Diagnostic efficiency of rejection monitoring after heart transplantation with cardiac troponin T is improved in specific patient subgroups

Elevated Cardiac Troponin to Detect Acute Cellular Rejection After Cardiac Transplantation: A Systematic Review and Meta-Analysis

Cardiac troponin is well known as a highly specific marker of cardiomyocyte damage, and has significant diagnostic accuracy in many cardiac conditions. However, the value of elevated recipient troponin in diagnosing adverse outcomes in heart transplant recipients is uncertain. We searched MEDLINE (Ovid), Embase (Ovid), and the Cochrane Library from inception until December 2020. We generated summary sensitivity, specificity, and Bayesian areas under the curve (BAUC) using bivariate Bayesian modelling, and standardised mean differences (SMDs) to quantify the diagnostic relationship of recipient troponin and adverse outcomes following cardiac transplant. We included 27 studies with 1,684 cardiac transplant recipients. Patients with acute rejection had a statistically significant late elevation in standardised troponin measurements taken at least 1 month postoperatively (SMD 0.98, 95% CI 0.33–1.64). However, pooled diagnostic accuracy was poor (sensitivity 0.414, 95% CrI 0.174–0.696; specificity 0.785, 95% CrI 0.567–0.912; BAUC 0.607, 95% CrI 0.469–0.723). In summary, late troponin elevation in heart transplant recipients is associated with acute cellular rejection in adults, but its stand-alone diagnostic accuracy is poor. Further research is needed to assess its performance in predictive modelling of adverse outcomes following cardiac transplant.

Systematic Review Registration: identifier CRD42021227861

Elevated ST2 Distinguishes Incidences of Pediatric Heart and Small Bowel Transplant Rejection

Elevated serum soluble (s) suppressor of tumorigenicity-2 is observed during cardiovascular and inflammatory bowel diseases. To ascertain whether modulated ST2 levels signify heart (HTx) or small bowel transplant (SBTx) rejection, we quantified sST2 in serially obtained pediatric HTx (n = 41) and SBTx recipient (n = 18) sera. At times of biopsy-diagnosed HTx rejection (cellular and/or antibody-mediated), serum sST2 was elevated compared to rejection-free time points (1714 ± 329 vs. 546.5 ± 141.6 pg/mL; p = 0.0002). SBTx recipients also displayed increased serum sST2 during incidences of rejection (7536 ± 1561 vs. 2662 ± 543.8 pg/mL; p = 0.0347). Receiver operator characteristic (ROC) analysis showed that serum sST2 > 600 pg/mL could discriminate time points of HTx rejection and nonrejection (area under the curve [AUC] = 0.724 ± 0.053; p = 0.0003). ROC analysis of SBTx measures revealed a similar discriminative capacity (AUC = 0.6921 ± 0.0820; p = 0.0349). Quantitative evaluation of both HTx and SBTx biopsies revealed that rejection significantly increased allograft ST2 expression. Pathway and Network Analysis of biopsy data pinpointed ST2 in the dominant pathway modulated by rejection and predicted tumor necrosis factor-α and IL-1β as upstream activators. In total, our data indicate that alloimmune-associated pro-inflammatory cytokines increase ST2 during rejection. They also demonstrate that routine serum sST2 quantification, potentially combined with other biomarkers, should be investigated further to aid in the noninvasive diagnosis of rejection.

Repeated measurements of NT-pro-B-type natriuretic peptide, troponin T or C-reactive protein do not predict future allograft rejection in heart transplant recipients

BACKGROUND

Studies on the prognostic value of serial biomarker assays for future occurrence of allograft rejection (AR) are scarce. We examined whether repeated measurements of NT-pro-B-type natriuretic peptide (NT-proBNP), troponin T (TropT) and C-reactive protein (CRP) predict AR.

METHODS

From 2005 to 2010, 77 consecutive heart transplantation (HTx) recipients were included. The NT-proBNP, TropT, and CRP were measured at 16 ± 4 (mean ± standard deviation) consecutive routine endomyocardial biopsy surveillance visits during the first year of follow-up. Allograft rejection was defined as International Society for Heart and Lung Transplantation (ISHLT) grade 2R or higher at endomyocardial biopsy. Joint modeling was used to assess the association between repeated biomarker measurements and occurrence of future AR. Joint modeling accounts for dependence among repeated observations in individual patients.

RESULTS

The mean age of the patients at HTx was 49 ± 9.2 years, and 68% were men. During the first year of follow-up, 1,136 biopsies and concurrent blood samples were obtained, and 56 patients (73%) experienced at least one episode of AR. All biomarkers were elevated directly after HTx and achieved steady-state after ∼ 12 weeks, both in patients with or without AR. No associations were present between the repeated measurements of NT-proBNP, TropT, or CRP and AR both early (weeks 0-12) and late (weeks 13-52) in the course after HTx (hazard ratios for weeks 13-52: 0.96 (95% confidence interval, 0.55-1.68), 0.67 (0.27-1.69), and 1.44 (0.90-2.30), respectively, per ln[unit]). Combining the three biomarkers in one model also rendered null results.

CONCLUSION

The temporal evolution of NT-proBNP, TropT, and CRP before AR did not predict occurrence of acute AR both in the early and late course of the first year after HTx.

Biomarkers of heart transplant rejection: the good, the bad, and the ugly!

Acute cellular rejection (ACR), antibody-mediated rejection (AMR), and cardiac allograft vasculopathy (CAV) are important limitations for the long-term survival of heart transplant recipients. Although much progress has been made in reducing ACR with modern immunosuppressive treatments and continuous biopsy surveillance, there is still a long way to go to better understand and treat AMR, to enable early detection of patients at risk of CAV, and to reduce the development and sustained progression of this irreversible disease that permanently compromises graft function. This review considers the advances made in ACR detection and treatment allowing a more prolonged survival and the risk factors leading to endothelial injury, dysfunction, inflammation, and subsequent CAV, as well as new treatment modalities for CAV. The review also evaluates the controversies around the definition, pathogenesis, and treatment of AMR. To date, much progress is still needed to significantly reduce post-transplant complications and increase graft and patient survival.

Correlation of noninvasive markers of cardiac allograft rejection with endomyocardial biopsy: a case report

Although endomyocardial biopsy remains the gold standard to diagnose cardiac allograft rejection, the search continues for clinical parameters that may aid in the early diagnosis of rejection. We report the case of a 29-year-old man who underwent orthotopic heart transplantation and subsequently had multifocal moderate allograft rejection. During the patient's hospital course, he exhibited a number of clinical parameters that served as important clues for the worsening rejection. After aggressive immunosuppression, the improvement of these markers hinted toward his eventual recovery.

Increased serum creatine kinase is a reliable marker for acute transplanted heart rejection diagnosis in rats

Different molecules have been studied as biochemical markers in heart transplantation. However, their utility is under discussion as results in human and animal models are controversial. In this work, lactate dehydrogenase (LDH), creatine kinase (CK) and cardiac troponin I (TnI) were studied as serologic markers of acute rejection after heterotopical heart transplantation in rats. In predictable rejection experiments, animals were divided into three groups: nonoperated (Lewis rats), control group (Lewis-Lewis isografts) and rejection group (Brown Norway-Lewis allografts). Nonpredictable rejection experiments were performed using nonconsanguineous Sprague-Dawley allografts. In predictable rejection experiments, LDH activity was similar between control and rejection groups. TnI values were heterogeneous in control and rejection groups. In contrast, the rejection group showed CK activity increased 4.5-fold compared with the control group. In addition to these predictable studies, we also presented novel nonpredictable experiments in which rats were divided into groups based on low and high CK activity. Histologic studies in these rats showed that none of those with low CK activity presented rejection signs, while all animals with high CK levels showed grade 2R rejection. These results suggest that CK might be an excellent marker for prediction of rejection in heart transplantation.

Should we be doing routine biopsy after heart transplantation in a new era of anti-rejection?

PURPOSE OF REVIEW

The endomyocardial biopsy has defined the diagnosis of rejection in cardiac transplantation and has historically been a vital tool when rejection rates following transplantation were high. Surveillance biopsies have been the cornerstone of post-transplant management, as signs or symptoms of rejection are non-specific. With significant improvements in immunosuppressive therapy, however, the incidence of clinically significant rejection has declined, bringing into question the need for routine surveillance biopsy. This article reviews the current role of the endomyocardial biopsy in the management of patients following cardiac transplantation.

RECENT FINDINGS

The endomyocardial biopsy is also limited by sub-optimal interobserver reproducibility, a lack of consensus with regard to treating certain grades of rejection, and often a lack of histological findings in patients with hemodynamic compromise, which frequently responds to anti-rejection therapy. Recent refinements, however, have allowed improved diagnosis of antibody mediated rejection, a relatively recently recognized entity. Moreover, a number of non-invasive modalities have been investigated recently as potential substitutes for the endomyocardial biopsy in detecting rejection.

SUMMARY

Despite the development of a variety of non-invasive methods for the detection of rejection, the endomyocardial biopsy will remain important in the management of patients following cardiac transplantation, as non-invasive techniques are associated with low specificity for the diagnosis of rejection. A new standardized classification will likely improve the utility of the biopsy by simplifying interpretation of cellular rejection and importantly allowing recognition of antibody-mediated rejection.

Immunosuppression, diagnosis, and treatment of cardiac allograft rejection

The success of cardiac transplantation has been largely attributable to the development of effective immunosuppressive regimens. The calcineurin inhibitors were pivotal in reducing the frequency of acute rejection and improving early survival. Newer agents, including mycophenolate mofetil and proliferation signal inhibitors, show some promise in further reducing episodes of acute allograft rejection and also having a significant impact on reducing transplant vasculopathy. The role of cytolytic induction therapy remains unclear, although its use may be most appropriate in the high risk presensitized transplant recipient. While the endomyocardial biopsy remains the gold standard for the diagnosis of acute allograft rejection, its invasive nature makes the test suboptimal. The presence of biopsy 'negative' rejection has also led to an appreciation for the role of antibody-mediated rejection in cardiac allograft dysfunction. Effective noninvasive evaluation of allograft rejection remains the ultimate challenge. While imaging technologies have some utility because of their ease of use, more sophisticated techniques such as gene-expession analysis from peripheral blood may show the greatest promise. Management of established acute allograft rejection has significantly improved with our understanding of the immune mechanisms involved. Therapies may be targeted specifically at cellular or humoral components of the immune system.

Utility of biochemical markers in the follow-up of heart transplant recipients

Endomyocardial biopsy (EMB) is currently the standard method to diagnose acute graft rejection. However, considering the potential complications of this procedure, a noninvasive marker of rejection would be an ideal alternative or at least a helpful adjunct to posttransplant management. We measured myoglobin (Myo), creatine kinase MB mass (CK-MBm), troponin T (cTnT), serum amyloid A (SAA), and C-reactive protein (CRP) in 57 patients (mean age 37.5 years) who underwent orthotopic heart transplantation for end-stage cardiac failure between January and December 2001.Endomyocardial biopsies were performed routinely after surgery and histologically diagnosed rejection was graded according to the criteria of the International Society of Heart and Lung Transplantation. Concomittant with the biopsies, blood samples were drawn from the coronary sinus (central blood samples) and from a peripheral vein (peripheral blood samples) to assay biochemical markers. Among 149 EMB evaluated, 87 were negative (grade 0); 28 showed grade 1a rejection; 26 showed grade 1b; and 8 showed grade > 1b (2 were grade 2, 6 were grade 3a). Grades 0 and 1a were considered to be negative, while grades 1b and >1b were considered positive indicating potential acute graft rejection. cTnT, Myo, CK-MBm, SAA, and CRP levels were measured in 149 central blood samples and 149 peripheral blood samples. Myo and CK-MBm did not show significant changes. cTnT seems to be a potentially useful addition to the EMB results, while SAA and CRP showed variations with respect to EMB grade both in central and peripheral samples.