 10 kg (n = 3), and 20 kg (n = 5) piglets, and perfused for 10 hours. Subsequently, 20 kg piglet hearts were transplanted. Hemodynamic stability and echocardiographic measurement of donor heart function were evaluated posttransplant. Perfusate parameters were stable through the perfusion interval. Temperature was consistently 23.8 ± 1.6°C. pH (7.35 ± 0.09) and pO2 (102 ± 29 mm Hg) were steady throughout. Glucose (5.9 ± 1.8 mmol/L) and lactate (2.4 ± 1.5 mmol/L) were metabolized by the heart over the course of perfusion. Transplanted hearts displayed durable hemodynamics and good biventricular function. We conclude that neonatal and pediatric hearts can be safely perfused for extended periods at subnormothermic conditions using blood-based perfusate.

"Take it or leave it": Analysis of pediatric heart offers for transplantation in Switzerland

BACKGROUND

There is a shortage of donor hearts in Switzerland, especially for pediatric recipients. However, the rate and reason for refusals of pediatric donor hearts offered in Switzerland has not been systematically analyzed.

METHODS

The national transplant database, Swiss Organ Allocation System, was searched for all hearts from Swiss and foreign donors younger than 16 years from 2015 to 2020. The numbers of accepted and refused hearts and early outcome were assessed, and the reasons for refusal were retrospectively analyzed.

RESULTS

A total of 136 organs were offered to the three Swiss pediatric heart centers and foreign donor procurement organizations. Of these, 26/136 (19%) organs were accepted and transplanted: 18 hearts were transplanted in Switzerland, and 13 of these were foreign. Reasons for refusal were (1) no compatible recipient due to blood group or weight mismatch, 89.4%; (2) medical, meaning organ too marginal for transplantation, 7.4%; (3) logistic, 1.4%; and (4) other, 1.8%. Five organs were refused in Switzerland by one center but later accepted and successfully transplanted by another center. Hearts from outside Switzerland were transplanted significantly less than Swiss hearts (n = 16/120 vs. 10/16, p < .001).

CONCLUSION

The most common reason for refusing a pediatric donor heart is lack of compatibility with the recipient. Few hearts are refused for medical reasons. A more generous acceptance seems to be justified in selected patients. Switzerland receives a high number of foreign offers, but their rate of acceptance is lower than that of Swiss donations.

A modified intraventricular balloon method for functional assessment of hearts from donation after circulatory death

Objective

Functional assessment of hearts during ex-vivo heart perfusion is not well-established. Conventional intraventricular balloon methods for large animals sacrifice the mitral valve. This study assessed the effectiveness of the modified intraventricular balloon method in comparison with other modalities used during working mode in juvenile pigs.

Methods

Following asphyxia circulatory arrest, hearts were ischemic for 15 minutes and then reperfused on an ex-vivo device for 2 hours before switching to working mode. Left ventricular pressure was continuously measured during reperfusion by a saline-filled balloon fixated in the left atrium. Spearman Correlation Coefficients with linear regression lines with confidence intervals were analyzed.

Results

Maximum dp/dt at 90 minutes of reperfusion and minimum dp/dt at 60 minutes of reperfusion showed a moderate positive correlation to that in working mode, respectively (Rs = 0.61, P = .04 and Rs = 0.60, P = .04). At 60 minutes of reperfusion, minimum dp/dt showed moderate positive correlation to tau (Rs = 0.52, P = .08). Myocardial oxygen consumption during reperfusion consistently decreased at least 30% compared to working mode (at 90 minutes as the highest during reperfusion, 3.3 ± 0.8; in working mode, 5.6 ± 1.4, mLO2/min/100 g, P < .001).

Conclusions

Functional parameters of contractility and relaxation measured during reperfusion by the modified balloon method showed significant correlations to respective parameters in working mode. This mitral valve sparing technique can be used to predict viability and ventricular function in the early phase of ex-vivo heart perfusion without loading the heart during working mode.

Risk Index Predicts Pediatric Heart Allograft Non-Utilization

BACKGROUND

Children listed for heart transplantation face the highest waitlist mortality among all solid organ transplant patients (14%). Attempts at decreasing donor allograft non-utilization (41.5%) could potentially decrease waitlist mortality for pediatric heart transplant patients. Our aim was to quantify the non-utilization risk of pediatric donor heart allografts at the time of initial offering.

METHODS

Using the United Network of Organ Sharing (UNOS) database, we retrospectively analyzed 8823 deceased donors (≤18 years old) data through univariable and multivariable analysis and logistic regression models. These factors were divided into a training (n = 5882) and validation set (n = 2941). Donor clinical characteristics and laboratory values were used to predict non-utilization of donor hearts. The multivariable analysis used factors that were significant from the univariable analysis (p-value < .05), and the pediatric non-utilization risk index (pDRSI) included significant factors from the multivariable analysis, producing an overall risk score for non-utilization. With these data, we created a non-utilization risk index to predict likelihood of donor allograft non-utilization.

RESULTS

From the 24 potential factors that were identified from univariable analysis, 17 were significant predictors (p < .05) of pediatric heart non-utilization in the multivariable analysis. Low left ventricular ejection fraction (odds ratio (OR)-35.3), hepatitis C positive donor (OR-23.3), high left ventricular ejection fraction (OR-3.29), and hepatitis B positive donor (OR-3.27) were the most significant risk factors. The phDSRI has a C-statistic of 0.80 for the training set and 0.80 for the validation set.

CONCLUSION

Using over 8000 donors, the phDSRI uses 17 significant risk factors to predict risk of pediatric heart donor allograft non-utilization.

An integrated program to expand donor utilization in pediatric heart transplantation: Case report of successful transplant with multiple donor risk factors

BACKGROUND

Pediatric heart transplantation (HT) continues to be limited by the shortage of donor organs, distance constraints, and the number of potential donor offers that are declined due to the presence of multiple risk factors.

METHODS

We report a case of successful pediatric HT in which multiple risk factors were mitigated through a combination of innovative donor utilization improvement strategies.

RESULTS

An 11-year-old, 25-kilogram child with cardiomyopathy and pulmonary hypertension, on chronic milrinone therapy and anticoagulated with apixaban, was transplanted with a heart from a Hepatitis C virus positive donor and an increased donor-to-recipient weight ratio. Due to extended geographic distance, an extracorporeal heart preservation system (TransMedics™ OCS Heart) was used for procurement. No significant bleeding was observed post-operatively, and she was discharged by post-operative day 15 with normal biventricular systolic function. Post-transplant Hepatitis C virus seroconversion was successfully treated.

CONCLUSIONS

Heart transplantation in donors with multiple risk factor can be achieved with an integrative team approach and should be taken into consideration when evaluating marginal donors in order to expand the current limited donor pool in pediatric patients.

Optimal Donor Allograft Function: The Search for the Lowest Acceptable Donor Left Ventricular Ejection Fraction in Pediatric Heart Transplantation

BACKGROUND

The availability of heart donors is limited by organ shortage. Due to concerns of reduced survival, donors with depressed left ventricular ejection fraction (LVEF <50%) have been cautiously used in pediatric heart transplantation. One strategy to expand the donor pool is to re-evaluate whether lower donor LVEF may be acceptable for transplantation.

METHODS

We performed a multicenter retrospective cohort study of patients <18 y receiving heart transplants from April 2007 to September 2021 using the United Network of Organ Sharing dataset. We excluded retransplants and multiorgan transplants. Cut-point analyses of LVEF was performed and Kaplan-Meier method was used to compare 1-y survival for new cut-points and the standard (LVEF >50%).

RESULTS

The analytic sample consisted of 5255 patients. Recipients receiving hearts with lower LVEFs were more likely to be on ventilator and extracorporeal membrane oxygenation support. Recipients did not differ in waitlist times or transplant status. Cut-point analysis identified LVEF 45% as a potentially new cutoff. One-year survival of recipients of donors with LVEF ≥45% (92.1%; 95% confidence interval [CI], 91.3%-92.8%) was similar to that of LVEF >50% (92.1%; CI, 91.4%-92.9%). Survival for the LVEF 45%-49% (88.8%; CI, 72.9%-95.7%) cohort was slightly lower than the ≥50% cohort, albeit nonsignificant.

CONCLUSIONS

One-year survival among pediatric heart transplants using a donor heart LVEF threshold of 45% or 40% was similar to a threshold of 50%. However, the finding is based on a small number of patients with LVEF <50%, and future larger prospective studies are warranted to confirm the findings of this study before a lower LVEF threshold is considered.

Do vasoactive medications impact donor hearts clinical outcomes in pediatric heart transplantation?

OBJECTIVES

There is limited data examining donor vasopressor and/or inotrope medications (vasoactives) on pediatric orthotopic heart transplant (OHT) outcomes. We aim to evaluate the effects of vasoactives on pediatric OHT outcomes.

METHODS

The United Network for Organ Sharing database was retrospectively reviewed from January 2000 to March 2018 for donor hearts. Exclusion criteria included multiorgan transplants and recipient age >18. Donors receiving vasoactives at the time of procurement were compared to donors not on vasoactives, including the number of vasoactives and the type. End-points of interest were survival at 30 days and 1 year as well as post-transplant rejection at 1 year. Logistic and Cox models were used to quantify survival end-points.

RESULTS

Of 6462 donors, 3187 (49.3%) were receiving at least one vasoactive. Comparing any vasoactive medication versus none, there was no difference in 30-day survival (p = .27), 1 year survival (p = .89), overall survival (p = .68), or post-transplant rejection (p = .98). There was no difference in 30-day survival for donors receiving 2 or more vasoactive infusions (p = .89), 1 year survival (p = .53), overall survival (p = .75), or post-transplant rejection at 1 year (p = .87). Vasopressin was associated with decreased 30-day mortality (OR = 0.22; p = .028), dobutamine with decreased 1-year mortality (OR = 0.37; p = .036), overall survival (HR = 0.51; p = .003), and decreased post-transplant rejection (HR = 0.63; p = .012).

CONCLUSIONS

There is no difference in pediatric OHT outcomes when the cardiac donor is treated with vasoactive infusions at procurement. Vasopressin and dobutamine were associated with improved outcomes. This information can be used to guide medical management and donor selection.

Partial heart transplantation can ameliorate donor organ utilization

BACKGROUND

The treatment of babies with unrepairable heart valve dysfunction remains an unsolved problem because there are no growing heart valve implants. However, orthotopic heart transplants are known to grow with recipients.

AIM

Partial heart transplantation is a new approach to delivering growing heart valve implants, which involves transplantation of the part of the heart containing the valves only. In this review, we discuss the benefits of this procedure in children with unrepairable valve dysfunction.

CONCLUSION

Partial heart transplantation can be performed using donor hearts with poor ventricular function and slow progression to donation after cardiac death. This should ameliorate donor heart utilization and avoid both primary orthotopic heart transplantation in children with unrepairable heart valve dysfunction and progression of these children to end-stage heart failure.

Impact of occurrence of cardiac arrest in the donor on long-term outcomes of pediatric heart transplantation

OBJECTIVE

The impact of cardiac arrest in the donor on long-term outcomes of pediatric heart transplantation has not been studied.

METHODS

The UNOS database was queried for primary pediatric heart transplantation (1999-2020). The cohort was divided into recipients who received a cardiac allograft from a donor who had a cardiac arrest (CA) versus a donor who did not (NCA). Univariable and multivariable analysis was done to compare recipient outcomes, followed by survival analysis using the Kaplan-Meier method.

RESULTS

A total of 7300 patients underwent heart transplantation, of which 579 (7.9%) patients belonged to the CA group. The CA group was younger (median 3 vs. 5 years, p < .001), male (51% vs. 47%, p = .03), and smaller in weight (13 vs. 17 kg, p < .001) and height (101 vs. 109 cm, p < .001) than the NCA group. The groups were similar in recipient heart failure diagnosis and blood type. The CA donors were younger (3 vs. 6 years, p < .001) versus nonwhite (48% vs. 45%, p = .003) and died from drowning and asphyxiation compared to blunt injury and intracranial hemorrhage in the NCA group. The left-ventricular ejection fraction was similar between the groups. There was no difference in VAD and ECMO use before the transplant. The listing status, waitlist days, and allograft ischemic times were similar. Posttransplant morbidity such as stroke, dialysis, pacemaker implantation, and treated rejection were similar. Donor cardiac arrest (hazard ratio = 0.93, p = .5) was not an independent predictor of mortality on multivariable analysis. There was no survival difference even beyond 20 years of follow-up between the groups (p = .88).

CONCLUSION

The occurrence of donor cardiac arrest has no impact on long-term survival in pediatric heart transplant recipients.

Extreme size mismatch: bronchus compression by an oversized donor heart in small children

Studies have suggested that a more liberal criterion of donor–recipient weight ratio (DRWR) is associated with superior waitlist survival without compromising posttransplant outcomes in selected critically ill patients. Successful transplantation of an extremely oversized donor heart into a small recipient is herein described. A 2-year-old girl accepted a size-mismatched adult donor heart offer (DRWR of 4.4) due to frequent complications with a left ventricular assist device. During the immediate postoperative period, spatial constraints within the thoracic cavity compromised graft function. Computed tomography revealed severe compression of the left bronchus due to the oversized allograft with lobar collapse of the left lung. With temporary extracorporeal membrane oxygenation support, graft function improved within 1 month after transplantation. Subsequent adaptive size remodeling of the transplanted heart with concomitant left bronchus re-expansion was observed within 6 months after transplantation. Despite a complicated posttransplant recovery, the patient was discharged home with minimal respiratory sequelae. Our report describes an alternative strategy for managing early morbidities related to an oversized graft and supports extending the criteria of size matching in pediatric heart transplantations.

Don't Throw Your Heart Away: Increased Transparency of Donor Utilization Practices in Transplant Center Report Cards Alters How Center Performance Is Evaluated

BACKGROUND

Publicly available report cards for transplant centers emphasize posttransplant survival and obscure the fact that some centers reject many of the donor organs they are offered (reflecting a conservative donor acceptance strategy), while others accept a broader range of donor offers (reflecting an open donor acceptance strategy).

OBJECTIVE

We assessed how the provision of salient information about donor acceptance practices and waitlist survival rates affected evaluation judgments of hospital report cards given by laypeople and medical trainees.

METHODS

We tested 5 different report card formats across 4 online randomized experiments (n1 = 1,003, n2 = 105, n3 = 123, n4 = 807) in the same hypothetical decision. The primary outcome variable was a binary choice between transplant hospitals (one with an open donor acceptance strategy and the other with a conservative donor acceptance strategy).

RESULTS

Report cards featuring salient information about donor organ utilization rates (transplant outcomes categorized by quality of donor offers accepted) or overall survival rates (outcomes from both waitlist and transplanted patients) led lay participants (studies 1, 3, and 4) and medical trainees (study 2) to evaluate transplant centers with open donor acceptance strategies more favorably than centers with conservative strategies.

LIMITATIONS

Due to the nature of the decision, a hypothetical scenario was necessary for both ethical and practical reasons. Results may not generalize to transplant clinicians or patients faced with the decision of where to join the transplant waitlist.

CONCLUSIONS

These findings suggest that performance evaluations for transplant centers may vary significantly based not only on what outcome information is presented in report cards but also how the information is displayed.

Decline of increased risk donor offers increases waitlist mortality in paediatric heart transplantation

BACKGROUND

Increased risk donors in paediatric heart transplantation have characteristics that may increase the risk of infectious disease transmission despite negative serologic testing. However, the risk of disease transmission is low, and refusing an IRD offer may increase waitlist mortality. We sought to determine the risks of declining an initial IRD organ offer.

METHODS AND RESULTS

We performed a retrospective analysis of candidates waitlisted for isolated PHT using 20072017 United Network of Organ Sharing datasets. Match runs identified candidates receiving IRD offers. Competing risks analysis was used to determine mortality risk for those that declined an initial IRD offer with stratified Cox regression to estimate the survival benefit associated with accepting initial IRD offers. Overall, 238/1067 (22.3%) initial IRD offers were accepted. Candidates accepting an IRD offer were younger (7.2 versus 9.8 years, p < 0.001), more often female (50 versus 41%, p = 0.021), more often listed status 1A (75.6 versus 61.9%, p < 0.001), and less likely to require mechanical bridge to PHT (16% versus 23%, p = 0.036). At 1- and 5-year follow-up, cumulative mortality was significantly lower for candidates who accepted compared to those that declined (6% versus 13% 1-year mortality and 15% versus 25% 5-year mortality, p = 0.0033). Decline of an IRD offer was associated with an adjusted hazard ratio for mortality of 1.87 (95% CI 1.24, 2.81, p < 0.003).

CONCLUSIONS

IRD organ acceptance is associated with a substantial survival benefit. Increasing acceptance of IRD organs may provide a targetable opportunity to decrease waitlist mortality in PHT.

A novel method of donor‒recipient size matching in pediatric heart transplantation: A total cardiac volume‒predictive model

BACKGROUND

The pediatric heart transplant community uses weight-based donor-to-recipient size matching almost exclusively, despite no evidence to validate weight as a reliable surrogate of cardiac size. Donor size mismatch is the second most common reason for the refusal of donor hearts in current practice (∼30% of all refusals). Whereas case-by-case segmentation of total cardiac volume (TCV) by computed tomography (CT) for direct virtual transplantation is an attractive option, it remains limited by the unavailability of donor chest CT. We sought to establish a predictive model for donor TCV on the basis of anthropomorphic and chest X-ray (CXR) cardiac measures.

METHODS

Banked imaging studies from 141 subjects with normal CT chest angiograms were obtained and segmented using 3-dimensional modeling to derive TCV. CXR data were available for 62 of those subjects. A total of 3 predictive models of TCV were fit through multiple linear regression using the following variables: Model A (weight only); Model B (weight, height, sex, and age); Model C (weight, height, sex, age, and 1-view anteroposterior CXR maximal horizontal cardiac width).

RESULTS

Model C provided the most accurate prediction of TCV (optimism corrected R2 = 0.99, testing set R2 = 0.98, mean absolute percentage error [MAPE] = 8.6%) and outperformed Model A (optimism corrected R2 = 0.94, testing set R2 = 0.94, MAPE = 16.1%) and Model B (optimism corrected R2 = 0.97, testing set R2 = 0.97, MAPE = 11.1%).

CONCLUSIONS

TCV can be predicted accurately using readily available anthropometrics and a 1-view CXR from donor candidates. This simple and scalable method of TCV estimation may provide a reliable and consistent method to improve donor size matching.

A coordinated approach to improving pediatric heart transplant waitlist outcomes: A summary of the ACTION November 2019 waitlist outcomes committee meeting

The number of children needing heart transplantation continues to rise. Although improvements in heart failure therapy, particularly durable mechanical support, have reduced waitlist mortality, the number of children who die while waiting for a suitable donor organ remains unacceptably high. Roughly, 13% of children and 25% of infants on the heart transplant waitlist will not survive to transplantation. With this in mind, the Advanced Cardiac Therapies Improving Outcomes Collaborative Learning Network (ACTION), through its Waitlist Outcomes Committee, convened a 2-day symposium in Ann Arbor, Michigan, from 2-3 November 2019, to better understand the factors that contribute to pediatric heart transplant waitlist mortality and to focus future efforts on improving the organ allocation rates for children needing heart transplantation. Using improvement science methodology, the heart failure-transplant trajectory was broken down into six key steps, after which modes of failure and opportunities for improvement at each step were discussed. As a result, several projects aimed at reducing waitlist mortality were initiated.

Pediatric donor heart allocation in the United States, 2006-2017: Current patterns and potential for improvement

OBJECTIVE

To understand current donor heart allocation practices for pediatric transplantation.

BACKGROUND

Despite high waitlist mortality rates among pediatric patients awaiting transplant, a substantial proportion of donor hearts go unused. Analysis of UNOS match run data may identify opportunities to optimize organ utilization.

METHODS

Using UNOS/OPTN data, we evaluated all match runs for pediatric (<18 years) donor hearts from 1/1/2006 to 3/31/2017. We assessed final disposition of donor hearts, reasons for donor refusal, and other match run characteristics. Variation in total offers made per organ, and refusal rates by OPOs were also evaluated.

RESULTS

Of 7585 pediatric potential donor hearts, 2226 (29.3%) were refused. Hearts accepted underwent a median of 2 offers (IQR: 1-5), compared to 11 (IQR: 5-24) for refused donor hearts. Organ refusal rates decreased from 36.9% in 2006-2009 to 22.3% in 2014-2017 (P < .001). Reasons for refusal included quality (80.9%), size mismatch (57.5%), and known/suspected crossmatch positivity (39.1%). Among 1800 hearts deemed "poor quality" by ≥1 transplant program, less than half (46.6%) were coded "poor quality" by multiple refusing programs. Organ refusal rates ranged from 13.5% to 83.3% across OPOs, and there was no correlation between refusal rates and median number of offers made by the OPO.

CONCLUSION

Although more organs are being used over time, 1 in 5 available pediatric donor hearts are still discarded. The lack of donor evaluation consensus and wide variability in donor refusal rates indicates a need for standardization of donor assessment and match run processes across OPOs.

Pediatric donor management to optimize donor heart utilization

Optimal management of pediatric cardiac donors is essential in order to maximize donor heart utilization and minimize the rate of discarded organs. This review was performed after a systematic literature review and gives a detailed overview on current practices and guidelines. The review focuses on optimal monitoring of pediatric donors, donor workup, hormonal replacement, and obliterating the adverse effects of brain death. The current evidence on catecholamine support and thyroid hormone replacement is also discussed. Recognizing and addressing this shall help in a standardized approach toward donor management and optimal utilization of pediatric heart donors organs.

Review of interactions between high-risk pediatric heart transplant recipients and marginal donors including utilization of risk score models

BACKGROUND

Donor organ acceptance practices vary among pediatric heart transplant professionals. We sought to understand what is known about the interactions between the "high-risk" recipient and the "marginal donor," and how donor risk scores can impact this discussion.

METHODS

A systematic review of published literature on pediatric HTx was undertaken with the assistance of a medical librarian. Two authors independently assessed search results, and papers were reviewed for inclusion.

RESULTS

We found that there are a large number of individual factors, and clusters of factors, that have been used to label individual recipients "high-risk" and individual donors "marginal." The terms "high-risk recipient" and "marginal donor" have been used broadly in the literature making it virtually impossible to make comparisons between publications. In general, the data support that patients who could be easily agreed to be "sicker recipients" are at more risk compared to those who are clearly "healthier," albeit still "sick enough" to need transplantation. Given this variability in the literature, we were unable to define how being a "high-risk" recipient interplays with accepting a "marginal donor." Existing risk scores are described, but none were felt to adequately predict outcomes from factors available at the time of offer acceptance.

CONCLUSIONS

We could not determine what makes a donor "marginal," a recipient "high-risk," or how these factors interplay within the specific recipient-donor pair to determine outcomes. Until there are better risk scores predicting outcomes at the time of organ acceptance, programs should continue to evaluate each organ and recipient individually.

Review of the discard and/or refusal rate of offered donor hearts to pediatric waitlisted candidates

We aimed to review current literature on the discard rate of donor hearts offered to pediatric recipients and assess geographical differences. Consequences and ways to reduce the discard rate are discussed. A systemic review on published literature on pediatric transplantation published in English since 2010 was undertaken. Additionally, a survey was sent to international OPOs with the goal of incorporating responses from around the world providing a more global picture. Based on the literature review and survey, there is a remarkably wide range of discard and/or refusal for pediatric hearts offered for transplant, ranging between 18% and 57% with great geographic variation. The data suggest that that the overall refusal rate may have decreased over the last decade. Reasons for organ discard were difficult to identify from the available data. Although the refusal rate of pediatric donor hearts seems to be lower compared to that reported in adults, it is still as high as 57% with geographic variation.

Effects of donor cause of death, ischemia time, inotrope exposure, troponin values, cardiopulmonary resuscitation, electrocardiographic and echocardiographic data on recipient outcomes: A review of the literature

BACKGROUND

Heart transplantation has become standard of care for pediatric patients with either end-stage heart failure or inoperable congenital heart defects. Despite increasing surgical complexity and overall volume, however, annual transplant rates remain largely unchanged. Data demonstrating pediatric donor heart refusal rates of 50% suggest optimizing donor utilization is critical. This review evaluated the impact of donor characteristics surrounding the time of death on pediatric heart transplant recipient outcomes.

METHODS

An extensive literature review was performed to identify articles focused on donor characteristics surrounding the time of death and their impact on pediatric heart transplant recipient outcomes.

RESULTS

Potential pediatric heart transplant recipient institutions commonly receive data from seven different donor death-related categories with which to determine organ acceptance: cause of death, need for CPR, serum troponin, inotrope exposure, projected donor ischemia time, electrocardiographic, and echocardiographic results. Although DITs up to 8 hours have been reported with comparable recipient outcomes, most data support minimizing this period to <4 hours. CVA as a cause of death may be associated with decreased recipient survival but is rare in the pediatric population. Otherwise, however, in the setting of an acceptable donor heart with a normal echocardiogram, none of the other data categories surrounding donor death negatively impact pediatric heart transplant recipient survival.

CONCLUSIONS

Echocardiographic evaluation is the most important donor clinical information following declaration of brain death provided to potential recipient institutions. Considering its relative importance, every effort should be made to allow direct image visualization.

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.

Behavioral economics-A framework for donor organ decision-making in pediatric heart transplantation

The high discard rate of pediatric donor hearts presents a major challenge for children awaiting heart transplantation. Recent literature identifies several factors that contribute to the disparities in pediatric donor heart usage, including regulatory oversight, the absence of guidelines on pediatric donor heart acceptance, and variation among transplant programs. However, a likely additional contributor to this issue are the behavioral factors influencing transplant team decisions in donor offer scenarios, a topic that has not yet been studied in detail. Behavioral economics and decision psychology provide an excellent foundation for investigating decision-making in the pediatric transplant setting, offering key insights into the behavior of transplant professionals. We conducted a systematic review of published literature in pediatric heart transplant related to behavioral economics and the psychology of decision-making. In this review, we draw on paradigms from these two domains in order to examine how existing aspects of the transplant environment, including regulatory oversight, programmatic variation, and allocation systems, may precipitate potential biases surrounding donor offer decisions. Recognizing how human decision behavior influences donor acceptance is a first step toward improving utilization of potentially viable pediatric donor hearts.

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.

Volumetrics and fit assessments for donor to recipient size matching in pediatric heart transplantation: Is it time for a new paradigm?

Pediatric heart transplant patients face the highest waitlist mortality in solid organ transplantation. Given the relatively fixed number of donor organs becoming available each year, improving donor organ utilization could potentially have significant impact on reducing waitlist mortality. Donor to recipient weight ratio has historically been used to identify suitable donors; however, this method does not take into account the potential for significant variance in heart size due to complex congenital heart disease or underlying cardiomyopathy. We believe, based on our experience to date, that donor matching based upon weight ratios should be augmented by improved methodologies that provide a more accurate assessment of heart volumes. Herein we describe the rationale for these methodologies and our single-center experience using volumetrics as an alternative for donor fit assessments.

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.

Utilizing increased risk for disease transmission (IRD) kidneys for pediatric renal transplant recipients

BACKGROUND

Strategies to expand numbers of deceased donor kidneys suitable for pediatric recipients are urgently needed to prevent long-term dialysis-associated morbidity and mortality. Donors designated as increased risk of disease transmission (IRD) are infrequently used in pediatric recipients. We examined outcomes of these kidneys in pediatric patients and the potential to increase the donor pool.

METHODS

The United Network for Organ Sharing (UNOS) database records presence of IRD in all deceased donors since 2004. All pediatric kidney transplant recipients from 2004 to 2017 were identified and stratified by IRD status, and outcomes were examined.

RESULTS

Four hundred seventy-three pediatric kidney transplant recipients received an IRD allograft. IRD donors had lower kidney donor profile index (KDPI); were more likely to be younger, male, and Caucasian; and were more likely to have used drugs. IRD kidneys were more likely to have been biopsied and placed on pulsatile perfusion. Other than an older recipient age, demographic data were not different between groups. Allograft and patient survivals were similar, as were rejection and delayed graft function rates. Compared with adult recipients and adult IRD recipients, pediatric recipients were more likely to have a younger donor, receive a kidney with a lower creatinine, and were less likely to have delayed graft function (p < 0.05). There were no recorded disease transmissions in IRD group.

CONCLUSIONS

Patient and allograft survivals are similar in IRD and non-IRD kidneys. High-quality IRD organs used in adults represent a large number of donors with excellent outcomes. IRD allografts have a potential to increase transplant volume and should be considered for pediatric patients.

Donor considerations in pediatric heart transplantation

Donors for pediatric heart transplantation are accepted based on variety of donor factors. There is wide variability in practice across centers and lack of evidence to guide standardized approach for some donor characteristics. This article reviews current practice and evidence for donor evaluation in pediatric heart transplantation.

Variability in donor selection among pediatric heart transplant providers: Results from an international survey

There is considerable variability in donor acceptance practices among adult heart transplant providers; however, pediatric data are lacking. The aim of this study was to assess donor acceptance practices among pediatric heart transplant professionals. The authors generated a survey to investigate clinicians' donor acceptance practices. This survey was distributed to all members of the ISHLT Pediatric Council in April 2018. A total of 130 providers responded from 17 different countries. There was a wide range of acceptable criteria for potential donors. These included optimal donor-to-recipient weight ratio (lower limit: 50%-150%, upper limit: 120%-350%), maximum donor age (25-75 years), and minimum acceptable left ventricular EF (30%-60%). Non-US centers demonstrated less restrictive donor selection criteria and were willing to accept older donors (50 vs 35 years, P < 0.001), greater size discrepancy (upper limit weight ratio 250% vs 200%, P = 0.009), and donors with a lower EF (45% vs 50%, P < 0.001). Recipient factors were most influential in the decision to accept marginal donors including recipients requiring ECMO support, ventilator support, and highly sensitized patients with a negative XM. However, programmatic factors impacted the decision to decline marginal donors including recent programmatic mortalities and concerns for programmatic restrictions from regulatory bodies. There is significant variation in donor acceptance practices among pediatric heart transplant professionals. Standardization of donor acceptance practices through the development of a consensus statement may help to improve donor utilization and reduce waitlist mortality.

Time for evidence-based, standardized donor size matching for pediatric heart transplantation

BACKGROUND

Accurately predicting cardiac size by other body parameters has long been problematic to determine whether a donor heart will serve a given waitlist candidate, yet hundreds of heart donors are turned down annually for size mismatch.

OBJECTIVES

We sought to describe how donor body weight parameters are currently utilized in cardiac transplantation and its influence on waitlist outcomes.

METHODS

From the United Network for Organ Sharing database, pediatric (age <18 years) heart transplant candidates were divided into lower quartile, interquartile, and upper quartile categories based on final maximum acceptable donor-candidate weight ratio (DCW), expressed as percentage. Baseline characteristics and waitlist outcomes, including monthly offers/candidate and survival were compared.

RESULTS

Overall median DCW was 200% (range, 159%-241%). Patients with congenital heart disease had higher DCW than those with cardiomyopathy (223% vs 203%; P < .001). Number of monthly offers/candidate (5.0, 5.6, and 7.2, respectively; P < .001) increased with quartile of DCW. Posttransplant survival was similar amongst the groups (log-rank P > .05). Subgroup analysis of critically ill children showed a waitlist survival advantage in those listed with a DCW ≥200% (P < .001).

CONCLUSIONS

Despite substantial practice variation in acceptable donor weight in pediatric heart transplantation, patients listed with variable DCW had similar posttransplant survival. However, in critically ill patients, higher DCW was associated with greater waitlist survival. Better understanding of the importance of donor weight could reduce practice variability and improve organ use and waitlist outcomes for pediatric cardiac transplant candidates.