Incidence, predictors, and outcomes after severe primary graft dysfunction in pediatric heart transplant recipients

Mechanical circulatory support early after pediatric heart transplantation-an analysis from the Pediatric Heart Transplant Society

BACKGROUND

The use of early mechanical circulatory support (MCS) following pediatric heart transplantation is not well-published. This paper attempts to uncover the incidence, predisposing factors, and outcomes of MCS in a large, international cohort.

METHODS

The Pediatric Heart Transplant Society Database (an international, prospective, event-driven database) was retrospectively analyzed for all cases of primary heart transplant over an 11-year period (2010-2020), dividing the cohort based on need for MCS within 30 days of transplantation.

RESULTS

Of 4,321 primary transplants, 249 (5.8%) required MCS (230 ECMO (Extracoporeal Membranous Oxygenation), 19 ventricular assist device). In a Cox proportional hazard model, congenital heart disease (p = 0.0002), older donor age (p < 0.0001), and longer ischemic time (p = 0.018) were each related to an increased need for MCS; increasing recipient body surface area (p < 0.0001) and increasing donor left ventricular ejection fraction (p = 0.016) were both correlated with less MCS use. One-year survival in those requiring MCS was 54.2%, compared with 94.8% in those who did not need MCS (p < 0.0001). Later survival in patients surviving to 1 year was similar between the groups.

CONCLUSIONS

MCS is used infrequently following pediatric heart transplant and is related to donor, recipient, and transplant factors. Although mortality is high, those surviving the first year post transplant have excellent outcomes. Judicious use in those patients who would otherwise perish is therefore justified.

Impact of prolonged ischemic time on pediatric heart transplantation outcomes: Improved outcomes in the most recent era

BACKGROUND

Impacts of ischemic time (IT) on pediatric heart transplant outcomes are multifactorial. We aimed to analyze the effect of prolonged IT on graft loss after pediatric heart transplantation. We hypothesized that graft survival with prolonged IT has improved across eras.

METHODS

Patients <18 years old in the Pediatric Heart Transplant Society database were included (N=6,765) and stratified by diagnosis and era (1993-2004, 2005-2009, and 2010-2019). Severe graft failure (SGF) was defined as death, retransplant, or need for mechanical circulatory support in the first 7 days post-transplant. Descriptive statistical methods were used to compare differences between patient characteristics and IT. Kaplan-Meier survival analysis compared freedom from graft loss, rejection, and infection. Multivariable analysis was performed for graft loss and SGF (hazard and logistic regression modeling, respectively).

RESULTS

Diagnoses were cardiomyopathy (N = 3,246) and congenital heart disease (CHD; N = 3,305). CHD were younger, more likely to have an IT ≥4.5 hours, and more likely to require extracorporeal membrane oxygenation or mechanical ventilation at transplant (all p < 0.001). Median IT was 3.6 hours (interquartile range 2.98-4.31; range 0-10.5). IT was associated with early graft loss (HR 1.012, 95% CI 1.005-1.019), but not when analyzed only in the most recent era. IT was associated with SGF (OR 1.016 95%CI 1.003-1.030).

CONCLUSIONS

Donor IT was independently associated with an increased risk of graft loss, albeit with a small effect relative to other risk factors. Graft survival with prolonged IT has improved in the most recent era but the risk of SGF persists.

Research Gaps in Pediatric Heart Failure: Defining the Gaps and Then Closing Them Over the Next Decade

Given the numerous opportunities and the wide knowledge gaps in pediatric heart failure, an international group of pediatric heart failure experts with diverse backgrounds were invited and tasked with identifying research gaps in each pediatric heart failure domain that scientists and funding agencies need to focus on over the next decade.

Primary isolated right ventricular failure after heart transplantation: prevalence, right ventricular characteristics, and outcomes

To determine the prevalence, right ventricular (RV) characteristics, and outcomes of primary isolated RV failure (PI-RVF) after heart transplant (HTX). PI-RVF was defined as (1) the need for mechanical circulatory support post-transplant, or (2) evidence of RVF post-transplant as measured by right atrial pressure (RAP) > 15 mmHg, cardiac index of < 2.0 L/min/m² or inotrope support for < 72 h, pulmonary capillary wedge pressure < 18 mmHg, and transpulmonary gradient < 15 mmHg with pulmonary systolic pressure < 50 mmHg. PI-RVF can be diagnosed from the first 24-72 h after completion of heart transplantation. A total of 122 consecutive patients who underwent HTX were reviewed. Of these, 11 were excluded because of secondary causes of graft dysfunction (GD). PI-RVF was present in 65 of 111 patients (59%) and 31 (48%) met the criteria for PGD-RV. Severity of patients with PI-RVF included 41(37%) mild, 14 (13%) moderate, and 10 (9%) severe. The median onset of PI-RVF was 14 (0-49) h and RV recovery occurred 5 (3-14) days after HTX. Severe RV failure was a predictor of 30-day mortality (HR 13.2, 95% CI 1.6-124.5%, p < 0.001) and post-transplant dialysis (HR 6.9, 95% CI 2.0-257.4%, p = 0.001). Patients with moderate PI-RVF had a higher rate of 30-day mortality (14% vs. 0%, p = 0.014) and post-operative dialysis (21% vs. 2%, p = 0.016) than those with mild PI-RVF. Among patients with mild and moderate PI-RVF, patients who did not meet the criteria of PGD-RV had worsening BUN/creatinine than those who met the PGD-RV criteria (p < 0.05 for all). PI-RVF was common and can occur after 24 h post-HTX. The median RV recovery time was 5 (2-14) days after HTX. Severe PI-RVF was associated with increased rates of 30-day mortality and post-operative dialysis. Moderate PI-RVF was also associated with post-operative dialysis. A revised definition of PGD-RV may be needed since patients who had adverse outcomes did not meet the criteria of PGD-RV.

Clinical approach to mechanical circulatory support in the transplant patient from the Pediatric Heart Transplant Society

The use of mechanical circulatory support (MCS) for pediatric patients who have undergone heart transplant has grown rapidly in the past decade. This includes support in the immediate post-transplant period and "rescue" therapy for patient later in their transplant course. Extracorporeal membrane oxygenation (ECMO) remains a standard modality of support for intraoperative concerns and for acute decompensation in the immediate post-transplant period. However, both pulsatile and continuous flow ventricular assist devices (VADs) have been used with increasing success in transplant patients for longer durations of support. Centers participating in the Pediatric Heart Transplant Society (PHTS) were queried to provide their internal protocols and rationale for mechanical circulatory support following heart transplant. These protocols coupled with evidence-based literature were used to provide the following description of clinical approaches to MCS in the transplant patient highlighting areas of both broad consensus and significant practice variation.

Ventricular assist device support following pediatric heart transplantation

BACKGROUND

VAD support for early graft failure after HTx is a rare event in pediatrics.

METHODS

We retrospectively describe our single-center experience with post-HTx VAD support in a cohort of patients transplanted between 01/05 and 12/20.

RESULTS

Nine patients underwent VAD insertion in the early post-HTx period [median age 6.1 years (Range 0.3-20.3), median weight 17.6 kg (Range 3.5-65.0), and congenital heart disease (67%)]. Of the nine patients with early graft failure, almost half (44%) were implanted after 2015 and all of these patients had a pre-HTx plan for possible post-transplant VAD insertion. Time to VAD implant was a median of 0 day (Range 0-11). Total time on VAD support was a median of 12 days (Range 3.0-478.0). Two-thirds (n = 6; 67%) of the patients were weaned from support, retransplanted (11%) and two patients died (22%). In all of the patients where post-HTx VAD was anticipated there was 100% survival.

CONCLUSIONS

In this small patient series, post-HTx VAD was a useful measure in selected patients especially with pre-HTx planning. However, more shared experiences to verify these findings are needed.

Pediatric heart transplantation in infants and small children under 3 years of age: Single center experience - "Early and long-term results"

OBJECTIVES

We analyzed the early and long-term survival after ABO-compatible heart transplantation in children under 3 years of age from 1991 to 2021 at our center. This retrospective and descriptive study aimed to identify serious adverse events associated with mortality after pediatric heart transplantation.

PATIENTS AND METHODS

46 patients with congenital heart failure (37%) in end-stage heart failure have undergone a pediatric heart transplantation. Primary outcome of interest was survival at follow-up time.

RESULTS

Median (IQR) follow-up time (y), age (y), body-weight (kg) and BMI (kg/cm²) were 13.2 (5.7-19.5), 0.9 (0.2-2.0), 6.8 (4.3-10.0) and 14.2 (12.3-15.7). Twenty-four (52%) patients were male. 15 patients (33%) had a single ventricle physiology. At 30- days survival rate was 94 ± 4%. Survival rate at 1, 5, 10 and 15 years post HTx was 87 ± 5%, 84 ± 6%, 79 ± 6% and 63 ± 8%. One child underwent re-transplantation after 4 years, and another one after 11 years - in both cases due to graft failure. Higher early mortality in patients under 3 months of age and in patients with single ventricle physiology. Transplant free survival at 15 years was in children with cardiomyopathy better (71 ± 10%) than in those with congenital heart disease (50 ± 13%). One or more previous heart surgeries prior to HTx (n = 21) were associated to more mortality.

CONCLUSION

Pediatric heart transplantation has acceptable long-term results and is still the best therapeutic option in children with end-stage cardiac failure. Underlying anomalies and single ventricle physiology, age below 3 months had a significant impact on survival.

Matching Donor and Recipient Size in Pediatric Heart Transplantation

Previous analyses in pediatric heart transplant (HT) recipients using weight or height have not found donor-recipient size-mismatch to be associated with post-transplant mortality. A recent study in 3,215 normal US children developed an equation for left ventricular (LV) mass using body surface area (BSA). We assessed whether donor-recipient size match using predicted LV mass (PLM) is associated with post-transplant in-hospital mortality or 1-year graft survival. We identified 4,717 children <18 yrs old who received primary HT in the US during 01/2000 to 03/2015 and divided them into five groups [10%, 10%, 60% (reference group), 10% and 10%, respectively] with increasing donor-recipient PLM ratio. In adjusted analysis, group 1 children (PLM ratio ≤.90) were at higher risk of post-transplant in-hospital mortality [Odds Ratio (OR) 1.55, 95% CI 1.04, 2.31]. This association of the most undersized donors with recipient in-hospital mortality was similar when donor-recipient weight ratio<.88 or BSA ratio<.92 (lowest decile) were used instead. There was no difference in 1-year graft survival among groups. Utilizing donors with donor-recipient PLM ratio ≤.90 is associated with higher risk of early post-transplant mortality in pediatric HT recipients. However, this metric is not superior to donor-recipient weight ratio or BSA ratio for assessing size match.

Plasma kallikrein predicts primary graft dysfunction after heart transplant

BACKGROUND

Primary graft dysfunction (PGD) is the leading cause of early mortality after heart transplant. Pre-transplant predictors of PGD remain elusive and its etiology remains unclear.

METHODS

Microvesicles were isolated from 88 pre-transplant serum samples and underwent proteomic evaluation using TMT mass spectrometry. Monte Carlo cross validation (MCCV) was used to predict the occurrence of severe PGD after transplant using recipient pre-transplant clinical characteristics and serum microvesicle proteomic data. Putative biological functions and pathways were assessed using gene set enrichment analysis (GSEA) within the MCCV prediction methodology.

RESULTS

Using our MCCV prediction methodology, decreased levels of plasma kallikrein (KLKB1), a critical regulator of the kinin-kallikrein system, was the most predictive factor identified for PGD (AUROC 0.6444 [0.6293, 0.6655]; odds 0.1959 [0.0592, 0.3663]. Furthermore, a predictive panel combining KLKB1 with inotrope therapy achieved peak performance (AUROC 0.7181 [0.7020, 0.7372]) across and within (AUROCs of 0.66-0.78) each cohort. A classifier utilizing KLKB1 and inotrope therapy outperforms existing composite scores by more than 50 percent. The diagnostic utility of the classifier was validated on 65 consecutive transplant patients, resulting in an AUROC of 0.71 and a negative predictive value of 0.92-0.96. Differential expression analysis revealed a enrichment in inflammatory and immune pathways prior to PGD.

CONCLUSIONS

Pre-transplant level of KLKB1 is a robust predictor of post-transplant PGD. The combination with pre-transplant inotrope therapy enhances the prediction of PGD compared to pre-transplant KLKB1 levels alone and the resulting classifier equation validates within a prospective validation cohort. Inflammation and immune pathway enrichment characterize the pre-transplant proteomic signature predictive of PGD.

Risk Factors for Severe Primary Graft Dysfunction in Infants Following Heart Transplant

Background

Previous studies suggest that infant heart transplant (HT) recipients are at higher risk of developing severe primary graft dysfunction (PGD) than older children. We sought to identify risk factors for developing severe PGD in infant HT recipients.

Methods and Results

We identified all HT recipients aged <1 year in the United States during 1996 to 2015 using the Organ Procurement and Transplant Network database. We linked their data to ELSO (Extracorporeal Life Support Organization) registry data to identify those with severe PGD, defined by initiation of extracorporeal membrane oxygenation support for PGD within 2 days following HT. We used multivariable logistic regression to assess risk factors for developing severe PGD. Of 1718 infants analyzed, 600 (35%) were <90 days old and 1079 (63%) had congenital heart disease. Overall, 134 (7.8%) developed severe PGD; 95 (71%) were initiated on extracorporeal membrane oxygenation support on the day of HT, 34 (25%) the next day, and 5 (4%) the following day. In adjusted analysis, recipient congenital heart disease, extracorporeal membrane oxygenation, or biventricular assist device support at transplant, recipient blood type AB, donor‐recipient weight ratio <0.9, and graft ischemic time ≥4 hours were independently associated with developing severe PGD whereas left ventricular assist device support at HT was not. One‐year graft survival was 48% in infants with severe PGD versus 87% without severe PGD.

Conclusions

Infant HT recipients with severe PGD have poor graft survival. Although some recipient‐level risk factors are nonmodifiable, avoiding modifiable risk factors may mitigate further risk in infants at high risk of developing severe PGD.

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.

Postoperative vasoactive inotropic score is predictive of outcomes in pediatric heart transplantation

Vasoactive inotrope score (VIS) is scarcely studied in pediatric orthotopic heart transplantation (pOHT). We conducted a retrospective review of pOHT (<21 years) recipients. Max VIS and mean VIS were calculated at 0-24 and 24-48 hours post-pOHT. Patients were divided into groups based on ISHLT guidelines: high (>10) and low (≤10). In our group (n = 104), patients with high max and mean VIS groups at 0-24 and 24-48 hours had longer bypass times (high: >130 minutes; low: <108 minutes; P < .05) and high max and mean VIS groups at 0-24 hours had longer ischemic times (high: >215 minutes; low: <192 minutes; P < .05). Patients with high max and mean VIS at 0-24 and 24-48 hours had longer hospital stay, ventilation, inotrope duration, more cardiac events, and acute kidney injury postoperatively (P < .05). High max VIS at 24-48 hours and high mean VIS at 24-48 hours had higher 3-year mortality (P = .04; P = .02). Multivariate analysis confirmed the association of VIS with short-term outcomes. However, VIS was not identified as an independent predictor of mortality. The ROC curve exhibits 10 as the ideal cutoff with area under the curve >0.8 for primary graft dysfunction (PGD).

Extracorporeal Membrane Oxygenation Support After Heart Transplantation in Children-Outcomes of a Single Center Cohort

OBJECTIVES

Extracorporeal membrane oxygenation is used for postcardiotomy low cardiac output but is less established following heart transplantation. We characterized outcomes for children supported with extracorporeal membrane oxygenation after heart transplantation.

DESIGN

Single-center retrospective study.

SETTING

Large pediatric cardiac referral center.

PATIENTS

All patients who received heart transplantation and were cannulated to extracorporeal membrane oxygenation between 1995 and 2016.

INTERVENTIONS

Primary outcome measure was mortality 12 months postextracorporeal membrane oxygenation. Patient characteristics were analyzed for association with outcome according to early graft failure (extracorporeal membrane oxygenation ≤ 7 d after heart transplantation), or late graft failure.

MEASUREMENTS AND MAIN RESULTS

There were 246 heart transplants during the study period and 50 extracorporeal membrane oxygenation runs in 44 patients. Median time from transplant to extracorporeal membrane oxygenation was 1 day (range, 0-11.7 yr), with early graft failure in 28 patients (median 1, range 0-2 d) and 22 extracorporeal membrane oxygenation runs in 20 late graft failure patients (median, 0.8 yr; range, 8 d to 11.7 yr), including four patients with prior extracorporeal membrane oxygenation for early graft failure. Twenty-six patients (59%) survived to hospital discharge, and survival 12 months postextracorporeal membrane oxygenation was 24 patients (55%), lower in those with late graft failure (40% vs 67%; p 0.02). Independent risk factors for 12-month mortality were congenital heart disease, higher pulmonary vascular resistance indexed to body surface area (> 2.2 Woods U/m), and higher creatinine. Higher panel reactive antibody levels were associated with 12-month mortality in the late graft failure group only.

CONCLUSIONS

Extracorporeal membrane oxygenation can be effectively used to rescue patients with graft dysfunction after heart transplantation but is associated with high early mortality. Factors associated with mortality within 12 months include presence of congenital heart disease, renal dysfunction, elevated pulmonary vascular resistance indexed to body surface area and in those supported with extracorporeal membrane oxygenation late after heart transplantation, significant human leukocyte antigen sensitization.

Pediatric heart transplantation in the current era

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Extracorporeal membrane oxygenation use in the first 24 hours following pediatric heart transplantation: Incidence, risk factors, and outcomes

Primary graft dysfunction following HTx is associated with significant morbidity and mortality. This study aimed to assess the incidence of, risk factors for, and outcomes of children requiring ECMO within 24 hours of HTx. This study utilized a linked PHIS/SRTR database of pediatric HTx recipients (2002-2016). Post-HTx ECMO was identified using inpatient billing data. Logistic regression assessed risk factors for post-HTx ECMO. Kaplan-Meier analyses assessed in-hospital mortality and post-discharge survival. A total of 2820 patients were included with 224 (7.9%) requiring ECMO. Independent risk factors for post-HTx ECMO include age <1 year (aOR: 2.2, 95% CI: 1.3-3.7, P = 0.006) or 1-5 years (aOR: 2.1, 95% CI: 1.3-3.4, P = 0.002), and ECMO support at HTx (aOR: 27.4, 95% CI: 15.2-49.6, P < 0.001). Survival to discharge decreased with increasing duration of post-HTx ECMO support; 89% for 1-3 days, 79.1% for 4-6 days, 63.2% for 7-9 days, and 18.8% for ≥10 days. There was no difference in long-term survival for patients requiring post-HTx ECMO who survived to hospital discharge (P = 0.434). There are identifiable risk factors associated with the need for ECMO in the post-HTx period. Length of time on ECMO post-HTx is strongly associated with the risk of in-hospital mortality. Patients who require ECMO early post-HTx and survive to discharge have comparable outcomes to patients who did not require ECMO.