Radioimmunometric assay of B-type natriuretic peptide (BNP) in heart transplantation: correlation between BNP determinations and biopsy grading of rejection

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.

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.

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.

Brain natriuretic peptide induces CD8+ T cell death via a caspase 3 associated pathway--implications following heart transplantation

BACKGROUND

Brain natriuretic peptide (BNP) remains elevated after cardiac transplantation despite replacement of the failing ventricle. Serum peaks are also seen during acute rejection episodes independent of intracardiac hemodynamic disturbance. High BNP levels are also reported during bacterial sepsis, burns, stroke and myocardial infarction. Given all of these conditions are linked by immune activation processes, we hypothesised that BNP is an immunoactive agent.

METHODS

Peripheral blood mononuclear cells (PBMCs) were isolated from whole blood of 40 cardiac transplant recipients. Cells were co-cultured for 72h in the presence or absence of BNP. Cells were then immunophenotyped using flow cytometry. Cell death pathways were determined using caspase 3 quantification and mitochondrial membrane assessment. Supernatants were analysed for cytokine, chemokine and growth factor production using luminex.

RESULTS

Co-culture of CD8+ T cells with BNP reduced cell number, and increased intracellular caspase 3. Supernatant analysis revealed that BNP reduced the expression of inflammatory cytokines including TNF-α, IL-1α and IL-6. However it preserved the production of anti-inflammatory and regulatory cytokines such as IL-4, 5 and 13.

CONCLUSION

Our findings provide evidence that BNP directly induces CD8+ T cell apoptosis via a caspase 3 associated mechanism from cardiac transplant patients. This may impart significant consequences on immune mediated disease processes, such as allograft rejection.

Screening for rejection in symptomatic pediatric heart transplant recipients: the sensitivity of BNP

As the pediatric OHT population expands, there is increasing demand for convenient, yet sensitive screening techniques to identify children with acute rejection when they present to acute care facilities. In children, symptoms of acute rejection or other causes of graft dysfunction are often non-specific and can mimic other childhood illnesses. The aim of this study was to assess the utility of BNP as a biomarker to assist providers in clinical decision-making when evaluating symptomatic pediatric heart transplant patients. One hundred twenty-two urgent care and emergency room visits from 53 symptomatic pediatric OHT patients were retrospectively reviewed to evaluate the relationship between BNP levels, symptoms, and clinical diagnosis at these visits. An ROC curve was generated to determine the accuracy of BNP as a screening tool for acute rejection in this patient population. In this group of patients, a BNP value of >700 pg/mL was 100% sensitive and 92% specific for detecting allograft acute rejection (NPV of 100%). We concluded that BNP is a highly sensitive screening test for acute rejection in symptomatic pediatric heart transplant patients.

Determinants of brain natriuretic peptide gene expression and secretion in acute cardiac allograft rejection

PURPOSE OF REVIEW

Circulating levels of the cardiac hormone brain natriuretic peptide in heart transplant patients may increase before and during an acute rejection episode. A similar increase in atrial natriuretic factor does not occur. This article reviews the possible significance of these findings.

RECENT FINDINGS

During acute cardiac allograft rejection episodes, brain natriuretic peptide plasma levels may increase well above baseline values. This increase is not the result of hemodynamic changes because brain natriuretic peptide levels during International Society for Heart and Lung Transplantation grade 3 rejection do not correlate with various hemodynamic parameters, and atrial natriuretic factor levels are not affected. Similar results were observed in experimentally induced autoimmune myocarditis. In-vitro data showed that some proinflammatory cytokines and chemokines are capable of selectively increasing brain natriuretic peptide gene expression and secretion in cardiocyte cultures.

SUMMARY

Atrial natriuretic factor and brain natriuretic peptide are usually co-regulated. Findings in heart allograft recipients, in experimentally induced myocarditis, and in vitro suggest that, unlike atrial natriuretic factor, brain natriuretic peptide is uniquely related to inflammation. These findings may translate into biomarkers or therapies for cardiac allograft rejection or myocarditis and may explain the existence of two hormones with nearly identical biologic properties.

Is there a correlation between brain naturietic peptide levels and echocardiographic and hemodynamic parameters in heart transplant patients?

BACKGROUND

Brain naturietic peptide (BNP) elevations have been reported in heart transplant patients both at baseline and during rejection. An association between BNP levels and certain echocardiographic and hemodynamic abnormalities has also been found in nontransplanted heart disease patients. We sought to determine whether BNP values were correlated with echocardiographic and hemodynamic parameters among a large cohort of heart transplant patients.

MATERIALS AND METHODS

We studied 71 consecutive heart transplant patients, excluding combined grafts, retransplants, and pediatric cases. We performed 488 BNP determinations during catheterization and within 48 hours of echocardiography. Hemodynamic parameters included mean pulmonary artery pressure, right ventricular systolic and diastolic pressures. Doppler echocardiography parameters were wall thickness, ventricular mass, left and right ventricular end-diastolic and end-systolic diameters, isovolumic relaxation time, and mitral flow deceleration time.

RESULTS

We observed significant correlations between BNP values and left ventricular size, ventricular mass, and a restrictive filling pattern. BNP levels were also significantly correlated with right ventricular size, mean pulmonary artery pressure, and right ventricular diastolic and end-diastolic pressures.

CONCLUSIONS

In heart transplant patients, BNP levels positively correlated with ventricular diameters and a restrictive filling pattern. An increase in right ventricle and pulmonary artery pressures was associated with elevated BNP values.

B-type natriuretic peptide concentrations and myocardial dysfunction in critical illness

B-type natriuretic peptide (BNP) is the first biomarker of proven value in screening for left ventricular dysfunction. The availability of point-of-care testing has escalated clinical interest and the resultant research is defining a role for BNP in the investigation and treatment of critically ill patients. This review was undertaken with the aim of collecting and assimilating current evidence regarding the use of BNP assay in the evaluation of myocardial dysfunction in critically ill humans. The information is presented in a format based upon organ system and disease category. BNP assay has been studied in a spectrum of clinical conditions ranging from acute dyspnoea to subarachnoid haemorrhage. Its role in diagnosis, assessment of disease severity, risk stratification and prognostic evaluation of cardiac dysfunction appears promising, but requires further elaboration. The heterogeneity of the critically ill population appears to warrant a range of cut-off values. Research addressing progressive changes in BNP concentration is hindered by infrequent assay and appears unlikely to reflect the critically ill patient's rapidly changing haemodynamics. Multi-marker strategies may prove valuable in prognostication and evaluation of therapy in a greater variety of illnesses. Scant data exist regarding the use of BNP assay to alter therapy or outcome. It appears that BNP assay offers complementary information to conventional approaches for the evaluation of cardiac dysfunction. Continued research should augment the validity of BNP assay in the evaluation of myocardial function in patients with life-threatening illness.

Neuroendocrine profiling of humans receiving cardiac allografts

BACKGROUND

Several studies have investigated changes in circulating hormones and markers of cardiac status after heart transplantation in humans. As a result, plasma levels of various hormones and autocoids have been associated with cardiac allograft rejection status. However, no clear associations can be defined given the highly contradictory nature of the available literature.

METHODS

In this study of 69 consecutive heart transplant patients followed for >2 years we examine the relationship between neurohumors potentially related to allograft rejection and endomyocardial biopsy grade of rejection (according to the ISHLT) and hemodynamic status. Markers assessed include brain natriuretic peptide (BNP), amino-terminal pro-BNP (N-BNP), atrial natriuretic factor (ANF), adrenomedullin, interleukin-1beta, interleukin-6, tumor necrosis factor-alpha, troponin C and C-reactive protein.

RESULTS

The highest plasma levels for most neurohumors were found shortly after surgery and showed a trend towards normalization with time. BNP and N-BNP were the only significantly elevated plasma analytes for patients with Grade 3 rejection as compared with other ISHLT grades. ANF plasma levels correlated with BNP and N-BNP in Grades 0 to 2, but not in Grade 3, suggesting that in this rejection grade the usual coordinated changes observed in BNP and ANF secretion no longer exist. Cardiac filling pressures were correlated with plasma BNP, N-BNP and ANF levels only for Grades 0 and 1.

CONCLUSIONS

The timing of blood sampling after transplantation influences the level of the neurohumors measured, which may help explain the conflicting literature reports on the association between neurohumor levels and rejection grade. The significant increase in circulating levels of BNP and N-BNP observed in most cases of Grade 3 rejection occurred with no apparent relationship to post-transplantation time, which suggests a specific influence of acute rejection on BNP gene expression.

B-Type Natriuretic Peptide as a Marker of Allograft Rejection After Heart Transplantation

B-type natriuretic peptide (BNP) concentrations, a cardiac hormone released upon cardiac stress, was monitored in patients after heart transplantation. Rejection was assessed by the International Society for Heart and Lung Transplantation (ISHLT) criteria. BNP was assessed by a cross-sectional approach. We found significantly (p = 0.024) increased concentrations during rejection episodes of ISHLT grade 2 and higher. BNP yielded only a moderate diagnostic accuracy (area under the receiving characteristic curve: mean = 0.76, 95% confidence interval 0.53-0.92) to detect clinically significant episodes of rejection, which was too low to replace endomyocardial biopsies. Acute rejection episodes were associated with marked BNP increases and a significant decrease in case of successful treatment in the individual long-term monitoring in the majority of patients. BNP monitoring seems to be a useful addition in the individual follow-up of heart transplant recipients to rule out significant rejection.

Tricuspid Regurgitation After Cardiac Transplantation: How Many Biopsies Are Too Many?

BACKGROUND

Tricuspid regurgitation (TR) is common in patients after orthotopic cardiac transplantation (OHT). Endomyocardial biopsy (EMB) used to monitor for rejection may be a cause of TR. The purpose of this study was to identify a correlation between the severity of TR and the number of EMBs.

METHODS

We studied 101 patients with OHT at our institution between May 1987 and August 2001. The number of EMBs performed in each patient was determined. Data on technique of anastomosis, liver and renal function, ejection fraction, and pulmonary artery pressure were also extracted. Echocardiography reports were reviewed to determine the presence and severity of TR. Symptoms of right heart failure were assessed by the amount of diuretic intake.

RESULTS

Twenty-five (25%) of 101 patients had evidence of severe TR, whereas 76 (75%) had non-severe TR. Multivariate analysis identified EMB as the only independent predictor of the severity of TR (p < 0.0001). At last follow-up, 60% of patients with more than 31 EMBs had developed severe TR, whereas none of the patients with less than 18 EMBs had severe TR. Of the 25 patients who had severe TR, 15 (61%) needed high doses of daily diuretics, and 4 (16%) required tricuspid valve replacement.

CONCLUSIONS

The development of TR after OHT is in large part due to EMBs used to monitor for rejection. There is a direct correlation between the number of EMBs and the severity of TR. We suggest a cutoff of less than 31 EMBs to reduce the risk of severe TR.

Cardiac natriuretic peptides for cardiac health

The cardiac natriuretic peptides, ANP (atrial natriuretic peptide) and BNP (brain natriuretic peptide), are secreted by the heart in proportion to cardiac transmural pressures. They possess a wide range of effects in multiple tissues facilitating overall pressure/volume homoeostasis. The close relationship between plasma concentrations of these peptides and 'cardiac load' has led to their use as biomarkers of cardiac health with diagnostic and prognostic applications in a variety of disorders affecting the cardiovascular system. BNP and its N-terminal fragment (NT-BNP) are especially sensitive indicators of cardiac dysfunction and remodelling, and correlate strongly with severity. Given that cardiac ischaemia is also an important trigger for the release of these ventricular peptides, they may likewise play a role in the detection of coronary artery disease. Measurement of BNP/NT-BNP shows particular promise as a 'rule out' test for suspected cases of HF (heart failure) in both emergency care and outpatient settings, and may assist in identifying individuals with asymptomatic ventricular impairment who will benefit from therapy preventing progression to overt HF. The BNP peptides also predict subsequent haemodynamic deterioration and adverse events in cardiovascular disease, and can therefore be used to monitor those at high risk and act as a guide to optimization of treatment. The favourable biological properties of the natriuretic peptides have also led to their use as therapeutic agents.

Natriuretic peptides BNP and NT-pro-BNP: established laboratory markers in clinical practice or just perspectives?

A growing body of literature describes diagnostic and prognostic value of B-type natriuretic peptides (BNP) in cardiac diseases since it was first described in 1988. As BNP is mainly secreted in the left ventricular (LV) myocardium, BNP was found to reflect LV function much better than any other neurohumoral factor. Thus, BNP is recommended as the first noninvasive blood test for determination of cardiac function by some authors. The introduction of fully automated, rapid bioassays for measurement of BNP and the aminoterminal part of its pro-hormone (NT-pro-BNP) made it possible to use the test even in emergency care settings. Here we review the literature with special focus on assessment of BNP and NT-pro-BNP in the following clinical settings: community screening for LV dysfunction, primary diagnosis of heart failure in general practice and emergency department (ED) and risk stratification in cardiac dysfunction and acute coronary syndromes. In addition, we discuss which applications can be recommended for daily clinical use from the cardiologist's point of view.