Long-term captopril treatment improves diastolic filling more than systolic performance in rats with large myocardial infarction

Mechanisms for the development of heart failure and improvement of cardiac function by angiotensin-converting enzyme inhibitors

Angiotensin-converting enzyme (ACE) inhibitors, which prevent the conversion of angiotensin I to angiotensin II, are well-known for the treatments of cardiovascular diseases, such as heart failure, hypertension and acute coronary syndrome. Several of these inhibitors including captopril, enalapril, ramipril, zofenopril and imidapril attenuate vasoconstriction, cardiac hypertrophy and adverse cardiac remodeling, improve clinical outcomes in patients with cardiac dysfunction and decrease mortality. Extensive experimental and clinical research over the past 35 years has revealed that the beneficial effects of ACE inhibitors in heart failure are associated with full or partial prevention of adverse cardiac remodeling. Since cardiac function is mainly determined by coordinated activities of different subcellular organelles, including sarcolemma, sarcoplasmic reticulum, mitochondria and myofibrils, for regulating the intracellular concentration of Ca2+ and myocardial metabolism, there is ample evidence to suggest that adverse cardiac remodelling and cardiac dysfunction in the failing heart are the consequence of subcellular defects. In fact, the improvement of cardiac function by different ACE inhibitors has been demonstrated to be related to the attenuation of abnormalities in subcellular organelles for Ca2+-handling, metabolic alterations, signal transduction defects and gene expression changes in failing cardiomyocytes. Various ACE inhibitors have also been shown to delay the progression of heart failure by reducing the formation of angiotensin II, the development of oxidative stress, the level of inflammatory cytokines and the occurrence of subcellular defects. These observations support the view that ACE inhibitors improve cardiac function in the failing heart by multiple mechanisms including the reduction of oxidative stress, myocardial inflammation and Ca2+-handling abnormalities in cardiomyocytes.

Changes in left ventricular function and remodeling after myocardial infarction in hypothyroid rats

It has been shown that hypothyroidism may lead to delayed wound healing after experimental myocardial infarction (MI) in rats and increased infarct size in dogs. However, the long-term effect of hypothyroidism on left ventricular (LV) remodeling after MI has not been determined. Adult female Sprague-Dawley rats with and without surgical thyroidectomy (TX) were used in the study. Four weeks after TX, MI or sham MI was performed on TX and non-TX rats. Rats from all groups were examined 4 wk later. Four weeks after TX, hypothyroid-induced LV dysfunction was confirmed by echocardiography. In terminal experiments 4 wk after MI, TX sham-MI rats showed smaller hearts and impaired LV function compared with non-TX sham-MI controls. TX + MI rats showed smaller hearts with bigger infarct areas, higher LV end-diastolic pressures, and greater impairment of relaxation (−dP/d t) compared with non-TX MI rats. Relative changes after MI between TX and non-TX rats for most other hemodynamic and echocardiographic indexes were similar. These results suggest that preexisting hypothyroidism exaggerates post-MI remodeling and worsens LV function, particularly diastolic function.

Optimal time for mesenchymal stem cell transplantation in rats with myocardial infarction

BACKGROUND

Bone marrow mesenchymal stem cell (MSC) transplantation is a promising strategy in the treatment of myocardial infarction (MI). However, the time for transplanting cells remains controversial. The aim of this study was to find an optimal time point for cell transplantation.

METHODS

MSCs were isolated and cultured from Sprague-Dawley (SD) rats. MI model was set up in SD rats by permanent ligation of left anterior descending coronary artery. MSCs were directly injected into the infarct border zone at 1 h, 1 week and 2 weeks after MI, respectively. Sham-operated and MI control groups received equal volume of phosphate buffered saline (PBS). At 4 weeks after MI, cardiac function was assessed by echocardiography; vessel density was analyzed on hematoxylin-eosin stained slides by light microscopy; the apoptosis of cardiomyocytes was evaluated by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay; the expressions of proteins were analyzed by Western blot.

RESULTS

MSC transplantation improved cardiac function, reduced the apoptosis of cardiomyocytes and increased vessel density. These benefits were more obvious in 1-week group than in 1-h and 2-week groups. There are more obvious increases in the ratio of bcl-2/bax and the expression of vascular endothelial growth factor (VEGF) and more obvious decreases in the expression of cleaved-caspase-3 in 1-week group than those in other two groups.

CONCLUSION

MSC transplantation was beneficial for the recovery of cardiac function. MSC transplantation at 1 week post-MI exerted the best effects on increases of cardiac function, anti-apoptosis and angiogenesis.

Short term triiodo-L-thyronine treatment inhibits cardiac myocyte apoptosis in border area after myocardial infarction in rats

Thyroid hormone (TH) levels decline after a myocardial infarction (MI). Treatment with TH has been shown to improve left ventricular (LV) function in MI and other cardiovascular diseases, but the mechanisms are not clear. We have previously shown that TH can prevent myocyte apoptosis via Akt signaling in cultured neonatal rat cardiomyocytes. In this study, the effects of triiodo-L-thyronine (T3) on LV function and myocyte apoptosis after MI was examined in rats. After surgery, MI rats were treated with T3 for 3 days. Compared with sham-operated rats, MI rats showed significantly increased LV chamber dimension during systole and decreased LV function. T3 treatment increased LV +/-dP/dt but did not change LV chamber dimensions. MI rats also showed significantly increased myocyte apoptosis in the border area as assessed by DNA laddering and TUNEL assay. T3 treatment decreased the amount of DNA laddering, and reduced TUNEL positive myocytes in the border area, which was associated with phosphorylation of Akt at serine 473. These results suggest that T3 can protect myocytes against ischemia-induced apoptosis, which may be mediated by Akt signaling.

Role of renin-angiotensin system in development of heart failure induced by myocardial infarction in rats

We investigated the morphologic and functional changes of infarcted rat hearts under a paradigm of angiotensinconverting enzyme inhibition. Myocardial infarction was induced by left coronary artery ligation and a control group (SHAM) underwent sham-operation. Infarcted rats received normal drinking water with (CAP group) or without (INF group) captopril. Functional assessment was performed by electro (ECG) and echocardiogram (ECHO) just before and 21 days after surgery. The ECG of INF and CAP showed similar values and resembled healed infarct after surgery. The most outstanding differences between INF and CAP were the prevention of the increase of P-wave and attenuation both in rightward deviation of the QRS axis and Q-wave amplitude in CAP compared with INF. The ECHO showed that captopril treatment improved the diastolic filling more than systolic performance. Cardiac dilatation and left congestive heart failure were observed only in INF. Both infarcted groups showed a scar tissue in the left ventricular wall, but the INF showed a higher scar area than CAP (49.7 ± 5.24 vs. 22.33 ± 6.19 respectively). These data suggest that the renin-angiotensin system induces morphologic and functional changes in post-infarcted rat hearts and which can be assessed by non-invasive exams.

Cellular cardiomyoplasty in large myocardial infarction: can the beneficial effect be enhanced by ACE-inhibitor therapy?

BACKGROUND

Cellular cardiomyoplasty with bone marrow derived stromal (MSC) and mononuclear (BMNC) cells has been shown to improve performance of infarcted hearts. We performed a comparative study with MSC and BMNC and tested the hypothesis that captopril treatment could enhance the beneficial effect of cell therapy in large myocardial infarctions.

METHODS

Male syngeneic Wistar rats underwent experimental infarction and were randomized to receive 1-3 x 10(6) MSC, 10(8) BMNC or vehicle (BSS group). Two additional groups were treated with captopril and received 1-3 x 10(6) MSC (Cap.MSC) or vehicle (Cap).

RESULTS

The ejection fraction (EF%) of MSC and BMNC-treated rats was higher than in the BSS rats, eight weeks after transplantation (33.0+/-4.0, 34.0+/-2.0 and 20.0+/-2.0% respectively, P<0.01). Both captopril-treated groups improved EF% similarly. But only captopril plus MSC treatment almost restored cardiac function to control levels, 8 weeks after injection (60.50+/-5.40% vs. 41.00+/-4.50% in Cap.MSC and Cap respectively, P<0.05). Many DAPI-labelled cells were found in the scar tissue of the left ventricle only in the Cap.MSC group.

CONCLUSIONS

Cell transplantation with both MSC and BMNC produced a similar stabilisation of heart function, but the success of the cell engraftment and the recovery of cardiac performance were dependent on concomitant treatment with captopril.

Performance of two-dimensional Doppler echocardiography for the assessment of infarct size and left ventricular function in rats

Although echocardiography has been used in rats, few studies have determined its efficacy for estimating myocardial infarct size. Our objective was to estimate the myocardial infarct size, and to evaluate anatomic and functional variables of the left ventricle. Myocardial infarction was produced in 43 female Wistar rats by ligature of the left coronary artery. Echocardiography was performed 5 weeks later to measure left ventricular diameter and transverse area (mean of 3 transverse planes), infarct size (percentage of the arc with infarct on 3 transverse planes), systolic function by the change in fractional area, and diastolic function by mitral inflow parameters. The histologic measurement of myocardial infarction size was similar to the echocardiographic method. Myocardial infarct size ranged from 4.8 to 66.6% when determined by histology and from 5 to 69.8% when determined by echocardiography, with good correlation (r = 0.88; P < 0.05; Pearson correlation coefficient). Left ventricular diameter and mean diastolic transverse area correlated with myocardial infarct size by histology (r = 0.57 and r = 0.78; P < 0.0005). The fractional area change ranged from 28.5 +/- 5.6 (large-size myocardial infarction) to 53.1 +/- 1.5% (control) and correlated with myocardial infarct size by echocardiography (r = -0.87; P < 0.00001) and histology (r = -0.78; P < 00001). The E/A wave ratio of mitral inflow velocity for animals with large-size myocardial infarction (5.6 +/- 2.7) was significantly higher than for all others (control: 1.9 +/- 0.1; small-size myocardial infarction: 1.9 +/- 0.4; moderate-size myocardial infarction: 2.8 +/- 2.3). There was good agreement between echocardiographic and histologic estimates of myocardial infarct size in rats.

Effects of combined inhibition of the Na+-H+ exchanger and angiotensin-converting enzyme in rats with congestive heart failure after myocardial infarction

1 We investigated the single vs the combined long-term inhibition of Na(+)-H(+) exchanger-1 (NHE-1) and ACE in rats with congestive heart failure induced by myocardial infarction (MI). 2 Rats with MI were randomized to receive either placebo, cariporide (3000 p.p.m. via chow), ramipril (1 mg kg(-1) day(-1) via drinking water) or their combination for 18 weeks starting on day 3 after surgery. 3 Cardiac morphology and function was assessed by echocardiography and by means of a 2.0 F conductance catheter to determine left ventricular (LV) pressure volume relationships. 4 MI for 18 weeks resulted in an increase in LV end-diastolic diameter (LVDed) in the placebo-treated group when compared to sham (placebo: 1.1+/-0.04 cm; sham: 0.86+/-0.01; P<0.05). Combined inhibition of NHE-1 and ACE, but not the monotherapies, significantly reduced LVDed (1.02+/-0.02 cm). 5 Preload recruitable stroke work (PRSW), dp/dt(max) (parameter of systolic function) and end-diastolic pressure volume relationship (EDPVR, diastolic function) were significantly impaired in placebo-treated MI group (PRSW: 39+/-7 mmHg; dp/dt(max): 5185+/-363 mmHg s(-1); EDPVR: 0.042+/-0.001 mmHg microl(-1); all P<0.05). Cariporide treatment significantly improved PRSW (64+/-7 mmHg), dp/dt(max) (8077+/-525 mmHg s(-1)) and EDPVR (0.026+/-0.014 mmHg microl(-1)), and reduced cardiac hypertrophy in rats with MI. Combined inhibition of NHE-1 and ACE had even a more pronounced effect on PRSW (72+/-5 mmHg) and EDPVR (0.026+/-0.014 mmHg microl(-1)), as well as cardiac hypertrophy that, however, did not reach statistical significance compared to cariporide treatment alone. 6 The NHE-1 inhibitor cariporide significantly improved LV remodeling and function in rats with congestive heart failure induced by MI. The effect of cariporide was comparable or tended to be stronger (e.g. systolic function) compared to ramipril. Combined treatment with cariporide and ramipril tended to be more effective on LV remodeling in rats with heart failure than the single treatments. Thus, inhibition of the NHE-1 may be a promising novel therapeutic approach for the treatment of congestive heart failure.

Effect of β-Blockers on Cardiac Function and Calcium Handling Protein in Postinfarction Heart Failure Rats

OBJECTIVES

The normal expression of Ca2+-handling protein is critical for efficient myocardial function. The present study was designed to test the hypothesis that beta-blocker treatment may attenuate left ventricular (LV) remodeling and cardiac contractile dysfunction in the failing heart, which may be associated with alterations of Ca2+-handling protein

METHODS

We investigated the change of LV remodeling and function in a rat model of heart failure due to myocardial infarction (MI) with or without carvedilol (30 mg/kg/d) or metoprolol (60 mg/kg/d) treatment for 6 weeks (n = 9 in the MI plus carvedilol group, and n = 8 in every other group). The expression of messenger RNA and proteins of sarcoplasmic reticulum Ca2+-adenosine triphosphatase (SERCA) and phospholamban in cardiomyocytes of all rats were also measured

RESULTS

There was significant LV remodeling and cardiac contractile dysfunction in MI rats. The messenger RNA and protein expression of SERCA were down-regulated (p < 0.01), but the expression of phospholamban messenger RNA and protein were up-regulated (p < 0.01) in MI rats compared to sham-operated rats. After the treatment with beta-blockers, LV remodeling and function were clearly improved. Carvedilol was better in attenuating the weight of the LV and the relative weight of the right ventricle than metoprolol (p < 0.05). beta-Blockers restored the low expression of SERCA (p < 0.05) but showed no effect on phospholamban expression (p > 0.05). Moreover, carvedilol induced a more significant improvement of SERCA expression than metoprolol (p < 0.05)

CONCLUSIONS

Beta-blockers are effective in preventing LV remodeling and cardiac contractile dysfunction in the failing heart. The molecular mechanism may be related to normalization of SERCA expression.

COMPARISON OF LOW and HIGH DOSES OF CARVEDILOL ON RESTORATION OF CARDIAC FUNCTION and CALCIUM-HANDLING PROTEINS IN RAT FAILING HEART

1. The beta-adrenoceptor antagonist carvedilol reverses cardiac dysfunction in the failing heart. A recent study showed that beta-adrenoceptor antagonists indirectly normalize Ca(2+)-regulatory proteins. The relationship between these two phenomena and the suitable dosage of carvedilol remains unclear. 2. We investigated the change in left ventricular (LV) remodelling and function in a rat model of heart failure due to myocardial infarction (MI) with or without carvedilol (30 or 2 mg/kg per day) treatment for 6 weeks. The expression of mRNA and proteins of sarcoplasmic reticulum Ca(2+)-ATPase (SERCA) and phospholamban (PLB) in cardiomyocytes was also measured. 3. There was significant LV remodelling and cardiac contractile dysfunction in MI rats. The expression of SERCA mRNA and protein were downregulated (P < 0.01), but the expression of PLB mRNA and protein were upregulated (P < 0.01) in MI rats compared with sham-operated rats. After treatment with carvedilol, LV remodelling and cardiac contractile dysfunction were clearly improved. Low-dose carvedilol was better at improving some parameters of LV remodelling and function than the high dose. Carvedilol partially restored the low expression of SERCA (P < 0.05), but had no effect on PLB expression (P > 0.05). Moreover, low-dose carvedilol induced a more significant improvement in SERCA expression than did the high dose (P < 0.05). 4. The results of the present study suggest that carvedilol is effective in improving LV remodelling and cardiac contractile dysfunction after MI. This may be related to the normalization of SERCA expression.

Comparative effects of carvedilol and losartan alone and in combination for preventing left ventricular remodeling after acute myocardial infarction in rats

It has been verified that losartan has beneficial effects on ventricular remodeling (VRM) after acute myocardial infarction (AMI), but the effects of carvedilol alone or in combination with losartan on this condition have not been defined. The present study used rats to compare the effects of carvedilol and losartan alone and in combination for preventing VRM after AMI. After ligation of the left coronary artery, 100 surviving female Sprague-Dawley rats were randomly assigned to 1 of 4 groups: (1) AMI control (n=25), (2) carvedilol (Car, 1 mg x kg(-1) x day(-1)) (n=25), (3) losartan (Los, 3 mg x kg(-1) x day (-1)) (n=25), and (4) Car (1 mg x kg (-1). day(-1)) + Los (3 mg x kg(-1) x day (-1)) (n=25). A sham-operated group (n=17) was also randomly selected. Drugs were administered by gastric gavage for 4 weeks. After hemodynamic studies, the hearts were fixed and analyzed pathologically. Exclusive of the rats that had died or had an infarct size <35% or >55%, complete data were obtained for 65 rats, comprising AMI control (n=13), Car (n=12), Los (n=13), combination (n=14), and sham (n=13) groups. There were no significant differences in the size of infarct among the 4 AMI groups (45.8 approximately 46.7%, all p>0.05). Compared with the sham group, left ventricular (LV) end-diastolic pressure (LVEDP), volume (LVV), weight (LVW) and septal thickness (STh) were all significantly increased (all p<0.001), whereas +/-dp/dt was significantly decreased (both p<0.001) in the AMI group. In comparison with the AMI group, LVEDP, LVV, LVW and STh were all significantly decreased (LVEDP: 12.7+/-2.3, 9.7+/-2.8, and 8.6+/-3.5 mmHg vs 20.6+/-2.7 mmHg, all p<0.001; LVV: 0.74+/-0.07, 0.76+/-0.07, and 0.70+/-0.09 ml vs 0.86+/-0.05 ml, all p<0.05; LVW: 668.4+/-52.0, 702.6+/-45.4, and 683.9+/-67.7 mg vs 787.3+/-76.7 mg, p<0.05 approximately 0.001; STh: 1.57+/-0.05, 1.48+/-0.07, and 1.46+/-0.07 mm vs 1.71+/-0.04 mm, all p<0.05), whereas +/-dp/dt was significantly increased (all p<0.05) in the Car, Los, and combination groups, with LVEDP decreasing more in both Los and the combination groups than in the Car group alone (p<0.05) and STh decreasing more in the combination group than in the Car group alone (p<0.05). Carvedilol and losartan alone and in combination all prevent VRM after AMI in rats, with almost equivalent effect.

Comparative effects of cilazapril, carvedilol and their combination in preventing from left ventricular remodelling after acute myocardial infarction in rats

OBJECTIVES

To compare the effects of cilazapril, carvedilol and their combination in preventing left ventricular remodelling (LVRM) after acute myocardial infarction (AMI) in rats.

METHODS

Twenty-four hours after left coronary artery ligation, 100 surviving AMI female Sprague-Dawley rats were randomly assigned to: (1) AMI control (n=25); (2) cilazapril (Cila, 1 mg/kg/day) (n=25); (3) carvedilol (Car, 1 mg/kg/day) (n=25), and (4) cilazapril (1 mg/kg/day)+ carvedilol (1 mg/kg/day) (combination) (n=25) groups. A sham-operated group (n=17) was selected randomly as a non-infarction control. After four weeks of therapy with the drugs given by gastric gavage, haemodynamic studies were performed, following which the rat hearts were fixed and pathologically analysed. Rats with MI size <35% or >55% were excluded. Complete data were obtained in 64 rats, comprising AMI control (n=13), Cila (n=12), Car (n=12), Combination (n=14), and sham-operated (n=13) groups.

RESULTS

There were no significant differences in MI size between the four AMI groups (45.2 46.7%, p>0.05). Compared with the sham-operated group, left ventricular (LV) end diastolic pressure (LVEDP), volume (LVV), weight (LVW), septal thickness (STh) and right ventricular weight (RVW) were all significantly increased (all p<0.001) in the AMI group, while the LV pressure maximal rate of rise and fall ( dp/dt) was significantly decreased (all p<0.001). In comparison with the AMI group, LVEDP, LVV, LVW, STh and RVW were all significantly decreased, while dp/dt was significantly increased in the Cila, Car, and combination groups, with LVEDP and STh decreasing more in the combination group than in the two monotherapy groups (p<0.05 0.01). There were no significant differences in other variables between the three therapy groups.

CONCLUSIONS

Cilazapril, carvedilol and their combination are all effective in preventing LVRM after AMI in rats, and in improving haemodynamics and LV function, with the combination therapy being superior to monotherapy in all respects.

Transplantation of embryonic stem cells improves cardiac function in postinfarcted rats

Massive loss of cardiac myocytes after myocardial infarction (MI) is a common cause of heart failure. The present study was designed to investigate the improvement of cardiac function in MI rats after embryonic stem (ES) cell transplantation. MI in rats was induced by ligation of the left anterior descending coronary artery. Cultured ES cells used for cell transplantation were transfected with the marker green fluorescent protein (GFP). Animals in the treated group received intramyocardial injection of ES cells in injured myocardium. Compared with the MI control group injected with an equivalent volume of the cell-free medium, cardiac function in ES cell-implanted MI animals was significantly improved 6 wk after cell transplantation. The characteristic phenotype of engrafted ES cells was identified in implanted myocardium by strong positive staining to sarcomeric alpha-actin, cardiac alpha-myosin heavy chain, and troponin I. GFP-positive cells in myocardium sectioned from MI hearts confirmed the survival and differentiation of engrafted cells. In addition, single cells isolated from cell-transplanted MI hearts showed rod-shaped GFP-positive myocytes with typical striations. The present data demonstrate that ES cell transplantation is a feasible and novel approach to improve ventricular function in infarcted failing hearts.

Effects of stimulation frequency on calcium transients in noninfarcted myocardium: modulation by chronic captopril treatment

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibition produces beneficial effects in patients and experimental animals after myocardial infarction (MI). However, the mechanisms accounting for these effects are incompletely understood.

METHODS AND RESULTS

We recorded contractile force and intracellular calcium (Ca2+i) transients in papillary muscles from sham-operated rats (n = 8), untreated rats with heart failure after MI (MI; n = 7), and MI rats receiving captopril treatment for 5 weeks (n = 4). All studies were performed 6 weeks after MI or sham surgery. In muscles from sham-operated rats, increasing stimulation frequency from 0.33 to 3.0 Hz was associated with no change in the peak amplitude or the time to the peak of the Ca2+i transients. In contrast, in muscles from MI rats, stimulation at 3.0 Hz caused a marked increase in the amplitude of the Ca2+i transients (170% of baseline), prolongation of the time to the peak of the Ca2+i transient (54 +/- 2 to 84 +/- 8 * ms), and a prominent alternans pattern. Tissue hypoxia did not appear to be responsible for the abnormal response to rapid stimulation in the myocardium from infarcted hearts because bubbling the bath solution with 95% N2/5% CO2 resulted in no change in the amplitude of the Ca2+i transients in muscles from both groups. Muscles from captopril-treated MI rats responded like sham-operated controls, with no change in the amplitude or time course of the Ca2+i transients during rapid stimulation.

CONCLUSION

In myocardium isolated from rats with postinfarction heart failure, increasing stimulation frequency causes marked increases in peak Ca2+i , prolongation of the time course of the Ca2+i transient, and Ca2+i alternans. Despite the increased Ca2+i transients, contractility declined during rapid pacing. We hypothesize that these changes could be explained by a frequency-related decline in intracellular pH and/or a decrease in sarcolemmal Ca2+ extrusion. The frequency-dependent abnormalities of cellular Ca2+ regulation in the infarcted heart are prevented by long-term treatment with an ACE inhibitor.

Effects of propranolol treatment on left ventricular function and intracellular calcium regulation in rats with postinfarction heart failure

1. Chronic treatment with beta-adrenergic blocking agents can improve survival in patients with heart failure. The mechanisms underlying the beneficial effects and whether these effects are generalizable to ischaemic heart failure are unresolved. 2. We performed echocardiographic-Doppler examinations in rats (n=28) 1 and 6 weeks after myocardial infarction (MI) or sham surgery. Rats were randomized to no treatment or propranolol (500 mg/l in drinking water) after the first echocardiogram. Isometric contractions and intracellular Ca transients were recorded simultaneously in noninfarcted left ventricular (LV) papillary muscles. 3. Untreated MI rats had significant LV dilatation (10.6+/-0.4* vs 8.9+/(-0.3) mm, MI vs control), impaired systolic function (fractional shortening=11+/-2* vs 38+/-2%), and a restrictive LV diastolic filling pattern. MI rats receiving propranolol had similar LV chamber sizes (10.6+/(-0.5) mm) and systolic function (13+/(-2%). The propranolol treated animals had higher LV end-diastolic pressures (27+/-2* vs 20+/(-3 mmHg) and a more restricted LV diastolic filling pattern (increased ratio of early to late filling velocities and more rapid E wave deceleration rate). Contractility of papillary muscles from untreated MI rats was depressed (1.6+/(-0.3) vs 2.4+/(0.5 g mm(-2). In addition, Ca transients were prolonged and the inotropic response to isoproterenol was blunted. Propranolol treatment did not improve force development (1.6+/(-0.3 g mm(-2) or the duration of Ca transients during isoproterenol stimulation. 4. Chronic propranolol treatment in rats with postinfarction heart failure did not improve LV remodeling or systolic function. LV diastolic pressures and filling patterns were worsened by propranolol. Treatment also did not produce appreciable improvement in contractility, intracellular Ca regulation or beta-adrenergic responsiveness in the noninfarcted myocardium.

Effects of candesartan and cilazapril on rats with myocardial infarction assessed by echocardiography

The purpose of this study was to compare the angiotensin II type 1 receptor antagonist candesartan cilexitil (candesartan) and the angiotensin-converting enzyme inhibitor cilazapril on cardiac function, assessed by Doppler echocardiography and cardiac gene expression associated with cardiac remodeling, in rats with myocardial infarction. Candesartan or cilazapril was administered after myocardial infarction. At 1 and 4 weeks after myocardial infarction, cardiac function and mRNA expression in noninfarcted myocardium were analyzed. Candesartan and cilazapril equally prevented increases in hypertrophy in noninfarcted myocardium, left ventricular dilatation, and ejection fraction at 4 weeks. The E-wave/A-wave velocity ratio and the rate of E-wave deceleration, measures of diastolic function, increased to 9.2+/-0.6 and 26.3+/-2. 6 m/s2 at 1 week after myocardial infarction. Candesartan and cilazapril, administered at a dose of 1 mg/kg per day, prevented increases in E-wave/A-wave velocity ratio and E-wave deceleration at 1 and 4 weeks. Candesartan and cilazapril significantly suppressed increased mRNA expression of beta-myosin heavy chain, alpha-skeletal actin, and atrial natriuretic peptide in noninfarcted ventricle at 1 and 4 weeks and expression of collagen I and III at 4 weeks to a similar extent. When given at a dose of 10 mg/kg per day, both candesartan and cilazapril prevented cardiac dysfunction and gene expression to the same extent as when given at 1 mg/kg per day. In conclusion, Doppler echocardiography showed that candesartan and cilazapril equally improved systolic and diastolic function and that ventricular remodeling accompanied modulation of cardiac gene expression.

Angiotensin II type 1-receptor antagonist candesartan cilexitil prevents left ventricular dysfunction in myocardial infarcted rats

The purpose of this study was to analyze the effect of the angiotensin II type 1-receptor antagonist candesartan cilexitil on left ventricular systolic and diastolic function and mRNA expression of contractile proteins, collagen, and Ca2+ handling protein in myocardial-infarcted rats. After myocardial infarction, the animals were randomly assigned to candesartan cilexitil-treated or untreated groups (MI). We performed Doppler-echocardiographic examination and measured the hemodynamics at four and twelve weeks after myocardial infarction. Following these measurements, their cardiac mRNA was analyzed. At four weeks in MI, left ventricular end-diastolic dimension increased (Control, 6.2+/-0.6 mm; MI, 8.7+/-0.6 mm; P < 0.01), fractional shortening decreased (Control, 41+/-5%; MI, 16+/-3%; P < 0.01) and E wave deceleration rate increased (Control, 14.3+/-2.0 m/sec2; MI, 23.3+/-2.3 m/sec2; P < 0.01). Candesartan cilexitil significantly prevented these changes. The mRNA expressions of beta-myosin heavy chain, alpha-skeletal actin, atrial natriuretic peptide, and collagens I and III in the non-infarcted left ventricle and right ventricle were increased at four weeks and were significantly suppressed by treatment with candesartan cilexitil. At four weeks, Na+-Ca2+ exchanger mRNA expression was increased, and candesartan cilexitil suppressed this increase. At twelve weeks, sarcoplasmic reticulum Ca2+-ATPase mRNA expression in the infarcted region including the adjacent non-infarcted left ventricle and right ventricle were decreased and candesartan cilexitil restored it to the control level. Candesartan cilexitil prevented the systolic and diastolic dysfunction and abnormal cardiac mRNA expression in myocardial-infarcted rats.

Short- and long-term effects of early fosinopril administration in patients with acute anterior myocardial infarction undergoing intravenous thrombolysis: results from the Fosinopril in Acute Myocardial Infarction Study. FAMIS Working Party

BACKGROUND

Angiotensin-converting enzyme inhibitors are used in patients who have myocardial infarction with left ventricular (LV) dysfunction. Few data are available in patients whose LV function is within the normal range.

METHODS AND RESULTS

The Fosinopril in Acute Myocardial Infarction Study was a 2-year, randomized, double-blind, placebo-controlled, multicenter study of 285 patients with anterior acute myocardial infarction and was designed to investigate the effects of the early (<9 hours) administration of fosinopril and thrombolysis on (1) changes in echocardiographically evaluated LV volumes at 3 months and (2) long-term occurrence of death and congestive heart failure. LV volumes were normal at baseline in more than 70% of patients and were comparable between groups both at baseline and after 3 months of treatment. Fosinopril-treated patients showed a 30% reduction in the 2-year combined prevalence of death or moderate-to-severe congestive heart failure (New York Heart Association class III-IV) despite having a worse clinical profile at baseline. The benefit of fosinopril was confirmed both in patients without congestive heart failure at admission and in those with ejection fraction >40% at baseline. Moreover, the incidence of significant ventricular arrhythmias was lower in the fosinopril group (0.8% vs 6.0%, p < 0.02).

CONCLUSIONS

The results of the Fosinopril in Acute Myocardial Infarction Study suggest that early treatment with fosinopril can benefit patients with acute myocardial infarction in addition to a prevention of LV remodeling.