Pressure overload-induced cardiac hypertrophy with and without dilation

Olive oil protects against progression of heart failure by inhibiting remodeling of heart subsequent to myocardial infarction in rats

We examined the beneficial effects of olive oil against heart failure post-myocardial infarction (PMI), induced by coronary artery ligation in rats. Animals were divided into sham and ligated groups and fed either regular chow, olive oil (10% wt/wt), or corn oil (10% wt/wt) and were followed up to 16 weeks. On the echocardiography at 3 days (PMI), in the ligated regular chow (LRC), ligated olive oil (LOO), and ligated corn oil (LCO) left ventricular ejection fraction (LVEF) decrease was 12.14%, 16.42%, and 17.53% from the baseline, respectively. However, only LOO group improved LVEF significantly at 16 weeks PMI and became comparable with all sham groups. Both scar formation and collagen deposition at 16 weeks PMI were less pronounced in the LOO group. Myocardial TNF-α level at 4 weeks of PMI increased by 176%, 11%, and 181% in the LRC, LOO, and LCO groups, respectively. Plasma TNF-α levels in LOO were significantly lower than LRC group after 4 weeks of PMI. Myocardial redox ratio (reduced glutathione/oxidized glutathione) decreased at 4 weeks PMI by 44.4%, 16.4%, and 36.9% in the LRC, LOO, and LCO groups, respectively, compared to the baseline. These changes in the redox ratio at 16 weeks PMI were further exacerbated in the LRC and LCO groups. Lipid hydroperoxides formation increased at 4 weeks PMI by 137.4%, 14.6%, and 97.1% in the LRC, LOO, and LCO groups, respectively. Since coronary artery ligation decreased left ventricular ejection fraction, increased myocardial TNF-α and oxidative stress, and since olive oil was able to inhibit these effects, it is proposed that dietary olive oil modulates cardiac remodeling and heart failure subsequent to myocardial infarction.

Heart Plasticity in Response to Pressure- and Volume-Overload: A Review of Findings in Compensated and Decompensated Phenotypes

The adult human heart has an exceptional ability to alter its phenotype to adapt to changes in environmental demand. This response involves metabolic, mechanical, electrical, and structural alterations, and is known as cardiac plasticity. Understanding the drivers of cardiac plasticity is essential for development of therapeutic agents. This is particularly important in contemporary cardiology, which uses treatments with peripheral effects (e.g., on kidneys, adrenal glands). This review focuses on the effects of different hemodynamic loads on myocardial phenotype. We examine mechanical scenarios of pressure- and volume overload, from the initial insult, to compensated, and ultimately decompensated stage. We discuss how different hemodynamic conditions occur and are underlined by distinct phenotypic and molecular changes. We complete the review by exploring how current basic cardiac research should leverage available cardiac models to study mechanical load in its different presentations.

Lethal Arg9Cys phospholamban mutation hinders Ca2+-ATPase regulation and phosphorylation by protein kinase A

The regulatory interaction of phospholamban (PLN) with Ca(2+)-ATPase controls the uptake of calcium into the sarcoplasmic reticulum, modulating heart muscle contractility. A missense mutation in PLN cytoplasmic domain (R9C) triggers dilated cardiomyopathy in humans, leading to premature death. Using a combination of biochemical and biophysical techniques both in vitro and in live cells, we show that the R9C mutation increases the stability of the PLN pentameric assembly via disulfide bridge formation, preventing its binding to Ca(2+)-ATPase as well as phosphorylation by protein kinase A. These effects are enhanced under oxidizing conditions, suggesting that oxidative stress may exacerbate the cardiotoxic effects of the PLN(R9C) mutant. These results reveal a regulatory role of the PLN pentamer in calcium homeostasis, going beyond the previously hypothesized role of passive storage for active monomers.

How different two almost identical action potentials can be: a model study on cardiac repolarization

Spatial heterogeneity in the properties of ion channels generates spatial dispersion of ventricular repolarization, which is modulated by gap junctional coupling. However, it is possible to simulate conditions in which local differences in excitation properties are electrophysiologically silent and only play a role in pathological states. We use a numerical procedure on the Luo-Rudy phase 1 model of the ventricular action potential (AP1) in order to find a modified set of model parameters which generates an action potential profile (AP2) almost identical to AP1. We show that, although the two waveforms elicited from resting conditions as a single AP are very similar and belong to membranes sharing similar passive electrical properties, the modified membrane generating AP2 is a weaker current source than the one generating AP1, has different sensitivity to up/down-regulation of ion channels and to extracellular potassium, and a different electrical restitution profile. We study electrotonic interaction of AP1- and AP2- type membranes in cell pairs and in cable conduction, and find differences in source-sink properties which are masked in physiological conditions and become manifest during intercellular uncoupling or partial block of ion channels, leading to unidirectional block and spatial repolarization gradients. We provide contour plot representations that summarize differences and similarities. The present report characterizes an inverse problem in cardiac cells, and strengthen the recently emergent notion that a comprehensive characterization and validation of cell models and their components are necessary in order to correctly understand simulation results at higher levels of complexity.

Hemodynamic and histomorphometric characteristics of heart failure induced by aortic stenosis in the guinea pig: comparison of two constriction sizes

Heart failure induced by aortic stenosis in young guinea pigs could constitute an interesting model for pharmacology, but its natural history needs to be characterized. One hundred five guinea pigs (3-4 weeks old) underwent thoracic aortic banding with 12- (B12G) or 14-gauge (B14G) needles or similar sham operations (S12G, S14G). Animals alive at 7 d (S12G, n = 16; B12G, n = 28; S14G, n = 19; B14G, n = 27) were assessed at 60 or 120 d. At 60 d, compared with sham groups, left ventricular (LV) mass and wall thickness increased in operated groups, but LV systolic pressure and right ventricular (RV) wall thickness only increased in the B14G group. At 120 d, B12G animals still showed signs of compensated hypertrophy with LV and RV wall thickening (+8%, +21%) and LV dilation (+20%), whereas B14G animals showed signs of decompensation with LV end-diastolic pressure increase (+167%) and mean arterial pressure decrease (-28%) associated with LV and RV hypertrophy (+77%, + 51%) and greater increases of LV and RV wall thickening (+19%, + 57%), as well as LV dilation (+43%). A 12G stenosis results in compensated hypertrophy at 60 and 120 d; a 14G stenosis leads to compensated hypertrophy at 60 d and heart failure at 120 d.

B-type natriuretic peptide and wall stress in dilated human heart

Background Although B-type natriuretic peptide (BNP) is used as complimentary diagnostic tool in patients with unknown thoracic disorders, many other factors appear to trigger its release. In particular, it remains unresolved to what extent cellular stretch or wall stress of the whole heart contributes to enhanced serum BNP concentration. Wall stress cannot be determined directly, but has to be calculated from wall volume, cavity volume and intraventricular pressure of the heart. The hypothesis was, therefore, addressed that wall stress as determined by cardiac magnetic resonance imaging (CMR) is the major determinant of serum BNP in patients with a varying degree of left ventricular dilatation or dysfunction (LVD). Methods A thick-walled sphere model based on volumetric analysis of the LV using CMR was compared with an echocardiography-based approach to calculate LV wall stress in 39 patients with LVD and 21 controls. Serum BNP was used as in vivo marker of a putatively raised wall stress. Nomograms of isostress lines were established to assess the extent of load reduction that is necessary to restore normal wall stress and related biochemical events. Results Both enddiastolic and endsystolic LV wall stress were correlated with the enddiastolic LV volume (r = 0.54, P < 0.001; r = 0.81, P < 0.001). LV enddiastolic wall stress was related to pulmonary pressure (capillary: r = 0.69, P < 0.001; artery: r = 0.67, P < 0.001). Although LV growth was correlated with the enddiastolic and endsystolic volume (r = 0.73, P < 0.001; r = 0.70, P < 0.001), patients with LVD exhibited increased LV wall stress indicating an inadequately enhanced LV growth. Both enddiastolic (P < 0.05) and endsystolic (P < 0.01) wall stress were increased in patients with increased BNP. In turn, BNP concentration was elevated in individuals with increased enddiastolic wall stress (>8 kPa: 587 +/- 648 pg/ml, P < 0.05; >12 kPa: 715 +/- 661 pg/ml, P < 0.001; normal < or =4 kPa: 124 +/- 203 pg/ml). Analysis of variance revealed LV enddiastolic wall stress as the only independent hemodynamic parameter influencing BNP (P < 0.01). Using nomograms with "isostress" curves, the extent of load reduction required for restoring normal LV wall stress was assessed. Compared with the CMR-based volumetric analysis for wall stress calculation, the echocardiography based approach underestimated LV wall stress particularly of dilated hearts. Conclusions In patients with LVD, serum BNP was increased over the whole range of stress values which were the only hemodynamic predictors. Cellular stretch appears to be a major trigger for BNP release. Biochemical mechanisms need to be explored which appear to operate over this wide range of wall stress values. It is concluded that the diagnostic use of BNP should primarily be directed to assess ventricular wall stress rather than the extent of functional ventricular impairment in LVD.

Activation of apoptotic processes during transition from hypertrophy to heart failure in guinea pigs

Changes in oxidative stress and apoptotic process were studied during the progression of a compensated hypertrophy to a decompensated heart failure in guinea pigs. Banding of the ascending aorta resulted in heart hypertrophy. At 10 wk, ventricle-to-body weight ratio and thickness of the interventricular septum as well as the left ventricular wall were increased significantly. Although fractional shortening and ejection fraction were decreased, there were no signs of heart failure. Furthermore, there was no increase in wet-to-dry weight ratios for the lungs and liver at this stage. However, at 20 wk, heart failure was characterized by a significant depression in heart function as indicated by a decrease in fractional shortening, and ejection fraction and a lesser increase in wall thickness from diastole to systole. Animals also showed clinical signs of heart failure, and the wet-to-dry weight ratios of the lungs and liver were significantly higher. Cardiomyocyte oxidative stress was significantly higher in the 20-wk aortic-banded group. The ratio of Bax to Bcl-xl showed an increase at 10 wk, and there was a further increase at 20 wk. Mitochondrial membrane potential in the aortic-banded animals was significantly decreased at 10 and 20 wk. Cytochrome c levels were higher in the cytosol compared with the mitochondria, leading to a considerable increase in the expression of p17 subunit of caspase-3. At 20 wk, both early and late stages of apoptosis were observed in isolated cardiomyocytes. It is suggested that an increase in oxidative stress initiates mitochondrial death pathway during the hypertrophic stage, leading to apoptosis and heart failure at a later stage.

The role of coenzyme Q10 in heart failure

OBJECTIVE

To review the clinical data demonstrating the safety and efficacy of coenzyme Q10 (CoQ10) in heart failure (HF).

DATA SOURCES

Pertinent literature was identified through MEDLINE (1966-January 2005) using the search terms coenzyme Q10, heart failure, antioxidants, and oxidative stress. Only articles written in the English language and evaluating human subjects were used.

DATA SYNTHESIS

HF impairs the ability of the heart to maintain its normal cardiac output. Following an initial insult, cardiac remodeling ensues, resulting in left ventricular dilation and hypertrophy. Oxidative stress is also increased, while CoQ10 levels are decreased in patients with HF. This has led to the hypothesis that CoQ10, an antioxidant, may decrease oxidative stress, impair remodeling, and improve cardiac function.

CONCLUSIONS

Large, well-designed studies on this topic are lacking. The limited data from well-designed trials indicate there may be some minor benefits with CoQ10 therapy in ejection fraction and end diastolic volume. CoQ10 therapy has been shown to be relatively safe with a low incidence of adverse effects.

Compartmental analysis of steady-state diaphragm Ca2+ kinetics in chronic congestive heart failure

An analytic method based on simulation and modeling of long-term 45Ca(2+) efflux data was used to estimate steady-state Ca(2+) contents (nmolCa(2+)g(-1)tissuewetwt.) and exchange fluxes (nmolCa(2+)min(-1)g(-1)tissuewetwt.) for extracellular and intracellular compartments in in vitro resting diaphragm from congestive heart failure (CHF, n=12) and sham-operated (SHAM, n=10) rats. Left hemidiaphragms were excised from experimental animals, loaded with 45Ca(2+) for 1h, and washed out with 45Ca(2+)-free perfusate for 8h. Tissue from the right hemidiaphragm was used to assess single-fiber cross-sectional area (CSA) as well as the relative proteolytic activity of Ca(2+)-dependent calpain. Kinetic analysis of 45Ca(2+) efflux data revealed that CHF was associated with increased Ca(2+) contents of extracellular and intracellular compartments as well as increased Ca(2+) exchange fluxes for all compartments. This accounted for the model prediction of a 250% increase in total diaphragm Ca(2+). Furthermore, single-fiber CSA was decreased 12% and proteolytic activity of calpain was increased twofold in CHF diaphragm relative to SHAM.

CONCLUSIONS

The kinetic data are consistent with the hypothesis that diaphragm Ca(2+) overload in CHF required all intercompartmental Ca(2+) fluxes to increase. The potential relationships among Ca(2+) overload, increased activity of calpain, and wasting of the diaphragm in CHF are discussed.

Early anti-remodeling effect of labetalol in the congestive heart failure model induced by aortic constriction in the guinea pig

We investigated the effects of the beta1-beta2-alpha1-blocker, labetalol, in the congestive heart failure (CHF) model induced by aortic constriction in the guinea pig. One hundred days after aortic constriction, 52 animals were given either placebo, labetalol 2 mg/kg/d, or labetalol 20 mg/kg/d for 60 days. Eighteen sham-operated animals were used as controls. Investigations were performed at the end of the treatment period. Compared with sham-operated animals, banded animals receiving placebo showed signs of overt CHF with cardiac, systemic and regional (mesenteric and femoral) hemodynamic dysfunction, and pulmonary and hepatic congestion. An increase in whole heart, atria, and left and right ventricle weights associated with left ventricular cavity enlargement and left and right ventricular wall thickening indicated a remodeling process. Compared with placebo, labetalol did not significantly modify cardiac, systemic, or regional hemodynamic variables but significantly decreased pulmonary and hepatic congestion. Labetalol significantly reduced left ventricular cavity area (-10 and -20% after 2 and 20 mg/kg, respectively) and left ventricular (-4 and -16%) and right ventricular (-4 and -19%) wall thickness. In conclusion, labetalol induced partial regression of cardiac remodeling before hemodynamic improvement. This early anti-remodeling effect could play a role in the favorable effects observed with beta1-beta2-alpha1-blockers in humans.

Na(+)-K(+)-ATPase alpha(2)-isoform expression in guinea pig hearts during transition from compensation to decompensation

Disturbance in ionic gradient across sarcolemma may lead to arrhythmias. Because Na(+)-K(+)-ATPase regulates intracellular Na(+) and K(+) concentrations, and therefore intracellular Ca(2+) concentration homeostasis, our aim was to determine whether changes in the Na(+)-K(+)-ATPase alpha-isoforms in guinea pigs during transition from compensated (CLVH) to decompensated left ventricular hypertrophy (DLVH) were concomitant with arrhythmias. After 12- and 20-mo aortic stenosis, CLVH and DLVH were characterized by increased mean arterial pressure (30% and 52.7%, respectively). DLVH differed from CLVH by significantly increased end-diastolic pressure (34%), decreased sarco(endo)plasmic reticulum Ca(2+)-ATPase (-75%), and increased Na(+)/Ca(2+) exchanger (25%) mRNA levels and by the occurrence of ventricular arrhythmias. The alpha-isoform (mRNA and protein levels) was significantly lower in DLVH (2.2 +/- 0.2- and 1. 4 +/- 0.15-fold, respectively, vs. control) than in CLVH (3.5 +/- 0. 4- and 2.2 +/- 0.13-fold, respectively) and was present in sarcolemma and T tubules. Changes in the levels of alpha(1)- and alpha(3)-isoform in CLVH and DLVH appear physiologically irrelevant. We suggest that the increased level of alpha(2)-isoform in CLVH may participate in compensation, whereas its relative decrease in DLVH may enhance decompensation and arrhythmias.

Inhibition of tissue repair by spironolactone: role of mineralocorticoids in fibrous tissue formation

Mineralocorticoids have been implicated in promoting fibrous tissue formation in various organs. In the present study, we sought to address the potential contribution of mineralocorticoids to fibrous tissue formation using a skin pouch model which has proved valuable for the analysis of inflammatory and wound healing responses. Skin pouches were induced in rats by administration of a phorbol ester, croton oil (0.5 ml of a 1% solution). After 2 weeks, rats were killed and intact pouch tissue collected. Pouch weights of control and aldosterone-treated (0.75 microg/h via osmotic minipump) rats were similar (3.33 +/- 0.44 g vs. 3.70 +/- 0.28 g respectively). However, pouch weights were reduced by more than 50% in spironolactone-treated (25 mg/day powdered in food) animals (1.62 +/- 0.22 g and 1.27 +/- 0.23 g respectively in aldosterone and spironolactone alone groups). To ascertain the effects of different treatments on collagen accumulation, hydroxyproline concentration was measured. Compared with controls, hydroxyproline concentration was significantly reduced following spironolactone treatment (17.1 +/- 0.08 vs. 7.5 +/- 2.0 microg/mg dry wt, respectively, p < 0.01). This response to spironolactone was negated by coadministration of aldosterone (hydroxyproline concentration was 18.6 +/- 2.1 microg/mg dry wt). Following bilateral adrenalectomy, spironolactone reduced pouch weight and hydroxyproline concentration, which was not the case for adrenalectomy alone. Two week aldosterone administration in uninephrectomized rats on high salt diet was deemed ineffective in modulating pouch development (pouch wet wts were 3.48 +/- 0.4 g vs. 3.00 +/- 0.19 g in controls and aldosterone-treated rats, respectively). Mineralocorticoid receptor expression in pouch tissue was demonstrated by RT/PCR. Furthermore, NADP+-dependent 11beta-hydroxysteroid dehydrogenase 1 (11beta-HSD1) activity was detected in pouch tissue, together with lower levels of NAD+-dependent 11beta-HSD2. Spironolactone (p < 0.05) significantly reduced 11beta-HSD1 activity compared with controls. Thus, fibrous tissue possesses requisite components of MC action, and antagonism of mineralocorticoid receptors by spironolactone attenuates its formation. Pouch formation is under the influence of circulating MC and, we would like to propose, is also mediated through corticosteroids generated de novo at the site of tissue repair.

In vivo left ventricular function and collagen expression in aldosterone/salt-induced hypertension

Cardiac fibrosis is linked to aldosterone-induced hypertension, but the effects on in vivo left ventricular (LV) function are not established. We studied the relations between in vivo LV function and aldosterone/salt cardiac fibrosis. Adult guinea pigs (GPs) were treated for 3 months with an aldosterone infusion and high-salt diet. This treatment induced arterial hypertension (+35%) and moderate LV hypertrophy (LVH; +60%) without right ventricular (RV) hypertrophy. Echo-Doppler LV assessment demonstrated unaltered cardiac output, stroke volume, or LV relaxation. Type I collagen messenger RNA (mRNA) was significantly increased in both ventricles (LV, +48%; RV, +77%) and accompanied by a significant increase in total collagen deposition (LV, from 0.52% in controls to 4.4% in treated GPs; RV, from 0.82 to 5.5% in treated GPs). Plasma norepinephrine levels increased 2.6-fold (p < 0.01) and correlated with the increase in collagen deposition in both ventricles. Collagen content was not correlated with hypertension or LVH. We conclude that aldosterone administration induces cardiac collagen accumulation and a sympathetic stimulation, which might preserve systolic and diastolic function.

Modifications of myocardial Na+,K(+)-ATPase isoforms and Na+/Ca2+ exchanger in aldosterone/salt-induced hypertension in guinea pigs

OBJECTIVE

The aim of this study was to determine whether changes in cardiac Na+,K(+)-ATPase subunits and Na+/Ca2+ exchanger expression are regulated in aldosterone-salt hypertensive guinea pigs.

METHODS

Guinea pigs (GP) were unilaterally nephrectomized and randomized into three groups (aldosterone-salt; control-salt; control). After 90 days of treatment, echocardiographic M-mode assessment and right carotid arterial catheterization were performed in vivo, and plasma hormones and electrolytes were measured. mRNA and protein levels were studied by Northern and Western blot analysis.

RESULTS

Aldosterone-salt treatment induced, (1) arterial hypertension (+40%) and LV hypertrophy (+60%) without altering LV-fractional shortening, (2) an increase in plasma norepinephrine levels (+262%) and suppression of renin activity. Northern blot analysis showed the presence of the mRNA encoding the three alpha isoforms and the beta 1 subunit of Na+,K(+)-ATPase in GP myocardium. In the aldosterone-salt group, levels of alpha 1 and beta 1 mRNAs were unchanged. alpha 2 mRNA was increased in both ventricles, whereas alpha 3 mRNA was increased in hypertrophied LV only. Furthermore, levels of the Na+/Ca2+ exchanger mRNA were decreased in both ventricles. At protein level, the two major transcripts (alpha 1 and alpha 2) were detected but alpha 3 isoform was not. Parallel changes in protein and mRNA accumulation of alpha 1 and alpha 2 isoforms were observed in hypertrophied LV.

CONCLUSION

These results show that alpha 1 and alpha 2 isoforms are expressed in GP heart and that they are independently regulated in aldosterone-salt hypertension. Like the alpha 1 isoform in renal tissue, alpha 2 isoform is the main target of aldosterone-salt. Reciprocal expression of the Na+/Ca2+ exchanger and Na+,K(+)-ATPase suggests an adaptational mechanism which maintains an appropriate sodium gradient and calcium concentration in hypertensive myocardium.

Complete stunning in hypertrophied guinea pig heart. Defects in sarcolemmal calcium influx

Isolated sham control as well as hypertrophied guinea pig hearts were subjected to global ischemia and reperfusion. Developed force declined to zero during 5 min of ischemia without any significant change in resting tension in both sham control and hypertrophied hearts. Upon reperfusion, control hearts showed nearly complete recovery of developed force within 20 min, whereas hypertrophied hearts during this time showed no contractile function, i.e., "a complete stunning" was observed. A continued reperfusion of the stunned hypertrophied hearts ultimately resulted in complete recovery of force within 40-60 min. Data on myocardial cation content showed a relative calcium deficiency in the stunned hearts (3.4 mumol/gm dry wt) as compared to sham control hearts (5.3 mumol/gm dry wt). Stunning could be reversed sooner by isoproterenol (100 microns), and low Na+ (35 and 60 mM) perfusion. Recovery of contractile function by low Na+ was blocked by amiloride (0.17-1.2 mM) in a dose-dependent manner. Perfusion with Bay K8644 (0.1-10 microM) as well as low (0.62 mM) and high (2.5 mM) extracellular calcium concentrations failed to reverse stunning. The pharmacological interventions that were able to reverse the stunning condition also increased the myocardial calcium content. Although the possibilities of a sarcoplasmic reticular dysfunction and/or reduced sensitivity of myofilaments are not excluded, data suggest that a defect in calcium influx across the sarcolemma is an important factor in "complete stunning." It is suggested that this "potential sarcolemmal defect" in the hypertrophied heart, which is unmasked by the ischemic stress, may also represent an early abnormality in the pathogenesis of heart failure.

Role of oxidative stress in transition of hypertrophy to heart failure

OBJECTIVES

In an attempt to define the role of increased oxidative stress in the transition from compensatory hypertrophy to heart failure, this study examined the effects of long-term vitamin E therapy on the occurrence of heart failure subsequent to chronic pressure overload in guinea pigs.

BACKGROUND

Hyperfunctional heart hypertrophy has been shown to be accompanied by an increase in the endogenous antioxidant reserve, whereas congestive heart failure is accompanied by a decrease in this reserve. The effects of vitamin E, a naturally occurring antioxidant, on the development of heart failure from a hypertrophic stage were examined.

METHODS

The ascending aorta in guinea pigs was coarcted. For vitamin treatment, slow-release pellets were implanted at the time of the operation. The animals were assessed at 10 and 20 weeks for hemodynamic function, myocardial structure, antioxidant agents and oxidative stress.

RESULTS

Banding of the ascending aorta in guinea pigs resulted in hyperfunctional hypertrophy at 10 weeks, which was followed by congestive heart failure at 20 weeks. Hypertrophied hearts showed decreased oxidative stress, as evidenced by a higher oxidation-reduction (redox) state and less lipid peroxidation, whereas the failure stage was characterized by increased oxidative stress. Supplementation of animals with timed-release vitamin E tablets resulted in an increased myocardial content of the vitamin, and the banded animals did not develop any signs of heart failure at 20 weeks. Hemodynamic function at 20 weeks in these vitamin E-treated animals was also better maintained. The myocardial reduced glutathione/oxidized glutathione ratio of vitamin E-treated animals at 20 weeks was higher and lipid peroxidation was less compared with the untreated animals. Ultrastructural abnormalities were significantly less in the vitamin E-treated hearts compared with the untreated failing hearts at 20 weeks.

CONCLUSIONS

An improved myocardial redox state with vitamin E therapy, coupled with the modulation of the development of heart failure, may indicate a pathophysiologic role for increased oxidative stress in the pathogenesis of heart failure. This study suggests the potential therapeutic value of long-term antioxidant treatment in modulating or preventing the pathogenesis of heart failure.

Oxidative stress and heart failure

Various abnormalities have been implicated in the transition of hypertrophy to heart failure but the exact mechanism is still unknown. Thus heart failure subsequent to hypertrophy remains a major clinical problem. Recently, oxidative stress has been suggested to play a critical role in the pathogenesis of heart failure. Here we describe antioxidant changes as well as their significance during hypertrophy and heart failure stages. Heart hypertrophy in rats and guinea pigs, in response to pressure overload, is associated with an increase in 'antioxidant reserve' and a decrease in oxidative stress. Hypertrophied rat hearts show increased tolerance for different oxidative stress conditions such as those imposed by free radicals, hypoxia-reoxygenation and ischemia-reperfusion. On the other hand, heart failure under acute as well as chronic conditions is associated with reduced antioxidant reserve and increased oxidative stress. The latter may have a causal role as suggested by the protection seen with antioxidant treatment in acute as well as in chronic heart failure. It is becoming increasingly apparent that, anytime the available antioxidant reserve in the cell becomes inadequate, myocardial dysfunction is imminent.

Left ventricular remodeling and function in adult aortic stenosis

The aim of this study was to analyze the left ventricular (LV) geometric changes occurring in chronic pressure overload due to valvular aortic stenosis (AS). Fifty-six adult patients (30 women, 26 men, mean age seventy-two +/- nine years, range forty-five to eighty-five years) with isolated AS (mean valve area by Doppler = 0.6 +/- 0.2 cm2) underwent a complete Doppler echocardiographic examination. According to the value of relative wall thickness (RWT = 2 x posterior wall thickness/LV end-diastolic diameter) and LV mass index (LVMI) in normal subjects (RWT < or = 0.44, LVMI < or = 125 gr/m2) AS patients were subdivided into four groups: Normal: no patients; Concentric Remodeling RWT > 0.44, LVMI < or = 125 gr/m2): 4 patients (7%); Concentric Hypertrophy (RWT > 0.44, LVMI > 125 gr/m2): 39 patients (70%); and Eccentric Hypertrophy (RWT < or = 0.44, LVMI > 125 gr/m2): 13 patients [23%]. Eccentric hypertrophy patients had, as compared with those with concentric hypertrophy, a larger left ventricle (61 +/- 6.5 mm vs 47.6 +/- 6 mm, P < or = 0.001), a smaller mean wall thickness (11.3 +/- 1.2 vs 14.7 +/- 1.7 mm, P < 0.001) and reduced LV fractional shortening (FS% = 22.9 +/- 11 vs 42.6 +/- 8.7%, P < 0.001). Furthermore, most patients (11/13) of the former group had heart failure due to LV systolic dysfunction, while only 16 of 39 patients of the latter group had heart failure and all but 2 had normal LV systolic function.(ABSTRACT TRUNCATED AT 250 WORDS)

Left ventricular remodeling in valvular aortic stenosis. Echocardiographic and clinical changes in two patients during follow-up

Left ventricular (LV) response to chronic pressure overload of aortic stenosis (AS) is usually characterized by an increase of wall thickness without cavity enlargement ("concentric hypertrophy"). During follow-up, two patients with AS developed relevant structural and functional changes of the left ventricle, ie, progressive LV dilatation, wall thinning, and reduction of systolic performance. At the same time, the patients had clinical symptoms of congestive heart failure. The pathophysiologic relevance of this form of LV remodeling in AS is discussed.