Predictive value of brain natriuretic peptide in the diagnosis of heart transplant rejection

European Society for Organ Transplantation (ESOT) Consensus Statement on the Use of Non-invasive Biomarkers for Cardiothoracic Transplant Rejection Surveillance

While allograft rejection (AR) continues to threaten the success of cardiothoracic transplantation, lack of accurate and repeatable surveillance tools to diagnose AR is a major unmet need in the clinical management of cardiothoracic transplant recipients. Endomyocardial biopsy (EMB) and transbronchial biopsy (TBBx) have been the cornerstone of rejection monitoring since the field's incipience, but both suffer from significant limitations, including poor concordance of biopsy interpretation among pathologists. In recent years, novel molecular tools for AR monitoring have emerged and their performance characteristics have been evaluated in multiple studies. An international working group convened by ESOT has reviewed the existing literature and provides a series of recommendations to guide the use of these biomarkers in clinical practice. While acknowledging some caveats, the group recognized that Gene-expression profiling and donor-derived cell-free DNA (dd-cfDNA) may be used to rule out rejection in heart transplant recipients, but they are not recommended for cardiac allograft vasculopathy screening. Other traditional biomarkers (NT-proBNP, BNP or troponin) do not have sufficient evidence to support their use to diagnose AR. Regarding lung transplant, dd-cfDNA could be used to rule out clinical rejection and infection, but its use to monitor treatment response is not recommended.

A gentler approach to monitor for heart transplant rejection

Despite developments in circulating biomarker and imaging technology in the assessment of cardiovascular disease, the surveillance and diagnosis of heart transplant rejection has continued to rely on histopathologic interpretation of the endomyocardial biopsy. Increasing evidence shows the utility of molecular evaluations, such as donor-specific antibodies and donor-derived cell-free DNA, as well as advanced imaging techniques, such as cardiac magnetic resonance imaging, in the assessment of rejection, resulting in the elimination of many surveillance endomyocardial biopsies. As non-invasive technologies in heart transplant rejection continue to evolve and are incorporated into practice, they may supplant endomyocardial biopsy even when rejection is suspected, allowing for more precise and expeditious rejection therapy. This review describes the current and near-future states for the evaluation of heart transplant rejection, both in the settings of rejection surveillance and rejection diagnosis. As biomarkers of rejection continue to evolve, rejection risk prediction may allow for a more personalized approach to immunosuppression.

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.

Selection and Interpretation of Molecular Diagnostics in Heart Transplantation

The number of heart transplants performed annually in the United States and worldwide continues to increase, but there has been little change in graft longevity and patient survival over the past 2 decades. The reference standard for diagnosis of acute cellular and antibody-mediated rejection includes histologic and immunofluorescence evaluation of endomyocardial biopsy samples, despite invasiveness and high interrater variability for grading histologic rejection. Circulating biomarkers and molecular diagnostics have shown substantial predictive value in rejection monitoring, and emerging data support their use in diagnosing other posttransplant complications. The use of genomic (cell-free DNA), transcriptomic (mRNA and microRNA profiling), and proteomic (protein expression quantitation) methodologies in diagnosis of these posttransplant outcomes has been evaluated with varying levels of evidence. In parallel, growing knowledge about the genetically mediated immune response leading to rejection (immunogenetics) has enhanced understanding of antibody-mediated rejection, associated graft dysfunction, and death. Antibodies to donor human leukocyte antigens and the technology available to evaluate these antibodies continues to evolve. This review aims to provide an overview of biomarker and immunologic tests used to diagnose posttransplant complications. This includes a discussion of pediatric heart transplantation and the disparate rates of rejection and death experienced by Black patients receiving a heart transplant. This review describes diagnostic modalities that are available and used after transplant and the landscape of future investigations needed to enhance patient outcomes after heart transplantation.

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.

Assessment of Acute Rejection by Global Longitudinal Strain and Cardiac Biomarkers in Heart-Transplanted Patients

Aims

The aim of this study was to evaluate left ventricular global longitudinal strain (LVGLS), N-terminal pro brain natriuretic peptide (Nt-ProBNP), and Troponin T as non-invasive markers for acute cellular rejection (ACR) diagnosis and severity assessment after heart transplantation (HTx).

Methods

We retrospectively included all HTx patients transplanted from 2013 to 2019. At each visit, the patients were subjected to endomyocardial biopsy (EMB), measurement of Nt-ProBNP and Troponin T, and protocoled echocardiography with assessment of LVGLS. Sudden drop in graft function (SDGF) was defined as a drop in LVGLS ≥-2% in combination with either an increase in Troponin T ≥20% or Nt-ProBNP ≥30% compared with levels at the latest visit.

Results

We included 1,436 EMBs from 83 HTx patients. The biopsies were grouped as 0R (n = 857), 1R (n = 538), and ≥2R (n = 41). LVGLS was lower and Troponin T and Nt-ProBNP higher in the 2R group than in the 0R and 1R groups (LVGLS: -12.9 ± 3.8% versus -16.9 ± 3.1% and -16.1 ± 3.3%; Troponin T: 79 [33;230] ng/l versus 27 [13;77] ng/l and 27 [14;68] ng/l; Nt-ProBNP: 4,174 [1,095;9,510] ng/l versus 734 [309;2,210] ng/l and 725 [305;2,082], all p < 0.01). A SDGF was seen at 45 visits of which 19 had ≥2R ACR. EMBs showed ACR in 20 cases without SDGF. Finally, neither was SDGF seen nor did the EMB show rejection in 1,136 cases. Thus, the sensitivity of SDGF for ≥2R ACR detection was 49% (32–65) and specificity 98% (97–99). The positive predictive value (PPV) was 42% (31–55) and the negative predictive value (NPV) 98% (98–99). The diagnostic value improved in a sub-analysis excluding EMBs within 3 months after HTx, clinically interpreted false positive ≥2R ACR cases, and cases with ≥2R ACR who recently (<2 weeks) were treated with intravenous methylprednisolone due to ≥2R ACR (sensitivity 75% (48–93), specificity 97% (96–98), NPV 99% (99–100), and PPV 39% (27–52).

Conclusions

Patients with ≥2R ACR have lower LVGLS and higher Troponin T and Nt-ProBNP than patients without 2R rejection. A non-invasive model combining changes in LVGLS and Troponin T or Nt-ProBNP showed excellent negative predictive value and moderate sensitivity and may be used as a gatekeeper to invasive biopsies after HTx.

Serum biomarkers of acute rejection: Towards precision medicine in heart transplant

Despite the important changes in the management of heart transplantation in the recent decades, the use of endomyocardial biopsy is still necessary for the follow-up of these patients. However, this technique has several limitations, the most important being the substantial interobserver variability. In the last years multiple attempts have been made to find non-invasive assays for cardiac allograft surveillance, such as imaging modalities and serum biomarkers. This state-of-the-art review focuses on describing the different serum biomarkers that have been proposed for non-invasive diagnosis of acute rejection and that are paving the way towards precision medicine in the field of heart transplantation.

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.

Brain natriuretic Peptide production and secretion in inflammation

Gene expression and secretion of the cardiac polypeptide hormones atrial natriuretic factor (ANF) and brain natriuretic peptide (BNP) are simultaneously upregulated in various cardiac disorders such as congestive heart failure, ischemic heart disease, and hypertensive heart disease, in which hemodynamic or neuroendocrine changes are key components in the progression of disease. However, during acute cardiac allograft rejection, plasma BNP levels are increased but not those of ANF. Successful treatment of the rejection episode decreases the elevated plasma BNP to prerejection values suggesting that substances related to inflammation may selectively influence BNP gene expression. Indeed, cytokines such as TNFα and IL-1β selectively stimulate cardiac BNP at the transcriptional and translational levels in cardiomyocyte cultures without affecting ANF. This selective BNP increase is seen in vivo, in addition to acute cardiac allograft rejection, in several circumstances where inflammation significantly contributes to the pathogenesis of disease such as in sepsis and in acute myocarditis.

Serum markers of apoptosis in the early period of heart transplantation

CONTEXT AND OBJECTIVE

To assess the relationship between levels of serum markers of apoptosis and rejection grades in heart transplant (HTx).

MATERIALS AND METHODS

A prospective study was conducted in 91 HTx. We correlated apoptosis markers and biopsy samples. The apoptosis markers were: TRAIL, TRAIL-R1, TRAIL-R2, TRAIL-R3, TRAIL-R4, sFas, sTNF-R1 and sTNF-R2.

RESULTS

The only significant correlation with rejection grade was sFas (r=0.329; p=0.005). Cyclosporine showed a proapoptotic effect (sTNF-R1 0.02 and sTNF-R2 0.02) and everolimus an antiapoptotic effect (sTNF-R1 r= -0.523; p=0.0001 and sTNF-R2 r= -0.405; p=0.0001).

CONCLUSIONS

The utility of specific apoptosis markers in peripheral blood for diagnosis of acute cellular rejection is low. Everolimus may have an anti-apoptotic effect.

Endocrine heart after lung transplantation: increased brain natriuretic peptide is related to right ventricular function

Brain natriuretic peptide (BNP) increases in proportion to the extent of right ventricular dysfunction in pulmonary hypertension and after heart transplantation. No data are available after lung transplantation. Clinical, biological, respiratory, echocardiographic characteristics and circulating BNP and its second messenger cyclic guanosine monophosphate (cGMP) were determined in thirty matched subjects (10 lung-, 10 heart-transplant recipients (Ltx, Htx) and 10 healthy controls). Eventual correlations between these parameters were investigated. Heart rate and pulmonary arterial blood pressure were slightly increased after transplantation. Creatinine clearance was decreased. Mean of forced expiratory volume in 1 s was 76.6 +/- 5.3% and vital capacity was 85.3 +/- 6.4% of the predicted values in Ltx. BNP was similarly increased in Ltx and Htx, as compared with control values (54.1 +/- 14.2 and 45.6 +/- 9.2 vs. 6.2 +/- 1.8 pg/ml, respectively). Significant relationships were observed between plasma BNP and cGMP values (r = 0.62; P < 0.05 and r = 0.75; P < 0.01, in Ltx and Htx) and between BNP and right ventricular fractional shortening and tricuspid E/Ea ratio in Ltx (r = -0.75 and r = 0.93; P < 0.01, respectively). BNP is increased after lung transplantation, like after heart transplantation. The relationships observed suggest that the cardiac hormone might counterbalance possible deleterious effects of lung-transplantation on right functioning of patient's heart.

Time-dependent changes in B-type natriuretic peptide after heart transplantation: correlation with allograft rejection and function

Endomyocardial biopsy is the gold standard to diagnose cardiac allograft rejection, although a noninvasive modality such as brain natriuretic peptide (BNP) is attractive. The authors examined the correlation of BNP levels with rejection patterns and allograft function in cardiac allograft recipients followed up to 8 years. One hundred forty-four consecutive patients underwent endomyocardial biopsy, right heart catheterization, and blood sampling. BNP levels decreased during the first 6 months after transplant but then reached a plateau. Time-dependent correlations were made between BNP levels and allograft rejection, left ventricular ejection fraction, pulmonary capillary wedge pressure, right atrial pressure, and serum creatinine. BNP levels were not different between patients with any rejection pattern and no rejection prior to or after 6 months following transplant. BNP levels did not correlate with ejection fraction, pulmonary capillary wedge pressure, right atrial pressure, or creatinine in the first 6 months after transplant. Statistically significant correlations existed between BNP and these parameters after 6 months following transplant. In cardiac transplant recipients, BNP levels decrease in the first 6 months following transplant and then reach a plateau regardless of the presence, type, or severity of allograft rejection. BNP levels do predict allograft rejection but correlate with allograft function after 6 months following transplant.

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

Serum B-type natriuretic peptide (BNP) is increased after heart transplantation (HT), but it has not been well established whether BNP could be used to detect acute rejection in asymptomatic patients after HT. A total of 259 routine endomyocardial biopsy specimens from 50 consecutive patients after HT (83% men; age 50 +/- 15 years) were studied. Serial BNP measurements were performed at the time of each biopsy. BNP was evaluated as an absolute level (picograms per milliliter) and percentage of change from the previous biopsy (BNP - BNP at previous biopsy)/BNP at previous biopsy] x 100). Rejection was defined as grade > or =2R International Society of Heart and Lung Transplantation grading system. BNP correlated independently with time after HT (p <0.001), pulmonary artery systolic pressure (p <0.001), creatinine (p = 0.001), and age (p = 0.0012). Asymptomatic rejection was found in 15 biopsy specimens (6%), for which absolute BNP (106 pg/ml; interquartile range [IQR] 67 to 495) did not differ from nonrejection biopsy specimens (92 pg/ml; IQR 49 to 230; p = 0.286). BNP percentage of change showed a median of +60% (IQR -29 to +154%) in rejection versus -17% (IQR -47 to +19%) in nonrejection biopsy specimens (p = 0.009). After multivariable adjustment, BNP percentage of change was a consistent predictor of rejection (+10%; odds ratio 1.05, 95% confidence interval 1.01 to 1.09, p = 0.021). Receiver-operator characteristic analysis showed an area under the curve of 0.71 (95% confidence interval 0.643 to 0.768) and identified percentage of change <+38% as an optimal cut-off point, with a negative predictive value of 97%. In conclusion, serial monitoring of BNP, evaluated as a percentage of change, may be a useful noninvasive tool in the clinical management of rejection.

BNP directly immunoregulates the innate immune system of cardiac transplant recipients in vitro

BACKGROUND

The innate immune system plays an important role in cardiac allograft rejection. BNP has frequently been reported to elevate during acute cardiac rejection, yet the explanation behind this phenomenon is unclear. We hypothesized that BNP might interact with the innate immune system in cardiac transplant recipients and devised a series of in vitro culture experiments to explore this phenomena.

METHODS

PBMCs were isolated from whole blood of (total n = 40) cardiac transplant recipients. Short (24h, n = 20) and long term (72h, n = 20) co-cultures of innate cells in the presence or absence of BNP were performed. BNP was added at two specific concentrations and compared to placebo control. Innate cells were immunophenotyped using flow cytometry.

RESULTS

BNP dose dependently reduced the total number of monocytes, B cells and NK cells. Furthermore, BNP co-culture impaired NK cell cytotoxicity and adhesion of non-classical monocytes (via down-regulation of CD11c).

DISCUSSION

BNP has an additional physiological role of moderating components of the innate immune system. Although speculative, this could be beneficial to cardiac transplant recipients as the innate immune system is involved in allograft rejection. Further investigation is required to elucidate the mechanism behind how BNP affects immune cells and whether the same effects are consistent with the adaptive immune system.

Prognostic relationship between two serial determinations of B-type natriuretic peptide and medium-long-term events in heart transplantation

BACKGROUND

Persistent elevation of B-type natriuretic peptide (BNP) levels in the first year after transplant appears to be associated with an adverse prognosis. However, there are no data on the prognostic value of two serial determinations of BNP at the end of the first year after transplant in clinically stable patients.

OBJECTIVES

The purpose of this study was to analyze the association between the increase in two serial determinations of BNP at the end of the first year and the subsequent development of events in medium-long-term follow-up.

METHODS

An observational study was conducted in a consecutive series of 71 patients transplanted between January 1999 and January 2001. Patients who were "unstable" or had other conditions that could elevate BNP levels (rejection, elevated pulmonary pressures, renal dysfunction, depressed ventricular function or severe graft vascular disease) were also excluded. The final number of patients included was 51. BNP determinations were performed at 9 and 12 months post-transplant at the same time as biopsies. Three groups were formed depending on the relationship between the two determinations: Group 1 (20 patients), decrease >20%; Group 2 (16 patients), change <20%; and Group 3 (15 patients), increase >20%. The following were considered events: death; late rejection; and ventricular dysfunction associated or not with graft vascular disease.

RESULTS

The baseline clinical profile was similar in the three groups. There was a significant difference in the rate of events (Group 1, 10%; Group 2, 32%; Group 3, 53%; p < 0.017). Event-free survival was statistically different between the groups (p = 0.017), mainly because of the large difference between Groups 1 and 3 (p = 0.003). Thus, cumulative event-free survival at 3,000 days was 89.4% for Group 1, 68.3% for Group 2 and 48.2% for Group 3.

CONCLUSIONS

The increase between two serial determinations of BNP levels at the end of the first year post-transplant could identify a subgroup of patients with poor outcome.

B-type natriuretic peptide is a sensitive screening test for acute rejection in pediatric heart transplant patients

BACKGROUND

The utility of B-type natriuretic peptide (BNP) for detecting acute rejection (AR) is unclear. The purpose of our study was to evaluate BNP as a screening test for AR in pediatric heart transplant patients.

METHODS

All endomyocardial biopsies (EMBs) with concurrent BNP levels from February 2004 through March 2007 at the study institution were reviewed and the association between BNP levels and acute rejection was assessed.

RESULTS

Eighty-six patients underwent a total of 560 EMBs. The median age at EMB was 10.5 years (interquartile range [IQR] 3.7 to 15.4 years). There were 59 episodes of AR, 32 (54%) occurring at <1 year post-transplant. BNP levels were higher in patients with AR, median 387 pg/ml (IQR 125 to 931 pg/ml), compared with those without AR, median 66 pg/ml (IQR 37 to 148 pg/ml) (p < 0.001). The receiver operating characteristic (ROC) curve for BNP demonstrated an area under the curve (AUC) of 0.82 (95% confidence interval [CI] 0.76 to 0.88) (p < 0.001). A BNP level of 100 pg/ml corresponded to a sensitivity of 0.85 (95% CI 0.73 to 0.92) and a negative predictive value (NPV) of 0.97 (95% CI 0.95 to 0.99) for detecting AR. The ROC curve for patients at >1 year post-transplant demonstrated an AUC of 0.86 (95% CI 0.80 to 0.93) (p < 0.001), and a BNP level of 100 pg/ml corresponded to a sensitivity of 0.96 (95% CI 0.79 to 0.99) and NPV of 0.994 (95% CI 0.962 to 0.999) for detecting AR.

CONCLUSIONS

BNP levels have a high sensitivity and NPV for evaluating AR in pediatric heart transplant patients. In patients >1 year post-transplant, a BNP level of <100 pg/ml correlates with a <1% chance of AR and may obviate the need for EMB in some cases.

Does circulating BNP normalize after heart transplantation in patients with normal hemodynamic and right and left heart functions?

BACKGROUND

Increased brain natriuretic peptide (BNP) in cardiovascular disease is thought to be a compensatory protective mechanism allowing to delay the occurrence of terminal heart failure. Heart transplantation should normalize the neuroendocrine balance but BNP remains elevated in stable heart-transplant recipients (Htx). Such increase has been related to persistent endothelial and cardiac dysfunctions. The purpose of this study was to determine whether selected Htx, presenting with normal hemodynamic and cardiac systolic and diastolic functions on both side of the heart, show a normalization of their BNP plasma values.

METHODS

Of a cohort of well-being 26 Htx, we selected 12 patients with normal hemodynamics and left and right heart systolic and diastolic functions and compared their circulating BNP, cyclic guanosine monophosphate (cGMP) (the BNP second messenger) and endothelin-1 (ET) values with that of 12 age-, body mass index- and mean arterial pressure-matched controls. Cardiac function determination by echodoppler included cardiac filling pressures assessment using tissue Doppler imaging. Blood samples for biological and hormonal determinations were drawn at rest, within 15 min before echocardiography.

RESULTS

As selected, hemodynamic and left and right heart systolic and diastolic functions were located in the normal range in Htx. Plasma ET value was also similar in Htx and controls (20.7 +/- 0.9 vs. 19.6 +/- 0.9 fmol/mL). However, circulating BNP, like cGMP, was still significantly increased after heart transplantation, when compared with controls (33.8 +/- 8.5 vs. 4.0 +/- 0.9 pg/mL, p = 0.002 and 8.2 +/- 1.1 vs. 4.4 +/- 0.3 nmol/L, p = 0.003) for BNP and cGMP, respectively, in Htx and controls. Interestingly, the sole correlation observed was between BNP and cGMP (r = 0.85, p < 0.0001) after heart transplantation.

CONCLUSIONS

After heart transplantation, BNP remained increased despite the normalization of hemodynamic and cardiac systolic and diastolic functions. This suggests that such endocrine heart stimulation should not be viewed only as a hemodynamic marker in Htx. Further studies will be useful to investigate the role of pro-inflammatory cytokines and whether elevated BNP still possesses antifibrotic properties, further supporting the interest of enhancing its activity after heart transplantation.

B-type natriuretic peptides in heart failure

There is increasing interest in the B-type natriuretic peptides in many clinical settings, with most research centered on patients with heart failure. These peptides have a strong negative predictive value in patients suspected of having this diagnosis, but are also known to be powerfully predictive of an adverse outcome. This latter property is particularly important in patients with advanced heart failure, allowing the selection of at-risk individuals for therapies that are in scarce resource. There is also ongoing research into B-type natriuretic peptide as a treatment for decompensated heart failure, as well as in other clinical contexts. This review aims to summarize the contemporary and established data on the B-type natriuretic peptides, with particular emphasis in the context of advanced heart failure.

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.

Brain Natriuretic Peptide is Produced Both by Cardiomyocytes and Cells Infiltrating the Heart in Patients with Severe Heart Failure Supported by a Left Ventricular Assist Device

BACKGROUND

Brain natriuretic peptide (BNP) is a cardiac neurohormone synthesized in cardiac ventricles as a result of increased wall stress. Left ventricular assist device (LVAD) support in patients with end-stage heart failure results in reduced wall stress and therefore may change BNP levels in the heart.

METHODS

BNP plasma levels were measured in 17 patients with end-stage HF before LVAD implantation and at 1 week, 1 month, and 3 months after LVAD support. BNP-messenger RNA (mRNA) expression in cardiac biopsy specimens of 27 patients before and after LVAD support was determined by quantitative polymerase chain reaction. Immunohistochemistry (IHC) and IHC-double staining was used in biopsy specimens from 32 patients before and after LVAD support to localize the BNP protein expression in the heart.

RESULTS

BNP plasma levels significantly decreased from 1,872 +/- 1,098 pg/ml before implantation to 117 +/- 91 pg/ml at 3 months after LVAD implantation. This decrease in plasma levels was accompanied by a significant decrease in mRNA expression (relative quantity) in the heart. IHC and IHC-double staining showed BNP immunoreactivity in the cardiomyocytes, endothelial cells, infiltrating T cells, and macrophages.

CONCLUSIONS

The significant decrease in serum BNP concentration after LVAD support coincides with a decrease in BNP mRNA and protein expression in the heart. BNP is produced in the left ventricle not only by cardiomyocytes but also by endothelial cells, T cells, and macrophages. Unloading of the left ventricle by a LVAD results in decreased BNP expression in the heart and plasma and may play an important role in the reverse remodeling process of the heart.

Is biopsy-proven cellular rejection an important clinical consideration in heart transplantation?

PURPOSE OF REVIEW

Immunosuppression strategies to prevent allograft rejection represent the cornerstone of long-term survival after heart transplantation. Endomyocardial biopsy has defined rejection in clinical cardiac transplantation and established a threshold for therapy. With the development of more effective immunosuppression modalities and the asymptomatic nature of most histologic rejection episodes, controversy exists regarding the need to augment immunosuppression based purely on histologic findings.

RECENT FINDINGS

The frequency of histologic rejection has declined with current immunosuppression. Resolution of lower grades of histologic rejection without treatment is the norm in both pediatric and adult heart transplant studies. Recurrent rejection episodes have been linked to the subsequent development of allograft coronary artery disease, and late rejection (even if asymptomatic) is associated with decreased survival in pediatric heart transplant recipients. Black race is a risk factor for recurrent rejection and reduced survival after late cellular rejection. Apoptosis of inflammatory cells is more evident during and after histologic rejection treated with corticosteroids. Despite numerous noninvasive modalities evaluated for the detection of rejection, to date noninvasive methods cannot reliably predict histologic rejection.

SUMMARY

Histologic rejection appears less common with current immunosuppressive strategies, and controversy exists about the need to treat asymptomatic rejection. It remains unproven whether non-treatment of moderate or greater rejection (>/=3A) increases the likelihood of recurrent rejection, which if present, may increase the risk of allograft coronary disease and/or reduced long-term survival.