Surveillance Endomyocardial Biopsy in the Modern Era Produces Low Diagnostic Yield for Cardiac Allograft Rejection

Sex-specific patterns of donor-derived cell-free DNA in heart transplant rejection: An analysis from the Genomic Research Alliance for Transplantation (GRAfT)

BACKGROUND

Noninvasive methods for surveillance of acute rejection are increasingly used in heart transplantation (HT), including donor-derived cell-free DNA (dd-cfDNA). As other cardiac biomarkers differ by sex, we hypothesized that there may be sex-specific differences in the performance of dd-cfDNA for the detection of acute rejection. The purpose of the current study was to examine patterns of dd-cfDNA seen in quiescence and acute rejection in male and female transplant recipients.

METHODS

Patients enrolled in the Genomic Research Alliance for Transplantation who were ≥18 years at the time of HT were included. Rejection was defined by endomyocardial biopsy with acute cellular rejection (ACR) grade ≥2R and/or antibody-mediated rejection ≥ pAMR 1. dd-cfDNA was quantitated using shotgun sequencing. Median dd-cfDNA levels were compared between sexes during quiescence and rejection. The performance of dd-cfDNA by sex was assessed using area under the receiver operator characteristic (AUROC) curve. Allograft injury was defined as dd-cfDNA ≥0.25%.

RESULTS

One hundred fifty-one unique patients (49 female, 32%) were included in the analysis with 1,119 available dd-cfDNA measurements. Baseline characteristics including demographics and comorbidities were not significantly different between sexes. During quiescence, there were no significant sex differences in median dd-cfDNA level (0.04% [IQR 0.00, 0.16] in females vs 0.03% [IQR 0.00, 0.12] in males, p = 0.22). There were no significant sex differences in median dd-cfDNA for ACR (0.33% [0.21, 0.36] in females vs 0.32% [0.21, 1.10] in males, p = 0.57). Overall, median dd-cfDNA levels were higher in antibody-mediated rejection (AMR) than ACR but did not significantly differ by sex (0.50% [IQR 0.18, 0.82] in females vs 0.63% [IQR 0.32, 1.95] in males, p = 0.51). Elevated dd-cfDNA detected ACR/AMR with an AUROC of 0.83 in females and 0.89 in males, p-value for comparison = 0.16.

CONCLUSIONS

There were no significant sex differences in dd-cfDNA levels during quiescence and rejection. Performance characteristics were similar, suggesting similar diagnostic thresholds can be used in men and women for rejection surveillance.

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.

Does bortezomib influence pre-transplant desensitization therapy or benefit post-heart transplant outcomes for highly sensitized patients?

BACKGROUND

The use of bortezomib which is a proteasome inhibitor has been demonstrated to be efficacious in small number of patients as a desensitization strategy in heart transplant. We reviewed our single center's experience using Bortezomib along with plasmapheresis as desensitization therapy for highly sensitized patients to assess pre- and post-transplant outcomes.

METHOD

We assessed 43 highly sensitized patients awaiting HTx (defined as cPRA > 50%) between 2010 and 2021 who underwent desensitization therapy with bortezomib. Only those patients who subsequently underwent HTx were included in this study. Enrolled patients received up to four doses of bortezomib (1.3 mg/m2 ) over 2 weeks in conjunction with plasmapheresis. The efficacy of PP/BTZ was assessed by comparing the calculated panel reactive antibodies to HLA class I or class II antigens. Post-transplant outcomes including overall survival and incidence of rejection were compared to those of non-sensitized patients (PRA < 10%, n = 649) from the same center.

RESULTS

The average cPRA prior to PP/BTZ was 94.5%. Post-PP/BTZ there was no statistically significant decline in mean cPRA, class I cPRA, or class II cPRA, though the average percentage decrease in class I cPRA (8.7 ± 17.0%) was higher than the change in class II cPRA (4.4 ± 13.3%). Resulted were also replicated with C1q-binding antibodies showing more effect on I class compared to class II (15.0 ± 37.4% vs. 6.8 ± 33.6%) as well as with 1:8 dilutional assay (14.0 ± 23.0% vs. 9.1 ± 34.9%). Additionally, PP/BTZ treated patients and the control group of non-sensitized patients had similar overall 1 year survival (95.4 vs. 92.5%) but patients with PP/BTZ had increased incidence of AMR (79.1% vs. 97.1%, p = < .001), any treated rejection (62.8% vs. 86.7%, p = < .001) and de novo DSA development (81.4% vs. 92.5%, p = .007). Major side effects of PP/BTZ included thrombocytopenia (42%), infection requiring antibiotics (28%), and neuropathy (12%).

CONCLUSION

The use of bortezomib in highly sensitized patients does not significantly lower circulating antibodies prior to heart transplantation. However, its use may improve the chances of obtaining an immuno-compatible donor heart and contribute to acceptable post-transplant outcomes.

Benefit versus Risk of Endomyocardial Biopsy 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 benefit of diagnosing and treating AR compared to the risk of EMB complications has not been compared in the contemporary era (2010-current).

Methods

The authors retrospectively analyzed 2,769 EMB 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 pathologic grades, treatment for AR, and clinical outcomes.

Results

The overall EMB complication rate was 1.6%. EMBs performed within 1 month after HTx compared to after 1 month 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 benefit/risk ratio was significantly lower in the surveillance compared to the for cause EMB group (OR = 0.05, p < 0.001). We also found the benefit to be lower than risk in surveillance EMBs.

Conclusions

The yield of surveillance EMBs has declined, while for cause EMBs continued to demonstrate a high benefit/risk ratio. The risk of EMB complications was highest within 1 month after HTx. Surveillance EMB protocols in the contemporary era may need to be re-evaluated.

Native T1 mapping detects both acute clinical rejection and graft dysfunction in pediatric heart transplant patients

BACKGROUND

Cardiovascular magnetic resonance (CMR) is emerging as an important tool for cardiac allograft assessment. Native T1 mapping may add value in identifying rejection and in assessing graft dysfunction and myocardial fibrosis burden. We hypothesized that CMR native T1 values and features of textural analysis of T1 maps would identify acute rejection, and in a secondary analysis, correlate with markers of graft dysfunction, and with fibrosis percentage from endomyocardial biopsy (EMB).

METHODS

Fifty cases with simultaneous EMB, right heart catheterization, and 1.5 T CMR with breath-held T1 mapping via modified Look-Locker inversion recovery (MOLLI) in 8 short-axis slices and subsequent quantification of mean and peak native T1 values, were performed on 24 pediatric subjects. A single mid-ventricular slice was used for image texture analysis using nine gray-level co-occurrence matrix features. Digital quantification of Masson trichrome stained EMB samples established degree of fibrosis. Markers of graft dysfunction, including serum brain natriuretic peptide levels and hemodynamic measurements from echocardiography, catheterization, and CMR were collated. Subjects were divided into three groups based on degree of rejection: acute rejection requiring new therapy, mild rejection requiring increased ongoing therapy, and no rejection with no change in treatment. Statistical analysis included student's t-test and linear regression.

RESULTS

Peak and mean T1 values were significantly associated with acute rejection, with a monotonic trend observed with increased grade of rejection. Texture analysis demonstrated greater spatial heterogeneity in T1 values, as demonstrated by energy, entropy, and variance, in cases requiring treatment. Interestingly, 2 subjects who required increased therapy despite low grade EMB results had abnormal peak T1 values. Peak T1 values also correlated with increased BNP, right-sided filling pressures, and capillary wedge pressures. There was no difference in histopathological fibrosis percentage among the 3 groups; histopathological fibrosis did not correlate with T1 values or markers of graft dysfunction.

CONCLUSION

In pediatric heart transplant patients, native T1 values identify acute rejection requiring treatment and may identify graft dysfunction. CMR shows promise as an important tool for evaluation of cardiac grafts in children, with T1 imaging outperforming biopsy findings in the assessment of rejection.

A Review of Biomarkers of Cardiac Allograft Rejection: Toward an Integrated Diagnosis of Rejection

Despite major advances in immunosuppression, allograft rejection remains an important complication after heart transplantation, and it is associated with increased morbidity and mortality. The gold standard invasive strategy to monitor and diagnose cardiac allograft rejection, based on the pathologic evaluation of endomyocardial biopsies, suffers from many limitations including the low prevalence of rejection, sample bias, high inter-observer variability, and international working formulations based on arbitrary cut-offs that simplify the landscape of rejection. The development of innovative diagnostic and prognostic strategies—integrating conventional histology, molecular profiling of allograft biopsy, and the discovery of new tissue or circulating biomarkers—is one of the major challenges of translational medicine in solid organ transplantation, and particularly in heart transplantation. Major advances in the field of biomarkers of rejection have paved the way for a paradigm shift in the monitoring and diagnosis of cardiac allograft rejection. We review the recent developments in the field, including non-invasive biomarkers to minimize the number of protocol endomyocardial biopsies and tissue biomarkers as companion tools of pathology to refine the diagnosis of cardiac rejection. Finally, we discuss the potential role of these biomarkers to provide an integrated bio-histomolecular diagnosis of cardiac allograft rejection.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Multi-parametric cardiovascular magnetic resonance with regadenoson stress perfusion is safe following pediatric heart transplantation and identifies history of rejection and cardiac allograft vasculopathy

BACKGROUND

The progressive risk of graft failure in pediatric heart transplantation (PHT) necessitates close surveillance for rejection and coronary allograft vasculopathy (CAV). The current gold standard of surveillance via invasive coronary angiography is costly, imperfect and associated with complications. Our goal was to assess the safety and feasibility of a comprehensive multi-parametric CMR protocol with regadenoson stress perfusion in PHT and evaluate for associations with clinical history of rejection and CAV.

METHODS

We performed a retrospective review of 26 PHT recipients who underwent stress CMR with tissue characterization and compared with 18 age-matched healthy controls. CMR protocol included myocardial T2, T1 and extracellular volume (ECV) mapping, late gadolinium enhancement (LGE), qualitative and semi-quantitative stress perfusion (myocardial perfusion reserve index; MPRI) and strain imaging. Clinical, demographics, rejection score and CAV history were recorded and correlated with CMR parameters.

RESULTS

Mean age at transplant was 9.3 ± 5.5 years and median duration since transplant was 5.1 years (IQR 7.5 years). One patient had active rejection at the time of CMR, 11/26 (42%) had CAV 1 and 1/26 (4%) had CAV 2. Biventricular volumes were smaller and cardiac output higher in PHT vs. healthy controls. Global T1 (1053 ± 42 ms vs 986 ± 42 ms; p < 0.001) and ECV (26.5 ± 4.0% vs 24.0 ± 2.7%; p = 0.017) were higher in PHT compared to helathy controls. Significant relationships between changes in myocardial tissue structure and function were noted in PHT: increased T2 correlated with reduced LVEF (r = - 0.57, p = 0.005), reduced global circumferential strain (r = - 0.73, p < 0.001) and reduced global longitudinal strain (r = - 0.49, p = 0.03). In addition, significant relationships were noted between higher rejection score and global T1 (r = 0.38, p = 0.05), T2 (r = 0.39, p = 0.058) and ECV (r = 0.68, p < 0.001). The presence of even low-grade CAV was associated with higher global T1, global ECV and maximum segmental T2. No major side effects were noted with stress testing. MPRI was analyzed with good interobserver reliability and was lower in PHT compared to healthy controls (0.69 ± - 0.21 vs 0.94 ± 0.22; p < 0.001).

CONCLUSION

In a PHT population with low incidence of rejection or high-grade CAV, CMR demonstrates important differences in myocardial structure, function and perfusion compared to age-matched healthy controls. Regadenoson stress perfusion CMR could be safely and reliably performed. Increasing T2 values were associated with worsening left ventricular function and increasing T1/ECV values were associated with rejection history and low-grade CAV. These findings warrant larger prospective studies to further define the role of CMR in PHT graft surveillance.

Endothelial Stromal PD-L1 (Programmed Death Ligand 1) Modulates CD8+ T-Cell Infiltration After Heart Transplantation

BACKGROUND

The role of checkpoint axes in transplantation has been partially addressed in animal models but not in humans. Occurrence of fulminant myocarditis with allorejection-like immunologic features in patients under anti-PD1 (programmed death cell protein 1) treatment suggests a key role of the PD1/PD-L1 (programmed death ligand 1) axis in cardiac immune homeostasis.

METHODS

We cross-sectionally studied 23 heart transplant patients undergoing surveillance endomyocardial biopsy. Endomyocardial tissue and peripheral blood mononuclear cells were analyzed by flow cytometry. Multivariate logistic regression analyses including demographic, clinical, and hemodynamic parameters were performed. Murine models were used to evaluate the impact of PD-L1 endothelial graft expression in allorejection.

RESULTS

We found that myeloid cells dominate the composition of the graft leukocyte compartment in most patients, with variable T-cell frequencies. The CD (cluster of differentiation) 4:CD8 T-cell ratios were between 0 and 1.5. The proportion of PD-L1 expressing cells in graft endothelial cells, fibroblasts, and myeloid leukocytes ranged from negligible up to 60%. We found a significant inverse logarithmic correlation between the proportion of PD-L1+HLA (human leukocyte antigen)-DR+ endothelial cells and CD8+ T cells (slope, -18.3 [95% CI, -35.3 to -1.3]; P=0.030). PD-L1 expression and leukocyte patterns were independent of demographic, clinical, and hemodynamic parameters. We confirmed the importance of endothelial PD-L1 expression in a murine allogeneic heart transplantation model, in which Tie2Crepdl1fl/fl grafts lacking PD-L1 in endothelial cells were rejected significantly faster than controls.

CONCLUSIONS

Loss of graft endothelial PD-L1 expression may play a role in regulating CD8+ T-cell infiltration in human heart transplantation. Murine model results suggest that loss of graft endothelial PD-L1 may facilitate alloresponses and rejection.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Molecular Diagnosis of Rejection in Heart Transplantation

Despite the overall success of heart transplantation as a definitive treatment for endstage heart failure, cardiac allograft rejection remains an important cause of morbidity and mortality. Endomyocardial biopsy has been the standard of care for rejection monitoring, but is associated with several diagnostic limitations and serious procedural complications. The use of molecular diagnostics has emerged over the past decade as a tool to potentially circumvent some of these limitations. We present an update on novel molecular approaches to detecting transplant rejection, focusing on 4 categories: microarray technology, gene expression profiling, cell-free DNA and microRNA.

Myocardial Vascular Function Assessed by Dynamic Oxygenation-sensitive Cardiac Magnetic Resonance Imaging Long-term Following Cardiac Transplantation

BACKGROUND

Coronary vascular function is related to adverse outcomes following cardiac transplantation (CTx) in patients with or without cardiac allograft vasculopathy (CAV). The noninvasive assessment of the myocardial vascular response using oxygenation-sensitive cardiac magnetic resonance (OS-CMR has not been investigated in stable long-term CTx recipients).

METHODS

CTx patients were prospectively recruited to complete a CMR study with a breathing maneuver of hyperventilation followed by a voluntary apnea. Changes in OS-sensitive signal intensity reflecting the myocardial oxygenation response were monitored and expressed as % change in response to these breathing maneuvers. Myocardial injury was further investigated with T2-weighted imaging, native and postcontrast T1 measurements, extracellular volume measurements, and late gadolinium enhancement.

RESULTS

Forty-six CTx patients with (n = 23) and without (n = 23) CAV, along with 25 healthy controls (HC), were enrolled. The OS response was significantly attenuated in CTx compared with HC at the 30-second time-point into the breath-hold (2.63% ± 4.16% versus 6.40% ± 5.96%; P = 0.010). Compared with HC, OS response was lower in CTx without CAV (2.62% ± 4.60%; P < 0.05), while this response was further attenuated in patients with severe CAV (grades 2-3, -2.24% ± 3.65%). An inverse correlation was observed between OS-CMR, ventricular volumes, and diffuse fibrosis measured by extracellular volume mapping.

CONCLUSIONS

In heart transplant patients, myocardial oxygenation is impaired even in the absence of CAV suggesting microvascular dysfunction. These abnormalities can be identified by oxygenation-sensitive CMR using simple breathing maneuvers.

Heart Failure Association of the ESC, Heart Failure Society of America and Japanese Heart Failure Society Position statement on endomyocardial biopsy

Endomyocardial biopsy (EMB) is an invasive procedure, globally most often used for the monitoring of heart transplant (HTx) rejection. In addition, EMB can have an important complementary role to the clinical assessment in establishing the diagnosis of diverse cardiac disorders, including myocarditis, cardiomyopathies, drug-related cardiotoxicity, amyloidosis, other infiltrative and storage disorders, and cardiac tumours. Improvements in EMB equipment and the development of new techniques for the analysis of EMB samples have significantly improved diagnostic precision of EMB. The present document is the result of the Trilateral Cooperation Project between the Heart Failure Association of the European Society of Cardiology, the Heart Failure Society of America, and the Japanese Heart Failure Society. It represents an expert consensus aiming to provide a comprehensive, up-to-date perspective on EMB, with a focus on the following main issues: (i) an overview of the practical approach to EMB, (ii) an update on indications for EMB, (iii) a revised plan for HTx rejection surveillance, (iv) the impact of multimodality imaging on EMB, and (v) the current clinical practice in the worldwide use of EMB.

Heart Failure Association, Heart Failure Society of America, and Japanese Heart Failure Society Position Statement on Endomyocardial Biopsy

Endomyocardial biopsy (EMB) is an invasive procedure, globally most often used for the monitoring of heart transplant rejection. In addition, EMB can have an important complementary role to the clinical assessment in establishing the diagnosis of diverse cardiac disorders, including myocarditis, cardiomyopathies, drug-related cardiotoxicity, amyloidosis, other infiltrative and storage disorders, and cardiac tumors. Improvements in EMB equipment and the development of new techniques for the analysis of EMB samples has significantly improved the diagnostic precision of EMB. The present document is the result of the Trilateral Cooperation Project between the Heart Failure Association of the European Society of Cardiology, Heart Failure Society of America, and the Japanese Heart Failure Society. It represents an expert consensus aiming to provide a comprehensive, up-to-date perspective on EMB, with a focus on the following main issues: (1) an overview of the practical approach to EMB, (2) an update on indications for EMB, (3) a revised plan for heart transplant rejection surveillance, (4) the impact of multimodality imaging on EMB, and (5) the current clinical practice in the worldwide use of EMB.

Protocol endomyocardial biopsy beyond 6 months-It is time to move on

The optimal duration and frequency of routine surveillance endomyocardial biopsy (EMB) have been questioned in the current era of heart transplantation (HT), where the advances in immunosuppression and donor selection strategies have led to a decline in acute allograft rejection. We investigated the utility of routine EMB beyond 6 months post-HT. A single-center retrospective review was performed on 2963 EMBs from 220 HT recipients over 10 years. Each EMB was categorized into protocol or symptom-triggered biopsy and reviewed for rejection. Heart transplant recipients with ≥2 known risk factors for rejection were designated as an elevated risk group. The majority of rejections occurred within 3 months following HT. The yield of routine protocol EMBs was significantly lower than symptom-triggered EMBs, not only during the first 6 months post-HT (1.6% vs. 33.3%, P < .0001), but more so during the 6-12 months (0.1% vs 83.0%, P < .0001). A similar pattern was observed in heart transplant recipients at both elevated and standard risk for rejection. In conclusion, EMB was found to be a low-yield screening modality for rejection beyond 6 months post-HT.

[Pathology of heart transplantation: Where are we now?]

Pathology is still the gold standard for the diagnosis of rejection in heart transplantation. During the last decade, molecular pathology has emerged as a powerful tool for the understanding of the processes implicated in allograft rejection. Transcriptomic analysis of the allograft may also help the pathologist for diagnosis and accurate classification of rejection. This review will describe the recent advances and perspectives of molecular pathology in the field of heart transplantation.

Endomyocardial Biopsy and Prevalence of Acute Cellular Rejection in Heart Transplantation

BACKGROUND

Percutaneous endomyocardial biopsy (EMB) remains the criterion standard method for surveillance of allograft rejection after heart transplant (HT). However, data regarding utility of EMBs and prevalence of acute cellular rejection (ACR) in Asian populations are still limited. We aimed to report our experience in the use of EMBs and prevalence of ACR in HT recipients.

METHODS

We retrospectively evaluated all EMBs from consecutive HT recipients between January 2008 and December 2018. EMB pathology results were according to International Society for Heart and Lung Transplantation 2004 revision of biopsy grading. We also divided patients into previous era and current era group (underwent HT before and after 2015) to compare prevalence of ACR and survival outcome.

RESULTS

A total of 832 EMBs from 81 HT recipients were included. Pathologic reports revealed ACR grade 1R 22.8%, 2R 4.2%, and 3R 0.6%. At patient level, at least 1 episode of ACR grade 1R, 2R, and 3R were found in 70.6%, 24.7%, and 3.5% of the patients, respectively. When compared between era, frequency of EMB during the first year after HT in current era was significantly higher (9.74 ± 3.38 vs 4.93 ± 3.29, P < .001), but lower frequency of rejection grade ≥ 2R were found (2.3% vs 8.1%, P < .001). However, 1-year survival was not statistically different (76% in previous era vs 80% in current era, P = .37).

CONCLUSIONS

From our study, prevalence of grade ≥ 2R rejection was approximately 5%, which is comparable with previous studies. Further studies are needed to evaluate proper interval and number of EMBs in HT recipients.

Utility of routine evaluations for rejection in patients greater than 2 years after heart transplantation

AIMS

Guidelines support routine surveillance testing for rejection for at least 5 years after heart transplant (HT). In patients greater than 2 years post-HT, we examined which clinical characteristics predict continuation of routine surveillance studies, outcomes following discontinuation of routine surveillance, and the cost-effectiveness of different surveillance strategies.

METHODS AND RESULTS

We retrospectively identified subjects older than 18 who underwent a first HT at our centre from 2007 to 2016 and who survived ≥760 days (n = 217) post-HT. The clinical context surrounding all endomyocardial biopsies (EMBs) and gene expression profiles (GEPs) was reviewed to determine if studies were performed routinely or were triggered by a change in clinical status. Subjects were categorized as following a test-based surveillance (n = 159) or a signs/symptoms surveillance (n = 53) strategy based on treating cardiologist intent to continue routine studies after the second post-transplant year. A Markov model was constructed to compare two test-based surveillance strategies to a baseline strategy of discontinuing routine studies. One thousand twenty studies were performed; 835 were routine. Significant rejection was absent in 99.0% of routine EMBs and 99.8% of routine GEPs. The treating cardiologist's practice duration, patient age, and immunosuppressive regimen predicted surveillance strategy. There were no differences in outcomes between groups. Routine surveillance EMBs cost more and were marginally less effective than a strategy of discontinuing routine studies after 2 years; surveillance GEPs had an incremental cost-effectiveness ratio of $1.67 million/quality-adjusted life-year.

CONCLUSIONS

Acute asymptomatic rejection is rare after the second post-transplant year. Obtaining surveillance studies beyond the second post-transplant year is not cost-effective.

Myocardial velocity, intra-, and interventricular dyssynchrony evaluated by tissue phase mapping in pediatric heart transplant recipients

BACKGROUND

Endomyocardial biopsy (EMB) is the standard method for detecting allograft rejection in pediatric heart transplants (Htx). As EMB is invasive and carries a risk of complications, there is a need for a noninvasive alternative for allograft monitoring.

PURPOSE

To quantify left and right ventricular (LV & RV) peak velocities, velocity twist, and intra-/interventricular dyssynchrony using tissue phase mapping (TPM) in pediatric Htx compared with controls, and to explore the relationship between global cardiac function parameters and the number of rejection episodes to these velocities and intra-/interventricular dyssynchrony.

STUDY TYPE

Prospective.

SUBJECTS

Twenty Htx patients (age: 16.0 ± 3.1 years, 11 males) and 18 age- and sex-matched controls (age: 15.5 ± 4.3 years, nine males).

FIELD STRENGTH/SEQUENCE

5T; 2D balanced cine steady-state free-precession (bSSFP), TPM (2D cine phase contrast with three-directional velocity encoding).

ASSESSMENT

LV and RV circumferential, radial, and long-axis velocity-time curves, global and segmental peak velocities were measured using TPM. Short-axis bSSFP images were used to measure global LV and RV function parameters.

STATISTICAL TESTS

A normality test (Lilliefors test) was performed on all data. For comparisons, a t-test was used for normally distributed data or a Wilcoxon rank-sum test otherwise. Correlations were determined by a Pearson correlation.

RESULTS

Htx patients had significantly reduced LV (P < 0.05-0.001) and RV (P < 0.05-0.001) systolic and diastolic global and segmental long-axis velocities, reduced RV diastolic peak twist (P < 0.01), and presented with higher interventricular dyssynchrony for long-axis and circumferential motions (P < 0.05-0.001). LV diastolic long-axis dyssynchrony (r = 0.48, P = 0.03) and RV diastolic peak twist (r = -0.64, P = 0.004) significantly correlated with the total number of rejection episodes.

DATA CONCLUSION

TPM detected differences in biventricular myocardial velocities in pediatric Htx patients compared with controls and indicated a relationship between Htx myocardial velocities and rejection history.

LEVEL OF EVIDENCE

2 Technical Efficacy Stage: 3 J. Magn. Reson. Imaging 2020;51:1212-1222.

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

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

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

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

Lower frequency routine surveillance endomyocardial biopsies after heart transplantation

In heart transplantation (HTx) patients, routine surveillance endomyocardial biopsies (rsEMB) are recommended for the detection of early cardiac allograft rejection. However, there is no consensus on the optimal frequency of rsEMB. Frequent rsEMB have shown a low diagnostic yield in the new era of potent immunosuppressive regimen. Efficacy and safety of lower frequency rsEMB have not been investigated so far. In this retrospective, single centre, observational study we evaluated 282 patients transplanted between 2004 and 2014. 218 of these patients were investigated by rsEMB and symptom-triggered EMB (stEMB). We evaluated EMB results, complications, risk factors for rejection, survival 1 and 5 years as well as incidence of cardiac allograft vasculopathy (CAV) 3 years after HTx. A mean of 7.1 ± 2.5 rsEMB were conducted per patient within the first year after HTx identifying 7 patients with asymptomatic and 9 patients with symptomatic acute rejection requiring glucocorticoide pulse therapy. Despite this relatively low frequency of rsEMB, only 6 unscheduled stEMB were required in the first year after HTx leading to 2 additional treatments. In 6 deaths among all 282 patients (2.1%), acute rejection could not be ruled out as a potential underlying cause. Overall survival at 1 year was 78.7% and 5-year survival was 74%. Incidence of CAV was 17% at 3-year follow-up. Morbidity and mortality of lower frequency rsEMB are comparable with data from the International Society for Heart and Lung Transplantation (ISHLT) registry. Consensus is needed on the optimal frequency of EMB.

Gene Expression Profiling for the Identification and Classification of Antibody-Mediated Heart Rejection

BACKGROUND

Antibody-mediated rejection (AMR) contributes to heart allograft loss. However, an important knowledge gap remains in terms of the pathophysiology of AMR and how detection of immune activity, injury degree, and stage could be improved by intragraft gene expression profiling.

METHODS

We prospectively monitored 617 heart transplant recipients referred from 4 French transplant centers (January 1, 2006-January 1, 2011) for AMR. We compared patients with AMR (n=55) with a matched control group of 55 patients without AMR. We characterized all patients using histopathology (ISHLT [International Society for Heart and Lung Transplantation] 2013 grades), immunostaining, and circulating anti-HLA donor-specific antibodies at the time of biopsy, together with systematic gene expression assessments of the allograft tissue, using microarrays. Effector cells were evaluated with in vitro human cell cultures. We studied a validation cohort of 98 heart recipients transplanted in Edmonton, AB, Canada, including 27 cases of AMR and 71 controls.

RESULTS

A total of 240 heart transplant endomyocardial biopsies were assessed. AMR showed a distinct pattern of injury characterized by endothelial activation with microcirculatory inflammation by monocytes/macrophages and natural killer (NK) cells. We also observed selective changes in endothelial/angiogenesis and NK cell transcripts, including CD16A signaling and interferon-γ-inducible genes. The AMR-selective gene sets accurately discriminated patients with AMR from those without and included NK transcripts (area under the curve=0.87), endothelial activation transcripts (area under the curve=0.80), macrophage transcripts (area under the curve=0.86), and interferon-γ transcripts (area under the curve=0.84; P<0.0001 for all comparisons). These 4 gene sets showed increased expression with increasing pathological AMR (pAMR) International Society for Heart and Lung Transplantation grade (P<0.001) and association with donor-specific antibody levels. The unsupervised principal components analysis demonstrated a high proportion of molecularly inactive pAMR1(I+), and there was significant molecular overlap between pAMR1(H⁺) and full-blown pAMR2/3 cases. Endothelial activation transcripts, interferon-γ, and NK transcripts showed association with chronic allograft vasculopathy. The molecular architecture and selective AMR transcripts, together with gene set discrimination capacity for AMR identified in the discovery set, were reproduced in the validation cohort.

CONCLUSIONS

Tissue-based measurements of specific pathogenesis-based transcripts reflecting NK burden, endothelial activation, macrophage burden, and interferon-γ effects accurately classify AMR and correlate with degree of injury and disease activity. This study illustrates the clinical potential of a tissue-based analysis of gene transcripts to refine diagnosis of heart transplant rejection.