"Escape" of aldosterone production in patients with left ventricular dysfunction treated with an angiotensin converting enzyme inhibitor: implications for therapy

Aldosterone receptor antagonists: focus on eplerenone

Despite the development of hypertension treatment guidelines, blood pressure control in the general population remains inadequate, indicating the need for ongoing re-evaluation of treatment strategies to further improve blood pressure control. Hypertension results from alterations in cardiac output and/or peripheral resistance. The renin-angiotensin-aldosterone system may be responsible, at least in part, for these alterations. Despite pharmacologic intervention with angiotensin-converting enzyme inhibitors and angiotensin type-1 receptor antagonists, aldosterone continues to be produced. Therapeutic modalities for treating hypertension directed toward antagonizing aldosterone might more effectively control blood pressure. Eplerenone, a new selective aldosterone receptor antagonist, recently received approval from the US Food and Drug Administration for the treatment of hypertension, either alone or in combination with other antihypertensive agents. The objective of this review is to summarize the renin-angiotensin-aldosterone system, emphasizing the role for aldosterone antagonism in the management of hypertension, with a focus on eplerenone.

Single- and repeated-dose pharmacokinetics of eplerenone, a selective aldosterone receptor blocker, in rats

1. The pharmacokinetics of eplerenone (EP) were examined in rats following single or repeated dosing with (14)C-labelled or unlabelled EP to characterize absorption, metabolism and excretion. Rates of EP metabolism and cytochrome P450 activities were determined in vitro after repeated dose administration of EP. 2. Following a single i.v. dose (15 mg kg(-1)), the elimination half-life of EP was 0.80 and 1.14 h in male and female rats, respectively. Plasma clearances (CL) of EP were 1.62 and 1.20 l kg(-1) h(-1) in males and females, respectively. Following a single oral dose (15 mg kg(-1)), C(max) and T(max) of EP were 1.71 micro g ml(-1) and 0.5 h in male rats. The corresponding values in female rats were 3.54 micro g ml(-1) and 1.0 h. The systemic availability of EP was 25.6% in male rats and 66.4% in female rats, demonstrating sex differences in the pharmacokinetics of EP. 3. In the 8-day study, the AUC(0-24h)'s of total EP (closed lactone ring form plus open form) following 100 and 200 mg kg(-1) oral doses were approximately half those on day 1 in male rats. After repeated dosing for 13 weeks, the pharmacokinetics of total EP did not change with study duration at the 20 mg kg(-1) dose in both males and females. However, at the 100 mg kg(-1) dose, AUC(0-24h)'s were notably reduced on day 24 but progressively increased on subsequent days to approximate day 1 levels by day 86 in both sexes. At the 500 mg kg(-1) dose, the AUCs on day 86 remained lower than those on day 1. Reductions in AUCs on days 8 and 24 appeared to be the result of metabolism induction. 4. EP was extensively metabolized in male rats and most faecal and urinary radioactivity was in the form of metabolites. In female rats, the vast majority of urine and faecal radioactivity was associated with total EP. Thus, the sex difference in the pharmakokinetics of EP was due to more extensive metabolism in male rats. 5. The major metabolite in the rat was 6beta-OH EP. EP 6beta-hydroxylase activity was well correlated with testosterone 6beta-hydroxylase activity, indicating that EP metabolism to 6beta-OH EP was mediated primarily by CYP3A in the rat. 6. After repeated dose administration, EP increased 6beta-hydroxylase activities of testosterone and EP itself in a dose-dependent manner in both male and female rats, indicating that EP was a CYP3A inducer in the rat. There appeared to be no effects on activities of CYP1A1, 2B and 2E1.

Aldosterone as a target in congestive heart failure

Based upon the results of the RALES trial and accumulating evidence about the role of aldosterone and aldosterone receptor antagonism in various disease states, the authors anticipate that aldosterone receptor antagonists will become standard therapy, along with ACE inhibitors and beta-adrenergic receptor blocking agents, in patients with heart failure that is caused by systolic left ventricular dysfunction. Furthermore, the prospect of the use of these agents in other disease states that have implicated an activated rennin-angiotensin-aldosterone cascade, such as diastolic dysfunction, aging, and atherosclerosis, remains to be tested. Until further data from well-designed, prospective, randomized trials are available, the use of aldosterone receptor antagonists should be restricted to patients with severe or progressive heart failure caused by systolic left ventricular dysfunction in whom serum creatinine level is < or = 2.0 mg/dL and serum potassium levels are < 5.0 meq/L at baseline.

Central mineralocorticoid receptor blockade decreases plasma TNF-alpha after coronary artery ligation in rats

The Randomized Aldactone Evaluation Study (RALES) demonstrated a substantial clinical benefit to blocking the effects of aldosterone (Aldo) in patients with heart failure. We recently demonstrated that the enhanced renal conservation of sodium and water in rats with heart failure can be reduced by blocking the central nervous system effects of Aldo with the mineralocorticoid receptor (MR) antagonist spironolactone (SL). Preliminary data from our laboratory suggested that central MR might contribute to another peripheral mechanism in heart failure, the release of proinflammatory cytokines. In the present study, SL (100 ng/h for 21 days) or ethanol vehicle (Veh) was administered via the 3(rd) cerebral ventricle to one group of rats after coronary ligation (CL) or sham CL (Sham) to induce congestive heart failure (CHF). In Veh-treated CHF rats, tumor necrosis factor-alpha (TNF-alpha) levels increased during day 1 and continued to increase throughout the 3-wk observation period. In CHF rats treated with SL, started 24 h after CL, TNF-alpha levels rose initially but retuned to control levels by day 5 after CL and remained low throughout the study. These findings suggest that activation of MR in the central nervous system plays a critical role in regulating TNF-alpha release in heart failure rats. Thus some of the beneficial effect of blocking MR in heart failure could be due at least in part to a reduction in TNF-alpha production.

Heart failure and the brain: new perspectives

Despite recent therapeutic advances, the prognosis for patients with heart failure remains dismal. Unchecked neurohumoral excitation is a critical element in the progressive clinical deterioration associated with the heart failure syndrome, and its peripheral manifestations have become the principal targets for intervention. The link between peripheral systems activated in heart failure and the central nervous system as a source of neurohumoral drive has therefore come under close scrutiny. In this context, the forebrain and particularly the paraventricular nucleus of the hypothalamus have emerged as sites that sense humoral signals generated peripherally in response to the stresses of heart failure and contribute to the altered volume regulation and augmented sympathetic drive that characterize the heart failure syndrome. This brief review summarizes recent studies from our laboratory supporting the concept that the forebrain plays a critical role in the pathogenesis of ischemia-induced heart failure and suggesting that the forebrain contribution must be considered in designing therapeutic strategies. Forebrain signaling by neuroactive products of the renin-angiotensin system and the immune system are emphasized.

The role of angiotensin II receptor blockers in the treatment of heart failure patients

Evidence from large, randomized, controlled clinical trials supports the use of angiotensin-converting enzyme (ACE) inhibitors, beta blockers, and spironolactone to reduce mortality and morbidity. Despite these effective therapies, event rates related to heart failure remain high. Although ACE inhibitors reduce angiotensin II production, they do not fully suppress the increased angiotensin II production in heart failure. Angiotensin II receptor blockers (ARBs) directly block the effect of angiotensin II, derived from any source, at the receptor level and have the potential to be as effective or even more effective than ACE inhibitors. The results of a number of clinical studies have demonstrated ARBs are effective and well tolerated. However, no studies have demonstrated a convincing decrease in mortality with ARB use, although a decrease has been observed for heart failure hospitalization. The results from further studies are awaited to clarify the role of ARBs in the treatment of heart failure.

Combined effects of enalapril and spironolactone in hamsters with dilated cardiomyopathy

Chronic angiotensin I-converting enzyme inhibition can be associated with aldosterone escape. We investigated the effects of enalapril, spironolactone, and their combination on hemodynamics and cardiac remodeling in cardiomyopathic hamsters to determine whether these drugs could exert additive effects. Cardiomyopathic hamsters, Bio TO-2 dilated strain, were orally treated with enalapril (20 mg. kg. day ) and/or spironolactone (20 mg. kg. day ) according to a 2 x 2 factorial design from 120 days of age. Animals were investigated at 180 (10 animals per group) and 240 (16 animals per group) days of age. Compared with corresponding untreated groups, enalapril significantly decreased mean blood pressure (-18%); enalapril and spironolactone significantly increased cardiac output (+28%, +11%) and femoral blood flow (+10%, +12%) and significantly decreased systemic (-38%, -17%) and femoral (-26%, -13%) vascular resistances. Enalapril and spironolactone significantly decreased left ventricle cavity area (-21%, -26%) and left (-34%, -47%) and right (-37%, -48%) ventricle collagen density. Spironolactone significantly increased left ventricle wall thickness (+4%). There were significant enalapril x spironolactone interactions for most variables (compared with control group, +52%, +36%, +45% for cardiac output; +26%, +28%, +26% for femoral blood flow; -50%, -30%, -45% for systemic vascular resistance; -33%, -20%, -35% for femoral vascular resistance; -27%, -31%, -40% for left ventricle cavity area; and -46%, -58%, -60% for left and -39%, -50%, -66% for right ventricle collagen density in enalapril, spironolactone, and enalapril + spironolactone groups, respectively). In cardiomyopathic hamsters, enalapril and spironolactone in combination did not improve hemodynamics more than enalapril alone but induced stronger effects than each drug alone on cardiac remodeling.

Aldosterone: cardiovascular assault

BACKGROUND

Blocking the renin-angiotensin-aldosterone system with angiotensin-converting enzyme inhibitors has improved cardiovascular morbidity and mortality rates. However, because of aldosterone "escape," the effectiveness of this blockade decreases over time.

METHODS

Various in vitro and in vivo studies were evaluated to determine the mechanisms by which aldosterone contributes to morbidity and mortality.

RESULTS

Aldosterone has several deleterious properties. It causes a vasculopathy with both endothelial dysfunction and a reduction in fibrinolysis, leading to heart, brain, and kidney damage. Aldosterone causes myocardial hypertrophy and fibrosis, autonomic imbalance, and electrolyte abnormalities, contributing to myocardial dysfunction, arrhythmias, and sudden cardiac death. Studies have shown that all of these deleterious effects can, at least in part, be reversed by aldosterone receptor blockade. This may explain why adding an aldosterone blocker to standard heart failure therapy, including angiotensin-converting enzyme inhibitors, reduces morbidity and mortality rates by an additional 30% compared with standard therapy alone.

CONCLUSIONS

Eplerenone is a selective aldosterone blocker whose role in reducing morbidity and mortality rates in patients with cardiovascular disease is being investigated.

Renin angiotensin aldosterone and adrenergic modulation in chronic heart failure: contemporary concepts

Whereas the earlier conceptual targets of heart failure therapy, such as the cardio-renal and hemodynamic models, all fulfilled the basic needs of symptomatic relief and hemodynamic improvement, only the neurohormonal model has provided an effective target to address symptom relief in concert with survival benefits. Recent data allude to a disease-modifying effect of angiotensin-converting enzyme inhibitors (ACE-Is) in retarding the new development of heart failure in high-risk populations. Angiotensin receptor antagonists (ARBs) have not been demonstrated to be superior to ACE-Is and their value in achieving incremental benefits in addition to ACE-Is is limited to scenarios in which beta-adrenergic receptor blocker therapy is not applicable. Beta-adrenergic receptor blockade in addition to ACE inhibition offers incremental benefits that are achieved early and are beneficial in most stages of severity except in the presence of overt decompensation. Unlike ACE-Is, beta-adrenergic receptor blockers cannot be construed as a class but are heterogeneous in their therapeutic response.

The pathophysiology of aldosterone in the cardiovascular system

Until relatively recently, the mineralocorticoid hormone aldosterone was thought to be produced uniquely in the adrenal cortex and to act exclusively on epithelia to promote sodium retention and potassium excretion. However, it is now known that aldosterone also acts on nonepithelial tissues, such as brain, heart, and blood vessels, and that enzymes required for aldosterone biosynthesis are expressed in these same tissues, which may be consistent with local aldosterone production acting in a paracrine fashion. A number of studies indicate that aldosterone exerts clearly deleterious effects when levels are inappropriate for salt status. For example, aldosterone in a high-salt environment initiates a vascular inflammation response that leads to cardiac and vascular pathologies. In experimental models of hypertension and heart failure, the nonepithelial effects of aldosterone are mediated via classical mineralocorticoid receptors, and are largely or completely abolished by administration of the selective aldosterone blocker eplerenone or by reduction of circulating aldosterone by adrenalectomy. In the present manuscript, we review some of the most recent discoveries in the field of aldosterone biology, with special emphasis on the mechanisms involved in the deleterious actions of this mineralocorticoid in cardiovascular tissues.

Mineralocorticoid and angiotensin receptor antagonism during hyperaldosteronemia

Elevated aldosterone levels induce a spironolactone-inhibitable decrease in cardiac sarcolemmal Na+-K+ pump function. Because pump inhibition has been shown to contribute to myocyte hypertrophy, restoration of Na+-K+ pump function may represent a possible mechanism for the cardioprotective action of mineralocorticoid receptor (MR) blockade. The present study examines whether treatment with the angiotensin type 1 receptor antagonist losartan, with either spironolactone or eplerenone, has additive effects on sarcolemmal Na+-K+ pump activity in hyperaldosteronemia. New Zealand White rabbits were divided into 7 different groups: controls, aldosterone alone, aldosterone plus spironolactone, aldosterone plus eplerenone, aldosterone plus losartan, aldosterone plus losartan and spironolactone, and aldosterone plus losartan and eplerenone. After 7 days, myocytes were isolated by enzymatic digestion. Electrogenic Na+-K+ pump current (I(p)), arising from the 3:2 Na+:K+ exchange ratio, was measured by the whole-cell patch clamp technique. Elevated aldosterone levels lowered I(p); treatment with losartan reversed aldosterone-induced reduced pump function, as did MR blockade. Coadministration of spironolactone or eplerenone with losartan enhanced the losartan effect on pump function to a level similar to that measured in rabbits given losartan alone in the absence of hyperaldosteronemia. In conclusion, hyperaldosteronemia induces a decrease in I(p) at near physiological levels of intracellular Na+ concentration. Treatment with losartan reverses this aldosterone-induced decrease in pump function, and coadministration with MR antagonists produces an additive effect on pump function, consistent with a beneficial effect of MR blockade in patients with hypertension and congestive heart failure treated with angiotensin type 1 receptor antagonists.

Beneficial effect of replacing of angiotensin-converting enzyme inhibitor with angiotensin II antagonist for heart failure patients

OBJECTIVE

Angiotensin-converting enzyme (ACE) inhibitors and beta-blockers improve prognosis inpatients with chronic heart failure. Some patients, however, show little response to combined treatment with an ACE inhibitor and a beta-blocker. In addition, the ACE inhibitor cannot completely suppress angiotensin II production. Our objective was to examine whether replacing the ACE inhibitor with an angiotensin II antagonist can improve the condition of patients with chronic heart failure.

METHODS

In 11 patients with chronic heart failure treated with an ACE inhibitor and a beta-blocker, who have had severe left ventricular dysfunction or high plasma level of natriuretic peptides, left ventricular dimension, and fractional shortening, plasma atrial and brain natriuretic peptide (ANP and BNP) levels were determined before and 3 months after the change of treatment.

RESULTS

After substituting the ACE inhibitor with an angiotensin II antagonist, patients showed New York Heart Association functional class improvement, and significant decrease in left ventricular dimension and BNP.

CONCLUSION

In patients with severe chronic heart failure treated with an ACE inhibitor and a beta-blocker, replacing the ACE inhibitor with an angiotensin II antagonist may be effective. However, this has to be confirmed by an adequately powered randomized controlled study.

Long-term, dose-dependent effects of spironolactone on left ventricular function and exercise tolerance in patients with chronic heart failure

OBJECTIVES

This study was designed to assess the effects of spironolactone (SP) on left ventricular (LV) function and exercise tolerance in patients with chronic heart failure (CHF).

BACKGROUND

In severe heart failure (HF), SP improves survival, but the underlying mechanisms are not clear.

METHODS

We randomized 106 outpatients with HF to SP (12.5 to 50 mg/day) (group 1) or control (group 2). Complete echocardiography and cardiopulmonary exercise testing were performed at baseline and 12 months after randomization.

RESULTS

Left ventricular end-systolic volume at baseline and at follow-up was 188 +/- 94 ml and 171 +/- 97 ml in group 1 and 173 +/- 71 ml and 168 +/- 79 ml in group 2 (treatment group-by-time interaction, p = 0.03). Left ventricular ejection fraction at baseline and at follow-up was 33 +/- 7% and 36 +/- 9% in group 1 and 34 +/- 7% and 34 +/- 9% in group 2 (treatment group-by-time interaction, p = 0.02). At baseline, 9 patients in group 1 and 3 patients in group 2 had a restrictive mitral filling pattern, a marker of severe diastolic dysfunction; at follow-up, 3 patients in group 1 and no patient in group 2 improved their pattern. No patient in group 1 and 4 patients in group 2 worsened their pattern (chi-square, p = 0.02). Peak oxygen consumption increased significantly in patients treated with 50 mg of SP and decreased in group 2 (17.7 +/- 5.2 vs. 18.5 +/- 5.9 and 19.1 +/- 5.6 vs. 17.9 +/- 5.3, respectively; analysis of variance, p = 0.01).

CONCLUSIONS

Spironolactone improves LV volumes and function; furthermore, it improves exercise tolerance at the highest administered dose. Our data might explain the mortality reduction during aldosterone antagonism in patients with HF.

New therapeutics for chronic heart failure

Traditionally, clinicians have viewed heart failure either as a problem of excessive salt and water retention caused by abnormalities of renal blood flow, or as a hemodynamic problem associated with a reduced cardiac output and excessive peripheral vasoconstriction. Recently, clinicians have begun to adopt a neurohormonal model in which heart failure progresses because of the toxic effects of endogenous biological systems that become activated in heart failure. We review the rationale for existing heart failure therapies and discuss the reasoning behind the development of some emerging therapies.

Forebrain renin-angiotensin system has a tonic excitatory influence on renal sympathetic nerve activity

All elements of the renin-angiotensin system (RAS) are present in the forebrain, particularly in circumventricular organs surrounding the third cerebral ventricle. We tested the hypothesis that forebrain angiotensin-converting enzyme (ACE) has a tonic excitatory influence on sympathetic drive. Neurally intact and sinoaortic-denervated pentobarbital-anesthetized rats were treated with forebrain-directed intracarotid artery (ICA) versus intravenous injections of angiotensin I (ANG I) and of the ACE inhibitor captopril. In intact rats, ICA ANG I elicited a rise in arterial pressure and a concomitant reduction in renal sympathetic nerve activity (RSNA; ICA captopril elicited the opposite responses). In barodenervated rats, ICA ANG I increased and ICA captopril decreased arterial pressure and RSNA in parallel; intravenous ANG I had no effect on RSNA. The findings suggest that the intrinsic forebrain RAS has a tonic excitatory influence on sympathetic drive that is overshadowed in normal rats by baroreflex mechanisms, but may assume a more prominent role in pathophysiological states (e.g., heart failure) in which baroreflex mechanisms are impaired and RAS activity is augmented.

Relation of aldosterone "escape" despite angiotensin-converting enzyme inhibitor administration to impaired exercise capacity in chronic congestive heart failure secondary to ischemic or idiopathic dilated cardiomyopathy

In patients with chronic congestive heart failure (CHF), aldosterone production may occur despite the administration of angiotensin-converting enzyme (ACE) inhibitors. This phenomenon has been termed aldosterone "escape"; its relation to the severity of the disease is unknown. We sought to assess whether aldosterone escape might be related to disease severity or functional impairment in patients with CHF. One hundred forty-one consecutive patients with CHF who received ACE inhibitors (> 6 months) underwent an evaluation of neurohormonal activation and body composition, an echo-Doppler examination, and a cardiopulmonary exercise test. Aldosterone escape was defined as plasma levels of aldosterone above the normal range in our laboratory (> 0.42 nmol/L). Fourteen patients (10%) had aldosterone escape. There were no differences between patients with and without aldosterone escape with regard to age, New York Heart Association class, neurohormonal activation, ACE inhibitor dose, hemodynamics, or skeletal muscle bulk. In contrast, mean peak oxygen consumption (14.2 +/- 3.5 vs 17.3 +/- 4.9 ml/min/kg, p < 0.05) and the slope of the relation between ventilation and carbon dioxide production (41 +/- 7 vs 36 +/- 6, p <0.05) were significantly worse in patients with aldosterone escape compared with those without it. Thus, aldosterone escape is associated with reduced exercise capacity in patients with CHF. This factor does not seem to be linked with hemodynamic mechanisms or with a reduced skeletal muscle bulk.

Neurohormonal and clinical responses to high- versus low-dose enalapril therapy in chronic heart failure

OBJECTIVES

We sought to compare the neurohormonal responses and clinical effects of long-term, high-dose versus low-dose enalapril in patients with chronic heart failure (CHF).

BACKGROUND

Examination of neurohormonal and clinical responses in patients receiving different doses of angiotensin-converting enzyme (ACE) inhibitors may provide insight into the potential for additional suppression with angiotensin II (AT-II) or aldosterone antagonists.

METHODS

Seventy-five patients with CHF were randomized to receive either high-dose (40 mg/day, n = 37) or low-dose (5 mg/day, n = 38) enalapril over six months. The results from exercise testing, echocardiography, tissue-specific ACE activity and monthly pre- and post-enalapril neurohormonal levels were compared.

RESULTS

Despite greater intra-group improvements in plasma renin activity and serum aldosterone levels in the high-dose group, no statistically significant differences were observed between the two groups in all variables, except for serum ACE activity at the end of study. Elevated serum aldosterone and plasma AT-II levels were observed in 35% and 85% of patients, respectively, at 34 weeks, an inter-group difference that was not statistically significant. A trend toward higher levels of tissue-specific ACE activity in the high-dose group compared with the low-dose group at the end of study was observed (p = 0.054). A predefined composite end point of clinical events had a trend toward better improvement in the high-dose group.

CONCLUSIONS

This study could not demonstrate a difference between high- and low-dose enalapril in terms of serum aldosterone and plasma AT-II suppression, despite a dose-dependent reduction in serum ACE activity. Even at maximal doses of enalapril, elevated serum aldosterone and plasma AT-II levels were frequently observed.

Influence of plasma aldosterone on left ventricular geometry and diastolic function in treated essential hypertension

Since aldosterone is known to promote interstitial fibrosis in cardiac tissues, it is possible that aldosterone may influence cardiac structure and function. In the present study, we investigated whether plasma aldosterone concentration (PAC) is related to the distinct patterns of left ventricular (LV) geometry and LV diastolic function in treated essential hypertension. In 92 patients with chronically treated essential hypertension, two-dimensional and Doppler echocardiographic examinations were performed and LV inflow velocities were measured for evaluation of LV diastolic function. When patients were divided into four groups by the different LV geometric patterns, PAC in patients with eccentric hypertrophy was significantly higher than in those with concentric hypertrophy (15.2+/-2.1 vs. 10.0+/-0.7 ng/dl, p<0.01). However, the ratio of the peak velocity of early diastolic filling to that of atrial filling (EIA), an index of LV diastolic function, was significantly decreased in patients with concentric hypertrophy compared with those showing normal geometry. In the relationship between PAC and LV diastolic function, PAC was negatively correlated with EIA (r=-0.35, p<0.05) only in the subgroup with normal relative wall thickness (i.e., without the concentric change in LV geometry). A multiple linear regression analysis showed that PAC was one of the independent determinants of E/A in the overall subject group. These observations indicate that PAC is associated with the eccentric change in LV geometry in patients with treated essential hypertension and also suggest that the increase in PAC participates in the impairment of LV diastolic function apart from the concentric change in LV geometry, although concentric hypertrophy clearly impairs LV diastolic function.

Central mineralocorticoid receptor blockade improves volume regulation and reduces sympathetic drive in heart failure

The mineralocorticoid (MC) receptor antagonist spironolactone (SL) improves morbidity and mortality in patients with congestive heart failure (CHF). We tested the hypothesis that the central nervous system actions of SL contribute to its beneficial effects. SL (100 ng/h for 28 days) or ethanol vehicle (VEH) was administered intracerebroventricularly or intraperitoneally to rats with CHF induced by coronary artery ligation (CL) and to SHAM-operated controls. The intracerebroventricular SL treatment prevented the increase in sodium appetite and the decreases in sodium and water excretion observed within a week of CL in VEH-treated CHF rats. Intraperitoneal SL also improved volume regulation in the CHF rats, but only after 3 wk of treatment. Four weeks of SL treatment, either intracerebroventricularly or intraperitoneally, ameliorated both the increase in sympathetic drive and the impaired baroreflex function observed in VEH-treated CHF rats. These findings suggest that activation of MC receptors in the central nervous system plays a critical role in the altered volume regulation and augmented sympathetic drive that characterize clinical heart failure.

Polypharmacy of heart failure. Creating a rational pharmacotherapeutic protocol

In the management of chronic heart failure, polypharmacy is common, necessary, and often overlooked. The increasing costs of care, noncompliance, and frequent adverse drug interactions have led to diminishing benefits by simply adding additional drugs to the already complex regimen. This review outlines a rational pharmacotherapeutic protocol based on establishing overall therapeutic goals and confirming treatment targets, tailoring therapy to individual patients by balancing beneficial and adverse drug effects, and paying particular attention to patient education and other nonpharmacologic support.

[Chronic heart failure in children: recent contributions of physiopathology and therapeutic implications]

The treatment of chronic heart failure has made remarkable progress over the past ten years. Recent advances in our understanding of the pathophysiologic mechanisms involved in heart failure syndrome have led to changes in our approach to the treatment of children. The goals of the therapy have shifted from purely hemodynamic manipulation to a combination of hemodynamic and neurohumoral modulation. As for adults, three therapeutic classes have recently emerged: conversion enzyme inhibitors, spironolactone and beta-blockers. Pediatricians know that a child is not a small adult and we have to think about heart failure on the basis of etiology, the age of the patient, and circulatory physiology and maturation.

Aldosterone antagonists in the treatment of hypertension and target organ damage

Mineralocorticoids mediate a number of effects besides regulation of fluid and electrolyte balance. Recent evidence has revealed several nontraditional roles, sites of synthesis, and action for these steroids. Aldosterone, the principal mineralocorticoid in humans, appears to be synthesized in physiologically relevant amounts in both the heart and the vasculature, and plays an important role in vessel wall and myocardial remodeling. The genomic effects of aldosterone are mediated through activation of the classic mineralocorticoid receptor, whereas rapid nongenomic effects seem to involve a distinct receptor and result in activation of multiple downstream signaling pathways. Recently, several lines of evidence seem to suggest an important interaction between the nitric oxide and the aldosterone pathway in the adrenal gland and vasculature. The evolution of selective aldosterone receptor antagonists will help us understand the role that mineralocorticoids play in the pathogenesis of hypertension, heart failure, and atherosclerosis.

Neurohumoral regulation in ischemia-induced heart failure. Role of the forebrain

Congestive heart failure (CHF) is characterized by neurohumoral excitation. Increased sympathetic drive and activation of the reninangiotensin-aldosterone system (RAAS), with vasoconstriction and volume retention, are hallmarks of the CHF syndrome. Treatment strategies have targeted the peripheral influences of these two systems, but have not addressed the central mechanisms that drive them. We monitored the development of CHF following coronary ligation in adult Sprague-Dawley rats. Left ventricular dysfunction characteristic of CHF was confirmed by echocardiography, and the CHF syndrome was validated by measurements of circulating hormones, sodium appetite, thirst, renal sodium and water retention, and renal sympathetic nerve activity (RSNA). In CHF rats, neuronal activity in the hypothalamic paraventricular nucleus (PVN), which mediates downstream effects of forebrain circumventricular organs, was increased and was inhibited by blocking components of the RAAS at the forebrain level. Forebrain (AV3V) lesions and intracarotid (forebrain directed) injections of agents (captopril, losartan, spironolactone) that block RAAS substantially attenuated the behavioral and physiological manifestations of CHF. Intravenous losartan and captopril, in doses that lower arterial pressure, increased RSNA. These findings demonstrate an important role for RAAS-activated forebrain mechanisms in CHF and suggest that the central neural mechanisms driving sympathetic nerve activity and volume retention may persist and promote the progression of CHF despite treatments directed toward the peripheral influences of RAAS.

Aldosterone and the hypertensive kidney: its emerging role as a mediator of progressive renal dysfunction: a paradigm shift

End-stage renal disease (ESRD) comprises an enormous public health burden, with an increasing incidence and prevalence. Hypertension is a major risk factor for progressive renal disease. This escalating prevalence suggests that newer therapeutic interventions and strategies are needed to complement current antihypertensive approaches. Although much evidence demonstrates that angiotensin II mediates progressive renal disease, recent evidence also implicates aldosterone as an important pathogenetic factor in progressive renal disease. Several lines of experimental evidence demonstrate that selective blockade of aldosterone, independent of renin-angiotensin blockade, reduces proteinuria and nephrosclerosis in the spontaneously hypertensive stroke-prone rat model and reduces proteinuria and glomerulosclerosis in the subtotally nephrectomized rat model (i.e. remnant kidney). Whereas pharmacological blockade with angiotensin II receptor blockers and angiotensin-converting enzyme inhibitors reduces proteinuria and nephrosclerosis/ glomerulosclerosis, selective reinfusion of aldosterone restores these abnormalities despite continued renin-angiotensin blockade. Aldosterone may promote fibrosis by several mechanisms, including plasminogen activator inhibitor-1 expression and consequent alterations of vascular fibrinolysis, by stimulation of transforming growth factor-beta 1, and by stimulation of reactive oxygen species. Based on this theoretical construct, randomized clinical studies will be initiated to delineate the potential renal-protective effects of antihypertensive therapy utilizing aldosterone receptor blockade.

Aldosterone as a mediator of progressive renal disease: pathogenetic and clinical implications

End-stage renal disease is an enormous public health burden with an increasing incidence and prevalence. This escalating prevalence suggests that newer therapeutic interventions and strategies are needed to complement current antihypertensive approaches. Although much evidence shows that angiotensin II mediates progressive renal disease, recent evidence also implicates aldosterone as an important pathogenetic factor in progressive renal disease. Several lines of experimental evidence show that selective blockade of aldosterone, independent of renin-angiotensin blockade, reduces proteinuria and nephrosclerosis in the spontaneously hypertensive stroke-prone rat model and reduces proteinuria and glomerulosclerosis in the subtotally nephrectomized rat model (ie, remnant kidney). Although pharmacological blockade with angiotensin II-receptor blockers and angiotensin-converting enzyme inhibitors reduces proteinuria and nephrosclerosis and/or glomerulosclerosis, selective reinfusion of aldosterone restores these abnormalities despite continued renin-angiotensin blockade. Based on this theoretic construct, randomized clinical studies will be initiated to delineate the potential renal-protective effects of antihypertensive therapy using aldosterone-receptor blockade. This is a US government work. There are no restrictions on its use.

The combination ace-inhibitors plus canreonate in patients with anterior myocardial infarction: safety and tolerability study

BACKGROUND

There is recent evidence that aldosterone (ALDO) exerts pro-fibrotic effects, acting via the mineral-corticoid receptors in cardiovascular tissues and partial aldosterone escape during ACE-inhibition treatment occurs.

METHODS

A double blind randomised study was performed to evaluate the feasibility, and tolerability of the administration of the 25 mg/day of canreonate plus captopril versus captopril alone in patients with anterior AMI unsuitable for thrombolysis and/or not receiving thrombolytic treatment, and unreperfused after thrombolysis. Fifty five patients hospitalised for anterior AMI,with a serum creatinine concentration <2.0 mg/dl and a serum K concentration <5.0 mmol per liter were randomised in 2 groups: Group A included 27 patients who received captopril and 25 mg i.v. of canreonate (1 mg/h for the 1st 72 h and then orally 25 mg/day. Group B (28 patients) received captopril and placebo. Ten days after admission they underwent echocardiography to determine end systolic volume (ESV), ejection fraction (EF), End diastolic diameter EDD, E/A ratio, E deceleration time (dec. time) and isovolumetric relaxation time (IVRT), E and A peak velocities.

RESULTS

All patients did not show patency of the infarct related artery (7-10 days after AMI) and the 2 groups were similar in regard to age, sex, diabetes, smoking habits, hypertension, CK enzymatic peak, adjuvant therapy, EF, ESV, and incidence of CABG/PTCA. One patient only showed increase of serum K>5.5 mmol/dl and creatinine >2.0 mg per liter after 10 days of treatment (group A). The mitral E/A ratio was higher in group A than group B (0.85+/-0.18 and 0.75+/-0.14) respectively, P=0.024. Creatinine, blood urea and serum K did not show significant differences between groups. No side effects were observed during the study period. The incidence of vessel diseases was similar in both groups.

CONCLUSIONS

Our data suggest that the combination of captopril plus canreonate in feasible in early treatment of AMI patients.

New drugs in the treatment of heart failure

New therapeutic strategies as well as the development of drugs with more specific targets have been fueled by disappointments in the treatment of adult heart failure. Calcium sensitizers, vesnarinone and angiotensin channel blockers will be addressed in this manuscript. The physiologic and pharmacologic principles that justify their use in the management of heart failure are reviewed. Calcium sensitizers increase myocardial contractility and in part they bypass the adenylyl cyclase cascade, which gives them a more favorable energy profile. Vesnarinone is a quinolinone derivative with ion channel modulation properties, which result in a positive inotropic effect and prolongation of the action potential. In addition vesnarinone has immunomodulatory properties. Angiotensin-converting enzyme inhibitors are the cornerstones for the treatment of heart failure. The discovery of some putative drawbacks to ACE inhibition has challenged this supremacy. Angiotensin receptor blockers have been developed hoping to overcome these deficiencies. Myocardial developmental differences highlight the shortcomings of attempting to extrapolate data on drugs and cellular physiology in adults to children. Studies are needed addressing standards of care, quality of life, morbidity and mortality, neurohumoral activation, its modulation and the consequences of these therapies in pediatric heart failure.

Pathophysiology of pediatric heart failure

Our understanding of the syndrome of heart failure has undergone several revisions, most importantly in the second half of the 20th century. New insights into the mechanisms of diseases offer new, challenging, controversial and sometimes counterintuitive forms of therapy. The development and progression of heart failure results from a complex interplay of hemodynamic and neurohormonal, cellular and genetic factors, rather than simply changes in cardiac function. It is because of this reason that our therapeutic focus can no longer be solely based on supply and demand models. Since the description of the pulsatile nature of the heart function and the flow of blood around a circuit by W. Harvey, numerous new paradigms have been put forward to explain the nature of heart failure. However, no single new model thus far proposed has been able to displace previous ones and successfully dictate therapy. It is the purpose of this manuscript to review the overall current understanding of the heart failure syndrome and how these new ideas may affect our therapeutic approach.

Overview of the management of pediatric heart failure

For the most part of this the century heart failure syndrome was understood as a pump failure disorder with hemodynamic consequences stemming from the same myocardial dysfunction. In addition supply and demand theories were used to explain the nature of symptoms. As a result, therapeutic strategies were directed at correcting the abnormal hemodynamic conditions and normalizing the delivery of the much needed nutrients. Improvement of cardiac pump function with inotropic drugs and abnormal circulatory conditions with afterload and preload modifications became therapeutic goals and standards of care. However, while vasodilators and inotropic drugs immediately improved symptoms, hemodynamics and functional status, in the long term they either did not affect or worsen the natural history of heart failure. In pediatrics, this is further complicated by the lack of large scale trials addressing issues pertinent to the particularities that affect heart failure in children. In the late 1980s and 1990s heart failure has evolved into a more complex, multiple and interactive pathophysiologic disorder. Today not only the abnormal hemodynamics but also the biological disorders are pharmacologic targets. The reversal or slowing of myocardial maladaptation has become one of the most important therapeutic goals. With this end in mind therapeutic strategies may seem counterintuitive and paradoxical, such as the use of beta-blockers. This review will address the current thinking and therapeutic modalities used today in the treatment of heart failure syndrome in the adult population. We also discuss some of the issues why we think that these principles can be extrapolated to the pediatric population.

Aldosterone, a new appreciation of its role in heart failure

Understanding of the role, triggers, and impact of the renin-angiotensin-aldosterone system in cardiovascular disease has significantly broadened. In recent years substantial discoveries have been made regarding the pathophysiology of heart failure, particularly in the area of neurohormonal activation. New interest in therapy with aldosterone antagonists was stimulated by results of a 2-year study of 1663 patients with heart failure that showed a 30% relative risk reduction of death among patients given a subhemodynamic dosage of spironolactone, a nonselective aldosterone antagonist, compared with placebo, in addition to standard therapy of diuretics, angiotensin-converting enzyme inhibitors, beta-blockers, and digitalis.

Dissociation between ACE activity and autonomic response to ACE inhibition in patients with heart failure

BACKGROUND

Administration of angiotensin-converting enzyme (ACE) inhibitors to patients with congestive heart failure has been shown to increase parasympathetic tone as indicated by increases in high-frequency heart rate variability. The mechanism for this effect, including its relation to changes in baroreflex activity, blood pressure variability, and suppression of ACE activity, remains undefined. This study was designed to test the relation of these variables, which may govern changes in autonomic activity, to the previously described increase in parasympathetic tone.

METHODS

Seven patients with heart failure received a 3-hour infusion of the ACE inhibitor enalaprilat. Hemodynamic variables and parameters of heart rate and blood pressure variability, baroreflex gain derived from the interaction of heart rate and blood pressure variability, and serum ACE activity were measured during and after the infusion. Measures of heart rate and blood pressure variability were also compared against a historic control group.

RESULTS

Serum ACE activity was significantly suppressed throughout and after enalaprilat infusion. Hemodynamic measures did not change other than a small decline in right atrial and pulmonary capillary wedge pressures. Parasympathetic tone showed an initial significant increase with a peak at 2 hours but then declined below baseline 8 hours after initiation of enalaprilat infusion. Sympathetically influenced low-frequency heart rate variability was significantly increased above baseline in the enalaprilat treatment group 8 hours after initiation of the infusion. Baroreflex gain showed a significant trend to an increase with the maximum value coinciding with the peak in parasympathetic tone. There was no change in blood pressure variability in the enalaprilat group and no change in baroreflex gain, heart rate variability, or blood pressure variability in the control group.

CONCLUSIONS

Parasympathetic tone and baroreflex gain increased with parenteral administration of an ACE inhibitor but subsequently decreased below baseline values despite continued suppression of serum ACE activity. The dissociation between ACE suppression and autonomic response to ACE inhibition indicates that enzyme systems not reflected by plasma ACE activity or independent from the classic pathways of angiotensin formation contribute to the regulation of the autonomic response to ACE inhibition in patients with heart failure. The absence of significant change in hemodynamic variables or in blood pressure variability indicates that these autonomic changes are not an indirect reflex response to ACE inhibitor-induced vasodilation or hemodynamic baroreceptor stimulation.

Synergistic effect of adrenal steroids and angiotensin II on plasminogen activator inhibitor-1 production

Recent data suggest an interaction between the renin-angiotensin-aldosterone system and fibrinolysis. Although previous work has focused on the effect of angiotensin II (Ang II) on plasminogen activator inhibitor (PAI-1) expression, the present study tests the hypothesis that aldosterone contributes to the regulation of PAI-1 expression. To test this hypothesis in vitro, luciferase reporter constructs containing the human PAI-1 promoter were transfected into rat aortic smooth muscle cells. Exposure of the cells to 100 nmol/L Ang II resulted in a 3-fold increase in luciferase activity. Neither 1 micromol/L dexamethasone nor 1 micromol/L aldosterone alone increased PAI-1 expression. However, both dexamethasone and aldosterone enhanced the effect of Ang II in a dose-dependent manner. This effect was abolished by mutation in the region of a putative glucocorticoid-responsive element. A similar interactive effect of Ang II and aldosterone was observed in cultured human umbilical vein endothelial cells. The time course of the effect of aldosterone on Ang II-induced PAI-1 expression was consistent with a classical mineralocorticoid receptor mechanism, and the effect of aldosterone on PAI-1 synthesis was attenuated by spironolactone. To determine whether aldosterone affected PAI-1 expression in vivo, we measured local venous PAI-1 antigen concentrations in six patients with primary hyperaldosteronism undergoing selective adrenal vein sampling. PAI-1 antigen, but not tissue plasminogen activator antigen, concentrations were significantly higher in adrenal venous blood than in peripheral venous blood. Taken together, these data support the hypothesis that aldosterone modulates the effect of Ang II on PAI-1 expression in vitro and in vivo in humans.

Within-patient comparison of effects of different dosages of enalapril on functional capacity and neurohormone levels in patients with chronic heart failure

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibitors are established as first-line therapy in chronic heart failure (CHF). However, conflicting results exist regarding the dose-effect relation of ACE inhibitors.

METHODS

We investigated 45 patients (age 55 +/- 10 years) with stable CHF who presented with a maintenance dosage of enalapril of either 5 mg given twice daily (E10; n = 16), 10 mg given twice daily (E20; n = 18), or 20 mg given twice daily (E40; n = 11). This dosage was changed 3 times to treat all patients with lower, higher, and the initial dosages for 4 weeks each. Neurohormones (atrial natriuretic peptide [ANP], brain natriuretic peptide [BNP], and norepinephrine) and enalaprilat trough levels were measured, and ergospirometry was performed.

RESULTS

Changes in enalapril dose and enalaprilat level were concordant in 82% of patients, indicating good compliance. After augmentation of enalapril to 40 mg daily, patients in the E10 group showed an increase in maximal oxygen consumption and a decrease in neurohormonal stimulation, whereas the opposite changes were observed after reduction of enalapril to 10 mg daily in patients in the E20 and E40 groups (maximal oxygen consumption: Delta1.1 +/- 2.0 vs -1.0 +/- 1.9 mL. kg(-1). min(-1), P <.01; ANP: Delta-63 +/- 106 vs 19 +/- 54 pg/mL, P <.01; BNP: Delta-62 +/- 104 vs 18 +/- 89 pg/mL, P <.05; norepinephrine: Delta-1.3 +/- 2.9 vs 0.6 +/- 1.8, P <.05). Within-patient comparison showed that neurohormone levels were higher and exercise capacity lower while patients were receiving 10 mg of enalapril per day than when they were receiving 40 mg per day (ANP: 172 +/- 148 vs 139 +/- 122 pg/mL, P <.01; BNP: 193 +/- 244 vs 152 +/- 225 pg/mL, P <.005; norepinephrine: 4.2 +/- 2.2 vs 3.5 +/- 1. 6 nmol/L, P <.05; maximal oxygen consumption 22.0 +/- 4.4 vs 21.3 +/- 4.3 mL. kg(-1). min(-1) P <.05). Similar differences were observed when comparing these variables, and patients had lowest and highest enalaprilat trough levels.

CONCLUSIONS

High doses of enalapril resulted in an improvement of exercise capacity and reduction of neurohumoral stimulation, whereas these parameters worsened after reduction of enalapril dose. Thus patients with congestive heart failure may benefit from increasing dosage of ACE inhibitors.

The effect of spironolactone on morbidity and mortality in patients with severe heart failure. Randomized Aldactone Evaluation Study Investigators

BACKGROUND AND METHODS

Aldosterone is important in the pathophysiology of heart failure. In a doubleblind study, we enrolled 1663 patients who had severe heart failure and a left ventricular ejection fraction of no more than 35 percent and who were being treated with an angiotensin-converting-enzyme inhibitor, a loop diuretic, and in most cases digoxin. A total of 822 patients were randomly assigned to receive 25 mg of spironolactone daily, and 841 to receive placebo. The primary end point was death from all causes.

RESULTS

The trial was discontinued early, after a mean follow-up period of 24 months, because an interim analysis determined that spironolactone was efficacious. There were 386 deaths in the placebo group (46 percent) and 284 in the spironolactone group (35 percent; relative risk of death, 0.70; 95 percent confidence interval, 0.60 to 0.82; P<0.001). This 30 percent reduction in the risk of death among patients in the spironolactone group was attributed to a lower risk of both death from progressive heart failure and sudden death from cardiac causes. The frequency of hospitalization for worsening heart failure was 35 percent lower in the spironolactone group than in the placebo group (relative risk of hospitalization, 0.65; 95 percent confidence interval, 0.54 to 0.77; P<0.001). In addition, patients who received spironolactone had a significant improvement in the symptoms of heart failure, as assessed on the basis of the New York Heart Association functional class (P<0.001). Gynecomastia or breast pain was reported in 10 percent of men who were treated with spironolactone, as compared with 1 percent of men in the placebo group (P<0.001). The incidence of serious hyperkalemia was minimal in both groups of patients.

CONCLUSIONS

Blockade of aldosterone receptors by spironolactone, in addition to standard therapy, substantially reduces the risk of both morbidity and death among patients with severe heart failure.

Anaesthesia for Conn's syndrome

We describe the peri-operative management of two patients undergoing bilateral adrenalectomy for Conn's syndrome; one using an open surgical approach and the other a laparoscopic technique. The first patient, aged 64 years, died of a myocardial infarction 5 days postoperatively; the second, aged 29 years, had an uneventful recovery. The pre-operative preparation, peroperative management and postoperative care of these patients are detailed, and the pathophysiology and clinical management of Conn's syndrome are reviewed.

Recent insight into therapy of congestive heart failure: focus on ACE inhibition and angiotensin-II antagonism

One possible intervention to interrupt the deleterious effects of the renin-angiotensin system is suppression of angiotensin II (Ang II) formation by inhibition of angiotensin-converting enzyme (ACE). However, ACE inhibition incompletely suppresses Ang II formation and also leads to accumulation of bradykinin. Angiotensin II type 1 (AT1) receptors are believed to promote the known deleterious effects of Ang II. Therefore, AT1 receptor antagonists have been recently introduced into therapy for hypertension and congestive heart failure (CHF). Although there are significant differences between the effects of AT1 receptor antagonists and ACE inhibitors including the unopposed stimulation of angiotensin II type 2 (AT2) receptors by AT1 receptor antagonists, the discussion of whether ACE inhibitors, AT1 receptor antagonists or the combination of both are superior in the pharmacotherapy of CHF is still largely theoretical. Accordingly, AT1 receptor antagonists are still investigational. Angiotensin-converting enzyme inhibitors remain first line therapy in patients with CHF due to systolic dysfunction. However, in patients not able to tolerate ACE inhibitor induced side effects, in particular cough, AT1 receptor antagonism is a good alternative. In clinical practice, emphasis should be placed on increasing the utilization of ACE inhibitors, as more than 50% of patients with CHF do not receive ACE inhibitors. In addition, the majority of those on ACE inhibitors receive doses lower than the dosage used in the large clinical trials. Although not yet completely proved, it is likely that high doses of ACE inhibition are superior to low doses with respect to prognosis and symptoms.

Effects of acute ACE inhibition on pulsatile renin and aldosterone secretion and their synchrony

Pulsatile (burstlike) secretion of renin and aldosterone is positively coupled with a short time lag of about 10 to 20 minutes. We investigated how acute interruption of the renin-angiotensin-aldosterone axis, ie, acute angiotensin-converting enzyme (ACE) inhibition, alters the pattern of renin and aldosterone secretion. Eight healthy men (mean age, 22+/-1 years) were studied while on standardized salt intake. They were allocated on 2 occasions in random order to injection of placebo or 1.25 mg of the ACE inhibitor enalaprilat. Blood samples were obtained every 10 minutes for 24 hours for measurement of plasma renin and aldosterone concentrations. The hormone concentration profiles were analyzed using a multiparameter deconvolution technique; basal (tonic) and pulsatile hormone secretion was assessed. The regularity of pulsatile hormone secretion was analyzed using approximate entropy (ApEn). Cross-correlation and cross-ApEn analysis of renin and aldosterone secretion were performed to assess synchrony. Acute ACE inhibition caused an immediate burst of renin release and, in addition, significantly (P<0.01) increased 24-hour pulsatile and total renin secretion. It did not affect basal (nonpulsatile) renin secretion. The amplitude of renin bursts and the mass of hormone secreted per burst were significantly (P<0.01) increased, whereas the burst frequency (ie, number of secretory events) was unchanged. ApEn analysis revealed significantly (P<0.05) more regular renin secretion after ACE inhibition. In contrast, neither basal nor pulsatile aldosterone secretion was affected by administration of enalaprilat. Cross-ApEn analysis documented not only a maintained pattern of reproducibility (ie, synchrony) but also greater conditional regularity between pulsatile renin and aldosterone secretions with acute ACE inhibition. However, the quantitative strength of hormone coupling (assessed by cross-correlation analysis) was markedly diminished by enalaprilat treatment. The present findings suggest that the renin-angiotensin-aldosterone axis may not be completely uncoupled by acute ACE inhibition or that pulsatile renin and aldosterone secretion is driven by a common signal generator that is unaffected by ACE inhibition. In addition, a background basal and pulsatile aldosterone secretion not regulated by the renin-angiotensin axis may exist.

Differential effects of antihypertensive drugs on neurohormonal activation: insights from a population-based sample

OBJECTIVES

The clinical course of hypertension or heart failure may be modified by the extent of concurrent neurohormonal activation. Factors that regulate neurohormones in patients with these conditions are complex. In the present study, we examined the relative contribution of antihypertensive therapy to the variability of neurohormonal levels in a well defined population based sample.

DESIGN AND SETTING

Cross-sectional study of a mixed urban and rural population.

SUBJECTS

Middle-aged individuals (n = 646) were analysed in order to elucidate determinants of neurohormone levels by uni- and multivariate comparisons. The assessment included anthropometric, echocardiographic and, if appropriate, genotype information.

RESULTS

The intake of antihypertensive drugs was related to significant alterations of neurohormone levels that, in part, exceeded the contribution of all other variables studied. Multivariate analyses revealed that renin levels were independently related to the intake of beta blockers (n = 80; -8.4 mU L-1; P = 0.001), angiotensin-converting enzyme (ACE)-inhibitors (n = 39; +15.9 mU L-1; P = 0.0001), diuretics (n = 62; +14.3 mU L-1; P = 0.0001), and calcium channel blockers (n = 45; +5.9 mU L-1; P = 0.05). Aldosterone levels were related to ACE-inhibition (-156.5 pmol L-1; P = 0.04) and diuretic treatment (+422.4 pmol L-1; P = 0.0001) in an opposite fashion whereas beta blockers and calcium channel blockers had no significant independent effects. The levels of the atrial natriuretic peptide were significantly related to the use of beta blockers (+3.9 pmol L-1; P = 0.002) and calcium channel blockers (+3.1 pmol L-1; P = 0.05). Finally, serum angiotensinogen levels and ACE activity were not found to be significantly affected by antihypertensive medication but were rather related to gender or genotype.

CONCLUSIONS

The data emphasize that antihypertensive treatment with different classes of drugs may modulate serum levels of neurohormones substantially resulting in distinct patterns of activation. These drug-related effects may require consideration when neurohormonal activation is of functional relevance or when neurohormones serve as prognostic predictors in patients with cardiovascular disorders.

Effects of spironolactone on exercise capacity and neurohormonal factors in patients with heart failure treated with loop diuretics and angiotensin-converting enzyme inhibitor

1. Treatment with spironolactone is reported to be useful when combined with loop diuretics and an angiotensin-converting enzyme (ACE) inhibitor in severe congestive heart failure (CHF). However, the effects of the addition of spironolactone on exercise capacity and neurohormonal variables have not been demonstrated. This study determined the effects of additive spironolactone on exercise capacity and neurohormonal factors in patients with mild CHF. 2. Oxygen uptake (VO2), plasma norepinephrine (NE), renin activity (PRA), angiotensin II (AII), aldosterone (ALD), and atrial natriuretic peptide (ANP) were measured at rest and after peak exercise in nine patients with CHF (six idiopathic and three ischemic cardiomyopathy; New York Heart Association (NYHA) classes II and III) who were already taking furosemide (mean 29 +/- 5 mg/day) and enalapril (mean 4.7 +/- 0.8 mg/day). Studies were repeated after 16 weeks of treatment with additive single daily dose of 25 mg of spironolactone. In four of nine patients, the exercise test was repeated after a 4-weeks washout of spironolactone. 3. Treatment with spironolactone caused natriuresis, decreased cardiothoracic ratio in chest X-ray (before vs. after treatment: 53.7 +/- 1.2 vs. 50.7 +/- 1.4%, P < 0.01), and improved NYHA functional class. Peak VO2 (17.1 +/- 1.6 vs. 17.5 +/- 2.2 ml/min/kg, NS) and heart rate and blood pressure responses to exercise were not altered. Resting NE (215 +/- 41 vs. 492 +/- 85 pg/ml, P < 0.01) and resting PRA (8.2 +/- 2.3 vs. 16.2 +/- 4.1 ng/ml/hr, P < 0.01) as well as peak NE (1618 +/- 313 vs. 2712 +/- 374 pg/ml, P < 0.01) and peak PRA (12.8 +/- 3.2 vs. 28.1 +/- 11.8 ng/ml/hr, P = 0.17) were augmented after additive spironolactone. ALD and AII were insignificantly increased, and ANP was insignificantly decreased at peak exercise after spironolactone treatment. Spironolactone washout was associated with a trend of the neurohormones to return toward pretreatment values. 4. In conclusion, chronic additive treatment with spironolactone was associated with neurohormonal activation both at rest and during exercise without changing the exercise capacity of patients with mild CHF who were already on loop diuretics and ACE inhibitor therapy.

Modulation of the renin-angiotensin pathway through enzyme inhibition and specific receptor blockade in pacing-induced heart failure: I. Effects on left ventricular performance and neurohormonal systems

BACKGROUND

The goal of this study was to determine the effects of ACE inhibition (ACEI) alone, AT1 angiotensin (Ang) II receptor blockade alone, and combined ACEI and AT1 Ang II receptor blockade on LV function, systemic hemodynamics, and neurohormonal system activity in a model of congestive heart failure (CHF).

METHODS AND RESULTS

Pigs were randomly assigned to each of 5 groups: (1) rapid atrial pacing (240 bpm) for 3 weeks (n=9), (2) ACEI (benazeprilat, 0.187 mg x kg(-1) x d(-1)) and rapid pacing (n=9), (3) AT1 Ang II receptor blockade (valsartan, 3 mg x kg(-1) x d(-1)) and rapid pacing (n=9), (4) ACEI and AT1 Ang II receptor blockade (benazeprilat/valsartan, 0.05/3 mg x kg(-1) d(-1)) and rapid pacing (n=9), and (5) sham controls (n=10). In the pacing group, LV fractional shortening (LVFS) fell (13.4+/-1.4% versus 39.1+/-1.0%) and end-diastolic dimension (LVEDD) increased (5.61+/-0.11 versus 3.45+/-0.07 cm) compared with control (P<.05). With AT1 Ang II blockade and rapid pacing, LVEDD and LVFS were unchanged from pacing-only values. ACEI reduced LVEDD (4.95+/-0.11 cm) and increased LVFS (20.9+/-1.9%) from pacing-only values (P<.05). ACEI and AT1 Ang II blockade reduced LVEDD (4.68+/-0.07 cm) and increased LVFS (25.2+/-0.9%) from pacing only (P<.05). Plasma norepinephrine and endothelin increased by more than fivefold with chronic pacing and remained elevated with AT1 Ang II blockade. Plasma norepinephrine was reduced from pacing-only values by more than twofold in the ACEI group and the combination group. ACEI and AT1 Ang II receptor blockade reduced plasma endothelin levels by >50% from rapid-pacing values.

CONCLUSIONS

These findings suggest that the effects of ACEI in the setting of CHF are not solely due to modulation of Ang II levels but rather to alternative enzymatic pathways and that combined ACEI and AT1 Ang II receptor blockade may provide unique benefits for LV pump function and neurohormonal systems in the setting of CHF.

Role of aldosterone in the remnant kidney model in the rat

The renin-angiotensin-aldosterone system (RAAS) participates in the injury sustained by the remnant kidney. Our studies assessed the importance of aldosterone in that model and the response of aldosterone to drugs interfering with the RAAS. Initially, four groups of rats were studied: SHAM-operated rats, untreated remnant rats (REM), REM rats treated with losartan and enalapril (REM AIIA), and REM AIIA rats infused with exogenous aldosterone (REM AIIA + ALDO). The last group was maintained with aldosterone levels comparable to those in untreated REM rats by constant infusion of exogenous aldosterone. REM rats had larger adrenal glands and a > 10-fold elevation in plasma aldosterone compared to SHAM. REM AIIA rats demonstrated significant suppression of the hyperaldosteronism as well as marked attenuation of proteinuria, hypertension, and glomerulosclerosis compared to REM. REM AIIA + ALDO rats manifested greater proteinuria, hypertension, and glomerulosclerosis than REM AIIA rats. Indeed, by 4 wk of observation all of these features of the experimental disease were similar in magnitude in REM AIIA + ALDO and untreated REM. In separate REM rats spironolactone administration did not reduce glomerular sclerosis but did transiently reduce proteinuria, lowered arterial pressure, and lessened cardiac hypertrophy. In summary, aldosterone contributes to hypertension and renal injury in the remnant kidney model.

Aldosterone escape during angiotensin-converting enzyme inhibitor therapy in chronic heart failure

In chronic heart failure, angiotensin-converting enzyme inhibitors produce an acute decrease in aldosterone levels. Long-term angiotensin-converting enzyme inhibition is, however, associated with aldosterone suppression that is weak, variable, and unsustained (ie, aldosterone escapes). The possible harmful effects of this residual aldosterone are multiple Magnesium loss caused by aldosterone and by diuretics could contribute to coronary artery spasm and arrhythmias. Aldosterone blocks norepinephrine uptake by the myocardium; extracellular catecholamines may, therefore, lead to arrhythmias and ischemia. Aldosterone has been shown to have an acute arrhythmogenic effect as well as a detrimental effect on parasympathetic and baroreflex function. Both angiotensin II and aldosterone stimulate myocardial fibrosis, which may lead to a higher incidence of malignant ventricular arrhythmias. Spironolactone therapy added to the regimen of an angiotensin-converting enzyme inhibitor and diuretic has been shown to cause natriuresis, magnesium retention, increased myocardial norepinephrine uptake, and reduced incidence of ventricular arrhythmias. It may well be that residual aldosterone mediates many harmful effects in chronic heart failure and that to optimize the benefit of blocking the renin-angiotensin-aldosterone system may require specific blockade of residual aldosterone as well as traditional angiotensin-converting enzyme inhibition.