Sympathoinhibitory effects of atrial natriuretic factor in normal humans

The longevity gene mIndy (I'm Not Dead, Yet) affects blood pressure through sympathoadrenal mechanisms

Reduced expression of the plasma membrane citrate transporter INDY (acronym I’m Not Dead, Yet) extends life span in lower organisms. Deletion of the mammalian Indy (mIndy) gene in rodents improves metabolism via mechanisms akin to caloric restriction, known to lower blood pressure (BP) by sympathoadrenal inhibition. We hypothesized that mIndy deletion attenuates sympathoadrenal support of BP. Continuous arterial BP and heart rate (HR) were reduced in mINDY-KO mice. Concomitantly, urinary catecholamine content was lower, and the decreases in BP and HR by mIndy deletion were attenuated after autonomic ganglionic blockade. Catecholamine biosynthesis pathways were reduced in mINDY-KO adrenals using unbiased microarray analysis. Citrate, the main mINDY substrate, increased catecholamine content in pheochromocytoma cells, while pharmacological inhibition of citrate uptake blunted the effect. Our data suggest that deletion of mIndy reduces sympathoadrenal support of BP and HR by attenuating catecholamine biosynthesis. Deletion of mIndy recapitulates beneficial cardiovascular and metabolic responses to caloric restriction, making it an attractive therapeutic target.

Deletion of mIndy reduces blood pressure and heart rate by attenuating catecholamine biosynthesis and recapitulates beneficial cardiovascular and metabolic responses to caloric restriction.

Can brain natriuretic peptide, S100b, and interleukin-6 prognosticate the neurological consequences in Egyptian patients presented with supratentorial intracerebral hemorrhage?

Background:

Biomarkers in supratentorial intracerebral hemorrhage (SICH) enhance the prognosis of the disease. This study aimed to assess the prognosticative grade of S100 calcium-binding protein B (S100B), interleukin-6 (IL-6), and the pro-brain natriuretic peptide (pro-BNP) in SICH outcome prediction.

Methods:

Blood samples of 50 SICH patients were analyzed for the biomarkers. The patients were classified into two groups with and without intraventricular hemorrhage (IVH). The following scales including Glasgow Coma Score (GCS), the Barthel index (BI), intracerebral hemorrhage (ICH) score, ICH volume, National Institutes of Health Stroke Scale (NIHSS), Modified Rankin Score (mRS), and length of stay were used to evaluate the severity.

Results:

The severity scores (NIHSS, GCS, BI, mRI) were significantly higher in SICH patients with IVH versus SICH patients without IVH (P = 0.002, 0.008, 0.001, and 0.03, respectively). Serum levels for a pro-BNP and S100b are significantly higher in SICH patients with IVH versus SICH patients without IVH (P = 0.02 and 0.027, respectively). Multivariate correlations between demographic (age), biomarkers panel (IL-6, S100b, and proBNP), and clinical and severity scores (ICH score, ICH volume, length of hospital stay [LOS], BI, mRS, GCS, and NIHSSS) in all studied patients showed a highly significant correlation between ICH score and pro-BNP (P = 0.04). There was a highly significant correlation between LOS and IL-6 (P = 0.003).

Conclusion:

Pro-BNP, IL-6, and S100b are greatly associated with the presence of IVH that, in turn, correlated well with poor clinical outcome measures.

Natriuretic peptides and neprilysin inhibition in hypertension and hypertensive organ damage

The family of natriuretic peptides (NPs) discovered in mammalian tissues including cardiac atrium and brain consists of three members, namely, atrial, B- and C-type natriuretic peptides (ANP, BNP, CNP). Since the discovery, basic and clinical studies have been vigorously performed to explore the biological functions and pathophysiological roles of NPs in a wide range of diseases including hypertension and heart failure. These studies revealed that ANP and BNP are hormones secreted from the heart into the blood stream in response to pre- or after-load, counteracting blood pressure (BP) elevation and fluid retention through specific receptors. Meanwhile, CNP was found to be produced by the vascular endothelium, acting as a local mediator potentially serving protective functions for the blood vessels. Because NPs not only exert blood pressure lowering actions but also alleviate hypertensive organ damage, attempts have been made to develop therapeutic agents for hypertension by utilizing this family of NPs. One strategy is to inhibit neprilysin, an enzyme degrading NPs, thereby enhancing the actions of endogenous peptides. Recently, a dual inhibitor of angiotensin receptor-neprilysin was approved for heart failure, and neprilysin inhibition has also been shown to be beneficial in treating patients with hypertension. This review summarizes the roles of NPs in regulating BP, with special references to hypertension and hypertensive organ damage, and discusses the therapeutic implications of neprilysin inhibition.

Neural control of blood pressure during pregnancy in humans

PURPOSE

Previous microneurographic studies found that muscle sympathetic nerve activity (MSNA) increased in normotensive pregnant women and was even greater in women with gestational hypertension and preeclampsia during the third trimester. It is possible that sympathetic activation during the latter months of normal pregnancy helps return arterial pressure to non-pregnant levels. However, when the increase in sympathetic activity is excessive, hypertension ensues. The key question that must be addressed is whether sympathetic activation develops early during pregnancy and remains high throughout gestation, or whether this sympathetic overactivity only occurs at term, providing the substrate for preeclampsia and other pregnancy-associated cardiovascular complications.

METHODS

This was a literature review of autonomic neural control during pregnancy.

RESULTS

Recent work from our laboratory and other laboratories showed that in healthy women resting MSNA increased in early pregnancy, increased further in late pregnancy, and returned to the pre-pregnancy levels shortly after delivery. We found that women who exhibited excessive sympathetic activation during the first trimester, before any clinical signs and symptoms appeared, developed gestational hypertension at term. We also found that the level of corin, an atrial natriuretic peptide-converting enzyme, was increased in the maternal circulation, especially during late pregnancy, as a homeostatic response to elevated sympathetic activity.

CONCLUSION

These findings provide important insight into the neural mechanisms underlying hypertensive disorders during pregnancy. With this knowledge, early prevention or treatment targeted to the appropriate pathophysiology may be initiated, which may reduce maternal and fetal death or morbidity, as well as cardiovascular risks in women later in life.

Adaptations in autonomic nervous system regulation in normal and hypertensive pregnancy

There is an increase in basal sympathetic nerve activity (SNA) during normal pregnancy; this counteracts profound primary vasodilation. However, pregnancy also impairs baroreflex control of heart rate and SNA, contributing to increased mortality secondary to peripartum hemorrhage. Pregnancy-induced hypertensive disorders evoke even greater elevations in SNA, which likely contribute to the hypertension. Information concerning mechanisms is limited. In normal pregnancy, increased angiotensin II acts centrally to support elevated SNA. Hypothalamic sites, including the subfornical organ, paraventricular nucleus, and arcuate nucleus, are likely (but unproven) targets. Moreover, no definitive mechanisms for exaggerated sympathoexcitation in hypertensive pregnancy have been identified. In addition, normal pregnancy increases gamma aminobutyric acid inhibition of the rostral ventrolateral medulla (RVLM), a key brainstem site that transmits excitatory inputs to spinal sympathetic preganglionic neurons. Accumulated evidence supports a major role for locally increased production and actions of the neurosteroid allopregnanolone as one mechanism. A consequence is suppression of baroreflex function, but increased basal SNA indicates that excitatory influences predominate in the RVLM. However, many questions remain regarding other sites and factors that support increased SNA during normal pregnancy and, more importantly, the mechanisms underlying excessive sympathoexcitation in life-threatening hypertensive pregnancy disorders such as preeclampsia.

Role of Corin in Blood Pressure Regulation in Normotensive and Hypertensive Pregnancy

Corin (an atrial natriuretic peptide-converting enzyme) represents a potential biomarker for gestational hypertensive disorders; yet, its role in blood pressure (BP) regulation throughout pregnancy remains unclear. We investigated the time course of change in blood corin content in relation to BP and sympathetic nerve activity throughout pregnancy. Forty-four women (29±0.9 years) participated. Following-term, 23 had low-risk (no personal history of gestational hypertensive disorders) normal pregnancies, 13 had high-risk (personal history of gestational hypertensive disorders) normal pregnancies, and 8 developed gestational hypertension. BP, heart rate, muscle sympathetic nerve activity, and serum corin were measured before pregnancy, during early (4-8 weeks) and late pregnancy (32-36 weeks), and postpartum (6-10 weeks). Overall, compared with prepregnancy, corin remained unchanged during early pregnancy, increased markedly during late pregnancy ( P<0.001), and returned to prepregnancy levels postpartum. In women who developed gestational hypertension, the change in corin from early to late pregnancy was greater than those with low-risk normal pregnancies (Δ971±134 versus Δ486±79 pg/mL; P<0.05). Throughout pregnancy, BP and muscle sympathetic nerve activity were augmented in women with gestational hypertension (all P<0.05). Finally, changes in corin from early to late pregnancy were related to all indices of BP ( R=0.454-0.551; all P<0.01) in late pregnancy, whereas burst frequency, burst incidence, and total muscle sympathetic nerve activity ( R=0.576-0.614; all P<0.001) in early pregnancy were related to changes in corin from early to late pregnancy. Corin plays a unique role in BP regulation throughout normotensive and, especially, hypertensive pregnancy and may represent a promising biomarker for determining women at high risk of adverse pregnancy outcome.

Natriuretic Peptides and Normal Body Fluid Regulation

Natriuretic peptides are structurally related, functionally diverse hormones. Circulating atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are delivered predominantly by the heart. Two C-type natriuretic peptides (CNPs) are paracrine messengers, notably in bone, brain, and vessels. Natriuretic peptides act by binding to the extracellular domains of three receptors, NPR-A, NPR-B, and NPR-C of which the first two are guanylate cyclases. NPR-C is coupled to inhibitory proteins. Atrial wall stress is the major regulator of ANP secretion; however, atrial pressure changes plasma ANP only modestly and transiently, and the relation between plasma ANP and atrial wall tension (or extracellular volume or sodium intake) is weak. Absence and overexpression of ANP-related genes are associated with modest blood pressure changes. ANP augments vascular permeability and reduces vascular contractility, renin and aldosterone secretion, sympathetic nerve activity, and renal tubular sodium transport. Within the physiological range of plasma ANP, the responses to step-up changes are unimpressive; in man, the systemic physiological effects include diminution of renin secretion, aldosterone secretion, and cardiac preload. For BNP, the available evidence does not show that cardiac release to the blood is related to sodium homeostasis or body fluid control. CNPs are not circulating hormones, but primarily paracrine messengers important to ossification, nervous system development, and endothelial function. Normally, natriuretic peptides are not powerful natriuretic/diuretic hormones; common conclusions are not consistently supported by hard data. ANP may provide fine-tuning of reno-cardiovascular relationships, but seems, together with BNP, primarily involved in the regulation of cardiac performance and remodeling. © 2017 American Physiological Society. Compr Physiol 8:1211-1249, 2018.

Are endogenous cardenolides controlled by atrial natriuretic peptide

Endogenous cardenolides are digoxin-like substances and ouabain-like substances that have been implicated in the pathogenesis of hypertension and mood disorders in clinical and pre-clinical studies. Regulatory signals for endogenous cardenolides are still unknown. These endogenous compounds are believed to be produced by the adrenal gland in the periphery and the hypothalamus in the central nervous system, and constitute part of an hormonal axis that may regulate the catalytic activity of the α subunit of Na(+)/K(+)-ATPase. A review of literature suggests that there is great overlap in physiological environments that are associated with either elevations or reductions in the levels of atrial natriuretic peptide (ANP) and endogenous cardenolides. This suggests that these two factors may share a common regulatory signal or perhaps that ANP may be involved in the regulation of endogenous cardenolides.

Cardiometabolic crosstalk in obesity-associated arterial hypertension

Abdominal obesity and elevated blood pressure commonly occur in the same patient and are key components of the metabolic syndrome. However, the association between obesity and increased blood pressure is variable. We review mechanisms linking cardiovascular and metabolic disease in such patients including altered systemic and regional hemodynamic control, neurohumoral activation, and relative natriuretic peptide deficiency. Moreover, we discuss recent results using omics techniques providing insight in molecular pathways linking adiposity, metabolic disease, and arterial hypertension. Recognition of the mechanisms orchestrating the crosstalk between cardiovascular and metabolic regulation in individual patients may lead to better and more precise treatments. It is reassuring that recently developed cardiovascular and metabolic medications may in fact ameliorate, both, cardiovascular and metabolic risks.

Efficacy and safety of nesiritide in patients with decompensated heart failure: a meta-analysis of randomised trials

OBJECTIVES

Current evidence suggests that nesiritide may have effects on renal function and decrease the incidence of mortality. However, a clear superiority using nesiritide in terms of renal toxicity and mortality in patients with heart failure was not consistently proven by previous studies. We performed a meta-analysis of all randomised trials to obtain the best estimates of efficacy and safety of nesiritide for the initial treatment of decompensated heart failure.

METHOD

We performed a meta-analysis of randomised trials of nesiritide in patients with decompensated heart failure (n=38,064 patients, in 22 trials). Two reviewers independently extracted data. Data on efficacy and safety outcomes were collected. We calculated pooled relatives risk (RRs), weighted mean difference and associated 95% CIs.

RESULTS

Compared with placebo, dobutamine and nitroglycerin, nesiritide indicated no increasing risk of total mortality. Compared with the combined control therapy, nesiritide was associated with non-significant differences in short-term mortality (RR 1.24; 95% CI 0.85 to 1.80; p=0.27), mid-term mortality (RR 0.86; 95% CI 0.60 to 1.24; p=0.42) and long-term mortality (RR 0.94; 95% CI 0.75 to 1.18; p=0.61). Nesiritide therapy increased the risk of hypotension (p<0.00 001) and bradycardia (p=0.02) when compared with control therapy. Compared with dobutamine or placebo therapy, no differences in serum creatinine, blood urea nitrogen and creatinine clearance, and no risk of the need for dialysis was observed in nesiritide therapy.

CONCLUSIONS

Our findings indicated that, in patients with heart failure, nesiritide was not associated with the risk of mortality. However, it increased the risk of cardiovascular adverse events. The change of serum creatinine and creatinine clearance had no significant difference, and no risk of the need for dialysis was observed after low-dose nesiritide treatment.

Evaluation of cardiac sympathetic nerve activity and aldosterone suppression in patients with acute decompensated heart failure on treatment containing intravenous atrial natriuretic peptide

PURPOSE

Aldosterone prevents the uptake of norepinephrine in the myocardium. Atrial natriuretic peptide (ANP), a circulating hormone of cardiac origin, inhibits aldosterone synthase gene expression in cultured cardiocytes. We evaluated the effects of intravenous ANP on cardiac sympathetic nerve activity (CSNA) and aldosterone suppression in patients with acute decompensated heart failure (ADHF).

METHODS

We studied 182 patients with moderate nonischemic ADHF requiring hospitalization and treated with standard therapy containing intravenous ANP and 10 age-matched normal control subjects. ANP was continuously infused for >96 h. In all subjects, delayed total defect score (TDS), heart to mediastinum ratio, and washout rate were determined by 123I-metaiodobenzylguanidine (MIBG) scintigraphy. Left ventricular (LV) end-diastolic volume, end-systolic volume, and ejection fraction were determined by echocardiography. All patients with acute heart failure (AHF) were examined once within 3 days and then 4 weeks after admission, while the control subjects were examined only once (when their hemodynamics were normal). Moreover, for 62 AHF patients, plasma aldosterone concentrations were measured at admission and 1 h before stopping ANP infusion.

RESULTS

123I-MIBG scintigraphic and echocardiographic parameters in normal subjects were more favorable than those in patients with AHF (all p < 0.001). After treatment, all these parameters improved significantly in AHF patients (all p < 0.001). We also found significant correlation between percent changes of TDS and aldosterone concentrations (r = 0.539, p < 0.001) in 62 AHF patients.

CONCLUSION

The CSNA and LV performance were all improved in AHF patients. Furthermore, norepinephrine uptake of myocardium may be ameliorated by suppressing aldosterone production after standard treatment containing intravenous ANP.

Natriuretic peptide receptor 3 (NPR3) is regulated by microRNA-100

Natriuretic peptide receptor 3 (NPR3) is the clearance receptor for the cardiac natriuretic peptides (NPs). By modulating the level of NPs, NPR3 plays an important role in cardiovascular homeostasis. Although the physiological functions of NPR3 have been explored, little is known about its regulation in health or disease. MicroRNAs play an essential role in the post-transcriptional expression of many genes. Our aim was to investigate potential microRNA-based regulation of NPR3 in multiple models. Hypoxic challenge elevated levels of NPPB and ADM mRNA, as well as NT-proBNP and MR-proADM in human left ventricle derived cardiac cells (HCMa), and in the corresponding conditioned medium, as revealed by qRT-PCR and ELISA. NPR3 was decreased while NPR1 was increased by hypoxia at mRNA and protein levels in HCMa. Down-regulation of NPR3 mRNA was also observed in infarct and peri-infarct cardiac tissue from rats undergoing myocardial infarction. From microRNA microarray analyses and microRNA target predictive databases, miR-100 was selected as a candidate regulator of NPR3 expression. Further analyses confirmed up-regulation of miR-100 in hypoxic cells and associated conditioned media. Antagomir-based silencing of miR-100 enhanced NPR3 expression in HCMa. Furthermore, miR-100 levels were markedly up-regulated in rat hearts and in peripheral blood after myocardial infarction and in the blood from heart failure patients. Results from this study point to a role for miR-100 in the regulation of NPR3 expression, and suggest a possible therapeutic target for modulation of NP bioactivity in heart disease.

The sympathetic nervous system as a target for the treatment of hypertension and cardiometabolic diseases

The regulation of blood pressure by the sympathetic nervous system is reviewed with an emphasis on the role of the sympathetic nervous system in the development and maintenance of hypertension. Evidence from patients and animal models is summarized. Because it is clear that there is a neural contribution to many types of human hypertension and other cardiometabolic diseases, the case is presented for a renewed emphasis on the development of sympatholytic approaches for the treatment of hypertension and other conditions associated with hyperactivity of the sympathetic nervous system.

Thermal vasodilation using a portable infrared thermal blanket in decompensated heart failure

Adjunctive and non-pharmacological therapies, such as heat, for the treatment of heart failure patients have been proposed. Positive results have been obtained in clinically stable patients, but no studies of the use of thermal therapy in patients with decompensated heart failure (DHF) have been reported. An open randomized clinical trial was designed in patients with DHF and controls. We studied 38 patients with a mean age of 56.9 years. A total of 86.8% were men, and 71% had nonischemic myocardiopathy. All participants were using dobutamine, and the median brain natriuretic peptide (BNP) level was 1396 pg/mL. An infrared thermal blanket heated the patients, who were divided into 2 groups: group T (thermal therapy) and group C (control). Group T underwent vasodilation using the thermal blanket at 50°C for 40 minutes in addition to drug treatment. The cardiac index increased by 24.1% (P = 0.009), and systemic vascular resistance decreased by 16.0% in group T (P < 0.024) after thermal therapy. Heat as a vasodilator increased the cardiac index and lowered systemic vascular resistance in DHF patients. These data suggest thermal therapy as a therapeutic approach for the adjuvant treatment of DHF patients.

Low-dose B-type natriuretic peptide raises cardiac sympathetic nerve activity in sheep

The reported effects of atrial natriuretic peptide (ANP) on sympathetic nerve activity (SNA) are variable, dependent on concomitant hemodynamic actions, and likely to be regionally differentiated. There are few reports of the effect of B-type natriuretic peptide (BNP) on SNA and none have measured cardiac SNA (CSNA) by direct microneurography. We measured the effects of low-dose ANP and BNP (2.4 pmol·kg−1·min−1 infused for 120 min) on CSNA and hemodynamics in conscious sheep ( n = 8). While there was a trend for mean arterial pressure and cardiac output to fall with both ANP and BNP, changes were not significant compared with vehicle control. However, BNP did significantly reduce systolic arterial (97 ± 4.2 vs. 107 ± 6.8 mmHg during control; P = 0.043) and pulse pressures (0.047) and increase heart rate (110 ± 6.7 vs. 96 ± 7.3 beats/min; P = 0.044). Trends for these hemodynamic parameters to change with ANP did not achieve statistical significance. ANP also had no significant effect on any CSNA parameters measured. In contrast, BNP induced a rise in both CSNA burst frequency (∼20 bursts/min higher than control, P = 0.011) and burst area (∼40% higher than control, P = 0.013). BNP-induced rises in burst incidence (bursts/100 beats), and burst area per 100 beats, however, were not significant. In conclusion, BNP infused at low doses that only had subtle effects on hemodynamics increased CSNA burst frequency and burst are per minute. This increase in CSNA may in large part be secondary to an increase in heart rate as CSNA burst incidence and burst area per 100 beats were not significantly increased. This study provides no evidence for inhibition of CSNA by natriuretic peptides.

Metabolic actions of natriuretic peptides and therapeutic potential in the metabolic syndrome

Natriuretic peptides (NPs) are a group of peptide-hormones mainly secreted from the heart, signaling via c-GMP coupled receptors. NP are well known for their renal and cardiovascular actions, reducing arterial blood pressure as well as sodium reabsorption. Novel physiological functions have been discovered in recent years, including activation of lipolysis, lipid oxidation, and mitochondrial respiration. Together, these responses promote white adipose tissue browning, increase muscular oxidative capacity, particularly during physical exercise, and protect against diet-induced obesity and insulin resistance. Exaggerated NP release is a common finding in congestive heart failure. In contrast, NP deficiency is observed in obesity and in type-2 diabetes, pointing to an involvement of NP in the pathophysiology of metabolic disease. Based upon these findings, the NP system holds the potential to be amenable to therapeutical intervention against pandemic diseases such as obesity, insulin resistance, and arterial hypertension. Various therapeutic approaches are currently under development. This paper reviews the current knowledge on the metabolic effects of the NP system and discusses potential therapeutic applications.

Microneurographic evidence in healthy middle-aged humans for a sympathoexcitatory reflex activated by atrial pressure

Atrial mechanoreceptors, stimulated by increased pressure or volume, elicit in healthy humans a net sympathoinhibitory response. The co-existence of an atrial reflex eliciting muscle sympathoexcitation has been postulated but undetected by conventional multi-unit muscle sympathetic nerve activity (MSNA). We hypothesized that in response to a selective increase in atrial pressure, single-unit MSNA would reveal a subpopulation of efferent sympathetic neurons with firing patterns opposite to the integrated multi-unit MSNA envelope. Multi- and single-unit MSNA recordings were acquired in eight healthy middle-aged subjects (age, 57 ± 8 years; body mass index, 25 ± 2 kg/m2) submitted to selective decreases or increases in atrial pressure by nonhypotensive lower body negative pressure (LBNP; −10 mmHg) or nonhypertensive lower body positive pressure (LBPP; +10 mmHg), respectively. Single-unit MSNA firing responses were classified as anticipated if spike frequency and incidence increased with LBNP or decreased with LBPP and paradoxical if they decreased with LBNP or increased with LBPP. LBNP decreased (3.2 ± 2.8 to 1.4 ± 3.1 mmHg, P < 0.01) and LBPP increased (3.3 ± 2.7 to 4.9 ± 2.8 mmHg, P < 0.01) estimated central venous pressure without affecting stroke volume, systemic pressure, or resistance. Multi-unit MSNA increased with LBNP (31 ± 17 to 38 ± 19 bursts/min, P < 0.01) and diminished with LBPP (33 ± 15 to 28 ± 15 bursts/min, P < 0.01). Of 21 single-units identified, 76% exhibited firing responses to both LBNP and LBPP concordant with multi-unit MSNA, whereas 24% demonstrated discordant or paradoxical responses. The detection of two subpopulations of single-units within the multi-unit MSNA recording, exhibiting opposite firing characteristics, establishes the first evidence in humans for the existence of an excitatory cardiac-muscle sympathetic reflex activated by increasing atrial pressure.

Effect of fitness on reflex sympathetic neurovascular transduction in middle-age men

PURPOSE

Muscle sympathetic nerve activity (MSNA) is increased in older endurance-trained men, yet the reflex sympathetic forearm vasoconstrictor response to graded lower body negative pressure (LBNP) diminishes with age. The aim of this study was to assess the influence of aerobic exercise capacity on this altered neurovascular coupling. We hypothesized that during graded LBNP, the forearm vascular resistance (FVR)-MSNA relationship would be steeper in sedentary versus fit men.

METHODS

We therefore studied 20 healthy middle-age men (age = 52 ± 2 yr, mean ± SE), 10 physically active (FIT) and 10 sedentary (SED) (129% ± 4% vs 85% ± 3% of predicted peak oxygen uptake) during 4 min each of LBNP at -5, -10, -20, and -40 mm Hg, applied in a random order. We determined HR, plasma norepinephrine, and MSNA (microneurography) and derived FVR from blood pressure and forearm blood flow (plethysmography). The FVR-MSNA relationship was determined by linear regression in each group separately, and groups were compared using multiple linear regression.

RESULTS

MSNA burst frequency and FVR at rest and during LBNP (P < 0.003) were similar in the two groups, whereas HR was significantly lower (P < 0.002) both at rest and during LBNP in FIT men (P < 0.05). FVR during LBNP correlated positively with MSNA in the SED group (r = 0.44, P < 0.001) but not in the FIT group (r = 0.19, P = 0.10). Multiple linear regression confirmed that both MSNA (P < 0.001) and fitness level (P = 0.04) contribute to the forearm vascular response.

CONCLUSIONS

Thus, during simulated orthostasis, middle-age SED men exhibit a significant FVR-MSNA relationship, which is not evident in age-matched FIT men. This alteration in neurovascular coupling may potentially affect cardiovascular risk in middle-age men.

The role of atrial natriuretic peptide in modulating cardiac electrophysiology

Since the discovery of atrial natriuretic peptide (ANP) in 1981, significant progress has been made in understanding the mechanism of its release and its role in salt and water balance in the body. It has also become clear that ANP plays a key role in cardiac electrophysiology, modulating the autonomic nervous system and regulating the function of cardiac ion channels. The clinical importance of this role was established when mutations in NPPA, the gene encoding ANP, were identified as a cause of familial atrial fibrillation. This review examines our current understanding of the electrophysiological effects of ANP, and their physiological relationship to clinical studies linking ANP and atrial fibrillation.

S100B and brain natriuretic peptide predict functional neurological outcome after intracerebral haemorrhage

OBJECTIVE

To determine the predictive value of S100b and brain natriuretic peptide (BNP) in order to determine accurately and quickly a discharge prognosis after primary supratentorial intracerebral haemorrhage (ICH).

METHODS

After IRB approval and informed consent, blood samples were obtained and analysed from 28 adult patients consecutively admitted to the neuroscience intensive care unit with computed tomography-proven supratentorial ICH from June 2003 and December 2004 within the first 24 h after symptom onset for S100b and BNP. Functional outcomes on discharge were dichotomized to favourable (mRS < 3) or unfavourable.

RESULTS

BNP (a neurohormone) and S100b (a marker of glial activation) were found to be independently highly predictive of functional neurological outcome at the time of discharge as measured by the modified Rankin Score (BNP: p < 0.01, r = 0.46; S100b: p < 0.01, r = 0.42) and the Barthel Index (BNP: p < 0.01, r = 0.54; s100b: p < 0.01, r = 0.50). Although inclusion of either biomarker produced additive value when included with traditional clinical prognostic variables, such as the ICH score (Barthel index: p < 0.01, r = 0.66; mRS: p < 0.01, r = 0.96), little predictive power is added with inclusion of both biomarkers in a regression model for neurological outcome.

CONCLUSIONS

Serum S100b and BNP levels in the first 24 h after injury accurately predict neurological function at discharge after supratentorial ICH.

Dissociation between reflex sympathetic and forearm vascular responses to lower body negative pressure in heart failure patients with coronary artery disease

Many heart failure (HF) patients exhibit paradoxical forearm vasodilation when central blood volume is reduced by lower body negative pressure (LBNP). We tested the hypothesis that this response results from reflex sympathetic withdrawal. We recorded simultaneously forearm blood flow, muscle sympathetic nerve activity (MSNA), and plasma norepinephrine (PNE) during four random applications of LBNP, -5, -10, -20, and -40 mmHg, in 12 men with HF (mean left ventricular ejection fraction = 24 + or - 2%) and 10 healthy, normal, age-matched men (N). Compared with N, MSNA burst frequency (P = 0.001) and PNE (P = 0.005) were significantly higher in the HF group, both at rest and during LBNP. As anticipated in N, LBNP -40 mmHg significantly increased MSNA (+14.2 + or - 2.5 bursts/min; P < 0.05) and PNE (+0.83 + or - 0.22 nmol/l; P < 0.05) and decreased forearm vascular conductance (FVC) (-11.7 + or - 3.2 ml.min(-1).mmHg(-1); P < 0.05). In the HF group, LBNP elicited similar increases in MSNA (+11.5 + or - 2.0; P < 0.05) and PNE (+0.85 + or - 0.12; P < 0.05), without affecting FVC significantly (-4.1 + or - 2.4; P = 0.01 vs. N, interaction P = 0.03). However, within the HF group, responses were bimodal: LBNP -40 mmHg increased MSNA in all subjects (P < 0.001), yet the six patients with nonischemic or dilated cardiomyopathy (DCM) exhibited significant vasoconstriction (decrease in FVC; P = 0.001), whereas the six patients with ischemic cardiomyopathy (ICM) exhibited significant vasodilation (increase in FVC; P < 0.02 vs. DCM and N; interaction P = 0.02). Cold pressor testing increased MSNA and decreased FVC in ICM (n = 4). Thus paradoxical forearm vasodilator responses to LBNP in HF are not mediated by reflex sympathetic withdrawal. ICM and DCM patients differ qualitatively in their vascular responses to hypotensive LBNP.

Human atrial natriuretic peptide suppresses torsades de pointes in rabbits

BACKGROUND

The increase in inward current, primarily L-type Ca2+ current, facilitates torsades de pointes (TdP). Because human atrial natriuretic peptide (ANP) moderates the L-type Ca2+ current, in our study it was hypothesized that ANP counteracts TdP.

METHODS AND RESULTS

We tested the effect of ANP, guanosine 3', 5'-cyclic monophosphate analogue (8-bromo cGMP) and hydralazine on the occurrence of TdP in a rabbit model. In control rabbits, administration of methoxamine and nifekalant almost invariably caused TdP (14/15). In contrast, ANP (10 microg . kg(-1) . min(-1)) markedly abolished TdP (2/15), whereas hydralazine failed to show a comparable anti-arrhythmic action (10/15). TdP occurred only in 1 of 15 rabbits treated with 8-bromo cGMP. Presence of early afterdepolarization-like hump in the ventricular monophasic action potential was associated with the occurrence of TdP.

CONCLUSION

Results suggest that ANP affects TdP in the rabbit model, and that this anti-arrhythmic effect of ANP is not necessarily shared by other vasodilating agents.

Comparison of enzymatic recycling electrodes for measuring aminophenol: development of a highly sensitive natriuretic peptide assay system

Several redox enzymes were examined for enzymatic/electrochemical-recycling systems in order to measure p-aminophenol (PAP) with high sensitivity. Glucose oxidase (GOD) and diaphorase (DI) worked well as catalysts for recycling electrode systems: these enzymes effectively reduced p-iminoquinone (PIQ), the electrochemically-oxidized form of PAP, and caused an enhancement in the electrochemical signals (anodic currents in the voltammogram and amperogram) by approximately 100 fold. The lower detection limits for PAP were estimated to be 50 nM with the GOD system and 2 nM with the DI system. We combined the enzymatic-recycling electrode using DI with an enzyme immunoassay system to measure atrial natriuretic peptide (ANP), an important marker peptide hormone involved in heart diseases. ANPs from serum samples at ppt-levels were determined appropriately using the present assay system.

Dose-related effects of red wine and alcohol on hemodynamics, sympathetic nerve activity, and arterial diameter

The cardiovascular benefits of light to moderate red wine consumption often have been attributed to its polyphenol constituents. However, the acute dose-related hemodynamic, vasodilator, and sympathetic neural effects of ethanol and red wine have not been characterized and compared in the same individual. We sought to test the hypotheses that responses to one and two alcoholic drinks differ and that red wine with high polyphenol content elicits a greater effect than ethanol alone. Thirteen volunteers (24–47 yr; 7 men, 6 women) drank wine, ethanol, and water in a randomized, single-blind trial on three occasions 2 wk apart. One drink of wine and ethanol increased blood alcohol to 38 ± 2 and 39 ± 2 mg/dl, respectively, and two drinks to 72 ± 4 and 83 ± 3 mg/dl, respectively. Wine quadrupled plasma resveratrol ( P < 0.001) and increased catechin ( P < 0.03). No intervention affected blood pressure. One drink had no heart rate effect, but two drinks of wine increased heart rate by 5.7 ± 1.6 beats/min; P < 0.001). Cardiac output fell 0.8 ± 0.3 l/min after one drink of ethanol and wine (both P < 0.02) but increased after two drinks of ethanol (+0.8 ± 0.3 l/min) and wine (+1.2 ± 0.3 l/min) ( P < 0.01). One alcoholic drink did not alter muscle sympathetic nerve activity (MSNA), while two drinks increased MSNA by 9–10 bursts/min ( P < 0.001). Brachial artery diameter increased after both one and two alcoholic drinks ( P < 0.001). No beverage augmented, and the second wine dose attenuated ( P = 0.02), flow-mediated vasodilation. One drink of ethanol dilates the brachial artery without activating sympathetic outflow, whereas two drinks increase MSNA, heart rate, and cardiac output. These acute effects, which exhibit a narrow dose response, are not modified by red wine polyphenols.

Metabolic regulation: effects of natriuretic peptide interactions

In addition to their well-established effects on blood pressure and volume homeostasis, natriuretic peptides have complex effects on carbohydrate and lipid metabolism. In vivo, pharmacological and physiological concentrations of atrial natriuretic peptides induce lipolysis in a concentration-dependent manner and increase the lipid oxidation rate. The response appears to be mediated through the stimulation of natriuretic peptide receptor-A. More recent studies suggest that natriuretic peptides also affect the production of several adipokines. These mechanisms may be relevant, as natriuretic peptide availability is altered in numerous physiological and pathological conditions, including physical exercise, congestive heart failure and obesity.

Comparison of N-terminal pro-brain natriuretic peptide versus electrophysiologic study for predicting future outcomes in patients with an implantable cardioverter defibrillator after myocardial infarction

The aim of the study was to examine the predictive value of N-terminal pro-brain natriuretic peptide (NT-pro-BNP) versus electrophysiologic study in patients with implantable cardioverter-defibrillators (ICDs) after myocardial infarction (MI). We prospectively studied 99 consecutive patients with a history of MI who underwent ICD implantation for primary or secondary prevention of sudden cardiac death. An electrophysiologic study was performed in all patients. Venous blood samples for NT-pro-BNP measurement were obtained at the beginning of the study. The primary end point was ventricular tachycardia or ventricular fibrillation (VT/VF) and the secondary end point was a composite of death, hospitalization for heart failure, or MI. On multivariate Cox regression analysis, NT-pro-BNP level at or greater than median (497 ng/L) was the only significant predictor for VT/VF occurrence (p = 0.047). Along with amiodarone use (p = 0.001), NT-pro-BNP levels higher than median were also associated with a higher risk of composite clinical events (p = 0.036). Kaplan-Meier analysis showed that patients with NT-pro-BNP level at or greater than median had a higher risk of experiencing VT/VF and composite clinical events than patients with NT-pro-BNP levels less than median (log-rank p <0.05). In conclusion, assay of NT-pro-BNP, which is easy to perform and widely available, is superior to electrophysiologic study for prediction of future outcomes in predominantly secondary prophylactic ICD recipients after MI. In the era of primary prophylactic ICD implantation without preimplantation electrophysiologic study, higher NT-pro-BNP levels might help to improve risk-adjusted concomitant antiarrhythmic therapy and device selection.

Beta-adrenergic and atrial natriuretic peptide interactions on human cardiovascular and metabolic regulation

CONTEXT

Atrial natriuretic peptide (ANP) has well-known cardiovascular effects and modifies lipid and carbohydrate metabolism in humans.

OBJECTIVE

The objective of the study was to determine the metabolic and cardiovascular interaction of beta-adrenergic receptors and ANP.

DESIGN

This was a crossover study, conducted 2004-2005.

SETTING

The study was conducted at an academic clinical research center.

PATIENTS

PATIENTS included 10 healthy young male subjects (body mass index 24 +/- 1 kg/m2).

INTERVENTION

We infused iv incremental ANP doses (6.25, 12.5, and 25 ng/kg.min) with and without propranolol (0.20 mg/kg in divided doses followed by 0.033 mg/kg.h infusion). Metabolism was monitored through venous blood sampling, im, and sc microdialysis and indirect calorimetry. Cardiovascular changes were monitored by continuous electrocardiogram and beat-by-beat blood pressure recordings.

MAIN OUTCOME MEASURES

Venous nonesterified fatty acid, glycerol, glucose, and insulin; and microdialysate glucose, glycerol, lactate, and pyruvate were measured.

RESULTS

ANP increased heart rate dose dependently. beta-Adrenergic receptor blockade abolished the response. ANP elicited a dose-dependent increase in serum nonesterified fatty acid and glycerol concentrations. The response was not suppressed with propranolol. Venous glucose and insulin concentrations increased with ANP, both without or with propranolol. ANP induced lipid mobilization in sc adipose tissue. In skeletal muscle, microdialysate lactate increased, whereas the lactate to pyruvate ratio decreased, both with and without propranolol. Higher ANP doses increased lipid oxidation, whereas energy expenditure remained unchanged. Propranolol tended to attenuate the increase in lipid oxidation.

CONCLUSIONS

Selected cardiovascular ANP effects are at least partly mediated by beta-adrenergic receptor stimulation. ANP-induced changes in lipid mobilization and glycolysis are mediated by another mechanism, presumably stimulation of natriuretic peptide receptors, whereas substrate oxidation might be modulated through adrenergic mechanisms.

Caffeine Prolongs Exercise Duration in Heart Failure

BACKGROUND

Caffeine increases submaximal exercise performance in healthy young subjects; its effects on exercise tolerance in heart failure (HF) have not been characterized.

METHODS AND RESULTS

To determine whether caffeine increases exercise tolerance in HF, caffeine (4 mg/kg intravenously, equivalent to 2 cups of coffee) or vehicle were infused into 10 treated HF patients (left ventricular ejection fraction 25 +/- 2 %), and 10 age-matched normal subjects (N) on 2 separate days in a double-blind, randomized, crossover design. We measured heart rate, blood pressure, and ventilation at rest and during graded cycling (15 W/minute) to peak effort. Peak oxygen consumption was unaffected in either group. Mean exercise time was unchanged in N (1,013 +/- 87 versus 988 +/- 107 seconds; P = .86) but was significantly increased by caffeine in HF (from 511 +/- 28 to 560 +/- 37 seconds; P = .004) despite an increase in peak minute ventilation (P < .05). Resting and peak blood pressures were higher after caffeine (P < .05) in HF, not N.

CONCLUSION

Caffeine allows HF patients to exercise longer at peak effort.

Atrial natriuretic peptide has dose-dependent, autonomically mediated effects on atrial refractoriness and repolarization in anesthetized dogs

INTRODUCTION

Atrial natriuretic peptide (ANP) may alter electrophysiological properties of the heart and possibly have a role in arrhythmogenesis. However, previous studies have yielded conflicting results and have not fully considered whether ANP's cardiac electrophysiological effects are mediated via direct actions and/or indirectly via the autonomic nervous system. This study's aim was to establish whether ANP infused at pathophysiological and pharmacological doses has significant in vivo cardiac electrophysiological effects and to determine whether these effects are directly or autonomically mediated.

METHODS AND RESULTS

Electrophysiologic and hemodynamic effects of ANP infusion (human ANP at 15-600 ng/kg per minute) were examined in chloralose-anesthetized dogs under conditions of varying autonomic blockade. In autonomically intact dogs (n = 12), low-dose ANP (15 ng/kg per minute) shortened atrial effective refractory period (ERP) (P < 0.001) and monophasic action potential duration (MAPD90) (P < 0.05) at 600, 500, and 400 msec atrial paced cycle lengths and reduced right atrial pressure (P < 0.05) but did not alter mean arterial pressure. After either combined vagal and beta-adrenergic blockade (vagotomy plus atropine plus propranolol, n = 7) or selective vagal blockade (n = 9), low-dose ANP no longer altered atrial ERP or MAPD90. Higher ANP doses (150 and 600 ng/kg per minute) decreased mean arterial and right atrial pressures (P < 0.001) but did not alter atrial ERP, MAPD90, or other electrophysiological parameters including atrial fibrillation threshold, ventricular ERP, and MAPD90.

CONCLUSION

ANP has dose-dependent, autonomically mediated effects on atrial refractoriness and repolarization.

Time Course and Prognostic Value of Plasma Levels of N-Terminal Pro-Brain Natriuretic Peptide in Patients After Ischemic Stroke

BACKGROUND

The association between plasma levels of N-terminal pro-brain natriuretic peptide (NT-proBNP) and prognostic outcomes in patients after ischemic stroke remains unknown. The present study tested the hypothesis that NT-proBNP level is noticeably increased after ischemic stroke and that elevated NT-proBNP is associated with unfavorable clinical outcomes (UFCO).

METHODS AND RESULTS

Blood samples for NT-proBNP levels were collected serially and examined with sandwich immunoassay after acute ischemic stroke in 86 consecutive patients. The NT-proBNP levels were also measured in 30 healthy control volunteers and 30 at-risk control subjects. The NT-proBNP levels were significantly higher at 4 intervals after ischemic stroke than in healthy and at-risk control subjects (all p<0.001). The NT-proBNP decreased to a significantly lower level on day 21 and to a substantially lower level on day 90. Additionally, the NT-proBNP level at any of the 4 intervals was significantly higher in patients with than in patients without UFCO (defined as combined congestive heart failure > or = class 3, acute myocardial infarction, recurrent stroke or any cause of death) (all p<0.01). Multivariate analysis demonstrated that age and NIH Stroke Scale were the 2 strongest independent predictors of increased NT-proBNP levels (all p<0.01). Furthermore, increased NT-proBNP (> or = 150 pg/ml) was the strongest independent predictor of long-term (mean follow-up: 24 months) UFCO (26 patients) (all p<0.05).

CONCLUSIONS

The NT-proBNP level was markedly elevated after acute ischemic stroke and declined substantially thereafter. An increased NT-proBNP level was strongly and independently correlated with UFCO in patients after ischemic stroke.

N-Terminal Pro-Brain Natriuretic Peptide is a Biomarker of Congestive Heart Failure and Predictive of 30-Day Untoward Clinical Outcomes in Patients With Acute Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention

BACKGROUND

Increased levels of N-terminal pro-brain natiuretic peptide (NT-proBNP) are now recognized as a new and useful biochemical marker that is predictive of clinical outcomes in patients with congestive heart failure (CHF). However, an association between an increased circulating level of this biomarker and clinical outcomes in patients following acute myocardial infarction (AMI) has not been fully delineated. Thus, the purpose of this study was to test whether NT-proBNP can predict prognosis in patients following ST-segment elevated AMI.

METHODS AND RESULTS

A prospective cohort study of 242 consecutive patients with ST-segment elevated AMI of onset <12 h who underwent primary percutaneous coronary intervention (PCI) was conducted. Blood samples for plasma concentration of NT-proBNP were collected following vascular puncture. Univariate analysis demonstrated that the 30-day composite major adverse clinical outcomes (MACO) [advanced Killip score > or =3, functional class > or =3 of CHF and 30-day mortality] were strongly associated with elevated NT-proBNP (>243 pg/ml) (p<0.0001), unsuccessful reperfusion (final thrombolysis in myocardial infarction flow < or =2) (p<0.0001), left ventricular ejection fraction (LVEF) <45% (p<0.0001), diabetes mellitus (DM) (p=0.0004) and multivessel disease (p=0.0005). Multiple stepwise logistic regression analysis demonstrated that elevation of NT-proBNP (p=0.0002), LVEF < 45% (p=0.0003), DM (p=0.0007), unsuccessful reperfusion (p=0.006), and age (> or =70 years) (p=0.031) are independent predictors of 30-day MACO. Additionally, elevation of NT-proBNP, together with advanced Killip score and unsuccessful reperfusion, are significant independent predictors of increased 30-day mortality (all p values <0.005).

CONCLUSION

Increased NT-proBNP level was the most independent predictor of 30-day MACO in patients with ST-segment elevated AMI undergoing primary PCI.

The interaction of plasma renin activity and plasma atrial natriuretic peptide in 21-hydroxylase deficiency patients

Plasma renin activity (PRA) determination is the main index used to evaluate the mineralocorticoid control in 21-hydroxylase deficiency (21-OHD). PRA values within or at the upper limit of the age-appropriate range, or values <5 or 10 ng/ml/h have been regarded as adequate control. Atrial natriuretic peptide (ANP) has opposite actions to those of angiotensin II/aldosterone, and could help to understand the hydrosaline homeostasis in 21-OHD. We studied the interaction between PRA and ANP levels in 10 controls and 26 patients with 21-OHD under corticoid treatment. Patients were divided into two groups according to PRA levels, < or > or = 5 ng/ml/h, irrespective of the clinical form of 21-OHD. Blood samples for determination of PRA and ANP levels were taken after 30 min in the sitting position (basal), after 30 min in the recumbent position and after 15 min of 20 degrees head-down tilting. ANP levels (pg/ml) in the basal, supine and after head-down tilting position were 25.9 +/- 1.6, 42.7 +/- 7.4 and 54.3 +/- 5.5 in controls; 28.5 +/- 2.1, 38.3 +/- 2.1 and 48.8 +/- 4.1 in the group with PRA levels <5 ng/ml/h, and 20.9 +/- 1.9, 26.6 +/- 2.5 and 34.6 +/- 3.1 in the group with PRA levels > or = 5 ng/ml/h, respectively. Basal and after head-down tilting ANP plasma levels were similar between the controls and the group with PRA levels <5 ng/ml/h. However, the group of patients with PRA levels > or = 5 ng/ml/h showed lower basal and stimulated ANP levels compared to the control group (p<0.05). The decreased plasma ANP levels in the basal condition and after head-down tilting indicate a chronic contraction of the extracellular volume in 21-OHD patients with increased PRA levels. Therefore, mineralocorticoid deficiency is counteracted by decreased ANP secretion in order to preserve fluid and electrolyte homeostasis.

Cardioprotective functions of atrial natriuretic peptide and B-type natriuretic peptide: a brief review

1. If one was to design a hormone to protect the heart, it would have a number of features shown by the cardiac natriuretic peptides atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP). These hormones are made in cardiomyocytes and are released into the circulation in response to atrial and ventricular stretch, respectively. Atrial natriuretic peptide and BNP can reduce the preload and after-load in normal and failing hearts. They reduce blood volume over the short term by sequestering plasma and over the longer term by promoting renal salt and water excretion and by antagonizing the renin-angiotensin-aldosterone system at many levels. Each of these actions affords indirect benefit to a volume- or pressure-threatened heart. 2. Recent studies have identified additional modes of action of the natriuretic peptides that may also confer cardioprotective benefits, especially in heart disease. The emerging findings are: (i) that ANP and BNP antagonize the cardiac hypertrophic action of angiotensin II and continue working under conditions where endothelial nitric oxide (NO) function is compromised, such as in the presence of high glucose in diabetes; (ii) they potentiate the bradycardia caused by inhibitory ('autoprotective') cardio-cardiac reflexes; and, furthermore, (iii) BNP can suppress cardiac sympathetic nerve activity in humans, including those with heart failure. Thus, it appears that natriuretic peptides can shift sympathovagal balance in a beneficial direction (away from the sympathetic). The vagal reflex and antihypertrophic actions of the peptides are mediated by particulate guanylyl cyclase (pGC) natriuretic peptide receptors. 3. The multiple synergistic actions of the natriuretic peptides make them and their pGC receptors attractive targets for therapy in heart disease. Encouragingly, exogenous natriuretic peptides remain effective even when endogenous peptide levels are raised, as is the case in heart failure. They also remain effective in disease states where other protective mechanisms, such as the NO system, have become ineffective, offering yet further encouragement for the therapeutic use of the natriuretic peptides.

Effect of nesiritide (human b-type natriuretic peptide) and dobutamine on heart rate variability in decompensated heart failure

BACKGROUND

Previous studies have suggested that natriuretic peptides may have direct sympathoinhibitory effects. Nesiritide (recombinant human B-type natriuretic peptide) has been recently approved for treatment of decompensated congestive heart failure (CHF). We sought to assess the effects of nesiritide compared with dobutamine on time-domain indices of heart rate variability (HRV) in patients with decompensated CHF.

METHODS

The study population consisted of 185 patients, who were randomized to intravenous nesiritide at a low (0.015 microg/kg/min, n = 56) or high (0.03 microg/kg/min, n = 58) dose, or to dobutamine (> or = 5 microg/kg/min, n = 58). Time-domain HRV indices were obtained from 24-hour Holter recordings immediately before and during study drug therapy.

RESULTS

Dobutamine therapy resulted in a decrease in standard deviation of the R-R intervals over a 24-hour period (SDNN), standard deviation of all 5-minute mean R-R intervals (SDANN), and the percentage of R-R intervals with >50 ms variation (pNN50) (all P < .05). Low-dose nesiritide induced an increase in SDNN (P < .05), and high-dose nesiritide resulted in a nonsignificant decrease in all measures of HRV. A significant interaction was noted between baseline HRV and the effect of vasoactive therapy on HRV (P = .028). Therefore, the effect of nesiritide and dobutamine was analyzed in relation to baseline HRV. In the dobutamine group, patients with moderately depressed HRV at baseline displayed a reduction in SDNN (P = .01), SDANN (P = .01), pNN50 (P = .04), and the square root of mean squared differences of successive R-R intervals (RMSSD) (P = .05), whereas no significant changes occurred in patients with severely depressed HRV. In the low-dose nesiritide group, patients with severely depressed HRV displayed an increase in SDNN (P = .001), SDANN (P = .02), and RMSSD (P = .01), with no significant changes in patients with moderately depressed HRV. HRV response to high-dose nesiritide was similar to that of dobutamine.

CONCLUSIONS

Low-dose nesiritide therapy in patients with decompensated CHF improves indices of overall HRV and parasympathetic modulation, particularly if HRV is severely depressed at baseline. Dobutamine and possibly high-dose nesiritide can potentially lead to further deterioration of autonomic dysregulation.

Insuffisances cardiaques d’origine médicamenteuse (en dehors des anthracyclines)

The principal drugs implicated in or disclosing cardiac insufficiency are drawn from a review of the literature and observations by the French national pharmacovigilance database, from 1984 to April 2003. Several pharmacological classes are identified: in addition to antimitotic drugs, such as anthracyclines, many drugs are implicated in cardiac insufficiency, e.g. immunomodulators, anti-inflammatory drugs (including coxibs), antiarrhythmic drugs, anaesthetic drugs, antipsychotic drugs, and antidiabetic drugs (including glitazones). It is usual to classify these drugs according to three categories: (i) drugs likely to cause cardiac insufficiency de novo (such as cyclophosphamide, paclitaxel, mitoxantrone, interferons, interleukin-2 etc.); (ii) drugs likely to worsen preexisting cardiac insufficiency (such as antiarrhythmics, beta-blockers, calcium antagonists, nonsteroidal and steroidal anti-inflammatory drugs, sympathomimetic drugs etc.); and (iii) drugs only occasionally causing cardiac insufficiency. This review shows that this classification is, in fact, artificial. If cardiac toxicity is a constant concern when using antimitotic drugs or some immunomodulator drugs, it is advisable to exercise caution in the use of many other drugs when treating patients with cardiac insufficiency, even if the clinical situation is well controlled. In particular, drug-drug interactions and patient medical history must be taken into account.

B-type natriuretic peptide in cardiovascular disease

Natriuretic peptide hormones, a family of vasoactive peptides with many favourable physiological properties, have emerged as important candidates for development of diagnostic tools and therapeutic agents in cardiovascular disease. The rapid incorporation into clinical practice of bioassays to measure natriuretic peptide concentrations, and drugs that augment the biological actions of this system, show the potential for translational research to improve patient care. Here, we focus on the physiology of the natriuretic peptide system, measurement of circulating concentrations of B-type natriuretic peptide (BNP) and the N-terminal fragment of its prohormone (N-terminal BNP) to diagnose heart failure and left ventricular dysfunction, measurement of BNP and N-terminal BNP to assess prognosis in patients with cardiac abnormalities, and use of recombinant human BNP (nesiritide) and vasopeptidase inhibitors to treat heart failure.

High plasma levels of N-terminal pro-atrial natriuretic peptide associated with low anxiety in severe heart failure

OBJECTIVE

Plasma levels of natriuretic peptides are elevated in congestive heart failure (CHF). These peptides show anxiolytic properties in studies of rodents and patients with panic disorder, but their possible effect on anxiety has never been studied in cardiac patients. We therefore assessed associations of the Atrial Natriuretic Pro-Peptide (pro-ANP) with anxiety in patients with CHF and controls.

METHOD

This was a cross-sectional study of 119 patients (46 with CHF, 76 controls with cardiovascular risk factors) in a tertiary care center. The study included assessment of CHF severity, ejection fraction, pro-ANP (microtiter assay), and psychosocial status (self-rating questionnaires for anxiety, depression, vital exhaustion, and quality of life).

RESULTS

The diagnosis and severity of CHF was significantly related to pro-ANP levels, bad physical quality of life, vital exhaustion, and depression. However, there was no significant effect of disease severity on anxiety. In CHF patients, pro-ANP was negatively correlated with anxiety (rho = -0.30, p =.041). In the whole group, anxiety was independently predicted by vital exhaustion, depression, and younger age (overall adjusted R2 = 0.48). Pro-ANP plasma levels showed an additional, inverse association with anxiety (beta = -0.17, p =.013, adjusted R2 = 0.50). Predicted mean anxiety scores derived from this model showed a good fit with anxiety scores observed in subgroups defined by CHF severity.

CONCLUSION

Pro-ANP plasma levels are independently and inversely related to anxiety. Even in severe CHF with severely compromised quality of life, anxiety tends to decrease with high pro-ANP levels. This might be part of a negative feedback loop limiting psychological distress and its adverse autonomic consequences in severe heart failure.

The therapeutic effect of natriuretic peptides in heart failure; differential regulation of endothelial and inducible nitric oxide synthases

The abnormal regulation of nitric oxide synthase activity represents an underlying feature of heart failure. Increased peripheral vascular resistance, and decreased renal function may be in part related to impaired endothelium-dependent nitric oxide (NO) synthesis. Paradoxically, the chronic production of NO by inducible nitric oxide synthase (iNOS) in heart failure exerts deleterious effects on ventricular contractility, and circulatory function. Consequently, pharmacologically improving endothelium-dependent NO synthesis and the concomitant inhibition of iNOS activity would be therapeutically advantageous. Interestingly, natriuretic peptides have been shown to differentially regulate endothelial NOS (eNOS) and iNOS activity. Moreover, in both patients and animal models of heart failure, pharmacologically increasing plasma natriuretic peptide levels ameliorated vascular tone, renal function, and ventricular contractility. Based on these observations, the following review will explore whether the therapeutic benefit of the natriuretic peptide system in heart failure may occur in part via the amelioration of endothelium-dependent NO synthesis, and the concomitant inhibition of cytokine-mediated iNOS expression.

Exercise prescription based upon cardiac vagal activity for middle-aged obese women

OBJECTIVE

The purposes of this study were to examine a new method to determine exercise intensity for obese people based on the cardiac vagal activity and to determine the effect of this approach on myocardial stress.

SUBJECTS

Forty-three middle aged obese female volunteers (age 43.7+/-6.5 y; height 1.56+/-0.05 m; body mass 66.5+/-9.3 kg; body mass index 27.3+/-2.8 kg m(2); percentage body fat 40.7+/-5.9%).

MEASUREMENT

In the first experiment, 43 subjects performed a ramp exercise test on a bicycle ergometer with measurement of ECG and gas exchange parameters. In the second experiment, 11 subjects performed 45 min of constant walking exercise on a treadmill at a level corresponding to exercise intensity determined by vagal activity obtained from a ramp bicycle test. Blood pressure, endothelin 1 (ET-1), catecholamine, atrial natriuretic peptide (ANP), and brain natriuretic peptide (BNP) were measured before and after exercise.

RESULTS

The heart rate variability power decreased with increasing work rate, and changed little after reaching individual-specific work rate. We presumed that vagal activity disappeared at this point and that the heart rate at this exercise intensity was determined as the vagal activity threshold (T(VA)). The results showed a significant positive correlation (r=0.742, P<0.0001) between T(VA) and ventilatory threshold (VT) heart rates, although the mean heart rate of T(VA) (114.3+/-8.5 beats/min) was significantly lower (P<0.001) than that at VT (119.0+/-11.7), suggesting the cardiac vagal withdrawal occurred prior to the onset of lactate acidosis (lactic acid accumulation). Furthermore, exercise intervention experiment at T(VA) indicated that ET-1, catecholamine and BNP levels were not significantly different before and after exercise. However, ANP levels increased significantly after exercise (pre-exercise 18.6+/-5.38 vs post-exercise 44.0+/-24.87 pg/ml, P<0.001), which in turn brought about a significant post-exercise reduction in the blood pressure (SBP 117.6+/-13.7 vs 110.5+/-7.4 mmHg, P<0.05; DBP 78.6+/-6.7 vs 73.5+/-6.6 mmHg, P<0.01).

CONCLUSION

Our data suggest that it is possible to determine the exercise intensity (T(VA)) on the basis of cardiac vagal response. These results also suggest that exercise at T(VA) level is a safe exercise intensity in the light of cardiac stress, and that T(VA) may be recommended for obese people who might possess lower cardiac sympatho-vagal activity.

B-type natriuretic peptide as a marker of the effects of enalapril in patients with heart failure

BACKGROUND

A-Type and B-type natriuretic peptides are cardiac hormones whose circulating levels reflect the severity of heart failure. It is not known how plasma levels of these hormones respond to changes in cardiac function that occur as a result of treatment with angiotensin-converting enzyme (ACE) inhibitors.

METHODS

Enalapril was administered at 5 mg/d for 3 months in 24 patients with chronic heart failure, and for the next 3 months at 15 mg/d in the high-dose group (n = 12) and 5 mg/d in the low-dose group (n = 12). We measured plasma levels of A-type or B-type natriuretic peptides, as well as conventional measures of cardiac function, such as the cardiothoracic ratio, left ventricular end-diastolic volume, and percent fractional shortening.

RESULTS

Mean (+/- SD) plasma levels of both hormones decreased promptly after 2 weeks of therapy (A-type natriuretic peptide: 140 +/- 107 pg/mL to 81 +/- 68 pg/mL, P = 0.01; B-type natriuretic peptide: 305 +/- 278 pg/mL to 190 +/- 178 pg/mL, P = 0.01). These reductions were sustained throughout therapy. In contrast, the cardiothoracic ratio, left ventricular end-diastolic dimension, and percent fractional shortening had not changed significantly after 3 months of treatment, although improvements were seen after 6 months of treatment. After 6 months, plasma levels of both A-type and B-type natriuretic peptides were significantly lower in the high-dose group than in the low-dose group (A-type natriuretic peptide: 48 +/- 25 pg/mL vs. 57 +/- 27 pg/mL, P = 0.01; B-type natriuretic peptide: 78 +/- 58 pg/mL vs. 139 +/- 61 pg/mL, P = 0.005), whereas no significant differences were observed in the other measures of cardiac function.

CONCLUSION

Plasma levels of A-type and B-type natriuretic peptides appear to be more sensitive markers of heart failure than conventional echocardiographic parameters and cardiothoracic ratios. Measurement of these hormones might be useful for monitoring the effects of treatment with ACE inhibitors.

ANP potentiates nonarterial baroreflex bradycardia: evidence from sinoaortic denervation in rats

Previous findings indicate that atrial natriuretic peptide (ANP) enhances the reflex bradycardia arising from stimulation of cardiac mechanoreceptors and chemoreceptors, but not that from arterial baroreceptors. The present study tests this proposal by examining the effect of ANP on these reflexes in six chronically sinoaortic-denervated (SAD), and eight sham-operated (sham), conscious rats. Arterial baroreceptor-heart rate (HR) reflex function was examined by constructing full-range steady-state blood pressure (BP)-HR curves using alternating doses of pressor (methoxamine, 2-100 microg/kg) and depressor (nitroprusside, 1-50 microg/kg) agents. Nonarterial baroreceptor reflex function was assessed by the 'ramp' bradycardic response to the rapid BP rise after i.v. methoxamine (100 microg/kg bolus dose). The cardiopulmonary chemoreflex was evoked by i.v. injections of serotonin (1-20 microg/kg). These three tests were performed on each rat during infusions, in random order, of rat ANP (150 ng/kg/min i.v.) and saline vehicle. The ability of ANP to significantly enhance ramp reflex bradycardia was not diminished in SAD compared with sham rats (+54 +/- 12% vs. +42 +/- 15%, respectively). ANP also significantly enhanced cardiopulmonary chemoreflex bradycardia in both groups (+60 +/- 15% in SAD, +40 +/- 8% in sham). Neither the normal steady-state BP-HR response in sham rats nor the small residual response in SAD rats was enhanced by ANP (-1 +/- 7% in sham, -11 +/- 8% in SAD). We conclude that ANP enhances reflex bradycardias of nonarterial, probably cardiac mechanoreceptor, origin.

Effect of adenosine receptor blockade with caffeine on sympathetic response to handgrip exercise in heart failure

Adenosine (Ado) increases muscle sympathetic nerve activity (MSNA) reflexively. Plasma Ado and MSNA are elevated in heart failure (HF). We tested the hypothesis that Ado receptor blockade by caffeine would attenuate reflex MSNA responses to handgrip (HG) and posthandgrip ischemia (PHGI) and that this action would be more prominent in HF subjects than in normal subjects. We studied 12 HF subjects and 10 age-matched normal subjects after either saline or caffeine (4 mg/kg) infusion during isometric [30% of maximal voluntary contraction (MVC)] and isotonic (10%, 30%, and 50%) HG exercise, followed by 2 min of PHGI. In normal subjects, caffeine did not block increases in MSNA during PHGI after 50% HG. In HF subjects, caffeine abolished MSNA responses to PHGI after both isometric and 50% isotonic exercise (P < 0.05) but MSNA responses during HG were unaffected. These findings are consistent with muscle metaboreflex stimulation by endogenous Ado during ischemic or intense nonischemic HG in HF and suggest an important sympathoexcitatory role for endogenous Ado during exercise in this condition.