Renin relationships in congestive cardiac failure, treated and untreated

Acid-base and electrolyte abnormalities in heart failure: pathophysiology and implications

Electrolyte and acid–base abnormalities are a frequent and potentially dangerous complication in subjects with congestive heart failure. This may be due either to the pathophysiological alterations present in the heart failure state leading to neurohumoral activation (stimulation of the renin–angiotensin–aldosterone system, sympathoadrenergic stimulation), or to the adverse events of therapy with diuretics, cardiac glycosides, and ACE inhibitors. Subjects with heart failure may show hyponatremia, magnesium, and potassium deficiencies; the latter two play a pivotal role in the development of cardiac arrhythmias. The early identification of these alterations and the knowledge of the pathophysiological mechanisms are very useful for the management of these patients.

The critical link of hypervolemia and hyponatremia in heart failure and the potential role of arginine vasopressin antagonists

BACKGROUND

Hypervolemia and hyponatremia resulting from activation of the neurohormonal system and impairment of renal function are prominent features of decompensated heart failure. Both conditions share many pathophysiologic and prognostic features and each has been associated with increased morbidity and mortality. When both conditions coexist, therapeutic options are limited.

METHODS AND RESULTS

This review presents a concise digest of the pathophysiology, clinical significance, and pharmacological therapy of hyponatremia complicating heart failure with a special emphasis on vasopressin antagonists and their aquaretic effects in the absence of neurohormonal activation along with their ability to correct hyponatremia.

CONCLUSIONS

Hypervolemia and hyponatremia share many pathophysiologic and prognostic features in heart failure. Vasopressin antagonists provide a viable option for their management and a potentially unique role when both conditions coexists.

Activation of the neuroendocrine response in heart failure: adaptive or maladaptive process?

Congestive heart failure is a clinical syndrome in which the capacity of the heart to maintain cardiac output is impaired. As a consequence, blood pressure is threatened and endocrine and paracrine mechanisms are activated to preserve circulatory homeostasis and to maintain blood pressure. At terminal stages, a complex multiorgan syndrome develops with severe pump failure, intense systemic vasoconstriction, and avid water and sodium retention. Increasing evidence points to humoral circulating or locally synthesized substances as one of the causes of the terminal consequences of heart failure. Therefore, the hypothesis that the syndrome of heart failure is, at least in part, a humoral disease has developed and is obtaining scientific credibility. Consequently, the neuroendocrine response to heart failure is no longer viewed as a compensatory beneficial mechanism. Instead, we have learned through the years that pharmacological treatment aimed at reducing the effect of the neuroendocrine response is indeed clinically and prognostically advantageous for the patient.

Dose-ranging study of the angiotensin II receptor antagonist irbesartan (SR 47436/BMS-186295) on blood pressure and neurohormonal effects in salt-deplete men

We characterised the blood pressure (BP) and hormonal responses to the oral angiotensin II (Ang II) receptor antagonist irbesartan (SR47436/BMS-186295) or placebo in normal men with an activated renin-angiotensin system (RAS) during salt depletion. We also evaluated safety and tolerability. Twelve healthy, normotensive male volunteers followed a standardised salt-depletion regimen for 3 days before each study day. Six different single oral doses of irbesartan (1, 5, 10, 25, 50, and 100 mg) were administered double-blind in a three-panel, dose escalation with placebo randomised in each panel. Supine and erect BP and heart rate (HR), serum and urinary electrolytes: plasma renin activity (PRA), and Ang II were measured at intervals. Urinary electrolytes were measured for the 24-h period before dosing (to confirm salt depletion) and for 24 h afterward. No drug-related side effects were noted. There was a dose-related decrease in supine and erect systolic and diastolic BP (SBP, DBP) with irbesartan from 10 mg and beyond, with no change in HR. Supine mean arterial pressure (MAP) decreased by 18.8 mm Hg. There was a dose-related reactive increase in PRA (to 35 ng/ml/h) and Ang II (to 450 pg/ml) with irbesartan. Irbesartan is an orally active AT1 receptor antagonist. In salt-deplete normal men, it has a dose-related haemodynamic, hormonal, and electrolyte profile characteristic of AT1 antagonists. The dose range studied did not show a plateau or maximum effect.

Prediction of renal impairment in elderly patients with congestive heart failure treated with captopril

This study assessed the usefulness of the oral captopril test in the prediction of renal impairment among elderly patients with congestive heart failure (CHF). Forty-seven patients aged > or = 65 years with CHF (EF < 40%) participated in a prospective nonrandomized series. Blood samples for plasma renin activity (PRA) were drawn before and 60 minutes after 50 mg of oral captopril. Twenty-four hours later, captopril was administered (up to 75 mg/day over a 4 day period), and renal laboratory and clinical assessment were performed at baseline and for a 9 day period. In 7 of 47 patients (14.9%), deterioration of renal function was observed. During the captopril test, the PRA increased significantly after 1 hour in almost all patients and the mean blood pressure decreased from 99.2 +/- 14.6 mmHg to 92.2 +/- 13.7 mmHg (p < 0.001). All patients whose baseline PRA level was < 1.9 ng/ml/hr and whose stimulated PRA was < 3.2 ng/ml/hr maintained a stable renal function throughout the study period. Significant statistical correlation (p < 0.05) was found between the initial PRA, the changes in PRA or mean blood pressure during the captopril test, and the change in plasma creatinine and creatinine clearance in the entire group, and was even more evident in a subgroup of patients with an ejection fraction > or = 30%. All these correlations were not statistically significant in the patients with an ejection fraction < 30%. It is thus concluded that measurement of pretreatment PRA levels might be a useful laboratory tool for predicting the renal safety of captopril use in patients with CHF whose EF > or = 30%.

Neuroendocrine changes in chronic cardiac failure

Numerous hormonal and neuroendocrine changes have been described in patients with chronic cardiac failure. These affect the balance of vasodilator and vasoconstrictor factors in favour of the latter, to the detriment of the circulation. Whether this is a reaction to central cardiac (haemodynamic) abnormalities, or is an integral part of the syndrome of heart failure, remains to be determined. Catecholamine levels are increased, especially in severe heart failure, and contribute to the vasoconstriction and probably also to lethal ventricular arrhythmias. The renin-angiotensin-aldosterone system (RAAS) is also activated, causing fluid retention and further vasoconstriction. In the earlier stages, some of this increase may be iatrogenic due to the use of loop diuretics or inhibitors of angiotensin converting enzyme, but there is evidence for independent RAAS activation in more severe grades of heart failure. The role of vasoconstrictor peptides such as neuropeptide Y and endothelin is briefly considered. Counterbalancing these are vasodilator peptides, in particular atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP). The possibility of therapeutic interventions to increase circulating natriuretic hormone levels is discussed.

Electrolyte disturbances in chronic heart failure: metabolic and clinical aspects

The pathophysiology of congestive heart failure (CHF) includes conditions (e.g., activation of the renin-angiotensin-aldosterone system) which, when combined with CHF therapies, make patients afflicted with this syndrome quite susceptible to electrolyte disturbances. The most commonly encountered are hyponatremia, hypokalemia, and hypomagnesemia. These derangements are of vast clinical importance; their development not only represents an immediate threat to the CHF patient (e.g., dysrhythmias secondary to hypokalemia), but are also indicative of underlying pathophysiologic events, an unfavorable clinical course, and occasionally an adverse therapeutic response. The optimal care of CHF patient includes the recognition and management of these electrolyte disturbances.

Neurohormonal mechanisms and the role of angiotensin-converting enzyme (ACE) inhibitors in heart failure

Clinical evidence accumulated over the past decade suggests that neurohormonal mechanisms significantly influence the pathogenesis and eventual outcome of congestive heart failure (CHF). Pharmacologic modulation of this neuroendocrine activity can, consequently, be expected to improve patient prognosis. Results of several recent clinical trials--the Studies of Left Ventricular Dysfunction (SOLVD), the second Veterans Administration Cooperative Vasodilator Heart Failure Trial (VH eFT-II), and the Cooperative North Scandinavian Enalapril Survival Study (CONSENSUS)--provide substantial evidence that addition of the angiotensin-converting enzyme (ACE) inhibitor enalapril to conventional therapeutic regimens can significantly reduce mortality and improve prognosis in patients with all grades of heart failure. Moreover, data from all three trials confirm the involvement of neurohormonal systems in the development and progression of CHF and suggest that the beneficial effects of enalapril in heart failure may in part be due to the suppression of this neurohormonal activity. It is now apparent that some form of neurohormonal activation is present early in the course of the disease before the emergence of overt heart failure symptoms. On the basis of such findings, it would seem that early introduction of therapy targeted at neurohormonal influences may well become a central component of any future CHF treatment program.

Responses to low dose intravenous perindoprilat infusion in salt deplete/salt replete normotensive volunteers

1. Intravenous ACE inhibitor therapy appears to have a role in the treatment of acute heart failure and early after myocardial infarction. Practical experience with intravenous administration with activation of renin is limited. We report responses to perindoprilat (Pt, 0.67 mg) or placebo (P) infused over 4 h in normotensive male volunteers (n = 12, 19-28 years, 53-77 kg) with double-blind, placebo controlled salt depletion (SD) or salt repletion (SR) as a model of the activated renin system. 2. Salt depletion caused no significant fall in serum sodium (P, 139.4 +/- 2.4; Pt, 138.3 +/- 1.9) compared with salt replete preparation (P, 139.9 +/- 1.2; Pt, 139.7 +/- 0.9) but elevation of plasma renin activity 2-3-fold. Pretreatment baseline systolic blood pressure following salt depletion (P, 121 +/- 9.3/71 +/- 7.9; Pt, 121.5 +/- 9.6/69 +/- 8.1) was higher than following salt replete preparation (P, 114 +/- 9.5/61 +/- 7.2; Pt, 116.9 +/- 6.9/67 +/- 7.2). 3. Baseline corrected supine SBP fell significantly and to a similar extent following active treatment regardless of activation of the renin system (SD, -14.6 +/- 9.5/-9.4 +/- 6.4; SR, -12 +/- 14/-10.1 +/- 6.6) compared with placebo (SD, -6.1 +/- 6/-3.7 +/- 5.6; SR, -4.7 +/- 10/-1.3 +/- 6.5). Heart rate was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

The problem of defining heart failure

A succession of theories arising from last century has attempted to explain why patients with damaged hearts develop peripheral edema. Opposed to the original simple concepts of backward failure, a number of theories of forward failure have been proposed, the cardiac output being considered inadequate for capillary permeability, renal function, or the metabolic needs of the body. Any theory needs to take account of the neuroendocrine stimulation now known to occur under these conditions. This article presents evidence for the belief that the condition arises when the cardiac output becomes insufficient to maintain the arterial blood pressure without the support of excessive neuroendocrine activity. This explains why the edematous state may be evoked in patients who have a severe reduction in peripheral resistance as well as in those with a reduced cardiac output. While the clinical concept of cardiac failure arose from the consideration of the formation of edema in patients with cardiac disease, the term has also come to be used by laboratory investigators studying the immediate effects of reducing the strength of ventricular contraction. The application of the same name to two different conditions has led to confusion, and this review stresses the importance of definition of terms.

Relation of neurohumoral activation to clinical variables and degree of ventricular dysfunction: a report from the Registry of Studies of Left Ventricular Dysfunction. SOLVD Investigators

OBJECTIVES

This study examined the relation between neurohumoral activation and severity of left ventricular dysfunction and congestive heart failure in a broad group of patients with depressed left ventricular function who were not recruited on the basis of eligibility for a therapeutic trial.

BACKGROUND

Previous studies have established the presence of neurohumoral activation in patients with severe congestive heart failure. It is not known whether the activation of these neurohumoral mechanisms is related to an impairment in left ventricular function.

METHODS

From the 6,273 patients recruited into the Studies of Left Ventricular Dysfunction Registry (SOLVD), a subgroup of 859 patients were randomly selected, and their plasma norepinephrine, plasma renin activity, arginine vasopressin and atrial natriuretic peptide levels were correlated with clinical findings, New York Heart Association functional class, left ventricular ejection fraction and drug use.

RESULTS

There was a weak but significant correlation between ejection fraction and an increase in plasma norepinephrine (rho = -0.18, p < 0.0001), plasma renin activity (rho = -0.24, p < 0.0001) and arginine vasopressin (rho = -0.12, p < 0.003). The only exception was atrial natriuretic peptide, which showed the best correlation to ejection fraction (rho = -0.37, p < 0.0001). Deterioration in functional class was associated more with increases in atrial natriuretic peptide (p = 0.0003) and plasma renin activity (p = 0.0003) and less with an increase in plasma norepinephrine. Of the clinical variables, elevated jugular venous pressure and third heart sound (S3) gallop were significantly associated with increased levels of plasma norepinephrine, plasma renin activity and atrial natriuretic peptide. We then compared the relation of neurohormones with clinical signs, functional status, ejection fraction and drug therapy and controlled for mutual interactive effects. After adjustment, a decrease in ejection fraction was still significantly related to an increase in plasma norepinephrine, plasma renin activity and atrial natriuretic peptide. In contrast, only a difference between functional classes I and III/IV was associated with an increase in plasma renin activity and atrial natriuretic peptide levels.

CONCLUSIONS

Neurohumoral activation in patients with heart failure is related to severity of left ventricular functional depression, and this relation is independent of functional class or concomitant drug therapy.

Comparative neurohormonal responses in patients with preserved and impaired left ventricular ejection fraction: results of the Studies of Left Ventricular Dysfunction (SOLVD) Registry. The SOLVD Investigators

OBJECTIVES

The aim of this study was to determine the differences in neurohumoral responses between patients with pulmonary congestion with and without impaired left ventricular ejection fraction.

BACKGROUND

Previous studies have established the presence of neurohumoral activation in patients with congestive heart failure. It is not known whether the activation of these neurohumoral mechanisms is related to the impairment in systolic contractility.

METHODS

The 898 patients recruited into the Studies of Left Ventricular Dysfunction (SOLVD) Registry substudy were examined to identify those patients with pulmonary congestion on chest X-ray film who had either impaired (< or = 45%, group I) or preserved (> 45%, group II) left ventricular ejection fraction. Plasma norepinephrine, plasma renin activity, arginine vasopressin and atrial natriuretic peptide levels were measured in these two groups of patients and compared with values in matched control subjects.

RESULTS

Distribution of the New York Heart Association symptom classification was the same in the two groups of patients. Compared with control subjects, patients in group II with pulmonary congestion and preserved ejection fraction had no activation of the neurohumoral mechanisms, except for a small but statistically significant increase in arginine vasopressin and plasma renin activity. Compared with patients in group II, those in group I with pulmonary congestion and impaired ejection fraction had significant increases in plasma norepinephrine (p < 0.002), plasma renin activity (p < 0.02) and atrial natriuretic peptide levels (p < 0.0007). When we controlled for baseline differences between groups I and II, the between-group differences in plasma norepinephrine (p < 0.02) and atrial natriuretic peptide (p < 0.002) remained significant. However, plasma renin activity was not significantly different between groups I and II. When the effects of diuretic agents and angiotensin-converting enzyme inhibitors were adjusted, patients with lower ejection fraction were found to have significantly higher plasma norepinephrine and atrial natriuretic peptide levels.

CONCLUSIONS

The results point to the importance of the decrease in left ventricular ejection fraction as one of the mechanisms for activation of neurohormones in patients with heart failure.

The treatment of heart failure--what next?

1. Despite demonstrable benefits in terms of symptomatic relief and improvement in prognosis, even the best treatments of heart failure currently available fall short of being ideal. We review the basis for newer approaches to the treatment of heart failure and discuss some of the agents which capitalize on current understanding of the underlying patho-physiology. 2. Several drugs, old and new, are presently being investigated by major clinical trials. We also consider some of the difficulties related to the design and conduct of such trials and suggest how drugs might be better assessed in the future.

Renal effects of xamoterol in patients with moderate heart failure

The acute renal effects of xamoterol, a partial beta 1-agonist, were studied in 12 patients with congestive heart failure (NYHA II-III) in stable condition on diuretic therapy for at least 6 weeks. Each patient was given a single intravenous infusion of xamoterol (0.2 mg/kg) or placebo in random order 2 weeks apart. Using constant infusion and lithium clearance techniques, clearance and excretion measurements were made in the supine position at 30- to 60-min intervals before, during, and up to 6 hours after infusion. Blood pressure, heart rate, renal plasma flow, glomerular filtration rate, and urinary flow rate remained unchanged, but xamoterol lowered sodium excretion by 30% (p < 0.05). The decrease started 120 minutes after infusion. Proximal reabsorption of sodium increased after xamoterol infusion, whereas plasma values of aldosterone and angiotensin II were unaffected. It is concluded that the acute renal effects of xamoterol imply an impaired sodium excretion determined by the tubular actions of the drug. The present results suggest that xamoterol may aggravate one of the important abnormalities intrinsic to the pathology of congestive heart failure. These findings are in contrast to the beneficial effects of xamoterol demonstrated in many clinical trials where xamoterol was given orally for a longer period.

Effect of inhibition of endopeptidase 24.11 on responses to angiotensin II in human volunteers

The effects of endopeptidase 24.11 inhibition on angiotensin-induced changes in plasma angiotensin II, aldosterone, and atrial natriuretic factor concentrations and blood pressure were assessed in normal volunteers. Two groups, each consisting of eight normal volunteers, received stepwise infusions of angiotensin II (2, 4, and 8 ng/kg per minute) on day 5 of dose administration with 25 mg every 12 hours (group 1) or 100 mg every 12 hours (group 2) of an oral inhibitor of endopeptidase 24.11 (UK 79300, candoxatril) or placebo in balanced randomized, double-blind, placebo-controlled crossover studies. Both doses of candoxatril significantly enhanced achieved plasma angiotensin II concentrations during infusions (group 1, p < 0.001; group 2, p < 0.01; overall treatment effect for combined data, p < 0.001). This effect was most pronounced at the highest dose of angiotensin II (treatment-time interaction, p < 0.0001 for combined data) and tended to be more marked with the higher dose of candoxatril (treatment-group interaction, p = 0.08). The pressor response to angiotensin II was clearly enhanced by the lower dose of candoxatril; peak systolic and diastolic pressures exceeded placebo values by approximately 10 mm Hg (p < 0.001 and p < 0.05 for systolic and diastolic pressures, respectively). This effect of candoxatril was absent in group 2, which (unlike group 1) had exhibited a modest natriuretic response (sustained cumulative negative sodium balance, -70 +/- 21 mmol; p < 0.01) to the higher dose of inhibitor. Baseline plasma aldosterone concentrations and the incremental aldosterone response to angiotensin II infusions were not significantly altered by low-dose (group 1) candoxatril.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin-converting enzyme inhibitors, left ventricular dysfunction, and early heart failure

A study was undertaken to examine the effects of the angiotensin-converting enzyme inhibitor lisinopril on exercise performance in 18 patients with major impairment of left ventricular systolic function. The study was a randomized, double-blind, crossover design, and patients received treatment with either once-daily lisinopril (2.5-10 mg) or placebo for a period of 6 weeks. A total of 15 patients completed the study. Compared with placebo, lisinopril had no significant effect on supine or standing blood pressure or heart rate. Although lisinopril had no effect on exercise duration during a low-intensity exercise protocol, in patients undergoing a high-intensity exercise protocol, there was a trend toward improved exercise time and peak oxygen consumption improved significantly. In addition, treatment with lisinopril resulted in an increase in renal blood flow and a reduction in glomerular filtration rate. Moreover, administration of once-daily lisinopril 10 mg resulted in a decrease in plasma concentrations of angiotensin II, aldosterone, and atrial natriuretic peptide, and an increase in plasma concentrations of active renin.

Vasodilators. A re-evaluation of their role in heart failure

Over the past 25 years, the concept of circulation in heart failure has evolved from that of a simple circuit with a weak pump and high pressures to a complex integrated system of cellular modification, cardiac compensation and systemic neurohumoral responses. The original model of cardiac afterload as the systemic vascular resistance has been refined to reflect the interdependence of preload and afterload and the central role of atrioventricular valve regurgitation. It is becoming increasingly apparent that the impact of vasodilator therapy far exceeds the direct haemodynamic effects on preload and afterload, and depends on the mechanism by which vasodilation is achieved, with increasing emphasis on those agents which oppose neurohumoral activation. The potential goals of therapy have broadened to include not only haemodynamic stabilisation through tailored therapy for patients referred with advanced heart failure, but also the prevention of disease progression for patients with asymptomatic ventricular dilation. As the different profiles of heart failure have come to be recognised, the purpose and design of vasodilator treatment must now be considered individually for each patient.

Predictors of prognosis in severe chronic heart failure

A total of 127 patients with chronic heart failure referred to our exercise laboratory were studied retrospectively to identify parameters predictive of prognosis. Patients were followed for a mean of 14.6 months. The group as a whole had severe ventricular dysfunction with a median ejection fraction of 17% and a median peak rate of oxygen consumption of 13.7 ml/kg/min. During the follow-up period 23 patients (18%) died and 18 (14%) underwent cardiac transplantation. The effect of the following variables on outcome (death or transplantation) were examined: age, cause of heart failure, cardiothoracic ratio on chest radiography, left ventricular end-systolic dimension on echocardiography, left ventricular ejection fraction on radionuclide ventriculography, mean dose of diuretic, plasma sodium and urea concentrations, and peak oxygen consumption during exercise. Although all variables except cause of heart failure affected outcome on univariate analysis, multivariate analysis identified three variables that were statistically significant and independent predictors of outcome. In order of importance these were plasma sodium level, left ventricular ejection fraction and peak oxygen consumption. Even in this group of patients with severe heart failure, these variables were predictive of outcome.

Neuroendocrine activity in untreated heart failure

Neuroendocrine activity was studied in 60 consecutive untreated patients with dyspnoea and a clinical suspicion of heart failure. On the basis of the so-called Boston clinical criteria the diagnosis of heart failure was regarded as unlikely in 26 patients, possible in 15 patients, and definite in 19 patients. These groups were studied before any drug treatment was started and were compared with a control group of 69 healthy individuals. Plasma atrial natriuretic peptide concentration was clearly raised in patients with definite heart failure and slightly raised in patients with possible heart failure. Plasma adrenaline concentration was somewhat raised in patients with definite or possible heart failure, whereas plasma noradrenaline concentration was raised only in patients with definite heart failure. Plasma renin activity was not increased in any of the patient groups and plasma aldosterone concentration was slightly increased only in patients with definite heart failure. In the total patient series there were significant correlations between plasma atrial natriuretic peptide concentration and markers of the severity of left ventricular dysfunction. There was some evidence of neuroendocrine activation in untreated heart failure: plasma concentrations of atrial natriuretic peptide and catecholamines were increased but the renin-angiotensin-aldosterone system showed little or no activation.

Which vasodilator drug in patients with chronic heart failure? A randomised comparison of captopril and hydralazine

1. Fifty patients with symptoms due to chronic heart failure despite diuretic therapy were randomised to receive additional treatment with either hydralazine or captopril. The dose was titrated; 24 received hydralazine and 26 captopril up to a maximum daily dosage of 225 mg and 75 mg respectively. Forty-three patients had coronary heart disease and seven dilated cardiomyopathy. 2. Dyspnoea and tiredness were assessed using a visual analogue scale (0-100) before and during 12 weeks' treatment. Captopril produced a significantly greater reduction in breathlessness (F = 31.6, P less than 0.001) and tiredness (F = 65.8, P less than 0.001) compared with hydralazine. 3. There was an increase in treadmill exercise time during treatment with both hydralazine (from 5.5 (3.47-7.53) min to 6.9 (4.87-8.93) min), and captopril (from 5.0 (3.05-6.95) min to 7.8 (5.85-9.75) min), but the degree of improvement was significantly greater in the patients treated with captopril (F = 7.4, P less than 0.001). 4. There was no significant change in right ventricular ejection fraction (from 27.9 (19.3-36.5)% to 28.7 (20.1-37.3)%) or left ventricular ejection fraction (from 22.2 (14.2-30.2)% to 23.9 (15.9-31.9)%) during treatment with hydralazine. However, both right and left ventricular ejection fraction increased significantly during treatment with captopril (from 27.1 (18.9-35.3)% to 32.0 (23.8-40.2)%, P less than 0.05; and from 25.0 (17.2-32.8)% to 29.6 (21.8-37.4)%, P less than 0.05 respectively). 5. These results suggest that in patients with symptoms due to chronic heart failure despite diuretic therapy, treatment with captopril produces a greater symptomatic and haemodynamic improvement than treatment with hydralazine.

Neuroendocrine activity in congestive heart failure

The increased neuroendocrine activity in patients with congestive heart failure appears to be a generalized attempt to maintain blood pressure at the expense of reduced cardiac performance and salt and water retention. It is likely that baroreceptor dysfunction contributes to increased sympathetic nervous system activity in patients with congestive heart failure. The usual tonic inhibitory messages emanating from baro- and mechanoreceptors in the great vessels and heart fail to adjust sympathetic traffic from the brain to the periphery, leading to uninhibited sympathetic tone. Arginine vasopressin and plasma renin activity may be increased secondarily; however, plasma renin activity activation could also be induced by a low-salt diet and diuretic use. Preliminary baseline data indicate that patients with left ventricular dysfunction (ejection fraction less than or equal to 35%) but no or very mild symptoms of heart failure have increased plasma levels of norepinephrine, atrial natriuretic factor and arginine vasopressin, while plasma renin activity is normal, suggesting that neuroendocrine activity contributes to the pathogenesis of congestive heart failure. Neurohormones such as angiotensin II may alter gene expression, leading to changes in the shape and size of the cell. Remodeling of the heart and blood vessels is associated with both heart failure and hypertension. Angiotensin-converting enzyme inhibitors have been demonstrated to retard or reverse the remodeling process under certain experimental conditions. Studies are currently under way to test this possibility in patients.

Enalapril as initial and sole treatment in severe chronic heart failure with sodium retention

Five patients, who had never received any drug treatment but who had severe chronic congestive heart failure with salt and water retention, were studied before and after a single dose of enalapril (10 mg orally). Three patients continued on enalapril as monotherapy (10 mg b.d. orally) for one month. Central haemodynamics, body fluid volumes, renal function and plasma hormones were measured at rest. The initial mean right atrial pressure was 13 +/- 4 mm Hg, pulmonary wedge pressure 29 +/- 4 mm Hg and cardiac index 1.8 +/- 0.21/min/m2. Enalapril, given acutely, caused only small changes. Two patients were withdrawn after the single dose of enalapril and treated with diuretics for clinical reasons. The remaining three patients each lost more than 4 kg in weight after one month of treatment with enalapril alone. Total body exchangeable sodium and total body water were reduced but central haemodynamics were unchanged. Although enalapril was of some benefit when given alone to patients with severe congestive heart failure, all five patients were finally treated with diuretics for clinical reasons. Enalapril is not recommended as the initial and only therapy for patients with severe congestive heart failure.

Prognostic value of hyponatremia in patients with severe chronic heart failure

In order to evaluate the incidence and the prognostic value of hyponatremia (hypoNa) in patients (pts) with severe chronic heart failure (SCHF), the authors studied 161 consecutive pts (113M, 48F ages sixty-seven +/- ten) with SCHF in NYHA class III-IV. The cause of SCHF was ischemic in 64 pts, hypertensive in 39, valvular in 14, alcohol-related in 3, and idiopathic in 41. Pretreatment hypoNa (less than 135 mmol/L) was found in 64/161 pts (40%) (Group I); Na+ was less than 125 in 10 pts, 125-130 in 19, and 131-135 mmol/L in 35; 42/64 pts (66%) of Group I were in NYHA class IV at admission. In the pts with pretreatment Na+ less than 125 mmol/L, hypoNa was persistent and refractory to high-dose furosemide (less than 500 mg/day) and water restriction. Cardiovascular mortality of Group I pts was 69% within twenty-four months (34 pts died of low-output syndrom and 10 suddenly). All pts with Na+ less than 130 mmol/L died within six months. The 20 pts who normalized Na+ are alive, and in NYHA class II-III (follow-up: twenty-six +/- fifteen, six to sixty months). Pts without hypoNa were 97/161 (Group II), and 58/97 (60%) are alive (follow-up: thirty +/- eighteen, five to fifty-eight months), whereas 39 pts died (27 suddenly, 9 of low-output syndrome, and 3 of extracardiac disease) within twenty-four months. The mortality rate of Group II was significantly lower (40% vs 69%, p less than 0.001) compared with Group I. The two groups were similar for age, sex, and cause and duration of SCHF.(ABSTRACT TRUNCATED AT 250 WORDS)

Interrelation of electrolytes and renin-angiotensin system in congestive heart failure

Many of the electrolyte derangements seen in chronic heart failure are related to activation of the renin-angiotensin system. Activation of the system may cause the retention of both sodium and water; the former is primarily related to the release of aldosterone and the latter is related to an angiotensin-mediated increase in thirst and decrease in the excretion of free water. The interaction of these mechanisms may explain why patients with chronic heart failure have higher values for total body sodium but lower values for serum sodium concentration than hypertensive patients or normal subjects. Activation of the renin-angiotensin system may also cause potassium depletion, which is manifest clinically by a decrease in both total body potassium and serum potassium concentration. These electrolyte disturbances may play a role in the development of ventricular arrhythmias. The renin-angiotensin system may also contribute to the development of magnesium deficits. These hormone-electrolyte interactions have important implications in the treatment of patients with heart failure, especially those in whom the renin-angiotensin system is pharmacologically inhibited.

The vasopressor system in patients with heart failure due to idiopathic dilated cardiomyopathy--influence of the clinical stage of disease and of chronic drug treatment

Alterations in the vasopressor system found in cardiac failure are part of compensatory measures that may modify pharmacologic-therapeutic response. Therefore, in 64 patients with dilated cardiomyopathy, we investigated its enhanced activity in different clinical stages of the disease as compared to normal controls. Patients in NYHA class II (n = 20) demonstrated increased activity of the sympathico-adrenal, renin-angiotensin-aldosterone, vasopressin, and atrial natriuretic factor systems, while maximum values were found in patients of NYHA class IV (n = 24). In these patients, noradrenaline was enhanced by a factor of 7, adrenaline by a factor of 2, plasma-renin-activity by a factor of 7, angiotensin II by a factor of 2.5, aldosterone by a factor of 5, vasopressin by a factor of 1.5, and ANF by a factor of 4 as compared to normal controls. Clinical NYHA classes correlated to a certain degree with the various plasma hormones. Patients treated with an aldosterone inhibitor in addition to digitalis and diuretics revealed significantly higher values for aldosterone, vasopressin, and angiotensin II as compared to those who received digitalis and diuretics alone. The addition of ACE-inhibitor therapy resulted in a decrease of angiotensin II, aldosterone, and vasopressin. Plasma catecholamines and ANF, however, did not change under the influence of cardiac medication. Diuretic treatment in NYHA class II patients reduced plasma volumes (p less than 0.01). Plasma volume in NYHA class IV patients only was found to be higher than in normal controls. Thus, analysis of the neurohumoral system can aid both in the identification of the clinical degree of dilated cardiomyopathy and in its optimal therapy.

Edema of cardiac origin. Studies of body water and sodium, renal function, hemodynamic indexes, and plasma hormones in untreated congestive cardiac failure

This study provides data on plasma hormone levels in patients with severe clinical congestive cardiac failure who had never received therapy and in whom the presence of an accumulation of excess water and sodium had been established. Eight patients were studied; two had ischemic cardiac disease, and six had dilated cardiomyopathy. Mean hemodynamic measurements at rest were as follows: cardiac index, 1.8 l/min/m2; pulmonary wedge pressure, 30 mm Hg; right atrial pressure, 15 mm Hg. Total body water content was 16% above control, extracellular liquid was 33% above control, plasma volume was 34% above control, total exchangeable sodium was 37% above control, renal plasma flow was 29% of control, and glomerular filtration rate was 65% of control. Plasma norepinephrine was consistently increased (on average 6.3 times control), whereas adrenaline was unaffected. Although plasma renin activity and aldosterone varied widely, they were on average above normal (renin 9.5 times control, aldosterone 6.4 times control). Plasma atrial natriuretic peptide (14.3 times control) and growth hormone (11.5 times control) were consistently increased. Cortisol was also increased on average (1.7 times control). Vasopressin was increased only in one patient.

Alterations in serum sodium in relation to atrial natriuretic factor and other neuroendocrine variables in experimental pacing-induced heart failure

The pathophysiologic role of atrial natriuretic factor and other neuroendocrine variables in relation to serum sodium and renal function was evaluated in 15 conscious dogs with severe chronic ventricular pacing-induced heart failure (250 beats/min for 5.1 +/- 0.4 weeks). Six sham-operated dogs observed over an 8 week period served as controls. Development of heart failure was characterized by a progressive increase in plasma norepinephrine, renin activity and aldosterone from control values of 293 +/- 15 pg/ml, 1.4 +/- 0.4 ng/ml per h and 124 +/- 42 pg/ml, respectively, to 1,066 +/- 96 pg/ml, 10.2 +/- 2.4 ng/ml per h and 577 +/- 151 pg/ml (all p less than 0.01), respectively, at severe heart failure. In contrast to other neuroendocrine variables, plasma atrial natriuretic factor increased from a control level of 243 +/- 74 pg/ml to a peak concentration of 724 +/- 149 pg/ml (p less than 0.01) at 2 weeks, then declined and plateaued at twice the level of the control value as severe heart failure developed. At severe heart failure, serum sodium decreased from 147 +/- 0.6 to 141.8 +/- 2.1 mmol/liter (p less than 0.05), whereas urea increased from 6.0 +/- 0.5 to 7.8 +/- 0.6 mmol/liter (p less than 0.05). The change in serum sodium concentration correlated with plasma renin activity and aldosterone (r = -0.77, -0.88, respectively, both p less than 0.01), but not with norepinephrine or atrial natriuretic factor. When sinus rhythm was restored, 14 dogs were observed for 48 to 72 h and 8 dogs were followed up for another 4 weeks after cessation of pacing.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial natriuretic peptide concentrations in hypoxic secondary pulmonary hypertension: relation to haemodynamic and blood gas variables and response to supplemental oxygen

Plasma atrial natriuretic peptide concentrations, measured in samples drawn from the pulmonary artery, were raised in nine of 17 patients with hypoxic pulmonary hypertension but normal right atrial pressures at rest. No relationship was seen between atrial natriuretic peptide concentrations and mean pulmonary artery or right atrial pressure, or calculated pulmonary or systemic vascular resistance. Patients with the most severe hypoxaemia tended to have higher plasma atrial natriuretic peptide concentrations; three patients with no past history of oedema had concentrations more than twice the upper limit of normal. Treatment with supplementary oxygen for 30 minutes reduced pulmonary vascular resistance in all patients but had no significant effect on plasma atrial natriuretic peptide concentration. These findings suggest that atrial natriuretic peptide may be a factor in the control of sodium and water balance in hypoxic cor pulmonale, where the determinants of individual susceptibility to peripheral oedema are not well understood.

Clinical applications of antimineralocorticoids

The renin-angiotensin-aldosterone system plays an important role in the development and maintenance of high blood pressure in several forms of hypertension. In hypertensive patients with primary aldosteronism, antimineralocorticoids are, as expected, very effective in reducing blood pressure and correcting metabolic disturbances. In patients with essential hypertension, an abnormal relationship between angiotensin II and aldosterone can occur. Aldosterone secretion in these patients is often too high relative to circulating levels of angiotensin II. Antimineralocorticoids effectively lower blood pressure in a large number of these patients. The reactive hyperreninemia caused by salt depletion is a factor limiting the antihypertensive effect of natriuretic agents including that of antimineralocorticoids. The enhanced aldosterone secretion resulting from treatment with a diuretic other than an antimineralocorticoid may diminish the natriuretic action of that diuretic. Therefore, antimineralocorticoids given in addition to a diuretic enhance natriuresis. The renin-angiotensin-aldosterone system is also involved as a compensatory mechanism in cardiovascular and body fluid homeostasis of patients with severe congestive heart failure or liver cirrhosis with ascites. Antimineralocorticoids are very effective in such conditions. In patients with congestive heart failure treated with digitalis, these natriuretic agents are particularly useful because of their potassium-sparing properties. The risk of developing hyperkalemia during antimineralocorticoid administration is negligible unless renal function is impaired. Antimineralocorticoids have the advantage of exerting no deleterious effect on carbohydrate and lipid metabolism. The use of these agents seems therefore rational in a variety of diseases concerned with blood pressure and body fluid volume regulation.

Neurohumoral responses to chronic myocardial infarction in rats

In chronic cardiac failure, various neurohumoral mechanisms are activated to sustain blood volume, blood pressure, and organ perfusion. Using the coronary artery ligation model of heart failure in the rat, we have measured changes in vasoactive hormone secretion and related these changes to salt and water status during a 1-month period. When compared with controls, rats with infarction had a marked rise in plasma atrial natriuretic peptide (294 +/- 59 vs. 79 +/- 10 pg/ml, p less than 0.001) although there was no increase in total exchangeable body sodium. Plasma renin activity and plasma aldosterone concentrations were the same for both rats with infarction and controls. Similarly, there were no significant differences in plasma arginine vasopressin, plasma osmolality, or plasma sodium concentration in rats with infarction. Ventricular norepinephrine levels were reduced in animals with infarction (p less than 0.01). Plasma atrial natriuretic peptide levels were raised in this model of chronic left ventricular failure. However, there was no salt retention and little stimulation of the renin-angiotensin-aldosterone system or vasopressin. The results suggest that high circulating atrial natriuretic peptide levels may prevent or limit salt and water retention, either directly or indirectly, by inhibiting the renin-angiotensin-aldosterone system.

Arrhythmias, catecholamines and electrolytes

The prognosis in patients with heart failure secondary to left ventricular dysfunction is poor. Although survival can be related to the extent of cardiac functional impairment, many patients die suddenly rather than in refractory heart failure. Ambulatory electrocardiography has revealed a high prevalence of simple and complex ventricular arrhythmias in these patients, which was the most important predictor of subsequent mortality in our patients. Factors predisposing to arrhythmias are many, but increased catecholamines and electrolyte abnormalities are among the more obvious. In patients who have undergone treatment for congestive heart failure, serum and total body potassium are reduced, and this is closely and inversely related to the state of activation of the renin-angiotensin system. Renin and noradrenaline are also closely and directly correlated, while both are inversely related to the arterial pressure. Treatment with angiotensin-converting enzyme inhibitors tends to reverse these neuroendocrine and electrolyte abnormalities and reduces the frequency of ventricular arrhythmias. Whether this will have a favorable impact on mortality, and, in particular, on sudden death, remains to be seen.

The effect of treatment of congestive heart failure on plasma atrial natriuretic peptide concentration: a longitudinal study

Eleven patients with acute congestive heart failure were studied during treatment with a loop diuretic. Plasma concentrations of atrial natriuretic peptide were considerably increased before treatment and with successful treatment returned progressively towards normal values. There was a statistically significant correlation between plasma atrial natriuretic peptide concentration and both jugular venous pressure and change of body weight. These results support the hypothesis that atrial distension is an important stimulus to atrial natriuretic peptide release. Furthermore, the close relation between plasma concentrations of atrial natriuretic peptide and clinical improvement in these patients suggests that measurement of plasma atrial natriuretic peptide concentration could provide a clinically useful and non-invasive method of monitoring the response to treatment.

Total body electrolyte composition in patients with heart failure: a comparison with normal subjects and patients with untreated hypertension

Total body elemental composition was measured in 40 patients with well documented heart failure who were oedema-free on digoxin and diuretics. The results were compared with values for 20 patients with untreated essential hypertension matched for height, weight, age, and sex. Total body potassium alone was also measured in 20 normal subjects also matched for anthropomorphic measurements. Patients with hypertension had a very similar total body potassium content to that of normal subjects, but patients with heart failure had significantly reduced total body potassium. This could not be explained by muscle wasting because total body nitrogen, largely present in muscle tissue, was well maintained. When total body potassium was expressed as a ratio of potassium to nitrogen mass a consistent depletion of potassium was revealed in the group with heart failure. Potassium depletion was poorly related to diuretic dose, severity of heart failure, age, or renal function. Activation of the renin-angiotensin-aldosterone system was, however, related to hypokalaemia and potassium depletion. Such patients also had significantly lower concentrations of serum sodium and blood pressure. Serum potassium was related directly to total body potassium. Despite the absence of clinically apparent oedema total body chlorine was not consistently increased in heart failure, but the calculated extracellular fluid volume remained expanded in the heart failure group. Total body sodium was significantly increased in patients with heart failure, but less than half of this increase could be accounted for by extracellular fluid volume expansion. Potassium depletion in heart failure may account in part for the high frequency of arrhythmias and sudden death in this condition.

Hemodynamic changes and renal plasma flow in early heart failure: implications for renin, aldosterone, norepinephrine, atrial natriuretic peptide and prostacyclin

Vasoconstrictory and vasodilatory hormone systems may be important in the regulation of peripheral vascular resistance and renal hemodynamics in the early phase of heart failure. The activity of the renin-angiotensin-aldosterone system (RAAS), the sympathetic nervous activity, and, as possible counterregulating systems, the activity of prostacyclin and atrial natriuretic peptide (ANP) were studied in 6 conscious dogs during the first 4 days of congestive heart failure in relation to hemodynamic changes and renal plasma flow. Congestive heart failure was induced by rapid right ventricular pacing, which caused a considerable decrease of cardiac output (-38%; p less than 0.05), oxygen saturation of the mixed venous blood (-13%; p less than 0.05), and mean arterial pressure (-24 mm Hg; p less than 0.05) on the 4th day. Mean pulmonary arterial pressure and mean pulmonary capillary wedge pressure increased (+4 mm Hg; p less than 0.05 and +7 mm Hg, respectively; p less than 0.05). Renal plasma flow was slightly reduced (N.S.), renal vascular resistance did not change. Peripheral vascular resistance showed a significant increase only on the 1st day. Sympathetic nervous activity was stimulated (from 175 +/- 31 pg/ml to 391 +/- 100 pg/ml; p less than 0.05), while plasma renin concentration was significantly suppressed on the 4th day (from 3.3 +/- 0.4 ngAI/ml/h to 1.9 +/- 0.5 ngAI/ml/h; p less than 0.05), and plasma aldosterone levels were decreased (from 108 +/- 12 pg/ml to 76 +/- 12 pg/ml; p less than 0.05). ANP increased 3-fold (p less than 0.05) and 6-keto-prostaglandin F1 alpha increased in 4 out of 6 dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

The clinical use of angiotensin converting enzyme inhibitors in hypertension and cardiac failure

The renin-angiotensin system has a range of physiological actions concerned with the control of the circulation. Angiotensin II has both an immediate and a delayed pressor effect, it stimulates the secretion of aldosterone and antidiuretic hormone, promotes thirst, stimulates the sympathetic nervous system at various sites while inhibiting vagal tone, and has a range of direct effects on the kidney. Several aspects of this range of actions can become deranged in a number of forms of hypertension as well as in congestive cardiac failure. Hence much effort has been directed in recent years to the development of agents designed to interfere with the renin-angiotensin system and to apply these clinically in the treatment of hypertension and congestive cardiac failure. Orally active converting enzyme inhibitors are of proven benefit not only in renovascular hypertension, but also, when combined with loop diuretics, in the treatment of intractable hypertension as well as, both alone and in combination with thiazide diuretics, in the treatment of essential hypertension. In congestive cardiac failure controlled trials have shown that converting enzyme inhibitors can improve exercise tolerance while diminishing lassitude, correct potassium deficiency and limit ventricular arrhythmias. Energetic efforts are being made to develop orally active inhibitors of the enzyme renin itself, since these would be more specific in action than the presently available and very successful converting enzyme inhibitors.

Untreated heart failure: clinical and neuroendocrine effects of introducing diuretics

The clinical and neuroendocrine response to diuretic treatment was assessed at rest and on exercise in 12 patients with heart failure. Before treatment all patients were limited by breathlessness on exercise; one was oedematous. Plasma renin activity and aldosterone were normal but plasma noradrenaline was raised both at rest and on exercise. After one month's treatment with frusemide (40 mg) and amiloride (5 mg) weight was significantly reduced by a mean of 3.5 kg and exercise capacity had doubled. Plasma noradrenaline fell to normal at rest but remained abnormally raised on exercise. Plasma renin activity and aldosterone increased significantly both at rest and on exercise. Diuretics bring about a considerable clinical improvement in patients with chronic heart failure but they stimulate the renin-angiotensin system. Activation of the renin-angiotensin system in moderate heart failure occurs as a response to diuretic treatment rather than as a result of the disease process itself.

Plasma alpha natriuretic peptide in cardiac impairment

Regional plasma alpha human atrial natriuretic peptide concentrations were measured, and their relation to intracardiac pressures assessed, in an unselected series of 45 patients undergoing diagnostic cardiac catheterisation. Arteriovenous gradients in plasma concentrations of alpha human atrial natriuretic peptide were consistent with its cardiac secretion and its clearance by the liver and kidneys. Plasma concentrations of the peptide in the pulmonary artery, aorta, and superior vena cava correlated closely with the mean right atrial and pulmonary arterial pressures, and similar, though weaker, positive relations were seen with the left ventricular end diastolic and pulmonary artery wedge pressures. Concentrations of both atrial natriuretic peptide and renin showed significant inverse relations with serum sodium concentrations. Plasma concentrations of alpha human atrial natriuretic peptide are an additional objective indicator of the severity of haemodynamic compromise in patients with cardiac impairment.

Vasopressin, renin and norepinephrine levels before and after captopril administration in patients with congestive heart failure due to idiopathic dilated cardiomyopathy

The effects of 4 weeks of captopril treatment were studied in 10 patients with chronic congestive heart failure (CHF). Acute administration of 50 mg of captopril resulted in an increase in cardiac index and significant decreases in arterial pressure, peripheral vascular resistance and pulmonary capillary wedge pressure. Before treatment, all patients had elevated vasopressin levels (17 +/- 4 pg/ml) relative to decreased plasma osmolality (274 +/- 15 mOsm/kg H2O), and these values were not initially affected by captopril administration (22 +/- 7 pg/ml). However, the relation between arginine vasopressin and plasma osmolality was restored to normal by long-term therapy with captopril (50 mg 3 times daily) (3.0 +/- 1.3 pg/ml; 283 +/- 166 mOsm/kg H2O), which also resulted in sustained improvement of cardiac function. Long-term captopril therapy increased plasma renin concentration from already elevated levels (11 +/- 4 to 32 +/- 8 ng AI/ml X hour) and decreased plasma norepinephrine from 1,054 +/- 244 to 488 +/- 101 pg/ml. Thus, nonosmolar stimulation of vasopressin secretion in CHF can be restored to normal by chronic converting enzyme blockade. The acute vasodilator effects of converting enzyme blockade are not mediated by a reduction of possible vasoconstrictor effects of vasopressin.