Endomyocardial biopsy in pediatric heart transplant recipients: a useful exercise? (Analysis of 1,169 biopsies)

Decreasing Endomyocardial Biopsy Frequency in Pediatric Heart Transplantation Using A Rejection Risk Prediction Score-A Single Center Study

BACKGROUND

Rejection remains an important cause of morbidity and mortality after pediatric heart transplantation (HT). Endomyocardial biopsy (EMB) is the gold standard for rejection diagnosis, but it comes with procedural risk. The frequency of EMB varies significantly across centers. Since April 2018, our center's surveillance EMB schedule is based on a rejection risk prediction score employing age, pre-HT diagnosis, and panel reactive antibodies (PRA). We aimed to evaluate outcomes in the 1st year post-HT before and after risk score implementation.

METHODS

Patients who underwent HT at our center at ≤ 18 years of age from January 2015 to December 2020 were reviewed. The primary endpoint was rejection-free survival at 1 year-post- HT. Clinical characteristics were compared for patients transplanted in Era 1 (January 2015-April 2018) and Era 2 (April 2018-December 2020). Cumulative 1-year survival free from rejection and from rejection with hemodynamic compromise (RHC) was compared between eras using Kaplan-Meier survival analysis.

RESULTS

115 patients underwent HT during our study period (52 in Era 1 and 63 in Era 2). There was an increase in VAD utilization between eras (19% in Era 1 vs. 40% in Era 2, p = 0.025), but otherwise no significant difference in demographic or clinical variables between the two eras. No statistically significant difference in freedom from rejection or freedom from RHC was identified between the two eras. There was a 60% reduction in the median number of EMB per patient in the first year post-HT after employing the score (5 in Era 1 vs. 2 in Era 2, p < 0.001).

CONCLUSIONS

After employing a rejection risk prediction score, our center decreased the frequency of EMB without worsening early post-HT outcomes, thus establishing the clinical applicability of this tool.

Histopathological Characteristics of Percutaneous Endomyocardial Biopsy in Heart Transplant Rejection Surveillance: A Single Center Experience

BACKGROUND

Heart transplantation (HT) remains the ultimate treatment for end-stage heart failure. An endomyocardial biopsy (EMB) is "the gold standard" diagnostic procedure used in HT rejection surveillance. The aim of this study is to provide a detailed analysis of the histopathological characteristics of the EMB and to investigate if there is a correlation between some histopathological changes, such as fibrosis, vasculitis, Quilty effect (Q.E.), myocytes damage, and the presence of episodes of acute rejection.

METHODS

In this retrospective study, 200 EMBs were included, coming from 65 patients transplanted in the Emergency Institute for Cardiovascular Diseases and Transplantation (ICvDT) Targu Mures between 2012 and 2024. Fibrosis, vasculitis, Q.E., myocyte damage, etc., were microscopically evaluated to see if these parameters correlate with rejection episodes.

RESULTS

The mean age was 38.18 years (SD 15.67), 25% of biopsies being recorded in the 41-50 age group. 77.14% of total acute cellular rejection (ACR) was of mild rejection, with most registered in the 11-20 age group; the cases of severe rejection being recorded in the 41-50 age group. Antibody-mediated rejection (AMR) was recorded more frequently in women with a representation of 23.4%, compared to 8.5% of men. 86.7% (39 cases) of the total number of EMBs with fibrosis score 3 and 71.4% (15 cases) of the total EMBs with fibrosis score 2 were recorded in men, compared to the 28.6% (6 cases) of fibrosis score 2 recorded in women (p = 0.013). 50.0% of all the EMB recorded in the 61-70 age group showed fibrosis score 3, compared to 34.8% of those from the 21-30 age group. The Q.E. was identified in 13% of the biopsies and, in some patients, it was observed across 3-4 successive biopsies. Mild vasculitis was associated in 34.9% of cases with ISHLT ≥ 1R and moderate vasculitis was associated in 87.5% of cases with ISHLT ≥ 1R.

CONCLUSIONS

Fibrosis was detected much more frequently in men and in the 61-70 age group. In addition to the histopathological changes specific to acute rejection, there are other pathological changes, such as the Q.E., and vasculitis and myocytes damage and disarray, that seem to suggest a close connection with rejection, but extensive studies are needed to confirm this.

New Non-Invasive Imaging Technologies in Cardiac Transplant Follow-Up: Acquired Evidence and Future Options

Heart transplantation (HT) is the established treatment for end-stage heart failure, significantly enhancing patients' survival and quality of life. To ensure optimal outcomes, the routine monitoring of HT recipients is paramount. While existing guidelines offer guidance on a blend of invasive and non-invasive imaging techniques, certain aspects such as the timing of echocardiographic assessments and the role of echocardiography or cardiac magnetic resonance (CMR) as alternatives to serial endomyocardial biopsies (EMBs) for rejection monitoring are not specifically outlined in the guidelines. Furthermore, invasive coronary angiography (ICA) is still recommended as the gold-standard procedure, usually performed one year after surgery and every two years thereafter. This review focuses on recent advancements in non-invasive and contrast-saving imaging techniques that have been investigated for HT patients. The aim of the manuscript is to identify imaging modalities that may potentially replace or reduce the need for invasive procedures such as ICA and EMB, considering their respective advantages and disadvantages. We emphasize the transformative potential of non-invasive techniques in elevating patient care. Advanced echocardiography techniques, including strain imaging and tissue Doppler imaging, offer enhanced insights into cardiac function, while CMR, through its multi-parametric mapping techniques, such as T1 and T2 mapping, allows for the non-invasive assessment of inflammation and tissue characterization. Cardiac computed tomography (CCT), particularly with its ability to evaluate coronary artery disease and assess graft vasculopathy, emerges as an integral tool in the follow-up of HT patients. Recent studies have highlighted the potential of nuclear myocardial perfusion imaging, including myocardial blood flow quantification, as a non-invasive method for diagnosing and prognosticating CAV. These advanced imaging approaches hold promise in mitigating the need for invasive procedures like ICA and EMB when evaluating the benefits and limitations of each modality.

Short-term clinical outcomes and predicted cost savings of dd-cfDNA-led surveillance after pediatric heart transplantation

BACKGROUND

Endomyocardial biopsy (EMB)-led surveillance is common after pediatric heart transplantation (HT), with some centers performing periodic surveillance EMBs indefinitely after HT. Donor derived cell-free DNA (dd-cfDNA)-led surveillance offers an alternative, but knowledge about its clinical and economic outcomes, both key drivers of potential utilization, are lacking.

METHODS

Using single-center recipient and center-level data, we describe clinical outcomes prior to and since transition from EMB-led surveillance to dd-cfDNA-led surveillance of pediatric and young adult HT recipients. These data were then used to inform Markov models to compare costs between EMB-led and dd-cfDNA-led surveillance strategies.

RESULTS

Over 34.5 months, dd-cfDNA-led surveillance decreased the number of EMBs by 81.8% (95% CI 76.3%-86.5%) among 120 HT recipients (median age 13.3 years). There were no differences in the incidences of graft loss or death among all recipients followed at our center prior to and following implementation of dd-cfDNA-led surveillance (graft loss: 2.9 vs. 1.5 per 100 patient-years; p = .17; mortality: 3.7 vs. 2.2 per 100 patient-years; p = .23). Over 20 years from HT, dd-cfDNA-led surveillance is projected to cost $8545 less than EMB-led surveillance. Model findings were robust in sensitivity and scenario analyses, with cost of EMB, cost of dd-cfDNA testing, and probability of elevated dd-cfDNA most influential on model findings.

CONCLUSIONS

dd-cfDNA-led surveillance shows promise as a less invasive and cost saving alternative to EMB-led surveillance among pediatric and young adult HT recipients.

Findings and Outcome of Transcatheter Right Ventricular Endomyocardial Biopsy and Hemodynamic Assessment in Children with Suspected Myocarditis or Cardiomyopathy

OBJECTIVE

The study objective is assessing findings and outcome in children with suspected cardiomyopathy (CMP) or myocarditis undergoing cardiac catheterization with transcatheter right ventricular endomyocardial biopsy (RV-EMB).

METHODS

All consecutive children undergoing cardiac catheterization with RV-EMB for suspected CMP/myocarditis between 2002-2021 were analysed regarding clinical presentation, cardiac biomarkers, periprocedural management, hemodynamic, histological/immunohistological findings, and outcome.

RESULTS

Eighty-five RV-EMBs were performed in 81 patients at a median age of 6.8 (IQR 9.9) years and a bodyweight of 20 (32.2) kg. Histological/immunohistological findings of RV-EMB revealed dilated CMP in 10 (12%), chronic myocarditis in 28 (33%), healing myocarditis in 5 (6%), acute myocarditis in 9 (11%), other heart muscle diseases in 23 (27%) (7 restrictive CMP, 5 hypertrophic CMP, 4 toxic/anthracycline-induced CMP, 4 endocardfibroelastosis, 1 arrhythmogenic right ventricular CMP, 1 laminin CMP, 1 haemangioma), no conclusive histology in 7 (8%), and normal histology in 3 (4%) patients. Median LVEDP was 17 mmHg (IQR 9), LAP 15 mmHg (10), and PVR 1.83 (1.87) Wood Units/m². There were 3 major complications (3%), all patients recovered without any sequelae. At follow-up (median 1153, IQR 1799 days) 47 (59%) patients were alive, 11 (13%) dead, 15 (18%) underwent cardiac transplantation, and 8 (9%) were lost to follow-up. Death/cardiac transplantation occurred within 3 years from RV-EMB. All patients with an acute myocarditis survived. NT-pro-BNP, echo parameters, and invasive hemodynamics correlate independently with death/cardiac transplant.

CONCLUSION

Hemodynamic invasive data and morphological findings in RV-EMB complete clinical diagnosis in children with suspected CMP/myocarditis and provide important information for further clinical management.

Cardiovascular Magnetic Resonance for Rejection Surveillance After Cardiac Transplantation

BACKGROUND

Endomyocardial biopsy (EMB) is the gold standard method for surveillance of acute cardiac allograft rejection (ACAR) despite its invasive nature. Cardiovascular magnetic resonance (CMR)-based myocardial tissue characterization allows detection of myocarditis. The feasibility of CMR-based surveillance for ACAR-induced myocarditis in the first year after heart transplantation is currently undescribed.

METHODS

CMR-based multiparametric mapping was initially assessed in a prospective cross-sectional fashion to establish agreement between CMR- and EMB-based ACAR and to determine CMR cutoff values between rejection grades. A prospective randomized noninferiority pilot study was then undertaken in adult orthotopic heart transplant recipients who were randomized at 4 weeks after orthotopic heart transplantation to either CMR- or EMB-based rejection surveillance. Clinical end points were assessed at 52 weeks.

RESULTS

Four hundred one CMR studies and 354 EMB procedures were performed in 106 participants. Forty heart transplant recipients were randomized. CMR-based multiparametric assessment was highly reproducible and reliable at detecting ACAR (area under the curve, 0.92; sensitivity, 93%; specificity, 92%; negative predictive value, 99%) with greater specificity and negative predictive value than either T1 or T2 parametric CMR mapping alone. High-grade rejection occurred in similar numbers of patients in each randomized group (CMR, n=7; EMB, n=8; P=0.74). Despite similarities in immunosuppression requirements, kidney function, and mortality between groups, the rates of hospitalization (9 of 20 [45%] versus 18 of 20 [90%]; odds ratio, 0.091; P=0.006) and infection (7 of 20 [35%] versus 14 of 20 [70%]; odds ratio, 0.192; P=0,019) were lower in the CMR group. On 15 occasions (6%), patients who were randomized to the CMR arm underwent EMB for clarification or logistic reasons, representing a 94% reduction in the requirement for EMB-based surveillance.

CONCLUSIONS

A noninvasive CMR-based surveillance strategy for ACAR in the first year after orthotopic heart transplantation is feasible compared with EMB-based surveillance.

REGISTRATION

HREC/13/SVH/66 and HREC/17/SVH/80.

AUSTRALIAN NEW ZEALAND CLINICAL TRIALS REGISTRY

ACTRN12618000672257.

Rejection surveillance in pediatric heart transplant recipients: Critical reflection on the role of frequent and long-term routine surveillance endomyocardial biopsies and comprehensive review of non-invasive rejection screening tools

BACKGROUND

Despite significant medical advances in the field of pediatric heart transplantation (HT), acute rejection remains an important cause of morbidity and mortality. Endomyocardial biopsy (EMB) remains the gold-standard method for diagnosing rejection but is an invasive, expensive, and stressful process. Given the potential adverse consequences of rejection, routine post-transplant rejection surveillance protocols incorporating EMB are widely employed to detect asymptomatic rejection. Each center employs their own specific routine rejection surveillance protocol, with no consensus on the optimal approach and with high inter-center variability. The utility of high-frequency and long-term routine surveillance biopsies (RSB) in pediatric HT has been called into question.

METHODS

Sources for this comprehensive review were primarily identified through searches in biomedical databases including MEDLINE and Embase.

RESULTS

The available literature suggests that the diagnostic yield of RSB is low beyond the first year post-HT and that a reduction in RSB intensity from high-frequency to low-frequency can be done safely with no impact on early and mid-term survival. Though there are emerging non-invasive methods of detecting asymptomatic rejection, the evidence is not yet strong enough for any test to replace EMB.

CONCLUSION

Overall, pediatric HT centers in North America should likely be doing fewer RSB than are currently performed. Risk factors for rejection should be considered when designing the optimal rejection surveillance strategy. Noninvasive testing including emerging biomarkers may have a complementary role to aid in safely reducing the need for RSB.

Estimating filling pressures in paediatric heart transplant recipients using echocardiographic parameters and B-type natriuretic peptide

BACKGROUND

Longitudinal evaluation of allograft diastolic function in paediatric heart transplant recipients is important for early detection of acute rejection, cardiac allograft vasculopathy, and graft dysfunction. Mean diastolic right atrial and pulmonary capillary wedge pressures obtained at catheterisation are the reference standards for assessment. Echocardiography is non-invasive and more suitable for serial surveillance, but individual parameters have lacked accuracy. This study aimed to identify covariates of post-transplant mean right atrial and pulmonary capillary wedge pressures, including B-type natriuretic peptide and certain echocardiographic parameters.

METHODS

A retrospective review of 143 scheduled cardiac catheterisations and echocardiograms from 56 paediatric recipients transplanted from 2007 to 2011 was performed. Samples with rejection were excluded. Univariate and multivariate linear regression models using backward selection were applied to a database consisting of B-type natriuretic peptide, haemodynamic, and echocardiographic data.

RESULTS

Ln B-type natriuretic peptide, heart rate z-score, left ventricular end-diastolic dimension z-score, mitral E/e', and percent interventricular septal thickening in systole were independently associated with mean right atrial pressure. Ln B-type natriuretic peptide, heart rate z-score, left ventricular end-diastolic dimension z-score, left ventricular mass (observed/predicted), and mitral E/e' were independently associated with mean pulmonary capillary wedge pressure. Covariates of B-type natriuretic peptide included mean pulmonary artery and pulmonary capillary wedge pressures, height, haemoglobin, fractional shortening, percent interventricular septal thickening in systole, and pulmonary vascular resistance index.

CONCLUSIONS

B-type natriuretic peptide and echocardiographic indices of diastolic function were independently related to post-transplant mean right atrial and pulmonary capillary wedge pressures in paediatric heart transplant recipients without rejection.

Early findings after integration of donor-derived cell-free DNA into clinical care following pediatric heart transplantation

BACKGROUND

Endomyocardial biopsy (EMB) is costly and discomforting yet remains a key component of surveillance after pediatric heart transplantation (HT). Donor-derived cell-free DNA (dd-cfDNA) has been histologically validated with high negative predictive value, offering an alternative to surveillance EMB (sEMB).

METHODS

We implemented an alternative surveillance protocol using commercially available dd-cfDNA assays in place of sEMB after pediatric HT. Recipients ≧7 months post-HT with reassuring clinical assessment were referred for dd-cfDNA. When not elevated above the manufacturers' threshold, sEMB was deferred. Subsequent clinical status and results of follow-up EMB were analyzed.

RESULTS

Over 17 months, 58 recipients [34% female, median age at HT 3.1 years (IQR 0.6-10.6)] had dd-cfDNA assessed per protocol. Median age was 14.8 years (8.4-18.3) and time from HT 6.0 years (2.2-11.2). Forty-seven (81%) had non-elevated dd-cfDNA and 11 (19%) were elevated. During a median of 8.7 months (4.2-15), all are alive without allograft loss/new dysfunction. Among those with non-elevated dd-cfDNA, 24 (51%) had subsequent sEMB at 12.1 months (6.9-12.9) with 23 showing no acute rejection (AR): grade 0R/pAMR0 (n = 16); 1R(1A)/pAMR0 (n = 7). One had AR (grade 2R(3A)/pAMR0) on follow-up sEMB after decreased immunosuppression following a diagnosis of PTLD. All 11 with elevated dd-cfDNA had reflex EMB at 19 days (12-32) with AR in 4: grade 1R(1B-2)/pAMR0 (n = 3); 1R(1B)/pAMR2 (n = 1).

CONCLUSIONS

dd-cfDNA assessment in place of selected, per-protocol EMB decreased surveillance EMB by 81% in our pediatric HT recipient cohort with no short-term adverse outcomes. Individual center approach to surveillance EMB will influence the utility of these findings.

Impact of institutional routine surveillance endomyocardial biopsy frequency in the first year on rejection and graft survival in pediatric heart transplantation

BACKGROUND

Routine surveillance biopsy (RSB) is performed to detect asymptomatic acute rejection (AR) after heart transplantation (HT). Variation in pediatric RSB across institutions is high. We examined center-based variation in RSB and its relationship to graft loss, AR, coronary artery vasculopathy (CAV), and cost of care during the first year post-HT.

METHODS

We linked the Pediatric Health Information System (PHIS) and Scientific Registry of Transplant Recipients (SRTR, 2002-2016), including all primary-HT aged 0-21 years. We characterized centers by RSB frequency (defined as median biopsies performed among recipients aged ≥12 months without rejection in the first year). We adjusted for potential confounders and center effects with mixed-effects regression analysis.

RESULTS

We analyzed 2867 patients at 29 centers. After adjusting for patient and center differences, increasing RSB frequency was associated with diagnosed AR (OR 1.15 p = 0.004), a trend toward treated AR (OR 1.09 p = 0.083), and higher hospital-based cost (US$390 315 vs. $313 248, p < 0.001) but no difference in graft survival (HR 1.00, p = 0.970) or CAV (SHR 1.04, p = 0.757) over median follow-up 3.9 years. Center RSB-frequency threshold of ≥2/year was associated with increased unadjusted rates of treated AR, but no association was found at thresholds greater than this.

CONCLUSION

Center RSB frequency is positively associated with increased diagnosis of AR at 1 year post-HT. Graft survival and CAV appear similar at medium-term follow-up. We speculate that higher frequency RSB centers may have increased detection of clinically less important AR, though further study of the relationship between center RSB frequency and differences in treated AR is necessary.

A Predictive Model for Intracardiac Pressures in Patients Free From Rejection or Allograft Vasculopathy After Pediatric Heart Transplantation

BACKGROUND

Despite the routine use of hemodynamic assessment in pediatric heart transplant (HT) patients, expected intracardiac pressure measurements in patients free of significant complications are incompletely described. A better understanding of the range of intracardiac pressures in these HT patients is important for the clinical interpretation of these indices and consequent management of patients.

METHODS

We conducted a retrospective chart review of pediatric HT recipients who had undergone HT between January 2010 and December 2015 at Lucile Packard Children's Hospital. We analyzed intracardiac pressures measured in the first 12 mo after HT. We excluded those with rejection, graft coronary artery disease, mechanical support, or hemodialysis. We used a longitudinal general additive model with bootstrapping technique to generate age and donor-recipient size-specific curves to characterize filling pressures through 1-y post-HT.

RESULTS

Pressure measurements from the right atrium, pulmonary artery, and pulmonary capillary wedge pressure were obtained in 85 patients during a total of 829 catheterizations. All pressure measurements were elevated in the immediate post-HT period and decreased to a stable level by post-HT day 90. Pressure measurements were not affected by age group, donor-recipient size differences, or ischemic time.

CONCLUSIONS

Intracardiac pressures are elevated in the early post-HT period and decrease to levels typical of the native heart by 90 d. Age, donor-to-recipient size differences, and ischemic time do not contribute to differences in expected intracardiac pressures in the first year post-HT.

Outcomes of low-intensity biopsy surveillance for rejection in paediatric cardiac transplantation

BACKGROUND

Significant inter-centre variability in the intensity of endomyocardial biopsy surveillance for rejection following paediatric cardiac transplantation has been reported. Our aim was to determine if low-intensity biopsy surveillance with two scheduled biopsies in the first year would produce outcomes similar to published registry outcomes.

METHODS

A retrospective study of paediatric recipients transplanted between 2008 and 2014 using a low-intensity biopsy protocol consisting of two surveillance biopsies at 3 and 12-13 months in the first post-transplant year, then annually thereafter. Additional biopsies were performed based on echocardiographic and clinical surveillance. Excluded were recipients that were re-transplanted or multi-organ transplanted or were followed at another institution.

RESULTS

A total of 81 recipients in the first 13 months after transplant underwent an average of 2 (SD ± 1.3) biopsies, 24 ± 6.8 echocardiograms, and 17 ± 4.4 clinic visits per recipient. During the 13-month period, 19 recipients had 24 treated rejection episodes, with the first at an average of 2.8 months post-transplant. The 3-, 12-, 36-, and 60-month conditional on discharge graft survival were 100%, 98.8%, 98.8%, and 90.4%, respectively, comparable to reported figures in major paediatric registries. At a mean follow-up of 4.7 ± 2.1 years, four patients (4.9%) developed cardiac allograft vasculopathy, three (3.7%) developed a malignancy, and seven (8.6%) suffered graft loss.

CONCLUSION

Rejection surveillance with a low-intensity biopsy protocol demonstrated similar intermediate-term outcomes and safety measures as international registries up to 5 years post-transplant.

Long-term surveillance biopsy: Is it necessary after pediatric heart transplant?

Due to limited and conflicting data in pediatric patients, long-term routine surveillance endomyocardial biopsy (RSB) in pediatric heart transplant (HT) remains controversial. We sought to characterize the rate of positive RSB and determine factors associated with RSB-detected rejection. Records of patients transplanted at a single institution from 1995 to 2015 with >2 year of post-HT biopsy data were reviewed for RSB-detected rejections occurring >2 year post-HT. We illustrated the trajectory of significant rejections (ISHLT Grade ≥3A/2R) among total RSB performed over time and used multivariable logistic regression to model the association between time and risk of rejection. We estimated Kaplan-Meier freedom from rejection rates by patient characteristics and used the log-rank test to assess differences in rejection probabilities. We identified the best-fitting Cox proportional hazards regression model. In 140 patients, 86% did not have any episodes of significant RSB-detected rejection >2 year post-HT. The overall empirical rate of RSB-detected rejection >2 year post-HT was 2.9/100 patient-years. The percentage of rejection among 815 RSB was 2.6% and remained stable over time. Years since transplant remained unassociated with rejection risk after adjusting for patient characteristics (OR = 0.98; 95% CI 0.78-1.23; P = 0.86). Older age at HT was the only factor that remained significantly associated with risk of RSB-detected rejection under multivariable Cox analysis (P = 0.008). Most pediatric patients did not have RSB-detected rejection beyond 2 years post-HT, and the majority of those who did were older at time of HT. Indiscriminate long-term RSB in pediatric heart transplant should be reconsidered given the low rate of detected rejection.

Cost-effectiveness of the National Pediatric Heart Transplantation Program in Australia

OBJECTIVES

Cost data for pediatric heart transplantation are scarce. We examined hospital cost of the national pediatric heart transplantation program in Australia and assessed factors associated with increased costs.

METHODS

The hospital cost of all children who underwent heart transplantation at a national referral center between January 2003 and June 2015 and were followed more than 1 year was retrospectively analyzed. Lifetime follow-up costs were adjusted for quality of life and projected to life expectancy. All costs were reported in 2016 US dollars.

RESULTS

Of 70 children who underwent heart transplantation in the study period, 61 were followed more than 1 year after transplantation (mean, 4.3 ± 2.5 years). Mean cost of primary heart transplantation was $278,480 (95% confidence interval, 219,282-337,679) and did not change over time. Pretransplant mechanical circulatory support was required in 36% (22/61) of children. On multivariable analysis, greater admission costs were associated with ventricular assist device and pretransplant length of stay. Mean annual follow-up cost after discharge was $55,823 (95% confidence interval, 47,631-64,015) in the first year and $12,119 (95% confidence interval, 8578-15,661) thereafter. Increased first-year follow-up costs were associated with endomyocardial biopsies and length of readmissions. Cost per quality-adjusted life-year gained varied from $29,161 to $44,481 on sensitivity analysis. Freedom from treated rejections was 65.5% at 1 year, 63.2% at 3 years, and 59.5% at 5 years. Endomyocardial biopsies contributed to 52% of first-year follow-up costs.

CONCLUSIONS

Primary pediatric heart transplantation in Australia is cost-effective for long-term survivors, even for those supported by ventricular assist device. Surveillance endomyocardial biopsy was a major contributor to post-transplantation costs. Selective targeting of surveillance biopsies may be cost-saving.

Impact of routine surveillance biopsy intensity on the diagnosis of moderate to severe cellular rejection and survival after pediatric heart transplantation

Data are lacking on RSB intensity and outcomes after pediatric heart transplantation. PHTS centers received a survey on RSB practices from 2005 to present. PHTS data were obtained for 2010-2013 and integrated with center-matched survey responses for analysis. Survey response rate was 82.6% (38/46). Centers were classified as low-, moderate-, and high-intensity programs based on RSB frequency (0-more than 8 RSB/y). RSB intensity decreased with increasing time from HT. Age at HT impacted RSB intensity mostly in year 1, with little to no impact in later years. Most centers have not replaced RSB with non-invasive methods, but many added ECHO and biomarker monitoring. Higher RSB intensity was not associated with decreased 4-year mortality (P=.63) or earlier detection of moderate to severe (ISHLT grade 2R/3R) cellular rejection (RSBMSR) in the first year (P=.87). First-year RSBMSR incidence did not differ with intensity or age at HT. Significant variability exists in RSB intensity, but with no impact on timing and incidence of RSBMSR or 4-year mortality. Reduction in RSB frequency may be safe in certain patients after pediatric HT.

Impact of age on incidence and prevalence of moderate-to-severe cellular rejection detected by routine surveillance biopsy in pediatric heart transplantation

BACKGROUND

The effect of age at transplant on rejection detected by routine surveillance biopsy (RSB) in pediatric heart transplant (HT) recipients is unknown. We hypothesized there would be low diagnostic yield and decreased prevalence of rejection detected on RSB in infants (age <1 year) when compared with children (age 1 to 9 years) and adolescents (age 10 to 18 years).

METHODS

We utilized Pediatric Heart Transplant Study (PHTS) data from 2010 to 2013 to analyze moderate-to-severe (ISHLT Grade 2R/3R) cellular rejection (MSR) detected only on RSB (RSBMSR).

RESULTS

RSB detected 280 of 343 (81.6%) episodes of MSR. RSBMSR was detected in all age groups even >5 years after HT. Infant RSBMSR had a greater proportion (p = 0.0025) occurring >5 years after HT (39.2 vs 18.4 vs 10.8%) and a lower proportion (p = 0.0009) occurring in the first year after HT (25.5 vs 60.6 vs 51.7%) compared with children and adolescents, respectively. Freedom from RSBMSR was 87 ± 7% in infants, 76 ± 6% in children and 73 ± 7% in adolescents 4 years after HT. In 1-year survivors who had RSBMSR in the first year after HT, the risk of RSBMSR occurring in Years 2 to 4 was significantly (p < 0.0001) greater than patients without RSBMSR in the first year (hazard ratio 21.28, 95% confidence interval 10.87 to 41.66), regardless of recipient age.

CONCLUSIONS

RSBMSR exists in all age groups after pediatric HT with long-term follow-up. The prevalence in infant recipients is highest >5 years after HT. Those with RSBMSR in the first year after HT are at a high risk for recurrent rejection regardless of age at HT.

Variation in the use of surveillance endomyocardial biopsy among pediatric heart transplant centers over time

EMB is widely utilized for graft surveillance after HTx; however, there is significant variation in the frequency of surveillance EMB use during the first year post-HTx. The aim of this study was to assess changes in the utilization of surveillance EMB over time among member institutions of PHTS. A survey of PHTS centers assessing the frequency of surveillance EMB use during the first year post-HTx was conducted in 2006. The same survey was repeated in 2014 to assess changes in practice over time. The number of EMB in infants ranged from 0 to 9 and in adolescents 0 to 16. The number of EMB decreased or remained unchanged in the majority of centers. Fewer EMB are performed in infants compared to adolescents and this practice did not change over time. There was a significant decrease in surveillance EMB use in adolescents (p = 0.012). International centers perform significantly fewer EMB in adolescents when compared to centers within the United States (p = 0.006). There continues to be significant variation in the utilization of surveillance EMB, with a shift toward less reliance on EMB for adolescents in the current era. Further research is necessary to determine the optimal frequency of invasive monitoring that reduces costs without compromising outcomes.

Endomyocardial biopsy and selective coronary angiography are low-risk procedures in pediatric heart transplant recipients: results of a multicenter experience

BACKGROUND

No prior reports documenting the safety and diagnostic yield of cardiac catheterization and endomyocardial biopsy (EMB) in heart transplant recipients include multicenter data.

METHODS

Data on the safety and diagnostic yield of EMB procedures performed in heart transplant recipients were recorded in the Congenital Cardiac Catheterization Outcomes Project database at 8 pediatric centers during a 3-year period. Adverse events (AEs) were classified according to a 5-level severity scale. Generalized estimating equation models identified risk factors for high-severity AEs (HSAEs; Levels 3-5) and non-diagnostic biopsy samples.

RESULTS

A total of 2,665 EMB cases were performed in 744 pediatric heart transplant recipients (median age, 12 years [interquartile range, 4.8, 16.7]; 54% male). AEs occurred in 88 cases (3.3%), of which 28 (1.1%) were HSAEs. AEs attributable to EMB included tricuspid valve injury, transient complete heart block, and right bundle branch block. Amongst 822 cases involving coronary angiography, 10 (1.2%) resulted in a coronary-related AE. There were no myocardial perforations or deaths. Multivariable risk factors for HSAEs included fewer prior catheterizations (p = 0.006) and longer case length (p < 0.001). EMB yielded sufficient tissue for diagnosis in 99% of cases. Longer time since heart transplant was the most significant predictor of a non-diagnostic biopsy sample (p < 0.001).

CONCLUSIONS

In the current era, cardiac catheterizations involving EMB can be performed in pediatric heart transplant recipients with a low AE rate and high diagnostic yield. Risk of HSAEs is increased in early post-transplant biopsies and with longer case length. Longer time since heart transplant is associated with non-diagnostic EMB samples.

Decline in rejection in the first year after pediatric cardiac transplantation: a multi-institutional study

BACKGROUND

Rejection is a major cause of morbidity and mortality after pediatric heart transplantation (HTx). Survival after pediatric HTx has improved over time, but whether there has been an era-related improvement in the occurrence of allograft rejection is unknown.

METHODS

The Pediatric Heart Transplant Study (PHTS) database was queried for patients who underwent HTx from January 1993 to December 2005 to determine the incidence of rejection and identify factors associated with the first episode of rejection in the first year after HTx.

RESULTS

Data were reviewed in 1,852 patients from 36 centers. The incidence of rejection declined over 13 years at a rate of -2.58 +/- 0.41 (p < 0.001) from approximately 60% to 40% (p < 0.001). The mean number of episodes of rejection also significantly fell at a rate of -0.05 +/- 0.01 per patient/year from 1.19 to 0.66 (p < 0.001). The incidence of rejection with hemodynamic compromise and death from rejection did not change. Multivariate analysis for the risk of a first rejection episode demonstrated decreased risk of rejection with later year of HTx (odds ratio [OR], 0.88; 95% confidence interval [CI], 0.85-0.91; p < 0.001) and use of mechanical support (OR, 0.65; 95% CI, 0.42-0.99; p = 0.046). Increased risk of rejection was associated with positive donor-specific crossmatch (OR, 1.85; 95% CI, 1.18-2.88; p = 0.007) and older recipient age (OR, 1.05; 95% CI, 1.02-1.07; p < 0.001).

CONCLUSIONS

Although the overall incidence and prevalence of rejection has substantially decreased over time in pediatric HTx recipients in the first year after HTx, the rate of rejection with hemodynamic compromise or death from rejection remains unchanged.

Update on cardiac transplantation pathology

CONTEXT

The endomyocardial biopsy is the mainstay for monitoring acute allograft rejection in heart transplantation. Objective and accurate assessment of cellular and humoral types of rejection is important to optimize immunosuppressive therapy, avoid therapeutic complications, and improve patient outcome. The grading system for evaluation of heart transplant biopsies published in 1990 was revised in 2004 after more than a decade of implementation.

OBJECTIVE

In this review, we focus on a practical approach to the evaluation of human heart transplant biopsies as diagnostic surgical pathologic specimens. We discuss the revised International Society of Heart and Lung Transplantation working formulation.

DATA SOURCES

We reviewed pertinent literature, incorporating ideas and vast experience of participants in various work groups that led to the revision of the 1990 grading system.

CONCLUSIONS

The grading system for cellular rejection is presented with detailed light microscopic morphology and comparison of the 1990 and 2004 International Society of Heart and Lung Transplantation working formulations. We show how the pathologic recognition of cellular rejection and antibody-mediated rejection has evolved. We emphasize the interpretation of immunostains for complement components C4d and C3d in the diagnosis of antibody-mediated rejection. Evidence of regulation of complement activation in human heart transplant biopsies is presented in this context. We also discuss the pitfalls, caveats, and artifacts in the interpretation of allograft endomyocardial biopsies. Lastly, we discuss the pathology of human cardiac allograft vasculopathy in practical detail.

Unsuspected rejection episodes on routine surveillance endomyocardial biopsy post-heart transplant in paediatric patients

The use of routine endomyocardial biopsies post-heart transplant in children remains controversial. It is generally accepted as the gold standard for detecting rejection, but details of the surveillance protocol, such as number and timing of biopsies, remain uncertain, with suggestions that recent advances in immunosuppressant therapy have obviated the need to perform surveillance biopsies. We retrospectively analysed results of endomyocardial biopsies performed in our unit since the introduction of a policy of three routine biopsies in the first six months post-transplantation. We specifically examined only routine surveillance biopsies in order to determine whether clinically unsuspected cases of rejection were identified. Between January 2002 and April 2006, 63 children completed three biopsies in the first six months post-transplant. Of 189 surveillance endomyocardial biopsies, 19 (10%) patients showed significant, grade III or above, rejection. One patient had two episodes of rejection. In only one case the child was haemodynamically unstable, four cases were mildly unwell, and 14 of 19 (74%) cases demonstrated no cardiac symptoms. Four of eight cases treated with sirolimus for some part of their post-transplant course had an episode of rejection and of 54 tacrolimus-treated patients, 13 had an episode of asymptomatic rejection detected. One of the seven infants had significant episode of rejection. Asymptomatic, clinically significant rejection is detected in about 10% of biopsies overall using a three-biopsy protocol in the first six months after paediatric heart transplantation, and occurs in 24% of tacrolimus-treated patients. More frequent surveillance appears needed in children treated with sirolimus, but less frequent surveillance may be possible in infants.

Impact of ELISA-Detected Anti-HLA Antibodies on Pediatric Cardiac Allograft Outcome

In this study, we determine whether the presence of enzyme-linked immunosorbent assay (ELISA) detected anti-human leukocyte antigen (HLA) antibodies correlates with acute and chronic rejection in pediatric heart transplantation (Tx). Forty-five patients, who had serial ELISA pre- and posttransplantation, were studied. Age at Tx was 8.2 +/- 7.2 years. Acute rejection (AR) was defined as International Society for Heart and Lung Transplantation Grade > or =3a. Patients were defined as rejectors (22 cases) if they had recurrent AR or steroid-resistant AR within the first year post-Tx; the other cases (23) were defined as nonrejectors. Overall, 219 samples were analyzed. Twenty-two of the 45 had pre- or post-Tx anti-HLA antibodies: 77% in rejectors (17/22) and only 22% in nonrejectors (5/23), p = 0.0002. Pre-Tx HLA antibodies were present in 12 cases (27%). Presensitization was more frequent in rejectors (11/22, 50%) than in nonrejectors (1/23, 4%, p = 0.0005). Nineteen cases retained (9 cases) or developed (10 cases) anti-HLA antibodies post-Tx: 14 in rejectors (63.6%) and 5 in nonrejectors (21.7%), p = 0.003. Four of eight cases with coronary artery disease (50%) had preformed anti-HLA antibodies compared with 8 of 37 without coronary artery disease (25.6%) (p = 0.09). Preformed, persistent, and de novo ELISA-detected anti-HLA antibodies were correlated with first-year acute rejection profile.

Pediatric heart transplantation: immunosuppression and its complications

PURPOSE OF REVIEW

Advances in immunosuppression have contributed to the significant improvements in outcome for pediatric heart transplant recipients in the past two decades. The large increase in the number of available immunosuppressive agents in the past few years mandates that those caring for this complex group of patients remain up to date in this rapidly advancing field.

RECENT FINDINGS

In this review, we evaluate recent studies of immunosuppressive efficacy, end-organ toxicities, and side effects of nonspecific immunosuppression with currently used regimens. In addition, we examine new findings that attempt to define the genetic contribution to rejection profiles, immunosuppressive efficacy, and drug disposition after heart transplantation in children.

SUMMARY

The continuous evaluation of new immunosuppressive regimens will help to elucidate the optimal treatment regimens for pediatric heart transplant recipients. Unfortunately, the small number of transplantations means that it is unlikely that pivotal randomized, controlled trials will ever be performed in this population. Extrapolation from adult controlled trials and experience from other pediatric solid organ transplant recipient populations will continue to provide important contributions to our knowledge base. Understanding the genetic contribution to graft and patient outcomes may help us tailor immunosuppressive therapy for the individual patient.

Advances in methods for surveillance of rejection

Transplantation is an effective treatment modality for infants1 and children2 with end-stage cardiac diseases. Rejection remains a major complication (Figure 1), even in newborn infants.3 Acute rejection can best be operationally defined by clinical findings, histopathology, and/or abnormalities of ventricular function of new origin that require, and respond to, intensified immunosuppression. Mechanistically, the ability to detect acute rejection is critically dependent on the detection of significant new myocytic injury, damage, and/or death. Surveillance for rejection is critically important in determining both long and short-term outcomes following cardiac transplantation. The ideal strategy for surveillance should have a high negative predictive value, correctly identifying the absence of myocytic injury, with high specificity, such that it does not falsely predict such injury.4

The yield of surveillance endomyocardial biopsies as a screen for cellular rejection in pediatric heart transplant patients

Endomyocardial biopsy is commonly used to screen for cellular rejection in pediatric heart transplant patients. The yield of EMBs when combined with newly developed immunohistochemical techniques and modern immunosuppression in pediatric heart transplant patients is unknown. After OHT, surveillance biopsies were performed on a routine basis on all pediatric patients. EMBs were also performed on symptomatic OHT patients suspected to have rejection. All positive results (greater than ISHLT grade 1B) were confirmed with immunohistochemical staining. A retrospective review of consecutive EMBs performed in this institution from January 1995 to January 2003 was performed. The echocardiographic results, clinical history and treatment changes at the time of every biopsy were also catalogued. Of the 1093 EMB results from 136 pediatric heart transplant grafts (127 patients, 64 male) reviewed, 825 biopsies were performed on patients managed with tacrolimus and 268 were performed on patients managed with cyclosporine. The patients managed with tacrolimus had an incidence of 0.85% (7/825) for significant rejection (greater than ISHLT grade 1B rejection) vs. an incidence of 4.1% (11/268) for the patients on cyclosporine (p < 0.0005). In the asymptomatic tacrolimus patients, only two screening biopsies (0.26%) manifest significant rejection, and both of these were performed within the first month after transplantation. Of the symptomatic tacrolimus patients, 9.1% (n = 5) had findings on biopsy consistent with significant cellular rejection. There were 25 patients with grade 1B rejection. Twenty-two of these patients were not treated, and all cases of grade 1B rejection resolved without clinical sequelae. For pediatric patients more than 30 days after OHT, EMB has failed to reveal significant episodes of cellular rejection in asymptomatic patients managed with tacrolimus.

Pediatric heart and lung transplantation

During the last two decades, several advances have resulted in marked improvement in medium-term survival with excellent quality of life in pediatric heart transplant recipients. These were possible due to better donor and recipient selection, increased surgical experience in transplantation for complex congenital heart disease, development of effective rejection surveillance, and wider choice of immunosuppressive medications. Despite all of these advances, recipients suffer from the adverse effects of non-specific immunosuppression including infections, post-transplant lymphoproliferative disorders and other malignancies, renal dysfunction and other important end-organ toxicities. Furthermore, newer immunosuppressive regimens appear (so far) to have had relatively little impact on the incidence of allograft coronary vasculopathy (chronic rejection). Progress in our understanding of the immunologic mechanisms of rejection and graft acceptance should lead to more targeted immunosuppressive therapy and avoidance of non-specific immunosuppression. The ultimate goal is to induce a state of tolerance, wherein the recipient will accept the allograft indefinitely without the need for long-term immunosuppression and yet remain immunocompetent to other antigens. This quest is currently being realized in many animal models of solid organ transplantation and offers great hope for the future.

The current state of, and future prospects for, cardiac transplantation in children

During the last two decades, several advances have resulted in marked improvement in medium-term survival, with excellent quality of life, in children undergoing cardiac transplantation. Improved outcomes reflect better selection of donors and recipients, increased surgical experience in transplantation for complex congenital heart disease, development of effective surveillance for rejection, and wider choice of immunosuppressive medications. Despite all of these advances, recipients continue to suffer from the adverse effects of non-specific immunosupression, including infections, induction of lymphoproliferative disorders and other malignancies, renal dysfunction, and other important end-organ toxicities. Furthermore, newer immunosuppressive regimes, thus far, appear to have had relatively little impact on the incidence of chronic rejection. Progress in our understanding of the immunologic mechanisms of rejection and graft acceptance should lead to more targeted immunosuppressive therapy and avoidance of non-specific immunosupression. The ultimate goal is to induce a state of tolerance, wherein the recipient will accept the allograft indefinitely, without the need for long-term immunusupression, and yet remain immuno-competent to all non-donor antigens. This quest is currently being realized in many animal models of solid organ transplantation, and offers great hope for the future.

Pediatric heart transplantation

Heart transplantation is now a treatment option with good outcome for infants and children with end-stage heart failure or complex, inoperable congenital cardiac defects. One-year and 5-year actuarial survival rates are high, approximately 75% and 65%, respectively, with overall patient survival half-life greater than 10 years. To date, survival has been improving as a result of reducing early mortality. Further reductions in late mortality, in part because of graft coronary artery disease and rejection, will allow achievement of the goal of decades-long survival. Quality of life in surviving children, as judged by activity, is usually "normal." Somatic growth is usually at the low normal range but linear growth can be reduced. Of infant recipients, 85% evaluated at 6 years of age or older were in an age-appropriate grade level. Long-term management of childhood heart recipients requires the collaboration of transplant physicians, given the increasing number of immunosuppressive agents and the balance between rejection and infection. Currently, recipients are maintained on immunosuppressive medications that target calcineurin (eg, cyclosporine, tacrolimus), lymphocyte proliferation (eg, azathioprine, mycophenolate mofetil [MMF], sirolimus) and, in some instances antiinflammatory corticosteroids. Emerging evidence now suggests a favorable immunologic opportunity for transplantation in childhood and, conversely, a higher mortality rate in children who have had prior cardiac surgery. Further studies are needed to define age-dependent factors that are likely to play a role in graft survival and possible graft-specific tolerance (eg, optimal conditions for tolerance induction and how immunosuppressive regimens should be changed with maturation of the immune system). As late outcomes continue to improve, the need for donor organs likely will increase, as transplantation affords a better quality and duration of life for children with complex congenital heart disease, otherwise facing a future of multiple palliative operations and chronic heart failure.

The MDR1 polymorphisms at exons 21 and 26 predict steroid weaning in pediatric heart transplant patients

Various polymorphisms of the MDR1 gene that encodes for P-glycoprotein (P-gp), a transmembrane pump, have been identified. A silent mutation C3435T in exon 26 and a G2677T mutation in exon 21 have been correlated with P-gp expression and function in humans. The objectives of this study were (a) to determine whether the MDR1 exon 21 and exon 26 polymorphisms were related to steroid weaning in a pediatric heart transplant (HTx) population, and (b) to determine whether an association exist between the MDR1 exon 21 and exon 26 polymorphisms in these patients. Sixty-nine pediatric HTx patients were studied. MDR1 genotyping was determined by polymerase chain reaction amplification, sequencing the DNA, and sequence evaluation using Polyphred software (University of Washington) to identify genotypes. The steroid dose at 1 year post-transplantation was recorded. For steroid weaning at one year post-HTx for MDR1 C3435T, 12 of 18 (67%) patients in the CC genotype were still on prednisone, whereas only 18 of 47 (38%) of the CT/TT group were still receiving prednisone (p = 0.04). Similar results were observed for the MDR1 G2677T genotyping and steroid weaning. Forty-three of 46 patients (93.5%) who have MDR1 C3435T allele also have a mutant G2677T allele (p < 0.001). We conclude that (a) a significantly larger number of MDR1 3435 CC HTx patients remain on steroids at 1 year after transplantation, and (b) the MDR1 C3435T genotype is associated with the G2677 genotype in pediatric HTx patients.

The effect of cytokine gene polymorphisms on pediatric heart allograft outcome

BACKGROUND

Cytokines play a major role in the inflammatory and immune responses that mediate allograft outcome. Several studies have shown that the production of cytokines varies among individuals and these variations are determined by genetic polymorphisms, most commonly within the regulatory region of the cytokine gene. The aim of this study was to assess the effect of these allelic variations on acute rejection after pediatric heart transplantation.

METHODS

We performed cytokine genotyping using polymerase chain reaction-sequence specific primers in 93 pediatric heart transplant recipients and 29 heart donors for the following functional polymorphisms: tumor necrosis factor-alpha (TNF-alpha) (-308), interleukin (IL)-10 (-1082, -819, and -592), TGF-beta1 (codon 10 and 25), IL-6 (-174), and interferon-gamma (INF-gamma) (+874). The distribution of polymorphisms in this population did not differ from published controls. The patients were classified as either non-rejecters (0 or 1 episode) or rejecters (> 1 episode) based on the number of biopsy proven rejection episodes in the first year after transplantation.

RESULTS

Forty-two of the 69 TNF-alpha patients (61%) in the low producer group were non-rejecters, while 9 of the 24 (37.5%) with high TNF-alpha were non-rejecters (p = 0.047). In contrast, IL-10 genotype showed the opposite finding. Forty-two of the 66 patients (64%) in the high and intermediate IL-10 group were non-rejecters, while 9 of the 26 (35%) in the low IL-10 group were non-rejecters (p = 0.011). The combination of low TNF-alpha with a high or intermediate IL-10 genotype was associated with the lowest risk of rejection (34/49 or 69% non-rejecters). Neither the distribution of the IL-6, INF-gamma, and TGF-beta1 genotype in recipients nor the donor genotype showed any association with acute rejection.

CONCLUSION

Genetic polymorphisms that have been associated with low TNF-alpha and high IL-10 production are associated with a lower number of acute rejection episodes after pediatric heart transplantation.