Suppression of hyperventilation-induced attacks with infusion of B-type (brain) natriuretic peptide in patients with variant angina

A Highly-sensitized Response of B-type Natriuretic Peptide to Cardiac Ischaemia Quantified by Intracoronary Pressure Measurements

B-type natriuretic peptide (BNP) secretion is stimulated by cardiac dysfunction. However, it is unclear how finely myocardial ischaemia contributes to BNP secretion and whether increases in BNP secretion contribute to coronary vasodilation. This study investigated the direct interaction between plasma BNP levels and cardiac ischaemia using the baseline distal-to-aortic pressure ratio (Pd/Pa). We examined the baseline Pd/Pa and fractional flow reserve (FFR) in 167 patients with intermediate coronary stenosis. The plasma BNP level appeared to be associated with the baseline Pd/Pa in the study population, and this association appeared to become clear only in patients with an FFR ≤ 0.80. To examine the effect of the baseline Pd/Pa on the BNP level in these patients, structural equation modeling (SEM) was performed. The baseline Pd/Pa significantly affected the BNP level (β: -0.37, p = 0.003) and the left ventricular ejection fraction (β: 0.43, p = 0.001). To examine the role of BNP in coronary vasodilation, we proposed another path model using a novel value obtained by dividing the FFR by the baseline Pd/Pa (FFR/baseline Pd/Pa) as an index of the hyperaemic response. The BNP level significantly affected the FFR/baseline Pd/Pa (β: 0.48, p = 0.037). This study demonstrated that BNP finely responded to an exacerbation of cardiac ischaemia and that increases in BNP secretion effectively ameliorated coronary vasoconstriction.

Atrial natriuretic peptide promotes cardiomyocyte survival by cGMP-dependent nuclear accumulation of zyxin and Akt

This study delineates a mechanism for antiapoptotic signaling initiated by atrial natriuretic peptide (ANP) stimulation leading to elevation of cGMP levels and subsequent nuclear accumulation of Akt kinase associated with zyxin, a cytoskeletal LIM-domain protein. Nuclear targeting of zyxin induces resistance to cell death coincident with nuclear accumulation of activated Akt. Nuclear translocation of zyxin triggered by cGMP also promotes nuclear Akt accumulation. Additional supportive evidence for nuclear accumulation of zyxin-enhancing cardiomyocyte survival includes the following: (a) promotion of zyxin nuclear localization by cardioprotective stimuli; (b) zyxin association with phospho-Akt473 induced by cardioprotective stimuli; and (c) recruitment of zyxin to the nucleus by activated nuclear-targeted Akt as well as recruitment of Akt by nuclear-targeted zyxin. Nuclear accumulation of zyxin requires both Akt activation and nuclear localization. Potentiation of cell survival is sensitive to stimulation intensity with high-level induction by ANP or cGMP signaling leading to apoptotic cell death rather than enhancing resistance to apoptotic stimuli. Myocardial nuclear accumulation of zyxin and Akt responds similarly in vivo following treatment of mice with ANP or cGMP. Thus, zyxin and activated Akt participate in a cGMP-dependent signaling cascade leading from ANP receptors to nuclear accumulation of both molecules. Nuclear accumulation of zyxin and activated Akt may represent a fundamental mechanism that facilitates nuclear-signal transduction and potentiates cell survival.

Effects of intravenous nesiritide on human coronary vasomotor regulation and myocardial oxygen uptake

BACKGROUND

Nesiritide, recombinant human B-type natriuretic peptide, has been shown to be efficacious in the treatment of decompensated heart failure. The effects of intravenous nesiritide on the human coronary vasculature have not been studied.

METHODS AND RESULTS

Ten patients underwent right and left heart catheterization. Baseline coronary blood flow was determined using quantitative coronary angiography (QCA) and an intracoronary Doppler-tipped guidewire. Myocardial oxygen uptake was measured using a coronary sinus catheter. Patients then received an intravenous infusion of nesiritide (2 microg/kg bolus followed by 0.01 microg/kg per min infusion) for 30 minutes. Right atrial pressure decreased 52% (P=0.012), pulmonary artery mean pressure decreased 19% (P=0.03), pulmonary capillary wedge pressure decreased 46% (P=0.002), and mean arterial pressure decreased 11% (P=0.007). QCA demonstrated a 15% increase in coronary artery diameter from a baseline of 2.6+/-0.8 to 3.0+/-0.8 mm at 30 minutes (P=0.007). The coronary velocity measure of average peak velocity increased 14% from 20.8+/-6.4 at baseline to 23.8+/-7.2 cm/s at 5 minutes (P=0.015) and then returned to baseline for the remainder of the infusion. Coronary blood flow increased 35% (P=0.007), whereas coronary resistance decreased 23% at 15 and 30 minutes (P=0.036). Myocardial oxygen uptake decreased 8% during the nesiritide infusion (P=0.043).

CONCLUSIONS

Nesiritide exerts coronary vasodilator effects on both the coronary conductance and resistance arteries. Despite a decrease in coronary perfusion pressure, coronary artery blood flow is increased, coronary resistance is decreased, and myocardial oxygen uptake is decreased.

BNP and congestive heart failure

Brain natriuretic peptide (BNP), a peptide hormone secreted chiefly by ventricular myocytes, plays a key role in volume homeostasis. The plasma concentration of BNP is raised in various pathological states, especially heart failure. Many studies suggest that measurement of plasma BNP has clinical utility for excluding a diagnosis of heart failure in patients with dyspnea or fluid retention and for providing prognostic information in those with heart failure or other cardiac disease. It may also be of value in identifying patients after myocardial infarction in whom further assessment of cardiac function is likely to be worthwhile. Preliminary evidence suggests that measuring the plasma concentration of BNP may be useful in fine tuning therapy for heart failure. Artificially raising the circulating levels of BNP shows considerable promise as a treatment for heart failure. With simpler assay methods now available, it is likely that many physicians will measure plasma BNP to aid them in the diagnosis, risk stratification, and monitoring of their patients with heart failure or other cardiac dysfunction.

ANP, BNP, and CNP enhance bradycardic responses to cardiopulmonary chemoreceptor activation in conscious sheep

We demonstrated previously that atrial natriuretic peptide (ANP) enhances reflex bradycardia to intravenous serotonin [5-hydroxytryptamine (5-HT)] (von Bezold-Jarisch reflex) in rats. To determine whether 1) ANP affects this cardiopulmonary vagal reflex in another species and 2) B-type (BNP) and C-type (CNP) natriuretic peptides share with ANP the ability to modulate this reflex, we used intravenous phenylbiguanide (PBG), a 5-HT(3) agonist, as the stimulus to evoke a von Bezold-Jarisch reflex (dose-related, reproducible bradycardia) in conscious adult sheep (n = 5). Three doses of PBG (13 +/- 3, 20 +/- 3, and 31 +/- 4 microg/kg) injected into the jugular vein caused reflex cardiac slowing of -7 +/- 1, -15 +/- 2, and -36 +/- 3 beats/min, respectively, under control conditions. These doses of PBG were repeated during infusions of ANP, BNP, or CNP (10 pmol. kg(-1). min(-1) iv), or vehicle (normal saline). Each of the natriuretic peptides significantly (P < 0.05) enhanced the sensitivity of bradycardic responses to PBG by 94 +/- 8% (ANP), 142 +/- 55% (BNP), and 61 +/- 16% (CNP). Thus not only did ANP sensitize cardiopulmonary chemoreceptor activation in a species with resting heart rate close to that in humans, but BNP and CNP also enhanced von Bezold-Jarisch reflex activity in conscious sheep.

Review of 10 years of the clinical use of brain natriuretic peptide in cardiology

Ten years ago brain natriuretic peptide (BNP), the second compound of a family of polypeptide hormones named natriuretic peptides was identified. This peptide has great pathophysiologic importance as a stress-induced cardiac hormone secreted from ventricles, and it rises in several cardiac diseases. It promotes natriuresis and diuresis, acts as a vasodilator, and antagonizes the vasoconstrictor effects of the renin-angiotensin-aldosterone system. The measurement of this peptide in blood by immunoassay has shown promise over the past decade in clinical diagnosis and prognosis. Because heart failure is a major health problem worldwide, BNP is proposed as a biochemical marker that might provide a useful screening test to select patients for further cardiac investigations. Such a hormone assay is inexpensive and available. The implications of BNP in diagnosis, prognosis, and therapy will be reviewed.

Natriuretic peptides: physiology, therapeutic potential, and risk stratification in ischemic heart disease

BACKGROUND

The natriuretic peptide family consists of four molecules that share significant amino acid sequence homologic characteristics and a looped motif. Atrial natriuretic peptide and brain natriuretic peptide are similar in their ability to promote natriuresis and diuresis, inhibit the renin-angiotensin-aldosterone axis, and act as vasodilators. Understanding of the actions of C-type natriuretic peptide and dendroaspis natriuretic peptide is incomplete, but these two new family members also act as vasodilators. Because of the rapid evolution of information about this peptide family, we reviewed the state of the art with respect to risk stratification and therapeutic ability.

METHODS

English-language papers were identified by a MEDLINE database search covering 1966 through 1997 and supplemented with bibliographic references and texts.

CONCLUSIONS

The natriuretic peptides are counterregulatory hormones with prognostically important levels. They are similarly upregulated in heart failure and counteract neurohormones that induce vasoconstriction and fluid retention. BNP may be the superior prognosticator for risk stratification after myocardial infarction and is independent of left ventricular ejection fraction. Lastly, experimental trials suggest that administration of exogenous natriuretic peptides or inhibitors of their catabolism to patients with ischemic heart disease may be clinically beneficial.

Hyperventilation as a specific test for diagnosis of coronary artery spasm

The hyperventilation test has been used as a clinical tool to induce coronary spasm. However, its diagnostic and prognostic values have not been fully elucidated. This study was designed to establish the sensitivity and specificity of the hyperventilation test and to clarify the characteristics of hyperventilation test-positive patients. We examined 206 patients in whom coronary spasm was documented by angiography (spasm group), and 183 patients without angina at rest in whom acetylcholine failed to induce spasm (nonspasm group). All patients performed vigorous hyperventilation for 6 minutes in the early morning. Of the spasm group patients, 127 showed positive responses to the test, including ST elevation (n = 111), ST depression (n = 15) and negative U wave (n = 1). None in the nonspasm group showed any ischemic electrocardiographic change. Thus, the sensitivity and specificity of this test for diagnosis of coronary spasm were 62% and 100%, respectively. In the spasm group, there were no significant differences between hyperventilation test-positive and test-negative patients in age, sex, the prevalence of hypertension, diabetes mellitus, obesity, smoking, and the number of diseased vessels. When clinical characteristics were compared, the proportions of the patients with high disease activity (> or =5 attacks a week), with severe arrhythmias (second- or third-degree atrioventricular block and/or ventricular tachycardia) during attacks, and with multivessel spasm were significantly higher in the hyperventilation test-positive patients than in the negative patients (69% vs 20%, p <0.0001; 31% vs 11%, p <0.005; and 58% vs 34%, p <0.01, respectively). These findings imply that hyperventilation is a highly specific test for the diagnosis of coronary artery spasm, and that hyperventilation test-positive patients are likely to have life-threatening arrhythmias during attacks and multivessel spasm.

Significance of raised natriuretic peptides after bicaval and standard cardiac transplantation

BACKGROUND

High levels of plasma atrial natriuretic peptide (ANP) and ventricular natriuretic peptide (BNP) have been identified after standard orthotopic cardiac transplantation. It has been postulated that the high ANP levels are a result of persistent secretion from the large residual atrial mass after transplantation. This study was undertaken to investigate the significance of raised ANP and BNP levels after standard and bicaval orthotopic heart transplantation.

METHODS

Plasma ANP and BNP levels were measured in 40 ambulatory, randomly selected cardiac transplant patients (group A, n = 20 had bicaval transplantation; group B, n = 20 had standard transplantation) and 10 healthy volunteers (group C). Cardiac transplant patients underwent endomyocardial biopsy and hemodynamic evaluation.

RESULTS

Plasma levels of ANP and BNP were elevated in the transplant recipients in comparison with normal volunteers (p = 0.0001 and p < 0.0001, respectively). There was no significant difference in the ANP levels between group A and group B, whereas BNP levels were higher in group B compared with group A (p = 0.03). Linear regression analysis showed that a faster heart rate, high mean pulmonary artery pressure, high pulmonary capillary wedge pressure, and high transpulmonary gradient were associated with higher levels of BNP (p < 0.05). Lower mean systemic pressure was associated with higher levels of ANP (p < 0.05).

CONCLUSIONS

High levels of ANP and BNP are synthesized and secreted by the transplanted denervated human heart regardless of the surgical technique. The level of BNP correlates with ventricular performance and afterload. The bicaval technique seems to be associated with better left ventricular and right ventricular diastolic performance.

Effects of brain (B-type) natriuretic peptide on coronary artery diameter and coronary hemodynamic variables in humans: comparison with effects on systemic hemodynamic variables

OBJECTIVES

This study attempted to clarify the effects of human brain (B-type) natriuretic peptide on coronary artery diameter and coronary vascular resistance in humans.

BACKGROUND

Brain natriuretic peptide induces vasodilation in systemic circulation by activating particulate guanylate cyclase of the vascular smooth muscle.

METHODS

In 13 patients with normal coronary arteries and left ventricular function, brain natriuretic peptide was infused at 0.5 microgram/kg body weight per min for 4 min into the left main coronary artery (six patients, Group A) or into the pulmonary artery (seven patients, Group B). Systemic hemodynamic variables and coronary sinus blood flow were measured before and after the infusion. The lumen diameter of the left coronary artery was quantitatively measured.

RESULTS

In both groups, brain natriuretic peptide significantly increased heart rate and decreased mean arterial pressure. Rate-pressure product remained unchanged in both groups. Brain natriuretic peptide decreased systemic vascular resistance index significantly in both groups (both p < 0.01 vs. baseline), and there was no difference in the effect between the groups. Brain natriuretic peptide decreased coronary vascular resistance in Group A (p < 0.01 vs. baseline) but did not affect coronary vascular resistance in Group B (p < 0.01 vs. Group A). The lumen diameters of the proximal and distal segments of the left coronary artery were increased significantly after brain natriuretic peptide in both groups. After infusion of brain natriuretic peptide, mean plasma level of brain natriuretic peptide in the coronary sinus increased from 36 to 130,411 pg/ml in Group A and from 64 to 12,329 pg/ml in Group B.

CONCLUSIONS

Brain natriuretic peptide shows a vasodilator effect on the coronary artery system in humans. However, the effect does not appear uniformly but is seen preferentially in the epicardial coronary artery. The sensitivity of the coronary resistance vessels to brain natriuretic peptide is low compared with that of the resistance vessels of the systemic circulation.