Increasing donor-recipient weight mismatch in pediatric orthotopic heart transplantation does not adversely affect outcome

Assessing Donor-Recipient Size Mismatch in Pediatric Heart Transplantation: Lessons Learned From Over 7,500 Transplants

BACKGROUND

To date, no studies have identified an optimal metric to match donor-recipient (D-R) pairs in pediatric heart transplantation (HT).

OBJECTIVES

This study sought to identify size mismatch metrics that predicted graft survival post-HT.

METHODS

D-R pairs undergoing HT in Pediatric Heart Transplant Society database from 1993 to 2021 were included. Effects of size mismatch by height, weight, body mass index, body surface area, predicted heart mass, and total cardiac volume (TCV) on 1- and 5-year graft survival and morbidity outcomes (rejection and cardiac allograft vasculopathy) were evaluated. Cox models with stepwise selection identified size metrics that independently predicted graft survival.

RESULTS

Of 7,715 D-R pairs, 36.0% were well matched (D-R ratio: -20% to +20%) by weight, 39.0% by predicted heart mass, 50.0% by body surface area, 57.0% by body mass index, 71.0% by height, and 93.0% by TCV. Of all size metrics, only D-R mismatch by height and TCV predicted graft survival at 1 and 5 years. Effects of D-R size mismatch on graft survival were nonlinear. At both 1 and 5 years post-HT, D-R undersizing and oversizing by height led to increased graft loss, with graft loss observed more frequently with undersizing. Moderately undersized donors by height (D-R ratio: <-30%) frequently experienced rejection post-HT (P < 0.001). Assessing D-R size matching by TCV, minimal donor undersizing was protective, while oversizing up to 25% was not associated with increased graft loss.

CONCLUSIONS

In pediatric HT, D-R appear most optimally matched using TCV. Only D-R size mismatch by TCV and height independently predicts graft survival. Standardizing size matching across centers may reduce donor discard.

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.

Total ventricular mass oversizing +50% or greater was a predictor of worse 1-year survival after heart transplantation

OBJECTIVES

Current donor-recipient size matching guidelines rely primarily on body weight, with no specified oversizing cutoff values. Recent literature has explored predicted total ventricular mass matching over body weight matching. We aim to explore the impact of total ventricular mass oversizing on heart transplant outcomes.

METHODS

The United Network for Organ Sharing database was queried for adults who underwent primary heart transplant from 1997 to 2017. By using validated equations, donor-recipient total ventricular mass mismatch was calculated. Donor-recipient pairs were divided into 3 groups by total ventricular mass mismatch. Post-heart transplant 1-year survival was analyzed using the Kaplan-Meier method and Cox proportional hazards models. We also investigated post-heart transplant complications, independent predictors for mortality, donor-recipient sex mismatch, and donor-recipient body habitus in total ventricular mass mismatch greater than +50%.

RESULTS

A total of 34,455 donor-recipient pairs were included. Fractional polynomial regression demonstrated increased the risk of mortality with higher total ventricular mass mismatch. Total ventricular mass mismatch of +48.3% maximized the Youden Index. Donor-recipient pairs were subsequently grouped by total ventricular mass mismatch as -20% to +30%, +30% to +50%, and greater than +50%. Total ventricular mass mismatch greater than +50% was an independent risk factor for 1-year mortality (hazard ratio, 1.40, P = .004) and was associated with increased postoperative stroke (P = .002). Some 80.3% of these recipients were smaller female patients with male donors. Total ventricular mass mismatch from +30% to +50% was not associated with worse survival (P = .17).

CONCLUSIONS

Total ventricular mass mismatch greater than +50% is associated with worse 1-year survival, although this group comprises a small portion of heart transplant. total ventricular mass mismatch from +30% to +50% is not associated with worse survival. These outcomes should be considered in selecting donors and in efforts to expand the potential donor pool.

Impact of size matching on survival post-heart transplant in infants: Estimated total cardiac-volume ratio outperforms donor-recipient weight ratio

BACKGROUND

Cardiac volume-based estimation offers an alternative to donor-recipient weight ratio (DRWR) in pediatric heart transplantation (HT) but has not been correlated to posttransplant outcomes. We sought to determine whether estimated total cardiac volume (eTCV) ratio is associated with HT survival in infants.

METHODS

The United Network for Organ Sharing database was used to identify infants (aged <1 year) who received HT in 1987-2020. Donor and recipient eTCV were calculated from weight using previously published data. Patient cohort was divided acc ording to the significant range of eTCV ratio; characteristics and survival were compared.

RESULTS

A total of 2845 infants were identified. Hazard ratio with cubic spline showed prognostic relationship of eTCV ratio and DRWR with the overall survival. The cut point method determined an optimal eTCV ratio range predictive of infant survival was 1.05 to 1.85, whereas no range for DRWR was predictive. Overall, 75.6% of patients had an optimal total cardiac volume ratio, while 18.1% were in the lower (LR) and 6.3% in the higher (HR) group. Kaplan-Meier analysis showed better survival for patients within the optimal vs LR (p = 0.0017) and a similar significantly better survival when compared to HR (p = 0.0053). The optimal eTCV ratio group (n = 2,151) had DRWR, ranging from 1.09 to 5; 34.3% had DRWR of 2% to 3%, and 5.0% had DRWR of >3.

CONCLUSIONS

Currently, an upper DRWR limit has not been established in infants. Therefore, determining the optimal eTCV range is important to identify an upper limit that significantly predicts survival benefit. This finding suggests a potential increase in donor pool for infant recipients since over 40% of donors in the optimal eTCV range include DRWR values >2 that are traditionally not considered for candidate listing.

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.

Female donor hearts can improve survival for male pediatric heart transplant recipients

BACKGROUND

Both gender- and weight-matching between donor and recipient are thought to impact survival in pediatric heart transplantation, with clinical dogma holding that male donor hearts and "ideal" weight-matching yield superior survival. The composite impacts of gender and weight on post-transplant survival (PTS) are understudied.

METHODS

All pediatric (age <18) heart recipients between 1989 and 2021 with the complete recipient and donor gender and weight data were identified in the United Network for Organ Sharing database. Patients were grouped by recipient-donor gender (M & F) and donor-to-recipient weight ratio (DRWR; undersized [<0.8], ideal-sized [0.8-1.5], oversized [>1.5]).

RESULTS

A total of 10 697 patients were identified. Among male recipients, PTS was greatest with oversized DRWR from either male or female donors (median 22.4 and 20.6 years; p < .001 vs. others) and lowest for undersized DRWR from either male or female donors (median 13.4 and 13.2 years; p < .001 vs. others). The majority (64%) of male recipients received ideal-sized DRWR, among which female donor hearts yielded superior survival to males (median 18.9 vs. 17.4 years, p = .014). No differences in PTS existed for female recipients on the basis of gender-match, DRWR, and gender/DRWR together (all p > .1).

CONCLUSIONS

When considered together, gender and DRWR pairings impact PTS in male-but not female-pediatric heart transplant recipients. For males receiving ideal-sized DRWR organs (most common pairing, >60%), male recipients achieve superior survival when female donor hearts are transplanted. These findings suggest that if weight is being used for size-matching, donor gender should also be considered, particularly for male recipients.

Influence of Body Mass Index in Donor-Recipient Size Mismatch in Pediatric Heart Transplantation

BACKGROUND

Body weight is the traditional metric for matching donor and recipient size for pediatric heart transplantation (pHT). We hypothesized that mismatch in body mass index (BMI) or body surface area (BSA) rather than weight is better associated with outcomes of transplantation and therefore should be used for donor-recipient size matching.

METHODS

Analysis of the United Network for Organ Sharing database limited to pHT recipients was performed. Donor and recipient mismatch groups were created for weight, BMI, and BSA ratios. Differences in recipient characteristics between each cohort and the impact of mismatch on outcomes were statistically analyzed.

RESULTS

A total of 4,465 patients were included in the analysis of which 43% had congenital heart disease (CHD). There were significant differences in patient characteristics by matching, independent of the matching parameter. Multivariable regression analysis showed that a low donor-recipient BMI ratio (compared to normal) (CHD OR 1.70; non-CHD 2.78) was a predictor of one-year mortality (all P < .001) in both CHD and non-CHD cohorts. Low BMI ratio was also associated with worse long-term survival in non-CHD groups, but not in the CHD cohort. Weight and BSA ratio did not predict one year or long-term survival.

CONCLUSION

The use of low BMI donors compared to recipient may predict poor early and long-term survival and therefore should be avoided in pHT. The use of BMI matching may improve donor-recipient matching in pHT.

Infant heart transplantation with extremely oversized donor heart: is the donor–recipient size matching too conservative?

Heart transplantation (HTx) remains the gold standard treatment for end-stage heart failure in children but is restricted due to the limitation of donors. The donor-recipient weight ratio (DRWR) of 0.8-2.5 was the main selection criterion, and reports were particularly scarce in cases of DRWR > 3.0. We present an infant HTx case with DRWR of 6.5. The recipient was a 66-day-old female infant, weighing 3 kg, diagnosed with complex congenital heart disease and refractory severe heart failure, whereas the donor was a 4-year-old girl weighing 19.5 kg. The phased delayed sternal closure was performed and accomplished on the 23rd day after operation without wound infection. After treating complications with extracorporeal membrane oxygenation, peritoneal dialysis, and mechanical ventilation, the patient was successfully discharged. After 1 year of follow-up, the patient was still in optimal condition. Extending DRWR range may help enlarge the donor pool and shorten recipients' waiting time.

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.

Donor-Recipient Weight Match in Pediatric Heart Transplantation: Liberalizing Weight Matching with Caution

(1) Background: To expand the donor pool, greater donor hearts tended to be used in heart transplantation. However, the data about the feasibility of expanding the donor and recipient weight ratios (DRWRs. All donor and recipient weight ratio (DRWR) in this study or cited from other articles were converted to the DRWR calculated by ((donor weight-recipient weight)/recipient weight) × 100%.) to >30% was still scant in China’s pediatric heart transplantation (HTx). The potential risk increased along with the further expansion of the appropriate range of DRWR to >30% and its upper limit was still in debate. (2) Methods: Seventy-eight pediatric patients (age < 18 years) undergoing HTx between 2015 and 2020 at our center were divided into two groups based on the DRWR (>30% and ≤30%). Variables were summarized and analyzed via univariate analyses and multivariate analyses. A Kaplan-Meier methodology was used to calculate survival and conditional survival. (3) Results: No significant difference was found in one-year, three-year or five-year survival between the two groups. (4) Conclusions: The expansion of DRWR to >30% was acceptable for China’s pediatric HTx. Notably, continuously liberalizing of the upper DRWR boundary to more than 200% could be used as a stop-loss option but should be applied with caution.

Oversized donor heart transplantation-clinical experience with an underestimated problem

PURPOSE

Heart transplantation is the definitive treatment for end-stage heart failure. With respect to donor-recipient size matching, the problems with undersized heart transplantation have been widely discussed, but there is a paucity of information on oversized transplants due to the presumed advantage of large hearts. We intend to share our center's experience with oversized heart transplantation and its associated problems which would help to expand the knowledge on oversized cardiac allografts.

METHODS

Patients who underwent isolated heart transplantation at our hospital between March 1, 2008, and March 1, 2020, were included. For adults, a donor-recipient predicted heart mass percentage difference exceeding 30% and for children, a donor-recipient weight ratio < 0.8 and > 2.0 was considered a mismatch. We collected data from the in-patient medical records and analyzed the in-hospital outcomes and survival post-transplant among various other parameters.

RESULTS

Out of the 43 patients included in this study, 32 (74.4%) patients received a matched heart and 11 (25.6%) patients received oversized hearts. None of the patients received an undersized heart. The in-hospital mortality rate of oversized transplants was 18.2% whereas that of matched transplants was 9.4% (p = 0.432). The post-operative characteristics and 1-year survival were comparable between the groups. We encountered problems specific to oversizing in 5 of the 11 patients (45.4%) which are discussed.

CONCLUSION

With the liberalization of donor criteria to overcome organ shortage, oversized heart transplantation poses certain unique challenges, which when efficiently managed offers acceptable outcomes.

Pediatric heart transplantation: how to manage problems affecting long-term outcomes?

Since the initial International Society of Heart Lung Transplantation registry was published in 1982, the number of pediatric heart transplantations has increased markedly, reaching a steady state of 500-550 transplantation annually and occupying up to 10% of total heart transplantations. Heart transplantation is considered an established therapeutic option for patients with end-stage heart disease. The long-term outcomes of pediatric heart transplantations were comparable to those of adults. Issues affecting long-term outcomes include acute cellular rejection, antibody-mediated rejection, cardiac allograft vasculopathy, infection, prolonged renal dysfunction, and malignancies such as posttransplant lymphoproliferative disorder. This article focuses on medical issues before pediatric heart transplantation, according to the Korean Network of Organ Sharing registry and as well as major problems such as graft rejection and cardiac allograft vasculopathy. To reduce graft failure rate and improve long-term outcomes, meticulous monitoring for rejection and medication compliance are also important, especially in adolescents.

Donor and Recipient Size Matching in Heart Transplantation With Predicted Heart and Lean Body Mass

Donor and recipient size matching during heart transplant can be assessed using weight or predicted heart mass (PHM) ratios. We developed sex-specific allomteric equations for PHM and predicted lean body mass (PLBM) using the United Kingdom Biobank (UKB) and evaluated their predictive value in the United Network of Organ Sharing database. Donor and recipient size matching was based on weight, PHM and PLBM ratios. PHM was calculated using the Multiethnic Study of Atherosclerosis and UKB equations. PLBM was calculated using the UKB and National Health and Nutrition Examination Survey equations. Relative prognostic utility was compared using multivariable Cox analysis, adjusted for predictors of 1-year survival in the Scientific Registry of Transplant Recipients model. Of 53,648 adult patients in the United Network of Organ Sharing database between 1996 and 2016, 6528 (12.2%) died within the first year. In multivariable analysis, undersized matches by any metric were associated with increased 1-year mortality (all P < 0.01). Oversized matches were at increased risk using PHM or PLBM (all P < 0.01), but not weight ratio. There were significant differences in classification of size matching by weight or PHM in sex-mismatched donor-recipient pairs. A significant interaction was observed between pulmonary hypertension and donor undersizing (hazard ratio 1.15, P = 0.026) suggesting increased risk of undersizing in pulmonary hypertension. Donor and recipient size matching with simplified PHM and PLBM offered an advantage over total body weight and may be more important for sex-mismatched donor-recipient pairs. Donor undersizing is associated with worse outcomes in patients with pulmonary hypertension.

Clinical profiles and risk factors for early and medium-term mortality following heart transplantation in a pediatric population: A single-center experience

AIMS AND OBJECTIVES

There is a paucity of data regarding the outcomes of Heart transplantation in children from the Indian subcontinent. The data of patients under the age of 18 undergoing an isolated heart transplantation was analyzed for patient clinical profiles and risk factors for early and medium-term mortality. Hospital mortality was defined as death within 90 days of transplantation and medium-term survival as follow up of up to 6 years.

MATERIALS AND METHODS

A total of 97 patients operated between March 2014 and October 2019 were included in this study. Data was collected about their INTERMACS status, pulmonary vascular resistance, donor heart ischemic times, donor age, donor to recipient weight ratio and creatinine levels.

RESULTS

The age range was from 1 to 18 with a mean of 10.6 ± 4.6 years. 67 % patients were in INTERMACS category 3 or less.12 children were on mechanical circulatory support at the time of transplant. The 90 day survival was 89 %. The risk factors for hospital mortality was lower INTERMACS category (odd's ratio 0.2143, P = 0.026), elevated creatinine (odd's ratio 5.42, P = 0.076) and elevated right atrial pressure (odd's ratio 1.19, P = 0.015). Ischemic time, pulmonary vascular resistance (PVR) and PVR index (PVRI) had no effect on 90 day survival. Kaplan Meier estimates for 5 year survival was 73 %. The medium term survival was affected by INTERMACS category (Hazard ratio 0.7, P = .078), donor age > 25 (Hazard ratio 1.6, P = 0.26) and raised serum creatinine values.(Hazard ratio 2.7, P = 0.012). All the survivors are in good functional class.

CONCLUSIONS

Excellent outcomes are possible after heart transplantation in a pediatric population even in a resource constrained environment of a developing economy. More efforts are needed to promote pediatric organ donation and patients need to be referred in better INTERMACS category for optimal outcomes.

Anti-hypertensive treatment in the immediate post-operative period and 1 year after pediatric heart transplantation

Hypertension is a known complication of pediatric heart transplantation. We sought to identify factors associated with anti-hypertensive use in pediatric heart transplant recipients immediately post-transplant and oral anti-hypertensive use at discharge and 1-year post-transplant. Retrospective chart review was conducted of patients ≤18 years who underwent heart transplantation at two major heart transplant centers between August 1, 2009 and December 31, 2017 with ≥1-year follow-up. Exclusion criteria included re-transplant, multi-organ recipients, survival <1 year, and comorbidities associated with hypertension. Anti-hypertensive use was recorded during initial ICU stay, at discharge, and 1-year post-transplant. Univariate and multivariate analyses determined associations of demographic and diagnostic factors and need for anti-hypertensives. There were 188 patients that met inclusion criteria. Anti-hypertensive infusions were required in the ICU post-transplant in 46 patients (24.5%) for a median of 3 days (1-21 days). Oral anti-hypertensives were required in 58 patients (30.9%) at discharge and 1-year post-transplant. Anti-hypertensive infusion in the ICU post-transplant was associated with donor-to-recipient weight ratio. Oral anti-hypertensive use at discharge was associated with weight ratio and pretransplant VAD use, and at 1-year, post-transplant was associated with age at transplant, steroid use at discharge, and oral anti-hypertensive use at discharge. Hypertension is common immediately following and 1-year post-transplant. Weight ratio was the only independent predictor of anti-hypertensive use in the early post-transplant period, whereas VAD use was also associated with anti-hypertensive use at discharge. Anti-hypertensive use 1-year post-transplant was not associated with those factors, but rather with age at transplant and steroid use.

Review of the impact of donor characteristics on pediatric heart transplant outcomes

Heart transplantation (HTx) is a treatment option for end-stage heart failure in children. HTx is limited by the availability and acceptability of donor hearts. Refusal of donor hearts has been reported to be common with reasons for refusal including preexisting donor characteristics. This review will focus on the impact of donor characteristics and comorbidities on outcomes following pediatric HTx. A literature review was performed to identify articles on donor characteristics and comorbidities and pediatric HTx outcomes. There are many donor characteristics to consider when accepting a donor heart. Weight-based matching is the most common form of matching in pediatric HTx with a donor-recipient weight ratio between 0.7 and 3 having limited impact on outcomes. From an age perspective, donors <50 years can be carefully considered, but the impact of ischemic time needs to be understood. To increase the donor pool, with minimal impact on outcomes, ABO-incompatible donors should be considered in patients that are eligible. Other factors to be considered when accepting an organ is donor comorbidities. Little is known about donor comorbidities in pediatric HTx, with most of the data available focusing on infections. Being aware of the potential infections in the donor, understanding the testing available and risks of transmission, and treatment options for the recipient is essential. There are a number of donor characteristics that potentially impact outcomes following pediatric HTx, but these need to be taken into consideration along with their interactions with recipient factors when interpreting the outcomes following HTx.

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.

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.

Application of modified bicaval technique for pediatric heart transplant with oversized donor heart

Whereas bicaval technique is an effective surgical method, standard bicaval technique for younger age and donor/recipient caval mismatch was reported to have a risk of superior vena caval obstruction. Between 2016 and 2019, three patients with dilated cardiomyopathy aged 10 years or younger underwent orthotropic heart transplantation with modified bicaval technique at our institute. Donor/recipient body weight and height ratios were 2.36, 0.77, and 2.61 and 1.37, 0.94, and 1.51, respectively. All patients were preoperatively supported by a left ventricular assist device: Excor Pediatric in two patients and Jarvik 2000 in one. Duration of LVAD support was 180, 238, and 220 days. One patient required revision of pulmonary anastomosis during the operation; accordingly, the chest was closed 3 days later. There was no mortality. Caval obstructions were not observed. Three months after the operation, tricuspid regurgitation was mild in two patients and trivial in one.

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.

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.

Primary Transplantation for Congenital Heart Disease in the Neonatal Period: Long-term Outcomes

BACKGROUND

Primary transplantation was developed in the 1980s as an alternative therapy to palliative reconstruction of uncorrectable congenital heart disease. Although transplantation achieved more favorable results, its utilization has been limited by the availability of donor organs. This review examines the long-term outcomes of heart transplantation in neonates at our institution.

METHODS

The institutional pediatric heart transplant database was queried for all neonatal heart transplants performed between 1985 and 2017. Follow-up was obtained from medical records and an annually administered questionnaire. Overall survival and time to development of complications were estimated using the Kaplan Meier method. Univariate and multivariate analyses were performed to identify independent predictors of survival.

RESULTS

Heart transplantation was performed in 104 neonates. Median age was 17 days. Hypoplastic left heart syndrome (classic or variant) was the primary diagnosis in 77.8% of patients. Survival at 10 years and 25 years was 73.9% and 55.8%, respectively. At 20 years, freedom from allograft vasculopathy and lymphoproliferative disease was 72.0% and 81.9%, respectively. Freedom from re-transplantation was 81.4% at 20 years. Eight patients (7.6%) developed end-stage renal disease. By multivariate analysis, lower glomerular filtration rate and allograft vasculopathy were the only significant predictors of death.

CONCLUSIONS

Neonatal heart transplantation remains a durable therapy with very acceptable long-term survival. Children transplanted in the newborn period have the potential to reach adulthood with minimal need for reintervention.

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.

Pediatric heart transplantation: long-term outcomes

Pediatric heart transplant has become the standard of care for end-stage heart disease in children throughout the world. The number of transplants has grown dramatically since the first transplant was performed, and over the last two decades, outcomes have consistently improved with progression in knowledge enhancing the clinical course and outcomes of these patients. Short-term outcomes in the most recent era have been excellent resulting in a renewed focus towards medium- and long-term outcomes. This article will review the most up-to-date literature on overall heart transplantation outcomes and specific long-term outcomes including rejection, cardiac allograft vasculopathy, graft failure, infection, renal dysfunction, malignancy, and the need for re-transplantation. The article also explores the post-transplantation outcomes of special populations, including Fontan patients, ABO-incompatible recipients, sensitized recipients, extracorporeal membrane oxygenation, and ventricular assist devices. The article concludes with a look at transition from pediatric to adult care and medication adherence, which are becoming major issues related to long-term outcomes as post-transplant survival increases.

Alternative methods for virtual heart transplant-Size matching for pediatric heart transplantation with and without donor medical images available

BACKGROUND

Listed pediatric heart transplant patients have the highest solid-organ waitlist mortality rate. The donor-recipient body weight (DRBW) ratio is the clinical standard for allograft size matching but may unnecessarily limit a patient's donor pool. To overcome DRBW ratio limitations, two methods of performing virtual heart transplant fit assessments were developed that account for patient-specific nuances. Method 1 uses an allograft total cardiac volume (TCV) prediction model informed by patient data wherein a matched allograft 3-D reconstruction is selected from a virtual library for assessment. Method 2 uses donor images for a direct virtual transplant assessment.

METHODS

Assessments were performed in medical image reconstruction software. The allograft model was developed using allometric/isometric scaling assumptions and cross-validation.

RESULTS

The final predictive model included gender, height, and weight. The 25th-, 50th-, and 75th-percentiles for TCV percentage errors were -13% (over-prediction), -1%, and 8% (under-prediction), respectively. Two examples illustrating the potential of virtual assessments are presented.

CONCLUSION

Transplant centers can apply these methods to perform their virtual assessments using existing technology. These techniques have potential to improve organ allocation. With additional experience and refinement, virtual transplants may become standard of care for determining suitability of donor organ size for an identified recipient.

Survival Outcomes of Oversized Cardiac Allografts in Pediatric Patients-A Single-Center Experience in Taiwan

OBJECTIVES

An oversized cardiac allograft may have a negative impact on survival outcomes according to previous studies; however, due to the shortage of pediatric donor hearts, the use of oversized cardiac allografts is sometimes inevitable. In this study, we reported the survival outcomes of pediatric patients in relation with the donor-recipient weight ratio.

METHODS

Twenty-eight children, aged 3 months to 17 years, with dilated cardiomyopathy underwent primary cardiac transplantation at the National Taiwan University Hospital between 1995 and 2012. We analyzed these patients according to the donor-recipient weight ratio: group 1 (n = 19) with donor-recipient weight ratio <2.5 (median 1.1, interquartile range 1.0-1.6), and group 2 (n = 9) with donor-recipient weight ratio ≥2.5 (median 3.0, inter-quartile range 2.87-3.5).

RESULTS

The 30-day survival rate was 100% for both group 1 and group 2 (P = 1). The survival rates for group 1 and group 2 were 95% vs 100% at 1 year, 84% vs 89% at 5 years, and 73% vs 61% at 10 years. The median survival was 14.4 years vs 12.9 years (P = .6313).

CONCLUSION

In this cohort, the use of oversized cardiac allograft in pediatric patients for dilated cardiomyopathy did not have a negative effect on short-term and long-term survival.

Transient severe tricuspid regurgitation after transplantation of an extremely oversized donor heart in a child-Does size matter? A case report

In pediatric heart transplantation, the size of the donor organ is an important criterion for organ allocation. Oversized donor hearts are often accepted with good results, but some complications in relation to a high donor-recipient ratio have been described. Our patient was transplanted for progressive heart failure in dilated cardiomyopathy. The donor-to-recipient weight ratio was 3 (donor weight 65 kg, recipient weight 22 kg). The intra-operative echocardiography before chest closure showed excellent cardiac function, no tricuspid valve regurgitation, and a normal central venous pressure. After chest closure, central venous pressure increased substantially and echocardiography revealed a severe tricuspid insufficiency. As other reasons for right ventricular dysfunction, that is, myocardial ischemia, pulmonary hypertension, and rejection, were excluded, we assumed that the insufficiency was caused by an alteration of the right ventricular geometry. After 1 week, the valve insufficiency regressed to a minimal degree. In pediatric heart transplant patients with a high donor-to-recipient weight ratio, the outlined complication may occur. If other reasons for right ventricular heart failure can be ruled out, this entity is most likely caused by an acute and transient alteration of the right ventricular geometry that may disappear over time.

Interaction of older donor age and survival after weight-matched pediatric heart transplantation

BACKGROUND

Donors are matched for weight in pediatric heart transplantation (PHT), yet age differences are not considered in this decision. In this study we attempt to identify the effect of age differences in weight-matched patients and the effect these differences have on post-transplant survival.

METHODS

The United Network of Organ Sharing (UNOS) database was queried for the period from October 1987 to March 2014 for all pediatric heart transplant patients. Transplants with donor-to-recipient (D-R) weight ratios of 0.8 to 1.5 were identified (weight-matched). D-R age differences were categorized as: donors 5 years younger than recipients (D<R-5); donors within 5 years of recipients (D=R±5); and donors 5 years older than recipients (D>R+5).

RESULTS

A total of 4,408 patients were identified as weight-matched transplants. Of these transplants, 681 were D>R+5, 3,596 were D=R±5 and 131 were D<R-5. D>R+5 transplants were found to be associated with decreased post-transplant survival compared with D=R±5 (p = 0.002). Rates of acute rejection were similar among all groups but post-transplant coronary allograft vasculopathy (CAV) was more prevalent in D>R+5 than D=R±5 patients (28% and 18%, respectively; p < 0.001). Increasing age difference by each year was associated with decreasing median post-transplant survival time (p < 0.001; hazard ratio 1.018, range 1.011 to 1.025). The overall negative association with mortality was due to the adolescent cohort (11 to 17 years), specifically D>R+5 transplants, utilizing organs from donors >25 of age.

CONCLUSION

In PHT, increasing D-R age difference decreases survival; however, this effect is driven by recipients 11 to 17 years old and donors >25 years old. Allocation of younger donor organs to adolescent recipients should be a priority.

Donor-recipient height ratio and outcomes in pediatric heart transplantation

Height matching in pediatric HTx has been proposed as a superior method of evaluating graft size, but no studies have examined survival advantage for height-matched donor-recipient pairs. We hypothesized that in pediatric patients with DCM, an oversized donor improves survival and aimed to define the optimal height ratio in this patient group. Pediatric primary HTx recipients with DCM between 10/89 and 09/12 were identified in the OPTN database. Patients were stratified into three donor-recipient height and weight ratio categories. One- and five-yr survival was compared using Kaplan-Meier analysis and HRs were computed. A total of 2133 children with DCM who underwent HTx during the study period were included. Unadjusted one-yr survival was worse for DRHR <0.87 (HR, 2.15 [95% CL, 1.30, 3.53]; p < 0.01). This difference was not present at five yr post-HTx or when stratified by weight. After adjustment for other risk factors affecting transplant survival, height matching was no longer significant. Although height matching appears to predict short-term survival better than weight in pediatric HTx recipients with DCM, other factors play a more important role as height matching loses significance in multivariate analysis.

Improved survival after heart transplant for failed Fontan patients with preserved ventricular function

BACKGROUND

Patients with a failing Fontan continue to have decreased survival after heart transplant (HT), particularly those with preserved ventricular function (PVF) compared with impaired ventricular function (IVF). In this study we evaluated the effect of institutional changes on post-HT outcomes.

METHODS

Data were retrospectively collected for all Fontan patients who underwent HT. Mode of failure was defined by the last echocardiogram before HT, with mild or no dysfunction considered PVF and moderate or severe considered IVF. Outcomes were compared between early era (EE, 1995 to 2008) and current era (CE, 2009 to 2014). Management changes in the CE included volume load reduction with aortopulmonary collateral (APC) embolization, advanced cardiothoracic imaging, higher goal donor/recipient weight ratio and aggressive monitoring for post-HT vasoplegia.

RESULTS

A total of 47 patients were included: 27 in the EE (13 PVF, 14 IVF) and 20 in the CE (12 PVF, 8 IVF). Groups were similar pre-HT, except for more PLE in PVF patients. More patients underwent APC embolization in the CE (80% vs 28%, p < 0.01). There was no difference in donor/recipient weight ratio between eras. There was a trend toward higher primary graft failure for PVF in the EE (77% vs 36%, p = 0.05) but not the CE (42% vs 75%, p = 0.20). Overall, 1-year survival improved in the CE (90%) from the EE (63%) (p = 0.05), mainly due to increased survival for PVF (82 vs 38%, p = 0.04).

CONCLUSIONS

Post-HT survival for failing Fontan patients has improved, particularly for PVF. In the CE, our Fontan patients had a 1-year post-HT survival similar to other indications.

Predictors and Outcome of Extracorporeal Life Support After Pediatric Heart Transplantation

BACKGROUND

Extracorporeal life support (ECLS) has proven success after conventional cardiac surgery. Its use after pediatric heart transplantation is less well documented. We reviewed ECLS after pediatric heart transplantation, to understand better predisposing factors, morbidity, and mortality.

METHODS

The notes of all patients at Great Ormond Street Hospital undergoing orthotopic heart transplantation from 1999 to 2009 were reviewed (202 transplants; patients aged 0.06 to 17.91 years). Patients were grouped by diagnosis: restrictive cardiomyopathy (n = 17), nonrestrictive cardiomyopathy (n = 134), and anatomic heart disease (n = 51).

RESULTS

Twenty-eight patients (13.9%) required ECLS after transplantation. Those requiring ECLS had longer ischemic times (4.2 versus 3.7 hours, p = 0.02). More restrictive cardiomyopathy patients (35.3%) required ECLS-higher than dilated cardiomyopathy (10.4%) or anatomic heart disease (15.7%; χ(2) 7.99; p = 0.018). Factors associated with posttransplant ECLS were restrictive cardiomyopathy, longer ischemic time, and extracorporeal membrane oxygenation before transplant. Graft survival was higher in the non-ECLS group, with 1-year survival of 98.2% versus 57.7%; however, medium-term survival was comparable, with 5-year survival for those surviving to hospital discharge being 84.7% versus 100%.

CONCLUSIONS

The requirement for ECLS was higher than expected for conventional cardiac surgery. Although just over one half of patients requiring ECLS survived to discharge, they had excellent medium-term survival, with all still alive. Although ECLS is an expensive, invasive therapy, with significant morbidity and mortality, without it, those patients would have perished. Its judicious use, therefore, can be recommended.

An echocardiographic measurement of superior vena cava to inferior vena cava distance in patients<20 years of age with idiopathic dilated cardiomyopathy

In normal pediatric echocardiograms, the distance from the junction of superior vena cava (SVC) and right atrium to inferior vena cava (IVC) and right atrium is linearly related to height. We examine this relation in children listed for heart transplant with idiopathic dilated cardiomyopathy (IDC) compared with the previously defined normal distribution of SVC-IVC to improve matching of heart sizes. Measurements of SVC-IVC and left ventricular end-diastolic diameter in 55 pediatric patients with IDC were correlated with height, weight, and body surface area. Regression analyses were performed to find the best-fit equation and correlation coefficient. Generalized linear modeling compared SVC-IVC in patients with IDC with normal SVC-IVC values from 254 patients. There was a strong linear relation in patients with IDC between SVC-IVC and height (R2=0.84) and a logarithmic relation to weight (R2=0.80). Left ventricular end-diastolic diameter did not correlate with SVC-IVC or any other parameter. In 87% of patients with IDC, SVC-IVC was over 2 SDs above predicted normal values (mean z-score=4.3±2.1). In conclusion, predicted SVC-IVC in patients with IDC was different from published norms (p<0.001). SVC-IVC in pediatric patients with IDC, although linearly related to height, is consistently above normal values.

Donors' characteristics and impact on outcomes in pediatric heart transplant recipients

Organ availability and acceptability limit pediatric HTx. What characteristics define an unacceptable or high-risk pediatric donor remains unclear. The purpose of this study was to characterize a large cohort of pediatric donors and determine the donor risk factors, including cumulative risk, that affect recipient survival. Data from the PHTS, a prospective multicenter study, were used to examine the impact of donor factors on the outcomes of patients listed <18 yr of age who received a HTx between 1993 and 2009. Donor data were available for 3149 of 3156 HTx (99.8%). Donor cause of death, need for inotropes, or CPR did not affect survival outcomes (p = 0.05). Ischemic time also did not have an impact on overall recipient survival; however, longer ischemic times negatively impacted one-yr post-transplant survival (p < 0.0001). There was no impact of cumulative risk factors on survival (p = 0.8). Although used in a minority of cases, hormonal therapy in the donor positively impacted survival (p = 0.03). In multivariate analysis, the only donor factor associated with decreased survival was smaller donor BSA, the other factors being related to the recipient characteristics. When analyzed by recipient age, there were no donor-related factors that affected survival for those who received a transplant at <6 months of age. Longer ischemic time (p < 0.0001) and greater age difference between the recipient and donor (p = 0.0098) were donor-related factors impacting early-phase survival for recipients who received a graft at ≥10 yr of age. Factors perceived to define a marginal or high-risk pediatric heart donor including inotrope use, CPR and donor cause of death may have less impact on outcomes than previously thought. Longer ischemic times did impact one yr, but not overall survival, and this impact was much greater with older donors. Parameters for accepting a donor heart can potentially be expanded, especially in the infant age group, but strong consideration should always be given to the interaction between ischemic time and donor age.

Pediatric heart transplantation for congenital and restrictive cardiomyopathy

BACKGROUND

Recent reports suggest worse outcomes in pediatric orthotopic heart transplantation (OHT) for congenital heart disease (CHD) and restrictive cardiomyopathy (RCM). We examined early outcomes in these diverse groups of patients in comparison with patients with dilatated cardiomyopathy (DCM).

METHODS

From 2000 to 2011, 209 patients were included: 50 with CHD, 23 with RCM, and 136 with DCM. Early survival was studied, as was the occurrence of acute rejection, donor-specific antibodies (DSAs) and nondonor-specific antibodies (NSDAs), incidence of pulmonary hypertension (PHT), right ventricular failure (RVF), and the need for mechanical circulatory support (MCS).

RESULTS

The incidence of preoperative PHT was greatest in the RCM group (χ(2)p = 0.0006); the requirement for mechanical support before OHT was greatest in patients with DCM. Thirty-day survival was 92.0%, 97.1%, and 100% for patients with CHD, DCM, and RCM respectively. The incidence of RVF was highest for patients with RCM (43.5%; versus CHD, 26.0%; versus DCM, 14.7%). One-year survival estimates for patients with CHD, DCM, and RCM were 92.0%, 97.8%, and 82.6%, respectively (log-rank p = 0.165). Multivariable analysis revealed 4 significant risk factors for mortality: age, incidence of acute rejection, preoperative PHT, and the presence of NDSAs. The occurrence of DSAs was similar, although there was a significantly higher incidence of NDSAs in the CHD and RCM groups (36.0% and 30.4%, respectively, versus 14.0% in the DCM group; χ(2)p = 0.0024).

CONCLUSIONS

Equivalent outcomes are achievable in pediatric OHT despite marked heterogeneity in anatomic and physiologic complexity in recipients. Physiologic factors such as PHT are likely to be more important than anatomic complexities in determining survival. The potential relevance of NDSAs warrants further investigation.