The 2013 International Society for Heart and Lung Transplantation Working Formulation for the standardization of nomenclature in the pathologic diagnosis of antibody-mediated rejection in heart transplantation

Enhanced Costimulation Blockade With αCD154, αCD2, and αCD28 to Promote Heart Allograft Tolerance in Nonhuman Primates

BACKGROUND

Long-term renal allograft acceptance has been achieved in macaques using a transient mixed hematopoetic chimerism protocol, but similar regimens have proven unsuccessful in heart allograft recipients unless a kidney transplant was performed simultaneously. Here, we test whether a modified protocol based on targeting CD154, CD2, and CD28 is sufficient to prolong heart allograft acceptance or promote the expansion of regulatory T cells.

METHODS

Eight macaques underwent heterotopic allo-heart transplantation from major histocompatibility complex-mismatched donors. Induction treatment for donor bone marrow transplantation (BMT) was administered after a 4-mo delay period under TNX-1500 monotherapy. The BMT induction regimen comprised 1 (group 1, G1; n = 3) or 2 (group 2, G2; n = 5) doses of total body irradiation, thymic irradiation, and antithymocyte globulin, followed by 2 (G1) or 5 (G2) weekly doses of αCD2 and 5 weekly treatments with αCD28 and TNX-1500.

RESULTS

During the delay period, 1 G1 graft was rejected and 2 (1 in each group) exhibited moderate rejection on protocol biopsy before BMT. Lymphocyte chimerism was seen in 3 of 5 G2 animals and in 1 of 2 G1 recipients. One G1 graft was rejected despite chimerism, whereas the other recipient succumbed to anti-cytomegalovirus treatment. Two G2 monkeys succumbed due to infection (cytomegalovirus, bacteremia) post-BMT and 3 due to posttransplantation lymphoproliferative disease.

CONCLUSIONS

Intensive costimulation pathway blockade with αCD2, αCD154, and αCD28 promotes lymphocyte chimerism at the cost of high incidence of posttransplantation lymphoproliferative disease and opportunistic infections, preventing assessment of the effectiveness of the regimen to promote alloimmune tolerance.

Correlation between Donor-Derived Cell-free DNA and Tissue Gene Expression in Heart Transplant Patients Undergoing for-cause Endomyocardial Biopsies

INTRODUCTION

The introduction of donor-derived cell-free DNA (dd-cfDNA) and the Molecular Microscope (MMDx) is changing how we diagnose rejection following heart transplantation (HT). This study aims to assess the accuracy of dd-cfDNA in detecting rejection as identified by MMDx and histology, with a focus on determining an optimal dd-cfDNA threshold to improve diagnostic performance.

METHODS

Single-center prospective study of HT recipients undergoing for-cause biopsies with paired MMDx results and dd-cfDNA levels. We employed a Receiver Operator Curve (ROC) to evaluate the performance of dd-cfDNA levels to detect rejection assessed by both histology and MMDx. We also assessed the correlation between dd-cfDNA levels and MMDx rejection scores. A mixed-effects model was applied to account for repeated dependent samples when appropriate.

RESULTS

247 for-cause biopsies were identified with a median of 21 months from HT and a median of 11 days between dd-cfDNA and biopsy. 56.7% of the samples had dd-cfDNA levels ≥0.20%. MMDx identified rejection in 27.1% of biopsies, compared to 7.7% identified by histology. Elevated dd-cfDNA levels were associated with a fourfold increase in rejection rates by MMDx, mainly driven by a fivefold increase in ABMR detection when compared to histology. Dd-cfDNA demonstrated superior performance in predicting rejection by MMDx (AUC of 0.77; optimal cut-off dd-cfDNA value 0.30%). When incorporating a mixed-effects model, the predictive performance improved further, (AUC of 0.89; optimal cut-off value 0.26%). In contrast, prediction based on histology resulted in a lower AUC of 0.64. The correlation between dd-cfDNA levels and MMDx rejection scores was moderate (r=0.51; p<0.001).

CONCLUSIONS

In a for-cause biopsy population, elevated dd-cfDNA levels were more predictive of rejection on MMDx than on histology, suggesting that molecular techniques may detect rejection at earlier stages than traditional histological methods. A dd-cfDNA cutoff of 0.26% provided the highest predictive accuracy for rejection by MMDx when applied within a mixed-effects model for repeated measures.

A two-threshold algorithm using donor-derived cell-free DNA fraction and quantity to detect acute rejection after heart transplantation

Donor-derived cell-free DNA (dd-cfDNA) is a promising biomarker of acute rejection (AR) after heart transplantation (HTx). dd-cfDNA, measured as a fraction of total cfDNA, can be affected by changes in total cfDNA whereas dd-cfDNA quantity can mitigate this impact. This study investigated the performance of a 2-threshold algorithm (2TA) that combines dd-cfDNA fraction (dd-cfDNA%) and donor-quantity score (DQS). A total of 808 plasma samples were prospectively collected for dd-cfDNA testing from 187 adult HTx patients with contemporaneous endomyocardial biopsies. cfDNA was analyzed by a single nucleotide polymorphism-based next-generation sequencing workflow; dd-cfDNA% and DQS were measured using the sequencing reads and single nucleotide polymorphism genotypes. Both dd-cfDNA% and DQS were significantly higher in AR than in non-AR samples (P < 10-14). Considering samples exceeding either dd-cfDNA% = 0.26% or DQS = 18 copies/mL as positive, the 2TA demonstrated 86.5% sensitivity and 83.6% specificity for AR detection and an area under the curve of 0.881. Compared to dd-cfdNA% alone, performance improved with a mean net reclassification index of 16.4% (standard deviation: 4.0%; P = .015) and a 37.3% reduction in the number of the false positive cases compared to the previously established cutoff of 0.15%. Combining dd-cfDNA fraction and quantity estimate in a 2TA may improve AR detection accuracy in HTx recipients compared with dd-cfDNA% alone.

Pathologist interrater reliability and clinical implications of elevated donor-derived cell-free DNA beyond heart transplant rejection, on behalf of the GRAfT investigators

BACKGROUND

There is significant variability among pathologists in the histopathological interpretation of the endomyocardial biopsy (EMB) for acute cellular rejection (ACR), and assessment of variability in the interpretation of antibody-mediated rejection (AMR) has not been reported. In contemporary practice, the strategy of allograft surveillance with donor-derived cell-free DNA (dd-cfDNA) compared to EMB has not been compared with a focus on long-term clinical outcomes beyond acute rejection (AR).

METHODS

The Genomic Research Alliance for Transplantation is a multicenter, prospective cohort study that enrolled patients from 2015 to 2020. The center pathologist read was compared to 2 blinded core cardiac pathologists. ACR and AMR were graded based on the International Society for Heart and Lung Transplantation criteria. Weighted Cohen's kappa (κ) was used to evaluate interrater reliability between the center and core reads. To assess long-term outcomes, we evaluated a composite of AR, allograft dysfunction, and mortality within 1 year.

RESULTS

The study included 94 patients (median age 55 years [interquartile range (IQR) 45, 62]), 30% female sex, 41% Black race), with 429 paired EMBs and dd-cfDNA measures. The concordance rate between center and core pathologists was 77% for ACR (95% confidence interval [CI]: 66%-89%) and 63% for AMR (95% CI: 53%-74%). Forty-six patients had an elevation in dd-cfDNA without AR by EMB. The median dd-cfDNA was 0.49% (IQR: 0.35, 1.01), and subsequent AR, allograft dysfunction, or mortality occurred in 59% of these patients at 1 year. In patients with AR by EMB and negative dd-cfDNA (n = 5), the composite outcome occurred in 20% of patients at 1 year. At baseline, the positive likelihood ratio (LR+) of dd-cfDNA to detect AR by the center pathologist was 3.74 (95% CI 3.01-4.64) and by core pathologist was 2.59 (95% CI: 1.95-3.45). If the composite outcome was included as a true positive, the LR+ of dd-cfDNA improved to 9.82 (95% CI: 7.04-13.69) and 7.63 (95% CI: 5.61-10.38) at 1 year, respectively.

CONCLUSIONS

Pathologists' interrater reliability is limited in AMR similar to what has been reported in ACR. The LR+ of dd-cfDNA when compared with traditional histopathology is limited, but when longitudinal clinical outcomes are included to assess diagnostic performance, the LR+ improves significantly. The value of dd-cfDNA extends beyond the diagnosis of AR to include other clinically meaningful outcomes for patients after heart transplant.

Identification of a novel biomarker of antibody-mediated rejection in heart transplantation: synergistic effect of anti-nuclear antibodies and de novo donor-specific IgG HLA antibodies

Introduction

Humoral autoimmune response may play a significant role in stimulating the alloimmune response, leading to antibody-mediated rejection (ABMR). This study investigated whether the development of IgG de novo donor-specific antibodies (dnDSA) could serve as an independent marker for ABMR diagnosis. Subsequently, we evaluated the synergistic effects of non-HLA anti-nuclear antibodies (ANA) and circulating IgG anti-HLA dnDSA in the development of ABMR.

Methods

This retrospective study included 285 patients who underwent heart transplants between January 2007 to November 2020 at the University of Chicago Medical Center and who had sufficient serum collected at the time of protocol or indication biopsy available for antibody testing.

Results

We observed a 23% incidence of ABMR in heart transplant patients at our center. Kaplan-Meier survival analysis revealed the lowest ABMR free survival in recipients that were positive for both ANA and circulating IgG dnDSA (Log rank p = 2 x 10-16), indicating a synergistic effect of ANA and circulating IgG dnDSA. A univariate stepwise cox proportional hazard model establishes the presence of IgG dnDSA as an independent marker to predict ABMR diagnosis (HR = 8.70, p = 6.15 x 10-9). Similarly, a synergistic effect was found in the presence of a positive ANA titer and IgG dnDSA for ABMR diagnosis in a univariate model (HR = 13.1, p = 2.73 x 10-14). A multivariate stepwise cox proportional hazard model showed an almost seven-fold increased risk for ABMR in patients that have developed IgG dnDSA (HR = 6.96, p = 2.33 x 10-6). Similarly, nearly an eleven-fold enhanced risk for ABMR was found in heart transplant recipients who were positive for ANA and had developed de novo IgG DSA (HR = 10.7, p = 1.25 x 10-10), suggesting the synergistic effect of ANA and IgG dnDSA in ABMR diagnosis.

Discussion

This study establishes circulating IgG dnDSA as an independent biomarker for ABMR diagnosis in heart transplantation and confirms the previously known correlation of IgG dnDSA with ABMR. Subsequently, our data revealed that circulating IgG dnDSA and non-HLA antinuclear antibodies have synergistic effects that cause antibody-mediated rejection in heart transplantation.

Optimizing outcomes in heart transplantation: multidisciplinary Heart Teams and mechanical circulatory support for primary graft dysfunction

Heart transplantation (HTx) is a definitive treatment for selected patients with advanced heart failure. However, primary graft dysfunction (PGD), a severe early complication, is a major cause of post-HTx morbidity and mortality. This paper explores the pathophysiology, diagnostic approaches, and management strategies for PGD, with a particular focus on temporary mechanical circulatory support (MCS) devices such as venoarterial extracorporeal membrane oxygenation and Impella. It also highlights the essential role of the multidisciplinary Heart Team in optimizing outcomes through patient-tailored MCS selection and timely intervention.

Therapeutic plasma exchange is associated with increased survival in heart transplant recipients experiencing severe primary graft dysfunction

BACKGROUND

Primary graft dysfunction (PGD) remains the leading cause of 30-day mortality post-heart transplantation (HTx). HTx recipients experiencing severe PGD have been found to have high levels of circulating proteins associated with PGD occurrence and post-HTx survival. Whether treating these patients with therapeutic plasma exchange (TPE) can attenuate ongoing immunological and inflammatory processes and improve post-transplant outcomes has not been well-investigated. Therefore, we aim to examine the impact of treatment with TPE on 30-day and 1-year clinical outcomes of patients experiencing severe PGD post-HTx.

METHODS

Between 2010 and 2022, we included 42 HTx patients who developed severe PGD. All included patients were placed on veno-arterial extracorporeal membrane oxygenation. We divided these patients into those who received TPE and those who did not (by physician choice). Endpoints included 30-day and 1-year survival, as well as 1-year-freedom from Any-treated rejection (ATR), acute cellular rejection (ACR), antibody-mediated rejection (AMR), biopsy negative rejection (BNR), cardiac allograft vasculopathy (CAV), non-fatal major adverse cardiac events (NF-MACE), and freedom from left ventricular dysfunction (LVD) at 1-year post-HTx.

RESULTS

Compared to patients who did not receive TPE, those managed with TPE had increased survival rates at 30 days (78.1% vs. 40%, p = 0.007) and at 1-year post-HTx (56.25% vs. 30% p = 0.035). However, no statistically significant differences were recorded in other outcomes of interest, including 1-year freedom from CAV, ATR, ACR, AMR, BNR, NF-MACE, or LVD.

CONCLUSION

TPE may serve as a promising therapeutic approach in HTx recipients experiencing severe PGD.

Tracking Acute Rejection in Heart Transplant Recipients by Using Donor-Derived Cell-Free DNA: A Promising Approach

Biomarkers play a crucial role in posttransplant monitoring as they enable early detection of graft dysfunction and rejection, thereby facilitating personalized therapeutic interventions. Although recent studies have demonstrated the potential of donor-derived cell-free DNA in monitoring acute rejection episodes in heart transplant recipients, further investigations are required to enhance its diagnostic accuracy and clinical applicability. Comprehensive clinical trials are warranted to establish standardized threshold values and evaluate the diagnostic utility of donor-derived cell-free DNA in identifying various patterns of allograft injury. A thorough investigation into the molecular mechanisms, clinical applications, and quantification methods of donor-derived cell-free DNA could substantially enhance posttransplant management and patient outcomes.

Donor-Derived Cell-Free DNA Versus Left Ventricular Longitudinal Strain and Strain-Derived Myocardial Work Indices for Identification of Heart Transplant Injury

Background/Objectives: Donor-derived cell-free DNA (dd-cfDNA) is a marker of graft injury that increases in acute rejection and has excellent negative predictive value. Left ventricular global longitudinal strain (LVGLS) and strain-derived myocardial work indices are novel echocardiographic parameters with growing applications. Still, they have been poorly investigated in heart transplant (HTx) recipients so far. We sought to examine the diagnostic impact of left ventricular longitudinal strain-derived indices in diagnosing myocardial injury as assessed by dd-cfDNA after HTx. Methods: Since October 2022, HTx recipients have been shifted from our endomyocardial biopsy (EMB)-based rejection surveillance protocol to a monthly dd-cfDNA-led rejection assessment. We analysed the percentage of donor-derived to total cell-free DNA. For echocardiographic analysis, patient selection was restricted to those transplanted ≥ 6 months. We used 2D speckle-tracking echocardiography to assess LVGLS and strain-derived myocardial work parameters. Results: We analysed four hundred and forty-nine dd-cfDNA samples from seventy-one patients until November 2024. The mean dd-cfDNA fraction remained very low (0.13 ± 0.06%). Eighty-eight percent of surveillance EMBs that would have otherwise been performed were avoided. The mean LVGLS was lower than the literature reference values. We found no correlation between dd-cfDNA and LVGLS. Transplanted hearts had different myocardial work indices than the reference values reported in the literature. Conclusions: dd-cfDNA effectively rules out clinically significant acute rejection and decreases the need for invasive surveillance EMBs. LVGLS seems less sensitive than dd-cfDNA for the identification of myocardial injury in the early stages of HTx rejection in patients at low risk for rejection.

Sex Differences in Incidence and Outcomes of New-Onset Post-Transplant Diabetes Mellitus After Heart Transplantation

INTRODUCTION

Post-transplant diabetes mellitus (PTDM) is a common complication following heart transplantation (HT). The purpose of this study was to investigate sex differences in risk factors for the development of PTDM after HT, as well as in PTDM-related post-transplant outcomes, including acute cellular rejection (ACR), antibody-mediated rejection (AMR), cardiac allograft vasculopathy (CAV), and death.

METHODS

A retrospective review of patients who underwent HT at a large-volume center between January 1, 2010 and December 31, 2019 was performed. PTDM was defined as hemoglobin A1C ≥ 6.5% or a random glucose >200 after HT among patients with no prior history of DM. Predictors of PTDM and post-HT outcomes were analyzed by sex.

RESULTS

A total of 533 patients were transplanted during the study period and screened for inclusion. Among the 317 HT patients without pre-transplant DM, 71 (22.4%) developed PTDM: 24 women (33.7%), 47 men (66.2%). Baseline hypertension (OR 2.9, [1.3, 6.7], p = 0.009) and mean steroid dose over the first 2 years post-transplant (OR 1.2, [1.0, 1.3], p = 0.006) were predictors of PTDM in women but not in men, and mean tacrolimus dose was a predictor in men (OR 1.1, [1.0, 1.2], p = 0.001) but not in women while mean tacrolimus level was a predictor in women (OR 1.2, [1.0, 1.2], p = 0.034) but not in men. Post-transplant outcomes, including ACR, AMR, CAV, and death, did not differ between men with and without PTDM. However, women with PTDM had a higher rate of AMR (38% vs. 18%, p = 0.04) as compared to women without PTDM. There were no significant differences in rates of ACR, CAV, infection requiring hospitalization, or death among women.

CONCLUSION

PTDM is a common complication of HT. Our study suggests that risk factors for PTDM and outcomes among HT patients differ by sex.

Ten-year follow-up after face transplantation-A single-center retrospective cohort study

Face transplantation has emerged as reconstructive option for the most challenging facial deformities. A comprehensive analysis of functional outcomes, medical complications, incidence of malignancy, and chronic rejection in face transplantation recipients over an extended follow-up period has not yet been published leaving a notable gap in the literature. We retrospectively collected data of morbidity, rejection, vasculopathy, metabolic side effects, as well as functional outcome of sensory return, facial motor function, and speech from 9 patients who underwent face transplantation at Brigham and Women's Hospital between 2009 and 2020. The median follow-up was 120 months (54 and 154 months). Four grafts (40%) developed signs of clinical and histopathologic chronic rejection without evidence of vasculopathy on computed tomography angiograms. Sensory return assessed with Weinstein enhanced sensory testing-monofilament showed an increase in 6 patients (66.7%), and facial expression analysis showed improvement throughout the whole cohort at their most recent follow-up. Speech intelligibility was stable or increasing for 5 patients (55.6%). In conclusion, the long-term outcomes reveal promising results in terms of overall graft retention and functional recovery. Metabolic, malignant, and infectious complications, as well as graft rejection episodes, are expected to occur in this population, and some may be related to patient's age and lifestyle.

Microcirculatory Dysfunction and Its Role in Diagnosing Acute Rejection in Pediatric Heart Transplantation: A Pilot Study

Background/Objectives: Acute rejection remains a major challenge in pediatric heart transplantation (HT), with limited tools for early diagnosis. In adult HT recipients, microcirculatory dysfunction, as measured by the index of microcirculatory resistance (IMR), has been identified as a potential biomarker of rejection. However, its role in pediatric populations is largely unexplored. This pilot study aimed to evaluate the association between coronary microcirculatory dysfunction and acute rejection in pediatric heart transplant recipients, as well as its relationship with echocardiographic alterations. Methods: This prospective, single-center study included 10 pediatric HT recipients who underwent routine coronary angiography and endomyocardial biopsy. The IMR, coronary flow reserve (CFR), and fractional flow reserve (FFR) were assessed. Acute rejection was classified as either acute cellular rejection (ACR) or antibody-mediated rejection (AMR) based on ISHLT criteria. Echocardiographic parameters included left ventricular ejection fraction (LVEF), global longitudinal strain (GLS), right ventricular (RV) dysfunction, and diastolic function. Patients were followed for a median of 9.7 months [IQR: 7.0-11.7]. Results: Patients with a history of acute rejection (40%, n = 4) were exclusively found in the IMR ≥ 15 group (66.7%), while no cases were observed in the IMR < 15 group (0%; p = 0.04). During follow-up, only one patient experienced acute rejection, occurring in the IMR ≥ 15 group, although the difference between groups was not statistically significant (p = 0.39). Both LVEF and GLS were worse in patients with IMR ≥ 15 compared to IMR < 15 (62.5% vs. 76.3% and -17.3% vs. -18.8%, respectively), although these differences did not reach statistical significance. No complications were reported during coronary physiology assessment. Conclusions: Microcirculatory dysfunction, as measured by IMR, was significantly associated with a history of acute cellular rejection in pediatric heart transplant recipients. While its predictive value for acute rejection during follow-up remains unclear due to the small sample size, this pilot study highlights the safety and feasibility of coronary physiology assessment in this population. Larger studies are needed to validate these findings and establish pediatric-specific diagnostic thresholds.

Microvascular Resistance Reserve and Prognosis After Heart Transplantation

BACKGROUND

Impaired microcirculatory function after heart transplantation is associated with increased risk for acute cellular rejection. Microvascular resistance reserve (MRR) is a novel index for assessing microcirculatory function, irrespective of epicardial coronary artery stenosis, but it has not been validated in transplanted hearts.

OBJECTIVES

The aim of this study was to investigate the prognostic impact of MRR in heart transplantation.

METHODS

The present study prospectively enrolled 154 heart transplant recipients who underwent scheduled coronary angiography and invasive coronary physiological assessment 1 month after transplantation. Coronary microcirculatory dysfunction was defined as MRR ≤3.0. Elevated microcirculatory resistance was defined as an index of microcirculatory resistance ≥15. The presence of epicardial coronary stenosis was assessed by fractional flow reserve. The primary outcome was a composite of death or biopsy-proven acute cellular rejection of grade ≥ 2R after transplantation.

RESULTS

Among the total patients, 22.1% (34 of 154) had impaired microcirculatory function (MRR ≤3.0), and 77.9% (122 of 154) had preserved microcirculatory function (MRR >3.0). During median follow-up of 730 days (Q1-Q3: 730-730 days), patients with MRR ≤3.0 showed increased risk for a composite of death or acute cellular rejection (adjusted HR: 5.31; 95% CI: 2.65-10.64; P < 0.001), acute cellular rejection (adjusted HR: 4.83; 95% CI: 2.20-10.60; P < 0.001), and death (adjusted HR: 5.19; 95% CI: 1.24-21.62; P = 0.024). MRR was significantly associated with increased risk for death or acute cellular rejection, regardless of epicardial coronary artery stenosis (HR adjusted for fractional flow reserve: 1.89 per 1-U decrease in MRR; 95% CI: 1.46-2.46; P < 0.001) or elevated microcirculatory resistance (HR adjusted for index of microcirculatory resistance: 1.90 per 1-U decrease in MRR; 95% CI: 1.43-2.52; P < 0.001).

CONCLUSIONS

Impaired microcirculatory function, determined by MRR early after heart transplantation, identified patients at high risk for death or acute cellular rejection, regardless of epicardial coronary artery stenosis or elevated microcirculatory resistance. (Physiologic Assessment of Microvascular Function in Heart Transplant Patients; NCT02798731).

Microvascular Inflammation of Kidney Allografts and Clinical Outcomes

BACKGROUND

The heterogeneous clinical presentation of graft microvascular inflammation poses a major challenge to successful kidney transplantation. The effect of microvascular inflammation on allograft outcomes is unclear.

METHODS

We conducted a cohort study that included kidney-transplant recipients from more than 30 transplantation centers in Europe and North America who had undergone allograft biopsy between 2004 and 2023. We integrated clinical and pathological data to classify biopsy specimens according to the 2022 Banff Classification of Renal Allograft Pathology, which includes two new diagnostic categories: probable antibody-mediated rejection and microvascular inflammation without evidence of an antibody-mediated response. We then assessed the association between the newly recognized microvascular inflammation phenotypes and allograft survival and disease progression.

RESULTS

A total of 16,293 kidney-transplant biopsy specimens from 6798 patients were assessed. We identified the newly recognized microvascular inflammation phenotypes in 788 specimens, of which 641 were previously categorized as specimens with no evidence of rejection. As compared with patients without rejection, the hazard ratio for graft loss was 2.1 (95% confidence interval [CI], 1.5 to 3.1) among patients with microvascular inflammation without evidence of an antibody-mediated response and 2.7 (95% CI, 2.2 to 3.3) among patients with antibody-mediated rejection. Patients with a diagnosis of probable antibody-mediated rejection had a higher risk of graft failure beyond year 5 after biopsy than those without rejection (hazard ratio, 1.7; 95% CI, 0.8 to 3.5). Patients with a diagnosis of either newly recognized microvascular inflammation phenotype had a higher risk of progression of transplant glomerulopathy during follow-up than patients without microvascular inflammation.

CONCLUSIONS

Microvascular inflammation in kidney allografts includes distinct phenotypes, with various disease progression and allograft outcomes. Our findings support the clinical use of additional rejection phenotypes to standardize diagnostics for kidney allografts. (Funded by OrganX. ClinicalTrials.gov number, NCT06496269.).

The Relationship Between Genetic Variants at Loci 9p21, 6q25.1, and 2q36.3 and the Development of Cardiac Allograft Vasculopathy in Heart Transplant Patients

BACKGROUND

Cardiac allograft vasculopathy (CAV) is an accelerated form of coronary artery disease (CAD) that is characterized by concentric fibrous intimal hyperplasia along the length of coronary vessels, and is recognized as long-term complication after heart transplantation. The chromosomal loci 9p21, 6q25.1, and 2q36.3, represented by their respective leading variants rs10757274, rs6922269 and rs2943634, have been linked with a history of CAD by genome-wide association studies. We aimed to investigate the associations of genetic variants at the loci 9p21, 6q25.1, and 2q36.3 with CAV as genetic risk factors for early prediction.

METHODS

Genomic DNA was extracted from paired aortic samples of 727 heart recipients (average age 50.8 ± 12.2 years; 21.3% women) and corresponding donors (average age 39.7 ± 12.0 years; 26.1% women). The variants within the loci 9p21, 6q25.1, and 2q36.3 were genotyped using PCR-RFLP.

RESULTS

The recipients' variants of 9p21 (OR 1.97; 95% CI, 1.21-3.19 for GG vs. +A comparison, p = 0.0056) and 2q36.3 (OR 2.46; 95% CI, 1.12-6.17 for +C vs. AA comparison, p = 0.0186) were associated with higher incidence of CAV during the first year following heart transplantation. No such association was found for donor genotypes.

CONCLUSIONS

Our data suggest that variants at the locus 9p21 (rs10757274) and 2q36.3 (rs2943634) are associated with early CAV development.

Surveillance donor-specific antibody and pathologic antibody-mediated rejection testing in heart transplant patients in the contemporary era

BACKGROUND

Surveillance donor-specific antibody (DSA) and pathologic antibody-mediated rejection (pAMR) testing is recommended in the first year after heart transplantation (HTx) in adult patients. Whether pAMR testing adds prognostic information to contemporary DSA testing has not been fully studied.

METHODS

This was a single-center study of consecutive endomyocardial biopsies (EMB) performed between November 2010 and February 2023 in adult HTx patients. The primary objective was to evaluate whether pAMR testing contributes additional information to DSA testing to better predict overall survival. Secondary end-points included cardiac survival and allograft dysfunction.

RESULTS

A total of 6,033 EMBs from 544 HTx patients were reviewed for the study. The pAMR+/DSA+ patients had significantly lower overall (pc = 0.013) and cardiac survival (pc = 0.002), while the pAMR+/DSA- and pAMR-/DSA+ patients showed no difference in either outcome compared to the pAMR-/DSA- group. We found significantly lower overall survival in pAMR+/DSA+ patients with allograft dysfunction (pc < 0.001) but not in pAMR+/DSA+ patients without allograft dysfunction (pc = 0.569), when compared to the pAMR-/DSA- without allograft dysfunction group. The pAMR+/DSA+ patients with cardiac allograft dysfunction accounted for 18% of deaths or cardiac retransplants while only representing 4% of the HTx cohort. Moderate or severe primary graft dysfunction (PGD) also was a novel risk factor for the development of de novo DSAs (dnDSA) by 4 weeks post-HTx (p = 0.025).

CONCLUSIONS

Surveillance DSA testing may effectively identify high-risk pAMR+ patients. Earlier DSA testing at 10 to 14 days post-HTx should also be considered in moderate or severe PGD patients.

Computational pathology assessments of cardiac stromal remodeling: Clinical correlates and prognostic implications in heart transplantation

Background

The hostile immune environment created by allotransplantation can accelerate pathologic tissue remodeling. Both overt and indolent inflammatory insults propel this remodeling, but there is a paucity of tools for monitoring the speed and severity of remodeling over time.

Methods

This retrospective cohort consisted of n = 2,167 digitized heart transplant biopsy slides along with records of prior inflammatory events and future allograft outcomes (cardiac death or allograft vasculopathy). Utilizing computational pathology analysis, biopsy images were analyzed to identify the pathologic stromal changes associated with future allograft loss or vasculopathy. Biopsy images were then analyzed to assess which historical inflammatory events drive progression of these pathologic stromal changes.

Results

The top 5 features of pathologic stromal remodeling most associated with adverse allograft outcomes were also strongly associated with histories of both overt and indolent inflammatory events. Compared to controls, a history of high-grade or treated rejection was significantly associated with progressive pathologic remodeling and future adverse outcomes (32.9% vs 5.1%, p < 0.001). A history of recurrent low-grade rejection and Quilty lesions was also significantly associated with pathologic remodeling and adverse outcomes vs controls (12.7% vs 5.1%, p = 0.047). A history of high-grade or treated rejection in the absence of recurrent low-grade rejection history was not associated with pathologic remodeling or adverse outcomes (7.1% vs 5.1%, p = 0.67).

Conclusions

A history of both traditionally treated and traditionally ignored alloimmune responses can predispose patients to pathologic allograft remodeling and adverse outcomes. Computational pathology analysis of allograft stroma yields translationally relevant biomarkers, identifying accelerated remodeling before adverse outcomes occur.

Data Availability

The data that support the findings of this study are presented in the manuscript and extended data sections. Unprocessed raw data are available from the corresponding author upon reasonable request. Source code for the stromal feature analysis pipeline is hosted on GitHub and freely available: https://github.service.emory.edu/CYUAN31/Pathomics_StromalBioMarker_in_Myocardium.git.

Cardiac allograft tolerance can be achieved in nonhuman primates by donor bone marrow and kidney cotransplantation

Long-term, immunosuppression-free allograft survival has been induced in human and nonhuman primate (NHP) kidney recipients after nonmyeloablative conditioning and donor bone marrow transplantation (DBMT), resulting in transient mixed hematopoietic chimerism. However, the same strategy has consistently failed in NHP heart transplant recipients. Here, we investigated whether long-term heart allograft survival could be achieved by cotransplanting kidneys from the same donor. Cynomolgus monkeys were transplanted with heart allografts alone or heart and kidney allografts from the same major histocompatibility complex (MHC)-mismatched donors. All animals except one received DBMT, either at the same time or after a 2- to 4-month delay, plus short-term costimulation blockade and calcineurin inhibitor treatment. Long-term, immunosuppression-free heart allograft survival was consistently achieved in heart/kidney, but not heart-alone, recipients. This was not associated with greater donor/recipient histocompatibility or altered lymphoid cell reconstitution after conditioning. The maintenance of tolerance after heart/kidney transplantation was associated with the presence of forkhead box P3 (Foxp3+) regulatory T cell (Treg)-rich organized lymphoid structures in kidneys but not hearts. Substituting high-dose erythropoietin treatment for kidney transplantation was unsuccessful, suggesting that it was not the sole mechanism of action. RNA sequencing analysis revealed that gene expression in hearts from tolerant recipients closely resembled that in hearts from chronically immunosuppressed recipients but differed markedly from rejecting allografts and naïve hearts. A version of this protocol may be able to induce tolerance in patients with end-stage heart and kidney failure who require combined heart and kidney transplantation.

Sex and Gender Differences in Face and Upper Extremity Allotransplantation: A Narrative Review of Implications and Impact

Sex and gender differences play a significant role in vascularized composite allotransplantation (VCA), impacting both surgical outcomes and postoperative care. While sex refers to biological distinctions and gender encompasses life experiences and behaviors, both factors are closely interrelated in transplantation. Biological sex differences, such as immune responses, hormonal fluctuations, and anatomical features influence graft adaptation and healing, while both sex and gender-specific factors affect psychological and functional recovery. Studies indicate that men have higher mortality and reoperation rates, whereas women are more susceptible to adverse effects from immunosuppressive therapies. Unlike solid organ transplantation (SOT), which is primarily lifesaving, VCA focuses on life-enhancing outcomes, requiring careful attention to patients' social, psychological, and functional well-being. Lifelong immunosuppression in VCA carries risks, including infections and cancer, complicating patient management. Psychological readiness is crucial for candidate selection and long-term success, with women often expressing greater concerns about outcomes. Although no significant gender differences in functional recovery have been observed, individualized rehabilitation plans based on anatomical and physiological differences remain essential for optimal recovery.

Clinical outcomes after a biopsy diagnosis of antibody-mediated rejection in pediatric heart transplant recipients

BACKGROUND

Extending survival after heart transplant (HT) is of paramount importance for childhood recipients of HT. Acute rejection is a significant event, and biopsy remains the most specific means for distinguishing between cellular (ACR) and antibody-mediated rejection (AMR).

METHODS

All children in the Pediatric Heart Transplant Society Registry who underwent HT between January 2015 and June 2022 and had ≥1 rejection episode were included. Survival was compared between AMR and ACR-only. Secondary outcomes of infection, malignancy, and cardiac allograft vasculopathy (CAV) were assessed. Risk factors for graft loss after AMR were identified using Cox proportional hazard modeling.

RESULTS

Among 906 children with rejection, 697 (77%) with complete biopsy information were included. AMR was present on biopsy in 261 (37%) patients; ACR-only was present in 436 (63%). Time to rejection was earlier for AMR, median time from HT to rejection 0.11 versus 0.29 years, p = 0.0006. Survival after AMR in the 1st year was lower than survival after ACR-only. Predictors of graft loss after AMR were younger age at HT, congenital heart disease, and rejection with hemodynamic compromise. There was no difference in time to CAV, infection, or malignancy after rejection between groups.

CONCLUSIONS

The largest analysis of pediatric HT rejection with biopsy data to identify AMR underscores the continued importance of AMR on survival. AMR is associated with higher graft loss versus ACR when occurring in the first-year post-HT. Predictors of graft loss after AMR identify patients who may benefit from increased surveillance or augmented maintenance immunosuppression.

Multiparametric cardiovascular magnetic resonance is associated with outcomes in pediatric heart transplant recipients

BACKGROUND

Multiparametric cardiovascular magnetic resonance (CMR) has an emerging role in non-invasive surveillance of pediatric heart transplant recipients (PHTR). Higher myocardial T2, higher extracellular volume fraction (ECV), and late gadolinium enhancement (LGE) have been associated with adverse clinical outcomes in adult heart transplant recipients. The purpose of this study was to investigate the prognostic value of CMR-derived T1 and T2 mapping, ECV, and LGE for clinical outcomes in PHTR.

METHODS

We performed a single-center, retrospective chart review of consecutive, gadolinium-enhanced CMR studies in PHTR over a 7.5-year period, excluding follow-up studies. Standard CMR ventricular volume and function analysis, T1 mapping with ECV, T2 mapping, and LGE assessment were performed. The composite outcome included cardiac death, non-cardiac death, re-transplantation, and cardiac hospitalization.

RESULTS

Among 113 PHTR, mean age was 13.0 ± 5.1 years, with 6.0 ± 4.0 years since transplant. The indication for CMR was surveillance in 79%. Mean native T1 was 1050 ± 48 ms, T2 49.2 ± 3.9 ms, and ECV 29.7 ± 4.5%. Left ventricular LGE was present in 37% (42/113) and right ventricular LGE in 3.5% (4/113). The mean follow-up time was 2.3 years and median was 1.4 years. Cardiac death occurred in 2% (2/113), re-transplantation in 4% (4/113), and cardiac hospitalization in 22% (25/113). Non-cardiac death did not occur. Using Kaplan-Meier analysis, high T1 (≥1061 ms), T2 (≥50.0 ms), and ECV (≥31.4%) were each associated with decreased freedom from the composite outcome in follow-up. In univariable Cox regression analyses, high T1 was associated with increased risk of the composite outcome (hazard ratios [HR] 4.0, 95% confidence interval [CI] 1.7-9.2, p = 0.001), as were high T2 (HR 2.8, 95% CI 1.1-7.1, p = 0.026), and high ECV (HR 3.5, 95% CI 1.5-8.1, p = 0.004).

CONCLUSION

T1 and T2 mapping are associated with early differences in adverse cardiac events in PHTR. These data suggest a role for a multicenter study with a longer follow-up duration.

Proteomics in Acute Heart Transplant Rejection, On Behalf of the GRAfT Investigators

BACKGROUND

Proteomic phenotyping can provide insights into rejection pathophysiology, novel biomarkers, and therapeutic targets.

METHODS

Within the prospective, multicenter Genomic Research Alliance for Transplantation study, 181 proteins were evaluated from blood drawn at the time of endomyocardial biopsy; protein fold change, logistic regression, and pathway analyses were conducted, with protein discovery adjusted for a 5% false discovery rate.

RESULTS

Among 104 adult heart transplant patients (31% female sex, 53% Black race, median age 52 y), 74 had no rejection, 18 developed acute cellular rejection (ACR), and 12 developed antibody-mediated rejection (AMR). Differential expression was found in 2 proteins during ACR (inflammatory proteins CXCL10 and CD5) and 73 proteins during AMR. The most abundant AMR proteins were the heart failure biomarkers N-terminal pro-B-type natriuretic peptide and suppression of tumorigenicity 2. In univariate logistic regression, odds of identifying ACR on endomyocardial biopsy increased with doubling of CXCL10 (odds ratio [OR] 2.2 [95% confidence interval (CI), 1.3-3.6]) and CD5 (OR 4.7 [95% CI, 1.7-12.9]) concentrations, and odds of AMR increased with doubling of N-terminal pro-B-type natriuretic peptide (OR 13.0 [95% CI, 2.7-62.7) and suppression of tumorigenicity 2 (OR 4.8 [95% CI, 2.1-10.7]) concentrations. After multivariable analysis with clinical covariates, these proteins showed similar odds of ACR or AMR on biopsy. Pathway analysis identified T cell-receptor signaling and cell differentiation as key pathways in ACR and cardiovascular disease and cell turnover in AMR.

CONCLUSIONS

Proteomic analysis reveals unique biomarkers and biological pathway expression in ACR and AMR. Cardiac injury-associated biomarkers were more pronounced in AMR, whereas inflammatory biomarkers were more pronounced in ACR. Proteomic analysis may provide insights into rejection pathophysiology, detection, and therapy.

Redefining Cardiac Antibody-Mediated Rejection With Donor-Specific Antibodies and Graft Dysfunction

BACKGROUND

Heart transplant recipients with donor-specific antibodies (DSAs) have an increased risk for antibody-mediated rejection. However, many patients with graft dysfunction and DSA do not have evidence of antibody-mediated rejection by endomyocardial biopsy (EMB).

METHODS

Participants from this prospective, multicenter study underwent serial EMB, echocardiogram, DSA, and donor-derived cell-free DNA evaluations. Outcomes were defined as pAMR+ (pAMR≥1) or DSA+/left ventricle (LV) dysfunction (DSA presence+LVEF drop ≥10% to an LVEF≤50%). Cox regression evaluated the association between antibody-mediated rejection categories and death or sustained (for 3 months) reduction of LVEF to <50%.

RESULTS

Two hundred sixteen patients (29% women, 39% Black race, median age 55 [interquartile range, 47-62] years) had 1488 EMB, 2792 DSA, 1821 echocardiograms, and 1190 donor-derived cell-free DNA evaluations. DSAs were present in 86 patients (40%). Fourteen patients had isolated pAMR+ episodes and 8 patients had isolated DSA+/LV dysfunction episodes; 2 patients had pAMR+ and then subsequently DSA+/LV dysfunction with pAMR+. Median %dd-cfDNA was significantly higher at diagnosis of pAMR+ (0.63% [interquartile range, 0.23-2.0]; P=0.0002), or DSA+/LV dysfunction (0.40% [interquartile range, 0.36-1.24]; P<0.0001), compared with patients without these outcomes (0.01% [interquartile range, 0.0001-0.10]). Both pAMR+ and DSA+/LV dysfunction were associated with long-term clinical outcome of death (n=18) or prolonged LV dysfunction (n=10): pAMR+ (hazard ratio, 2.8 [95% CI, 1.03-7.4]; P=0.043); DSA+/LV dysfunction (hazard ratio, 26.2 [95% CI, 9.6-71.3]; P<0.001); composite of both definitions (hazard ratio, 6.5 [95% CI, 2.9-14.3]; P<0.001). Patients who developed pAMR+ or DSA+/LV dysfunction within the first 6 months of transplant were more likely to die within 3 years posttransplant (hazard ratio, 3.9 [95% CI, 1.03-14.6]; P=0.031).

CONCLUSIONS

Expanding the characterization of antibody-mediated rejection to include patients with DSA and concurrent allograft dysfunction identified DSA+ patients at risk for death and prolonged LV dysfunction.

Angiotensin II Type-1 Receptor Antibody in Solid Organ Transplantation - Is It Time to Test?

Angiotensin II type-1 receptor antibody (AT1R-Ab) has been mooted as a potential effector of both acute and chronic antibody mediated rejection (AMR). A growing body of literature on the topic is now coming under scrutiny in the context of the evolving Banff AMR diagnostic classification system and refinement of recommendations for histocompatibility testing by the Sensitization in Transplantation Assessment of Risk (STAR) workgroup. This mini-review discusses the latest understanding of pathophysiological mechanisms, clinical evidence for the pathogenicity of AT1R-Ab, and methods of laboratory testing.

Longitudinal Assessment of T1 Mapping Trends Disease in Pediatric Patients With Heart Transplant

BACKGROUND

Surveillance for heart transplant rejection by endomyocardial biopsy is invasive and may yield false negatives. T1 and T2 mapping from cardiac magnetic resonance can demonstrate elevations with rejection. We sought to evaluate longitudinal changes in T1 and T2 mapping in pediatric patients with heart transplant.

METHODS AND RESULTS

A cohort study was performed of pediatric patients with heart transplant who underwent concurrent endomyocardial biopsy and cardiac magnetic resonance with T1 and T2 mapping from December 2019 to July 2024. Segmental values were measured and subsegmental elevations (ie, hotspots) were identified. Subjects were categorized as either treated rejection or no rejection. Peak and mean T1 and T2 values and number of hotspots at/between each time point for patient dyads were compared between the groups. A total of 21 subjects (7 treated rejection, 14 no rejection) with 68 total encounters met inclusion criteria. Peak and mean T1 values were higher in treated rejection patients during the rejection period and decreased with treatment (peak, 1086 versus 1052; mean, 1028 versus 1021), such that at last follow-up when their rejection had resolved, there was no significant difference in values when compared with no rejection patients (peak, 1066; mean, 1016). The number of T1 hotspots decreased after rejection treatment (2 versus 1). There were no changes in peak or mean T2 values in the treated rejection group despite treatment, and peak and mean T2 values were similar to patients with no rejection through last follow-up.

CONCLUSIONS

Elevated T1 values and hotspots observed during cardiac allograft rejection decline in response to treatment. Cardiac magnetic resonance may serve as a noninvasive monitoring tool for the development and resolution of rejection, as well as the effectiveness of rejection therapy.

Terbutaline for Management of Relative Bradycardia Post-Orthotopic Heart Transplant: A Single Center Experience

BACKGROUND

Vagal nerve denervation during the heart transplant procedure results in higher resting heart rates in these recipients compared to the general population. Relative bradycardia (RB) is a common and often temporary post-operative complication that can be managed with agents like terbutaline; however, little data exist on the efficacy, safety, and necessity of long-term terbutaline use post-heart transplant.

METHODS

This was a single-center, retrospective, descriptive study conducted at a large academic medical center investigating oral terbutaline use for RB management in heart transplant recipients. Outcomes included time to and reason for terbutaline discontinuation post-transplant, adverse event rates, and permanent pacemaker (PPM) placement rates.

RESULTS

In the 229 patients included, the median (IQR) time to terbutaline initiation was 8 (5, 12) days post-heart transplant, with a median (IQR) time to discontinuation of 56 (20, 96) days from the first dose. In most cases, terbutaline was successfully tapered off outpatient due to the resolution of RB. Tachyarrhythmias occurred in 29 (12.7%) patients without long-term sequelae. At 3 months post-transplant, PPM had been placed for chronotropic support in 15 patients (6.6%) with a median time (IQR) to PPM placement of 24 (19, 77) days from transplant.

CONCLUSION

This study's overall low PPM placement rate suggests that early sinus node dysfunction can be treated with pharmacotherapy without committing to a permanent device, and that terbutaline can be used safely in early post-heart transplant recipients. If patients require long-term chronotropic support, the risk-benefit of PPM placement versus continued terbutaline should be considered.

Association Between High Sensitivity Troponin I and NTproBNP With Rejection and Graft Loss in Pediatric Heart Transplant Recipients

BACKGROUND

Troponin I is a blood biomarker of cardiac injury and levels measured using a high-sensitivity assay after pediatric heart transplantation (HT) have not been described. We sought to assess the association between high-sensitivity troponin I (hsTnI) and N-terminal pro-B-type natriuretic peptide (NTproBNP) with treated acute rejection (AR) and graft loss in pediatric heart transplant (HT) recipients.

METHODS

Serum was collected and banked from pediatric HT recipients prior to cardiac catheterization. Patients with samples drawn within 365 days post-HT were included and followed for up to 5 years. Generalized linear mixed-effect models examined the association between hsTnI and treated AR using a random intercept per patient. Cox proportional hazards models tested the association between maximal hsTnI and NT-proBNP and death/graft loss.

RESULTS

HsTnI and NTproBNP values decline in the weeks following HT, after which these biomarkers stabilize. HsTnI was higher in AR versus no AR (6.2 vs. 3.5 ng/L, p < 0.001); doubling of hsTnI increased the odds of AR by 33% (p = 0.004). HsTnI showed moderate discrimination for AR with an AUC of 0.811 (95% CI 0.76, 0.87) and a NPV of 96.4% (95% CI 93.0, 98.1). Elevation in NT-proBNP was not associated with AR. In multivariable Cox modeling, a doubling of maximal NT-proBNP was associated with graft loss (HR 8.96, p = 0.014).

CONCLUSIONS

In this pediatric HT cohort, HsTnI was moderately discriminative for AR and higher maximal NT-proBNP was associated with graft loss. HsTnI may add value in pediatric HT non-invasive AR surveillance, and elevated NTproBNP could suggest an increased risk of graft loss.

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.

Socioeconomic Status and Major Adverse Transplant Events in Pediatric Heart Transplant Recipients

Importance

Low socioeconomic status (SES) has been associated with higher risk of rejection and graft loss in pediatric heart transplant (HT) recipients. The association of SES with other posttransplant morbidities is unknown.

Objective

To assess whether low SES is associated with higher risk of a major adverse transplant event (MATE) among pediatric HT recipients.

Design, Setting, and Participants

Retrospective single-center cohort study at a children's hospital in Boston with consecutive primary HT recipients from 2006 to 2019 and follow-up through 2022. Data were analyzed from June 2023 to March 2024.

Exposure

Very low or low, moderate, and high or very high Childhood Opportunity Index (COI) for neighborhood (census tract) of patient residence.

Main Outcomes and Measures

Primary outcome was 3-year MATE-6 score assessed in 6-month survivors as cumulative burden of acute cellular rejection, antibody-mediated rejection, coronary vasculopathy, lymphoproliferative disease, kidney dysfunction, and infection, each as an ordinal score from 0 to 4 (24 for death or retransplant). Secondary outcomes were freedom from rejection during first 6 months, freedom from death or retransplant, MATE-3 score for events 1 to 3 (under immune suppression) and events 4 to 6 (chronic immune suppression effects), and each MATE component.

Results

Of 153 children analyzed, the median (IQR) age at HT was 7.2 (1.5-14.8) years, 99 (65%) were male, 16 (10%) were Black, 17 (11%) were Hispanic, and 106 (69%) were White. Fifty patients (33%) lived in very low or low, 17 (11%) in moderate, and 86 (56%) in high or very high COI neighborhoods. There was no significant group difference in mean (SD) 3-year MATE-6 score (very low or low COI, 3.4 [6.5]; moderate COI, 2.4 [6.3]; and high or very high COI, 4.0 [6.9]). Furthermore, there was no group difference in mean (SD) MATE-3 scores for underimmune suppression (very low or low COI, 1.9 [3.5]; moderate COI, 1.2 [3.2]; and high or very high COI, 2.2 [3.6]), chronic immune suppression effects (very low or low COI, 1.6 [3.3]; moderate COI, 1.1 [3.2]; and high or very high COI, 1.8 [3.6]), individual MATE components, rejection during the first 6 months, or death or retransplant.

Conclusions and relevance

In this cohort study of pediatric HT recipients, there was no difference in posttransplant outcomes among recipients stratified by SES, a notable improvement from prior studies. These findings may be explained by state-level health reform, standardized posttransplant care, and early awareness of outcome disparities.

Donor-Specific Antibody Testing is an Effective Surveillance Strategy for High-Risk Antibody Mediated Rejection in Heart Transplant Patients in the Contemporary Era

Background

Pathologic antibody mediated rejection (pAMR) evaluation and donor specific antibody (DSA) testing are recommended in the first year after heart transplantation (HTx) in adult patients. Whether DSA testing adds prognostic information to contemporary pAMR surveillance has not been fully studied.

Methods

This was a single center study of consecutive endomyocardial biopsies (EMB) performed between November 2010 and February 2023 in adult HTx patients. The primary objective was to evaluate whether DSA testing contributes additional information to pAMR surveillance to better predict overall survival. Secondary endpoints included cardiac allograft dysfunction and loss.

Results

A total of 6,033 EMBs from 544 HTx patients were reviewed for the study. The pAMR+/DSA+ group had significantly lower overall survival versus the pAMR-/DSA- group (hazard ratio [HR] = 2.63; 95% confidence interval [CI], 1.35-5.11; pc = 0.013). In the pAMR+/DSA+ group, patients with cardiac allograft dysfunction, compared to those without allograft dysfunction, had significantly lower overall and cardiac survival (pc < 0.001 for both). In contrast, pAMR+/DSA+ and pAMR-/DSA- patients without cardiac allograft dysfunction showed no difference in overall and cardiac survival. Primary graft dysfunction (PGD) was a novel risk factor for development of de novo DSAs (dnDSA) three weeks post-HTx (p = 0.007).

Conclusions

DSA testing as the primary surveillance method can identify high-risk pAMR+/DSA+ patients. Surveillance pAMR testing in the contemporary era may need to be reevaluated. Earlier DSA testing at 10-14 days post-HTx should be considered in PGD patients.

A machine learning algorithm improves the diagnostic accuracy of the histologic component of antibody mediated rejection (AMR-H) in cardiac transplant endomyocardial biopsies

BACKGROUND

Pathologic antibody mediated rejection (pAMR) remains a major driver of graft failure in cardiac transplant patients. The endomyocardial biopsy remains the primary diagnostic tool but presents with challenges, particularly in distinguishing the histologic component (pAMR-H) defined by 1) intravascular macrophage accumulation in capillaries and 2) activated endothelial cells that expand the cytoplasm to narrow or occlude the vascular lumen. Frequently, pAMR-H is difficult to distinguish from acute cellular rejection (ACR) and healing injury. With the advent of digital slide scanning and advances in machine deep learning, artificial intelligence technology is widely under investigation in the areas of oncologic pathology, but in its infancy in transplant pathology. For the first time, we determined if a machine learning algorithm could distinguish pAMR-H from normal myocardium, healing injury and ACR.

MATERIALS AND METHODS

A total of 4,212 annotations (1,053 regions of normal, 1,053 pAMR-H, 1,053 healing injury and 1,053 ACR) were completed from 300 hematoxylin and eosin slides scanned using a Leica Aperio GT450 digital whole slide scanner at 40X magnification. All regions of pAMR-H were annotated from patients confirmed with a previous diagnosis of pAMR2 (>50% positive C4d immunofluorescence and/or >10% CD68 positive intravascular macrophages). Annotations were imported into a Python 3.7 development environment using the OpenSlide™ package and a convolutional neural network approach utilizing transfer learning was performed.

RESULTS

The machine learning algorithm showed 98% overall validation accuracy and pAMR-H was correctly distinguished from specific categories with the following accuracies: normal myocardium (99.2%), healing injury (99.5%) and ACR (99.5%).

CONCLUSION

Our novel deep learning algorithm can reach acceptable, and possibly surpass, performance of current diagnostic standards of identifying pAMR-H. Such a tool may serve as an adjunct diagnostic aid for improving the pathologist's accuracy and reproducibility, especially in difficult cases with high inter-observer variability. This is one of the first studies that provides evidence that an artificial intelligence machine learning algorithm can be trained and validated to diagnose pAMR-H in cardiac transplant patients. Ongoing studies include multi-institutional verification testing to ensure generalizability.

Heart Transplant Rejection: From the Endomyocardial Biopsy to Gene Expression Profiling

Heart transplant prolongs life for patients with end-stage heart failure but rejection remains a complication that reduces long-term survival. The aim is to provide a comprehensive overview of the current status in HT rejection. EMB is an invasive diagnostic tool, consisting in the sampling of a fragment of myocardial tissue from the right ventricular septum using fluoroscopic guidance. This tissue can later be subjected to histopathological, immunohistochemical or molecular analysis, providing valuable information for cardiac allograft rejection, but this procedure is not without complications. To increase the accuracy of the rejection diagnosis, EMB requires a systematic evaluation of endocardium, myocardium, interstitium and intramural vessels. There are three types of rejection: hyperacute, acute or chronic, diagnosed by the histopathological evaluation of EMB as well as by new diagnostic methods such as DSA, ddcfDNA and gene expression profiling, the last having a high negative predictive value. More than 50 years after the introduction of EMB in medical practice, it still remains the "gold standard" in monitoring rejection in HT recipients but other new, less invasive diagnostic methods reduce the number of EMBs required.

Redefining the molecular rejection states in 3230 heart transplant biopsies: Relationships to parenchymal injury and graft survival

The first-generation Molecular Microscope (MMDx) system for heart transplant endomyocardial biopsies used expression of rejection-associated transcripts (RATs) to diagnose not only T cell-mediated rejection (TCMR) and antibody-mediated rejection (ABMR) but also acute injury. However, the ideal system should detect rejection without being influenced by injury, to permit analysis of the relationship between rejection and parenchymal injury. To achieve this, we developed a new rejection classification in an expanded cohort of 3230 biopsies: 1641 from INTERHEART (ClinicalTrials.gov NCT02670408), plus 1589 service biopsies added to improve the power of the machine learning algorithms. The new system used 6 rejection classifiers instead of RATs and generated 7 rejection archetypes: No rejection, 48%; Minor, 24%; TCMR1, 2.3%; TCMR2, 2.7%; TCMR/mixed, 2.7%; early-stage ABMR, 3.9%; and fully developed ABMR, 16%. Using rejection classifiers eliminated cross-reactions with acute injury, permitting separate assessment of rejection and injury. TCMR was associated with severe-recent injury and late atrophy-fibrosis and rarely had normal parenchyma. ABMR was better tolerated, seldom producing severe injury, but in later biopsies was often associated with atrophy-fibrosis, indicating long-term risk. Graft survival and left ventricular ejection fraction were reduced not only in hearts with TCMR but also in hearts with severe-recent injury and atrophy-fibrosis, even without rejection.

Four decades of progress in heart-lung transplantation: Two hundred seventy-one cases at a single institution

OBJECTIVE

The objective of this study is to evaluate survival for combined heart-lung transplant (HLTx) recipients across 4 decades at a single institution. We aim to summarize our contemporary practice based on more than 271 HLTx procedures over 40 years.

METHODS

Data were collected from a departmental database and the United Network for Organ Sharing. Recipients younger than age 18 years, those undergoing redo HLTx, or triple-organ system transplantation were excluded, leaving 271 patients for analysis. The pioneering era was defined by date of transplant between 1981 and 2000 (n = 155), and the modern era between 2001 and 2022 (n = 116). Survival analysis was performed using cardinality matching of populations based on donor and recipient age, donor and recipient sex, ischemic time, and sex matching.

RESULTS

Between 1981 and 2022, 271 HLTx were performed at a single institution. Recipients in the modern era were older (age 42 vs 34 y; P < .001) and had shorter waitlist times (78 vs 234 days; P < .001). Allografts from female donors were more common in the modern era (59% vs 39%; P = .002). In the matched survival analysis, 30-day survival (97% vs 84%; P = .005), 1-year survival (89% vs 77%; P = .041), and 10-year survival (53% vs 26%; P = .012) significantly improved in the modern era relative to the pioneering era, respectively.

CONCLUSIONS

Long-term survival in HLTx is achievable with institutional experience and may continue to improve in the coming decades. Advances in mechanical circulatory support, improved maintenance immunosuppression, and early recognition and management of acute complications such as primary graft dysfunction and acute rejection have dramatically improved the prognosis for recipients of HLTx in our contemporary institutional experience.

Caveats in Interpretation of Molecular Diagnostics in Heart Allografts

Histologic separation of injury, T cell-mediated rejection, or antibody-mediated rejection in allograft heart biopsies is difficult. A critical review of publications was performed to evaluate the caveats of using molecular diagnostics (MDX) to distinguish between these entities. Typically, only 1 to 2 fragments of unknown histologic appearance are evaluated. Archetype and molecular classifier analyses use gene lists derived from histologic labels and associated reproducibility issues influence the accuracy of the derived MDX classes. Archetypes A1, A2, and A3 archetypes created by bioinformatics were renamed no rejection, T cell-mediated rejection, and antibody-mediated rejection despite as little as 40% concordance with histologic diagnoses and overlapping archetype scores. Additional archetypes S4 and minor injury were created using arbitrary cutoffs based on visual examination of principal component analysis plots. Therapeutic implications of the numerous discrepancies with histology remain unexplored. Many MDX-derived observations are ambiguous and open to alternate logical explanations. Better molecular methods and more rigorous validation studies are needed to advance the field. Ideally, these methods should analyze all available biopsy fragments to minimize sampling issues. It is also desirable to incorporate spatial transcriptomics into the workflow, so that gene expression data can be directly compared with the underlying histology lesions.

Pseudomonas aeruginosa infection correlates with high MFI donor-specific antibody development following lung transplantation with consequential graft loss and shortened CLAD-free survival

BACKGROUND

Donor-specific antibodies (DSAs) are common following lung transplantation (LuTx), yet their role in graft damage is inconclusive. Mean fluorescent intensity (MFI) is the main read-out of DSA diagnostics; however its value is often disregarded when analyzing unwanted post-transplant outcomes such as graft loss or chronic lung allograft dysfunction (CLAD). Here we aim to evaluate an MFI stratification method in these outcomes.

METHODS

A cohort of 87 LuTx recipients has been analyzed, in which a cutoff of 8000 MFI has been determined for high MFI based on clinically relevant data. Accordingly, recipients were divided into DSA-negative, DSA-low and DSA-high subgroups. Both graft survival and CLAD-free survival were evaluated. Among factors that may contribute to DSA development we analyzed Pseudomonas aeruginosa (P. aeruginosa) infection in bronchoalveolar lavage (BAL) specimens.

RESULTS

High MFI DSAs contributed to clinical antibody-mediated rejection (AMR) and were associated with significantly worse graft (HR: 5.77, p < 0.0001) and CLAD-free survival (HR: 6.47, p = 0.019) compared to low or negative MFI DSA levels. Analysis of BAL specimens revealed a strong correlation between DSA status, P. aeruginosa infection and BAL neutrophilia. DSA-high status and clinical AMR were both independent prognosticators for decreased graft and CLAD-free survival in our multivariate Cox-regression models, whereas BAL neutrophilia was associated with worse graft survival.

CONCLUSIONS

P. aeruginosa infection rates are elevated in recipients with a strong DSA response. Our results indicate that the simultaneous interpretation of MFI values and BAL neutrophilia is a feasible approach for risk evaluation and may help clinicians when to initiate DSA desensitization therapy, as early intervention could improve prognosis.

Relationship between donor-derived cell-free DNA and tissue-based rejection-related transcripts in heart transplantation

BACKGROUND

Endomyocardial biopsy (EMB)-based traditional microscopy remains the gold standard for the detection of cardiac allograft rejection, despite its limitation of inherent subjectivity leading to inter-reader variability. Alternative techniques now exist to surveil for allograft injury and classify rejection. Donor-derived cell-free DNA (dd-cfDNA) testing is now a validated blood-based assay used to surveil for allograft injury. The molecular microscope diagnostic system (MMDx) utilizes intragraft rejection-associated transcripts (RATs) to classify allograft rejection and identify injury. The use of dd-cfDNA and MMDx together provides objective molecular insight into allograft injury and rejection. The aim of this study was to measure the diagnostic agreement between dd-cfDNA and MMDx and assess the relationship between dd-cfDNA and MMDx-derived RATs, which may provide further insight into the pathophysiology of allograft rejection and injury.

METHODS

This is a retrospective observational study of 156 EMB evaluated with traditional microscopy and MMDx. All samples were paired with dd-cfDNA from peripheral blood before EMB (up to 9 days). Diagnostic agreement between traditional histopathology, MMDx, and dd-cfDNA (threshold of 0.20%) was compared for assessment of allograft injury. In addition, the relationship between dd-cfDNA and individual RAT expression levels from MMDx was evaluated.

RESULTS

MMDx characterized allograft tissue as no rejection (62.8%), antibody-mediated rejection (ABMR) (26.9%), T-cell-mediated rejection (TCMR) (5.8%), and mixed ABMR/TCMR (4.5%). For the diagnosis of any type of rejection (TCMR, ABMR, and mixed rejection), there was substantial agreement between MMDx and dd-cfDNA (76.3% agreement). All transcript clusters (group of gene sets designated by MMDx) and individual transcripts considered abnormal from MMDx had significantly elevated dd-cfDNA. In addition, a positive correlation between dd-cfDNA levels and certain MMDx-derived RATs was observed. Tissue transcript clusters were correlated with dd-cfDNA scores, including DSAST, GRIT, HT1, QCMAT, and S4. For individual transcripts, tissue ROBO4 was significantly correlated with dd-cfDNA in both nonrejection and rejection as assessed by MMDx.

CONCLUSIONS

Collectively, we have shown substantial diagnostic agreement between dd-cfDNA and MMDx. Furthermore, based on the findings presented, we postulate a common pathway between the release of dd-cfDNA and expression of ROBO4 (a vascular endothelial-specific gene that stabilizes the vasculature) in the setting of antibody-mediated rejection, which may provide a mechanistic rationale for observed elevations in dd-cfDNA in AMR, compared to acute cellular rejection.

Spatial multiomics of arterial regions from cardiac allograft vasculopathy rejected grafts reveal novel insights into the pathogenesis of chronic antibody-mediated rejection

Cardiac allograft vasculopathy (CAV) causes late graft failure and mortality after heart transplantation. Donor-specific antibodies (DSAs) lead to chronic endothelial cell injury, inflammation, and arterial intimal thickening. In this study, GeoMx digital spatial profiling was used to analyze arterial areas of interest (AOIs) from CAV+DSA+ rejected cardiac allografts (N = 3; 22 AOIs total). AOIs were categorized based on CAV neointimal thickening and underwent whole transcriptome and protein profiling. By comparing our transcriptomic data with that of healthy control vessels of rapid autopsy myocardial tissue, we pinpointed specific pathways and transcripts indicative of heightened inflammatory profiles in CAV lesions. Moreover, we identified protein and transcriptomic signatures distinguishing CAV lesions exhibiting low and high neointimal lesions. AOIs with low neointima showed increased markers for activated inflammatory infiltrates, endothelial cell activation transcripts, and gene modules involved in metalloproteinase activation and TP53 regulation of caspases. Inflammatory and apoptotic proteins correlated with inflammatory modules in low neointima AOIs. High neointima AOIs exhibited elevated TGFβ-regulated transcripts and modules enriched for platelet activation/aggregation. Proteins associated with growth factors/survival correlated with modules enriched for proliferation/repair in high neointima AOIs. Our findings reveal novel insight into immunological mechanisms mediating CAV pathogenesis.

Clinical Utility of the Molecular Microscope Diagnostic System in a Real-World Transplant Cohort: Moving Towards a New Paradigm

Objectives

To evaluate the clinical implications of adjunctive molecular gene expression analysis (MMDx ) of biopsy specimens in heart transplant (HT ) recipients with suspected rejection.

Introduction

Histopathological evaluation remains the standard method for rejection diagnosis in HT. However, the wide interobserver variability combined with a relatively common incidence of "biopsy-negative" rejection has raised concerns about the likelihood of false-negative results. MMDx, which uses gene expression to detect early signs of rejection, is a promising test to further refine the assessment of HT rejection.

Methods

Single-center prospective study of 418 consecutive for-cause endomyocardial biopsies performed between November 2022 and May 2024. Each biopsy was graded based on histology and assessed for rejection patterns using MMDx. MMDx results were deemed positive if borderline or definitive rejection was present. The impact of MMDx results on clinical management was evaluated. Primary outcomes were 1-year survival and graft dysfunction following MMDx-guided clinical management. Secondary outcomes included changes in donor-specific antibodies, MMDx gene transcripts, and donor-derived cell-free DNA (dd-cfDNA) levels.

Results

We analyzed 418 molecular samples from 237 unique patients. Histology identified rejection in 32 cases (7.7%), while MMDx identified rejection in 95 cases (22.7%). Notably, in 79 of the 95 cases where MMDx identified rejection, histology results were negative, with the majority of these cases being antibody-mediated rejection (62.1%). Samples with rejection on MMDx were more likely to show a combined elevation of dd-cfDNA and peripheral blood gene expression profiling than those with borderline or negative MMDx results (36.7% vs 28.0% vs 10.3%; p<0.001). MMDx results led to the implementation of specific antirejection protocols or changes in immunosuppression in 20.4% of cases, and in 73.4% of cases where histology was negative and MMDx showed rejection. 1-year survival was better in the positive MMDx group where clinical management was guided by MMDx results (87.0% vs 78.6%; log rank p=0.0017).

Conclusions

In our cohort, MMDx results more frequently indicated rejection than histology, often leading to the initiation of antirejection treatment. Intervention guided by positive MMDx results was associated with improved outcomes.

Graphical abstract

Cardiac magnetic resonance imaging in heart transplant recipients with biopsy-negative graft dysfunction

AIMS

Graft dysfunction (GD) after heart transplantation (HTx) can develop without evidence of cell- or antibody-mediated rejection. Cardiac magnetic resonance imaging (CMR) has an evolving role in detecting rejection; however, its role in biopsy-negative GD has not been described. This study examines CMR findings, evaluates outcomes based on CMR results, and seeks to identify the possibility of rejection missed through endomyocardial biopsy by using CMR in HTx recipients with biopsy-negative GD.

METHODS AND RESULTS

HTx recipients with GD [defined as a decrease in left ventricular ejection fraction (LVEF) by >5% and LVEF < 50%] in the absence of rejection by biopsy or allograft vasculopathy and who underwent CMR were included in the study. The primary outcome was a composite of all-cause mortality, re-transplantation, or persistent LVEF < 50%. Overall, 34 HTx recipients developed biopsy-negative GD and underwent CMR. Left ventricular late gadolinium enhancement (LGE) on CMR was observed in 16 patients with two distinct patterns: diffuse epicardial (n = 13) and patchy (n = 3) patterns. Patients with LGE developed GD later after HTx [4 (1.4-6.8) vs. 0.8 (0.3-1.2) years, P < 0.001], were more often symptomatic (88% vs. 56%, P = 0.06), and had greater haemodynamic derangement (pulmonary capillary wedge pressure: 19 ± 7 vs. 13 ± 3 mmHg, P = 0.002) as compared with those without LGE. No significant difference was observed in the primary composite outcome between patients with LGE and those without LGE (50% vs. 38% of patients with events, P = 0.515). During a median follow-up of 3.8 years, mean LVEF improved similarly in the LGE-negative (37-55%) and LGE-positive groups (32-55%) (P = 0.16).

CONCLUSIONS

Biopsy-negative GD occurs with and without LGE when assessed by CMR, indicative of possible rejection/inflammation occurring only in a subset of patients. Irrespective of LGE, LVEF improvement occurs in most GD patients, suggesting that other neurohormonal or immunomodulatory mechanisms may also contribute to GD development.

Impacts of Pre-transplant Panel-Reactive Antibody on Post-transplantation Outcomes: A Study of Nationwide Heart Transplant Registry Data

BACKGROUND AND OBJECTIVES

The number of sensitized heart failure patients on waiting lists for heart transplantation (HTx) is increasing. Using the Korean Organ Transplantation Registry (KOTRY), a nationwide multicenter database, we investigated the prevalence and clinical impact of calculated panel-reactive antibody (cPRA) in patients undergoing HTx.

METHODS

We retrospectively reviewed 813 patients who underwent HTx between 2014 and 2021. Patients were grouped according to peak PRA level as group A: patients with cPRA ≤10% (n= 492); group B: patients with cPRA >10%, <50% (n=160); group C patients with cPRA ≥50% (n=161). Post-HTx outcomes were freedom from antibody-mediated rejection (AMR), acute cellular rejection, coronary allograft vasculopathy, and all-cause mortality.

RESULTS

The median follow-up duration was 44 (19-72) months. Female sex, re-transplantation, and pre-HTx renal replacement therapy were independently associated with an increased risk of sensitization (cPRA ≥50%). Group C patients were more likely to have longer hospital stays and to use anti-thymocyte globulin as an induction agent compared to groups A and B. Significantly more patients in group C had positive flow cytometric crossmatch and had a higher incidence of preformed donor-specific antibody (DSA) compared to groups A and B. During follow-up, group C had a significantly higher rate of AMR, but the overall survival rate was comparable to that of groups A and B. In a subgroup analysis of group C, post-transplant survival was comparable despite higher preformed DSA in a desensitized group compared to the non-desensitized group.

CONCLUSIONS

Patients with cPRA ≥50% had significantly higher incidence of preformed DSA and lower freedom from AMR, but post-HTx survival rates were similar to those with cPRA <50%. Our findings suggest that sensitized patients can attain comparable post-transplant survival to non-sensitized patients when treated with optimal desensitization treatment and therapeutic intervention.

Cardiac PET Myocardial Blood Flow Quantification Assessment of Early Cardiac Allograft Vasculopathy

BACKGROUND

Positron emission tomography (PET) has demonstrated utility for diagnostic and prognostic assessment of cardiac allograft vasculopathy (CAV) but has not been evaluated in the first year after transplant.

OBJECTIVES

The authors sought to evaluate CAV at 1 year by PET myocardial blood flow (MBF) quantification.

METHODS

Adults at 2 institutions enrolled between January 2018 and March 2021 underwent prospective 3-month (baseline) and 12-month (follow-up) post-transplant PET, endomyocardial biopsy, and intravascular ultrasound examination. Epicardial CAV was assessed by intravascular ultrasound percent intimal volume (PIV) and microvascular CAV by endomyocardial biopsy.

RESULTS

A total of 136 PET studies from 74 patients were analyzed. At 12 months, median PIV increased 5.6% (95% CI: 3.6%-7.1%) with no change in microvascular CAV incidence (baseline: 31% vs follow-up: 38%; P = 0.406) and persistent microvascular disease in 13% of patients. Median capillary density increased 30 capillaries/mm2 (95% CI: -6 to 79 capillaries/mm2). PET myocardial flow reserve (2.5 ± 0.7 vs 2.9 ± 0.8; P = 0.001) and stress MBF (2.7 ± 0.6 vs 2.9 ± 0.6; P = 0.008) increased, and coronary vascular resistance (CVR) (49 ± 13 vs 47 ± 11; P = 0.214) was unchanged. At 12 months, PET and PIV had modest correlation (stress MBF: r = -0.35; CVR: r = 0.33), with lower stress MBF and higher CVR across increasing PIV tertiles (all P < 0.05). Receiver-operating characteristic curves for CAV defined by upper-tertile PIV showed areas under the curve of 0.74 for stress MBF and 0.73 for CVR.

CONCLUSIONS

The 1-year post-transplant PET MBF is associated with epicardial CAV, supporting potential use for early noninvasive CAV assessment. (Early Post Transplant Cardiac Allograft Vasculopahty [ECAV]; NCT03217786).

Computational Pathology Assessments of Cardiac Stromal Remodeling: Clinical Correlates and Prognostic Implications in Heart Transplantation

Both overt and indolent inflammatory insults in heart transplantation can accelerate pathologic cardiac remodeling, but there are few tools for monitoring the speed and severity of remodeling over time. To address this need, we developed an automated computational pathology system to measure pathologic remodeling in transplant biopsy samples in a large, retrospective cohort of n=2167 digitized heart transplant biopsy slides. Biopsy images were analyzed to identify the pathologic stromal changes associated with future allograft loss or advanced allograft vasculopathy. Biopsy images were then analyzed to assess which historical allo-inflammatory events drive progression of these pathologic stromal changes over time in serial biopsy samples. The top-5 features of pathologic stromal remodeling most strongly associated with adverse outcomes were also strongly associated with histories of both overt and indolent inflammatory events. Our findings identify previously unappreciated subgroups of higher- and lower-risk transplant patients, and highlight the translational potential of digital pathology analysis.

Evaluating threshold for donor fraction cell-free DNA using clinically available assay for rejection in pediatric and adult heart transplantation

BACKGROUND

The aims of the study were to assess the performance of a clinically available cell-free DNA (cfDNA) assay in a large cohort of pediatric and adult heart transplant recipients and to evaluate performance at specific cut points in detection of rejection.

METHODS

Observational, non-interventional, prospective study enrolled pediatric and adult heart transplant recipients from seven centers. Biopsy-associated plasma samples were used for cfDNA measurements. Pre-determined cut points were tested for analytic performance.

RESULTS

A total of 487 samples from 160 subjects were used for the analysis. There were significant differences for df-cfDNA values between rejection [0.21% (IQR 0.12-0.69)] and healthy samples [0.05% (IQR 0.01-0.14), p < .0001]. The pediatric rejection group had a median df-cfDNA value of 0.93% (IQR 0.28-2.84) compared to 0.09% (IQR 0.04-0.23) for healthy samples, p = .005. Overall negative predictive value was 0.94 while it was 0.99 for pediatric patients. Cut points of 0.13% and 0.15% were tested for various types of rejection profiles and were appropriate to rule out rejection.

CONCLUSION

The study suggests that pediatric patients with rejection show higher levels of circulating df-cfDNA compared to adults and supports the specific cut points for clinical use in pediatric and adult patients with overall acceptable performance.

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

BACKGROUND

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.

OBJECTIVES

To evaluate the ability of cardiac magnetic resonance (CMR) to noninvasively identify differences in PHT patients with AR and CAV.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Incidence of Acute Rejection Compared With Endomyocardial Biopsy Complications for Heart Transplant Patients in the Contemporary Era

BACKGROUND

The reference standard of detecting acute rejection (AR) in adult heart transplant (HTx) patients is an endomyocardial biopsy (EMB). The majority of EMBs are performed in asymptomatic patients. However, the incidence of treated AR compared with EMB complications has not been compared in the contemporary era (2010-current).

METHODS

The authors retrospectively analyzed 2769 EMBs obtained in 326 consecutive HTx patients between August 2019 and August 2022. Variables included surveillance versus for-cause indication, recipient and donor characteristics, EMB procedural data and pathological grades, treatment for AR, and clinical outcomes.

RESULTS

The overall EMB complications rate was 1.6%. EMBs performed within 1 mo after HTx compared with after 1 mo from HTx showed significantly increased complications (OR, 12.74, P  < 0.001). The treated AR rate was 14.2% in the for-cause EMBs and 1.2% in the surveillance EMBs. We found the incidence of AR versus EMB complications was significantly lower in the surveillance compared with the for-cause EMB group (OR, 0.05, P  < 0.001). We also found the incidence of EMB complications was higher than treated AR in surveillance EMBs.

CONCLUSIONS

The yield of surveillance EMBs has declined in the contemporary era, with a higher incidence of EMB complications compared with detected AR. The risk of EMB complications was highest within 1 mo after HTx. Surveillance EMB protocols in the contemporary era may need to be reevaluated.

Disulfiram treatment suppresses antibody-producing reactions by inhibiting macrophage activation and B cell pyrimidine metabolism

Antibody responses, involving B cells, CD4 + T cells, and macrophages, are implicated in autoimmune diseases and organ transplant rejection. We have previously shown that inhibiting FROUNT with disulfiram (DSF) suppresses macrophage activation and migration, effectively treating inflammatory diseases. In this study, we investigated the effectiveness of DSF in antibody-producing reactions. Using a heart transplantation mouse model with antibody-mediated rejection, we administered anti-CD8 antibody to exclude cellular rejection. DSF directly inhibited B cell responses in vitro and significantly reduced plasma donor-specific antibodies and graft antibody deposition in vivo, resulting in prolonged survival of the heart graft. DSF also mediated various effects, including decreased macrophage infiltration and increased Foxp3+ regulatory T-cells in the grafts. Additionally, DSF inhibited pyrimidine metabolism-related gene expression induced by B-cell stimulation. These findings demonstrate that DSF modulates antibody production in the immune response complexity by regulating B-cell and macrophage responses.

Impact of Everolimus Initiation and Corticosteroid Weaning During Acute Phase After Heart Transplantation on Clinical Outcome: Data from the Korean Organ Transplant Registry (KOTRY)

The effect of changes in immunosuppressive therapy during the acute phase post-heart transplantation (HTx) on clinical outcomes remains unclear. This study aimed to investigate the effects of changes in immunosuppressive therapy by corticosteroid (CS) weaning and everolimus (EVR) initiation during the first year post-HTx on clinical outcomes. We analyzed 622 recipients registered in the Korean Organ Transplant Registry (KOTRY) between January 2014 and December 2021. The median age at HTx was 56 years (interquartile range [IQR], 45-62), and the median follow-up time was 3.9 years (IQR 2.0-5.1). The early EVR initiation within the first year post-HTx and maintenance during the follow-up is associated with reduced the risk of primary composite outcome (all-cause mortality or re-transplantation) (HR, 0.24; 95% CI 0.09-0.68; p < 0.001) and cardiac allograft vasculopathy (CAV) (HR, 0.39; 95% CI 0.19-0.79; p = 0.009) compared with EVR-free or EVR intermittent treatment regimen, regardless of CS weaning. However, the early EVR initiation tends to increase the risk of acute allograft rejection compared with EVR-free or EVR intermittent treatment.

An Update on Myocarditis in Forensic Pathology

In forensic medicine, myocarditis is a complicated topic in the context of sudden death and medical malpractice. A good knowledge of the etiopathology, histopathology, and available literature are both indispensable and essential for the correct management and evaluation of the causal link. Some agents, which are rarely lethal for humans, are not necessarily related to death from myocarditis, even if an infection in other organs such as the gastrointestinal tract is documented. The diagnosis of the causes of death is often difficult and confusing. In some cases, the hypothetical diagnosis of myocarditis as the cause of death is formulated by deduction, causing error and misleading the correct temporal evaluation of pathological events. We reviewed the literature realizing that histomorphological data are scarce and often poorly documented. Only after COVID-19 have the histomorphological aspects of myocarditis been better documented. This is due to poor autopsy practice and poor accuracy in identifying the specific histotype of myocarditis with identification of the responsible agent. We believe that four points are essential for a better understanding and complete diagnosis of the disease: (1) clinical classification of myocarditis; (2) etiological classification of myocarditis; (3) pathophysiology of viral and bacterial infections with host response; and (4) histopathological diagnosis with precise identification of the histotype and pathogen. In the review we provide histological images from authoritative scientific references with the aim of providing useful information and food for thought to readers.