Brain Natriuretic Peptide Precursor Research Articles

Brain natriuretic peptide precursor (NT-pro-BNP) levels predict for clinical benefit to sunitinib treatment in patients with metastatic renal cell carcinoma

BackgroundSunitinib is an oral, multitargeted tyrosine kinase inhibitor that has been approved for the treatment of metastatic renal cell carcinoma. Although the majority of sunitinib-treated patients receive a clinical benefit, almost a third of the patients will not respond. Currently there is no available marker that can predict for response in these patients.MethodsWe estimated the plasma levels of NT-pro-BNP (the N-terminal precursor of brain natriuretic peptide) in 36 patients that were treated with sunitinib for metastatic clear-cell renal carcinoma.ResultsFrom the 36 patients, 9 had progressive disease and 27 obtained a clinical benefit (objective response or disease stabilization). Increases in plasma NT-pro-BNP were strongly correlated to clinical outcome. Patients with disease progression increased plasma BNP at statistically significant higher levels than patients that obtained a clinical benefit, and this was evident from the first 15 days of treatment (a three-fold increase in patients with progressive disease compared to stable NT-pro-BNP levels in patients with clinical benefit, p < 0.0001). Median progression-free survival was 12.0 months in patients with less than 1.5 fold increases (n = 22) and 3.9 months in patients with more than 1.5 fold increases in plasma NT-pro-BNP (n = 13) (log-rank test, p = 0.001).ConclusionsThis is the first time that a potential "surrogate marker" has been reported with such a clear correlation to clinical benefit at an early time of treatment. Due to the relative small number of accessed patients, this observation needs to be further addressed on larger cohorts. More analyses, including multivariate analyses are needed before such an observation can be used in clinical practice.

Biomarkers for the Prediction of Major Adverse Cardiovascular Events in Patients With Acute Coronary Syndrome

The aim of this study is to find novel biomarkers for prognosis in patients with acute coronary syndrome (ACS). We enrolled 245 eligible patients with ACS and compared the protein expression between the two groups, with or without major adverse cardiovascular events (MACE). To determine biomarkers for prognosis, we performed mass spectrometry analysis. We found 10 proteins in the serum that can be used to classify ACS with or without MACE and specific protein peaks at m/z 1921.0, 2124.2, and 20887.3 that were increased in patients with MACE. These peaks reliably predict MACE occurrence in patients with ACS, in addition to the widely accepted markers troponin and brain natriuretic peptide precursor. The characteristic changes in the peaks at m/z 1921.09, 2124.2, and 20887.3 correlate with poor prognosis in ACS patients. These proteins could potentially be used as predictive biomarkers to evaluate patient prognosis.

Factors associated with the development of atrial fibrillation in patients with rheumatic mitral stenosis

The aim of this study was to evaluate the factors associated with the development of atrial fibrillation (AF) in patients with rheumatic mitral stenosis (MS). A total of 146 consecutive patients with rheumatic MS were screened. They were accepted to be in AF group and sinus rhythm group according to their rhythm in the baseline ECG. After screening, 38 patients were excluded due to hyperthyroidism (n = 13), chronic obstructive pulmonary disease (n = 22), malignancy (n = 2) and rheumatoid arthritis (n = 1). Therefore, remaining 108 patients, 74 of whom in sinus rhythm (MS-SR) and 34 of whom in AF (MS-AF) constituted study population. Fourty age- and gender-matched patients constituted control group. Factors associated with development of AF in multivariable analysis included High sensitivity C reactive protein (P = 0.005; odds ratio, 3.44; 95% confidence interval, 1.44-8.22), N-terminal of brain natriuretic peptide precursor (P < 0.0001; odds ratio, 1.03; 95% confidence interval, 1.02-1.06) and left atrial diameter (P < 0.0001; odds ratio, 1.68; 95% confidence interval, 1.32-2.14). Present study suggests that High sensitivity C reactive protein, N-terminal of brain natriuretic peptide precursor and left atrial diameter are associated with development AF in patients with MS.

The response of circulating brain natriuretic peptide to academic stress in college students

Brain natriuretic peptide (BNP), a cardiac peptide, has been implicated in the regulation of hypothalamic-pituitary–adrenocortical (HPA) responses to psychological stressors. The influence of academic stress on circulating concentration of the N-terminal fragment of BNP precursor (NT-proBNP), and in relation to the stress hormone (cortisol) response was studied in 170 college students undergoing major examinations. Just prior to the examination, we measured self-estimated stress level, systolic, and diastolic blood pressure (SBP, DBP), heart rate (HR), plasma levels of cortisol, and NT-proBNP. These parameters were compared to the participants' baseline measurements, taken at the same hour of a different ‘control day’, without a major examination to induce stress. Hemodynamic variables (SBP, DBP, and HR) increased on the examination day compared with baseline values (p < 0.001). Circulating cortisol concentration increased before examinations (+42%, p < 0.001). The response to stress was marked by a significant decrease in plasma NT-proBNP concentration ( − 40%, p < 0.001). We found in males a significant interaction between the cortisol elevation with examination stress and the NT-proBNP reduction (p = 0.02). In response to academic stress, the plasma cortisol elevation was accompanied by a marked reduction in plasma NT-proBNP level. These data may indicate that mental stress entails an interface between the HPA axis and the peripheral natriuretic peptide system, leading to reciprocating changes in circulating levels of the corresponding hormones.

Detection of Left Ventricular Hypertrophy in Rats Administered a Peroxisome Proliferator–Activated Receptor α/γ Dual Agonist Using Natriuretic Peptides and Imaging

Chronic treatment with suprapharmacologic doses of peroxisome proliferator-activated receptor (PPAR) agonists has a known potential for causing left ventricular hypertrophy (LVH). The mechanism by which LVH develops is not well understood nor are biomarkers of it well characterized. Natriuretic peptides are important regulators of cardiac growth, blood volume, and arterial pressure and may be useful biomarkers of LVH and hemodynamic changes that precede it. We measured amino-terminal pro-atrial natriuretic peptide (NTproANP), amino-terminal pro-brain natriuretic peptide (NTproBNP), and cardiac troponin I (cTnI) concentrations in serum and plasma, as well as transcripts in left ventricular heart tissue for atrial natriuretic peptide precursor (Nppa), brain natriuretic peptide precursor (Nppb), and myosin heavy chain-beta (Myh7) as potential biomarkers of LVH induced by a PPARalpha/gamma dual agonist in Sprague-Dawley rats. We used magnetic resonance imaging, echocardiography, and hemodynamics to identify structural and functional cardiovascular changes related to the biomarkers. Heart-to-brain weight ratios (HW:BrW) were correlated with NTproANP, NTproBNP, and cTnI concentrations in serum as well as fold change in expression of Nppa and Nppb. LVH was characterized by increased left ventricular wall thickness and inner diameter, increased cardiac output, decreased arterial blood pressure, and increased heart rate. In these studies, each end point contributed to the early detection of LVH, the ability to monitor its progression, and demonstrated the ability of NTproANP concentration in serum to predict LVH and hemodynamic changes.

Processing of Pro–Brain Natriuretic Peptide Is Suppressed by O-Glycosylation in the Region Close to the Cleavage Site

Processing of the brain natriuretic peptide (BNP) precursor, proBNP, is a convertase-dependent reaction that produces 2 molecules--the active BNP hormone and the N-terminal part of proBNP (NT-proBNP). Although proBNP was first described more than 15 years ago, very little is known about the cellular mechanism of its processing. The study of proBNP processing mechanisms is important, because processing impairments could be associated with the development of heart failure (HF). The biochemical properties of recombinant proBNP and NT-proBNP and the same molecules derived from the blood of HF patients were analyzed by gel-filtration chromatography, site-directed mutagenesis, and different immunochemical methods with a panel of monoclonal antibodies (MAbs). Part of the proBNP molecule (amino acid residues 61-76) located near the cleavage site was inaccessible to specific MAbs because of the presence of O-glycans, whereas the same region in NT-proBNP was completely accessible. We demonstrated that a convertase (furin) could effectively cleave deglycosylated (but not intact) proBNP. Of several mutant proBNP forms produced in a HEK 293 cell line, only the T71A variant was effectively processed in the cell. Only proBNP that was not glycosylated in the region of the cleavage site could effectively be processed into BNP and NT-proBNP. Site-directed mutagenesis enabled us to ascertain the unique suppressing role of T71-bound O-glycan in proBNP processing.

Genomic selection of reference genes for real-time PCR in human myocardium

BackgroundReliability of real-time PCR (RT-qPCR) data is dependent on the use of appropriate reference gene(s) for normalization. To date, no validated reference genes have been reported for normalizing gene expression in human myocardium. This study aimed to identify validated reference genes for use in gene expression studies of failed and non-failed human myocardium.MethodsBioinformatic analysis of published human heart gene expression arrays (195 failed hearts, 16 donor hearts) was used to identify 10 stable and abundant genes for further testing. The expression stability of these genes was investigated in 28 failed and 28 non-failed human myocardium samples by RT-qPCR using geNorm software.ResultsSignal recognition particle 14 kDa (SRP14), tumor protein, translationally-controlled 1 (TPT1) and eukaryotic elongation factor 1A1 (EEF1A1) were ranked the most stable genes. The commonly used reference gene, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was ranked the least stable of the genes tested. The normalization strategy was tested by comparing RT-qPCR data of both normalized and raw expression levels of brain natriuretic peptide precursor (NPPB), a gene known to be up-regulated in heart failure. Non-normalized levels of NPPB exhibited a marginally significant difference between failed and non-failed samples (p = 0.058). In contrast, normalized NPPB expression levels were significantly higher in heart-failed patients compared with controls (p = 0.023).ConclusionThis study used publicly available gene array data to identify a strategy for normalization involving two reference genes in combination that may have broad application for accurate and reliable normalization of RT-qPCR data in failed and non-failed human myocardium.

NT-proBNP Does Not Rise on Acute Ascent to High Altitude

The response of brain natriuretic peptide (BNP) to acute ascent to altitude is of interest as a surrogate for ventricular function and because BNP is involved in the normal homeostasis of the pulmonary vasculature. The structurally related hormone atrial natriuretic pressure (ANP) has been demonstrated to be elevated at altitude and implicated in natriuresis. We measured plasma concentrations of ANP and NT-proBNP (a more stable BNP precursor) in 10 healthy non-HAPE-susceptible lowlanders during acute exposure to 5200 m on the Apex 2 expedition to Bolivia. Systolic pulmonary artery pressure (PASP) was measured using tricuspid regurgitant jet estimation by echocardiography. Despite a significant rise in the PASP, NT-proBNP did not rise. A small decrease in NT-pro BNP occurred after 7 days at high altitude. There was no significant change in ANP levels. The lack of any increase in NT-proBNP in healthy resting subjects supports the view that ventricular function is well preserved and suggests that BNP is not playing a significant role in altered pulmonary artery pressure.

Novel Immunoassay for Quantification of Brain Natriuretic Peptide and Its Precursor in Human Blood

Brain natriuretic peptide (BNP) is an unstable molecule that can rapidly lose immunologic activity in blood. Conventional sandwich BNP immunoassays use 2 antibodies specific to 2 different epitopes. Larger distances between epitopes are associated with a greater probability of proteolysis sites being located between the antibody-binding sites, and thus such assays have an increased susceptibility to underdetect BNP because of the increased likelihood of proteolytic degradation. The purpose of our study was to develop a sandwich immunoassay for the precise quantification of BNP and BNP precursor (proBNP) in human blood that is not susceptible to proteolysis. Mice were immunized with an immune complex consisting of monoclonal antibody (MAb) 24C5 (specific for BNP peptide 11-22) and the entire BNP molecule. The MAb used in our assay (Ab-BNP2) recognizes the immune complex but neither free BNP nor MAb 24C5. We used MAbs 24C5 and Ab-BNP2 to develop a new type of sandwich BNP assay (the "single-epitope sandwich assay"), which requires only a short BNP fragment (fragment 11-22) for immunodetection. This assay recognizes both BNP and proBNP with the same efficiency and sensitivity and demonstrates both considerably less susceptibility to antigen degradation and greater stability of the measured antigen than conventional sandwich BNP immunoassays. We have developed this sensitive single-epitope sandwich assay for detecting BNP, proBNP, and their fragments in human blood. This assay appears promising for use in clinical studies to assist in triage, management, and outcomes assessment in heart failure patients.

Immunodetection of Glycosylated NT-proBNP Circulating in Human Blood

Brain natriuretic peptide (BNP) or NT-proBNP (N-terminal fragment of BNP precursor) measurements are recommended as aids in diagnosis and prognosis of patients with heart failure. Recently it has been shown that proBNP is O-glycosylated in human blood. The goal of this study was to map sites on the NT-proBNP molecule that should be recognized by antibodies used in optimal NT-proBNP assays. We analyzed endogenous NT-proBNP by several immunochemical methods using a broad panel of monoclonal antibodies specific to different epitopes of the NT-proBNP molecule. Treatment of endogenous NT-proBNP by a mixture of glycosidases resulted in significant improvement of the interaction between deglycosylated NT-proBNP and monoclonal antibodies (MAbs) specific to the mid-fragment of the molecule. MAbs specific to the N- and C-terminal parts of NT-proBNP (epitopes 13-24 and 63-76) were able to recognize glycosylated and deglycosylated protein with similar efficiency. The central part of endogenous NT-proBNP is glycosylated, making it almost "invisible" for the antibodies specific to the mid-fragment of the molecule. Thus sandwich assays using even one antibody (poly- or monoclonal) specific to the central part of the molecule could underestimate the real concentration of endogenous NT-proBNP. MAbs specific to the N- and C-terminal parts of NT-proBNP (epitopes 13-24 and 63-76) are the best candidates to be used in an assay for optimal NT-proBNP immunodetection.

Atrial function after epicardial microwave ablation in patients with atrial fibrillation

Objectives. To study epicardial microwave ablation of concomitant atrial fibrillation and its effects on heart rhythm and atrial function during follow-up. Design. The study included 20 open-heart surgery patients with concomitant atrial fibrillation. Transthoracic echocardiography with flow and tissue Doppler recordings was performed preoperatively and at 6 months postoperatively. Blood samples were obtained preoperatively and postoperatively for analysis of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and amino terminal precursor of brain natriuretic peptide (NT-proBNP). Results. Fourteen of 19 patients (74%) were in sinus rhythm with no antiarrhythmic drugs at 12 months. All patients in sinus rhythm had preserved left and right atrial-filling waves through atrioventricular valves during atrial contraction. Tissue velocity echocardiography on patients in sinus rhythm showed preserved atrial wall velocities, atrial strain, and atrial strain rate. Levels of natriuretic peptides tended to decrease in patients with stable sinus rhythm at one year compared to patients in atrial fibrillation. Conclusions. Epicardial microwave ablation results in sinus rhythm in a majority of patients and seems to preserve atrial mechanical function.

N-Terminal proB-type natriuretic peptide (NT-proBNP) concentrations in elite rugby players at rest and after active and passive recovery following strenuous training sessions

The serum biomarker N-terminal proB-type natriuretic peptide (NT-proBNP), a cleaved fragment of the brain natriuretic peptide (BNP) precursor (amino acids 1-76), is accepted as a standard marker for evaluating and monitoring cardiac injury characterized by myocardial wall stress. Strenuous exercise may generate transitory ischemia, myocardial stress and diastolic left ventricular dysfunction, possibly inducing increased concentrations of NT-proBNP. A purported caveat to prolonged strenuous exercise is based on evidence for biochemical and structural signs of heart dysfunction in recreational athletes after continuous exertion. We compared NT-proBNP levels in three groups of physically fit subjects: top-level rugby players, professional soccer players and healthy controls. NT-proBNP concentrations were measured at rest and after an intensive training session followed by two different recovery strategies (passive or active). A comparison of the three samples showed that NT-proBNP concentrations in the rugby players were lower than those in controls at rest and were similar to those in professional soccer players. Elevated post-training NT-proBNP levels were unaffected by the type of recovery. The relatively high NT-proBNP levels after active recovery when psychophysical stress is higher, because of cycling and cold water immersion, suggest that not only endurance exercise, but also strenuous, stressful short exercise can induce an increase in NT-proBNP concentrations. In this sample of professional athletes, NT-proBNP was low at rest, and the increase after physical exercise was physiological.

The Brain Natriuretic Peptide (BNP) Precursor Is the Major Immunoreactive Form of BNP in Patients with Heart Failure

Peptides derived from brain natriuretic peptide (BNP) precursor (proBNP), BNP, and the N-terminal fragment of proBNP (NT-proBNP) are used as biomarkers of heart failure. It remains unclear which forms of these peptides circulate in blood and which forms are measured by assays for these natriuretic peptides. To design assays for immunodetection of proBNP, NT-proBNP, and BNP, we used a panel of BNP- and NT-proBNP-specific monoclonal antibodies (MAbs). All MAbs were tested in 2-site combinations in time-resolved fluoroimmunoassays with recombinant or synthetic antigens and plasma from heart failure (HF) patients. ProBNP and related molecules were assayed in HF plasma samples and plasma extracts by means of gel filtration fast protein liquid chromatography (FPLC) before and after protein fractionation on Sep-Pak C18 cartridges. The limits of detection for BNP, proBNP, and NT-proBNP assays were 0.4, 3, and 10 ng/L, respectively. Gel filtration-FPLC studies revealed 1 peak of NT-proBNP (approximately 25 kDa), 1 peak of proBNP (approximately 37 kDa), and 2 peaks of BNP immunoreactivity, a major peak (approximately 37 kDa) for proBNP, and a minor peak (approximately 4 kDa) for BNP. In patient plasma, the molar concentration of NT-proBNP was almost 10 times that of proBNP. The mean proBNP:BNP ratio in patient plasma was 6.3, ranging from 1.8 to 10.8. ProBNP is the major BNP-immunoreactive form in human blood. The proBNP:BNP ratio in plasma samples is dependent on the methods used for sample handling and for the measurement of the peptides.

Atrial Overdrive Pacing in Patients with Sleep Apnea with Implanted Pacemaker

Atrial overdrive pacing markedly improved sleep-disordered breathing in a recent study. Using a single-blind, randomized, crossover design, we aimed to reproduce these findings and investigate the possible underlying mechanisms. Twenty ambulatory patients with an implanted pacemaker or cardioverter defibrillator were studied by polysomnography on 3 consecutive nights in a randomized, single-blind, crossover study in which devices were programmed for nonpacing or for overdrive pacing at 7 or 15 beats/minute faster than the mean nocturnal heart rate. Ventilation and biomarkers (urinary norepinephrine excretion, amino-terminal portion of the precursor of brain natriuretic peptide, or NT-proBNP, were also evaluated. Neither the primary endpoint apnea-hypopnea index, nor the apnea index, oxygen desaturation, ventilation, or biomarkers were affected by the nocturnal atrial overdrive pacing. A small, clinically insignificant, rate-dependent reduction in the hypopnea index was evoked by pacing (nonpacing, 13.4 +/- 1.4; pacing 7, 12.9 +/- 1.4; pacing 15, 10.9 +/- 1.0; p < 0.01, analysis of variance). The lack of effect on the apnea-hypopnea index means that atrial overdrive pacing is inappropriate for treating sleep-disordered breathing.

The use of NT-proBNP in clinical practice

Early detection of heart failure and the accurate diagnosis of heart failure remains a huge clinical challenge to family practitioners. ECGs and chest x-rays merely serve as baseline investigations and the diagnosis is eventually only confirmed by a two-dimensional echocardiogram coupled with Doppler-flow studies. Another biomarker of left ventricular dysfunction that could be added to the armamentarium of the generalist is the blood test proBNP, the precursor of brain natriuretic peptide (BNP). Studies have shown that, already in early phases of left-ventricular systolic dysfunction (asymptomatic left ventricular systolic dysfunction and diastolic dysfunction), BNP proved to be a good marker of both development of heart failure and prognosis. This article gives the generalist an approach to using proBNP in general practice for early detection of left ventricular dysfunction, exclusion of heart failure and prudent referral to the cardiologist.

Elevated plasma levels of Nt-proBNP in patients with type 2 diabetes without overt cardiovascular disease.

The NH(2)-terminal portion of the precursor of brain natriuretic peptide (Nt-proBNP) has been reported to be elevated in left ventricular dysfunction. This peptide is a split product from the proBNP molecule, and its level in the circulation is not, as the mature BNP peptide, dependent on the peripheral number of BNP receptors. We aimed to test the hypothesis that asymptomatic left ventricular dysfunction (ALVD), as estimated by Nt-proBNP, would be more prevalent in patients with type 2 diabetes without overt cardiovascular disease in comparison with matched control subjects. The study population consisted of 253 patients with type 2 diabetes and 230 matched control subjects aged 40-70 years without any overt heart disease from primary care centers in Western Finland and Southern Sweden. Nt-proBNP was measured in plasma by competitive enzyme immunosorbent assay. Patients with type 2 diabetes were shown to have higher Nt-proBNP values (360.9 pmol/l [262.6-467.9]) than control subjects (302.7 pmol/l [215.4-419.2]) (P < 0.001). Nt-proBNP levels were independently related to diabetes after adjustment for age, sex, systolic and diastolic blood pressure, BMI, heart rate, drug treatment, serum creatinine, and cystatin C. Our data suggest that the secretion of Nt-proBNP is increased in type 2 diabetic patients with no overt heart disease, suggesting that type 2 diabetes is associated with a higher prevalence of ALVD than hitherto thought. Nt-proBNP may thus serve as a screening instrument to select patients with type 2 diabetes who could benefit from an echocardiographical examination.

Prediction of outcome by neurohumoral activation, the six-minute walk test and the Minnesota Living with Heart Failure Questionnaire in an outpatient cohort with congestive heart failure.

To compare the precursor of atrial and brain natriuretic peptide (N-ANP, N-BNP), brain natriuretic peptide (BNP), big endothelin-1, the 6-min walk test and the Minnesota Living with Heart Failure Questionnaire (LHFQ) with regard to short-term outcome in an ambulatory heart failure population. Ninety-six individuals (left ventricular ejection fraction of 26+/-10%) were included in the study. Within 1 day blood samples of N-ANP, N-BNP, BNP and big endothelin-1 were obtained, and the 6-min walk test and LHFQ were measured. The predictive power of these variables - including renin-angiotensin system antagonist therapy - in respect of 1-year event-free survival were calculated with a Cox regression analysis. All investigated variables had the power to predict outcome in a univariate analysis. Multivariate analysis revealed that N-ANP (chi-square=58 P<0.0001), BNP (chi-square=8 P<0.01), the LHFQ (chi-square=6 P<0.02) and the renin-angiotensin system antagonist (chi-square=4 P<0.05), are independent predictors. We conclude that, in an open clinical cohort of patients with large differences in the progression of the disease, N-ANP, BNP and LHFQ are the most reliable predictors of worsening heart failure in the short term. However, the dosage of the ACE inhibitor influenced short-term survival in this population.

Circulating N-terminal brain natriuretic peptide precursor and endothelin levels in patients with syndrome X and left bundle branch block with preserved systolic function

Background: Deterioration of left ventricular function during follow-up was reported in some patients with syndrome X and concomitant left bundle branch block. The patients with syndrome X and left bundle branch block has been frequently presented with elevated Endothelin-1 (ET-1) level while brain natriuretic peptide (BNP) (a sensitive marker of left ventricular dysfunction) has not been measured in patients with syndrome X. Methods: The purpose of the present study was to assess left ventricular diastolic function, levels of N-terminal Brain Natriuretic Peptide (NT-proBNP) precursor and biochemical parameters of endothelial function in patients with syndrome X complicated by left bundle branch block but preserved left ventricular systolic function (group A, n=8). The echocardiographic and neurohormonal measures in these patients were compared to those in patients with syndrome X without left bundle branch block (group B, n=13), and controls (group C, n=15). Results: At rest and after exercise the serum concentration of NT-proBNP was significantly higher in group A than in the controls (at rest: 232±96 vs. 133±23 fmol/ml, P=0.03; after exercise: 313±96 vs. 180±33 fmol/ml, P=0.02). The highest concentration of endothelin-1 was also found in group A, being significantly higher than in the controls (6.81 vs. 4.52 pg/ml, P<0.05). Mitral flow abnormalities were detected in left bundle branch block patients. Accordingly, the lowest E/A ratio was in group A and it differed significantly from that in group C (0.85 vs. 1.1, P<0.05). E/A ratio inversely correlated with plasma NT-proBNP concentration in patients with left bundle branch block ( r=−0.48, P=0.02). Conclusions: Elevated NT-proBNP and endothelin-1 plasma concentrations were demonstrated in patients with syndrome X complicated by left bundle branch block even when left ventricular systolic function was still preserved. In this subgroup the magnitude of left ventricular diastolic dysfunction correlated with the increase of BNP level which reflects neurohormonal activation.

Radioimmunoassay for N-terminal probrain natriuretic peptide in human plasma

Measurement of plasma levels of natriuretic peptides has been used to assess left ventricular dysfunction and prognosis. Recently levels of the N-terminal peptide fragment of the precursor of brain natriuretic peptide have been reported to be present in peripheral plasma and to be increased in chronic heart failure patients. Our aim in this study was to develop a radioimmunoassay for N-terminal proBNP, to compare its plasma concentrations in control subjects and in patients with end-stage heart failure and to define its relation to brain natriuretic peptide (BNP). A polyclonal antibody was raised in rabbits against human N-terminal proBNP fragment (amino acid 1-21). The plasma N-terminal proBNP concentrations were assayed directly without extraction. No detectable cross-reactivity existed with other natriuretic peptides: BNP, ANP or N-terminal proANP. The assay had a detection limit (2 SD from zero) of 9.7 pmol/L. Plasma N-terminal proBNP was 29 (13-75) (median (range)) pmol/L in the control group. There were no gender difference, male: 28 (13-61) vs. female 33 (13-75) pmol/L, p= NS, but there was a positive correlation to age (r=0.52, p<0.0001). In patients with end-stage heart failure the median N-terminal proBNP levels were increased significantly 616 (114-2781) pmol/L (p<0.001) and in pooled data N-terminal proBNP showed a close correlation to BNP (r=0.96, p<0.0001). Size exclusion of plasma extracts indicated that proBNP (1-108) may circulate both as intact prohormone and as split products, N-terminal proBNP (1-76) and BNP (77-108). Our results support the concept that N-terminal proBNP measurement could be a valuable tool in the biochemical indication of increased cardiac wall stress.

Plasma amino-terminal pro-brain natriuretic peptide: A novel approach to the diagnosis of cardiac dysfunction

Background: Heart failure is a common cause of hospitalization and death across the industrialized world. Improving the diagnosis and care of patients with heart failure is therefore likely to have a major impact on morbidity, mortality, and health care costs. Methods and Results: To determine the relation between cardiac function and plasma levels of amino-terminal brain natriuretic peptide precursor (NT-proBNP), plasma NT-proBNP levels and ventricular function (by radionucleotide ventriculography) were measured in healthy patients, patients with renal failure, patients with recent myocardial infarction, and patients investigated for cardiorespiratory symptoms. Plasma NT-proBNP levels were greater in healthy women (median, 1.5 fmol/mL; range, 1.0 to 13.8 fmol/mL; n = 34) than healthy men (median, 1.0 fmol/mL; range, 1.0 to 3.3 fmol/mL; n = 33; P =.012). NT-proBNP levels were elevated in subjects with renal failure (geometric mean, 314 fmol/mL; range, 18 to 5,800 fmol/mL) and were related to left ventricular ejection fraction (LVEF) ( r = −0.86; P < .0001; n = 19). NT-proBNP levels were also related to LVEF in patients with recent myocardial infarction ( r = −0.62; P = −.0003; n = 29) and those investigated for cardiorespiratory symptoms ( r = −0.56; P = < .0001; n = 129). Applying an upper limit of normal of 5 fmol/mL for men and 15 fmol/mL for women (specificity, 100%), elevated plasma NT-proBNP levels had 100% sensitivity for the detection of LVEF less than 45% after myocardial infarction and 97% sensitivity for the detection of LVEF less than 45% in patients investigated for cardiorespiratory symptoms. NT-proBNP levels were also elevated in 87% of the patients with normal systolic function (LVEF ≥ 45%) after myocardial infarction and in 87% of the patients investigated for cardiorespiratory symptoms with heart failure and normal systolic function (LVEF ≥ 45%). Conclusions: Plasma NT-proBNP level is a sensitive indicator of cardiac dysfunction, both in the presence and absence of systolic dysfunction, and may prove to be a useful tool for the identification and management of cardiac dysfunction in the general community.