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

Tachycardia-Induced Cardiomyopathy in an Infant with Atrial Flutter and Prolonged Recovery of Cardiac Function

Background: Tachycardia-induced cardiomyopathy (TIC) is caused by prolonged tachycardia, leading to left ventricular dilatation and systolic dysfunction with heart failure. Although TIC is more common in adults, it is rare in early infancy. Methods: Clinical testing was performed as part of medical evaluation and management. Next-generation sequencing (NGS) was conducted for a patient with TIC. A literature review on TIC was also conducted. Results: The case involved a 5-month-old infant referred to the hospital due to symptoms of heart failure lasting at least two months. The infant's heart rate was 200 beats per minute, the left ventricular ejection fraction fell below 14%, and electrocardiograms showed atrial flutter, suggesting TIC. After cardioversion, there was no recurrence of atrial flutter, and cardiac function improved 98 days after tachycardia arrest. The NGS did not identify any pathogenic variants. The literature review identified eight early infantile cases of TIC. However, no previous reports described a case with such a prolonged duration of TIC as ours. Conclusions: This is the first report of a case of prolonged TIC in a child with the documented time to recover normal cardiac function. The improvement of cardiac function depends on the duration of TIC. Early recognition and intervention in TIC are essential to improve outcomes for infantile patients, as timely treatment offers the potential for recovery.

Relation of Plasma Catecholamine Concentrations and Myocardial Mitochondrial Respiratory Activity in Anesthetized and Mechanically Ventilated, Cardiovascular Healthy Swine

Chronic heart failure is associated with reduced myocardial β-adrenergic receptor expression and mitochondrial function. Since these data coincide with increased plasma catecholamine levels, we investigated the relation between myocardial β-receptor expression and mitochondrial respiratory activity under conditions of physiological catecholamine concentrations. This post hoc analysis used material of a prospective randomized, controlled study on 12 sexually mature (age 20-24 weeks) Early Life Stress or control pigs (weaning at day 21 and 28-35 after birth, respectively) of either sex. Measurements in anesthetized, mechanically ventilated, and instrumented animals comprised serum catecholamine (liquid-chromatography/tandem-mass-spectrometry) and 8-isoprostane levels, whole blood superoxide anion concentrations (electron spin resonance), oxidative DNA strand breaks (tail moment in the "comet assay"), post mortem cardiac tissue mitochondrial respiration, and immunohistochemistry (β2-adrenoreceptor, mitochondrial respiration complex, and nitrotyrosine expression). Catecholamine concentrations were inversely related to myocardial mitochondrial respiratory activity and β2-adrenoceptor expression, whereas there was no relation to mitochondrial respiratory complex expression. Except for a significant, direct, non-linear relation between DNA damage and noradrenaline levels, catecholamine concentrations were unrelated to markers of oxidative stress. The present study suggests that physiological variations of the plasma catecholamine concentrations, e.g., due to physical and/or psychological stress, may affect cardiac β2-adrenoceptor expression and mitochondrial respiration.

Emerging concepts in heart failure management and treatment: focus on tachycardia-induced cardiomyopathy

Tachycardia-induced cardiomyopathy is an entity characterized by reversible dysfunction of the left ventricle, which can be induced by different types of arrhythmia such as atrial fibrillation, atrial flutter, incessant supraventricular tachycardia and ventricular arrhythmia (more frequent causes). Correct identification of the causative arrhythmia and normalization of the heart rate (e.g through medical treatment, electrical cardioversion, ablation) can lead to recovery of left ventricular function. Tachycardia-induced cardiomyopathy should be suspected in patients with tachycardia and left ventricular dysfunction (heart failure setting), especially when there is no history of previous heart disease. Its usual phenotype is that of non-ischaemic/non-valvular dilated cardiomyopathy and it can occur in both children (main cause: permanent junctional reciprocating tachycardia) and adults (main cause: atrial fibrillation). With proper treatment, most cases recover within a few months, though there is a risk of relapse, especially when the causal arrhythmia reappears or its control is lost. This is a narrative review that comprehensively addresses the pathophysiology, clinical manifestations, and therapeutic management of tachycardia-induced cardiomyopathy. This article is part of the Emerging concepts in heart failure management and treatment Special Issue: https://www.drugsincontext.com/special_issues/emerging-concepts-in-heart-failure-management-and-treatment.

Atrial Fibrillation and Heart Failure: Epidemiology, Pathophysiology, Prognosis, and Management

Atrial fibrillation (AF) and heart failure (HF) have similar risk factors, frequently coexist, and potentiate each other in a vicious cycle. Evidence suggests the presence of AF in both HF with reduced ejection fraction (HFrEF) and HF with preserved ejection fraction (HFpEF) increases the risk of all-cause mortality and stroke, particularly when AF is incident. Catheter ablation may be an effective strategy in controlling symptoms and improving quality of life in AF-HFrEF. Strong data guiding management of AF-HFpEF are lacking largely due to its challenging diagnosis. Improving outcomes associated with these coexistent conditions requires further careful investigation.

Effects of dual blockade in heart failure and renal dysfunction: Systematic review and meta-analysis

OBJECTIVE

The effect of dual renin-angiotensin system (RAS) inhibition in heart failure (HF) is still controversial. Systematic reviews have shown that dual RAS blockade may reduce mortality and hospitalizations, yet it has been associated with the increased risk of renal dysfunction (RD). Surprisingly, although RD in patients with HF is frequent, the effect of combining RAS inhibitors in HF patients with RD has never been studied in a meta-analysis.

METHODS

A systematic review and meta-analysis of randomized clinical trials involving HF patients with RD who received dual blockade analyzing death, cardiovascular (CV) death or HF hospitalization, and adverse events.

RESULTS

Out of 2258 screened articles, 12 studies were included (34,131 patients). Compared with monotherapy, dual RAS inhibition reduced hazard ratio of death to 0.94 (p=0.07) and significantly reduced CV death or HF hospitalization to 0.89 (p=0.0006) in all individuals, and to 0.86 (p=0.005) in patients with RD and to 0.91 (p=0.04) without RD. Nevertheless, dual RAS blockade significantly increased the risk of renal impairment (40%), hyperkalemia (44%), and hypotension (42%), although discontinuation of treatment occurs only in 3.68% versus 2.19% (p=0.00001).

CONCLUSIONS

Dual RAS inhibition therapy reduces the risk of CV death or HF hospitalization. However, cautions monitoring for specific adverse events may be warranted.

Renin Activity in Heart Failure with Reduced Systolic Function-New Insights

Regardless of the cause, symptomatic heart failure (HF) with reduced ejection fraction (rEF) is characterized by pathological activation of the renin–angiotensin–aldosterone system (RAAS) with sodium retention and extracellular fluid expansion (edema). Here, we review the role of active renin, a crucial, upstream enzymatic regulator of the RAAS, as a prognostic and diagnostic plasma biomarker of heart failure with reduced ejection fraction (HFrEF) progression; we also discuss its potential as a pharmacological bio-target in HF therapy. Clinical and experimental studies indicate that plasma renin activity is elevated with symptomatic HFrEF with edema in patients, as well as in companion animals and experimental models of HF. Plasma renin activity levels are also reported to be elevated in patients and animals with rEF before the development of symptomatic HF. Modulation of renin activity in experimental HF significantly reduces edema formation and the progression of systolic dysfunction and improves survival. Thus, specific assessment and targeting of elevated renin activity may enhance diagnostic and therapeutic precision to improve outcomes in appropriate patients with HFrEF.

Arrhythmia-Induced Cardiomyopathy: Prevalent, Under-recognized, Reversible

Arrhythmia-induced cardiomyopathy (AIC) is a clinical condition in which a persistent tachyarrhythmia or frequent ectopy contribute to ventricular dysfunction leading to systolic heart failure. AIC can be partially or completely corrected with adequate treatment of the culprit arrhythmia. Several molecular and cellular alterations by which tachyarrhythmias lead to cardiomyopathy have been identified. AIC can affect children and adults, can be clinically silent in the form of asymptomatic tachycardia with cardiomyopathy, or can present with manifest heart failure. A high index of suspicion for AIC and aggressive treatment of the culprit arrhythmia can result in resolution of heart failure symptoms and improvement in cardiac function. Recurrent arrhythmia, following recovery from the index episode, can hasten the left ventricular dysfunction and result in HF, suggesting persistent adverse remodeling despite recovery of left ventricular function. Several aspects of AIC, such as predisposing factors, early diagnosis, preventive measures to avoid adverse remodeling, and long-term prognosis, remain unclear, and need further research.

Early activation of deleterious molecular pathways in the kidney in experimental heart failure with atrial remodeling

Heart failure (HF) is a major health problem with worsening outcomes when renal impairment is present. Therapeutics for early phase HF may be effective for cardiorenal protection, however the detailed characteristics of the kidney in early‐stage HF (ES‐HF), and therefore treatment for potential renal protection, are poorly defined. We sought to determine the gene and protein expression profiles of specific maladaptive pathways of ES‐HF in the kidney and heart. Experimental canine ES‐HF, characterized by de‐novo HF with atrial remodeling but not ventricular fibrosis, was induced by right ventricular pacing for 10 days. Kidney cortex (KC), medulla (KM), left ventricle (LV), and left atrial (LA) tissues from ES‐HF versus normal canines (n = 4 of each) were analyzed using RT‐PCR microarrays and protein assays to assess genes and proteins related to inflammation, renal injury, apoptosis, and fibrosis. ES‐HF was characterized by increased circulating natriuretic peptides and components of the renin‐angiotensin‐aldosterone system and decreased sodium and water excretion with mild renal injury and up‐regulation of CNP and renin genes in the kidney. Compared to normals, widespread genes, especially genes of the inflammatory pathways, were up‐regulated in KC similar to increases seen in LA. Protein expressions related to inflammatory cytokines were also augmented in the KC. Gene and protein changes were less prominent in the LV and KM. The ES‐HF displayed mild renal injury with widespread gene changes and increased inflammatory cytokines. These changes may provide important clues into the pathophysiology of ES‐HF and for therapeutic molecular targets in the kidney of ES‐HF.

Heart rate-induced modifications of concentric left ventricular hypertrophy: exploration of a novel therapeutic concept

Lowering the heart rate is considered to be beneficial in heart failure (HF) with reduced ejection fraction (HFrEF). In a dilated left ventricle (LV), pharmacological heart rate lowering is associated with a reduction in LV chamber size. In patients with HFrEF, this structural change is associated with better survival. HF with preserved ejection fraction (HFpEF) is increasingly prevalent but, so far, without any evidence-based treatment. HFpEF is typically associated with LV concentric remodeling and hypertrophy. The effects of heart rate on this structural phenotype are not known. Analogous with the benefits of a low heart rate on a dilated heart, we hypothesized that increased heart rates could lead to potentially beneficial remodeling of a concentrically hypertrophied LV. This was explored in an established porcine model of concentric LV hypertrophy and fibrosis. Our results suggest that a moderate increase in heart rate can be used to reduce wall thickness, normalize LV chamber volumes, decrease myocardial fibrosis, and improve LV compliance. Our results also indicate that the effects of heart rate can be titrated, are reversible, and do not induce HF. These findings may provide the rationale for a novel therapeutic approach for HFpEF and its antecedent disease substrate.

Arrhythmia-Induced Cardiomyopathies: Mechanisms, Recognition, and Management

Arrhythmia-induced cardiomyopathy (AIC) is a potentially reversible condition in which left ventricular dysfunction is induced or mediated by atrial or ventricular arrhythmias. Cellular and extracellular changes in response to the culprit arrhythmia have been identified, but specific pathophysiological mechanisms remain unclear. Early recognition of AIC and prompt treatment of the culprit arrhythmia using pharmacological or ablative techniques result in symptom resolution and recovery of ventricular function. Although cardiomyopathy in response to an arrhythmia may take months to years to develop, recurrent arrhythmia can result in rapid decline in ventricular function with development of heart failure, suggesting residual ultrastructural abnormalities. Reports of sudden death in patients with normalized left ventricular ejection fraction cast doubt on the complete reversibility of this condition. Several aspects of AIC, including specific pathophysiological mechanisms, predisposing factors, optimal therapeutic strategies to prevent ultrastructural changes, and long-term risk of sudden death remain unresolved and need further research.

Sex differences in porcine left ventricular myocardial remodeling due to right ventricular pacing

Background

Although sex differences in heart failure (HF) prevalence and severity have been recognized, its molecular mechanisms are poorly understood. We used a tachycardia-induced cardiomyopathy model to determine the sex specific remodeling pattern in male and female adult pigs.

Methods

We compared the echocardiographic and molecular measures of myocardial remodeling in 19 male and 12 female pigs with chronic symptomatic systolic HF due to right ventricle (RV) pacing (170 bpm) and 6 male and 5 female sham-operated controls. Males achieved subsequent HF stages earlier than females.

Results

The progression of symptomatic HF was associated with the reduction of the left ventricle (LV) ejection fraction in both sexes (all p < 0.05). A significant LV dilatation occurred only in males (p < 0.001). The HF development was accompanied by an increased pro-hypertrophic factor GATA4 and TGF-β1 messenger RNA (mRNA) expression in the LV only in male pigs (all p < 0.01). The total gelatinolytic activity in LV was higher in males than females (irrespective of HF, p < 0.05), and the HF progression was associated with a reduced total gelatinolytic activity (p < 0.05) in the LV only in males. No differences in LV myocardial collagen content were found between HF groups and sexes. Cardiomyocyte cross-sectional diameter was significantly smaller in male hearts as compared to female (p < 0.05).

Conclusions

Male and female porcine hearts respond differently to RV pacing. Males, most likely due to a higher extracellular matrix turnover, demonstrated a significant LV dilatation, followed by a strong induction of pro-hypertrophic program, and an earlier development of symptomatic HF.

Electronic supplementary material

The online version of this article (doi:10.1186/s13293-015-0048-4) contains supplementary material, which is available to authorized users.

Differential Effects of Prevention and Reversal Treatment with Lisinopril on Left Ventricular Remodelling in a Rat Model of Heart Failure

BACKGROUND

Angiotensin converting enzyme (ACE) inhibitors such as lisinopril, represent the front line pharmacological treatment for heart failure, which is characterised by marked left ventricular (LV) dilatation and hypertrophy. This study sought to determine whether initiating treatment with ACE inhibitors at different stages in the remodelling process would alter the efficacy of treatment.

METHODS

To this end, LV size and function were determined in the aortocaval (AV) fistula model of volume overload-induced heart failure. Sprague-Dawley rats were assigned to sham, untreated AV fistula (21 weeks), AV fistula treated with lisinopril (21 weeks), or AV fistula treated with lisinopril from six to 21 weeks post-fistula groups.

RESULTS

Administration of lisinopril for the entire 21-week period prevented LV dilatation, attenuated myocardial hypertrophy and prevented changes in myocardial compliance and contractility, whereas delaying initiation of treatment until six weeks post-fistula attenuated LV dilatation and hypertrophy, however, the delayed onset of treatment had no beneficial effect on ventricular compliance or systolic function.

CONCLUSIONS

The results demonstrate differential effects that can occur with ACE inhibitors depending on the stage during the remodelling process at which treatment is administered.

Foundations of Pharmacotherapy for Heart Failure With Reduced Ejection Fraction: Evidence Meets Practice, Part I

Pharmacologic treatment for systolic heart failure, otherwise known as heart failure with reduced ejection fraction, has been established through clinical trials and is formulated into guidelines to standardize the diagnosis and treatment. The premise of pharmacologic therapy in heart failure with reduced ejection fraction is aimed primarily at interrupting the neurohormonal cascade that is responsible for altering left ventricular shape and function. This is the first in a series of articles to describe the pharmacologic agents in the guidelines that impact the morbidity and mortality associated with heart failure. Angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and vasodilators will be presented in the context of the mechanism of action in heart failure, investigational trials that showed beneficial effects, and the practical application for clinical use.

Effects of Shenmai injection and its bioactive components following ischemia/reperfusion in cardiomyocytes

The aim of the present study was to determine whether the myocardial protective function of Shenmai injection (SM) during ischemia/reperfusion (I/R) is attributable to its regulation of intracellular calcium (Ca²⁺) and phospholamban (PLB) levels. Cultured neonatal Sprague Dawley rat cardiomyocytes were used to compare the effects of normoxia, total saponins of Panax ginseng (TSPG), ginsenoside Rg1 (Rg1) and SM treatments in rat myocardial cells following I/R. For each of these treatment groups, the mRNA and protein levels of PLB and the sarco/endoplasmic reticulum Ca²⁺ ATPase (SERCA) were evaluated, in addition to the cytoplasmic Ca²⁺ concentration [Ca²⁺]_i and the rate of apoptosis. The results indicated that I/R markedly decreased phosphorylated PLB and SERCA expression and that SM was able to mitigate this effect, while TPSG and Rg1 were not. Furthermore, SM appeared to prevent aberrant apoptosis and restore the depleted [Ca²⁺]_i resulting from I/R. The protective efficacy of SM against heart disease following I/R may, therefore, be due in part to its effect on intracellular Ca²⁺ homeostasis. SM may exert its protective effects by relieving PLB inhibition, and the pharmacodynamic actions of SM appear to be significantly more effective than those of its bioreactive components, TPSG and Rgl.

Modulation of haemodynamics, endogeneous antioxidant enzymes, and pathophysiological changes by selective inhibition of angiotensin II type 1 receptors in pressureoverload rats

Background

Constriction of the thoracic or abdominal aorta provides an experimental model of pressure-overload cardiac hypertrophy. Blockade of AT₁ receptors is beneficial in preventing target-organ damage in hypertension.

Objective

To examine the effect of angiotensin II receptor antagonists on blood pressure, endogenous antioxidant enzyme and histopathological changes in pressure-overload rats.

Methods

Pressure overload was produced by abdominal aortic banding (AAB) using a blunt 22-guage needle in male rats as a model of cardiac hypertrophy. After surgery, the AAB-induced hypertension (AABIH) rats were treated with losartan 40 mg/kg/day, candesartan 10 mg/kg/day, irbesartan 10 mg/kg/day per os for 16 weeks. At 16 weeks of surgery, the rats were observed for general characteristics and mortality, and we determined non-invasive blood pressure (NIBP), endogenous antioxidant enzyme catalase and superoxide dismutase (SOD) activities, and histology of the target organs.

Results

In the AABIH group, significant increase in systolic blood pressure was observed from weeks 3 to 16 compared with the control group, along with reduced serum catalase and SOD activities. The treated groups showed significant reduction in systolic BP and increase in serum SOD and catalase activities. The histological changes induced in the target organs, namely heart, liver, kidneys and thoracic aorta in the AABIH rats were attenuated in the treated rats.

Conclusion

Blockade of the AT₁ receptor caused an improvement in the myocardial antioxidant reserve and decreased oxidative stress in the hypertensive rats, which was evidenced by the protection observed in the treatment groups.

Prevention of remodeling in congestive heart failure due to myocardial infarction by blockade of the renin–angiotensin system

Ventricular remodeling subsequent to myocardial infarction (MI) is a complex process and is considered to be a major determinant of the clinical course of congestive heart failure (CHF). Emerging evidence suggests that activation of the renin-angiotensin system (RAS) plays an important role in post-MI ventricular remodeling; however, it is becoming clear that this is one of several neurohumoral systems that are activated in CHF. Blockade of RAS by angiotensin-converting enzyme inhibitors or angiotensin II type 1 receptor antagonists attenuates the ventricular dysfunction, but the effects of individual drugs in reducing the morbidity and mortality in CHF patients are variable. Furthermore, there is a difference of opinion as to the time of initiation of therapy with RAS blockers after the onset of MI. Since blockade of RAS partially improves cardiac function, it is suggested that a combination therapy involving RAS blockers (angiotensin-converting enzyme inhibitors or angiotensin II type 1 receptor antagonists) and agents that affect other neurohumoral systems may prove useful for improved treatment of CHF. Although activation of RAS has been shown to promote oxidative stress in experimental studies, the use of antioxidant therapy in CHF patients is controversial. Recent experimental studies have shown that ventricular remodeling in CHF is associated with remodeling of subcellular organelles such as sarcolemma, sarcoplasmic reticulum, myofibrils and extracellular matrix in terms of their molecular structure and composition. Since attenuation of remodeling in one and/or more subcellular organelles by different agents may prevent the progression of CHF, it is a challenge to develop specific drugs affecting molecular mechanisms associated with subcellular remodeling for the improved therapy of CHF.

Astragalosides rescue both cardiac function and sarcoplasmic reticulum Ca²⁺ transport in rats with chronic heart failure

The study investigated the beneficial effects of astragalosides (AS) on cardiac performance in rats with chronic heart failure. Chronic heart failure was produced by left anterior descending coronary artery ligation, and the therapeutic efficacy of astragalosides at 10, 20 and 40 mg/kg was evaluated. Five weeks after the operation, cardiac function was deficient and sarcoplasmic reticulum Ca²⁺-ATPase (SERCA) activity was significantly reduced. Moreover, SERCA mRNA decreased, while expression of the SERCA down-regulator phospholamban (PLB) was significantly increased. Phosphorylated phospholamban (P-PLB), the form that does not inhibit SERCA, was also reduced by chronic heart failure. Treatment with AS improved left ventricle function and cardiac structure, reversed the depression of SERCA activity, and increased P-PLB. These results suggest that the cardioprotective effect of AS may be due to the increase in P-PLB protein, which disinhibits SERCA activity. Rescue of sarcoplasmic reticulum Ca²⁺ cycling by astragalosides could normalize excitation-contraction coupling and improve overall cardiac function.

ACE inhibitors - angiotensin II receptor antagonists: A useful combination therapy for ischemic heart disease

Morbidity and mortality from cardiovascular diseases are still high, even with the use of the best available therapies. There is mounting evidence that excessive renin-angiotensin system activation triggers much of the damaging and progressive nature of cardiovascular and kidney diseases through expression of angiotensin II. Moreover, angiotensin II play a major role in the development of end organ damage through a variety of inflammatory mechanisms. Today, angiotensins-converting enzyme (ACE) inhibitors and angiotensin II receptor antagonists have clearly demonstrated their efficacy in preventing target organ damage and in reducing cardiovascular morbidity and mortality in ischemic heart disease (IHD). Moreover, the development of angiotensin II receptor antagonists has enabled a large gain in tolerability and safety. Several clinical trials have firmly established that these drugs act on the renin–angiotensin system, reducing the incidence of coronary events with monotherapy and combination therapy. In this review we summarize the role mono- and combined therapy of ACE inhibitors and angiotensin II receptor antagonists play in ischemic heart disease. In this respect the review will improve ideas for developing new formulations with combinations of these drugs in the future.

Large animal models of heart failure: a critical link in the translation of basic science to clinical practice

Congestive heart failure (HF) is a clinical syndrome, with hallmarks of fatigue and dyspnea, that continues to be highly prevalent and morbid. Because of the growing burden of HF as the population ages, the need to develop new pharmacological treatments and therapeutic interventions is of paramount importance. Common pathophysiologic features of HF include changes in left ventricle structure, function, and neurohormonal activation. The recapitulation of the HF phenotype in large animal models can allow for the translation of basic science discoveries into clinical therapies. Models of myocardial infarction/ischemia, ischemic cardiomyopathy, ventricular pressure and volume overload, and pacing-induced dilated cardiomyopathy have been created in dogs, pigs, and sheep for the investigation of HF and potential therapies. Large animal models recapitulating the clinical HF phenotype and translating basic science to clinical applications have successfully traveled the journey from bench to bedside. Undoubtedly, large animal models of HF will continue to play a crucial role in the elucidation of biological pathways involved in HF and the development and refinement of HF therapies.

Basis for the preferential activation of cardiac sympathetic nerve activity in heart failure

In heart failure (HF), sympathetic nerve activity is increased. Measurements in HF patients of cardiac norepinephrine spillover, reflecting cardiac sympathetic nerve activity (CSNA), indicate that it is increased earlier and to a greater extent than sympathetic activity to other organs. This has important consequences because it worsens prognosis, provoking arrhythmias and sudden death. To elucidate the mechanisms responsible for the activation of CSNA in HF, we made simultaneous direct neural recordings of CSNA and renal SNA (RSNA) in two groups of conscious sheep: normal animals and animals in HF induced by chronic, rapid ventricular pacing. In normal animals, the level of activity, measured as burst incidence (bursts of pulse related activity/100 heart beats), was significantly lower for CSNA (30 +/- 5%) than for RSNA (94 +/- 2%). Furthermore, the resting level of CSNA, relative to its maximum achieved while baroreceptors were unloaded by reducing arterial pressure, was set at a much lower percentage than RSNA. In HF, burst incidence of CSNA increased from 30 to 91%, whereas burst incidence of RSNA remained unaltered at 95%. The sensitivity of the control of both CSNA and RSNA by the arterial baroreflex remained unchanged in HF. These data show that, in the normal state, the resting level of CSNA is set at a lower level than RSNA, but in HF, the resting levels of SNA to both organs are close to their maxima. This finding provides an explanation for the preferential increase in cardiac norepinephrine spillover observed in HF.

Expression of renin-angiotensin system and peroxisome proliferator-activated receptors in alcoholic cardiomyopathy

BACKGROUND

Alcoholic cardiomyopathy (ACM) develops in response to chronic alcohol intake and it is hypothesized that activation of the renin-angiotensin system (RAS) and disorders in energy metabolism may play important roles in its onset. Given that the expression of peroxisome proliferator-activated receptors (PPARalpha and PPARgamma) changes with alterations in cardiac metabolism and myocardial remodeling, this study was designed to test the hypothesis that protein expression of PPARalpha and PPARgamma is correlated with RAS activation in ACM.

METHODS

For the first experiment, rats were divided into 3 groups: 30 received alcohol (intragastric administration with ad libitum drinking), 30 received alcohol and irbesartan (5 mg/kg/d, p.o.), and 30 served as controls. RAS activity and protein expression of PPARalpha and PPARgamma were evaluated in rats following 6 months of alcohol feeding using radioimmunoassay, reverse transcriptase PCR, and Western blot methods. For the second experiment, rats were divided into 4 groups: 10 rats received alcohol/irbesartan (5 mg/kg/d, p.o.)/PD98059 (methyl ethyl ketone [MEK]-1 inhibitor) (0.3 mg/kg/d, p.o.), 10 rats received alcohol/PD98059, 10 rats received alcohol/irbesartan, and 10 rats received alcohol alone. Myocardial PPARalpha and PPARgamma protein expression was detected following 6 months of alcohol feeding using Western blot method.

RESULTS

Compared with controls, myocardial angiotensin (Ang) I, Ang II, and renin levels were progressively increased at 2, 4, and 6 months of alcohol intake. mRNA expression of renin, angiotensinogen, angiotensin-converting enzyme (ACE), and AT1 was increased at 6 months. Moreover, activated RAS downregulated PPARalpha and upregulated PPARgamma protein expression as ACM progressed. Finally, extracellular signal regulated kinase 1 and 2 (ERK1/2) was shown to play a key role in the regulation of protein expression of PPARalpha and PPARgamma.

CONCLUSION

These results suggest that RAS is activated during the development of ACM. Moreover, ERK1/2 plays a key role in the regulation of protein expression of PPARalpha and PPARgamma by RAS in ACM.

Valsartan in the treatment of heart attack survivors

Survivors of myocardial infarction (MI) are at high risk of disability and death. This is due to infarct-related complications such as heart failure, cardiac remodeling with progressive ventricular dilation, dysfunction, and hypertrophy, and arrhythmias including ventricular and atrial fibrillation. Angiotensin (Ang) II, the major effector molecule of the renin–angiotensin–aldosterone system (RAAS) is a major contributor to these complications. RAAS inhibition, with angiotensin-converting enzyme (ACE) inhibitors were first shown to reduce mortality and morbidity after MI. Subsequently, angiotensin receptor blockers (ARBs), that produce more complete blockade of the effects of Ang II at the Ang II type 1 (AT₁) receptor, were introduced and the ARB valsartan was shown to be as effective as an ACE inhibitor in reducing mortality and morbidity in high-risk post-MI suvivors with left ventricular (LV) systolic dysfunction and and/or heart failure and in heart failure patients, respectively, in two major trials (VALIANT and Val-HeFT). Both these trials used an ACE inhibitor as comparator on top of background therapy. Evidence favoring the use of valsartan for secondary prevention in post-MI survivors is reviewed.

AT2 receptor mediates the cardioprotective effects of AT1 receptor antagonist in post-myocardial infarction remodeling

There are two subtypes of angiotensin (Ang) II receptors, AT1R and AT2R. It is established that clinical use of specific AT1R blocker (ARB) improves the long-term prognosis of heart failure. However, scientific basis for such effects of ARB is incompletely understood. The present study was designed to determine whether ARB inhibits the left ventricular (LV) remodeling that occurs early after myocardial infarction (MI) and whether the benefit of ARB is mediated by blockade of AT1R itself or by stimulation of AT2R resulting from AT1R blockade. MI was induced in AT2R-knockout mice and wild-type mice. Administration of valsartan, an ARB, or vehicle was started soon after the surgery and continued for two weeks. Infarction caused significant increase in end diastolic and end systolic LV dimensions, LV/body weight ratio, and myocyte cross-sectional area (MCSA) in both strains to a similar extent. Lung/body weight ratio, an index of pulmonary congestion, was also significantly increased in both strains, but the magnitude of increase was significantly larger in knockout mice. Valsartan significantly reduced LV dimensions, LV/body weight ratio, MCSA, and lung/body weight ratio in wild-type mice. In knockout mice, however, valsartan failed to inhibit the increases in LV dimensions and LV/body weight ratio. After the treatment, lung/body weight ratio in the mutant strain was significantly larger than that in the wild-type mice. Valsartan attenuates acute phase post-infarction remodeling and ameliorates heart failure, and a large part of its cardioprotective effect was mediated by AT2R.

In vivo evaluation of the improved MCMS-0102 pacemaker with a rapid pacing mode for induction of experimental heart failure in animals

The MCMS-0102 cardiac pacemaker for rapid ventricular pacing to induce heart failure in animals has been improved in terms of miniaturization and performance. To determine the performance of the new MCMS-0102, six devices were implanted in beagle dogs, and two of these devices were reimplanted for continued pacing in a total of eight beagle dogs. The hearts were paced at 260 beats per minute for 4 weeks (P group: n = 8). The hemodynamic status of the P group was examined and compared with nonpaced dogs (NP group: n = 8). The neurohumoral status of the P group was evaluated before and after rapid pacing. Stable operation of the six devices during rapid pacing was confirmed using the telemetry system. Postmortem examinations revealed features similar to clinical heart failure characterized by massive ascites, pleural effusion, cardiomegaly, and liver congestion in all the paced dogs. Cardiac output was 1.1 +/- 0.2 l/min in the NP group and 0.5 +/- 0.1 l/min in the P group (P < 0.0001). The left atrial pressure and the central venous pressure of the P group and the NP group were 23 +/- 6 versus 6 +/- 2 mmHg (P < 0.0001) and 10 +/- 3 versus 4 +/- 3 mmHg (P < 0.001), respectively. In the paced dogs, plasma renin activity increased from 0.5 +/- 0.4 to 8.5 +/- 7.4 ng/ml/h (P < 0.05) and atrial natriuretic peptide levels increased from 69 +/- 41 to 229 +/- 72 pg/ml (P < 0.001). The improved MCMS-0102 was successfully implanted in beagle dogs and it succeeded in inducing the congestive heart failure model.

Angiotensin II receptor blockade and ventricular remodelling

Cardiac remodelling is the expression of molecular, cellular and interstitial changes in response to cardiac injury, manifesting as adverse alterations in the size, shape and function of the ventricle. Several clinical studies have documented significant elevations in the levels of renin, angiotensin II (Ang II) and aldosterone attending acute myocardial infarction and/or congestive heart failure. Similar to catecholamines, markedly elevated activity of the renin-angiotensin-aldosterone system (RAAS) is associated with poor prognosis. The effects of Ang II upon cardiac tissue are related to two primary receptors, Ang II type 1 (AT1) and Ang II type 2 (AT2). The AT1-receptor appears to mediate many of the deleterious effects of chronic RAAS activity, while the AT2-receptor is increasingly shown to have potential cardioprotective effects. Attenuating the deleterious effects of sustained Ang II stimulation can be achieved by direct inhibition of angiotensin- converting enzyme (ACE) and/or direct antagonism of AT receptors. ACE inhibition reduces left ventricular (LV) volumes, retards the progression of LV dilatation and hypertrophy and increases systolic function in systolic dysfunction. By blocking at the receptor level, Ang II receptor blockers (ARBs) provide an alternative and more direct approach to inhibiting the effects of Ang II; however, data relating to their effects upon ventricular remodelling, whether used in isolation or in combination with ACE inhibitors (ACE-Is), are less convincing. Data arising from several recent clinical trials suggest that simultaneous use of ACE-Is and ARBs maybe of more benefit in attenuating ventricular remodelling than either agent alone.

Combined angiotensin receptor blocker and ACE inhibitor on myocardial fibrosis and left ventricular stiffness in dogs with heart failure

Angiotensin receptor blocker (ARB) and angiotensin-converting enzyme (ACE) inhibitor (ACEI) each act in a different manner to prevent myocardial fibrosis and left ventricular (LV) stiffness in animals with pathways in the heart for generating ANG II as well as ACE. A model of pacing-induced congestive heart failure (CHF) was used to test the central hypothesis that ARB + ACEI prevents myocardial fibrosis and decreases LV stiffness to a greater extent than ARB or ACEI alone. Thirty-five dogs were assigned to the following treatment protocols on the 8th day of a 4-wk pacing schedule: 1) rapid ventricular pacing, 2) ARB (candesartan cilexetil, 1.5 mg.kg(-1).day(-1)) with pacing, 3) ACEI (enalapril, 1.9 mg.kg(-1).day(-1)) with pacing, 4) ARB (candesartan cilexetil, 0.75 mg.kg(-1).day(-1)) + ACEI (enalapril, 0.95 mg.kg(-1).day(-1)) with pacing, and 5) sham operation. The LV stiffness coefficient was significantly increased after rapid pacing but was significantly lower with ARB + ACEI than with ARB or ACEI alone. The collagen volume fraction and mRNA levels of collagen I and III, which were increased by rapid pacing, were significantly lower with ARB + ACEI than with ARB or ACEI alone. Thus ARB + ACEI prevents myocardial fibrosis and decreases LV stiffness during the progression of CHF compared with ARB or ACEI alone.

Atrial Ultrastructural Changes During Experimental Atrial Tachycardia Depend on High Ventricular Rate

INTRODUCTION

Atrial structural and electrophysiologic changes occur during atrial tachycardia. The role of high ventricular rate in these processes remains to be established.

METHODS AND RESULTS

Six goats were subjected to 4 weeks of rapid atrioventricular (AV) pacing at an atrial and ventricular rate of 240 beats/min, resulting in development of congestive heart failure. In another five goats, AV block was created. These goats then were subjected to 4 weeks of atrial pacing, also at 240 beats/min while the ventricular rate was kept low and regular at 80 beats/min (A-paced). Pacing was interrupted only for measurement of atrial effective refractory period and right atrial diameter. The ultrastructure of both atria was examined by light and electron microscopy, including quantification of the percentage of atrial extracellular matrix (%ECM). A group of six goats served as controls. In the AV-paced group, severe structural remodeling occurred in the atria, including severe loss of sarcomeres, glycogen accumulation, disruption of sarcoplasmic reticulum, and appearance of numerous small mitochondria and nuclei with homogeneously distributed chromatin. In contrast, structural changes were virtually absent in the atria of A-paced goats. Only a redistribution of nuclear chromatin and the appearance of numerous mitochondria were observed. The ultrastructure was normal in control animals. The%ECM was increased in AV-paced goats (29%) compared to A-paced animals (18%) and controls (17%) (P < 0.05). Finally, right atrial diameter increased by 51% in AV-paced goats but was unchanged in A-paced goats (P < 0.05). In both experimental groups, atrial effective refractory period shortened during pacing.

CONCLUSION

Structural remodeling during chronic atrial tachycardia is related to the concomitant presence of a high ventricular rate and hence the occurrence of congestive heart failure rather than a high atrial rate. Electrical remodeling can occur in the absence of significant structural changes.

Furosemide and the progression of left ventricular dysfunction in experimental heart failure

OBJECTIVES

We tested the hypothesis that furosemide accelerates the progression of left ventricular systolic dysfunction in a tachycardia-induced porcine model of heart failure.

BACKGROUND

Furosemide activates the renin-angiotensin-aldosterone system in patients with congestive heart failure (CHF). Such activation may contribute to CHF progression, but prospective data are lacking.

METHODS

Thirty-two Yorkshire pigs were randomized to furosemide (1 mg/kg intramuscularly daily, mean 16.1 +/- 0.9 mg) or placebo. Thereafter, a pacing model of heart failure was utilized to produce systolic dysfunction in both sets of animals (fractional shortening <0.16 by echocardiogram). The goal was to determine if furosemide would accelerate the progression of left ventricular dysfunction in the "treated" group. After sacrifice, sodium-calcium exchanger currents and their responsiveness to isoproterenol were measured during voltage clamp. All investigators were blinded to treatment assignment.

RESULTS

Furosemide shortened the time to left ventricular dysfunction (35.1 +/- 5.1 days in placebo versus 21.4 +/- 3.2 days for furosemide animals; p = 0.038, log-rank test). By day 14, aldosterone levels were significantly higher in furosemide animals (43.0 +/- 11.8 ng/dl vs. 17.6 +/- 4.5 ng/dl; p < 0.05). Serum sodium was reduced (133.0 +/- 0.9 mmol/l furosemide vs. 135.7 +/- 0.8 mmol/l placebo; p < 0.05), but no difference in norepinephrine, potassium, magnesium, creatinine, or urea nitrogen was present. Basal sodium-calcium exchanger currents were significantly increased and isoproterenol responsiveness depressed by furosemide.

CONCLUSIONS

Tachycardic pigs given furosemide had significant acceleration of both contractile and metabolic features of CHF, including left ventricular systolic dysfunction, elevated serum aldosterone levels, and altered calcium handling in a controlled experimental model of heart failure.

Unequal effects of renin-angiotensin system inhibitors in acute cardiac dysfunction induced by isoproterenol

Several clinical trials have demonstrated that angiotensin-converting enzyme inhibitor (ACEI) and angiotensin II type 1 receptor blocker (ARB) are equally effective in the treatment of chronic heart failure. However, this has not been confirmed for acute cardiac dysfunction. We examined whether ACEI or ARB prevents isoproterenol-induced acute left ventricular (LV) dysfunction in dogs. LV dysfunction induced by a large dose of isoproterenol (1 microg.kg(-1).min(-1), 3-h infusion) was compared in dogs treated with ACEI (temocaprilat) or ARB (olmesartan). Atrial pacing induced a constant heart rate and use of adjustable aortic banding provided a nearly constant afterload. LV systolic function (LV dP/dt, fractional shortening, and ejection fraction) and diastolic function (tau and LV end-diastolic pressure) were significantly deteriorated after isoproterenol infusion. The LV dysfunction was almost totally prevented by ARB but was only partially prevented by ACEI. The partial effect of ACEI was complemented by cotreatment with HOE-140, a bradykinin B2 receptor antagonist. At baseline, the response to low doses of isoproterenol was significantly attenuated by ACEI but not by ARB, and the ACEI-induced attenuation was totally abolished by cotreatment with HOE-140. The response to isoproterenol was significantly attenuated after 3 h of excess isoproterenol loading, and it was almost completely preserved by ARB but not by ACEI. In conclusion, acute LV dysfunction and beta-adrenergic desensitization induced by excess isoproterenol administration were almost totally prevented by ARB but only partially prevented by ACEI. These differences were attributable at least in part to bradykinin pathways activated by ACEI administration in acute LV dysfunction.

Candesartan Prevents Myocardial Fibrosis during Progression of Congestive Heart Failure

BACKGROUND

The goal of this study was to determine whether an Angiotensin II receptor antagonist, candesartan, prevents myocardial fibrosis more effectively than enalapril in animals with a non-ACE pathway during the progression of congestive heart failure (CHF).

METHODS AND RESULTS

Dogs were randomly assigned to one of four groups: (1) rapid ventricular pacing (240 bpm); (2) concomitant candesartan cilexetil (1.5 mg/kg/d) and rapid pacing; (3) concomitant enalapril (1.9 mg/kg/d) and rapid pacing; (4) sham-operated control. The expression of collagen type I & III mRNA and the collagen volume fraction, which were significantly increased in the pacing-only group, were suppressed by both treatments; it was lower in the candesartan than the enalapril group. Although there were no differences in the LV stiffness coefficient (beta) among all pacing groups, the absolute changes in beta from the control values were smaller in the candesartan group, but not the enalapril group, compared with the rapid-pacing-only group.

CONCLUSIONS

The present study demonstrates that in animals with a non-ACE pathway, candesartan suppressed myocardial fibrosis during the progression of CHF in comparison with enalapril. Furthermore, candesartan prevented an increase in LV stiffness. These findings imply potential clinical applications for candesartan in the management of CHF to prevent myocardial fibrosis. Further prospective evaluation and clinical study will be necessary before deciding on the net benefits of candesartan in comparison to enalapril.

Reversal of heart failure remodeling: is it maintained?

BACKGROUND

Reversal of heart failure remodeling has been observed with intensive heart failure therapy.

HYPOTHESIS

We hypothesized that reversal of heart failure remodeling may not be sustained in long-term follow-up.

METHODS

Sixty-one sequential patients with heart failure and left ventricular ejection fraction < or = 35%, who improved their ejection fraction by > or = 10% over baseline at follow-up, were prospectively followed and retrospectively analyzed. Each patient underwent echocardiography at baseline and biannually thereafter.

RESULTS

In all patients, left ventricular ejection fraction increased from 18 +/- 7% to 42 +/- 12% on uptitrated medical therapy. At follow-up over 20 +/- 8 (+/- standard deviation) months, this improvement was sustained in 38 patients ("Improved"). A relapse in remodeling occurred in the remaining 23 patients ("Relapsed"), with ejection fraction falling to 24 +/- 7%. For Improved and Relapsed patients, baseline echocardiographic and clinical parameters were equivalent. However, Improved patients tended to be younger, with shorter heart failure duration. Improved patients had more effective improvement in ejection fraction than Relapsed patients (45 +/- 13% vs. 36 +/- 8%, p = 0.005), with greater reductions in chamber size and mitral regurgitation.

CONCLUSION

Reversal of heart failure remodeling may be sustained in only two-thirds of patients at long-term follow-up. In contrast to Relapsed patients, Improved patients tended to be younger, with shorter heart failure duration and a more complete recovery of left ventricular systolic function.

Attenuation of heart failure due to coronary stenosis by ACE inhibitor and angiotensin receptor blocker

It is not known how the angiotensin-converting enzyme (ACE) inhibitor and angiotensin II receptor blocker (ARB) attenuate heart failure (HF) in viable ischemic hearts. To assess HF in a rat coronary stenosis (CS) model, we administered vehicle and quinapril or candesartan (or both) orally for 12 wk. Compared with the sham group, the vehicle group showed impaired myocardial perfusion, impaired coronary endothelial nitric oxide (NO) function in vitro, exhausted myocardial mitochondrial respiration, larger left ventricular (LV) dimensions and lower ejection fraction, lower LV rate of pressure development over time (dP/dt), lower slopes of LV end-systolic pressure-dimension relations (ESPDRs), and increased myocardial fibrosis. Treatment with quinapril or candesartan ameliorated these parameters without modifying the epicardial CS severity. Moreover, their combination maintained similar myocardial perfusion, despite a trend toward lower blood pressure, and showed distinctive neurohumoral modulation, normalized mitochondrial respiration, and increased ESPDR slopes. Thus improved myocardial blood flow and coronary flow reserve by quinapril or candesartan are the key to alleviate CS-induced HF, and their combination may have a therapeutic significance partly through ameliorated mitochondrial respiration and improved LV systolic function.

Adding angiotensin II type 1 receptor blockade to angiotensin-converting enzyme inhibition limits myocyte remodeling after myocardial infarction

BACKGROUND

Adding angiotensin II type 1 receptor blockade (ARB) to angiotensin-converting enzyme inhibition (ACEI) further attenuates left ventricular (LV) remodeling in an ovine model of myocardial infarction (MI). We hypothesized that combined therapy with ACEI and ARB (CT) would be additive in the limitation of the myocyte hypertrophy and dysfunction that occurs in untreated adjacent noninfarcted regions during remodeling.

METHODS AND RESULTS

Nineteen sheep underwent coronary ligation to create a moderate-sized anteroapical infarction. Post-MI day 2, sheep were randomized to therapy with ramipril (ACEI, n = 5) or ramipril plus losartan (CT, n = 6) or none (untreated, n = 8). Infarct size was similar between groups. At 8 weeks post-MI, myocytes were isolated from regions adjacent to and remote from the infarct to measure morphometric indices (cell volume, length, cross-sectional area, width) and parameters of contraction (% shortening and -dL/dt, rate of shortening) and relaxation (+dL/dt [rate of relengthening] and TR 70% [time for 70% relengthening]). Volume % collagen was measured from adjacent and remote regions. Adjacent myocyte volume was different between groups (2.5 +/- 0.1 x 10(4) microm(3) in CT, 3.0 +/- 0.4 x 10(4) microm(3) in ACEI, 3.5 +/- 0.2 x 10(4) microm(3) in untreated, analysis of variance [ANOVA] P =.001) as was length (158 +/- 4 microm, 161 +/- 9 microm, 189 +/- 8 microm, respectively, ANOVA P <.001). Adjacent cell volume and length in CT were lower than untreated (P <.05). Percent shortening and -dL/dt of isolated adjacent myocytes were improved with both ACEI (7.9 +/- 0.3%, -131 +/- 6 microm/sec, P <.05) and CT (7.7 +/- 0.3%, -144 +/- 8 microm/sec, P <.05) compared with no therapy (6.4 +/- 0.4%, -104 +/- 7 microm/sec), as was both +dL/dt and TR 70%. No between-group difference in volume % collagen was found in adjacent or remote regions.

CONCLUSION

Compared with ACEI alone, the addition of ARB further limits adjacent noninfarcted myocyte hypertrophy during post-MI LV remodeling. Both ACEI alone and CT preserve isolated unloaded myocyte function, but neither significantly reduce interstitial collagen. The additional benefit of ARB on regional and global function in vivo may also be due to other factors including regional load.

Effect of Valsartan on hospitalization: results from Val-HeFT

BACKGROUND

Although current therapies have improved heart failure (HF) outcome, hospitalizations continue at high rates. The Valsartan Heart Failure Trial (Val-HeFT) showed that valsartan reduced the risk of first worsening HF hospitalization by 27.5% versus placebo (P <.001). This article analyzes all-cause and investigator-assessed HF hospitalization in Val-HeFT overall and in subgroups defined by preexisting HF therapy.

METHODS

Val-HeFT was a randomized, double-blind parallel-arm study in which HF patients (New York Heart Association class II-IV) received either valsartan (n = 2511, force-titrated to 160 mg twice daily) or placebo (n = 2499) in addition to prescribed HF therapy. Total and per patient-year investigator-assessed hospitalizations (all-cause or HF) were analyzed according to prescribed therapy at baseline (angiotensin-converting enzyme inhibitors [ACEI] and beta-blockers [BB]).

RESULTS

Hospitalization for worsening HF accounted for 35% of all hospitalizations. There were 2856 and 3106 total all-cause hospitalizations in the valsartan and placebo groups, respectively, an 8% reduction (P =.145). Valsartan significantly reduced the overall number of investigator-assessed HF hospitalizations (-22.4%, P =.002) and reduced HF hospitalizations in the combination therapy subgroups (significant for ACEI+/BB- P =.003 and ACEI-/BB- P =.028) except those receiving both ACEI and BB. The benefit of valsartan versus placebo was more pronounced in reducing the number of patients with recurrent HF hospitalization (-20.6%) than single hospitalizations (-8.7%).

CONCLUSIONS

Addition of valsartan to prescribed HF therapy demonstrated significant reductions in HF hospitalizations and was particularly beneficial in reducing recurrent HF hospitalization.

Addition of angiotensin II receptor antagonist to an ACE inhibitor in heart failure improves cardiovascular function by a bradykinin-mediated mechanism

Whether cardiovascular responses to bradykinin are augmented by additional treatment with angiotensin II receptor antagonism (ATRA) to angiotensin-converting enzyme inhibition (ACEI) in congestive heart failure (CHF) is unknown. To clarify the level and functional effects of endogenous bradykinin in CHF with combined ATRA and ACEI, 35 dogs were assigned to the following treatment protocols: 1). rapid ventricular pacing (240 bpm), 2). concomitant ATRA (TCV116, 1.5 mg x kg-1.day-1) and rapid pacing, 3). concomitant ACEI (enalapril 1.9 mg x kg-1.day-1) and rapid pacing, 4). concomitant combined ATRA (TCV116, 0.75 mg x kg-1.day-1) and ACEI (enalapril 0.95 mg x kg-1.day-1) and rapid pacing, and 5). sham-operated control. Plasma bradykinin levels were increased and B(2) receptors were synergistically upregulated in CHF groups treated with combined ATRA and ACEI compared with those treated with ATRA or ACEI alone. HOE-140 (0.3 mg/kg), a bradykinin B(2) receptor antagonist, produced an increase in total systemic resistance and a decrease in left ventricular contractility in CHF with combined therapy compared with either monotherapy. Thus, endogenous bradykinin partially contributes to the synergistic improvement of cardiovascular function in CHF with additional treatment with ATRA to ACEI.

[Addition of an angiotensin II receptor blocker to maximal dose of ACE inhibitors in heart failure]

In heart failure, the benefits of adding angiotensin-receptor blockade to ACE inhibitors have been studied only with submaximal doses of ACE inhibitors. We included 20 patients (LVEF 24 7%, NYHA II-III), with no clinical or therapeutic variations in the previous three months, who were receiving maximal doses of ACE inhibitors. We added losartan 50 mg once a day. At six months, SBP decreased (115 8 vs. 106 9 mmHg; p = 0.001), LVEF increased (24.4 7 vs. 34.1 7%; p < 0.001), ventricular end-diastolic volumes decreased (220 58 vs 190 46 ml; p = 0.007), and SPAP decreased (43 8 vs. 35 7 mmHg; p < 0.001). Seven patients improved one degree on the NYHA scale (p = 0.004), but VO2max did not change (20.8 5.2 vs. 21.8 5.0 ml/kg/min, p = 0.120). Plasma levels of norepinephrine, at rest and maximal exercise, brain natriuretic peptide, and renin were similar. After maximum ACE inhibitor doses, the addition of losartan is safe and associated with an improvement in ventricular function and NYHA functional class, but with no change in neurohormonal status.

Systemic and regional hemodynamic and cardiac remodeling effects of candesartan in dilated cardiomyopathic hamsters with advanced congestive heart failure

The effects of the selective angiotensin II type 1 receptor antagonist candesartan on cardiac, systemic, and regional hemodynamics and on cardiac, pulmonary, and hepatic histomorphometry were investigated in cardiomyopathic hamsters (CMHs), Bio TO-2 dilated strain, with advanced congestive heart failure (CHF). Two groups were treated orally with candesartan cilexetil at 22 or 50 mg/kg/d from 190 days of age and compared with a control group (38 animals/group). Investigations were performed at 225, 255, and 285 days of age. Left ventricle (LV) and systemic blood pressures and cardiac output and mesenteric and femoral blood flows were measured in anesthetized animals. LV cavity area, LV and right ventricle (RV) wall thickness and collagen density, and pulmonary and hepatic congestion were assessed. Compared with the control group, candesartan did not modify cardiac hemodynamics but significantly and dose-dependently decreased systemic vascular resistances (on average: -23 and -32% after 22 and 50 mg/kg, respectively) and increased stroke volume (+32 and +42%) and cardiac output (+27 and +34%). Candesartan did not modify mesenteric vascular resistances and blood flow but significantly and dose-dependently decreased femoral vascular resistances (-19 and -33%) and increased femoral blood flow (+33 and +43%). Candesartan significantly decreased LV cavity area (-14 and -8%) and LV (-15 and -31%) and RV (-16 and -24%) collagen density but did not modify LV and RV wall thickness. Candesartan decreased pulmonary congestion at 255 and 285 days of age but did not modify hepatic congestion. In CMHs with advanced CHF, candesartan cilexetil improves systemic and femoral hemodynamics, partly reverses cardiac remodeling, and decreases pulmonary congestion.

Nitric oxide production is maintained in exercising swine with chronic left ventricular dysfunction

Left ventricular (LV) dysfunction caused by myocardial infarction (MI) is accompanied by endothelial dysfunction, most notably a loss of nitric oxide (NO) availability. We tested the hypothesis that endothelial dysfunction contributes to impaired tissue perfusion during increased metabolic demands as produced by exercise, and we determined the contribution of NO to regulation of regional systemic, pulmonary, and coronary vasomotor tone in exercising swine with LV dysfunction produced by a 2- to 3-wk-old MI. LV dysfunction resulted in blunted systemic and coronary vasodilator responses to ATP, whereas the responses to nitroprusside were maintained. Exercise resulted in blunted systemic and pulmonary vasodilator responses in MI that resembled the vasodilator responses in normal (N) swine following blockade of NO synthase with N(omega)-nitro-L-arginine (L-NNA, 20 mg/kg iv). However, L-NNA resulted in similar decreases in systemic (43 +/- 3% in N swine and 49 +/- 4% in MI swine), pulmonary (45 +/- 5% in N swine and 49 +/- 4% in MI swine), and coronary (28 +/- 4% in N and 35 +/- 3% in MI) vascular conductances in N and MI swine under resting conditions; similar effects were observed during treadmill exercise. Selective inhibition of inducible NO synthase with aminoguanidine (20 mg/kg iv) had no effect on vascular tone in MI. These findings indicate that while agonist-induced vasodilation is already blunted early after myocardial infarction, the contribution of endothelial NO synthase-derived NO to regulation of vascular tone under basal conditions and during exercise is maintained.

Cardiorenal effects of adenosine subtype 1 (A1) receptor inhibition in an experimental model of heart failure

BACKGROUND

Elaboration of a number of bioactive substances, including adenosine, occurs in heart failure (HF). Adenosine, through the adenosine subtype 1 (A1) receptor, can reduce renal perfusion pressure and glomerular filtration rate and increase tubular sodium reabsorption, which can affect natriuresis and aquaresis. Accordingly, the present study examined the acute effects of selective A1 receptor blockade on hemodynamics and renal function in a model of HF.

STUDY DESIGN

HF was induced in adult pigs (n = 19) by chronic pacing (240 beats/min for 3 weeks). The pigs were then instrumented for hemodynamic and renal function measurements. After baseline measurements were taken, pigs received either A1 block [ 1 mg/kg BG9719 (1,3-dipropyl-8-[2(5,6-epoxynorbornyl)]xanthine; n = 9)] or infusion of vehicle (n = 10), and measurements were repeated at intervals for up to 2 hours. Normal controls (n = 7) were included for comparison.

RESULTS

Cardiac output remained unchanged between the A1 block and vehicle groups throughout the study. Pulmonary vascular resistance fell 38% from baseline at 10 minutes post-A1 block in the HF group (p < 0.05) with no change in the vehicle group. At 10 minutes post-A1 block, urine flow increased sixfold and sodium excretion increased over 10-fold (for both, p < 0.05) with no change in the vehicle group. At 10 minutes post-A1 block, creatinine clearance increased with no change in the vehicle group. At 10 minutes post-A1 block, plasma renin activity had increased over threefold (p <0.05), and it returned to baseline levels by 30 minutes post-A1 block.

CONCLUSIONS

The unique findings from this study were threefold. First, increased A1 receptor activation contributes to renal mediated fluid retention in HF. Second, selective A1 blockade can induce diuresis without hemodynamic compromise and with possible benefit to pulmonary resistance in a model of HF. A1 blockade transiently increased plasma renin activity with no change in hemodynamics. These unique results suggest that selective A1 blockade can be a useful adjunctive diuretic in the setting of HF.

AT(1) and AT(2) receptor expression and blockade after acute ischemia-reperfusion in isolated working rat hearts

We assessed ANG II type 1 (AT(1)) and type 2 (AT(2)) receptor (R) expression and functional recovery after ischemia-reperfusion with or without AT(1)R/AT(2)R blockade in isolated working rat hearts. Groups of six hearts were subjected to global ischemia (30 min) followed by reperfusion (30 min) and exposed to no drug and no ischemia-reperfusion (control), ischemia-reperfusion and no drug, and ischemia-reperfusion with losartan (an AT(1)R antagonist; 1 micromol/l), PD-123319 (an AT(2)R antagonist; 0.3 micromol/l), N(6)-cyclohexyladenosine (CHA, a cardioprotective adenosine A(1) receptor agonist; 0.5 micromol/l as positive control), enalaprilat (an ANG-converting enzyme inhibitor; 1 micromol/l), PD-123319 + losartan, ANG II (1 nmol/l), or ANG II + losartan. Compared with controls, ischemia-reperfusion decreased AT(2)R protein (Western immunoblots) and mRNA (Northern immunoblots, RT-PCR) and impaired functional recovery. PD-123319 increased AT(2)R protein and mRNA and improved functional recovery. Losartan increased AT(1)R mRNA (but not AT(1)R/AT(2)R protein) and impaired recovery. Other groups (except CHA) did not improve recovery. The results suggest that, in isolated working hearts, AT(2)R plays a significant role in ischemia-reperfusion and AT(2)R blockade induces increased AT(2)R protein and cardioprotection.

Effect of angiotensin type I-receptor blockade on left ventricular remodeling in pressure overload hypertrophy

BACKGROUND

The renin-angiotensin system is involved in cardiac remodeling. In contrast to the well-recognized salutary effects of angiotensin-converting enzyme inhibition, the value of angiotensin II type I (AT(1))-receptor blockade on left ventricular (LV) hypertrophy and dysfunction is controversial.

METHODS AND RESULTS

Descending thoracic aorta-banded and sham-operated guinea pigs were given either losartan (30 mg x kg(-1) x day(-1) intraperitoneally) or vehicle for 8 weeks (n = 7 in each group). LV end-diastolic and end-systolic dimensions and wall thicknesses were measured echocardiographically, and LV fractional shortening, relative wall thickness, and LV mass normalized by body weight were calculated. Isolated heart function (Langendorff perfusion) was studied 8 weeks after surgery, and LV performance was assessed by maximum LV pressure and +/-dP/dt normalized by LV mass. Eight weeks after banding guinea pigs developed concentric LV hypertrophy and had decreased maximum LV pressure and +/-dP/dt normalized by LV mass; LV end-diastolic dimension and LV fractional shortening were unchanged. In band-operated guinea pigs treatment with losartan had no significant effects on any of these measurements.

CONCLUSIONS

In guinea pigs with descending aortic banding, treatment with losartan for 8 weeks neither attenuates progression of pressure overload hypertrophy nor significantly improves impaired mass-normalized pressure-derived indices of LV contraction and relaxation.

Beneficial effects of the Ca2+ sensitizer EMD 57033 in exercising pigs with infarction-induced chronic left ventricular dysfunction

1. It is unknown how cardiac stimulation by Ca(2+) sensitization modulates the cardiovascular response to exercise when left ventricular (LV) function is chronically depressed following a myocardial infarction. We therefore investigated the effects of EMD 57033 at rest and during exercise and compared these to those of the mixed Ca(2+)-sensitizer/phosphodiesterase-III inhibitor pimobendan. 2. Pigs were chronically instrumented for measurement of cardiovascular performance. At the time of instrumentation, infarction was produced by coronary artery ligation (MI, n=12). Studies in MI were performed in the awake state, 2 - 3 weeks after infarction. 3. MI were characterized by a lower resting cardiac output (18%), stroke volume (30%) and LVdP/dt(max) (18%), and a doubling of LV end-diastolic pressure, compared to normal pigs (N, n=13). 4. In 11 resting MI, intravenous EMD 57033 (0.2 - 0.8 mg kg(-1) min(-1)) increased LVdP/dt(max) (57+/-5%) and stroke volume (26+/-6%) with no effect on heart rate, LV filling pressure, and myocardial O(2)-consumption, similar to N. 5. In MI, the effects of EMD 57033 (0.4 mg kg(-1) min(-1), IV) on stroke volume and LVdP/dt(max) were maintained during treadmill exercise up to 85% of maximal heart rate, while heart rate was lower compared to control exercise (all P<0.05). In contrast, the effects of EMD57033 gradually waned in N at increasing intensity of exercise. 6. Compared to N, the cardiostimulatory effects of pimobendan (20 microg kg(-1) min(-1), IV) were blunted in MI both at rest and during exercise compared to N. 7. In conclusion, the positive inotropic actions of the Ca(2+) sensitizer EMD 57033 are unmitigated in resting and exercising MI compared to N, while those of the mixed Ca(2+)-sensitizer/phosphodiesterase-III inhibitor pimobendan are blunted.

Myocardial bradykinin following acute angiotensin-converting enzyme inhibition, AT1 receptor blockade, or combined inhibition in congestive heart failure

BACKGROUND

The present study examined the effects of acute angiotensin-converting enzyme inhibition (ACEI), AT(1) receptor blockade (AT(1) block), or combined treatment on in vitro and in vivo bradykinin (BK) levels.

METHODS

BK levels were measured in isolated porcine myocyte preparations (n = 13) in the presence of exogenous BK (10(-8) M); with an ACEI (benezaprilat; 0.1 mM) and BK; an AT(1) block (valsartan; 10(-5) M) and BK; and combined treatment and BK. In a second study, myocardial microdialysis was used to measure porcine interstitial BK levels in both normal (n = 14) and pacing-induced congestive heart failure (CHF) (240 beats/min, 3 weeks, n = 16) under the following conditions: baseline, following ACEI (benezaprilat, 0.0625 mg/kg) or AT(1) block (valsartan, 0.1 mg/kg), and a combined treatment (benezaprilat, 0.0625 mg/kg; valsartan, 0.1 mg/kg).

RESULTS

In the left ventricular myocyte study, BK levels increased over 93% with all treatments compared to untreated values (P < 0.05). In the in vivo study, basal interstitial BK values were lower in the CHF group than in controls (2.64 +/- 0.57 vs 5.91 +/- 1.4 nM, respectively, P < 0.05). Following acute infusion of the ACEI, BK levels in the CHF state increased from baseline (57% +/- 22; P < 0.05). Following combined ACEI/AT(1) block, BK levels increased from baseline in both control (42% +/- 11) and CHF groups (60% +/- 22; P < 0.05 for both).

CONCLUSION

These findings suggest that ACEI, or combined ACEI/AT(1) block increased BK at the level of the myocyte and potentiated BK levels in the CHF myocardial interstitium.

Effects of adenosine receptor subtype A1 on ventricular and renal function

The adenosine subtype 1 (A1) receptor, which may influence cardiac function and modulate renal function, may have particular relevance in congestive heart failure (CHF). However, the effects of A1 receptor inhibition in the setting of CHF are poorly defined. Systemic hemodynamics and indices of renal function were measured in pigs with pacing-induced CHF at 240 bpm for 3 weeks (n = 10) before and after A1 receptor blockade with 100 microg of BG9719 (1,3-dipropyl-8-[2-(5,6-epoxynorbornyl)]xanthene) or in CHF pigs after infusion of vehicle only (n = 10). Heart rate, mean aortic pressure, and left ventricular peak pressure increased following A1 blockade in the CHF group, consistent with an adenosine inhibitory effect. However, cardiac output and global measures of vascular resistance did not significantly change following A1 blockade. Urine output increased twofold and sodium clearance increased threefold following A1 blockade (p < 0.05). Creatinine clearance increased following A1 blockade (127 +/- 17 vs. 62 +/- 7 ml/min, p < 0.05). Selective A1 receptor blockade improved glomerular filtration rate and induced a natriuresis and diuresis in a model of CHF without adverse effects on cardiac function. These unique results suggest that renal A1 receptor activation may contribute to the reduced renal function associated with CHF.

Effects of angiotensin converting enzyme inhibitor and angiotensin II type 1 receptor blocker on cardiac dysfunction induced by isoproterenol in dogs

We examined whether angiotensin converting enzyme (ACE) inhibitors and angiotensin II type 1 receptor blockers (ARB) prevent isoproterenol (ISO)-induced left ventricular (LV) dysfunction in dogs. The effects of a large dose of ISO, 1 microg/kg/min, 3 h infusion, were investigated in three groups with simultaneous infusion of an ACE inhibitor (quinaprilat), ARB (candesartan) or saline. ISO infusion significantly decreased LV dP/dt, LV ejection fraction and LV fractional shortening, and significantly increased tau, the time constant of isovolume relaxation of LV, and LV end diastolic pressure. All of these changes were significantly attenuated in both the ACE inhibitor and ARB groups, especially in the ARB group. Serum levels of creatinin kinase isoform MB, lactate dehydrogenase and lipid peroxide were significantly increased by ISO. However, the increases in these markers of myocardial damage were significantly diminished by simultaneous infusion of an ACE inhibitor or ARB, especially by ARB. In conclusion, an ACE inhibitor and ARB prevent LV systolic and diastolic dysfunction as well as myocardial damage induced by excess beta-adrenergic stimulation.