Atrial natriuretic peptide levels in congestive heart failure in man before and during converting enzyme inhibition

The effects of medications on circulating levels of cardiac natriuretic peptides

Circulating cardiac natriuretic peptide levels are being used increasingly in a range of clinical circumstances. Since it is evident that drugs used in the treatment of cardiovascular disorders can modulate natriuretic peptide levels, we here review the literature documenting these effects. Diuretics, blockers of the renin-angiotensin system, vasodilator agents, dopamine-like agonists, amiodarone, and perhaps allopurinol and statins suppress natriuretic peptide levels, most obviously in heart failure. Beta-blockers stimulate natriuretic peptide concentrations in hypertensive subjects, whereas in heart failure they have little effect or are stimulatory in the short term and inhibitory with sustained therapy. Digitalis compounds and aspirin tend to increase natriuretic peptide levels, and calcium channel blocking agents have varying effects depending on the individual drug and duration of administration. The effects of other drugs are less clear. Additional information is needed regarding the effects of medications along with dissection of the role of altered cardiac secretion versus changes in plasma clearance as explanation for drug-induced perturbations in natriuretic peptide concentrations. In the meantime, clinicians need to consider the known effects of medications when interpreting plasma levels of the cardiac natriuretic peptides.

Cardiac natriuretic hormones, neuro-hormones, thyroid hormones and cytokines in normal subjects and patients with heart failure

The derangement of neuro-endocrine control of circulation influences both disease evolution and response to treatment in patients with heart failure, but little data are available about the complex relationships between the degree of neuro-hormonal activation and clinical severity. We studied the relationships between cardiac natriuretic hormones (CNHs) and several neuro-hormones and immunological markers in a prospective cohort of 105 consecutive patients with cardiomyopathy (77 men and 28 women, mean age 66.7±12.4 years, range 33–89 years). We assayed the circulating levels of CNHs (atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP)), plasma renin activity (PRA), aldosterone, cortisol, adrenaline, noradrenaline, thyroid hormones and thyroid stimulating hormone (TSH), tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6). The concentrations of all CNHs and neuro-hormones were higher in patients with heart failure compared to normal subjects, except for free triiodothyronine (FT3), which was below normal values. ANP was positively related to NYHA class, IL-6, adrenaline, noradrenaline and cortisol, while negatively with ejection fraction and FT3. BNP was positively related to age, NYHA class, IL-6, TNF-α, adrenaline, noradrenaline and cortisol, while negatively with ejection fraction and FT3. A stepwise multiple linear regression indicated that plasma ANP depended only on ejection fraction, adrenaline and noradrenaline values, while for plasma BNP variation NYHA class contributed too. Our data confirm a progressive activation of hormonal and immunological systems in patients with heart failure. Furthermore, CNH circulating levels in heart failure are affected not only by cardiac function and disease severity, but also by activation of neuro-hormonal and stress-related cytokine systems, as well as by the thyroid hormones, even on usual medical treatment.

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

BACKGROUND

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

METHODS

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

CONTENT

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

CONCLUSIONS

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

Outpatient management of heart failure

With the increasing prevalence of heart failure, the greater spectrum of proven therapies, the broader spectrum of cardiac dysfunction qualifying for treatment and the recognition that heart failure is difficult to diagnose, the need for an indicator of both the diagnosis and the efficacy of treatment in this condition is clear. Plasma concentrations of the B-type natriuretic peptides are related to cardiac function and cardiovascular prognosis. They parallel hemodynamic indicators of cardiac dysfunction and may therefore act as indicators of the adequacy of therapy. In the one published trial of outpatient treatment of heart failure guided by plasma BNP, 69 patients (LVEF < 40%, NYHA II-IV) were randomised to treatment according to plasma peptide levels or a clinical score. The primary end point of total cardiovascular events was reduced in BNP-guided patients (19 versus 54 events) with p < 0.001 in a multivariate analysis. The natriuretic peptides and particularly plasma BNP and aminoterminal proBNP promised to provide an objective guide for optimising treatment in heart failure.

Cardiac hormones as diagnostic tools in heart failure

In patients with heart failure, plasma levels of atrial natriuretic peptide (ANP), B-type natriuretic peptide (BNP), and the N-terminal fragments of their prohormones (N-ANP and N-BNP) are elevated, because the cardiac hormonal system is activated by increased wall stretch due to increased volume and pressure overload. Patients suspected of having heart failure can be selected for further investigations on the basis of having an elevated plasma concentration of N-ANP, BNP, and N-BNP. High levels of cardiac hormones identify those at greatest risk for future serious cardiovascular events. Moreover, adjusting heart failure treatment to reduce plasma levels of N-BNP may improve outcome. Cardiac hormones are most useful clinically as a rule-out test. In acutely symptomatic patients, a very high negative predictive value is coupled with a relatively high positive predictive value. Measurement of cardiac hormones in patients with heart failure may reduce the need for hospitalizations and for more expensive investigations such as echocardiography. However, there have also been conflicting reports on the diagnostic value of cardiac hormones, they are not specific for any disease, and the magnitude of the effects of age and gender on BNP in the normal subgroup suggests that these parameters need to be considered when interpreting cardiac hormone levels.

BNP in hormone-guided treatment of heart failure

The pharmacotherapy of heart failure has become complex. Angiotensin-converting enzyme inhibitors (or angiotensin II receptor blockers), beta-blockers, spironolactone, diuretics and digoxin can be prescribed concurrently. Endothelin antagonists and combined inhibitors of converting enzyme and neutral endopeptidase are under investigation. Optimal dosing will become increasingly difficult to judge. Plasma brain natriuretic peptide (BNP) indicates the severity of left ventricular dysfunction. The C-terminal bioactive peptide and N-terminal BNP (N-BNP) circulate at concentrations related to cardiac status. We proposed that plasma levels of N-BNP would provide an index to guide drug treatment in established heart failure. Sixty-nine patients were randomized to treatment adjusted according to clinical criteria or plasma N-BNP. Hormone-guided therapy resulted in fewer clinical end points than did clinical management. This encourages further exploration of hormone guidance of anti-heart failure therapy, which could be extended to patients with preserved ejection fraction, in addition to those with established systolic dysfunction.

Brain natriuretic peptide-guided therapy for heart failure

The drug treatment of heart failure, once simple, has become complex. Apart from a loop diuretic and digoxin, most patients should now be receiving an angiotensin-converting enzyme inhibitor (or angiotensin II receptor blocker), a beta-blocker and spironolactone. Newer drugs, such as endothelin-receptor antagonists and combined blockers of converting-enzyme and neutral endopeptidase, might soon become available. When to introduce these drugs and what dose is optimal for any individual, are questions that currently vex clinicians. We proposed that plasma levels of the cardiac hormone brain natriuretic peptide (BNP, or better, its 1-76 amino-acid N-terminal fragment, N-BNP), would provide an objective index for guiding drug treatment in patients with established, stable cardiac failure. In a pilot study, 69 patients were randomized to drug treatment based on clinical criteria, or based on plasma levels of N-BNP. After a median follow-up of 9.6 months, those in the N-BNP group had fewer clinical end-points than those in the group managed by clinical criteria alone (19 vs 54; P= 0.02). These preliminary data encourage the concept that the increasingly complex pharmacotherapy for heart failure, both chronic (as in this trial) and acute, might best be guided by an objective measure such as plasma levels of BNP or N-BNP.

Effects of omapatrilat on systemic arterial function in patients with chronic heart failure

The mechanisms of action of omapatrilat, an agent that inhibits both neutral endopeptidase 24.11 and angiotensin-converting enzyme, on arterial function in patients with heart failure have not been previously reported. Forty-eight patients in New York Heart Association functional class II to III, left ventricular ejection fraction < or = 40%, and in sinus rhythm were randomized to a dose-ranging (2.5, 5, 10, 20, or 40 mg) study of omapatrilat for 12 weeks. Measurements were obtained at baseline and 12 weeks. Decreases in systolic (25.0 +/- 4.5 vs 2.8 +/- 5.0 mm Hg, p < 0.05) and mean arterial (13.9 +/- 3.0 vs 0.3 +/- 3.3 mm Hg, p < 0.05) pressure were seen after 12 weeks of therapy with higher doses. Ventricular-arterial coupling was improved with a dose-related decrease in augmentation index (-13.8 +/- 1.7% vs +6.1 +/- 2.1%, p < 0.01). There was no change in resting forearm blood flow between groups; however, maximum forearm vasodilator response during reactive hyperemia increased in the high-dose groups compared with the control group (+266 +/- 43% vs - 14 +/- 92%, p < 0.05). Omapatrilat induced an increase in postdose plasma atrial natriuretic peptide levels (30 +/- 11 vs -2 +/- 7 pmol/L, p < 0.01) in high-dose groups consistent with endopeptidase 24.11 inhibition. Omapatrilat shows beneficial changes in ventricular-vascular coupling and arterial function in heart failure.

Beneficial renal and hemodynamic effects of omapatrilat in mild and severe heart failure

Omapatrilat is a member of the new drug class of vasopeptidase inhibitors that may offer benefit in the treatment of heart failure (HF) through simultaneous inhibition of angiotensin-converting enzyme and neutral endopeptidase. We examined the effects of omapatrilat in a placebo-controlled crossover study using a pacing model of HF. Seven sheep were paced sequentially at 180 bpm (mild HF) and then 225 bpm (severe HF) for 7 days each. Omapatrilat (0.005 mg/kg) or vehicle was administered by intravenous bolus on days 4 to 7 of each paced period. Omapatrilat lowered mean arterial and left atrial pressure and increased cardiac output acutely and chronically in both mild and severe HF (P<0.01 for all). Plasma atrial and brain natriuretic peptide and cGMP levels were stable acutely (P=NS), while brain natriuretic peptide increased after repeated dosing in severe HF (P<0.05). Plasma renin activity rose, whereas angiotensin II and aldosterone levels fell after acute and repeated dosing in both states (P<0.01 for all). Omapatrilat increased urinary sodium excretion by day 7 in both mild and severe HF (P<0.05). Effective renal plasma flow and glomerular filtration rate increased or were stable after omapatrilat in mild and severe HF after both acute and repeated dosing. Omapatrilat exhibited pronounced acute and sustained beneficial hemodynamic and renal effects in both mild and severe heart failure.

The clinical, cardiac, renal, arterial and neurohormonal effects of omapatrilat, a vasopeptidase inhibitor, in patients with chronic heart failure

OBJECTIVES

We sought to examine the effects of long-term vasopeptidase inhibition in patients with heart failure.

BACKGROUND

The long-term effects of omapatrilat, an agent that inhibits both neutral endopeptidase and angiotensin-converting enzyme, on clinical status, neurohormonal indexes and left ventricular function in patients with chronic heart failure (CHF) have not been previously documented.

METHODS

Forty-eight patients in New York Heart Association functional class II or III, with left ventricular ejection fraction (LVEF)< or =40% and in sinus rhythm were randomized to a dose-ranging pilot study of omapatrilat for 12 weeks. Measurements were performed at baseline and 12 weeks.

RESULTS

There was an improvement in functional status, as reported by the patient (p<0.001) and physician (p<0.001) at 12 weeks. Dose-dependent improvements in LVEF (p<0.001) and LV end-systolic wall stress (sigma) (p<0.05) were seen, together with a reduction in systolic blood pressure (p<0.05). There was evidence of a natriuretic effect (p<0.001), and total blood volume decreased (p<0.05). Omapatrilat induced an increase in postdose plasma atrial natriuretic peptide levels (p<0.01) in the high dose groups, with a reduction in predose plasma brain natriuretic peptide (p<0.001) and epinephrine (p<0.01) levels after 12 weeks of therapy. Omapatrilat was well tolerated.

CONCLUSIONS

The sustained hemodynamic, neurohumoral and renal effects of omapatrilat, together with improved functional status, suggest that vasopeptidase inhibition has potential as a new therapeutic modality for the treatment of CHF.

The circulating renin-angiotensin system during treatment with metoprolol or captopril in patients with heart failure due to non-ischaemic dilated cardiomyopathy

OBJECTIVE

To investigate the effects of beta-blocker (metoprolol) or angiotensin-converting enzyme inhibitor (captopril) treatment on neurohormonal function in a randomized prospective study on patients with heart failure due to dilated cardiomyopathy.

PATIENTS

Fifty-four patients (42 men and 12 women, mean age 50 years) were studied. There were three patients in NYHA (New York Heart Association) functional class I, 32 patients in class II and 19 patients in class III.

METHODS

Measurements of plasma renin activity (PRA). plasma angiotensin II (A II) concentration and plasma atrial natriuretic peptide (ANP) concentration were made at rest and also in a subgroup (n = 32) during exercise. The urinary excretion of aldosterone was also determined. Investigations were performed at baseline, and after 3 and 6 months. Therapy was then stopped and the patients were re-investigated 1 month thereafter.

RESULTS

The mean level of PRA was normal at baseline, reduced during therapy with metoprolol, and increased during therapy with captopril. The mean plasma concentration of A II was reduced during exercise and there was a trend towards a reduction even at rest in the metoprolol group, but not in the captopril group. The urinary excretion of aldosterone decreased in both groups. The mean plasma concentration of ANP was elevated at baseline and declined during exercise in the metoprolol group.

CONCLUSION

In patients with dilated cardiomyopathy and only a partly activated renin-angiotensin system, both metoprolol and captopril reduced urinary excretion of aldosterone. Furthermore, metoprolol suppressed the exercise-induced increase in ANP, suggesting a favourable effect on ventricular performance.

Improvement of exercise capacity of rats with chronic heart failure by long-term treatment with trandolapril

1. The effects of long-term treatment with trandolapril, an angiotensin I-converting enzyme inhibitor, on exercise capacity of rats with chronic heart failure (CHF) following coronary artery ligation were examined. CHF was developed by 8 weeks after the coronary artery ligation. 2. The running time of rats with CHF in the treadmill test was shortened to approximately 65% of that of sham-operated rats (16.3+/-1.2 vs. 25.1+/-1.6 min, n = 7; P<0.05). ATP, creatine phosphate (CP), and lactate contents of the gracilis muscle of rats with CHF were similar to those of sham-operated rats before running. After running, ATP and CP were decreased and lactate was increased in both rats with CHF and sham-operated rats. There were no significant differences in the levels of energy metabolites between rats with CHF and sham-operated rats. The rates of decrease in ATP and CP and rate of increase in lactate in the gracilis muscle of rats with CHF during exercise were greater than those of sham operated rats (2.5, 2.0 and 1.5 fold high, respectively), suggesting wastage of energy during exercise in the animals with CHF. 3. Myofibrillar Ca2+ -stimulated ATPase (Ca-ATPase) activity of skeletal muscle of rats with CHF was increased over that of the sham-operated control (62.03+/-1.88 vs. 52.34+/-1.19 micromol Pi mg(-1) protein h(-1) n = 7; P<0.05). The compositions of myosin heavy chain (MHC) isoforms of gracilis muscle were altered by CHF; decreases in MHC types I and IIb and an increase in MHC type IIa were found (P<0.05). 4. Rats with CHF were treated with 1 mg kg(-1) day(-1) trandolapril from the 2nd to 8th week after surgery. Treatment with trandolapril prolonged the running time, reversed the rates of decrease in ATP and CP and the rate of increase in lactate, and restored the Ca-ATPase activity (51.11+/-0.56 micromol Pi mg(-1) protein h(-1), n = 7; P<0.05) and composition ratio of MHC isoforms in the gracilis muscle. 5. The results suggest that long-term trandolapril treatment of rats with CHF may restore their ability to utilize energy without wastage and thus improve exercise capacity.

Effects of long-term treatment with trandolapril on sarcoplasmic reticulum function of cardiac muscle in rats with chronic heart failure following myocardial infarction

1 Calcium transport activity of isolated cardiac sarcoplasmic reticulum (SR) including Ca2+ uptake and release is decreased in animals with chronic heart failure (CHF) following myocardial infarction. The present study was undertaken to determine whether an angiotensin converting enzyme (ACE) inhibitor, trandolapril, improves cardiac sarcoplasmic reticular function in animals with CHF following myocardial infarction. 2 CHF was induced by left coronary artery ligation in rats, which resulted in an infarction of approximately 45% of the left ventricle. Aortic flow and cardiac output index were decreased, and left ventricular end-diastolic pressure was increased 8 weeks after the operation, suggesting the development of CHF. 3 The developed force transients of cardiac skinned fibres of the rats with CHF were decreased when the skinned fibre was preloaded for 0.25-1 min with 10(-5) M Ca2+ (48-88%) and when preloaded with 10(-6) M Ca2+ and then exposed to 0.1-1 mM caffeine (45-93%). 4 The [3H]-ryanodine-binding activity in SR-enriched fractions was reduced by 23% in the CHF group. These results suggest that the amount of Ca2+ released from SR is decreased due to a reduced rate of SR Ca2+ uptake and a downregulation of the SR Ca2+-release channel. 5 Rats were treated orally with 3 mg kg(-1) day(-1) trandolapril from the 2nd to the 8th week after the coronary artery ligation. Treatment with trandolapril attenuated the reduction in aortic flow and cardiac output index and the increase in left ventricular end-diastolic pressure, and improved the developed force transients of the skinned fibre of the animal with CHF without causing a reduction of infarct size. Treatment with trandolapril also attenuated the reduction in ryanodine receptor density in the viable left ventricle of the rat with CHF. 6 It is concluded that long-term treatment with trandolapril attenuates cardiac SR dysfunction in rats with CHF and that the mechanism underlying this effect is, at least in part, attributed to prevention of downregulation of Ca2+ release channel.

Short term effects of acute inhibition of the angiotensin-converting enzyme on the renin-angiotensin system and plasma atrial natriuretic peptide in healthy dogs fed a low-sodium diet versus a normal-sodium diet

The purpose of the present study was to quantify some of the short term responses of the renin-angiotensin system (RAS) to a recommended dosage of the angiotensin-converting enzyme inhibitor enalapril in clinically healthy dogs fed a normal-sodium and a low-sodium diet. A single dose of enalapril (0.5 mg/kg PO) was given to eight clinically healthy male Beagle dogs after a period where the dogs were fed a normal-sodium diet and low-sodium diet, respectively. Serum angiotensin-converting enzyme activity (ACE), plasma renin activity (PRA), plasma aldosterone concentration (PAC), and plasma atrial natriuretic peptide (ANP) concentration were measured during the following twenty-four hour period. The data indicate that enalapril induced a potent blockade of the renin-angiotensin system (RAS) for at least twenty-four hour. Specifically, enalapril during low-sodium diet elicited an exaggerated increase in PRA and a diminished decrease in ACE and ANP when compared to the results of the drug during normal-sodium diet. Long term controlled studies of enalapril in dogs with congestive heart failure (CHF) are warranted in order to determine the duration of action and optimal dose of enalapril.

Atrial natriuretic peptide in severe heart failure: response to controlled changes in atrial pressures during intravenous nitroglycerin therapy

Atrial natriuretic peptide (ANP) levels were measured in 17 patients with severe congestive heart failure (New York Heart Association functional class IV), and the response of the peptide was studied during changes in cardiac filling pressures induced by a 24-hour infusion of nitroglycerin. In the control state plasma ANP levels (687 +/- 551 pg/ml) were 10-fold normal. During the administration of nitroglycerin, natriuretic peptide levels decreased (p less than 0.005) with changes matching very closely the decreases in pulmonary arterial wedge and right atrial pressures, a 1% mean decrease in the peptide level for every 1.5 to 2% mean change in atrial filling pressures. In patients with hemodynamic tolerance to constant-dose nitroglycerin infusion, the resulting increase in atrial pressures was accompanied by an appropriate secondary increase in the plasma ANP level. During the 24-hour study period there was a direct linear relationship between both wedge (r = 0.93, p = 0.007) and right atrial (r = 0.93, p = 0.008) pressures and the plasma ANP level, with a zero-pressure ANP intercept near normal (69 pg/ml for wedge, 174 pg/ml for right atrial pressure). The findings were no different in a subgroup of five patients receiving simultaneous treatment with captopril, except that plasma renin activity was higher and the aldosterone level lower than in the control group by a factor of approximately 2.5. The close relationship and tracking of atrial pressure and natriuretic peptide curves suggested that the sensitivity of the atrial stretch response to changes in atrial filling pressures was maintained in severe congestive heart failure.

Increased plasma level of substance P in patients with severe congestive heart failure treated with ACE inhibitors

The effects of angiotensin-converting-enzyme (ACE) inhibitors on circulatory regulating mechanisms in congestive heart failure (CHF) were studied by comparison of plasma levels of catecholamines, neuropeptide Y-like immunoreactivity (NPY-LI), substance P (SP-LI), calcitonin gene-related peptide (CGRP-LI), vasopressin (ADH-LI), atrial natriuretic peptide (ANP-LI) and renin activity (PRA) in patients with severe CHF (NYHA III-IV) with (n = 15) or without (n = 17) ACE inhibitors in addition to digoxin and diuretic therapy. Data were also compared with those for healthy subjects (n = 31) and patients with moderate CHF (NYHA I-II). Catecholamines and NPY-LI were increased to the same extent in both groups with severe CHF. CGRP-LI showed no changes relative to controls in any of the patient groups, and was not affected by ACE inhibitors. The SP-LI level was significantly increased in all patient groups. Patients with severe CHF on ACE inhibition had a SP-LI level of 4.05 +/- 0.79 pmol l-1, compared to a concentration of 2.28 +/- 0.30 pmol l-1 (P less than 0.05) in the patient group with a comparable degree of CHF but without ACE inhibition. In the latter group, an inverse relationship appeared between the SP-LI and the serum sodium levels (r = -0.68, P less than 0.05). The patients with severe CHF who received ACE inhibitors had significantly lower ADH-LI levels than the patients with a comparable degree of CHF who were not treated with ACE inhibitors, while the ANP-LI levels was increased to a similar extent in both groups.