Pediatric Heart Transplant Patients Research Articles

Non-invasive pulse arrival time is associated with cardiac index in pediatric heart transplant patients with normal ejection fraction.

Cardiac Index (CI) is a key physiologic parameter to ensure end organ perfusion in the pediatric intensive care unit (PICU). Determination of CI requires invasive cardiac measurements and is not routinely done at the PICU bedside. To date, there is no gold standard non-invasive means to determine CI. This study aims to use a novel non-invasive methodology, based on routine continuous physiologic data, called Pulse Arrival Time (PAT) as a surrogate for CI in patients with normal Ejection Fraction. &#xD;Approach: Electrocardiogram (ECG) and photoplethysmogram (PPG) signals were collected from beside monitors at a sampling frequency of 250 samples per second. Continuous PAT, derived from the ECG and PPG waveforms was averaged per patient. Pearson's correlation coefficient was calculated between PAT and CI, PAT and heart rate (HR), and PAT and ejection fraction (EF). &#xD;Main Results: Twenty patients underwent right heart cardiac catheterization. The mean age of patients was 11.7±5.4 years old, ranging from 11 months old to 19 years old, the median age was 13.4 years old. HR in this cohort was 93.8±17.0 beats per minute. The average EF was 54.4±9.6%. The average CI was 3.51±0.72 L/min/m2, with ranging from 2.6 to 4.77 L/min/m2. The average PAT was 0.31±0.12 seconds. Pearson correlation analysis showed a positive correlation between PAT and CI (0.57, p < 0.01). Pearson correlation between HR and CI, and correlation between EF and CI was 0.22 (p = 0.35) and 0.03 (p = 0.23) respectively. The correlation between PAT, when indexed by HR (i.e. PAT × HR), and CI minimally improved to 0.58 (p < 0.01).&#xD;Significance: This pilot study demonstrates that PAT may serve as a valuable surrogate marker for CI at the bedside, as a non-invasive and continuous modality in the PICU. The use of PAT in clinical practice remains to be thoroughly investigated. &#xD.

Non-invasive myocardial tissue deformation and discoordination indices predict cardiac allograft vasculopathy in pediatric heart transplantation patients.

There is an urgent need for non-invasive imaging-based biomarkers suitable for diagnostic surveillance of cardiac allograft vasculopathy (CAV) in pediatric heart transplant (PHT) patients. The purpose of this study was to comprehensively investigate left ventricular (LV) myocardial deformation in conjunction with electromechanical discoordination in PHT. PHT patients with and without CAV were evaluated for echocardiography derived global longitudinal strain (GLS) and electromechanical discoordination indices including systolic stretch fraction (SSF) and diastolic relaxation fraction (DRF). SSF was increased in CAV(+) patients at the time of CAV diagnosis (median CAV(+) 5.0 vs. median CAV(-) 0.0, P = 0.008) and in the echocardiogram preceding the CAV diagnosis (median CAV(+) 29.0 vs. median CAV(-) 0.0, P < 0.001). DRF was also increased in the echocardiogram that preceded CAV diagnosis in CAV(+) patients (0.31 ± 0.08 vs. 0.25 ± 0.05, P = 0.008). The final model using indices 6-12 months prior to CAV diagnosis included GLS, SSF, and DRF providing AUC of 0.94 with sensitivity 98.5%, specificity 80.0%, positive predictive value 85.0%, and negative predictive value 94.1%. Systolic and diastolic electro-mechanical discoordination indices are significantly worse in PHT patients experiencing CAV. Non-invasive imaging guided surveillance using echocardiographic myocardial deformation indices can be improved by adding SSF and DRF to standard GLS measurements.

Approval of Mycophenolate Mofetil for Prophylaxis of Organ Rejection in Pediatric Recipients of Heart or Liver Transplants: A Regulatory Perspective.

On June 6, 2022, the FDA expanded the indications for mycophenolate mofetil (MMF) to include the prophylaxis of organ rejection in combination with other immunosuppressants in pediatric recipients of allogeneic heart or liver transplants aged 3 months and older. The approved oral dosing regimen for these patients was a starting dose of 600 mg/m2 with titration up to a maximum of 900 mg/m2 twice daily. Data to support efficacy in pediatric patients were derived from established pharmacokinetic (PK) relationships across approved populations, a PK study in pediatric liver transplant recipients, and information from the Scientific Registry of Transplant Recipients database. Information supporting safety was based on comparing mycophenolic acid (MPA) exposure with that in pediatric kidney transplant recipients, the published literature, and post-marketing safety reports. Efficacy in pediatric patients was established based on extrapolation of efficacy from studies in adult liver, adult heart, and pediatric kidney transplant populations, and similarity in MPA exposure between pediatric and adult patients. Review of the data supported an oral dosing regimen for pediatric heart transplant and liver transplant recipients consisting of a starting dose of 600 mg/m2 up to a maximum of 900 mg/m2 b.i.d. A dosage range for MMF is recommended recognizing that the MMF dose may be modified in clinical practice for myriad factors. The dosage recommendations in the labeling for pediatric liver and pediatric heart transplant patients are intended to permit individualized dosing based on clinical assessment of these factors.

B-12 | Safety, Feasibility and Outcomes of Echocardiogram-guided Endomyocardial Biopsies in Pediatric Heart Transplant Patients

B-12 | Safety, Feasibility and Outcomes of Echocardiogram-guided Endomyocardial Biopsies in Pediatric Heart Transplant Patients

Serologic Evaluation for Severe Acute Respiratory Syndrome Coronavirus 2 in Pediatric Heart Transplantation Recipients and Patients on a Pediatric Heart Transplantation Waiting List in a Quaternary Hospital

BackgroundThe COVID-19 pandemic has been a global reality for over three years. Serological studies have great importance for the comprehension of the virus's behavior in populations, as it can suggest the status of the epidemic in a community. This cross-sectional study aimed to analyze the serological profile for COVID-19 in patients before and after pediatric heart transplant. MethodsSerologies for IgG and IgM antibodies for Sars-CoV-2 were collected in patients of the Pediatric Cardiology and Congenital Heart Diseases unit of a Brazilian hospital between January and August 2022. In total, 174 patients were recruited: 28 on waiting list and 146 recipients. Information such as demographics (age, gender, state of origin), type of heart disease (congenital or acquired) and time after transplant were analyzed. ResultsOverall, 72 patients had a positive serology for anti-N antibodies (48,0%), being 62 transplant recipients and 10 patients on transplant waiting list, with positivity rates of 48,1% and 47,6%, respectively. Positivity rates for previously infected individuals were 62,5% and 62,1%, respectively. ConclusionsWe found that approximately half of the sample has developed IgM or IgG antibodies against the Sars-CoV-2 virus Serological studies are a relevant tool to public health for health promotion of vulnerable groups, and can be useful to future studies on the antibodies’ behavior. The duration and the level of protection given by these antibodies is still a subject being studied, and can become a key information for the protection of these populations if discovered in the future.

(1384) - Feasibility and Utility of 24-Hour Ambulatory Blood Pressure Monitoring in Pediatric Heart Transplant Patients

(1384) - Feasibility and Utility of 24-Hour Ambulatory Blood Pressure Monitoring in Pediatric Heart Transplant Patients

(1342) - Donor-Derived Cell-Free DNA in Pediatric Heart Transplant Patients

(1342) - Donor-Derived Cell-Free DNA in Pediatric Heart Transplant Patients

The effect of socioeconomic status on pediatric heart transplant outcomes at a single institution between 2013 and2022.

Disparities in pediatric heart transplant outcomes based on socioeconomic status (SES) have been previously observed. However, there is a need to reevaluate these associations in contemporary settings with advancements in transplant therapies and increased awareness of health disparities. This retrospective study aims to investigate the relationship between SES and outcomes for pediatric heart transplant patients. Data were collected through a chart review of 176 pediatric patients who underwent first orthotopic heart transplantation (OHT) at a single center from 2013 to 2021. The Area Deprivation Index (ADI), a composite score based on U.S. census data, was used to quantify SES. Cox proportional hazards models and generalized linear models were employed to analyze the association between SES and graft failure, rejection rates, and hospitalization rates. The analysis revealed no statistically significant differences in graft failure rates, rejection rates, or hospitalization rates between low-SES and high-SES pediatric heart transplant patients for our single-center study. There may be patient education, policies, and social resources that can help mitigate SES-based healthcare disparities. Additional multi-center research is needed to identify post-transplant care that promotes patient equity.

Impact of a positive crossmatch on pediatric heart transplant outcomes

BackgroundPediatric heart transplant (HT) candidates experience high waitlist mortality due to a limited donor pool that is constrained in part by anti-HLA sensitization. We evaluated the impact of CDC and Flow donor-specific crossmatch (XM) results on pediatric HT outcomes. MethodsAll pediatric HT between 1999 and 2019 in the OPTN database were included. Donor-specific XM results were sub-categorized based on CDC and Flow results. Primary outcomes were treated rejection in the first year and time to death or allograft loss. Propensity scores were utilized to adjust for differences in baseline characteristics. ResultsA total of 4695 pediatric HT patients with T-cell XM data were included. After propensity score adjustment, a positive T-cell CDC-XM was associated with two times higher odds of treated rejection (OR 2.29 (1.56,3.37)) and shorter time to death/allograft loss (HR 1.50 (1.19,1.88)) compared to a negative Flow-XM. HT recipients who were Flow-XM positive with negative/unknown CDC-XM did not have higher odds of rejection or shorter time to death/allograft loss. An isolated positive B-cell XM was also not associated with worse outcomes. Over the study period XM testing shifted from CDC- to Flow-based assays. ConclusionsA positive donor-specific T-cell CDC-XM was associated with rejection and death/allograft loss following pediatric HT. This association was not observed with a positive T-cell Flow-XM or B-cell XM result alone. The shift away from performing the CDC-XM may result in loss of important prognostic information unless the clinical relevance of quantitative Flow-XM results on heart transplant outcomes is systematically studied.

Echocardiographic assessment of pediatric heart transplantation: A single-center experience in China.

Pediatric heart transplant (HT) has become the standard of care for end-stage heart failure in children worldwide. Serial echocardiographic evaluations of graft anatomy and function during follow-up are crucial for post-HT management. However, evolution of cardiac structure and function after pediatric HT has not been well described, especially during first year post-HT. This study aimed to characterize the evolution of cardiac structure and function after pediatric HT and investigate the correlation between biventricular function with adverse clinical outcomes. A single-center retrospective study of echocardiographic data obtained among 99 pediatric HT patients was conducted. Comprehensive echocardiographic examination was performed in all patients at 1-, 3-, 6-, 9- and 12-months post-HT. We obtained structural, functional and hemodynamic parameters from both left- and right-side heart, such as left ventricular stroke volume (LVSV), left ventricular ejection fraction (LVEF), right ventricular fractional area change (RVFAC), etc. The cardiac evolution of pediatric HT patients during first post-HT year was described and compared between different time points. We also explored the correlation between cardiac function and major adverse transplant events (MATEs). 1) Evolution of left heart parameters: left atrial length, mitral E velocity, E/A ratio, LVSV and LVEF significantly increased while mitral A velocity significantly decreased over the first year after HT (P<.05). Compared with 1 month after HT, interventricular septum (IVS) and left ventricular posterior wall (LVPW) decreased at 3 months but increased afterwards. (2) Evolution of right heart parameters: right ventricular base diameter and mid-diameter; right ventricular length diameter, tricuspid E velocity, E/A ratio, tricuspid annular velocity e' at free wall, and RVFAC increased, while tricuspid A velocity decreased over the first year after HT (P<.05). (3) Univariate logistic regression model suggests that biventricular function parameters at 1-year post-HT (LVEF, RVFAC, tricuspid annular plane systolic excursion and tricuspid lateral annular systolic velocity) were associated with MATEs. Gradual improvement of LV and RV function was seen in pediatric HT patients within the first year. Biventricular function parameters associated with MATEs. The results of this study pave way for designing larger and longer follow-up of this population, potentially aiming at using multiparameter echocardiographic prediction of adverse events.

Risk Index Predicts Pediatric Heart Allograft Non-Utilization.

Children listed for heart transplantation face the highest waitlist mortality among all solid organ transplant patients (14%). Attempts at decreasing donor allograft non-utilization (41.5%) could potentially decrease waitlist mortality for pediatric heart transplant patients. Our aim was to quantify the non-utilization risk of pediatric donor heart allografts at the time of initial offering. Using the United Network of Organ Sharing (UNOS) database, we retrospectively analyzed 8823 deceased donors (≤18 years old) data through univariable and multivariable analysis and logistic regression models. These factors were divided into a training (n = 5882) and validation set (n = 2941). Donor clinical characteristics and laboratory values were used to predict non-utilization of donor hearts. The multivariable analysis used factors that were significant from the univariable analysis (p-value < .05), and the pediatric non-utilization risk index (pDRSI) included significant factors from the multivariable analysis, producing an overall risk score for non-utilization. With these data, we created a non-utilization risk index to predict likelihood of donor allograft non-utilization. From the 24 potential factors that were identified from univariable analysis, 17 were significant predictors (p < .05) of pediatric heart non-utilization in the multivariable analysis. Low left ventricular ejection fraction (odds ratio (OR)-35.3), hepatitis C positive donor (OR-23.3), high left ventricular ejection fraction (OR-3.29), and hepatitis B positive donor (OR-3.27) were the most significant risk factors. The phDSRI has a C-statistic of 0.80 for the training set and 0.80 for the validation set. Using over 8000 donors, the phDSRI uses 17 significant risk factors to predict risk of pediatric heart donor allograft non-utilization.

Effects of WuZhi preparations on tacrolimus in pediatric and adult patients carrying the CYP3A5*1 allele of heart transplant during the early period after transplantation.

Wuzhi preparations (WZP) are commonly administrated with tacrolimus (TAC) in China to improve the liver function and increase the exposure of TAC. This study aims to investigate the effects of WZP on TAC in pediatric heart transplantation (HTx) patients carrying the CYP3A5*1 allele during the early period after transplantation and also make a comparison with these effects in adult recipients. A total of 81 recipients with CYP3A5*1 allele were included and divided into the pediatric group (n=29) and adult group (n=52). The changes in TAC dose-corrected trough blood concentrations (C0 /D), dose requirement as well as intra-patient variability(IPV) of C0 /D after co-therapy with WZP were evaluated. The TAC C0 /D was significantly increased 1.7 and 1.8 times after co-administration of WZP in the pediatric and adult groups, respectively. We further analyzed the pediatric patients, found that no statistical difference was observed in TAC C0 /D before and after co-therapy with WZP in children <6years old. The changes of C0 /D increased with the dose of the active ingredient (Schisantherin A) in adult patients, but not in pediatric patients. TAC IPV was reduced by 10.5% in pediatric patients and 4.8% in adult patients when co-administrated with WZP. Furthermore, after taking WZP, the AST and TB were dramatically lowered in pediatric recipients. Our study is the first attempt to demonstrate the effects of WZP on TAC in pediatric HTx recipients. By comparing these effects to those observed in adult recipients, valuable insights can be gained regarding the efficacy and potential benefits of WZP in the pediatric population.

Prevalence and spectrum of infectious and inflammatory dermatologic conditions occurring in pediatric heart transplant patients on a predominantly mTOR-based immune suppressive regimen: A retrospective chart review.

Pediatric heart transplant patients are routinely followed in dermatology clinics due to elevated risk of cutaneous malignancy. However, transplant patients may experience other, non-cancer-related dermatologic conditions including skin infections, inflammatory diseases, and drug eruptions that can cause significant medical and psychosocial comorbidity. A retrospective chart review of all pediatric heart transplant patients at Mayo Clinic Children's Center in Rochester, MN, was performed to determine the prevalence and spectrum of non-cancer dermatologic conditions. Statistical analysis was conducted to look for associations between episodes of rejection and skin condition development. Of the 65 patients who received heart transplants under the age of 18 and were followed at Mayo Clinic, 69% (N = 45) were diagnosed with at least one skin condition between transplant and the time of most recent follow-up. Sixty-two percent (N = 40) of patients were diagnosed with an inflammatory skin condition (most commonly acne and atopic dermatitis), 45% (N = 29) with an infectious skin condition (most commonly warts and dermatophyte infection), and 32% (N = 21) with a drug eruption (most commonly unspecified rash and urticaria). No association was found between presence of skin disease and number of rejection episodes. Non-cancer dermatologic conditions are prevalent within pediatric heart transplant recipients and may directly impact their medical needs and quality of life. Dermatologist involvement in the care of post-transplant pediatric patients is important, not only for cancer screening but also for diagnosis and treatment of common infectious and inflammatory skin conditions.

Cardiac magnetic resonance assessment of acute rejection and cardiac allograft vasculopathy in pediatric heart transplant

In pediatric heart transplant (PHT), cardiac catheterization with endomyocardial biopsy (EMB) is standard for diagnosing acute rejection (AR) and cardiac allograft vasculopathy (CAV) but is costly and invasive. To evaluate the ability of cardiac magnetic resonance (CMR) to noninvasively identify differences in PHT patients with AR and CAV. Patients were enrolled at three children's hospitals. Data were collected from surveillance EMB or EMB for-cause AR. Patients were excluded if they had concurrent diagnoses of AR and CAV, CMR obtained >7days from AR diagnosis, they had EMB negative AR, or could not undergo contrasted, unsedated CMR. Kruskal-Wallis test was used to compare groups: (1) No AR or CAV (Healthy), (2) AR, (3) CAV. Wilcoxon rank-sum test was used for pairwise comparisons. Fifty-nine patients met inclusion criteria (median age 17years [IQR 15-19]) 10 (17%) with AR, and 11 (19%) with CAV. AR subjects had worse left ventricular ejection fraction compared to Healthy patients (p=0.001). Global circumferential strain (GCS) was worse in AR (p=0.054) and CAV (p=0.019), compared to Healthy patients. ECV, native T1, and T2 z-scores were elevated in patients with AR. CMR was able to identify differences between CAV and AR. CAV subjects had normal global function but abnormal GCS which may suggest subclinical dysfunction. AR patients have abnormal function and tissue characteristics consistent with edema (elevated ECV, native T1 and T2 z-scores). Characterization of CMR patterns is critical for the development of noninvasive biomarkers for PHT and may decrease dependence on EMB.

Use of volumetric absorptive microsampling and parallel reaction monitoring mass spectrometry for tacrolimus blood trough measurements at home in pediatric heart transplant patients

BackgroundMeasurement of trough levels for calcineurin inhibitors by venipuncture sampling is a mainstay of patient management in solid organ transplant recipients but challenging in pediatric patients. Volumetric Absorptive Microsampling (VAMS) is a patient-friendly, minimally invasive sampling technique to accurately collect blood. An assay for measurement of tacrolimus in blood using VAMS, coupled with parallel reaction monitoring (PRM) mass spectrometry, was validated in pediatric heart transplant patients. MethodsTacrolimus was measured by a newly developed high-resolution PRM assay and compared with low-resolution tandem mass spectrometry (MRM). Dried blood samples were collected from pediatric heart transplant patients (n = 35) using VAMS devices and a satisfaction survey was completed by patients/guardians. Tacrolimus concentrations were compared across whole liquid blood, dried blood spots, and capillary blood, and shipping stability determined. ResultsThe PRM assay was linear over a range 1–50 ng/mL, similar to MRM but had greater specificity due to reduced background noise. No significant differences in tacrolimus concentrations were observed between VAMS and venous blood. Tacrolimus dried on VAM tips was stable for 14 days and concentrations were unaffected by postal shipping. The variability in two simultaneously collected at-home patient samples was minimal – average concentration difference was 0.12 ± 0.94 ng/mL (p = 0.6) between paired samples. ConclusionA high resolution PRM mass spectrometry assay was developed for home-based dried blood collections for therapeutic monitoring of tacrolimus. The advantage of PRM was enhanced specificity and the VAMS devices provided a simple and convenient approach to blood sampling at home in pediatric heart transplant patients.

Abstract 11979: Cardiac MRI Adds Value in Discerning Pediatric Heart Transplant Rejection and Its Management

Introduction: Endomyocardial biopsy (EMB) drives rejection diagnosis in pediatric heart transplant patients but is subject to false negatives and carries risk. Cardiac MRI can detect and quantify myocardial fibrosis and edema with T1 and T2 mapping. Hypothesis: Cardiac MRI may improve discernment of acute rejection in pediatric transplant patients. Methods: Pediatric heart transplant patients referred for clinically indicated EMB underwent noncontrast MRI with T1 +T2 mapping prior to EMB. Segmental T1 and T2 values were measured for base/mid/apex segments. Mean and peak T1+ T2 were quantified per encounter. Rejection treatment was per institutional protocol, and categorized as (A) no changes, (B) oral therapy initiated, or (C) IV therapy initiated. Treatment decisions were blinded to MRI results. Treatment category and T1+T2 were compared with Fisher’s exact test and logistic regression. Results: 89 encounters in 34 patients (median age 13.2y (IQR 8.3-16.8), BSA 1.39 m2 (1.09-1.65), 44.1% female) were successfully completed, with treatment groups A 11%, B 8%, C 81%. Median T1 mean and T1 peak values were (1022 ms (994-1040) and 1077 ms (1056, 1113)), respectively. Median T2 mean and T2 peak values were (50.4 ms (48.4-53.2) and 57.4 ms (53.1-60.8)), respectively. Higher T2 mean and T2 peak predict need for IV therapy; the strongest discriminator was T2 mean &gt; 54.5 (AUC = 0.801, 95% CI: 0.630, 0.972) Table 1. T1 mean and T1 peak were not significant in predicting rejection requiring IV therapy. Adding T1 mean to T2 mean did not improve the AUC (0.804 (95% CI: 0.637, 0.971), DeLong p=0.74). Finally, the odds ratio of new IV rejection therapy for T2 mean values &gt; 54.5 ms is 16.1 (95% confidence interval: 3.6 - 72.6, p&lt;0.001). Conclusions: Average T2 values (cutoff &gt; 54.5 ms) were efficacious at identifying need for IV treatment for rejection in pediatric heart transplant patients, regardless of T1 values. MRI is a promising noninvasive test to identify children at risk of rejection.

Accuracy of free-breathing multi-parametric SASHA in identifying T1 and T2 elevations in pediatric orthotopic heart transplant patients.

T1/T2 parametric mapping may reveal patterns of elevation ("hotspots") in myocardial diseases, such as rejection in orthotopic heart transplant (OHT) patients. This study aimed to evaluate the diagnostic accuracy of free-breathing (FB) multi-parametric SAturation recovery single-SHot Acquisition (mSASHA) T1/T2 mapping in identifying hotspots present on conventional Breath-held Modified Look-Locker Inversion recovery (BH MOLLI) T1 and T2-prepared balanced steady-state free-precession (BH T2p-bSSFP) maps in pediatric OHT patients. Pediatric OHT patients underwent noncontrast 1.5T CMR with BH MOLLI T1 and T2p-bSSFP and prototype FB mSASHA T1/T2 mapping in 8 short-axis slices. FB and BH T1/T2 hotspots were segmented using semi-automated thresholding (ITK-SNAP) and their 3D coordinate locations were collected (3-Matic, Materialise, Leuven, Belgium). Receiver operator characteristic curve analysis and measures of central tendency were utilized. 40 imaging datasets from 23 pediatric OHT patients were obtained. FB mSASHA yielded a sensitivity of 82.8% for T1 and 80% for T2 maps when compared to the standard BH MOLLI, as well as 100% specificity for both T1 and T2 maps. When identified on both FB and BH maps, hotspots overlapped in all cases, with an average long axis offset between FB and BH hotspot centers of 5.8mm (IQR 3.5-8.2) on T1 and 5.9mm (IQR 3.5-8.2) on T2 maps. FB mSASHA T1/T2 maps can identify hotspots present on conventional BH T1/T2 maps in pediatric patients with OHT, with high sensitivity, specificity, and overlap in 3D space. Free-breathing mapping may improve patient comfort and facilitate OHT assessment in younger patient populations.

O16 Toward a combined DR+DQ HLA molecular mismatch score for risk stratification of pediatric heart transplant patients

O16 Toward a combined DR+DQ HLA molecular mismatch score for risk stratification of pediatric heart transplant patients

Recurrent Mild Acute Rejections and Donor-specific Antibodies as Risk Factors for Cardiac Allograft Vasculopathy in a National Pediatric Heart Transplant Cohort.

Immune-mediated factors such as acute cellular rejections and donor-specific antibodies (DSAs) are risk factors for cardiac allograft vasculopathy (CAV). We studied a national cohort with a unified setting and thorough protocol endomyocardial biopsy (EMB) data for an association between cellular rejections, especially when mild and recurrent, and DSAs with CAV in pediatric heart transplant (HTx) patients. This is a retrospective, national cohort study of 94 pediatric HTxs performed between 1991 and 2019 and followed until December 31, 2020. Diagnosis of CAV was based on reevaluation of angiographies. Protocol and indication EMB findings with other patient data were collected from medical records. Associations between nonimmune and immune-mediated factors and CAV were analyzed with univariable and multivariable Cox regression analyses. Angiographies performed on 76 patients revealed CAV in 23 patients (30%). Altogether 1138 EMBs (92% protocol biopsies) were performed on 78 patients (83%). During the first posttransplant year, grade 1 rejection (G1R) appeared in 45 patients (58%), and recurrent (≥2) G1R findings in 14 patients (18%). Pretransplant DSAs occurred in 13 patients (17%) and posttransplant DSAs in 37 patients (39%). In univariable analysis, pretransplant DSAs, appearance and recurrence of G1R findings, and total rejection score during the first posttransplant year, as well as recurrent G1R during follow-up, were all associated with CAV. In multivariable analysis, pretransplant DSAs and recurrent G1R during the first posttransplant year were found to be associated with CAV. Our results indicate that pretransplant DSA and recurrent G1R findings, especially during the first posttransplant year, are associated with CAV after pediatric HTx.

Risk factors for 1-year allograft loss in pediatric heart transplant patients using machine learning: An analysis of the pediatric heart transplant society database.

Pediatric heart transplant patients are at greatest risk of allograft loss in the first year. We assessed whether machine learning could improve 1-year risk assessment using the Pediatric Heart Transplant Society database. Patients transplanted from 2010 to 2019 were included. The primary outcome was 1-year graft loss free survival. We developed a prediction model using cross-validation, by comparing Cox regression, gradient boosting, and random forests. The modeling strategy with the best discrimination and calibration was applied to fit a final prediction model. We used Shapley additive explanation (SHAP) values to perform variable selection and to estimate effect sizes and importance of individual variables when interpreting the final prediction model. Cumulative incidence of graft loss or mortality was 7.6%. Random forests had favorable discrimination and calibration compared to Cox proportional hazards with a C-statistic (95% confidence interval [CI]) of 0.74 (0.72, 0.76) versus 0.71 (0.69, 0.73), and closer alignment between predicted and observed risk. SHAP values computed using the final prediction model indicated that the diagnosis of congenital heart disease (CHD) increased 1 year predicted risk of graft loss by 1.7 (i.e., from 7.6% to 9.3%), need for mechanical circulatory support increased predicted risk by 2, and single ventricle CHD increased predicted risk by 1.9. These three predictors, respectively, were also estimated to be the most important among the 15 predictors in the final model. Risk prediction models used to facilitate patient selection for pediatric heart transplant can be improved without loss of interpretability using machine learning.