Donor considerations in pediatric heart transplantation

Donor Characteristics and Outcomes of Pediatric Heart Transplantation in South Korea

BACKGROUND

Heart transplantation is often limited by the availability of transplantable donor heart and understanding of donor aspects that would influence transplant outcomes becomes important. In this study, donor characteristics and their impact on the outcomes of pediatric heart transplantations performed in South Korea were investigated.

METHODS

We reviewed the medical records of patients less than 18 years old who received heart transplantation between 2002 and 2022 in three tertiary hospitals located in South Korea.

RESULTS

A total of 139 cases were enrolled. One-year mortality was 10.4% and total mortality was 33.8%. Forty-nine recipients (35.3%) showed biopsy-proven rejections and 20 (14.4%) showed cardiac allograft vasculopathy during mean follow-up of 6.4 ± 4.9 years. Six recipients (4.5%) showed left ventricle ejection fraction of less than 55% post-transplantation. The mean age of the donors was 23.0 ± 15.4 years. The most common cause of death of the donors was unspecified illness (46.4%). Donors with a history of diabetes, hypertension, smoking, and alcohol consumption were 0%, 3.1%, 32.1%, and 34.4%, respectively. Mean total ischemic time was 191.6 ± 72.7 min, while total ischemic time was over 4 h in 37 patients (26.6%). There were no significant relationship between donor factors and survival. However, donor's history of drinking or cardiopulmonary resuscitation was significantly associated with acute rejection and donor's age with cardiac allograft vasculopathy.

CONCLUSION

Donor factors did not show significant impact on post-transplant survival but some factors were predictive of post-transplant rejection and cardiac allograft vasculopathy.

Influence of donor age and donor-recipient age difference on intimal hyperplasia in pediatric patients with young and adult donors vs. adult patients after heart transplantation

AIM

Optimal selection and allocation of donor hearts is a relevant aspect in transplantation medicine. Donor age and cardiac allograft vasculopathy (CAV) affect post-transplant mortality. To what extent donor age impacts intimal hyperplasia (CAVIH) in pediatric and adult patients after heart transplantation (HTx) is understudied.

METHODS

In a cohort of 98 HTx patients, 58 pediatric (24.1% with adult donors) and 40 adult patients, we assessed the effect of donor age and donor-recipient age difference (D-R) on the continuous parameter of maximal intima thickness (mIT) in optical coherence tomography. We evaluated their predictive value regarding higher mIT and the prevalence of CAVIH, defined as mIT > 0.3 mm, and compared it to established CAV risk factors.

RESULTS

In the overall population, donor age correlated with mIT (p < 0.001), while in the pediatric subpopulation, both donor age and D-R correlated with mIT (p < 0.001 and p = 0.002, respectively). In the overall population, donor age was a main predictor of higher mIT and CAVIH (p = 0.001 and p = 0.01, respectively) in addition to post-transplant interval, arterial hypertension, and dyslipidemia. In the pediatric patients, dyslipidemia remained a main predictor of both higher mIT and CAVIH (p = 0.004 and p = 0.040, respectively), while donor age and D-R were not.

CONCLUSION

While there was an effect of the non-modifiable parameter of donor age regarding maximal intimal thickness, a stronger association was seen between the modifiable risk factor dyslipidemia and higher maximal intimal thickness and CAVIH in both the overall population and the pediatric subpopulation.

Preclinical Proof-of-Concept of a Minimally Invasive Direct Cardiac Compression Device for Pediatric Heart Support

PURPOSE

For pediatric patients, extracorporeal membrane oxygenation (ECMO) remains the predominant mechanical circulatory support (MCS) modality for heart failure (HF) although survival to discharge rates remain between 50 and 60% for these patients. The device-blood interface and disruption of physiologic hemodynamics are significant contributors to poor outcomes.

METHODS

In this study, we evaluate the preclinical feasibility of a minimally invasive, non-blood-contacting pediatric DCC prototype for temporary MCS. Proof-of-concept is demonstrated in vivo in an animal model of HF. Hemodynamic pressures and flows were examined.

RESULTS

Minimally invasive deployment on the beating heart was successful without cardiopulmonary bypass or anticoagulation. During HF, device operation resulted in an immediate 43% increase in cardiac output while maintaining pulsatile hemodynamics. Compared to the pre-HF baseline, the device recovered up to 95% of ventricular stroke volume. At the conclusion of the study, the device was easily removed from the beating heart.

CONCLUSIONS

This preclinical proof-of-concept study demonstrated the feasibility of a DCC device on a pediatric scale that is minimally invasive and non-blood contacting, with promising hemodynamic support and durability for the initial intended duration of use. The ability of DCC to maintain pulsatile MCS without blood contact represents an opportunity to mitigate the mortality and morbidity observed in non-pulsatile, blood-contacting MCS.

Reducing donor acceptance practice variation - Learnings from a discussion forum

PURPOSE

Although waitlist mortality is unacceptably high, nearly half of donor heart offers are rejected by pediatric heart transplant centers. The Advanced Cardiac Therapy Improving Outcome Network (ACTION) and Pediatric Heart Transplant Society (PHTS) convened a multi-institutional donor decision discussion forum (DDDF) aimed at assessing donor acceptance practices and reducing practice variation.

METHODS

A 1-h-long virtual DDDF for providers across North America, the United Kingdom, and Brazil was held monthly. Each session typically included two case presentations posing a real-world donor decision challenge. Attendees were polled before the presenting center's decision was revealed. Group discussion followed, including a review of relevant literature and PHTS data. Metrics of participation, participant agreement with presenting center decisions, and impact on future decision-making were collected and analyzed.

RESULTS

Over 2 years, 41 cases were discussed. Approximately 50 clinicians attended each call. Risk factors influencing decision-making included donor quality (10), size discrepancy (8), and COVID-19 (8). Donor characteristics influenced 63% of decisions, recipient factors 35%. Participants agreed with the decision made by the presenting center only 49% of the time. Post-presentation discussion resulted in 25% of participants changing their original decision. Survey conducted reported that 50% respondents changed their donor acceptance practices.

CONCLUSION

DDDF identified significant variation in pediatric donor decision-making among centers. DDDF may be an effective format to reduce practice variation, provide education to decision-makers, and ultimately increase donor utilization.

Pediatric donor heart acceptance practices in the United States: What is really being considered?

BACKGROUND

Recent studies demonstrate high offer decline and organ non-utilization rates are associated with increased pediatric heart transplant waitlist mortality. We sought to determine which donor, candidate, and offer specific variables most importantly influenced these decisions using only data available at the time of each offer.

METHODS

Retrospective review of pediatric (<18 years) heart donor offers made to pediatric candidates in the United States between 2010 and 2020. In addition to standard donor, candidate, and offer data available in UNOS, we extracted objective and qualitative valvar and myocardial function data from all available donor echocardiogram reports.

RESULTS

During the study period, 5625 pediatric donor hearts produced 30 156 offers to 4905 unique candidates, of which 88.7% of all offers were declined and 39.2% of organs were not utilized by pediatric waitlisted candidates. Of the 60.8% utilized hearts, 89.7% had a 'cumulatively' normal echocardiogram at the time of offer acceptance; 62.9% of hearts not utilized for a pediatric candidate also had a cumulatively normal final echocardiogram. Random forest and logistic regression modeling demonstrated good predictive performance (AUROC ≥0.83) of likelihood to accept when utilizing donor, candidate, and offer specific variables. SHAP variable importance scores demonstrated number of prior offer declines and candidate institution's prior year acceptance rates as the two most important variables influencing offer decisions.

CONCLUSIONS

Behavioral economics appear to play a significant role in pediatric heart transplant candidate institutions' acceptance practices, even when considering the arguably healthier pediatric donor population. Removal of prior institution's decisions from DonorNet may help increase donor utilization.

Effect of ischemic time on pediatric heart transplantation outcomes: is it the same for all allografts?

BACKGROUND

Studies have shown that the optimal ischemia time (IT) threshold in pediatric heart transplantation (PHT) is up to 4 h, independent of other donor organ factors. The purpose of this study was to examine the relationship between IT and donor left ventricular ejection fraction (LVEF) and study their impact on PHT outcomes.

METHODS

This is a retrospective cohort study of PHT (<18 years) identified in UNOS between January 2000 and March 2020. Post-transplantation survival analysis of patients receiving donor hearts with IT<4, 4-6, and >6 h was performed using Kaplan-Meier curves. Cohort was divided according to donor LVEF median value, and survival was analyzed. Cox regression was performed.

RESULTS

Median LVEF was 65% in the study cohort (6669 PHT). Overall, IT>6 h was associated with worse survival compared to <4 h regardless of donor LVEF. For allografts with LVEF < 65%, IT = 4-6 h was associated with worse survival compared with IT < 4 h (p = .006) but had similar survival compared with IT > 6 h (p = .315). For allografts with LVEF ≥ 65%, IT = 4-6 h had similar survival compared with <4 h (p = .175) but improved survival compared with >6 h (p = .003). After adjusting for donor and recipient variables, Cox regression showed that IT = 4-6 h was not associated with increased mortality for LVEF ≥ 65%.

CONCLUSIONS

The IT threshold of 4 h does not apply to all allografts. Recipients of hearts with LVEF≥65% can tolerate an IT up to 6 h without any detriment to survival. Routine acceptance of these donor hearts could mitigate longer waiting times and poor donor availability for many candidates.

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.