Usefulness of serial monitoring of B-type natriuretic peptide for the detection of acute rejection after heart transplantation

The utilization of molecular microscope in management of heart transplant recipients in the era of noninvasive monitoring

INTRODUCTION

Monitoring for graft rejection is a fundamental tenet of post-transplant follow-up. In heart transplantation (HT) in particular, rejection has been traditionally assessed with endomyocardial biopsy (EMB). EMB has potential complications and noted limitations, including interobserver variability in interpretation. Additional tests, such as basic cardiac biomarkers, cardiac imaging, gene expression profiling (GEP) scores, donor-derived cell-free DNA (dd-cfDNA) and the novel molecular microscope diagnostic system (MMDx) have become critical tools in rejection surveillance beyond standard EMB.

METHODS

This paper describes an illustrative case followed by a review of MMDx within the context of other noninvasive screening modalities for rejection.

CONCLUSIONS

We suggest MMDx be used to assist with early detection of rejection in cases of discordance between EMB and other noninvasive studies.

Diagnostic accuracy of brain natriuretic peptide and N-terminal-pro brain natriuretic peptide to detect complications of cardiac transplantation in adults: A systematic review and meta-analysis

BACKGROUND

We aimed to evaluate the utility of BNP and NT-proBNP in identifying adverse recipient outcomes following cardiac transplantation.

METHODS

We searched MEDLINE (Ovid), Embase (Ovid), and the Cochrane Library from inception to February 2023. We included studies reporting associations between BNP or NT-proBNP and adverse outcomes following cardiac transplantation in adults. We calculated standardised mean differences (SMD) with 95% confidence intervals (CI); or confusion matrices with sensitivities and specificities. Where meta-analysis was inappropriate, studies were analysed descriptively.

RESULTS

Thirty-two studies involving 2,297 cardiac transplantation recipients were included. We report no significant association between BNP or NT-proBNP and significant acute cellular rejection of grade 3A or higher (SMD 0.40, 95% CI -0.06-0.86) as defined by the latest 2004 International Society for Heart and Lung Transplantation Guidelines. We also report no strong associations between BNP or NT-proBNP and cardiac allograft vasculopathy or antibody mediated rejection.

CONCLUSION

In isolation, serum BNP and NT-proBNP lack sufficient sensitivity and specificity to reliably predict adverse outcomes following cardiac transplantation.

Cardiac Allograft Rejection Induces Changes in Nucleocytoplasmic Transport: RANGAP1 as a Potential Non-Invasive Biomarker

The non-invasive diagnosis of acute cellular rejection (ACR) is a major challenge. We performed a molecular study analyzing the predictive capacity of serum RanGTPase AP1 (RANGAP1) for diagnosing ACR during the first year after heart transplantation (HT). We included the serum samples of 75 consecutive HT patients, extracted after clinical stability, to determine the RANGAP1 levels through ELISA. In addition, various clinical, analytical, and echocardiographic variables, as well as endomyocardial biopsy results, were collected. RANGAP1 levels were higher in patients who developed ACR (median 63.15 ng/mL; (inter-quartile range (IQR), 36.61–105.69) vs. 35.33 ng/mL (IQR, 19.18–64.59); p = 0.02). Receiver operating characteristic (ROC) curve analysis confirmed that RANGAP1 differentiated between patients with and without ACR (area under curve (AUC), 0.70; p = 0.02), and a RANGAP1 level exceeding the cut-off point (≥90 ng/mL) was identified as a risk factor for the development of ACR (OR, 6.8; p = 0.006). Two independent predictors of ACR identified in this study were higher RANGAP1 and N-terminal pro-brain natriuretic peptide levels. The analysis of the ROC curve of the model showed a significant AUC of 0.77, p = 0.001. Our findings suggest that RANGAP1 quantification facilitates risk prediction for the occurrence of ACR and could be considered as a novel non-invasive biomarker of ACR.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The evolution of patient-specific precision biomarkers to guide personalized heart-transplant care

Introduction

In parallel to the clinical maturation of heart transplantation over the last 50 years, rejection testing has been revolutionized within the systems biology paradigm triggered by the Human Genome Project.

Areas Covered

We have co-developed the first FDA-cleared diagnostic and prognostic leukocyte gene expression profiling biomarker test in transplantation medicine that gained international evidence-based medicine guideline acceptance to rule out moderate/severe acute cellular cardiac allograft rejection without invasive endomyocardial biopsies. This work prompted molecular re-classification of intragraft biology, culminating in the identification of a pattern of intragraft myocyte injury, in addition to acute cellular rejection and antibody-mediated rejection. This insight stimulated research into non-invasive detection of myocardial allograft injury. The addition of a donor-organ specific myocardial injury marker based on donor-derived cell-free DNA further strengthens the non-invasive monitoring concept, combining the clinical use of two complementary non-invasive blood-based measures, host immune activity-related risk of acute rejection as well as cardiac allograft injury.

Expert Opinion

This novel complementary non-invasive heart transplant monitoring strategy based on leukocyte gene expression profiling and donor-derived cell-free DNA that incorporates longitudinal variability measures provides an exciting novel algorithm of heart transplant allograft monitoring. This algorithm's clinical utility will need to be tested in an appropriately designed randomized clinical trial which is in preparation.

Usefulness of speckle tracking echocardiography and biomarkers for detecting acute cellular rejection after heart transplantation

BACKGROUND

Acute cellular rejection (ACR) is a major complication after heart transplantation. Endomyocardial biopsy (EMB) remains the gold standard for its diagnosis, but it has concerning complications. We evaluated the usefulness of speckle tracking echocardiography (STE) and biomarkers for detecting ACR after heart transplantation.

METHODS

We prospectively studied 60 transplant patients with normal left and right ventricular systolic function who underwent EMB for surveillance 6 months after transplantation. Sixty age- and sex-matched healthy individuals constituted the control group. Conventional echocardiographic parameters, left ventricular global longitudinal, radial and circumferential strain (LV-GLS, LV-GRS and LV-GCS, respectively), left ventricular systolic twist (LV-twist) and right ventricular free wall longitudinal strain (RV-FWLS) were analyzed just before the procedure. We also measured biomarkers at the same moment.

RESULTS

Among the 60 studied patients, 17 (28%) had severe ACR (grade ≥ 2R), and 43 (72%) had no significant ACR (grade 0 - 1R). The absolute values of LV-GLS, LV-twist and RV-FWLS were lower in transplant patients with ACR degree ≥ 2 R than in those without ACR (12.5% ± 2.9% vs 14.8% ± 2.3%, p=0.002; 13.9° ± 4.8° vs 17.1° ± 3.2°, p=0.048; 16.6% ± 2.9% vs 21.4%± 3.2%, p < 0.001; respectively), while no differences were observed between the LV-GRS or LV-GCS. All of these parameters were lower in the transplant group without ACR than in the nontransplant control group, except for the LV-twist. Cardiac troponin I levels were significantly higher in patients with significant ACR than in patients without significant ACR [0.19 ng/mL (0.09-1.31) vs 0.05 ng/mL (0.01-0.18), p=0.007]. The combination of troponin with LV-GLS, RV-FWLS and LV-Twist had an area under curve for the detection of ACR of 0.80 (0.68-0.92), 0.89 (0.81-0.93) and 0.79 (0.66-0.92), respectively.

CONCLUSION

Heart transplant patients have altered left ventricular dynamics compared with control individuals. The combination of troponin with strain parameters had higher accuracy for the detection of ACR than the isolated variables and this association might select patients with a higher risk for ACR who will benefit from an EMB procedure in the first year after heart transplantation.

Predictive Parameters of Decreased Left Ventricular Global Longitudinal Strain at 1 Month After Pediatric Heart Transplantation

Previous reports indicate that the decreased left ventricular global longitudinal strain (LVGLS) seen in the early postoperative period of pediatric heart transplant patients generally recovers over the course of 1-2 years. In this study, we investigate the predictive capacity of preoperative parameters on the LVGLS decline seen at 1 month post transplant. Forty-six transplant subjects with 2D echocardiographic images sufficient for speckle tracking echocardiography were enrolled. We excluded patients diagnosed with cardiac allograft vasculopathy or with an episode of rejection 1 month before or after their echocardiographic examinations. The mean LVGLS was significantly reduced at 1 month when compared to 1 year following transplant (- 15.5% vs. - 19.4%, respectively, p < 0.001). The predictors of LVGLS that decline at 1 month were the LV mass z-score [odds ratio (OR) 1.452; 95% confidence interval (CI) 1.007-2.095, p = 0.046], recipient age (OR 1.124; 95% CI 1.015-1.245, p = 0.025), and donor age (OR 1.081; 95% CI 1.028-1.136, p = 0.002) in the univariate logistic regression analyses. Although multivariate analysis yielded no significant predictors, higher LV mass z-scores showed a trend associated with the decline of LVGLS (p = 0.087). The donor/recipient weight ratio was associated with the LV mass z-score (R² = 0.412, p < 0.001).

Noninvasive biomarkers for prediction and diagnosis of heart transplantation rejection

For most patients with end-stage heart failure, heart transplantation is the treatment of choice. Allograft rejection is one of the major post-transplantation complications affecting graft outcome and survival. Recent advancements in science and technology offer an opportunity to integrate genomic and other omics-based biomarkers into clinical practice, facilitating noninvasive evaluation of allograft for diagnostic and prognostic purposes. Omics, including gene expression profiling (GEP) of blood immune cell components and donor-derived cell-free DNA (dd-cfDNA) are of special interest to researchers. Several studies have investigated levels of dd-cfDNA and miroRNAs in blood as potential markers for early detection of allograft rejection. One of the achievements in the field of transcriptomics is AlloMap, GEP of peripheral blood mononuclear cells (PBMC), which can identify 11 differentially expressed genes and help with detection of moderate and severe acute cellular rejection in stable heart transplant recipients. In recent years, the utilization of GEP of PBMC for identifying differentially expressed genes to diagnose acute antibody-mediated rejection and cardiac allograft vasculopathy has yielded promising results. Advancements in the field of metabolomics and proteomics as well as their potential implications have been further discussed in this paper.

Non-invasive cardiac allograft rejection surveillance: reliability and clinical value for prevention of heart failure

Allograft rejection-related acute and chronic heart failure (HF) is a major cause of death in heart transplant recipients. Given the deleterious impact of late recognized acute rejection (AR) or non-recognized asymptomatic antibody-mediated rejection on short- and long-term allograft function improvement of AR surveillance and optimization of action strategies for confirmed AR can prevent AR-related allograft failure and delay the development of cardiac allograft vasculopathy, which is the major cause for HF after the first posttransplant year. Routine non-invasive monitoring of cardiac function can improve both detection and functional severity grading of AR. It can also be helpful in guiding the anti-AR therapy and timing of routine surveillance endomyocardial biopsies (EMBs). The combined use of EMBs with non-invasive technologies and methods, which allow detection of subclinical alterations in myocardial function (e.g., tissue Doppler imaging and speckle-tracking echocardiography), reveal alloimmune activation (e.g., screening of complement-activating donor-specific antibodies and circulating donor-derived cell-free DNA) and help in predicting the imminent risk of immune-mediated injury (e.g., gene expression profiling, screening of non-HLA antibodies, and circulating donor-derived cell-free DNA), can ensure the best possible surveillance and management of AR. This article gives an overview of the current knowledge about the reliability and clinical value of non-invasive cardiac allograft AR surveillance. Particular attention is focused on the potential usefulness of non-invasive tools and techniques for detection and functional grading of early and late ARs in asymptomatic patients. Overall, the review aimed to provide a theoretical and practical basis for those engaged in this particularly demanding up-to-date topic.

Feasibility and interpretation of global longitudinal strain imaging in pediatric heart transplant recipients

Evaluation of myocardial mechanics after heart transplant is important in monitoring allograft function and identifying rejection. Speckle tracking global longitudinal strain (GLS) may be more sensitive to early regional changes from rejection. This study aimed to determine feasibility of GLS in pediatric hearts during surveillance echocardiograms, compare their GLS to published norms (-18% to -22%), and assess association of GLS with other indices of graft function. Retrospective review of transplant echocardiograms from 2013 to 2014. Philips QLAB was used for post-acquisition GLS analysis. Multiple linear regression was used to assess the association of GLS with echocardiographic/catheterization indices, and B-type natriuretic peptide (BNP). Forty-seven patients (84 studies) were included. Calculation of GLS was feasible in 82 studies (97%) with inter- and intra-observer variability of 0.71 and 0.69. Patients (n=9) with rejection had GLS of -16.4% (SD=3.5%) compared to those without [-16.8% (SD=3.7%)]. GLS worsened linearly with increasing Ln(BNP) (P=<.001), left ventricular volume in diastole (P=<.001), septal a' wave (P=<.001), and pulmonary capillary wedge pressure (P=<.001). Speckle tracking-based GLS is feasible and reproducible in pediatric heart recipients and is reduced at baseline. The role of GLS and BNP in detecting early systolic dysfunction warrants further investigation.

Brain natriuretic peptide and right heart dysfunction after heart transplantation

Heart transplantation (HT) should normalize cardiac endocrine function, but brain natriuretic peptide (BNP) levels remain elevated after HT, even in the absence of left ventricular hemodynamic disturbance or allograft rejection. Right ventricle (RV) abnormalities are common in HT recipients (HTx), as a result of engraftment process, tricuspid insufficiency, and/or repeated inflammation due to iterative endomyocardial biopsies. RV function follow-up is vital for patient management as RV dysfunction is a recognized cause of in-hospital death and is responsible for a worse prognosis. Interestingly, few and controversial data are available concerning the relationship between plasma BNP levels and RV functional impairment in HTx. This suggests that infra-clinical modifications, such as subtle immune system disorders or hypoxic conditions, might influence BNP expression. Nevertheless, due to other altered circulating molecular forms of BNP, a lack of specificity of BNP assays is described in heart failure patients. This phenomenon could exist in HT population and could explain elevated BNP plasmatic levels despite a normal RV function. In clinical practice, intra-individual change in BNP over time, rather than absolute BNP values, might be more helpful in detecting right cardiac dysfunction in HTx.

Novel Biomarker Approaches for Managing Patients With Cardiac Transplantation

Despite major advances in the medical care of patients following heart transplantation (HTx) and a steady increase in long-term survival, allograft surveillance is still based on endomyocardial biopsy, the gold standard since the 1970s. This invasive procedure calls for less burdening and more cost-effective approaches. In recent years, impressive progress has been made in utilizing blood-based biomarkers for the diagnosis and management of diseases in a variety of fields. Hence, a number of trials have been performed testing the usefulness of circulating molecules or other technical methods to overcome the need for surveillance myocardial biopsy in HTx patients. Here, we review current approaches and the state of research on novel biomarkers for the management of patients following heart transplantation.

Biomarkers of acute rejection following cardiac transplantation

Cardiac transplantation can be a life-saving treatment for selected patients with heart failure. However, despite advances in immunosuppressive therapy, acute allograft rejection remains a significant cause of morbidity and mortality. The current 'gold standard' for rejection surveillance is endomyocardial biopsy, which aims to identify episodes of rejection prior to development of clinical manifestations. This is an invasive technique with a risk of false-positive and false-negative results. Consequently, a wide variety of noninvasive alternatives have been investigated for their potential role as biomarkers of rejection. This article reviews the evidence behind proposed alternatives such as imaging techniques, electrophysiological parameters and peripheral blood markers, and highlights the potential future role for biomarkers in cardiac transplantation as an adjunct to biopsy.

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.

Diagnostic performance of cardiac magnetic resonance for the detection of acute cardiac allograft rejection: a systematic review and meta-analysis

BACKGROUND

Several studies have addressed the diagnostic accuracy of cardiac magnetic resonance (CMR) to assess acute cardiac allograft rejection (ACAR) compared with endomyocardial biopsy (EMB). But the methodological heterogeneity limited the clinical application of CMR. Accordingly, we have sought a comprehensive, systematic literature review and meta-analysis for the purpose.

METHODS

Studies prior to September 1, 2014 identified by Medline/PubMed, EMBASE and Cochrance search and citation tracking were examined by two independent reviewers. A study was included if a CMR was used as a diagnostic test for the detection of ACAR.

RESULTS

Of the seven articles met the inclusion criteria. Only four studies using T2 relaxation time as a CMR parameter could be pooled results, because the number of studies using other parameters was less than three. By using DerSimonian-Laird random effects model, meta-analysis demonstrated a pooled sensitivity of 90% [95% confidence interval (CI), 79% to 97%], a pooled specificity of 83% (95% CI, 78% to 88%), and a pooled diagnostic odds ratio (DOR) of 61.66 (95% CI, 18.09 to 210.10).

CONCLUSIONS

CMR seems to have a high sensitivity and moderate specificity in the diagnosis of ACAR. However, as a result of CMR for diagnostic ACAR should be comprehensively considered by physicians and imaging experts in the context of clinical presentations and imaging feature. Further investigations are still required to test different parameters and study condition.

Changes in serial B-type natriuretic peptide level independently predict cardiac allograft rejection

BACKGROUND

Despite positive associations with rejection, the clinical value of B-type natriuretic peptide (BNP) monitoring in heart transplant recipients has not been established. We sought to determine the predictive value of changes in serial BNP level for identifying patients with acute allograft rejection.

METHODS

BNP, hemodynamics and biopsies were obtained for 205 transplant recipients who underwent a total of 4,007 endomyocardial biopsy procedures. Samples analyzed were collected ≥ 180 days post-transplant, without evidence of rejection on the immediately preceding biopsy. Using a repeated-measures multivariate model, we assessed the association of change in BNP with Grade ≥ 3A (2R) rejection. We also determined predictive values of various cut-off thresholds of change in serial BNP levels to predict Grade ≥ 3A rejection.

RESULTS

There were 47 episodes of Grade ≥ 3A rejection among the 1,350 samples analyzed. Median change in serial BNP (ΔBNP) for those with Grade ≥ 3A rejection was 20 pg/ml (IQR -26 to 169 pg/ml) and among those with Grade <3A rejection was -4 pg/ml (IQR -34 to 22 pg/ml, p = 0.003). On multivariate analysis, ΔBNP remained the most potent independent predictor of Grade ≥ 3A rejection (p = 0.001). ΔBNP >100 pg/ml predicted increased risk of Grade ≥ 3A rejection (OR = 5.3, p < 0.001) with high specificity (93.3%) and positive predictive value (13.0%) and excellent negative predictive value (97.3%).

CONCLUSIONS

Change in serial BNP level is an independent predictor of cardiac allograft rejection. With wide availability, rapid turnaround, low cost, favorable positive predictive value and excellent negative predictive value, serial BNP monitoring has several advantages for non-invasive monitoring of heart transplant recipients for acute cardiac allograft rejection.