The prognostic role of atrial natriuretic peptides in hemodialysis patients

BACKGROUND: It is well known that plasma atrial natriuretic peptide (ANP) is an indicator of extracellular fluid volume expansion and that plasma ANP is considered to be a marker for setting the proper dry weight of HD patients. Although the plasma ANP is a prognostic predictor of cardiac death, the prognostic role of ANP in HD patients has yet to be elucidated. In this study, we investigated the prognostic role of ANP in HD patients. METHODS: Plasma ANP concentrations were measured in 105 HD patients after HD. Multiple regression analysis was performed to determine the major factors causing increased plasma ANP concentrations. Cardiac mortality was monitored for 24 months after baseline analysis, and the prognostic role of ANP was examined by Cox proportional hazards regression analysis. RESULTS: Multiple regression analysis showed that cardiovascular disease (CD) and age were independent factors for elevated ANP (R2 = 0.298, p < 0.0001). During a 24-month follow-up period, cardiac death occurred in 11 patients. Kaplan- Meier survival estimates of patients from varying plasma ANP levels (<50 and >50 pg/ml) differed between the two groups (p < 0.0001). The group with the higher ANP level (>50 pg/ml) had the lower survival. When compared with patients with ANP <50, the hazard ratios for cardiac death of patients with ANP of >50 pg/ml were 32.0 (95% confidence interval (CI) 4.1 to 252.4). Univariate Cox proportional hazards model showed that ANP, left ventricular ejection fraction (LVEF), LVMI, age, serum albumin and C-reactive protein (CRP) were significantly associated with the risk of cardiac mortality. By stepwise multivariate Cox proportional hazards analysis, only ANP, LVMI and CRP remained powerful independent predictors of cardiac death. The relative risk ratios were 3.483 (95% CI 1.640-7.397) for ln ANP, 1.023 (1.008-1.038) for LVMI, and 1.379 (1.115-1.705) for CRP. CONCLUSION: High plasma ANP level of post-HD were strongly associated with CD and age. Post-HD ANP level may be a reliable parameter for assessing the risk for cardiac death in HD patients by providing prognostic information independent of other variables previously reported.     

The role of natriuretic peptides in cardioprotection

Atrial natriuretic peptide (ANP) and brain (B-type) natriuretic peptide (BNP) are circulating hormones of cardiac origin that play an important role in the regulation of intravascular blood volume and vascular tone. The plasma concentrations of ANP and BNP are elevated in heart failure, and they are considered to compensate for heart failure because of their diuretic, natriuretic, and vasodilating actions and inhibitory effects on renin and aldosterone secretion. Evidence is also accumulating from recent work that ANP and BNP exert their cardioprotective functions not only as circulating hormones but also as local autocrine and/or paracrine factors. In studies using cultured neonatal myocytes and fibroblasts, exogenous administration of both ANP and ANP antagonists demonstrated that ANP has antihypertrophic and antifibrotic functions. Corroborating these in vitro results, mice lacking natriuretic receptor-A (NPR-A), the receptor for ANP and BNP, develop cardiac hypertrophy and fibrosis independent of their blood pressure. Recent studies also suggest that the intracardiac natriuretic peptides/cGMP system plays a counter-regulatory role against the intracardiac renin-angiotensin-aldosterone system and TGF-beta mediated pathway. In a clinical setting, human recombinant ANP and BNP may be used for a therapy of heart failure; however, further evaluation is required in the future.     

The role of natriuretic peptides in heart failure

Heart failure is a clinical syndrome associated with progressive cardiac, vascular, and renal dysfunction. Regardless of the initial injury, investigations have demonstrated that neurohormones play an important role in the complex multiorgan and cellular adaptations. Natriuretic peptides play a key role in this process, antagonizing the actions of the renin-angiotensin-aldosterone system, thus promoting vasodilatation and natriuresis. Other important physiologic properties of the natriuretic peptides are prolusitropic, sympathoinhibitory, antiproliferative, anti-ischemic, anti-inflammatory, and antioxidative. Administering exogenous natriuretic peptide is a US Food and Drug Administration-approved therapy for patients with advanced decompensated congestive heart failure. Also, measuring natriuretic peptide levels has diagnostic and prognostic value. More studies are needed to define the full potential of this unique family of endogenous peptides.     

The role of natriuretic peptides in heart failure

Heart failure is a clinical syndrome associated with progressive cardiac, vascular, and renal dysfunction. Regardless of the initial injury, investigations have demonstrated that neurohormones play an important role in the complex multiorgan and cellular adaptations. Natriuretic peptides play a key role in this process, antagonizing the actions of the renin-angiotensin-aldosterone system, thus promoting vasodilatation and natriuresis. Other important physiologic properties of the natriuretic peptides are prolusitropic, sympathoinhibitory, antiproliferative, anti-ischemic, anti-inflammatory, and antioxidative. Administering exogenous natriuretic peptide is a US Food and Drug Administration-approved therapy for patients with advanced decompensated congestive heart failure. Also, measuring natriuretic peptide levels has diagnostic and prognostic value. More studies are needed to define the full potential of this unique family of endogenous peptides.     

The broad homeostatic role of natriuretic peptides

A brief non-inclusive review on natriuretic peptides (NP), their receptors, and their main functional properties is presented. The three main NP, atrial (ANP), brain (BNP) and C-type (CNP) are considered. Guanylyl cyclase receptors modulate all the known systemic effects of NP. Clearance receptors determine the metabolic disposal of NP and in this manner regulate their plasma levels and/or local tissue concentrations. Structure-function properties, and homeostatic properties of NP receptors are presented. ANP, which plays a major role in pressure-volume homeostasis, is discussed in relationship to its effects on renal hemodynamic and excretory functions, inhibition of the renin-angiotensin-aldosterone system, vasorelaxant, and third-spacing action. For BNP special attention is directed to its role as a negative modulator of ventricular remodeling, in view of its anti-hypertrophic, anti-fibrotic and anti-inflammatory effects in the heart. The major effect of CNP in promoting vertebral and longitudinal bone growth is briefly addressed. Finally, emphasis is placed on the recent discovery that ANP affects fat metabolism in humans due to its powerful lipolytic action.     

Atrial natriuretic peptides predict mortality in the elderly

Objectives. To ascertain whether atrial natriuretic peptides could be used as prospective and independent predictors of total mortality in an elderly population.
Design. Atrial natriuretic peptides, ANP(1–98) and ANP(99–126), were measured in 541 subjects from the 85-year-old population of Gothenburg, Sweden. Before the study cardiovascular disorders such as congestive heart failure, ischaemic heart disease, hypertension and atrial fibrillation were defined. Total mortality was recorded during the prospective 60-month follow-up period.
Setting. Individuals aged 85 years from the population of Gothenburg, Sweden, were visited once at home and made one visit to Vasa Hospital.
Main outcome measures. Sixty-month mortality in relation to circulating concentrations of atrial natriuretic peptides.
Results. Circulating concentrations of ANP(1–98) and ANP(99–126) were significantly correlated with 60-month mortality in the total study population (ANP(1–98), P <0.001; ANP(99–126), P <0.01). In subjects with cardiovascular disorders, 60-month mortality was significantly correlated with increased concentrations of ANP(1–98) ( P <0.01) and ANP(99–126) ( P <0.05). In subjects with no defined cardiovascular disorder, 60-month mortality was significantly correlated with increased ANP(1–98) concentrations ( P <0.01).
Conclusions. In the elderly population, atrial peptides predict mortality in subjects with defined cardiovascular disorders as well as in the total population and may predict future cardiovascular disorder.     

Physiology of natriuretic peptides: The volume overload hypothesis revisited

The discovery of the natriuretic peptide system in the early 1980s aroused great interest among clinical cardiologists. The heart was not a mechanical pump alone, but also an endocrine organ that had powerful effects on blood circulation. Natriuretic peptides caused both natriuresis and diuresis, and they responded to a volume overload which caused either stretch or pressure on the heart. As a result, the findings led to the conclusion that the human body had a hormone with effects similar to those of a drug which treats high blood pressure. Later, it became evident that the volume contraction was fortified by extrarenal plasma shift. Here, a hypothesis is presented in which the role of natriuretic peptides is to regulate oxygen transport as the volume contraction leads to hemoconcentration with an increased oxygen-carrying capacity. Wall stress, either chemical or mechanical, changes the oxygen gradient of the myocardium and affects the diffusion of oxygen within a myocyte. In support of this hypothesis, hypoxia-response elements have been found in both the atrial natriuretic peptide and the brain natriuretic peptide genes.     

Physiology of natriuretic peptides: The volume overload hypothesis revisited简

The discovery of the natriuretic peptide system in the early 1980s aroused great interest among clinical cardiologists. The heart was not a mechanical pump alone, but also an endocrine organ that had powerful effects on blood circulation. Natriuretic peptides caused both natriuresis and diuresis, and they responded to a volume overload which caused either stretch or pressure on the heart. As a result, the findings led to the conclusion that the human body had a hormone with effects similar to those of a drug which treats high blood pressure. Later, it became evident that the volume contraction was fortified by extrarenal plasma shift. Here, a hypothesis is presented in which the role of natriuretic peptides is to regulate oxygen transport as the volume contraction leads to hemoconcentration with an increased oxygen-carrying capacity. Wall stress, either chemical or mechanical, changes the oxygen gradient of the myocardium and affects the diffusion of oxygen within a myocyte. In support of this hypothesis, hypoxia-response elements have been found in both the atrial natriuretic peptide and the brain natriuretic peptide genes.     

The role of the natriuretic peptides in the cardiovascular system

The discovery of the natriuretic peptide family was a breakthrough in modern cardiovascular physiology as it provided a direct link between the heart and the kidneys in the regulation of natriuresis. Along with vasopressin and the renin-angiotensin-aldosterone system, the natriuretic peptides comprise the key peptides on which our present understanding of neuroendocrine regulation of the cardiovascular system is based. Three natriuretic peptides have been identified; the A-type, B-type and C-type natriuretic peptides. The former two, the A- and B-type natriuretic peptides, function mainly in the cardiovascular system and comprise the cardiac natriuretic peptides. Together with our increased understanding of the neurohormonal regulation of the cardiovascular system in recent years, the discovery of the natriuretic peptide family was important in the establishment of the new field of cardiovascular endocrinology.     

The natriuretic peptides

Abstract. The natriuretic peptides are a family of widely distributed, but evolutionarily conserved, polypeptide mediators that exert a range of actions throughout the body. In cardiovascular homeostasis, the endocrine roles of the cardiac-derived atrial and B-type natriuretic peptide (ANP and BNP) in regulating central uid volume and blood pressure have been recognised for two decades. However, there is a growing realisation that natriuretic peptide actions go far beyond their volumeregulating effects. These pleiotropic actions include local (autocrine/paracrine) regulatory actions of ANP and BNP within the heart, and of another natriuretic peptide, CNP, within the vessel wall. Effects on function and growth of the local tissue environment are likely to be of great importance, especially in disease states where tissue and circulating levels of ANP and BNP rise markedly. At present, the relevance of other natriuretic peptides (notably uroguanylin and DNP) to human physiology and pathology remain uncertain. Other articles in this issue of Basic Research in Cardiology review the molecular physiology of natriuretic peptide signalling, with a particular emphasis on the lessons from genetically targetted mice; the vascular activity of natriuretic peptides; the regulation and roles of natriuretic peptides in ischaemic myocardium; and the diagnostic, prognostic and therapeutic roles of natriuretic peptides in heart failure.     

Biological variation of the natriuretic peptides and their role in monitoring patients with heart failure

BACKGROUND: B-type natriuretic peptide (BNP) and the inactive metabolite NT-proBNP are proven tests for diagnosis and staging of severity for patients with heart failure. However, the utility of these biomarkers for monitoring the success of drug therapy remains to be determined. Results of longitudinal studies on serial blood testing must be linked to overall patient morbidity and mortality outcomes. We previously determined the 8-week biological variability (BV) of BNP and NT-proBNP assays in healthy subjects and the 1-day BV for BNP alone in patients with compensated and stable heart failure. From these studies, the percent statistical change in serial samples of approximately 100% difference was estimated (95% confidence). METHODS: We applied the biological variability concepts to the serial results of BNP and NT-proBNP collected from patients with heart failure and compared the performance of these two markers. RESULTS: While there are minor differences in the results between the assays from one time period to another, the overall interpretation of results are essentially identical. Moreover, the majority of individual serial time points are not significantly different from the previous value. CONCLUSION: Frequent testing (e.g. daily) for BNP and NT-proBNP to monitor therapy for patients with CHF is not indicated, as overall changes require several days to become evident.     

Post-acute care: the role of natriuretic peptides

Heart failure is a chronic disease marked by variable acute exacerbations. Once hospitalized the decompensated patient may have signs and symptoms only partially reversed, medical therapy only partially optimized and deranged physiology only partially restored. Therefore, the post-acute care period is one of unique vulnerability and merits efforts of careful and comprehensive assessment of patients at risk of recurrent decompensation and rehospitalization. Natriuretic peptide (NP) assessment which has the ability to monitor dynamic changes in a patient's physiology, may play an important role as part of a post-acute care algorithm focused on early detection and prevention of further decompensation and rehospitalization. ?2012 Wiley Periodicals, Inc.     

Deconvolution analysis of cardiac natriuretic peptides during acute volume overload

Cardiac natriuretic peptides, especially amino terminal pro-Brain Natriuretic Peptide (NT-proBNP), are emerging as powerful circulating markers of cardiac function. However, the in vivo secretion and elimination (t1/2) of these peptides during acute volume overload have not been studied. We present the first report of the secretion and elimination of cardiac natriuretic peptides, based on deconvolution analysis of endogenous ovine plasma levels measured by specific radioimmunoassay. Four normal, conscious sheep underwent rapid right ventricular pacing (225 bpm) for 1 hour to stimulate acute cardiac natriuretic peptide release. Plasma samples and right atrial pressure measurements were taken at regular intervals 30 minutes before, during, and 4 hours after pacing. Baseline right atrial pressure significantly increased (P:=0.02) during the 1 hour of pacing in association with a prompt increase in plasma BNP (P:=0.03), atrial natriuretic peptide (P:=0.01), and NT-proBNP (P:=0.02). Deconvolution analysis showed that the t1/2 of NT-proBNP (69.6+/-10.8 minutes) was 15-fold longer than BNP (4.8+/-1. 0 minutes). Despite sustained increases in atrial pressure, cardiac secretion of natriuretic peptides (particularly atrial natriuretic peptide) fell during the pacing period, suggesting a finite source of peptide for secretion. Size-exclusion high-performance liquid chromatography revealed NT-proBNP to be a single immunoreactive peak, whereas BNP comprised at least 2 immunoreactive forms. These findings, especially the prompt secretion of BNP and the prolonged t1/2 of NT-proBNP, clarify the metabolism of BNP forms and help to explain the diagnostic value of NT-proBNP measurement as a sensitive marker of ventricular function.     

The natriuretic peptides in cardiovascular medicine

Within the last five years, assay systems for measurement of plasma levels of brain natriuretic peptide (BNP) have been approved as a diagnostic aid for heart failure (HF). Similarly, nesiritide, a recombinant form of human BNP, has been approved for the treatment of acutely decompensated HF. Both BNP as a diagnostic test and a therapeutic modality are rapidly becoming integrated into clinical practice. The purpose of this review is to provide a brief overview of the physiology of the natriuretic peptides relevant to their informed clinical use. The current literature regarding the utility of measuring BNP for the diagnosis and management of HF is reviewed and practical recommendations regarding the interpretation of BNP levels are offered. The clinical literature regarding the use of recombinant BNP for the treatment of HF is reviewed, underscoring current gaps in our knowledge regarding the indications for and benefits of this novel agent.     

The natriuretic peptides in heart failure

Abstract. Synthesis and release of the natriuretic peptides rises incrementally with increasing degrees of cardiac dysfunction. The prime stimulus is intracardiac distending pressures with modulating inuences including age, gender, renal function and other aspects of neurohormonal status. Measurements of plasma natriuretic peptide concentrations and of B-type natriuretic peptide and amino-terminal pro-B-type natriuretic peptide, in particular, show promise in diagnosis of heart failure, risk stratication in those with known heart disease, and in adjustment of therapy. Recombinant B-type natriuretic peptide itself can be administered as a treatment. These diagnostic, prognostic and therapeutic applications of B-type natriuretic peptide require a considerable expansion beyond current evidence, but it appears likely that the true role of plasma peptide measurements and peptide administration will become rmly established within the coming 5 year period.