Development of heart failure in chronic hypertensive Dahl rats: focus on heart failure with preserved ejection fraction

The impact of hypertension on left ventricular (LV) structure, pump function, and heart failure in Dahl salt-sensitive rats is poorly characterized but hypothesized to yield insights into the pathophysiology of heart failure with normal or preserved ejection fraction. Eighty Dahl salt-sensitive rats were fed either a high-salt (HS) or low-salt (LS, controls) diet starting at age 7 weeks. Ventricular properties were measured by echocardiography, hemodynamics and end-systolic and end-diastolic pressure-volume relationships (ESPVR and EDPVR, respectively). Compared with LS controls, HS rats developed severe hypertension and LV hypertrophy. At week 12, HS rats developed passive diastolic dysfunction (leftward/upward shifted EDPVR, increased chamber stiffness) with reductions in end-diastolic volume. However, the ESPVR also shifted upward (enhanced end-systolic function) so that overall pump function was enhanced compared with LS, and there was no change in end-diastolic pressure (EDP). At 16 and 20 weeks, HS hearts enlarged so that end-diastolic volumes and EDPVRs became similar to the respective age-matched LS controls. Concomitantly, the ESPVRs and overall pump function curves also moved toward controls, and ejection fraction declined. Despite normal or enhanced overall pump function at these times, EDP and wet lung weight increased, indicative of development of heart failure. In the Dahl salt-sensitive rat, which pathophysiologically retains salt and water, the development of heart failure (increased EDP and wet lung weight) is dissociated from changes in passive diastolic and active systolic properties. These observations suggest that a volume overload sate plays an important pathophysiological role in development of heart failure despite preserved overall ventricular pump function in this model of chronic hypertension.     

Therapeutic effects of angiotensin II type 1 receptor blocker at an advanced stage of hypertensive diastolic heart failure

OBJECTIVE: Angiotensin II type 1 receptor blocker (ARB) is increasingly prescribed for the treatment of systolic heart failure with a growing body of clinical evidence. The roles of ARB, however, remain to be clarified in the treatment of diastolic heart failure (DHF), particularly at its advanced stage. This experimental study investigated the effects of ARB administered at an advanced stage of hypertensive DHF. METHODS: Dahl salt-sensitive rats fed an 8% NaCl diet from age 7 weeks represent overt DHF at age 20 weeks, as noted in previous studies (hypertensive DHF model). The DHF model rats were randomly divided into two groups at age 17 weeks when left ventricular diastolic dysfunction, hypertrophy, fibrosis, macrophage infiltration and reactive oxygen species generation were already augmented; six rats treated for 3 weeks with a subdepressor dose of ARB (olmesartan 0.6 mg/kg per day), and six untreated rats. RESULTS: The 3-week administration of ARB significantly decreased the left ventricular end-diastolic pressure in association with attenuation of left ventricular hypertrophy, fibrosis and diastolic dysfunction. Macrophage infiltration was attenuated with decreased gene expression of transforming growth factor-beta1 and monocyte chemoattractant protein-1 in the left ventricular myocardium of the ARB-treated rats. The production of reactive oxygen species also decreased with NADPH oxidase activity. CONCLUSIONS: ARB provides beneficial effects in hypertensive DHF independent of its antihypertensive effects even if initiated at an advanced stage. The beneficial effects are at least partly attributed to the attenuation of inflammatory changes and oxidative stress through the suppression of cytokine and chemokine production and of NADPH oxidase activity.     

Prevention of diastolic heart failure by endothelin type A receptor antagonist through inhibition of ventricular structural remodeling in hypertensive heart

OBJECTIVES: Despite the clinical frequency of diastolic heart failure, its therapeutic strategy has not been established. Our recent study demonstrated activation of the endothelin (ET) system in a diastolic heart failure model with hypertension. Several studies have reported that ET type A (ETA) receptor antagonist improves systolic function and prevents systolic heart failure; however, its effects on diastolic heart failure are unknown. We investigated the effects of chronic administration of ET(A) receptor antagonist in diastolic heart failure. DESIGN AND METHODS: Dahl-Iwai salt-sensitive rats fed on a high-salt diet from 7 weeks of age, in which congestive heart failure develops following hypertension without cardiac chamber dilatation or systolic dysfunction, were divided into groups with and without administration of a subdepressor dose of ET(A) receptor antagonist. RESULTS: Hypertension induced compensatory left ventricular (LV) hypertrophy at 13 weeks in six untreated rats. Persistent pressure overload developed progressive LV hypertrophy and fibrosis from 13 to 19 weeks, resulting in elevated LV filling pressure and increased lung weight. Chronic ET(A) receptor blockade did not restrain compensatory LV hypertrophy at 13 weeks; however, it attenuated LV hypertrophy and fibrosis thereafter (n = 6). These beneficial effects resulted in the maintenance of normal LV filling pressure without changes in LV end-diastolic diameter, indicating prevention of LV stiffening. CONCLUSIONS: Chronic ET(A) receptor blockade is likely to exert beneficial effects in diastolic failure through attenuation of the progression of LV hypertrophy and fibrosis.     

Evolving changes in Doppler mitral flow velocity pattern in rats with hypertensive hypertrophy

OBJECTIVES

The aim of our study was to explore evolving changes in a mitral flow velocity pattern (MFVP) and its hemodynamic and pathological correlates in hypertensive rats in an isolated diastolic heart failure model.

BACKGROUND

Development of left ventricular (LV) hypertrophy and concomitant diastolic dysfunction cause heart failure in hypertensive hearts even with normal systolic function; however, associated evolving change in MFVP is still unclear.

METHODS

Mitral flow velocity pattern was recorded every 2 weeks from 7 to 19 weeks in six hypertensive rats. Hemodynamic and pathological correlates of Doppler mitral flow indexes were examined as an additional part of the study using the hypertensive rats at the age of 13 weeks (compensatory stage, N = 7) and at 19 weeks (heart failure stage, N = 8).

RESULTS

Initial development of pressure overload LV hypertrophy resulted in a decrease in early diastolic filling wave (E), a reciprocal increase in the filling wave due to atrial contraction (A) and prolongation of deceleration time of E wave (relaxation abnormality pattern). These changes were associated with an increase in tau, an index of LV relaxation, but without a change in LV end-diastolic pressure. Transition to congestive heart failure caused an increase in E, a decrease in A and shortening of deceleration time. These changes were not associated with further increase in tau but with elevation of LV end-diastolic pressure, reflecting marked LV hypertrophy and myocardial fibrosis.

CONCLUSIONS

Development of pressure overload LV hypertrophy is associated with evolving changes in MFVP from normal to relaxation abnormality pattern and, in turn, to pseudonormalized to restrictive pattern. Analysis of MFVP may be useful to follow not only functional but also constitutional changes of the myocardium in hypertensive hearts.     

Roles of renin-angiotensin and endothelin systems in development of diastolic heart failure in hypertensive hearts

OBJECTIVE: Although interest in diastolic heart failure is growing because of its clinical frequency, little is known about this type of heart failure. Our laboratory recently developed a diastolic heart failure model using Dahl salt-sensitive rat. In this model, gene expression of angiotensin-converting enzyme and endothelin (ET) system in the left ventricle was enhanced at heart failure stage without downregulation of angiotensin type 1a receptor mRNA level. However, the roles of these humoral systems in the transition to diastolic failure remain unclear. METHODS: Subdepressor doses of angiotensin II type 1 (AT1) receptor and ET type A (ETA) receptor antagonists were administered in this model just after onset of hypertension, and their effects were investigated. RESULTS: Neither AT1 nor ETA receptor blockade inhibited the early (13 weeks) compensatory left ventricular (LV) hypertrophy. This form of compensatory hypertrophy is associated with subnormal LV end-systolic stress, which was normalized by AT1 receptor blockade but not by ETA receptor blockade. Progression of LV hypertrophy and fibrosis and transition to heart failure (19 weeks) in the untreated rats were prevented by both antagonists, resulting in normalization of LV end-diastolic pressure and lung weight. AT1 receptor blockade, but not ETA receptor blockade, normalized time constant of LV relaxation. Enhanced gene expression for ET system in the left ventricle observed in the untreated rats was suppressed with AT1 receptor antagonist administration. ETA receptor blockade slightly but significantly elevated the AT1a receptor mRNA level as compared with the untreated rats. CONCLUSIONS: RAS and ET system contribute to the transition to diastolic heart failure through the development of excessive hypertrophy and ventricular fibrosis in hypertensive heart diseases, however, neither RAS nor ET system is mandatory for normal compensation for pressure overload. RAS apparently causes such diastolic effects at least partly through the ET system.     

Alterations in Early Filling Dynamics Predict the Progression of Compensated Pressure Overload Hypertrophy to Heart Failure Better than Abnormalities in Midwall Systolic Shortening

To evaluate whether the evolution of compensated pressure overload hypertrophy (POH) to overt heart failure (HF) is better predicted by systolic versus diastolic dysfunction, serial echocardiography was performed 1, 2, 4, 8, and 10 weeks after suprarenal aortic banding in 52 rats. One week after banding, at comparable extent of left ventricular hypertrophy and geometry, myocardial and chamber systolic performance, a restrictive filling pattern was well evident only in rats which eventually developed overt HF, according to postmortem lung weight. In experimental POH, early assessment of transmitral flow velocity allows to predict a faster progression toward HF.     

Long-term administration of amlodipine prevents decompensation to diastolic heart failure in hypertensive rats.

OBJECTIVES; We assessed the effects of long-term amlodipine administration in a diastolic heart failure (DHF) rat model with preserved systolic function as well as the relationship between changes in left ventricular (LV) myocardial stiffening and alterations in extracellular matrix. BACKGROUND: Although the effect of long-term administration of amlodipine has been shown to be disappointing in patients with systolic failure, the effect is unknown in those with DHF. METHODS: Dahl salt-sensitive rats fed a high-salt diet for seven weeks were divided into three groups: eight untreated rats (DHF group), eight rats given high-dose amlodipine (10 mg/kg/day; HDA group) and seven rats given low-dose amlodipine (1 mg/kg/day; LDA group). RESULTS: High-dose administration of amlodipine decreased systolic blood pressure and controlled excessive hypertrophy, without a decrease in the collagen content, and prevented the elevation of LV end-diastolic pressure at 19 weeks. Low-dose administration of amlodipine with subdeppressive effects did not control either hypertrophy or fibrosis; however, it prevented myocardial stiffening and, hence, the elevation of LV end-diastolic pressure. The ratio of type I to type III collagen messenger ribonucleic acid levels was significantly lower in both the HDA and LDA groups than in the DHF group. CONCLUSIONS: Long-term administration of amlodipine prevented the transition to DHF both at the depressor and subdepressor doses. Amlodipine did not decrease the collagen content, but attenuated myocardial stiffness, with inhibition of the phenotype shift from type III to type I collagen. Thus, amlodipine may exert beneficial effects through amelioration of collagen remodeling in the treatment of DHF.     

Renin angiotensin system-dependent hypertrophy as a contributor to heart failure in hypertensive rats: different characteristics from renin angiotensin system-independent hypertrophy

OBJECTIVES: This study aimed to characterize the difference between renin angiotensin system (RAS)-dependent and RAS-independent hypertrophy and their differential contribution to the transition to heart failure. BACKGROUND: Hypertensive left ventricular (LV) hypertrophy develops with RAS activation in the heart; however, LV hypertrophy develops even without RAS activation. METHODS: Left ventricular geometry and function were assessed in Dahl salt-sensitive rats placed on an 8% NaCl diet from seven weeks old (hypertensive rats) and in those placed on an 0.3% NaCl diet (control rats, n = 8). The hypertensive rats were randomized to no treatment (n = 8) or treatment with the angiotensin type 1 receptor (AT1R) antagonist candesartan (1 mg/kg per day, n = 10) after the baseline echocardiography study. RESULTS: From 7 to 13 weeks, AT1R blockade at a subdepressor dose did not restrain the development of LV hypertrophy but prevented narrowing of LV diastolic dimension, leading to the normalization of abnormally decreased end-systolic wall stress in the untreated rats. Progressive development of LV hypertrophy in spite of lower than normal end-systolic wall stress (excessive hypertrophy) after 13 weeks was suppressed by the AT1R blockade. Elevation of LV end-diastolic pressure and prolongation of Tau were associated with histological evidence of myocyte hypertrophy and massive interstitial fibrosis in the untreated rats, and none of these was evident in the treated rats. CONCLUSIONS: Renin-angiotensin system activation and AT1R signaling may be dispensable for the development of early adaptive LV hypertrophy and closely linked to the transition to heart failure.     

Pravastatin increases survival and suppresses an increase in myocardial matrix metalloproteinase activity in a rat model of heart failure

OBJECTIVES: Oxidative stress is implicated in the pathogenesis of heart failure and affects the activity of matrix metalloproteinases (MMPs). We have now investigated the role of MMPs and their tissue inhibitors (TIMPs) in the transition from compensated left ventricular (LV) hypertrophy to heart failure as well as the effects of pravastatin on this transition in a rat model. METHODS: Dahl salt-sensitive rats were fed a high-salt (8% NaCl) diet and treated with pravastatin (50 or 100 mg/kg per day) or vehicle from 7 weeks of age. RESULTS: Pravastatin did not attenuate LV hypertrophy apparent at 12 or 18 weeks of age. However, the high dose of this drug markedly improved indices of diastolic function (early diastolic myocardial velocity) and systolic function (LV fractional shortening) at 18 weeks of age and increased the survival rate. It also prevented a decrease in the ratio of reduced to oxidized glutathione and an increase in NADPH oxidase activity in the left ventricle induced by the high-salt diet. The activities of MMP2 and MMP9 and the abundance of TIMP1 and TIMP2 in LV tissue were increased at 18 weeks of age, and pravastatin also prevented these changes. CONCLUSION: Although pravastatin did not attenuate LV hypertrophy, it prevented the transition from compensated hypertrophy to heart failure in this rat model. This effect of pravastatin may result from a reduction both in the level of oxidative stress and in MMP activity in the heart.     

Local neurohumoral regulation in the transition to isolated diastolic heart failure in hypertensive heart disease: absence of AT1 receptor downregulation and 'overdrive' of the endothelin system

OBJECTIVE: Although isolated diastolic heart failure with preserved left ventricular (LV) systolic function frequently occurs, regulation of local neurohumoral factors in the transition from diastolic dysfunction without signs of heart failure to diastolic failure, a target for therapeutic strategy, remains to be clarified, partly because of a lack of animal models. Our laboratory recently demonstrated that Dahl-Iwai salt-sensitive (Dahl-S) rats fed on a high-salt diet since 7 weeks of age develop hypertension followed by compensated LV hypertrophy at 13 weeks and transition to isolated diastolic heart failure at 19 weeks. METHODS: Gene expression of the components of the renin-angiotensin system, endothelin (ET) system and natriuretic peptide system in the left ventricle was investigated in the transition to isolated diastolic heart failure in this model. RESULTS: The compensated ventricular hypertrophy was associated with slight increases in angiotensin-converting enzyme (ACE) and angiotensin II type-1a (AT1a) receptor mRNA levels. Although preproET-1 (ppET-1) and ET-converting enzyme-1 (ECE-1) mRNA levels were not increased, mRNA levels of ET type-A (ETA) and ET type-B (ETB) receptors were increased. Atrial natriuretic peptide (ANP) mRNA level increased, but not brain natriuretic peptide (BNP) mRNA level. At the decompensated failing stage (at 19 weeks), ACE mRNA level further increased without downregulation of ATla receptor mRNA level. The mRNA levels of ppET-1 and ECE-1 increased with persistent upregulation of mRNA levels of ETA and ETB receptors, and immunohistochemical staining for ET-1 was found at endothelial cells and myocytes. BNP mRNA level increased with a further increase in ANP mRNA level. CONCLUSIONS: The transition to isolated diastolic heart failure in hypertrophied hearts was associated with preserved gene expression of the renin-angiotensin system and 'overdrive' of gene expression of the ET system. BNP gene expression is likely to be activated by the progression of diastolic failure rather than by LV hypertrophy alone.     

The Influence of Myocardial Systolic Shortening on Action Potential Duration Following Changes in Left Ventricular End-Diastolic Pressure

APD and Systolic Shortening. Introduction: Contraction-excitation feedback may he an important factor in arrhythmogenesis in patients with heart failure. We have previously demonstrated the contrasting effects of raising left ventricular end-diastolic pressure on action potential duration in dog and guinea pig hearts. The current study was undertaken to assess whether these differing effects might reflect differences in the effect of varying left ventricular end-diastolic pressure on systolic shortening in the two models. Methods and Results: Two models were studied and compared. In open chest dog hearts and isolated guinea pig hearts, measurements of myocardial segment length were made while left ventricular end-diastolic pressure was raised and lowered at constant left ventricular peak systolic pressure. Action potentials were also recorded while left ventricular end-diastolic pressure was changed. The dog hearts were studied further in a manner aimed at reproducing the contraction pattern of the guinea pig hearts. In the in situ dog heart, elevation of left ventricular end-diastolic pressure, and the consequent increase in end-diastolic segment length, was accompanied by a marked increase in systolic shortening, such that minimum systolic segment length remained unchanged. Elevation of left ventricular end-diastolic pressure was accompanied by a prolongation of action potential duration. In the in vitro guinea pig model, elevation of left ventricular end-diastolic pressure was accompanied by more modest changes in systolic shortening, which were not sufficient to compensate for increased diastolic segment length. Consequently, minimum systolic segment length increased as the hearts dilated. Elevation of left ventricular end-diastolic pressure was accompanied by a shortening of action potential duration. In a further series of experiments, the effects of increased left ventricular end-diastolic pressure were studied in the dog model while allowing aortic pressure to rise, thereby restricting systolic shortening. Under these circumstances, the dog model was similar to the guinea pig model, with an increase in left ventricular end-diastolic pressure causing a shortening of action potential duration. Conclusion: Our results suggest that the effects of preload changes on action potential duration depend on accompanying changes in systolic shortening. This suggests a possible role for contraction-excitation feedback in arrhythmogenesis in patients with regional wall-motion abnormalities.     

Isoproterenol-induced alterations in myocardial blood flow, systolic and diastolic function in conscious dogs with heart failure

The effects of isoproterenol were examined in 10 conscious, chronically instrumented adult dogs with left ventricular (LV) failure after pressure overload hypertrophy induced by aortic banding at 8-10 weeks of age (LV free wall plus septum-to-body weight ratio, 8.6 +/- 0.5 g/kg) and also in eight control dogs (LV free wall plus septum-to-body weight ratio, 5.1 +/- 0.3 g/kg). Baseline values of heart rate, LV end-diastolic pressure, LV end-diastolic stress, and LV systolic wall stress were greater in the LV failure dogs (p less than 0.01), whereas the ejection phase index, rate of change of LV short-axis diameter, LV dD/dt, was depressed compared with control animals. In the control animals, isoproterenol infusion increased Vcf and LV dD/dt significantly (p less than 0.05), whereas LV systolic wall stress did not change. In the LV failure dogs, the increases in Vcf and LV dD/dt were less (p less than 0.01), and LV systolic wall stress increased (p less than 0.01). In the control animals, LV end-diastolic pressure, LV end-diastolic stress, LV end-diastolic stress-dimension ratio, diastolic radial myocardial stiffness, and the time constant of isovolumic relaxation decreased (p less than 0.05), whereas in the LV failure dogs, LV end-diastolic pressure, LV end-diastolic stress, diastolic radial myocardial stiffness, and the LV end-diastolic stress-dimension ratio increased. In the LV failure group, the endocardial to epicardial blood flow ratio fell to 0.59 +/- 0.06 during isoproterenol infusion, that is, significantly lower than in control dogs (0.93 +/- 0.06). These data support the concept that potent sympathomimetic amines exert deleterious effects on systolic and diastolic function in the failing heart, potentially related to subendocardial hypoperfusion.     

Moderate calorie restriction improves cardiac remodeling and diastolic dysfunction in the Dahl-SS rat

Caloric restriction extends longevity and reduces the onset of chronic disease in many animal models. Recently, caloric restriction was shown in humans to be associated with lower blood pressure, decreased systemic inflammation, and improved cardiac diastolic parameters. However, the causation and mechanisms of caloric restriction were obscured by the varied diet composition of the participants. The Dahl salt-sensitive rat which develops gradual, hypertension-associated diastolic dysfunction was used in this study to assess the impact of caloric restriction upon decompensated pressure-overload hypertrophy. Male Dahl salt-sensitive rats were provided either a low-salt diet or a high-salt diet to initiate heart failure progression. A further subset of high-salt rats underwent 15% calorie restriction, with salt load held constant. Parameters measured included serial systolic blood pressure, body weight, and changes of left ventricular systolic and diastolic parameters and ventricular geometry by echocardiography. After 18 weeks, fasting glucose, blood lipids, heart weight, kidney weight, lung weight, plasma interleukin-6 and TNF-alpha, and cardiac lipid peroxidation were measured. Low-salt rats did not develop heart failure. While high-salt rats displayed features of decompensated pressure-overload hypertrophy, moderate calorie restriction remarkably reduced morbidity. Compared to the high-salt fed group, the high-salt, calorie-restricted group showed reduced blood pressure, delayed onset of cachexia, lower fasting hyperlipidemia, lower cardiac, renal and lung weight, less plasma IL-6 and TNF-alpha, less cardiac oxidative damage, and improved diastolic chamber function and cardiac index. Modest calorie restriction, independent of salt intake, reduced pathogenesis in this well described model of decompensated pressure-overload hypertrophy.     

Exercise intolerance in rats with hypertensive heart disease is associated with impaired diastolic relaxation

A decrease in functional capacity is one of the most important clinical manifestations of hypertensive heart disease, but its cause is poorly understood. Our purpose was to evaluate potential causes of hypertension-induced exercise intolerance, focusing on identifying the type(s) of cardiac dysfunction associated with the first signs of exercise intolerance during the course of hypertensive heart disease. Exercise capacity was measured weekly in Dahl salt-sensitive rats as they developed hypertension as well as in Dahl salt-resistant control rats. Exercise capacity was unchanged from baseline during the first 8 weeks of hypertension, suggesting that hypertension itself did not cause exercise intolerance. After 9 to 12 weeks of hypertension, exercise capacity decreased in salt-sensitive rats but not in control rats. After 10 weeks of hypertension, indices of diastolic function (early truncation of the E wave), as assessed by echocardiography at rest, were decreased in the salt-sensitive rats. When exercise capacity had decreased by approximately 25% in a rat, the heart was isolated, and left ventricular (LV) compliance and systolic function were measured. At that time point, LV hypertrophy was modest (an approximately 20% increase in LV mass), and systolic function was normal or supernormal, indicating that exercise intolerance began during "compensated" LV hypertrophy. Passive LV compliance remained normal in salt-sensitive rats. Thus, in this model of hypertensive heart disease, exercise intolerance develops during the compensated stage of LV hypertrophy and appears to be due to changes in diastolic rather than systolic function. However, studies in which LV function is assessed during exercise are needed to conclusively define the roles of systolic and diastolic dysfunction in causing exercise intolerance.     

Therapy for diastolic heart failure

There is little objective to guide the therapy of patients with diastolic heart failure. Because of the similarities of pathophysiology abnormalities in diastolic and systolic heart failure, it is a reasonable inference to suggest that the proven therapy for systolic heart failure may also be of benefit in patients with diastolic heart failure. Treatment of underlying or exacerbating conditions in diastolic heart failure, such as hypertension, left ventricular hypertrophy, ischemia, diabetes, anemia, obesity and pulmonary disease is an important means of managing diastolic heart failure. Control of systolic blood pressure is effective in improving and preventing the development of diastolic heart failure. Treatment of diastolic heart failure is most effective when it is associated with hypertension. Production of systolic arterial pressure acutely reduces pulmonary congestion, ischemia, and chronically may lead to regression of left ventricular hypertrophy. Patients with diastolic heart failure in the absence of hypertension are very difficult to treat.     

Arterial hypertension and chronic heart failure

Arterial hypertension, alone or in combination with ischemic heart disease, precedes the development of heart failure. The Framingham study demonstrated that hypertension was the major risk factor in the development of heart failure. Arterial hypertension is not a sole factor contributing to the development of heart failure. The syndrome of heart failure is a consequence of multiple systemic responses and the development of heart failure is a complex and progressive process associated with cardiovascular disease resulting from risk factors: hypertension, obesity, smoking and dyslipidaemia. Arterial hypertension is the main precursor of left ventricular hypertrophy. Initially, this process causes diastolic dysfunction in the early stages of primary hypertension. Systolic dysfunction is rarely observed in those subjects. Left ventricular hypertrophy is also an important risk factor for myocardial infarction and ventricular arrhythmias. Asymptomatic systolic and diastolic left ventricular dysfunction may both progress to overt HFThe primary prevention of heart failure patients should be based upon strategies providing tight and sustained blood pressure control. This therapy should include an agent that inhibits the renin–angiotensin–aldosterone system. Treatment of arterial hypertension in patients with HF must take into account the prevalent type of cardiac dysfunction—diastolic or systolic.     

High-dose 17β–estradiol treatment prevents development of heart failure post–myocardial infarction in the rat

OBJECTIVES: Prognosis of heart failure remains poor despite therapeutic advances, such as angiotensin converting enzyme inhibition or beta-receptor blockade. Thus, more effective forms of treatment are urgently needed. Since estrogens have been shown to modulate migration and proliferation of cardiac fibroblasts and to modulate the expression of estrogen receptors of cardiomyocytes we examined whether high-dose estrogen treatment can affect post-myocardial infarction left ventricular remodeling. METHODS: Female rats were treated with 17beta-estradiol (7.5 mg/90 d) or placebo for ten weeks, starting two weeks prior to experimental myocardial infarction. Eight weeks after infarction, in vivo echocardiographic and hemodynamic measurements as well as isolated heart perfusion were performed. RESULTS: In vivo, chronic estrogen treatment almost completely prevented the development of all signs of heart failure that occur in untreated infarcted hearts, such as increased left ventricular diameters (dilatation), reduced fractional shortening (systolic dysfunction) or increased left ventricular end-diastolic pressure (diastolic dysfunction). In vitro, the right- (indicating structural dilatation) and downward (indicating left ventricular dysfunction) shift of left ventricular pressure-volume curves occurring in untreated infarcted hearts was completely prevented by estrogen. CONCLUSIONS: High dose estradiol treatment prevented development of post-MI remodeling, as assessed by in vivo and in vitro parameters of LV dysfunction. Estrogen may hold the potential of becoming a new form of heart failure treatment.However, the mechanisms responsible for this striking and unexpected beneficial action of estrogen in heart failure remain to be elucidated.     

Effects of imidapril on endothelin-1 and ACE gene expression in failing hearts of salt-sensitive hypertensive rats

The renin-angiotensin system and endothelin are important regulators of the cardiovascular system. Although increased production of endothelin-1 (ET-1) is reported in patients with heart failure, the detailed mechanism remains to be determined. To elucidate the relationship between the renin-angiotensin system and ET-1 in hypertensive heart failure, we evaluated the effects of long-term treatment with imidapril, an angiotensin converting enzyme (ACE) inhibitor, on preproET-1, endothelin A receptor (ETAR), and ACE mRNA expression in the left ventricle and evaluated these in relation to myocardial remodeling in the failing heart of Dahl salt-sensitive (DS) hypertensive rats fed a high salt diet. In DS rats fed an 8% NaCl diet after the age of 6 weeks, a stage of concentric left ventricular hypertrophy at 11 weeks (DSLVH) was followed by a distinct stage of left ventricular failure with chamber dilatation at 18 weeks (DSHF). Imidapril (DSHF-IM, n = 8, 1 mg/kg/day, subdepressor dose) or vehicle (DSHF-V, n = 8) was given from stage DSLVH to DSHF for 7 weeks, and age-matched (18 weeks) Dahl salt-resistant rats fed the same diet served as the control group (DR-C, n = 8). In both groups, blood pressure was similar and significantly higher than in DR-C. Markedly increased left ventricular end-diastolic diameter and reduced fractional shortening in DSHF-V was significantly ameliorated in DSHF-IM using transthoracic echocardiography. The preproET-1, ETAR, and ACE mRNA levels in the left ventricle were significantly increased in DSHF-V compared with DR-C, and significantly suppressed in DSHF-IM compared with DSHF-V. DSHF-V demonstrated a significant increase in the wall-to-lumen ratio and perivascular fibrosis in coronary arterioles, and myocardial fibrosis, with all these parameters being significantly improved by imidapril. In conclusion, myocardial remodeling and heart failure in DS rats fed a high salt diet were significantly ameliorated by a subdepressor dose of imidapril, which may be attributable to a decrease in ET-1 mRNA expression and angiotensin II in the left ventricle.     

Heart failure with normal ejection fraction

Opinion statement Heart failure with normal ejection fraction, also known as diastolic heart failure, is a major problem for patients and health-care providers and is a substantial expense to society. The main pathophysiologic processes involved are increased left ventricular stiffness and abnormal relaxation, with resulting impaired left ventricular filling. These processes typically displace the pressure-volume relationship in an upward direction, resulting in increased left ventricular end-diastolic, left atrial, and pulmonary capillary wedge pressures, leading to symptoms of pulmonary congestion. The most common clinical disorders leading to diastolic heart failure are 1) hypertension with concentric left ventricular hypertrophy, 2) coronary artery disease with decreased left ventricular compliance, 3) hypertrophic cardiomyopathy, and 4) aortic stenosis with concentric left ventricular hypertrophy. Echocardiography and cardiac catheterization with magnetic resonance imaging hold promise as future diagnostic tools. The approach to the treatment of diastolic heart failure is focused on four treatment goals: 1) persistent control of elevated blood pressure, with regression of left ventricular hypertrophy, 2) careful reduction of central blood volume (diuretics), 3) maintenance of atrial contraction and control of heart rate (beta-blockers, digoxin, atrioventricular pacing); and 4) improvement of left ventricular relaxation. There is currently no drug treatment specific for abnormal relaxation, although efforts are being made to develop such compounds. A promising future therapy includes agents that lyse advanced glycation end-products as an approach to relieving increased ventricular stiffness. In addition to pharmacotherapy, maintaining ideal body weight and a regular exercise program are also helpful in the treatment of diastolic heart failure. Although the overall prognosis of patients with diastolic dysfunction is more favorable than that of patients with systolic dysfunction, the frequency of treatment failure and recurrent symptoms underscores the need for further improvement in treatment of this condition.     

Experimental model for heart failure in rats--induction and diagnosis

BACKGROUND: Clinical heart failure is generally preceded by hypertrophy. Many animal models (e. g. toxic heart failure models) do not consider this hypertrophy. We set out to develop a heart failure model in rats by inducing pressure-overload hypertrophy. METHODS: We induced coarctation of the aortic arch with a tantalum clip (0.35 mm internal diameter) In 3-week-old rats (n=17). Starting at seven weeks postoperatively, we measured ejection fraction (EF), fractional shortening (FS), end-systolic (LVESD) and end-diastolic (LVEDD) left ventricular dimensions by echocardiography each week. Heart, lung, and liver specimens were analyzed histopathologically at least eleven weeks after the operation. RESULTS: Contractile function was significantly decreased in hearts from animals with aortic banding (EF: 45+/-5% vs. 73+/-5%, p<0.01; FS: 20+/-3% vs. 35+/-5%, p<0.01). At the same time, left ventricles were dilated (LVEDD: 9.1+/-0.6 mm vs. 7.4+/-0.5 mm; LVESD: 7.3+/-0.6 mm vs. 4.8+/-0.4 mm, p<0.01). These observations were associated with clinical and histopathological changes characteristic for chronic left heart failure. CONCLUSION: Placing a tantalum clip around the aortic arch in 3-week-old rats consistently induces left ventricular decrease in contractile function and dilatation after eleven weeks.