Possibility of age regulation of the natriuretic peptide C-receptor in human platelets

The Use of Brain Natriuretic Peptide in the Evaluation of Heart Failure in Geriatric Patients

Heart failure is one of the main morbidity and mortality factors in the general population and especially in elderly patients. Thus, at the European level, the prevalence of heart failure is 1% in people under 55 years of age but increases to over 10% in people over 70 years of age. The particularities of the elderly patient, which make the management of heart failure difficult, are the presence of comorbidities, frailty, cognitive impairment and polypharmacy. However, elderly patients are under-represented in clinical trials on the diagnosis and treatment of heart failure. The need for complementary methods (biomarkers) for differential and early diagnosis of heart failure is becoming more and more evident, even in its subclinical stages. These methods need to have increased specificity and sensitivity and be widely available. Natriuretic peptides, in particular B-type natriuretic peptide (BNP) and its fraction NTproBNP, have gained an increasingly important role in the screening, diagnosis and treatment of heart failure in recent years.

Tayside Screening For Cardiac Events (TASCFORCE) study: a prospective cardiovascular risk screening study

PURPOSE

Risk factor-based models struggle to accurately predict the development of cardiovascular disease (CVD) at the level of the individual. Ways of identifying people with low predicted risk who will develop CVD would allow stratified advice and support informed treatment decisions about the initiation or adjustment of preventive medication, and this is the aim of this prospective cohort study.

PARTICIPANTS

The Tayside Screening for Cardiac Events (TASCFORCE) study recruited men and women aged≥40 years, free from known CVD, with a predicted 10-year risk of coronary heart disease<20%. If B-type natriuretic peptide (BNP) was greater than their gender median, participants were offered a whole-body contrast-enhanced MRI (WBCE-MRI) scan (cardiac imaging, whole-body angiography to determine left ventricular parameters, delayed gadolinium enhancement, atheroma burden). Blood, including DNA, was stored for future biomarker assays. Participants are being followed up using electronic record-linkage cardiovascular outcomes.

FINDINGS TO DATE

4423 (1740, 39.3% men) were recruited. Mean age was 52.3 years with a median BNP of 7.50 ng/L and 15.30 ng/L for men and women, respectively. 602 had a predicted 10-year risk of 10%-19.9%, with the remainder<10%. Age, female sex, ex-smoking status, lower heart rate, higher high-density lipoprotein and lower total cholesterol were independently associated with higher log10 BNP levels. Mean left ventricular mass was 129.2 g and 87.0 g in men and women, respectively.

FUTURE PLANS

The TASCFORCE study is investigating the ability of a screening programme, using BNP and WBCE-MRI, at the time of enrolment, to evaluate prediction of CVD in a population at low/intermediate risk. Blood stored for future biomarker analyses will allow testing/development of novel biomarkers. We believe this could be a new UK Framingham study allowing study for many years to come.

CLINICAL TRIAL REGISTRATION

ISRCTN38976321.

Potential and Limitations of Atrial Natriuretic Peptide as Biomarker in Pediatric Heart Failure-A Comparative Review

Although B-type Natriuretic Peptide (BNP), N-terminal-proBNP (NT-proBNP), and mid-regional-proANP (MR-proANP) are included in current guidelines on heart failure in adults, no guideline considering these biomarkers in pediatric heart failure is available. A new drug class of neprilysin inhibitors as fixed-dose combination (Sacubitril/valsartan) has been introduced and is currently being investigated in children suffering from heart failure. Atrial Natriuretic Peptide (ANP) is discussed as a more useful alternative to BNP because it may grants better insights into the effects of this treatment. Thus, this review aimed to provide an overview of the current knowledge concerning ANP in pediatric heart failure and compares its suitability regarding diagnosis and prognosis of heart failure. A literature search using PubMed resulted in 147 publications of which 22 studies were classified as relevant. The review presents available ANP, NT-proANP, and MR-proANP level data in children (0-18 years). Summarizing, ANP shows only minor differences as marker for diagnosing and monitoring pediatric heart failure if compared to BNP. Due to its fast release, ANP offers the advantage of displaying rapid changes during therapy or operation. ANP is -like the other natriuretic peptides- influenced by age, presenting with the highest levels in very young infants. ANP also correlates with atrial pressure and volume overload in children. In addition, ANP determination in saliva appears to be a promising alternative to blood sampling. Similarly to NT-proBNP, NT-proANP, and MR-proANP offer better stability but only few data has been published in children and thus their potential is only presumable so far.

Plasma levels of natriuretic peptides and development of chronic kidney disease

Background

Plasma levels of atrial and brain natriuretic peptides (ANP and BNP) are increased in patients with chronic kidney disease (CKD) complicated with deteriorated kidney function, but the relationship between the plasma level of ANP or BNP and the future development of CKD is unclear.

Methods

We measured the plasma ANP and BNP levels of 294 local residents without CKD in a Japanese community (56.5 ± 10.4 years, mean ± S.D.), who were followed up for the development of CKD over the next 7 years.

Results

Sixty-three residents developed CKD during the follow-up period, and the baseline level of plasma ANP of these residents was significantly higher than in those without CKD development. Kaplan-Meier analysis showed that the residents with higher ANP than the median value developed CKD more frequently than those with lower ANP. The association between plasma ANP level and CKD development was found to be independent of baseline estimated glomerular filtration rate by a Cox proportional hazards model, while this association became insignificant when adjusted by age; plasma ANP was significantly correlated with age. Compared with ANP, the relationship between plasma BNP and CKD development was unclear in these analyses.

Conclusions

Age-related elevation of plasma ANP levels preceded the development of CKD in the general population of Japan, raising a possibility for ANP being involved in the development of CKD.

State of the art of immunoassay methods for B-type natriuretic peptides: An update

The aim of this review article is to give an update on the state of the art of the immunoassay methods for the measurement of B-type natriuretic peptide (BNP) and its related peptides. Using chromatographic procedures, several studies reported an increasing number of circulating peptides related to BNP in human plasma of patients with heart failure. These peptides may have reduced or even no biological activity. Furthermore, other studies have suggested that, using immunoassays that are considered specific for BNP, the precursor of the peptide hormone, proBNP, constitutes a major portion of the peptide measured in plasma of patients with heart failure. Because BNP immunoassay methods show large (up to 50%) systematic differences in values, the use of identical decision values for all immunoassay methods, as suggested by the most recent international guidelines, seems unreasonable. Since proBNP significantly cross-reacts with all commercial immunoassay methods considered specific for BNP, manufacturers should test and clearly declare the degree of cross-reactivity of glycosylated and non-glycosylated proBNP in their BNP immunoassay methods. Clinicians should take into account that there are large systematic differences between methods when they compare results from different laboratories that use different BNP immunoassays. On the other hand, clinical laboratories should take part in external quality assessment (EQA) programs to evaluate the bias of their method in comparison to other BNP methods. Finally, the authors believe that the development of more specific methods for the active peptide, BNP1-32, should reduce the systematic differences between methods and result in better harmonization of results.

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.

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.

Reference limits for N-terminal-pro-B-type natriuretic peptide in healthy individuals (from the Framingham Heart Study)

N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) is a commonly measured cardiovascular biomarker in ambulatory and hospital settings. Nonetheless, there are limited data regarding "normal" ranges for NT-pro-BNP in healthy subjects, despite the importance of such information for interpreting natriuretic peptide measurements. In this study, a healthy reference sample free of cardiovascular disease from the Framingham Heart Study Generation 3 cohort was examined; there were 2,285 subjects (mean age 38 years, 56% women). Plasma NT-pro-BNP levels were measured using the Roche Diagnostics Elecsys 2010 assay, and reference values (2.5th, 50th, and 97.5th quantiles) were determined using empiric and quantile regression methods. Gender, age, blood pressure, and body mass index accounted for approximately 33% of the interindividual variability in NT-pro-BNP in the reference sample. NT-pro-BNP values were substantially higher in women compared to men at every age, and levels increased with increasing age for both genders. Using quantile regression, the upper reference values (97.5th quantile) for NT-pro-BNP were 42.5 to 106.4 pg/ml in men (depending on age) and 111.0 to 215.9 pg/ml in women. Intraindividual variability was assessed in an additional 12 healthy subjects, who had serial NT-pro-BNP measurements over 1 month. Intraclass correlation was 0.85, indicating that most of the variability in NT-pro-BNP concentrations was among rather than within subjects. However, the reference change value was 100%, suggesting that small proportional differences in NT-pro-BNP could be attributable to analytic variability. In conclusion, the reference limits obtained from this large, healthy, community-based sample may aid in the evaluation of NT-pro-BNP concentrations measured for clinical and research purposes.

Diagnostic and prognostic value of brain natriuretic peptide (BNP) concentrations in very elderly heart disease patients: specific geriatric cut-off and impacts of age, gender, renal dysfunction, and nutritional status

Confirming the presence of heart failure (HF) in geriatric patients is made difficult by the overlapping symptoms with other diseases and by limited access to investigative techniques such as echography, and the clinical signs are either non-constant or difficult to interpret. In this context, BNP measurement could prove highly useful. We determined a cut-off value of BNP for diagnosing HF in geriatric patients and gauged its predictive power in terms of cardiovascular events, dependence and death within a 6-month timeframe. This clinical and biological study was performed in patients, 44 women and 20 men, age>65 years with suspected HF hospitalized in the geriatric unit at Emile-Roux hospital. Echography was performed at baseline examination. BNP concentrations were determined at baseline examination and at 2 and 6 months later. Renal function was assessed via the Cockroft-Gault formula. Nutritional status was assessed using the geriatric nutritional risk index (GNRI). Final reference diagnosis was established by both cardiologist and geriatrician. The diagnostic value of BNP was assessed by area under the ROC curve. The average age of the 64 patients was 84.3±7.4 years. The final diagnosis was HF in 26 patients (41%). A BNP<129pg/ml had a negative predictive value of 90% (accuracy 80%) for excluding the diagnosis of HF. BNP values were predictive of cardiovascular events over a 2-month timeframe in patients with HF and over a 6-month timeframe in the global population. BNP values were not predictive of mortality in patients with or without HF. BNP testing should help to differentiate pulmonary from cardiac etiologies of dyspnea, but a specific cut-off point has to be used in geriatric settings, mainly for patients presenting nutritional and renal dysfunctions.

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.

Dysregulation of pulsatility in aging IV. Pulsatile signaling and cardiovascular aging: functions and regulation of natriuretic peptide signaling

Atrial and brain natriuretic peptides (ANP and BNP) are cardiac hormones connecting heart and kidney and playing a key role in hydromineral and hemodynamic homeostasis. In contrast with the renin-angiotensin-aldosterone system, circulating ANP and BNP are not temporally related with rapid eye movement (REM)-nonREM sleep cycles, autonomic activity, or blood pressure. Cardiac natriuretic peptides are secreted in a pulsatile manner, with short periods of 20-48min, in normal as well as in pathological conditions. The frequency of pulses seems to be unchanged with aging, whereas the absolute amplitude of the oscillations seems to increase, most likely as a result of an increase in the plasma hormone levels observed in elderly. Enhanced cardiac secretion and decreased degradation partly explain the higher ANP and BNP concentrations observed in elderly. Despite higher levels, the natriuretic system seems to loose efficiency at the renal site in elderly. This more probably relies on reduced target organ responsivity and not on deeply altered hormone secretion. Here we review the impact of aging on the renal effects of the natriuretic peptides, and point out the lack of knowledge on the precise interactions between the ultradian rhythms of the systems involved in salt and water balance in elderly. Additional studies focusing on potential age-induced alterations of the intracellular signaling pathway are now needed.

BNP or NTproBNP? A clinician's perspective

Existing literature on two natriuretic peptides--B-type natriuretic peptide (BNP) and amino terminal pro-brain natriuretic peptide (NTproBNP)--is overwhelming. Both peptides are acknowledged markers for cardiac dysfunction. Most of the sources present data on either BNP or NTproBNP making the comparison difficult. This paper focuses on reviewing studies directly comparing two peptides in the setting of chronic and acute heart failure (HF) and coronary artery disease. Many concomitant diseases influence these two peptides to varying extent. These characteristics should be taken into consideration when interpreting results. For most practical purposes, BNP and NTproBNP are interchangeable, and can be used based on local preferences and availability. NTproBNP seems to be more advantageous for diagnosing mild HF or asymptomatic left ventricular dysfunction.

Role of NT-proBNP and 6MWD in chronic thromboembolic pulmonary hypertension

BACKGROUND

This study aims to evaluate the role of NT-proBNP and six minute walking distance (6MWD) in the pre- and post-operative assessment of subjects undergoing pulmonary endarterectomy (PEA) for chronic thromboembolic pulmonary hypertension (CTEPH).

METHODS

Subjects undergoing PEA between August 2004 and July 2006 were assessed at baseline and 3 months post-operatively with resting haemodynamics, NT-proBNP and 6MWD.

RESULTS

A number of 111 subjects underwent surgery, of which 102 were included. 15 subjects died before their 3 month assessment. Non-survivors had significantly worse preoperative NT-proBNP and 6MWD (4728 pg/mL vs 1863 pg/mL, p=0.001, 182.4 m vs 263.5 m, p=0.001). Taking pre-operative cut-off values of 1200 pg/mL for NT-proBNP and 345 m for 6MWD, both tests had high negative predictive value for predicting mortality (97.3% and 100%, respectively). Amongst survivors, peri-operative changes in NT-proBNP and 6MWD correlated with changes in total pulmonary resistance (TPR) (r=0.49, p<0.001 and r=-0.46, p<0.001). Post-operatively, both NT-proBNP and 6MWD also correlated with mPAP (r=0.65, p<0.001 and r=-0.50, p<0.001) and PVR (r=0.63, p<0.001 and r=-0.47, p<0.001). The ability of NT-proBNP to predict persistent pulmonary hypertension was significantly confounded by age, but not gender, BMI or renal function.

CONCLUSIONS

Pre-operative evaluation with NT-proBNP and 6MWD helps risk-stratify patients prior to PEA. Post-operatively, both markers correlate with changes in disease burden and right ventricular function. These results suggest that both NT-proBNP and 6MWD offer effective 'bedside' tools for the long term follow up of patients with CTEPH.

Ageing, oestrogen, platelets and thrombotic risk

1. Adverse thrombotic cardiovascular events increase in women coincident with the onset of menopause. 2. Age past menopause may be an important variable in defining the benefit/risk of hormone treatments. 3. Few studies have examined hormonal status as a variable of ageing using a polygenomic approach of both humoral and cellular components of the coagulation system. 4. Longitudinal studies of a global set of platelet functions that define procoagulant activity (i.e. adhesion, aggregation, secretion and thrombin production) in individuals with documented hormonal status are needed to better understand how hormonal changes associated with ageing impact thrombotic risk.

Amino-terminal pro-B-type natriuretic peptide and B-type natriuretic peptide in the general community: determinants and detection of left ventricular dysfunction

OBJECTIVES

This study sought to characterize factors influencing amino-terminal pro-B-type natriuretic peptide (NT-proBNP) and to evaluate the ability of NT-proBNP to detect left ventricular (LV) dysfunction in a large community sample.

BACKGROUND

Secretion of BNP increases in cardiac disease, making BNP an attractive biomarker. Amino-terminal proBNP, a fragment of the BNP prohormone, is a new biomarker. We evaluated factors influencing NT-proBNP in normal patients and compared the ability of NT-proBNP and BNP to detect LV dysfunction in a large community sample.

METHODS

Amino-terminal pro-BNP was determined in plasma samples of a previously reported and clinically and echocardiographically characterized random sample (n = 1,869, age > or =45 years) of Olmsted County, Minnesota.

RESULTS

In normal patients (n = 746), female gender and older age were the strongest independent predictors of higher NT-proBNP. Test characteristics for detecting an LV ejection fraction < or =40% or < or =50% were determined in the total sample with receiver operating characteristic curves. Amino-terminal pro-BNP had significantly higher areas under the curve for detecting an LV ejection fraction < or =40% or < or =50% than BNP in the total population and in several male and age subgroups, whereas areas were equivalent in female subgroups. Age- and gender-adjusted cutpoints improved test characteristics of NT-proBNP. Both assays detected patients with systolic and/or moderate to severe diastolic dysfunction to a similar degree, which was less robust than the detection of LV systolic dysfunction alone.

CONCLUSIONS

Amino-terminal pro-BNP in normal patients is affected primarily by gender and age, which should be considered when interpreting values. Importantly, in the entire population sample NT-proBNP performed at least equivalently to BNP in detecting LV dysfunction and was superior in some subgroups in detecting LV systolic dysfunction.

Clinical relevance of biological variation: the lesson of brain natriuretic peptide (BNP) and NT-proBNP assay

The clinical relevance of brain natriuretic peptide (BNP) and N-terminal (NT)-proBNP assays as a diagnostic tool and prognostic marker in patients with cardiovascular diseases has recently been confirmed. However, several studies demonstrated variation of intra-individual BNP concentrations of >30% (ranging from 30% to 50%) with reference change values at the 95% confidence interval (i.e., the estimated critical difference) ranging from 99% to 130% in healthy subjects and heart failure patients. According to this estimated confidence interval, only a great variation in plasma BNP levels should be considered significant in an individual patient (for example, a decrease of >50% or an increase of more than two-fold). Many recent clinical studies have demonstrated that BNP variations below this estimated critical difference could also have clinical relevance. Like the concentration of other neuro-hormones, levels of plasma BNP fluctuate widely and rapidly along with heart rhythm and blood pressure variations in response to physiological stimuli. However, biological variation of BNP should not be interpreted strictly as random fluctuation around a homeostatic set point, as assumed by the common model used in all studies on biological variation of BNP reported in the literature. These results cannot be directly transferred to clinical practice. While awaiting more accurate studies, we suggest that variations of plasma BNP three-fold greater than the analytical imprecision should be considered as potentially relevant from a physiological and clinical point of view.

BNP--Considering a heartfelt message

The natriuretic hormones have been discovered as mediators of the cardiac response to volume overload and mechanical dysfunction. Although there are some physiological differences between atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), it is BNP that has been found to be most useful as a clinical test. BNP is secreted along with an N terminal proBNP cleavage product (NT-proBNP). The similarities between these two tests are far greater than the differences. They are both probably useful in the diagnosis of high-risk patients (e.g. dyspnoeic) and may be useful in monitoring cardiac failure treatment. Although BNP levels in the normal range predict the risk of cardiac events and mortality, there is little evidence to promote their use as a screening test. In such an important condition as cardiac failure we should consider any messages that are likely to be of value, particularly those that are heartfelt.

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.

C-type natriuretic peptide in vascular physiology and disease

Natriuretic peptides play a critical role in coordination of fluid/electrolyte balance and vascular tone. The renal effects of circulating atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are distinct from the paracrine effects of vascular C-type natriuretic peptide (CNP). CNP is widely expressed throughout the vasculature and is found in particularly high concentrations in the endothelium. Recent studies demonstrate that CNP is a novel endothelium-derived hyperpolarising factor (EDHF) that complements the actions of other endothelial vasorelaxant mediators such as nitric oxide (NO) and prostacyclin. Since several cardiovascular disorders are associated with dysfunction of natriuretic peptide activity, selective modulation of the natriuretic peptide pathways represents an important therapeutic target; whilst this has been exploited to some degree in terms of ANP/BNP, the therapeutic potential of CNP has yet to be tapped. This review focuses on recent findings on the actions and mechanism of locally produced endothelial-derived CNP in the cardiovascular system and highlights many potential avenues for therapeutic intervention, via modulation of CNP-signalling, in cardiovascular disease.

Prevalence of maternal dietary iodine insufficiency in the north east of England: implications for the fetus

BACKGROUND

Maternal subclinical hypothyroidism is a cause of poor neurodevelopment outcome in the offspring. Although iodine deficiency is the most common cause of hypothyroidism world wide, there are no screening programmes for it in the United Kingdom where the population is assumed to be iodine replete.

OBJECTIVE

To determine the prevalence of reduced iodine intake by measuring urinary iodide concentrations in pregnant and non-pregnant women from the north east of England.

METHODS

Urinary iodide excretion (UIE) rate was estimated using inductively coupled mass spectrometry in 227 women at 15 weeks gestation and in 227 non-pregnant age matched controls. A reduced intake of iodine is indicated by a concentration in urine of less than 50 microg/l or less than 0.05 microg iodine/mmol creatinine.

RESULTS

Eight (3.5%) pregnant women and 13 (5.7%) controls had a reduced iodine/creatinine ratio. These values were higher when UIE was expressed as iodine concentration: 16 (7%) and 20 (8.8%) respectively. Ninety (40%) of the pregnant women had a UIE of 0.05-0.10, which is consistent with borderline deficiency.

CONCLUSION

In this study, 3.5% of pregnant women had evidence of iodine deficiency, and 40% may be borderline deficient. Larger scale studies are required to estimate the true prevalence of iodine deficiency in the United Kingdom.

Attenuation of biologic compensatory action of cardiac natriuretic peptide system with aging

Although plasma B-type natriuretic peptide (BNP) levels increase with age, the mechanisms responsible for this increase are unknown. We investigated the predictors of elevated BNP in older subjects without cardiac systolic dysfunction and overt renal dysfunction. Furthermore, we analyzed the relations between BNP and its second messenger, cyclic guanosine monophosphate (cGMP), to aging. In 252 subjects (mean age 69 +/- 12 years) with left ventricular ejection fraction >/=50% and creatinine levels <==1.5 mg/dl, plasma levels of BNP, cGMP, blood urea nitrogen, creatinine, and beta2-microglobulin (an endogenous marker of renal function), estimated glomerular filtration rate, and echocardiographic data were prospectively evaluated. Plasma BNP levels increased with age (r = 0.4, p <0.0001). With use of multivariate analysis, predictors of elevated BNP levels were age, use of beta blockers, and serum beta2-microglobulin levels. The molar ratio of cGMP to BNP significantly decreased with aging (r = 0.55, p <0.0001). Elevated BNP in older subjects with normal cardiac systolic function may be due in part to renal impairment. With aging, biologic compensation of the cardiac natriuretic peptide system may be attenuated.

Diagnostic accuracy and prognostic relevance of the measurement of cardiac natriuretic peptides: a review

BACKGROUND

The pathophysiologic and clinical relevance of cardiac natriuretic hormone (CNH) assays has been investigated in numerous experimental and clinical studies. Authors have sought to evaluate the diagnostic accuracy and prognostic relevance of the measurement of CNHs according to evidence-based laboratory medicine principles.

METHODS

In June 2003, we ran a computerized literature search on National Library of Medicine using keywords "ANP" and "BNP" and found more than 12 300 and 1200 articles, respectively. A more refined search with keywords "ANP or BNP assay" extracted approximately 7000 and 800 articles, respectively. Only studies specifically designed to evaluate the diagnostic accuracy and prognostic relevance of CNH measurements were selected from this huge mass of articles to be discussed in this review.

CONTENT

Several studies suggested that CNH assays may be clinically useful for the screening and classification of patients with heart failure, as a prognostic marker in cardiovascular disease, in the follow-up of patients with heart failure, and because they may reduce the need for further cardiac investigation. However, it is difficult to compare even the best-designed studies because not only did the authors evaluate different populations, they also used different gold standards.

CONCLUSIONS

CNH assays and conventional diagnostic work-ups provide complementary information for evaluation of the presence and severity of cardiac dysfunction and clinical disease. Several aspects of CNH assays are still to be elucidated, and further work is needed to carefully assess their diagnostic accuracy and prognostic value in cardiac disease.

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.

Plasma levels of adrenomedullin and atrial and brain natriuretic peptides in the general population: their relations to age and pulse pressure

Adrenomedullin (AM) and atrial and brain natriuretic peptides (ANP and BNP) exert vasodilator and natriuretic actions and are thought to share roles in counteracting the progression of hypertension or heart failure as circulating or locally-acting hormones. However, little data is available with regard to their roles in subjects who have no apparent cardiovascular diseases. The present study was carried out to identify the factors that affect plasma levels of AM, ANP and BNP in the general population. We measured the plasma levels of AM, ANP and BNP in 184 local residents who had a scheduled regular health checkup, and compared the findings with those for other clinical parameters. Univariate analyses showed that the plasma levels of AM, ANP and BNP were significantly correlated with age. The plasma levels of ANP and BNP were also significantly correlated with systolic blood pressure (SBP) and with pulse pressure (PP), an indicator of the stiffness of the great vessels. Multivariate analyses conducted using a stepwise method revealed that age was a significant, independent variable for the plasma levels of AM, ANP and BNP. In addition, PP was a significant factor for the plasma levels of ANP and BNP, while the plasma AM was significantly associated with body mass index (BMI). Thus, the plasma levels of AM, ANP and BNP all increased in association with aging, and those of ANP and BNP increased in association with PP, suggesting possible relationships between the plasma levels and age-related changes in the cardiovascular system.

Pathophysiological and clinical relevance of circulating levels of cardiac natriuretic hormones: are they merely markers of cardiac disease?

Several specific and sensitive markers for myocardial injury as well as diagnostic tests for the assessment and stratification of cardiovascular risk have been recently introduced in clinical laboratories. However, until a few years ago, there were no laboratory tests for diagnosis, stratification and follow-up of patients with heart failure. The assay for cardiac natriuretic hormones (CNH) fills this gap. Heart failure is not only the most frequent "final common pathway" in cardiovascular disease, but is also the most common primary hospital discharge diagnosis, as well as the most common cause of death in patients over 50 years of age in Western countries; therefore, CNH assay may be destined to assume a growing relevance in clinical cardiology. However, to consider CNH assay only as a general and functional indicator of cardiac structural disease, without recalling that atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are powerful hormones, may lead to underestimation of the physiological role they play in healthy subjects as well as in patients with heart failure. Indeed, the circulating levels of CNH should be always interpreted taking into account not only hemodynamic factors and myocardial performance, but also their relationship with the counter-regulatory neuroendocrine system (including renin-angiotensin-aldosterone system, sympathetic system, endothelins, cytokines and vasopressin), as well as other hormones (such as sex steroid hormones, thyroid hormones and glucocorticoids).

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.