Effect of spironolactone on ventricular arrhythmias in congestive heart failure secondary to idiopathic dilated or to ischemic cardiomyopathy

Changes in heart failure medications in patients hospitalised and discharged

BACKGROUND

To date, evidence-based recommendations help doctors to manage patients with heart failure (HF). However, the implementation of these recommendations in primary care is still problematic as beneficial drugs are infrequently prescribed. The aim of the study was to determine whether admission to hospital increases usage of beneficial HF medication and if this usage is maintained directly after discharge.

METHODS

The study was conducted from November 2002 until January 2004. In 77 patients hospitalised with heart failure (HF), the medication prescribed by the referring general practitioner (GP) and drug treatment directed by the hospital physicians was documented. Information regarding the post-discharge (14 d) therapy by the GP was evaluated via a telephone interview. Ejection fraction values, comorbidity and specifics regarding diagnostic or therapeutic intervention were collected by chart review.

RESULTS

When compared to the referring GPs, hospital physicians prescribed more ACE-inhibitors (58.4% vs. 76.6%; p = 0.001) and beta-blockers of proven efficacy in HF (metoprolol, bisoprolol, carvedilol; 58.4% vs. 81.8%). Aldosterone antagonists were also administered more frequently in the hospital setting compared to general practice (14.3% vs. 37.7%). The New York Heart Association classification for heart failure did not influence whether aldosterone antagonists were administered either in primary or secondary care. Fourteen days after discharge, there was no significant discontinuity in discharge medication.

CONCLUSION

Patients suffering from HF were more likely to receive beneficial medication in hospital than prior to admission. The treatment regime then remained stable two weeks after discharge. We suggest that findings on drug continuation in different cardiovascular patients might be considered validated for patients with HF.

Spironolactone treatment and clinical outcomes in patients with systolic dysfunction and mild heart failure symptoms: a retrospective analysis

BACKGROUND

The effect of spironolactone on clinical outcomes in patients with mild heart failure is unclear.

METHODS AND RESULTS

We performed a retrospective analysis of 482 consecutive patients with left ventricular ejection fraction < or =40% and New York Heart Association I-II symptoms. Major cardiac event (MCE) was defined as death, left ventricular assist device implantation, or United Network of Organ Sharing 1 cardiac transplantation. Proportional hazards analysis was used to determine predictors of MCE and to derive an adjusted hazard for spironolactone therapy. Spironolactone was prescribed to 279 (58%) patients and mean follow-up was 1029 days. After controlling for predictors of clinical events, spironolactone treatment was associated with a trend for lower risk of MCE or heart failure rehospitalization (HR, 0.68; 95% CI, 0.43-1.07; P = .095). Exploration of interaction terms between medications revealed that treatment with the combination of spironolactone and thiazide diuretics was associated with lower risk of clinical events (HR, 0.32; 95% CI, 0.12-0.89; P = .029).

CONCLUSION

In subjects with mild heart failure treated with a thiazide diuretic, the use of spironolactone is associated with reduced risk of MCE or heart failure rehospitalization. A randomized controlled trial is necessary to accurately define the clinical effects of spironolactone in patients with mild heart failure.

Use and side-effect profile of spironolactone in a private cardiologist's practice

BACKGROUND

The beneficial effects of spironolactone on the treatment of cardiovascular diseases are well known, but translating these benefits into private practice can be difficult because of the drug's side-effect profile.

HYPOTHESIS

When patients are monitored over the long term, spironolactone can be used safely with an acceptable side-effect profile.

METHODS

We retrospectively studied 762 patients taking spironolactone over a 7-year period in a cardiologist's referral-based practice and monitored them for side effects from the medication.

RESULTS

Data were available on 762 patients. The average age of our patients when started on the medication was 67.2 +/- 0.5 years. Of these, 585 (76.8%) patients were treated for heart failure and 155 (20.3%) for hypertension. An average dose of 38.4 +/- 1.4 mg of spironolactone was used for treatment of all conditions. Of the 762 patients, 81 (10.6%) experienced side effects while using the medication; 40 had hyperkalemia (5.3%), 14 had gynecomastia (1.8%), and 15 had gastritis (2%). Of the patients with hyperkalemia, average creatinine clearance decreased from 64.6 +/- 5.8 ml/min at therapy start to 50.3 +/- 5.5 ml/min at the time of onset of side effects.

CONCLUSION

Spironolactone can be used with an acceptable side-effect profile as long as patients are monitored long-term while receiving the medication.

Neurohormones and heart failure: the importance of aldosterone

Heart failure is a major cause of cardiovascular morbidity and mortality and its incidence is on the increase. The pathophysiology of heart failure is multi-factorial but recent studies suggest that aldosterone plays an important and independent role in its progression. Emerging evidence now suggests that aldosterone exerts renal-independent effects. It binds to its mineralocorticoid receptor to produce direct effects on the myocardium and vasculature, leading to damaging processes such as hypertrophy, necrosis, fibrosis and endothelial dysfunction, factors known to contribute to the pathophysiology of heart failure. Mineralocorticoid receptor antagonists have thus emerged as a new paradigm for the treatment of heart failure. The benefits of these agents on both morbidity and mortality when used in patients with chronic symptomatic heart failure have been demonstrated by recent trials.

Aldosterone Antagonism Improves Endothelial-Dependent Vasorelaxation in Heart Failure via Upregulation of Endothelial Nitric Oxide Synthase Production

BACKGROUND

Altering the renin-angiotensin aldosterone system improve mortality in heart failure (HF) in part through an improvement in nitric oxide (NO)-mediated endothelial function. This study examined if spironolactone affects endothelial nitric oxide synthase (eNOS) and NO-mediated vasorelaxation in HF.

METHODS AND RESULTS

Rats with HF after coronary artery ligation were treated with spironolactone for 4 weeks. Rats with HF had a decrease (P < .05) in left ventricular (LV) systolic pressure (130 +/- 7 versus 118 +/- 6 mm Hg) and LV pressure with respect to time (9,122 +/- 876 versus 4,500 +/- 1971 mm Hg/second) with an increase in LV end-diastolic pressure (4 +/- 2 versus 23 +/- 8 mm Hg). Spironolactone did not affect hemodynamics but it improved (P < .05) endothelial-dependent vasorelaxation at more than 10(-8) M acetylcholine that was abolished with N(G)-monomethyl-L-arginine. The eNOS levels were decreased (P < .05) in the LV and the aorta; spironolactone restored LV and aortic eNOs levels to normal.

CONCLUSION

Spironolactone prevents the decrease in eNOS in the LV and aorta and improves NO-dependent vasorelaxation, suggesting that one potential mechanism of spironolactone is an improvement in vasoreactivity mediated though an increase in NO.

Aldosterone antagonists in the treatment of heart failure

PURPOSE

The clinical benefits, adverse effects, pharmacokinetics, and recommendations for the appropriate use of the aldosterone antagonists spironolactone and eplerenone in patients with heart failure are reviewed.

SUMMARY

Heart failure is a clinical syndrome characterized by the functional inability of the ventricle to meet the metabolic demands of the body. Renal hypoperfusion occurs as a result of reduced cardiac output, resulting in the activation of the renin-angiotensin-aldosterone system, which compensates for the hypoperfusion. However, this contributes to the pathology of the disease by, among other actions, increasing the release of aldosterone. Aldosterone has been shown to cause coronary inflammation, cardiac hypertrophy, myocardial fibrosis, ventricular arrhythmias, and ischemic and necrotic lesions. There are currently two aldosterone antagonists commercially available in the United States, spironolactone and eplerenone. Spironolactone is a nonselective aldosterone antagonist, and eplerenone is selective to the aldosterone receptor. Although numerous clinical trials have evaluated the efficacy of each drug, no studies have directly compared spironolactone and eplerenone. Both have been shown to improve morbidity and mortality in patients with advanced heart failure. Adverse effects of both spironolactone and eplerenone include potentially life-threatening hyperkalemia, which can be induced by renal insufficiency, diabetes mellitus, advanced heart failure, advanced age, and concurrent drug therapy.

CONCLUSION

Spironolactone and eplerenone are life-saving agents in patients with advanced heart failure and may benefit patients with mild heart failure. Potassium and renal function must be routinely assessed to minimize the risk of life-threatening hyperkalemia.

The pharmacological treatment of primary aldosteronism

Aldosterone is increasingly considered to have a fundamental role in the pathophysiology of cardiovascular disease. Primary aldosteronism is a much more common cause of secondary hypertension than once suspected, accounting for approximately 10% of cases. Screening for primary aldosteronism should be considered even in the presence of normokalaemia. The non-classical effects of aldosterone, some of which are transcription-independent, may be of similar or greater importance than its traditional effects on the kidney. Treatment of primary aldosteronism should be specific and aim to ameliorate all hormone-related effects of aldosterone, not just the most obvious manifestation of hypertension. Mineralocorticoid antagonism, shown to lead to significant additional survival advantage in heart failure, offers the best prospect for achieving therapeutic goals. For the increasing proportion of patients with primary aldosteronism suitable for long-term medical treatment, mineralocorticoid receptor blockade (better tolerated with eplerenone) should be considered the most appropriate choice of treatment, pending the development of better alternatives.

Impact of β-Blocker Dosage Changes during Heart Failure Exacerbation

Background:

Although β-blockers are important life-saving medications in heart failure patients, studies evaluating β-blocker dosing in decompensated heart failure are limited.

Objective:

To determine the clinical outcomes in patients with severe decompensated heart failure receiving the same dose of β-blockers as well as those whose outpatient regimen was altered.

Methods:

A retrospective chart analysis was conducted in patients with severe decompensated heart failure receiving chronic β-blocker therapy who were admitted to the hospital for decompensated heart failure. Of 245 patients identified, 76 were included in the study: same dose (n = 26), decreased dose (n = 19), discontinued dose (n = 21), or increased dose (n = 10). χ2 Analysis for K-independent samples evaluated the incidence of proarrhythmic events, mortality, and the number of recurrent hospitalizations after the index admission. Stepwise forward linear regression analysis determined the variables correlated with morbidity and mortality in these patients.

Results:

New arrhythmias during hospital admission occurred in 19 (25%) patients. The discontinued dose group had the most proarrhythmic events (47.6%; n = 10) and the most deaths (50%) in 6 months. Arrhythmias developed 1.8 and 3 days following β-blocker discontinuation or dosage reduction, respectively.

Conclusions:

Patients who remained on their outpatient β-blocker dose upon admission for decompensated heart failure had better clinical outcomes than others whose β-blocker dose was changed. A prospective, randomized, controlled clinical trial is warranted to further explore the implications of this drug–disease state interaction.

A look between the cardiomyocytes: the extracellular matrix in heart failure

The extracellular matrix (ECM) of the heart dynamically interacts with various cellular components of the myocardium, including the myocytes and connective tissue cells. With the development and progression of heart failure, left ventricular (LV) myocardial remodeling occurs. The progression of LV remodeling is accompanied by alterations in the structure and function of the ECM that occur after injury resulting from neurohormonal activation, changes in LV loading conditions, and alterations in myocardial perfusion and metabolism and is secondary to a host of nonmyocyte signaling pathways that affect repair and remodeling of the myocardium as a whole. This article attempts to review some of these processes and their interactions and to provide a focus to the often overlooked contribution of the ECM to the development and progression of heart failure and thereby its potential role as a target for therapy for heart failure.

Spironolactone and its main metabolite canrenoic acid block hKv1.5, Kv4.3 and Kv7.1 + minK channels

Both spironolactone (SP) and its main metabolite, canrenoic acid (CA), prolong cardiac action potential duration and decrease the Kv11.1 (HERG) current. We examined the effects of SP and CA on cardiac hKv1.5, Kv4.3 and Kv7.1+minK channels that generate the human I(Kur), I(to1) and I(Ks), which contribute to the control of human cardiac action potential duration.hKv1.5 currents were recorded in stably transfected mouse fibroblasts and Kv4.3 and Kv7.1 + minK in transiently transfected Chinese hamster ovary cells using the whole-cell patch clamp. SP (1 microM) and CA (1 nM) inhibited hKv1.5 currents by 23.2 +/- 3.2 and 18.9 +/- 2.7%, respectively, shifted the midpoint of the activation curve to more negative potentials and delayed the time course of tail deactivation.SP (1 microM) and CA (1 nM) inhibited the total charge crossing the membrane through Kv4.3 channels at +50 mV by 27.1 +/- 6.4 and 27.4 +/- 5.7%, respectively, and accelerated the time course of current decay. CA, but not SP, shifted the inactivation curve to more hyperpolarised potentials (V(h)-37.0 +/- 1.8 vs -40.8 +/- 1.6 mV, n = 10, P < 0.05).SP (10 microM) and CA (1 nM) also inhibited Kv7.1 + minK currents by 38.6 +/- 2.3 and 22.1 +/- 1.4%, respectively, without modifying the voltage dependence of channel activation. SP, but not CA, slowed the time course of tail current decay.CA (1 nM) inhibited the I(Kur) (29.2 +/- 5.5%) and the I(to1) (16.1 +/- 3.9%) recorded in mouse ventricular myocytes and the I(K) (21.8 +/- 6.9%) recorded in guinea-pig ventricular myocytes.A mathematical model of human atrial action potentials demonstrated that K(+) blocking effects of CA resulted in a lengthening of action potential duration, both in normal and atrial fibrillation simulated conditions. The results demonstrated that both SP and CA directly block hKv1.5, Kv4.3 and Kv7.1 + minK channels, CA being more potent for these effects. Since peak free plasma concentrations of CA ranged between 3 and 16 nM, these results indicated that blockade of these human cardiac K(+) channels can be observed after administration of therapeutic doses of SP. Blockade of these cardiac K(+) currents, together with the antagonism of the aldosterone proarrhythmic effects produced by SP, might be highly desirable for the treatment of supraventricular arrhythmias.

Aldosterone receptor antagonists in the medical management of chronic heart failure

The benefits of aldosterone receptor antagonists (spironolactone and eplerenone) for patients with heart failure were shown in 2 recent randomized controlled trials. Some of the proposed mechanisms of action of aldosterone antagonists are (1) inhibition of myocardial and vascular remodeling, (2) blood pressure reduction, (3) decreased collagen deposition, (4) decreased myocardial stiffness, (5) prevention of hypokalemia and arrhythmia, (6) modulation of nitric oxide synthesis, and (7) immunomodulation. Like many hormone receptors, the aldosterone receptor can be either nuclear or membrane bound. Most of the activities of the aldosterone receptor are subserved by the nuclear receptors and often lead to alterations in gene transcription. Although these agents are well tolerated in carefully selected patient populations that meet the inclusion criteria of large clinical trials, their use in unselected elderly patients with heart failure and multiple comorbidities has been associated with a significant risk of hyperkalemia and renal failure. Although no convincing data exist to predict which individual patients will respond to aldosterone inhibition, patients with more severe heart failure and those with acute myocardial infarction with concomitant heart failure or left ventricular dysfunction are most likely to respond. Theoretically, aldosterone receptor antagonists may also be beneficial in patients with more mild to moderate systolic heart failure or even in those with diastolic heart failure, although direct evidence is still lacking.

Bone loss in rats with aldosteronism

OBJECTIVE

We hypothesized that aldosteronism is accompanied by hypercalciuria and hypermagnesuria that lead to bone loss, which could be rescued by hydrochlorothiazide and spironolactone.

METHODS

We monitored 24-hour urinary Ca and Mg excretion; plasma ionized [Ca]o and [Mg]o and plasma K; and bone mineral density of the femur. The following groups (n=5 in each group) were studied: age- and gender-matched, untreated controls; controls + 4 weeks hydrochlorothiazide; 4 weeks aldosterone/salt treatment (ALDOST, 0.75 mug/h and dietary 1% NaCl/0.4% KCl); 4 weeks ALDOST+hydrochlorothiazide (50 mg/kg in prepared food); and 4 weeks ALDOST+hydrochlorothiazide+spironolactone (200 mg/kg day in divided doses by twice-daily gavage).

RESULTS

ALDOST increased (P<0.05) urinary Ca and Mg excretion four- and twofold, respectively; hydrochlorothiazide co-treatment attenuated (P<0.05) Ca excretion in controls and during ALDOST without affecting augmented Mg excretion whereas hydrochlorothiazide+spironolactone normalized Ca and reduced Mg excretion (P<0.05). Compared with controls, plasma [Ca]o at 4 weeks of ALDOST was reduced (0.89+/-0.02 versus 0.83+/-0.03 mmol/L; P<0.05) but remained no different from levels in controls with hydrochlorothiazide and hydrochlorothiazide+spironolactone (0.88+/-0.04 and 0.97+/-0.03 mmol/L, respectively). Plasma [Mg]o fell (P<0.05) with ALDOST+hydrochlorothiazide (0.23+/-0.01 versus 0.34+/-0.01 mmol/L) and was prevented with spironolactone co-treatment (0.33+/-0.01 mmol/ dL). Hypokalemia (2.9+/-0.2 mmol/L) occurred in rats with ALDOST+hydrochlorothiazide but not with spironolactone co-treatment. At 4 weeks of ALDOST, plasma parathyroid hormone was increased (30+/-4 versus 11+/-3 pg/mL; P<0.05) and bone mineral density was reduced (0.153+/-0.006 versus 0.170+/-0.002 g/cm; P<0.05). Co-treatments with either hydrochlorothiazide or hydrochlorothiazide+spironolactone each prevented bone loss.

CONCLUSIONS

Hypercalciuria and hypermagnesuria accompany aldosteronism and account for a decline in their plasma ionized concentrations and secondary hyperparathyroidism with bone resorption. Attenuation of bone loss in aldosteronism can be achieved with hydrochlorothiazide; however, mono- and divalent cation homeostasis, together with bone integrity, are each preserved with the combination hydrochlorothiazide+spironolactone.

Nonsustained ventricular tachycardia in dilated cardiomyopathy

In patients with structural heart disease, ventricular arrhythmias are associated with an increased risk of overall mortality and sudden cardiac death (SCD). Nonsustained ventricular tachycardia (NSVT) is common in patients with dilated cardiomyopathy of both ischemic and nonischemic origin. Recent studies suggest that NSVT may be a marker, but not a significant predictor, of mortality and SCD in that suppression of NSVT in these patients using antiarrhythmic drugs is of questionable benefit. Additionally, indications for implantable cardioverter defibrillator implantation do not include NSVT. This article focuses on the prognostic significance and treatment of patients with NSVT and ischemic or nonischemic dilated cardiomyopathy.

Current role of device therapy to reduce sudden cardiac death in heart failure

Sudden cardiac death (SCD) continues to be a major contributor to mortality in patients with heart failure (HF) despite recent advances in medical therapy. Device therapy, including the implantable cardioverter defibrillator (ICD) and cardiac resynchronization therapy (CRT), serves as an adjunct in reducing HF mortality. Several clinical trials support the prophylactic use of the ICD in reducing mortality in certain HF populations and have established the clinical benefits of CRT in advanced HF. More recently, the Comparison of Medical Therapy Pacing and Defibrillation in Heart Failure trial was the first study to demonstrate a survival benefit of CRT alone or in conjunction with an ICD. This article reviews the most pertinent data regarding the role of device therapy in reducing SCD in HF and addresses future challenges faced by device manufacturers and clinicians.

Conditional mineralocorticoid receptor expression in the heart leads to life-threatening arrhythmias

BACKGROUND

Life-threatening cardiac arrhythmia is a major source of mortality worldwide. Besides rare inherited monogenic diseases such as long-QT or Brugada syndromes, which reflect abnormalities in ion fluxes across cardiac ion channels as a final common pathway, arrhythmias are most frequently acquired and associated with heart disease. The mineralocorticoid hormone aldosterone is an important contributor to morbidity and mortality in heart failure, but its mechanisms of action are incompletely understood.

METHODS AND RESULTS

To specifically assess the role of the mineralocorticoid receptor (MR) in the heart, in the absence of changes in aldosteronemia, we generated a transgenic mouse model with conditional cardiac-specific overexpression of the human MR. Mice exhibit a high rate of death prevented by spironolactone, an MR antagonist used in human therapy. Cardiac MR overexpression led to ion channel remodeling, resulting in prolonged ventricular repolarization at both the cellular and integrated levels and in severe ventricular arrhythmias.

CONCLUSIONS

Our results indicate that cardiac MR triggers cardiac arrhythmias, suggesting novel opportunities for prevention of arrhythmia-related sudden death.

Evidence for an increased rate of cardiovascular events in patients with primary aldosteronism

OBJECTIVES

The aim of this report was to show that the rate of cardiovascular events is increased in patients with either subtype of primary aldosteronism (PA).

BACKGROUND

Primary aldosteronism involves hypertension (HTN), hypokalemia, and low plasma renin. The two major PA subtypes are unilateral aldosterone-producing adenoma (APA) and bilateral adrenal hyperplasia.

METHODS

During a three-year period, the diagnosis of PA was made in 124 of 5,500 patients referred for comprehensive evaluation and management. Adenomas were diagnosed in 65 patients and idiopathic hyperaldosteronism in 59 patients. During the same period, clinical characteristics and cardiovascular events of this group were compared with those of 465 patients with essential hypertension (EHT) randomly matched for age, gender, and systolic and diastolic blood pressure.

RESULTS

A history of stroke was found in 12.9% of patients with PA and 3.4% of patients with EHT (odds ratio [OR] = 4.2; 95% confidence interval [CI] 2.0 to 8.6]). Non-fatal myocardial infarction was diagnosed in 4.0% of patients with PA and in 0.6% of patients with EHT (OR = 6.5; 95% CI 1.5 to 27.4). A history of atrial fibrillation was diagnosed in 7.3% of patients with PA and 0.6% of patients with EHT (OR = 12.1; 95% CI 3.2 to 45.2). The occurrence of cardiovascular complications was comparable in both subtypes of PA.

CONCLUSIONS

Patients presenting with PA experienced more cardiovascular events than did EHT patients independent of blood pressure. The presence of PA should be detected, not only to determine the cause of HTN, but also to prevent such complications.

Interactions of High Salt Intake and the Response of the Cardiovascular System to Aldosterone

High salt intake contributes to the risk of hypertension, and this effect is in part mediated by the physiologic action of aldosterone on renal mineralocorticoid receptors. However, the actions of aldosterone are not restricted to the kidneys, because aldosterone can bind to mineralocorticoid receptors in the heart, vasculature, and brain to produce structural and functional changes that lead to target organ damage. Experimental and clinical studies show that, in the setting of high salt intake, blocking aldosterone at the mineralocorticoid receptor reduces progression to target organ damage and preserves vascular function. In many cases, these benefits are independent of changes in blood pressure. Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers have short-term effects on reducing aldosterone levels, but frequently aldosterone levels return to pretreatment levels during long-term therapy. Aldosterone blockade may be more completely achieved with mineralocorticoid receptor antagonists. Spironolactone has been shown to have substantial and significant benefits in experimental and clinical studies of cardiac dysfunction. Eplerenone is a selective aldosterone blocker with a greater binding affinity for mineralocorticoid receptors than for androgen and progesterone receptors. Eplerenone has similarly demonstrated significant benefits in experimental animals and in patients with left ventricular dysfunction after myocardial infarction. Thus, aldosterone blockade with mineralocorticoid receptor antagonists offers target organ protection and may blunt some of the adverse effects of chronic high salt intake.

Aldosterone and end-organ damage

PURPOSE OF REVIEW

This review highlights recent clinical studies demonstrating the contribution of aldosterone to cardiovascular mortality, vascular dysfunction, and renal injury in the context of advances in our understanding of the molecular biology of aldosterone.

RECENT FINDINGS

Mineralocorticoid receptor antagonism reduces mortality in patients with congestive heart failure and following myocardial infarction. Studies in animal models and in patients with congestive heart failure or hypertension indicate that aldosterone induces oxidative stress and impairs endothelial nitric oxide synthase through a mineralocorticoid receptor-dependent mechanism. Furthermore, aldosterone can cause vasoconstriction and vasodilation through rapid nongenomic mechanisms. The contribution of the nongenomic effects of aldosterone to vascular tone may depend on underlying endothelial function. In the heart and kidney, aldosterone stimulates oxidative stress and increases expression of inflammatory markers leading to fibrosis. The induction of inflammation and fibrosis appears to be both sodium and mineralocorticoid receptor dependent. The mechanisms underlying the progression from inflammation to fibrosis remain to be elucidated. Studies measuring circulating markers of collagen turnover suggest that mineralocorticoid antagonism reduces extracellular matrix turnover and cardiac remodeling in humans as well. Similarly, mineralocorticoid receptor antagonism reduces urinary albumen excretion in clinical trials in humans.

SUMMARY

Aldosterone induces oxidative stress, endothelial dysfunction, inflammation and fibrosis in the vasculature, heart and kidney. While most of these effects appear to be mediated via the mineralocorticoid receptor, better understanding of the mineralocorticoid receptor-independent effects of aldosterone, the role of nonaldosterone mineralocorticoid receptor agonists, and the mechanisms involved in the progression from inflammation to fibrosis and remodeling would enable the development of new strategies to slow the progression of cardiovascular and renal disease.

Angiotensin II, angiotensin II antagonists and spironolactone and their modulation of cardiac repolarization

Angiotensin II and aldosterone produce pro-arrhythmic effects by several mechanisms, including the modulation of voltage-dependent K(+) channels involved in human cardiac repolarization. Drugs that inhibit the renin-angiotensin-aldosterone system exert anti-arrhythmic actions that are related to the blockade of the pro-arrhythmic actions of angiotensin II and aldosterone. These anti-arrhythmic actions include inhibition of electrical and structural cardiac remodeling, inhibition of neurohumoral activation, reduction of blood pressure and stabilization of electrolyte disturbances. In this article, several angiotensin II AT(1) receptor antagonists (candesartan, E3174, eprosartan, irbesartan and losartan) and aldosterone receptor antagonists (canrenoic acid and spironolactone) that directly modulate the activity of the voltage-dependent K(+) channels are reviewed; the effects of these antagonists might be useful in the prevention and treatment of cardiac arrhythmias.

Ventricular Dysrhythmias in Heart Failure

Left-ventricular systolic dysfunction, or heart failure (HF), is a chronic, progressive condition with a poor prognosis. Approximately 50% of deaths, especially in mild to moderate cases, are sudden. Most sudden deaths are thought to be due to ventricular tachycardia; however, premature ventricular contractions and couplets parallel severity of HF and have been associated with increased mortality risk as opposed to dysrhythmic death. Ventricular arrhythmogenesis results from many mechanisms (afterdepolarizations, reentry, and enhanced automaticity) and preconditions (electrophysiologic abnormalities, neuroendocrine activation, electrolyte imbalances, scar from an ischemic event in ischemic cardiomyopathy, fibrosis in dilated cardiomyopathy, hemodynamic abnormalities, and HF medical management). Nurses are key caregivers in optimally managing HF, either by direct actions or by using advocacy, communication, and collaboration skills to promote positive outcomes. Ventricular dysrhythmia management consists of facilitating core HF pharmacologic and nonpharmacologic medical therapies, using amiodarone to improve symptoms, as needed, and utilizing implantable cardioverter-defibrillator therapy to reduce the risk of sudden cardiac death.

Autoimmunity against the second extracellular loop of beta(1)-adrenergic receptors induces early afterdepolarization and decreases in K-channel density in rabbits

OBJECTIVES

We sought to define the electrophysiologic property of the rabbit heart associated with autoimmunity against the second extracellular loop of the beta(1)-adrenergic receptor.

BACKGROUND

Sudden death of patients with cardiomyopathy, probably due to lethal ventricular arrhythmias, can be predicted by the presence of autoantibodies against the second extracellular loop of the beta(1)-adrenergic receptor.

METHODS

Rabbits were immunized by repetitive subcutaneous administration of a synthetic peptide corresponding to the second extracellular loop of beta(1)-adrenergic receptors (beta group; n = 30) for a mean of 4.2 months. Control rabbits received only vehicle (control group; n = 30).

RESULTS

One of the rabbits in the beta group died suddenly during the observation period, but none of the control animals died. The prevalence of sustained ventricular tachycardia was significantly higher in the beta group (beta: 4 of 27 vs. control: 0 of 30), and a standard microelectrode experiment revealed prolongation of the action potential duration (APD) in the right ventricular papillary muscle (beta: 156 +/- 5 ms vs. control: 131 +/- 4 ms; p < 0.05). Early afterdepolarization (EAD) was observed in one rabbit in the beta group (1 of 26), but not in any animals in the control group (0 of 17). A dose of 100 nmol/l of E-4031 induced EAD in the beta group (10 of 10), but not in the control group, except for one rabbit (1 of 10). The whole-cell, patch-clamp experiment on left ventricular M cells showed significant decreases in transient outward current (I(to1)) (-43%) and slowly activated delayed rectifier current (I(Ks)) densities (-33%), whereas the inward-rectifying K current (I(K1)) and rapidly activated delayed rectifier current (I(Kr)) densities remained unchanged.

CONCLUSIONS

Long-term immunization against the second extracellular loop of the beta(1)-adrenergic receptor caused EAD and APD prolongation and decreased the K-channel density, suggesting that an arrhythmic substrate via autoimmune mechanisms is present in cardiomyopathic patients who have autoantibodies directed against the receptors.

Aldosterone-synthase overexpression in heart: a tool to explore aldosterone's effects

Clinical observations indicate that elevated aldosterone impairs cardiovascular function. The mechanisms, however, are not totally understood although total and cardiovascular mortality are decreased by aldosterone antagonists. Experimentally, increased plasma aldosterone induces pericoronary inflammation and cardiac fibrosis. Our laboratory has discovered that aldosterone is synthesized in the rat heart, and has demonstrated that this cardiac aldosterone is involved in post-infarction cardiac remodeling. In man, activated cardiac aldosterone production has been described in patients with heart failure. In transgenic mice that overexpress aldosterone-synthase in the heart, we observe a normal cardiac function but a major coronary dysfunction, more pronounced in males. These observations converge to a potential physiological and pathological relevance of this system. Beneficial effects of anti-aldosterone treatment in heart failure may thus be secondary in part to blockade of cardiac aldosterone action.

Effects of Repeated Sauna Treatment on Ventricular Arrhythmias in Patients With Chronic Heart Failure

BACKGROUND

The aim of the present study was to determine whether repeated 60 degrees C sauna treatment improves cardiac arrhythmias in chronic heart failure (CHF) patients, because ventricular arrhythmias are an important therapeutic target in CHF.

METHODS AND RESULTS

Thirty patients (59+/-3 years) with New York Heart Association functional class II or III CHF and at least 200 premature ventricular contractions (PVCs)/24 h assessed by 24-h Holter recordings were studied. They were randomized into sauna-treated (n=20) or non-treated (n=10) groups. The sauna-treated group underwent a 2-week program of a daily 60 degrees C far infrared-ray dry sauna for 15 min, followed by 30 min bed rest with blankets, for 5 days per week. Patients in the non-treated group had bed rest in a temperature-controlled room (24 degrees C) for 45 min. The total numbers of PVCs/24 h in the sauna-treated group decreased compared with the non-treated group [848+/-415 vs 3,097+/-1,033/24 h, p<0.01]. Heart rate variability (SDNN, standard deviation of normal-to-normal beat interval) increased [142+/-10 (n=16) vs 112+/-11 ms (n=8), p<0.05] and plasma brain natriuretic peptide concentrations decreased [229+/-54 vs 419+/-110 pg/ml, p<0.05] in the sauna-treated group compared with the non-treated group.

CONCLUSION

Repeated sauna treatment improves ventricular arrhythmias in patients with CHF.

Corticosteroid receptors, 11 beta-hydroxysteroid dehydrogenase, and the heart

Mineralocorticoid and glucocorticoid hormones are known as corticosteroid hormones and are synthesized mainly in the adrenal cortex; however, more recently the enzymes involved in their synthesis have been found in a variety of cells and tissues, including the heart. The effects of these hormones are mediated via both cytoplasmic mineralocorticoid receptors (MRs) and glucocorticoid receptors (GRs), which act as ligand-inducible transcription factors. In addition, rapid, nongenomically mediated effects of these steroids can occur that may be via novel corticosteroid receptors. The lipophilic nature of these hormones allows them to pass freely through the cell membrane, although the intracellular concentration of mineralocorticoids and glucocorticoids is dependent on several cellular factors. The main regulators of intracellular glucocorticoid levels are 11 beta-hydroxysteroid dehydrogenase (11 beta HSD) isoforms. 11 beta HSD1 acts predominantly as a reductase in vivo, facilitating glucocorticoid action by converting circulating receptor-inactive 11-ketoglucocorticoids to active glucocorticoids. In contrast, 11 beta HSD 2 acts exclusively as an 11 beta-dehydrogenase and decreases intracellular glucocorticoids by converting them to their receptor-inactive 11-ketometabolites. Furthermore, P-glycoproteins, by actively pumping steroids out of cells, can selectively decrease steroids and local steroid synthesis can increase steroid concentrations. Receptor concentration, receptor modification, and receptor-protein interactions can also significantly impact on the corticosteroid response. This review details the receptors and possible mechanisms involved in both mediating and modulating corticosteroid responses. In addition, direct effects of corticosteroids on the heart are described including a discussion of the corticosteroid receptors and the mechanisms involved in mediating their effects.

Prescription patterns of diuretics in chronic heart failure: a contemporary background as a clue to their role in treatment

BACKGROUND

Diuretics are the cornerstone of treatment for the congestive symptoms of heart failure (HF). Despite their widespread use, diuretic prescription data in clinical practice are scarce. In this study we evaluated the prescription pattern of diuretics in a large population of HF outpatients, enrolled by a national network of hospital-based cardiologists.

METHODS AND RESULTS

Among 11070 HF outpatients (mean age 64 +/- 12 years, 72.9% men, 29.8% New York Heart Association [NYHA] class III-IV, mean left ventricular ejection fraction [LVEF] 35+/-12%), 9247 took a diuretic, the most frequently prescribed therapeutic agent (83.5%). Loop diuretics were prescribed alone (65.5%) or combined with other diuretics in 91.6% of patients. By multivariate analysis, the strongest independent predictors of diuretic use were a previous hospital admission for HF (odds ratio [OR] 2.55, 95% confidence interval [CI] 2.28-2.86), NYHA class III-IV (OR 2.52, 95% CI 2.14-2.96), LVEF < 30% (OR 1.87, 95% CI 1.57-2.24). Aldosterone antagonists were prescribed to 2142 patients (23.1%); independent predictors of their use overlapped with those of diuretics and moreover included treatment with loop diuretics (OR 3.52, 95% CI 2.66-4.66) and digoxin (OR 1.45, 95% CI 1.29-1.64).

CONCLUSIONS

In this wide series of stable HF outpatients, cardiologists prescribed diuretics in accordance with published guidelines. Evolving prescription patterns of aldosterone-receptor blockers need to be further evaluated.

Eplerenone: cardiovascular protection

Data from animal studies and clinical trials indicate that aldosterone causes cardiovascular and renal injury through mineralocorticoid receptor-dependent mechanisms. However, although aldosterone receptor antagonism reduces mortality in patients with congestive heart failure, the progestational and antiandrogenic side effects of the nonspecific aldosterone receptor antagonist, spironolactone, have limited its usefulness in the treatment of hypertension. This review provides an overview of the pharmacology, efficacy, and safety of a new, more selective aldosterone receptor antagonist, eplerenone, in the context of emerging concepts of the role of aldosterone in cardiovascular toxicity.

Neurohumoral activation and ventricular arrhythmias in patients with decompensated congestive heart failure: role of endothelin

Patients with congestive heart failure (CHF) have a high incidence of ventricular arrhythmias and sudden arrhythmic death. CHF entails profound and complex abnormalities in humoral responses that are thought to promote arrhythmic events. However, it is unknown which of the many endogenous mediators that accumulate as part of neurohormonal activation is important in arrhythmogenesis in the setting of CHF. The study included 83 patients admitted to the hospital for treatment of decompensated CHF. Neurohormonal and cytokine activation was assessed by measuring plasma renin activity, aldosterone, norepinephrine, endothelin-1, tumor necrosis factor-alpha, and interleukin-6 levels. Atrial and ventricular arrhythmic events were assessed by 24-hour Holter monitoring. In a univariate analysis, a highly significant, positive relationship was found between plasma endothelin-1 levels and the average hourly total premature ventricular beats (P = 0.003), the frequency of ventricular pairs (P = 0.0003), and the frequency of ventricular tachycardia episodes (P = 0.001). After inclusion of clinical variables, drug therapies, neurohormones, and cytokine levels in a multivariate analysis, the positive relationship between plasma endothelin-1 level and the average hourly total premature ventricular beats (P = 0.008), the frequency of ventricular pairs (P = 0.007), and ventricular tachycardia episodes (P = 0.009) remained independent. No association between other neurohormones or cytokines and arrhythmic events was demonstrated. The results of the present study suggest that increased endothelin-1 concentrations may be involved in promoting the occurrence of ventricular ectopy in patients with decompensated CHF. Proarrhythmic effects may account, in part, for the poor outcome associated with increased endothelin-1 levels in patients with decompensated CHF.

Rationale for the use of aldosterone antagonists in congestive heart failure

Traditionally, the role of aldosterone in heart failure was thought to be a result of its effects on epithelial cells where it induces sodium reabsorption and potassium excretion with subsequent haemodynamic effects from intravascular volume expansion. On this basis, spironolactone, a non-selective aldosterone antagonist, has been used for the treatment of congestive heart failure to block aldosterone-mediated effects in epithelial cells. The Randomized Aldactone Evaluation Study (RALES), in which spironolactone was added to existing therapy in patients with heart failure, showed a significant reduction in morbidity and mortality. These results suggest that the role of aldosterone in the pathophysiology of cardiovascular disease may be more complex than previously recognised. There now is extensive experimental and growing clinical evidence for an important physiological role for aldosterone in the pathology of cardiac and renal disease. Classical effects of aldosterone are mediated via its nuclear receptor. Novel non-epithelial effects of aldosterone are mediated via a second messenger system, which involves activation of the sodium/hydrogen antiporter. These effects of aldosterone have been demonstrated in the kidney, vascular smooth muscle cell and leukocytes, and in the regulation of rapid corticotropin suppression. It has been hypothesised that cardiac damage induced by aldosterone is independent of the presence of hypertension. In support of this, experimental evidence demonstrates that cardiovascular damage induced by aldosterone can be prevented by administration of a selective mineralocorticoid receptor antagonist. These findings suggest the dissociation between cardiovascular lesions and high blood pressure, and highlight the importance of aldosterone in the pathological changes.

Reversible cardiac fibrosis and heart failure induced by conditional expression of an antisense mRNA of the mineralocorticoid receptor in cardiomyocytes

Cardiac failure is a common feature in the evolution of cardiac disease. Among the determinants of cardiac failure, the renin-angiotensin-aldosterone system has a central role, and antagonism of the mineralocorticoid receptor (MR) has been proposed as a therapeutic strategy. In this study, we questioned the role of the MR, not of aldosterone, on heart function, using an inducible and cardiac-specific transgenic mouse model. We have generated a conditional knock-down model by expressing solely in the heart an antisense mRNA directed against the murine MR, a transcription factor with unknown targets in cardiomyocytes. Within 2-3 mo, mice developed severe heart failure and cardiac fibrosis in the absence of hypertension or chronic hyperaldosteronism. Moreover, cardiac failure and fibrosis were fully reversible when MR antisense mRNA expression was subsequently suppressed.

Alteration of cardiac and renal functions in transgenic mice overexpressing human mineralocorticoid receptor

The mineralocorticoid receptor (MR), a ligand-dependent transcription factor, mediates aldosterone actions in a large variety of tissues. To explore the functional implication of MR in pathophysiology, transgenic mouse models were generated using the proximal human MR (hMR) promoter to drive expression of hMR in aldosterone target tissues. Tissue-specific analysis of transgene expression in two independent transgenic animal (TG) lines by ribonuclease protection assays revealed that hMR is expressed in all mineralocorticoid-sensitive tissues, most notably in the kidney and the heart. TG exhibit both renal and cardiac abnormalities. Enlarged kidneys were histologically associated with renal tubular dilation and cellular vacuolization whose prevalence increased with aging. Renal clearance studies also disclosed a significant decrease in urinary potassium excretion rate in TG. hMR-expressing animals had normal blood pressure but developed mild dilated cardiomyopathy (increased left ventricle diameters and decreased shortening fraction), which was accompanied by a significant increase in heart rate. Differential gene expression analysis revealed a 2- to 5-fold increase in cardiac expression of atrial natriuretic peptide, serum- and glucocorticoid-induced kinase, and early growth response gene 1 as detected by microarrays; renal serum- and glucocorticoid-induced kinase was also induced significantly. Altogether, TG exhibited specific alteration of renal and cardiac functions, thus providing useful pathophysiological models to gain new insights into the tissue-specific mineralocorticoid signaling pathways.

New perspectives on the role of aldosterone excess in cardiovascular disease

1. Evidence from recent experimental and clinical studies suggests that excessive circulating levels of aldosterone can bring about adverse cardiovascular sequelae independent of the effects on blood pressure. Examples of these sequelae are the development of myocardial and vascular fibrosis in uninephrectomized, salt-loaded rats infused with mineralocorticoids and, in humans, an association of aldosterone with left ventricular hypertrophy, impaired diastolic and systolic function, salt and water retention causing aggravation of congestion in patients with established congestive cardiac failure (CCF), reduced vascular compliance and an increased risk of arrhythmias (resulting from intracardiac fibrosis, hypokalaemia, hypomagnesaemia, reduced baroreceptor sensitivity and potentiation of catecholamine effects). 2. These sequelae of aldosterone excess may contribute to the pathogenesis and worsen the prognosis of CCF and hypertension. 3. The heart and blood vessels may be capable of extra-adrenal aldosterone biosynthesis, raising the possibility that aldosterone may have paracrine or autocrine (and not just endocrine) effects on cardiovascular tissues. 4. The high prevalence of CCF, which is associated with secondary aldosteronism, and primary aldosteronism (PAL; recently recognized to be a much more common cause of hypertension than was previously thought) argue for an important role for aldosterone excess as a cause of cardiovascular injury. 5. The recognition of non-blood pressure-dependent adverse sequelae of aldosterone excess raises the question as to whether normotensive individuals with PAL, who have been detected as a result of genetic or biochemical screening among families with inherited forms of PAL, are at excess risk of cardiovascular events. 6. Provided that patients are carefully investigated in order to permit the appropriate selection of specific surgical (laparoscopic adrenalectomy for PAL that lateralizes on adrenal venous sampling) or medical (treatment with aldosterone antagonist medications) management and safety considerations for the use of aldosterone antagonists are kept in mind, the appreciation of a widening role for aldosterone in cardiovascular disease should provide a substantially better outlook for many patients with CCF and hypertension.

Recent studies with eplerenone, a novel selective aldosterone receptor antagonist

Activation of the renin-angiotensin-aldosterone system is associated with unsatisfactory outcomes in patients with hypertension and congestive heart failure, in that activation of this system is correlated strongly with both the incidence and extent of end-organ damage. Despite the availability of the angiotensin-converting enzyme inhibitors and the AT1 receptor antagonists, unblocked aldosterone levels remain an important risk factor for cardiovascular disease progression. New preclinical data generated over the past few years strongly support the hypothesis that aldosterone has important deleterious effects on the cardiovascular system independent of the classical action of this hormone on renal epithelial cells. The new selective aldosterone receptor antagonist eplerenone has been shown to produce significant cardioprotective effects in experimental models of cardiovascular disease. Early clinical testing suggests that eplerenone may have important therapeutic benefit in the treatment of hypertension and heart failure.