Cardiac chamber-specific alterations of ANP and BNP expression with advancing age and with systemic hypertension

Physiology of the Right Ventricle Across the Lifespan

The most common cause of heart failure in the United States is ischemic left heart disease; accordingly, a vast amount of work has been done to elucidate the molecular mechanisms underlying pathologies of the left ventricle (LV) as a general model of heart failure. Until recently, little attention has been paid to the right ventricle (RV) and it has commonly been thought that the mechanical and biochemical properties of the RV are similar to those of the LV. However, therapies used to treat LV failure often fail to improve ventricular function in RV failure underscoring, the need to better understand the unique physiologic and pathophysiologic properties of the RV. Importantly, hemodynamic stresses (such as pressure overload) often underlie right heart failure further differentiating RV failure as unique from LV failure. There are significant structural, mechanical, and biochemical properties distinctive to the RV that influences its function and it is likely that adaptations of the RV occur uniquely across the lifespan. We have previously reviewed the adult RV compared to the LV but there is little known about differences in the pediatric or aged RV. Accordingly, in this mini-review, we will examine the subtle distinctions between the RV and LV that are maintained physiologically across the lifespan and will highlight significant knowledge gaps in our understanding of pediatric and aging RV. Consideration of how RV function is altered in different disease states in an age-specific manner may enable us to define RV function in health and importantly, in response to pathology.

Cardiac Troponin T as Early Marker of Subclinical Cardiovascular Deterioration in Black Hypertensive Women

BACKGROUND

Hypertensive heart disease is a rising concern, especially among black South African women. As high sensitivity cardiac troponin T (cTnT) is a marker of cardiomyocyte damage, we determined the potential link of (i) systemic endothelial dysfunction (reflected by urinary albumin-to-creatinine ratio), (ii) large artery stiffness, (iii) cardiac volume load (estimated by the N-terminal prohormone B-type natriuretic peptide (Nt-proBNP)), and (iv) ECG left ventricular hypertrophy in post-menopausal black women.

METHODS

In 121 (50 normotensive and 71 hypertensive) black women (mean age: 60.6 years), basic cardiovascular assessments including blood pressure and ECG were performed, along with plasma and urinary biomarkers including cTnT.

RESULTS

The cTnT levels (p=0.049) along with Nt-proBNP (p=0.003), pulse pressure (p<0.0001) and the Cornell product (p=0.030) were higher in hypertensive than normotensive women. Only in hypertensive women, was cTnT independently associated with urinary albumin-to-creatinine ratio (β=0.25; p=0.019), pulse pressure (β=0.31; p=0.019), Nt-proBNP (β=0.47; p<0.0001) and Cornell product (β=0.31; p=0.018). An independent association between albumin-to-creatinine ratio and cTnT was also evident in normotensive women (β=0.34; p=0.037).

CONCLUSION

We found cTnT to be a useful marker in an elderly black population relating to several measures of cardiovascular deterioration - from subclinical endothelial dysfunction to left ventricular hypertrophy.

Association between resting heart rate and N-terminal pro-brain natriuretic peptide in a community-based population study in Beijing

BACKGROUND

N-terminal pro-brain natriuretic peptide (NT-proBNP) is associated with an increased risk of cardiac insufficiency, which possibly leads to heart failure. However, the relationship between resting heart rate and NT-proBNP is unclear.

OBJECTIVE

This study focuses on this relativity between resting heart rate and plasma NT-proBNP levels in a surveyed community-based population.

METHODS

We evaluated the relativity between resting heart rate and plasma levels of NT-proBNP in 1,567 participants (mean age 61.0 years, range 21-96 years) from a community-based population in Beijing, People's Republic of China.

RESULTS

In patients with high resting heart rate (≥75 beats/min), NT-proBNP was higher than in those having low resting heart rate (<75 beats/min). In multiple linear stepwise regression analysis, plasma NT-proBNP was associated with resting heart rate (partial correlation coefficient, 0.82; 95% confidence interval, 0.18-1.51; P=0.011). A subsequent subgroup analysis revealed that the association between resting heart rate and plasma NT-proBNP was strengthened in subjects over 60 years old (partial correlation coefficient 1.28; 95% confidence interval, 0.49-2.36; P=0.031); while the relativity between resting heart rate and plasma NT-proBNP was not emerged in the younger subgroup (<60 years old).

CONCLUSIONS

Resting heart rate was associated with plasma NT-proBNP in the elderly, which indicated a relationship between resting heart rate and cardiac function damage.

New insight into improvement of cardiovascular outcomes with intensive glycemic control in patients with metabolic syndrome and type 2 diabetes mellitus included

The epidemiology of metabolic syndrome (MetS) is very concerning since this is a widespread chronic disease in adult and elderly population. Different epidemiological studies confirmed strong relationship between type 2 diabetes mellitus (DM2) inclusive MetS and the occurrence of microvascular and macrovascular complications in these patients. Therefore, we are discussing molecular mechanisms and pathways recently introduced and intensively researched. These molecules have been held responsible for direct and indirect correlative trends important in the assessment of potential benefit of intensive glycemic control. Novel substances may improve patient's outcome in recent future regarding cardiovascular complications though their acting mechanisms have not been completely elucidated. We are reviewing whether it would intensive glycemic control be a reasonable approach in patients with MetS when DM2 is included and which recommendations are currently widely applied. The aim was therefore to emphasize current need for further investigations in the field since the utility of intensive glycemic control in all DM/MetS patients as mean for reduction of cardiovascular complications still remains controversial.

Right heart adaptation to pulmonary arterial hypertension: physiology and pathobiology

Survival in patients with pulmonary arterial hypertension (PAH) is closely related to right ventricular (RV) function. Although pulmonary load is an important determinant of RV systolic function in PAH, there remains a significant variability in RV adaptation to pulmonary hypertension. In this report, the authors discuss the emerging concepts of right heart pathobiology in PAH. More specifically, the discussion focuses on the following questions. 1) How is right heart failure syndrome best defined? 2) What are the underlying molecular mechanisms of the failing right ventricle in PAH? 3) How are RV contractility and function and their prognostic implications best assessed? 4) What is the role of targeted RV therapy? Throughout the report, the authors highlight differences between right and left heart failure and outline key areas of future investigation.

Inverse association of N-terminal pro-B-type natriuretic peptide with metabolic syndrome in patients with congestive heart failure

BACKGROUND

Metabolic syndrome has been shown to be associated with lower levels of plasma N-terminal pro-B-type natriuretic peptide (Nt-proBNP) in the general population. We sought to elucidate the relationship between Nt-proBNP and components of metabolic syndrome in patients with congestive heart failure (CHF).

METHODS

Fasting blood samples were obtained from 93 patients in our institution. Plasma levels of Nt-proBNP and other biochemical data were measured. The New York Heart Association (NYHA) classification system (I-IV) was used to define the functional capacity of CHF. Metabolic syndrome and its components were defined using diagnostic criteria from the International Diabetes Federation.

RESULTS

Forty-nine patients (52.7%) had CHF. There was a positive correlation between plasma Nt-proBNP levels and NYHA functional capacity in CHF patients. Plasma Nt-proBNP levels increased significantly with each increasing NYHA class of the disease. The prevalence of metabolic syndrome in CHF patients was higher than that in patients without CHF. Most importantly, we found that plasma Nt-proBNP levels were lower in CHF patients with metabolic syndrome attributable to inverse relationships between plasma Nt-proBNP and body mass index (β = -0.297), plasma triglyceride (β = -0.286) and homeostasis model assessment of insulin resistance (HOMA-IR; β = -0.346). Fasting glucose to insulin ratio (FGIR, an insulin sensitivity index) was positively associated with plasma Nt-proBNP levels (β = 0.491), and was the independent predictor of plasma Nt-proBNP levels in CHF patients.

CONCLUSIONS

Plasma Nt-proBNP levels are inversely associated with metabolic syndrome in CHF patients. Reduced plasma Nt-proBNP levels in CHF patients may lead to impaired lipolysis and metabolic function, and may contribute to the development of metabolic syndrome in CHF patients.

Relation of N-terminal pro-B-type natriuretic peptide with diastolic function in hypertensive heart disease

BACKGROUND

Elevated natriuretic peptide levels in asymptomatic individuals without heart failure are associated with increased risk of adverse cardiovascular outcomes and may reflect subclinical cardiac dysfunction.

METHODS

In a sample of 313 asymptomatic individuals (51% women, mean age 61 years) with hypertension and diastolic dysfunction, we examined the association of plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) with both conventional and advanced echocardiographic measures of systolic and diastolic function, including myocardial strain, using speckle-tracking-based analyses.

RESULTS

In univariate analyses, higher NT-proBNP was associated with greater left ventricular mass index (P = 0.003), left atrial volume index (P = 0.007), lateral E' velocity (P < 0.0001), E/E' ratio (P < 0.0001), peak global longitudinal systolic strain (P = 0.015), systolic strain rate (P = 0.021), and early diastolic strain rate (P < 0.0001). In multivariable analyses, NT-proBNP remained associated with measures of diastolic dysfunction, including lateral E' velocity (P = 0.013) and the E/E' ratio (P = 0.008). However, early diastolic strain rate was the echocardiographic parameter most strongly associated with NT-proBNP (P = 0.003).

CONCLUSIONS

In the setting of asymptomatic hypertensive heart disease and preserved ejection fraction, elevation in natriuretic peptide levels is predominantly associated with subclinical diastolic dysfunction.

NT-proBNP, C-reactive protein and soluble uPAR in a bi-ethnic male population: the SAfrEIC study

Objective and design

This cross-sectional study aimed to investigate associations between a marker of cardiac strain, the N-terminal prohormone B-type natriuretic peptide (NT-proBNP), and inflammation as reflected by either a conventional or novel inflammatory marker in a bi-ethnic South African cohort.

Methods and subjects

We measured NT-proBNP, C-reactive protein (CRP) and plasma-soluble urokinase plasminogen activator receptor (suPAR) levels along with conventional biomarkers in black (n = 117) and white (n = 116) men.

Results

NT-proBNP, CRP and suPAR levels were higher in black compared to white men. NT-proBNP was significantly associated with both CRP (r = 0.38; p = 0.001) and suPAR (r = 0.42; p<0.001) in black men only. After full adjustment in multiple regression analyses, the above associations of NT-proBNP with CRP (β = 0.199; p = 0.018) and suPAR (β = 0.257; p<0.01) were confirmed in black men.

Conclusion

These results suggest that a low-grade inflammatory state as reflected by both a conventional and novel marker of inflammation may contribute to higher cardiovascular risk as reflected by the associations obtained with a marker of cardiac strain in black South African men.

Sex-specific differences in natriuretic peptide and nitric oxide synthase expression in ANP gene-disrupted mice

Sex-specific differences in hormone-mediated gene regulation may influence susceptibility to cardiac hypertrophy, a primary risk factor for cardiovascular disease. Under hormonal influence, natriuretic peptide (NP) and nitric oxide synthase (NOS) systems modulate cardio-protective gene programs through common downstream production of cyclic guanosine 3'-5' monophosphate (cGMP). Ablation of either system can adversely affect cardiac adaptation to stresses and insults. This study elucidates sex-specific differences in cardiac NP and NOS system gene expression and assesses the impact of the estrous cycle on these systems using the atrial natriuretic peptide gene-disrupted (ANP(-/-)) mouse model. Left ventricular expression of the NP and NOS systems was analyzed using real-time quantitative polymerase chain reaction in 13- to 16-week-old male, proestrous and estrous female ANP(+/+) and ANP(-/-) mice. Left ventricular and plasma cGMP levels were measured to assess the convergent downstream effects of the NP and NOS systems. Regardless of genotype, males had higher expression of the NP system while females had higher expression of the NOS system. In females, transition from proestrus to estrus lowered NOS system expression in ANP(+/+) mice while the opposite was observed in ANP(-/-) mice. No significant changes in left ventricular cGMP levels across gender and genotype were observed. Significantly lower plasma cGMP levels were observed in ANP(-/-) mice compared to ANP(+/+) mice. Regardless of genotype, sex-specific differences in cardiac NP and NOS system expression exist, each sex enlisting a predominant system to conserve downstream cGMP. Estrous cycle-mediated alterations in NOS system expression suggests additional hormone-mediated gene regulation in females.

NT-proBNP is associated with fibulin-1 in Africans: the SAfrEIC study

OBJECTIVES

The N-terminal prohormone B-type natriuretic peptide (NT-proBNP) is involved in the regulation of volume load and secreted when systemic cardiac overload occurs. Fibulin-1 on the other hand is a component of many extracellular matrix proteins including those present in atherosclerotic lesions, expressed in elastin-containing fibres of blood vessels, and also in the heart. Due to an alarming prevalence of hypertensive heart disease in black South Africans, we investigated the associations of NT-proBNP with fibulin-1 and markers of arterial stiffness in Africans and Caucasians.

METHODS

We included 231 Africans and 238 Caucasians from South Africa aged 22-77 years. Serum NT-proBNP and fibulin-1 levels were determined, and arterial compliance and pulse wave velocity were measured.

RESULTS

Africans had significantly higher blood pressure and NT-proBNP levels than Caucasians and African men had higher fibulin-1 levels than Caucasian men. In single regression analysis, NT-proBNP was significantly associated with fibulin-1 in African men and Caucasian women. NT-proBNP correlated negatively with arterial compliance in all groups except Caucasian women. After partial adjustments, the association between NT-proBNP and fibulin-1 strengthened in African men only. After full adjustment in multiple regression analysis, the association of NT-proBNP with fibulin-1 was confirmed in African men (R(2)=0.41; β=0.26; p<0.01) and also in younger women (R(2)=0.34; β=0.251; p=0.012).

CONCLUSIONS

Only Africans indicated a significant independent association between NT-proBNP and fibulin-1, suggesting that cardiovascular alterations are already present in this relatively young African population as opposed to Caucasians.

Influence of age, race, sex, and body mass index on interpretation of midregional pro atrial natriuretic peptide for the diagnosis of acute heart failure: results from the BACH multinational study

AIMS

Midregional pro atrial natriuretic peptide (MR-proANP) is useful for diagnosing acute heart failure (HF) in patients presenting to the Emergency Department with dyspnoea. Optimal interpretation of MR-proANP requires understanding of how various demographic variables influence its levels and performance as a diagnostic marker. We sought to determine how age, race, sex, and body mass index (BMI) affect the levels and interpretation of MR-proANP for the diagnosis of acute HF.

METHODS AND RESULTS

The Biomarkers in Acute Heart Failure (BACH) study was an international 15-centre study of 1641 patients presenting to the Emergency Department with acute dyspnoea. Of these, 1352 had complete information on age, race, sex, and BMI. MR-proANP levels increased with age and were higher in men and in patients with lower BMI. MR-proANP performed better as a diagnostic marker in younger individuals and in blacks compared with whites. Despite this, MR-proANP at the recommended cut-off point of 120 pmol/L was >90 % sensitive in ruling out the diagnosis of acute HF in all subgroups of patients except white subjects <50 years old.

CONCLUSION

Age, race, sex, and BMI affect MR-proANP levels to various degrees. However, the diagnostic performance of the recommended cut-off point of 120 pmol/L to rule out acute HF was robust across most subgroups. Although both sex and BMI affected MR-proANP levels, they did not alter its overall diagnostic performance. Lower cut-off points for MR-proANP could be considered in younger patients and in patients with a higher BMI, to optimize diagnostic sensitivity.

Molecular signature of a right heart failure program in chronic severe pulmonary hypertension

Right heart failure is the cause of death of most patients with severe pulmonary arterial hypertensive (PAH) disorders, yet little is known about the cellular and molecular causes of right ventricular failure (RVF). We first showed a differential gene expression pattern between normal rat right and left ventricles, and postulated the existence of a molecular right heart failure program that distinguishes RVF from adaptive right ventricular hypertrophy (RVH), and that may differ in some respects from a left heart failure program. By means of microarrays and transcriptional sequencing strategies, we used two models of adaptive RVH to characterize a gene expression pattern reflective of growth and the maintenance of myocardial structure. Moreover, two models of RVF were associated with fibrosis, capillary rarefaction, the decreased expression of genes encoding the angiogenesis factors vascular endothelial growth factor, insulin-like growth factor 1, apelin, and angiopoeitin-1, and the increased expression of genes encoding a set of glycolytic enzymes. The treatment of established RVF with a β-adrenergic receptor blocker reversed RVF, and partly reversed the molecular RVF program. We conclude that normal right and left ventricles demonstrate clearly discernable differences in the expression of mRNA and microRNA, and that RVH and RVF are characterized by distinct patterns of gene expression that relate to cell growth, angiogenesis, and energy metabolism.

Pro-B-type natriuretic peptide(1-108) circulates in the general community: plasma determinants and detection of left ventricular dysfunction

OBJECTIVES

The purpose of this study was to investigate circulating pro-B-type natriuretic peptide (proBNP(1-108)) in the general community and evaluate its ability to detect left ventricular (LV) dysfunction.

BACKGROUND

The current concept for cardiac endocrine function is that, in response to cardiac stress, the heart secretes B-type natriuretic peptide (BNP(1-32)) and amino-terminal pro-B-type natriuretic peptide (NT-proBNP(1-76)) after intracardiac cleavage of their molecular precursor, proBNP(1-108). We hypothesized that proBNP(1-108) circulates in normal human subjects and that it is a useful biomarker for LV dysfunction.

METHODS

Our population-based study included a cohort of 1,939 adults (age ≥45 years) from Olmsted County, Minnesota, with 672 participants defined as healthy. Subjects underwent in-depth clinical characterization, detailed echocardiography, and measurement of proBNP(1-108). Independent factors associated with proBNP(1-108) and test characteristics for the detection of LV dysfunction were determined.

RESULTS

ProBNP(1-108) in normal humans was strongly influenced by sex, age, heart rate, and body mass index. The median concentration was 20 ng/l with a mean proBNP(1-108) to NT-proBNP(1-76) ratio of 0.366, which decreased with heart failure stage. ProBNP(1-108) was a sensitive (78.8%) and specific (86.1%) biomarker for detecting LV systolic dysfunction, which was comparable to BNP(1-32), but less than NT-proBNP(1-76), in several subsets of the population.

CONCLUSIONS

ProBNP(1-108) circulates in the majority of healthy humans in the general population and is a sensitive and specific biomarker for the detection of systolic dysfunction. The proBNP(1-108) to NT-proBNP(1-76) ratio may provide insights into altered proBNP(1-108) processing during heart failure progression. Thus, this highly specific assay for proBNP(1-108) provides important new insights into the biology of the BNP system.

The role of N-terminal pro-brain natriuretic peptide (NT-pro-BNP) as a prognostic marker in older people: the impact of reduced renal function

The N-terminal pro-brain natriuretic peptide (NT-pro-BNP) is released in response to volume expansion and/or increased tension on left ventricular myocytes. NT-pro-BNP is a useful diagnostic and prognostic biomarker both in patients with dyspnoea of unknown aetiology, and for risk assessment of patients with established heart failure. However, impaired kidney function – a common condition in older people as well as a strong risk factor for cardiovascular disease is associated with elevated circulating levels of NT-pro-BNP. Therefore, it is important to know the kidney function when interpreting an elevated NT-pro-BNP measurement obtained in older people in order to diagnose or stage congestive heart failure.

Prognostic value of N-terminal pro-brain natriuretic peptide in elderly people with acute myocardial infarction: prospective observational study

OBJECTIVE

To examine the influence of age on the predictive value of N-terminal pro-brain natriuretic (NT-proBNP) peptide assay in acute myocardial infarction.

DESIGN

Prospective observational study.

SETTING

All intensive care units in one French region.

PARTICIPANTS

3291 consecutive patients admitted for an acute myocardial infarction, from the RICO survey (a French regional survey for acute myocardial infarction).

MAIN OUTCOME MEASURE

Cardiovascular death at 1 year.

RESULTS

Among the 3291 participants, mean age was 68 (SD 14) years and 2356 (72%) were men. In the study population, the median NT-proBNP concentration was 1053 (interquartile range 300-3472) pg/ml. Median values for age quarters 1 to 4 were 367 (119-1050), 696 (201-1950), 1536 (534-4146), and 3774 (1168-9724) pg/ml (P<0.001). A multiple linear regression analysis was done to determine the factors associated with the pro-peptide concentrations in the overall population. NT-proBNP was mainly associated with age, left ventricular ejection fraction, creatinine clearance, female sex, hypertension, diabetes, and anterior wall infarction. At one year's follow-up, 384 (12%) patients had died from all causes and 372 (11%) from cardiovascular causes. In multivariate analysis, NT-proBNP remained strongly associated with the outcome, beyond traditional risk factors including creatinine clearance and left ventricular ejection fraction, in each age group except in the youngest one (<54 years) (P=0.29). The addition of NT-proBNP significantly improved the performance of the statistical model in the overall study population (-2log likelihood 3179.58 v 3099.74, P<0.001) and in each age quarter including the upper one (1523.52 v 1495.01, P<0.001).The independent discriminative value of NT-proBNP compared with the GRACE score was tested by a diagonal stratification using the median value of the GRACE score and NT-proBNP in older patients (upper quarter). Such stratification strikingly identified a high risk group-patients from the higher NT-proBNP group and with a high risk score-characterised by a risk of death of almost 50% at one year.

CONCLUSIONS

In this large contemporary non-selected cohort of patients with myocardial infarction, NT-proBNP concentration had incremental prognostic value even in the oldest patients, above and beyond the GRACE risk score and traditional biomarkers after acute myocardial infarction. These data further support the potential interest of clinical trials specifically assessing NT-proBNP measurement as a guide to current treatment strategies, as well as novel strategies, in older patients with acute myocardial infarction.

Gene expression and physiologic responses of the heart to the initiation and withdrawal of caloric restriction

Aging increases and caloric restriction (CR) decreases morbidity and mortality associated with the cardiovascular system. Using Affymetrix microarrays, we identified changes in heart gene expression induced by aging and CR in male mice. Eight weeks of CR (CR8) reproduced 19% of the long-term CR (LTCR)-related expression changes. Because CR8 begins to extend the life span of these mice, these genes may be keys to its cardioprotective effects. CR8 and LTCR changed gene expression in a manner consistent with reduced remodeling and fibrosis, and enhanced contractility and energy production via lipid beta-oxidation. Molecular and histochemical studies indicated that CR reduced natriuretic peptide precursor type B and collagen expression, and reduced perivascular collagen deposition. We found smaller cardiomyocytes in the left ventricle of old-LTCR mice, suggesting reduced age-related cell death. Eight weeks of control feeding returned 97% of the LTCR-responsive genes to control expression levels. Thus, key CR-induced effects are rapidly responsive to diet, suggesting reduced caloric intake has rapid, positive effects on the heart.

N-Terminal Pro Brain Natriuretic Peptide Is Inversely Related to Metabolic Cardiovascular Risk Factors and the Metabolic Syndrome

We wanted to investigate the relationship of N-terminal pro brain natriuretic peptide (Nt-proBNP) to metabolic and hemodynamic cardiovascular (CV) risk factors in the general population. From a population-based sample of 2656 people 41, 51, 61, or 71 years of age, we selected 2070 patients without previous stroke or myocardial infarction who did not receive any CV, antidiabetic, or lipid-lowering treatment in 1993 to 1994. Traditional CV risk factors, 24-hour blood pressures, left ventricular (LV) mass, and ejection fraction by echocardiography, pulse wave velocity, urine albumin/creatinine ratio (UACR), and serum Nt-proBNP were measured in 1993 to 1994. The metabolic syndrome was defined in accordance with the definition of the European Group for the Study of Insulin Resistance (EGIR). Higher log(Nt-proBNP) was in multiple regression analysis related to female gender (beta=-0.37), older age (beta=0.32), higher clinic pulse pressure (beta=0.20), lower serum total cholesterol (beta=-0.15), lower LVEF (beta=-0.08, all P<0.001), lower log(serum insulin) (beta=-0.07), lower log(plasma glucose) (beta=-0.06, both P<0.01, lower log(serum triglyceride) (beta=-0.06), lower body mass index (beta=-0.05); lower heart rate (beta=-0.05), higher logUACR (beta=0.04, all P<0.05) and higher log(LV mass index) (beta=0.04, P=0.07), adjusted R2=0.35, P<0.001). The metabolic syndrome was associated with lower Nt-proBNP (35 pg/mL versus 48 pg/mL; P<0.001) and shifted the positive relationship between pulse pressure and Nt-proBNP to the right (ie, higher blood pressure for a given level of Nt-proBNP). The metabolic syndrome was associated with lower Nt-proBNP levels and shifted the positive relationship between Nt-proBNP and pulse pressure to the right, creating a possible link between the metabolic syndrome and hypertension.

Reference interval determination for N-terminal-B-type natriuretic peptide (NT-proBNP): A study in blood donors

We assessed reference values in a group of apparently healthy blood donors. A total of 1980 blood donors was recruited and tested for the presence of NT-proBNP using a newly developed electrochemiluminescence immunoassay (ECLIA) method. NT-proBNP clustered in all blood donors below the age of 50 years and an upper limit of normal (ULN) was found to be 84 pg/ml for males and 146 pg/ml for females. Mean NT-proBNP values increased with increasing age which was due to an increasing number of individuals exceeding the ULN. Age- and gender-appropriate NT-proBNP levels decreased with increasing hemoglobin levels. Hemoglobin but not creatinine levels influenced the NT-proBNP concentration in this cohort. The upper limit of normal can be used in clinical studies to further assess groups of diseased individuals to define clinical cutoffs.

B-type natriuretic peptide: Issues for the intensivist and pulmonologist

OBJECTIVE

B-type natriuretic peptide (BNP) and N-terminal pro-BNP (NT-proBNP), although promising as biomarkers for heart failure, are affected by multiple confounders. The purpose of this article is to review the literature on the utility of BNP and NT-proBNP as biomarkers, with a focus on their role in critical illness and pulmonary diseases.

DATA SOURCE

Published articles on BNP and NT-proBNP.

DATA ANALYSIS

Multiple disorders in the intensive care unit cause elevated BNP and NT-proBNP levels, including cardiac diseases, shock, pulmonary hypertension, acute respiratory distress syndrome, acute pulmonary embolism, chronic obstructive pulmonary disease, renal failure, and other conditions.

CONCLUSIONS

Intensivists and pulmonologists should understand that BNP and NT-proBNP levels might be raised to different degrees not only in heart failure but also in critical illness and various pulmonary diseases; in these situations, BNP and NT-proBNP may also serve as markers of severity and prognosis.

B-type natriuretic peptide as a biomarker beyond heart failure: speculations and opportunities

Cardiac secretion of B-type natriuretic peptide (BNP) Increases with the progression of heart failure (HF), and plasma measurement of BNP has emerged recently as a useful, cost-effective biomarker for the diagnosis and prognosis of HF. The diagnostic utility of BNP is complemented by its therapeutic use in decompensated HF. Although clinical use of BNP as a biomarker in HF is Increasing, the specificity of BNP for HF is not robust, suggesting that other mechanisms beyond simple ventricular stretch stimulate BNP release. Several studies have shown that BNP levels Increase in other cardiovascular disease states including ischemia, arrhythmias, fibrosis, cardiac hypertrophy, and coronary endothelial dysfunction. Furthermore, 2 important studies revealed recently that moderate elevations In BNP level, well below the HF range, have prognostic value for future cardiovascular events. Specifically, BNP levels greater than 20 pg/mL were associated with significantly Increased risk of HF and atrial fibrillation. These observations increase speculation that elevated BNP levels represent a final common pathway for many cardiovascular pathologic states and that BNP can be used as a biomarker for non-HF mechanisms, preclinical disease, and other pathologic states of myocardial disease.

Opposite effects of losartan and atenolol on natriuretic peptides in patients with hypertension and left ventricular hypertrophy: a LIFE substudy

BACKGROUND

Secretion of natriuretic peptides is related to cardiac wall stress and influenced by the renin-angiotensin system. Therefore, we investigated the influence of blood pressure (BP) reduction with losartan versus atenolol on N-terminal pro-atrial natriuretic peptide (Nt-proANP) and N-terminal pro-brain natriuretic peptide (Nt-proBNP).

METHODS

In 183 patients with hypertension and electrocardiographic left ventricular (LV) hypertrophy, enrolled in the LIFE Study, we measured BP and serum Nt-proANP and Nt-proBNP by immunoassay after 2 weeks of placebo treatment and after 1, 2, 4, 6, 12, 24, 36 and 48 months of randomized treatment with losartan- or atenolol-based antihypertensive regimens.

RESULTS

There was no significant difference in BP at any time point between the two treatment groups. In patients treated with losartan, median Nt-proANP decreased gradually throughout the study, reaching significance after 6 months of treatment (1125-1060 pmol/l, P < 0.001), and Nt-proBNP decreased within the first month (24.7-18.7 pmol/l, P < 0.01) and stayed reduced throughout the study. During losartan-based antihypertensive treatment, Nt-proANP and Nt-proBNP as a percentage of baseline values were correlated to reductions in systolic BP (r = 0.11, P < 0.01 and r = 0.10, P = 0.01) and diastolic BP (r = 0.17, P < 0.001 and r = 0.07, P = 0.09). In atenolol-treated patients, Nt-proANP (1100-1640 pmol/l, P < 0.001) and Nt-proBNP (20.0-37.7 pmol/l, P < 0.001) increased during the first month, and remained elevated throughout the study. During atenolol-based antihypertensive treatment, changes in Nt-proANP (r = -0.16, P < 0.001) and Nt-proBNP (r = -0.07, P = 0.08) were negatively related to change in heart rate.

CONCLUSION

Nt-proANP and Nt-proBNP were reduced in parallel with BP in losartan-treated patients whereas they increased in parallel with decreased heart rate in atenolol-treated patients.

N-Terminal-proBNP (NT-proBNP) as an indicator of cardiac dysfunction

BACKGROUND

Natriuretic peptides represent a novel diagnostic tool in the assessment of cardiac dysfunction.

METHODS

A total of 473 consecutive referred patients presenting to 18 cardiologists for the assessment of their cardiac state were recruited for the study. Patients received a medical history, a physical examination an electrocardiogram and an echocardiogram where left ventricular ejection fraction was recorded.

RESULTS

NT-proBNP was found to correlate with left ventricular ejection fraction (LVEF), level of symptoms (NYHA classification), history of angina pectoris (AP) and myocardial infarction (AMI). Atrial fibrillation (AF) and thyroid dysfunction as well as renal impairment were shown to influence NT-proBNP levels.

CONCLUSION

The study supports the hypothesis that NT-proBNP determination contributes to the assessment of patients presenting to cardiologists.

N-terminal pro-brain natriuretic peptide predicts cardiovascular events in patients with hypertension and left ventricular hypertrophy

BACKGROUND

N-terminal pro-brain natriuretic peptide (Nt-proBNP) and N-terminal pro-atrial natriuretic peptide (Nt-proANP) are strong cardiovascular risk markers in patients with chronic heart failure, as well as in the general population. We investigated whether high Nt-proBNP or Nt-proANP could also predict the composite endpoint (CEP) of cardiovascular death, non-fatal stroke or non-fatal myocardial infarction in patients with hypertension and left ventricular (LV) hypertrophy.

METHODS

After 2 weeks of placebo treatment, clinical, laboratory and echocardiographic variables were assessed in 183 hypertensive participants in the LIFE echo substudy with electrocardiographic LV hypertrophy. Nt-proBNP and Nt-proANP were measured by immunoassay at baseline. The patients were followed for 60 +/- 5 months.

RESULTS

Using Cox regression analysis, the 25 CEP were predicted by ln(Nt-proBNP) (hazard ratio 1.61 per 2.73-fold increase, P < 0.01) as well as ln(Nt-proANP) (hazard ratio 2.93, P < 0.05). Nt-proBNP above the median value of 21.8 pmol/ml was associated with higher incidence of CEP (19.6 versus 7.7%, P < 0.05). Nt-proBNP above the median value was associated with higher incidence of CEP in the 123 patients without history of diabetes or cardiovascular disease (14.8 versus 4.3%, P < 0.05), but the association was insignificant in the 60 patients with a history of diabetes or cardiovascular disease (26.3 versus 18.2%, NS). Nt-proANP showed the same tendency.

CONCLUSION

Nt-proBNP, more than Nt-proANP, strongly predicts cardiovascular events in patients with hypertension and LV hypertrophy, especially in patients without diabetes or clinically overt cardiovascular disease.

Plasma B-Type Natriuretic Peptide Levels Predict Postoperative Atrial Fibrillation in Patients Undergoing Cardiac Surgery

BACKGROUND

Postoperative (postop) atrial fibrillation (AF) occurs in up to 60% of patients after cardiac surgery, leading to longer hospital stays and increased healthcare costs. Recently, B-type natriuretic peptide (BNP) has been reported to predict occurrence of nonpostoperative AF. This study evaluates whether elevated preoperative (preop) plasma BNP levels predict the occurrence of postop AF.

METHODS AND RESULTS

One hundred eighty-seven patients with no history of atrial arrhythmia who had a preoperative BNP level and had undergone cardiac surgery were identified. Their records were reviewed, and postoperative ECG and telemetry strips were analyzed for AF until the time of discharge. Postop AF was documented in 80 patients (42.8%). AF patients were older (68+/-11 versus 64+/-14 years, P=0.04), but there was no difference in sex distribution, hypertension, left ventricular (LV) function, LV hypertrophy (LVH), left atrial size, history of coronary artery disease (CAD), or beta-blocker use. Preop plasma BNP levels were higher in the postop AF patients (615 versus 444 pg/mL, P=0.005). After adjustment for age, sex, type of surgery, hypertension, LV function, LVH, left atrial size, CAD, and beta-blocker use, the odds ratios of postop AF according to increasing quartiles, compared with patients with lowest quartile, were 1.8, 2.5, and 3.7 (P(trend)=0.03).

CONCLUSIONS

An elevated preop plasma BNP level is a strong and independent predictor of postop AF. This finding has important implications for identifying patients at higher risk of postop AF who could be considered for prophylactic antiarrhythmic or beta-blocker therapy.

The confounding effects of age, gender, serum creatinine, and electrolyte concentrations on plasma B-type natriuretic peptide concentrations in critically ill patients

OBJECTIVE

To investigate the confounding effects of age, gender, serum creatinine, and electrolyte concentrations on plasma B-type natriuretic peptide (BNP) concentrations in critically ill patients.

DESIGN

A prospective cross-sectional study.

SETTING

A 20-bed general intensive care unit of a tertiary referral hospital.

PATIENTS

Patients were 121 patients admitted to the intensive care unit over a period of 9 wks.

INTERVENTIONS

Intravenous blood was collected for BNP measurements, and cardiac investigations including echocardiography were carried out for every patient on admission.

MEASUREMENTS AND MAIN RESULTS

The mean BNP concentration was 201 +/- 317 pg/mL (n = 121). Thirty-five patients (28.9%), identified to have cardiac abnormalities, exhibited higher BNP concentrations than those without cardiac abnormalities (518 +/- 394 vs. 60 +/- 98 pg/mL, p <.001). The females exhibited higher concentrations of BNP than males in the noncardiac abnormality group (96 +/- 132 pg/mL, n = 39 vs. 31 +/- 38 pg/mL, n = 47, p =.016). BNP correlated significantly with age (r2 =.19) and creatinine (r2 =.084). The latter correlation became insignificant when patients with cardiac abnormality were excluded. No correlation was found between serum Na+ and K+ concentrations with BNP. Multivariate analyses demonstrated that the presence of cardiac abnormalities accounted for nearly 50% of the BNP variation. Addition of age and gender improved R2 to 60%. The contribution of creatinine was found to be insignificant. There was no association between BNP concentrations and serum Na+ and K+ concentrations. Logistic analysis confirmed that BNP is the strongest predictor for cardiac abnormalities in the critically ill patients.

CONCLUSION

The current study demonstrated that plasma BNP concentrations increased with age and were higher in females than in males. Although the presence of cardiac disease was the most important determinant for BNP variations, age and gender also contributed significantly. The results suggest that age and gender need to be taken into account in the interpretation of BNP concentrations in critically ill patients.

Immunohistochemistry of atrial and brain natriuretic peptides in control cats and cats with hypertrophic cardiomyopathy

Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are cardiac hormones involved in electrolyte and fluid homeostasis. Our laboratory has investigated the use of ANP and BNP as diagnostic markers of cardiac disease in cats. We hypothesize that the cardiac distribution of ANP and BNP increases in cats with hypertrophic cardiomyopathy (HCM). Accordingly, we evaluated the immunohistochemical distribution of ANP and BNP in hearts of four cats with naturally occurring HCM relative to five healthy controls. Indirect immunoperoxidase was performed with polyclonal immunoglobulin G against feline ANP (1-28) and proBNP (43-56). In control cats, ANP and BNP immunoreactivity was restricted to the atria. Staining for both peptides was most intense adjacent to the endocardial surface. Auricles stained more diffusely than atria for both peptides. The interstitial capillaries and nerve fibers within the heart were positive only for BNP. Atrial immunoreactivity for ANP and BNP was more diffuse and had a less distinctly layered pattern in HCM than in control cats. Ventricular cardiomyocytes of HCM cats were negative for ANP but stained lightly and diffusely for BNP. The capillaries and nerve fibers remained positive for BNP. We conclude that in cats with HCM, the cardiac distribution of ANP and BNP is more diffuse in the atria and that novel expression of BNP in the ventricular cardiomyocytes occurs.

The influence of age, sex and other variables on the plasma level of N-terminal pro brain natriuretic peptide in a large sample of the general population

OBJECTIVE

To identify potentially confounding variables for the interpretation of plasma N-terminal pro brain natriuretic peptide (NT-proBNP).

DESIGN

Randomly selected subjects filled in a heart failure questionnaire and underwent pulse and blood pressure measurements, ECG, echocardiography, and blood sampling.

SETTING

Subjects were recruited from four Copenhagen general practices located in the same urban area and were examined in a Copenhagen University Hospital.

PATIENTS

382 women and 290 men in four age groups: 50-59 years (n = 174); 60-69 years (n = 204); 70-79 years (n = 174); and > 80 years (n = 120).

MAIN OUTCOME MEASURES

Associations between the plasma concentration of NT-proBNP and a range of clinical variables.

RESULTS

In the undivided study sample, female sex (p < 0.0001), greater age (p < 0.0001), increasing dyspnoea (p = 0.0001), diabetes mellitus (p = 0.01), valvar heart disease (p = 0.002), low heart rate (p < 0.0001), left ventricular ejection fraction < or = 45% (p < 0.0001), abnormal ECG (p < 0.0001), high log10[plasma creatinine] (p = 0.0009), low log10[plasma glycosylated haemoglobin A1c] (p = 0.0004), and high log10[urine albumin] (p < 0.0001) were independently associated with a high plasma log10[plasma NT-proBNP] by multiple linear regression analysis.

CONCLUSIONS

A single reference interval for the normal value of NT-proBNP is unlikely to suffice. There are several confounders for the interpretation of a given NT-proBNP concentration and at the very least adjustment should be made for the independent effects of age and sex.

Cardiac structure and function after short-term ethanol consumption in rats

Using an animal model of alcoholism, we investigated whether 4 months of ethanol consumption was associated with a preclinical stage of alcoholic cardiomyopathy (ACM), as well as activation of the renin-angiotensin system and natriuretic peptides (NPs). In other forms of cardiovascular disease, the latter peptide systems have been used as markers of left ventricular (LV) remodeling and dysfunction. Rats were fed either a liquid ethanol or control diet, and serial blood samples were collected at baseline, as well as at 2 and 4 months, for plasma renin activity (PRA), angiotensin II (ANG II), atrial natriuretic peptide (ANP), and brain natriuretic peptide (BNP) levels. Serial echocardiography (echo) was performed at the same time points, and isolated heart studies were performed to assess ex vivo contractility at 4 months. In both groups at 4 months, there were significant and similar increases in end-diastolic and end-systolic echo dimensions and LV mass. At 4 months, however, a significant decrease was found in the relative wall thickness in the ethanol-fed group compared with findings for the control group. In both groups at 4 months, significant and similar time-dependent decreases were shown in BNP and ANP levels compared with baseline values. No differences were found in NP gene expression or tissue levels. In both groups at 4 months, significant and similar increases were found in ANG II levels compared with baseline values. Over time, in both groups, PRA levels were unchanged. In this study, the only cardiac structural feature characteristic of a preclinical ACM was a decrease in relative wall thickness.

Impact of age and sex on plasma natriuretic peptide levels in healthy adults

Assays for natriuretic peptides have received considerable attention as potential screening tests for congestive heart failure and left ventricular dysfunction. However, information regarding the impact of age, sex, and other physiologic characteristics on natriuretic peptide levels is limited. We examined a healthy reference sample of 911 subjects (mean age 55 years, 62% women) from the Framingham Heart Study who were free of hypertension, valvular disease, diabetes, atrial fibrillation, obesity, coronary heart disease, congestive heart failure, and renal failure, and who had normal left ventricular systolic function. Plasma brain natriuretic peptide and N-terminal atrial natriuretic peptide levels were measured, and multivariable regression used to assess correlates of natriuretic peptide levels. The strongest predictors of higher natriuretic peptide levels were older age and female sex. Other multivariable predictors included lower diastolic blood pressure (higher pulse pressure), lower body mass index, and higher left atrial size. Reference limits were then formulated based on the empirical distribution of natriuretic peptide levels by gender both across all ages and partitioned by age. Age-pooled reference limits compared with age-specific limits classified a higher proportion of healthy elderly subjects (17% vs 2.5%), but a lower proportion of healthy young subjects (1% vs 2.5%) as "abnormal." We conclude that interpretation of natriuretic peptide levels should take into consideration gender and possibly age. The reference limits derived from this large, healthy community-based sample will aid in the identification of elevated natriuretic peptide levels in clinical practice.