Dobutamine stress echocardiography predicts left ventricular remodeling after acute myocardial infarction

BACKGROUND AND OBJECTIVES

Left ventricular (LV) remodeling after acute myocardial infarction (MI) is strongly related to infarct size. The contribution of viability in the infarct zone and the presence of multivessel disease remains unknown. Because dobutamine stress echocardiography (DSE) can estimate infarct size and detect myocardial viability and multivessel disease, we postulated that DSE can accurately predict LV remodeling after acute MI.

METHODS

To test this hypothesis, 30 patients age 59 +/- 15 years, 21 men, 14 with anterior MI, underwent multistage DSE (low dose, 5 to 10 microg, and peak dose) during the first week after MI occurred. Follow-up echocardiography was performed at >/=1 year. LV remodeling (2 SD increase in LV volume) occurred in 17 of 30 patients. Remodeling occurred in 12 (92%) of 13 patients with large nonviable infarct and in 1 (13%) of 8 patients with large viable infarct (P <.001). Univariate predictors of LV remodeling were baseline ejection infarct (P <.01), infarct size (number of akinetic segments at low dose P <.01), age (P <.05), and multivessel coronary disease (P <. 01). The only multivariate predictor of remodeling was infarct size. Viability of infarct zone was a negative predictor of LV remodeling.

CONCLUSION

DSE performed during the first week after acute MI predicts subsequent LV remodeling. Infarct size, nonviability of the infarct zone, and age are independent predictors of LV remodeling. Myocardial viability is a strong negative predictor of LV remodeling.

Left ventricular remodeling after aortic valve replacement with the Toronto-SPV prosthesis

The remarkable hemodynamic features of the aortic Toronto SPV prosthesis have been reported. To assess the efficacy of these characteristics to produce a favorable left ventricular remodeling and to test the limits of the dobutamine stress test to check these results, 25 consecutive patients, who had undergone aortic valve replacement with Toronto SPV, were monitored with dobutamine and exercise stress tests for 1 year. Among the prosthetic and left ventricular morphological and functional parameters evaluated, dobutamine infusion produced an overestimation of prosthetic and left ventricular outflow tract gradients, effective orifice area, and prosthetic resistance compared with the more physiological exercise test (P<.01). These misleading results were probably due to the inotropic and unloading effects of dobutamine in still hypertrophied hearts. Indexed myocardial mass and wall thickness decreased significantly during the follow-up period (P<.01), whereas left ventricular diastolic diameter and ejection fraction showed no significant variations. These data show that the positive left ventricular remodeling is due only to the regression of the hypertrophy and not to the reduction of left ventricular diameters. Based on results from this study, the dobutamine stress test should be avoided to evaluate patients with aortic valve prostheses and still present left ventricular hypertrophy. The Toronto SPV produces a favorable left ventricular remodeling during the first year of follow-up, and is likely to improve.

Left ventricular geometry and function in patients with aortic stenosis: gender differences

BACKGROUND

Gender differences in cardiac size have been described in normal and pathological conditions in human and animals. Sex determination of a pattern of hypertrophy as a response to pressure overload has not been extensively evaluated and is still poorly understood in humans.

METHODS AND RESULTS

To investigate the influence of gender in the left ventricle remodelling and preservation of the left ventricle function 195 adults (140 men and 55 women) with isolated aortic stenosis were evaluated. The mean age was 52 +/- 11 years for men and 53 +/- 13 years for women. All the patients had similar degree of aortic stenosis finally treated with valve replacement, similar clinical status and no signs of coronary artery disease in coronary angiograms. On echocardiography the left ventricle of women had a smaller the end systolic (30.5 +/- 7.8 vs. 39.4 +/- 11.2, P<0.001) and the end diastolic (49.4 +/- 9 vs. 57.3 +/- 11, P<0.001) chamber size. The female left ventricle generated a higher relative wall thickness (0.65 +/- 0.21 vs. 0.52 +/- 0.12, P<0.01), a greater fractional shortening (35.3 +/- 8.5 vs. 32.0 +/- 9.0, P<0.01) and a higher ejection fraction (64.4 +/- 12.7 vs. 57.5 +/- 14.6, P<0.001). The left ventricle posterior wall thickness and the septal thickness indexes were similar in both groups. There were also significant differences between the two groups in the left ventricle mass index.

CONCLUSIONS

Gender has an important influence on the left ventricle adaptation pattern to pressure overload due to aortic stenosis. Women developed a greater degree of left ventricle hypertrophy documented as changes in left ventricle geometry (increased relative wall thickness, left ventricular mass) and left ventricle function (fractional shortening and ejection fraction).

Relation of plasma brain and atrial natriuretic peptides to left ventricular geometric patterns in essential hypertension

We investigated whether plasma brain and atrial natriuretic peptide (BNP and ANP, respectively) levels could reflect left ventricular (LV) geometry and function in patients with mild to moderate essential hypertension. A positive correlation was found between LV mass index (LVMI) and plasma ANP levels in 84 untreated, hypertensive patients, but not between LVMI and plasma BNP levels. As compared with other geometric patterns, plasma BNP levels were increased in concentric hypertrophy, in which LVMI was increased and LV diastolic function was decreased. These data suggest that production of BNP was increased in hypertensive patients with concentric hypertrophy via LV overload or depression of diastolic function.

Ventricular remodeling after acute myocardial infarction

The term ventricular remodeling has been coined to describe the geometrical changes in size and shape of the left ventricle occurring after large myocardial infarcts. We do not exactly know what initiates this process. Slipping of myofilaments following destruction of connective tissue--probably due to metalloproteinase activation--could be the initial event. As a consequence, wall stress is increased triggering deleterious adaptation processes, such as: - intracardiac angiotensin II generation; - cardiac endothelin formation and release; - pro-apoptotic signals for cardiomyocytes; - hypertrophic signals for fibroblasts and cardiomyocytes. This cascade of events is not only observed in the process of remodeling following myocardial infarction but is also operating during the progression of heart failure. Therapeutic principles therefore are similar in both conditions: - reduction of wall stress (pharmacological or mechanical unloading of the heart); - blockade of angiotensin II generation or of AT1-receptors (ACE-inhibitors or AT1 antagonists); - blockade of endothelin receptors (ET(A)-blockers); - blockade of adrenergic receptors (preferably beta1-adrenergic receptor blockers). Better understanding of the molecular mechanisms of the remodeling process already has fueled the search for new therapeutic interventions (such as endothelin receptor blockers, aldosterone antagonists and growth hormone application). Continuous research in this field may be especially rewarding if we will succeed in identifying the very first step in the cascade.

Temporal dissociation of left ventricular function and remodeling following experimental myocardial infarction in rats

BACKGROUND

Left ventricular function early after myocardial infarction (MI) predicts subsequent clinical outcome. Nevertheless, the relationship between early changes in left ventricular function and subsequent left ventricular remodeling has not been well defined.

METHODS AND RESULTS

To explore the temporal relationship between left ventricular function and remodeling after MI, rats (n = 63) underwent coronary artery ligation with and without reperfusion at 45 or 180 minutes or a sham operation. All animals were followed up by serial echocardiography preligation; 4, 24, and 48 hours; and 1, 2, 3, 4, 6, and 9 weeks after MI. Measures of global left ventricular size and function and regional wall motion were obtained at physiological heart rates. Histological infarct sizes (range, 0% to 52%) were determined in all animals. Within 4 hours of MI, fractional area change (FAC) decreased dramatically in association with an increase in left ventricular systolic cavity area, whereas diastolic area increased more gradually. Early FAC was related to infarct size (r = -0.82; P < .000), predicted the extent of left ventricular enlargement (P = .0001), and remained depressed throughout the duration of follow-up. Regional wall motion excursion and systolic wall thickness decreased in the infarcted and noninfarcted regions in animals with large infarctions.

CONCLUSIONS

The rate of left ventricular dilatation after MI in rats is proportional to initial left ventricular function, although left ventricular function remains relatively constant as the ventricle progressively enlarges. Regional myocardial function after a large MI is abnormal in noninfarcted as well as infarcted regions.

[Echocardiographic findings, pro-ANP and treatment in acute myocardial infarction without overt heart failure]

This study was undertaken to characterise patients without overt heart failure and with a left ventricular ejection fraction > or = 40% 2-7 days following an acute myocardial infarction. Patients with an ejection fraction > or = 40% (n = 868) had a lower prevalence of anterior myocardial infarction (p < 0.001) and lower levels of N-terminal pro-ANP (atrial natriuretic peptide) (p < 0.001) than those with ejection fraction < 40% (n = 305). Patients with ejection fraction > or = 40% had smaller left ventricular volume and mass (p < 0.001). Pro-ANP levels did not correlate significantly with left ventricular volume or ejection fraction in this group. Among patients with ejection fraction < 40%; statistically significant correlations between pro-ANP levels and both ejection fraction and left ventricular endsystolic volume were found. 64% and 61% of patients in the two groups were given thrombolytic treatment. In this study, most patients with acute myocardial infarction had an ejection fraction > or = 40%. Pro-ANP levels were not correlated with the ejection fraction or left ventricular volume. Approximately two thirds of the patients received thrombolytic treatment.

Myocardial infarction and remodeling in mice: effect of reperfusion

Anatomic and functional changes after either a permanent left anterior descending coronary artery occlusion (PO) or 2 h of occlusion followed by reperfusion (OR) in C57BL/6 mice were examined and compared with those in sham-operated mice. Both interventions generated infarcts comprising 30% of the left ventricle (LV) measured at 24 h and equivalent suppression of LV ejection velocity and filling velocity measured by Doppler ultrasound at 1 wk. Serial follow-up revealed that the ventricular ejection velocity and filling velocity returned to the levels of the sham-operated controls in the OR group at 2 wk and remained there; in contrast, PO animals continued to display suppression of both systolic and diastolic function. In contrast, ejection fractions of PO and OR animals were depressed equivalently (50% from sham-operated controls). Anatomic reconstruction of serial cross sections revealed that the percentage of the LV endocardial area overlying the ventricular scar (expansion ratio) was significantly larger in the PO group vs. the OR group (18 +/- 1.7% vs. 12 +/- 0.9%, P < 0.05). The septum that was never involved in the infarction had a significantly (P < 0.002) increased mass in PO animals (22.5 +/- 1.08 mg) vs. OR (17.8 +/- 1.10 mg) or sham control (14.8 +/- 0.99 mg) animals. Regression analysis demonstrated that the extent of septal hypertrophy correlated with LV expansion ratio. Thus late reperfusion appears to reduce the degree of infarct expansion even under circumstances in which it no longer can alter infarct size. We suggest that reperfusion promoted more effective ventricular repair, less infarct expansion, and significant recovery or preservation of ventricular function.

[Role of cardiac aldosterone in post-infarction ventricular remodeling in rats]

Synthesis of aldosterone (Aldo) and corticosterone (B) has been recently reported in rat heart. However, regulation of this synthesis in pathophysiological states remains unknown. Thus, this study aimed to analyze effects of a one-month myocardial infarction (MI) on cardiac steroidogenic system. Levels of terminal enzymes of B (11 beta-hydroxylase: 11 beta H) and aldo (Aldo-synthase: AS) synthesis were assayed by quantitative RT-PCR. Cardiac Aldo and B levels were assessed by celite colum chromatography and radioimmunoassay. MI raised AS mRNA levels by 2.0-fold (p < 0.05) but downregulated that of 11 beta H by 2.4 fold (p < 0.05) in the noninfarcted part of the left ventricle (LV). Cardiac steroids production followed a similar pattern of regulation. Aldo level was increased in MI (319 +/- 85 vs 87 +/- 11 pg/mg of protein in control, p < 0.05) whereas that of B fell (2,412 +/- 318 vs 4,624 +/- 857 pg/mg of protein in control, p < 0.05). MI also induced an 1.9-fold increase in cardiac Ang II level. Such cardiac regulations were prevented by Ang II-AT1 receptor antagonist losartan (8 mg/kg/day) treatment. The Aldo receptor antagonist spironolactone (20 mg/kg/day) had no effect. Plasma Aldo and B, and adrenal 11 beta H and AS mRNA levels were unchanged whatever the treatment. The MI-induced collagen deposition in noninfarcted area of the LV was reduced by both spironolactone and losartan treatments by 1.6- and 2.5-fold, respectively. These data indicate that MI is associated with tissue-specific activation of myocardial aldosterone synthesis. This activation is mediated by cardiac Ang II via AT1 receptor and the resultant increase of intracardiac aldosterone level may be involved in post-MI ventricular remodeling.

Managing congestive heart failure with thoracic electrical bioimpedance

Because of clinical utility, immediate feedback, absence of risk to the patient, portability, and use in virtually any practice setting, facilities using thoracic electrical bioimpedance monitoring are increasing throughout the world. Specialized centers treating patients with heart failure have shown remarkable benefits, both in health care costs and patient morbidity, attributable to the careful monitoring and management of patients with heart failure. The ability of thoracic bioimpedance monitoring to provide objective data in the management of congestive heart failure provides practitioners with the clinical reassurance to optimize pharmacologic therapy safely.

Myocarditis Treatment Trial

BACKGROUND

Remodeling of the left ventricle with the development of a spherical cavity occurs in dilated cardiomyopathy and is associated with a poor long-term prognosis. The early effects of myocarditis on left ventricular geometry have not been previously described or correlated with clinical outcome.

METHODS

The baseline echocardiograms of 35 patients with biopsy-confirmed myocarditis were compared with 20 normal controls. Left ventricular end-diastolic volume, long axis length, and mid-cavity diameter were measured. The degree of sphericity was expressed as the ratio of the mid-cavity diameter to the long axis length. Left ventricular ejection fraction was assessed by radionuclide angiography.

RESULTS

In patients with myocarditis, mean left ventricular volume of 81 +/- 29 mL/m(2) was significantly greater than 50 +/- 8 mL/m(2) in controls (P =.001). Chamber dilatation occurred primarily along the mid-cavity diameter, which measured 5.3 +/- 0.8 cm in patients with myocarditis versus 4.2 +/- 0.4 cm in controls (P =.001). The degree of left ventricular sphericity in patients with myocarditis, 0.64 +/- 0.08, was significantly greater than that of controls, 0.54 +/- 0.04 (P =.001). When patients were stratified according to left ventricular volume, patients with increased left ventricular volume (>75 mL/m(2)) were associated with a more spherical chamber and lower left ventricular ejection fraction than patients with a more normal left ventricular volume (</=75 mL/m(2)).

CONCLUSIONS

Active myocarditis is associated with early left ventricular remodeling and the development of a spherical chamber. These changes correlate with ventricular dilatation and reduced left ventricular ejection fraction.

Angiotensin II promotes integrin-mediated collagen gel contraction by adult rat cardiac fibroblasts

Remodeling is a fundamental cardiac response to injury and involves cardiac fibroblast proliferation and extracellular matrix (ECM) production. Angiotensin II (Ang II) directly promotes these changes in cardiac fibroblasts and thus, plays critical roles in cardiac hypertrophy and wound healing. Osteopontin, fibronectin and laminin mRNA were detected in total RNA harvested from cultured adult rat cardiac fibroblasts. Immunocytochemistry staining of cultured adult rat cardiac fibroblasts grown on coverslips revealed the presence of beta 3 integrins on the surfaces of the cells. In the present study, we investigated the role of Ang II in a model of wound repair using floating collagen gels harboring adult rat cardiac fibroblasts, and we determined which members of the integrin family existed on these cells. The presence of either MPIIIB10, a monoclonal antibody against osteopontin (7.2 micrograms/ml) or RGD (arginine-glycine-aspartate) peptide (10(4) M) had no effect on gel contraction. Osteopontin itself induced gel contraction; however this effect was completely neutralized by MPIIIB10 (7.2 micrograms/ml, RGD peptide (10(4) M) and a monoclonal antibody against rat beta 3 integrin (25 micrograms/ml). We identified alpha v, beta 3 and beta 5 integrins on adult rat cardiac fibroblasts by fluorescence-activated cell sorting and confirmed that RGD peptide and an antibody against beta 3 integrin completely blocked osteopontin-induced gel contraction. These results suggest that Ang II promotes cardiac wound healing and remodeling processes by inducing expression of osteopontin and beta 3 integrin by cardiac fibroblasts.

Relationship between remodeling and function of left ventricle and angiotensin II AT1 receptor expression after myocardial infarction in rats

OBJECTIVE

To determine the relationship between remodeling and dysfunction of left ventricle (LV) and the expression of the angiotensin II AT1 receptor mRNA after myocardial infarction (MI) in rats.

METHODS

Nine MI rats (Group A) and 8 sham-operated rats (Group B) were studied by both Doppler echocardiography and Dot blot using Digoxingenin-labelled cDNA probes.

RESULTS

Compared with Group B, Group A showed the increase in LV internal diastolic diameter (0.87 +/- 0.06 mm vs 0.66 +/- 0.03 mm, respectively, P < 0.01) and volume (0.73 +/- 0.09 ml vs 0.51 +/- 0.05 ml, P < 0.01). In addition, thinning of anterior wall, thickening of posterior wall, increasing of peak early filling velocity (peak E), decreasing of late filling velocity (peak A) and increasing of the E/A were demonstrated in MI rats 7 weeks after MI. The levels of the cardiac angiotensin II AT1 receptor mRNA in Group A were higher than those of Group B (2.2-fold).

CONCLUSIONS

Seven weeks after MI in rats, character of LV remodeling and dysfunction were developed and the expression of cardiac angiotensin II AT1 receptor mRNA was increased.

Gender differences in molecular remodeling in pressure overload hypertrophy

OBJECTIVES

The objective of this study was to examine gender differences in left ventricular (LV) function and expression of cardiac genes in response to LV pressure overload due to ascending aortic stenosis in rats.

BACKGROUND

Clinical studies have documented gender differences in the pattern of adaptive LV hypertrophy. Whether these differences result from intrinsic differences in molecular adaptation to pressure overload between men and women, or are related to other factors is not known.

METHODS

Male (n = 8) and female (n = 8) Wistar rats underwent ascending aortic stenosis and were studied 6 weeks after banding with gender-matched control rats (male n = 7; female n = 7). The LV contractile reserve was examined in isolated hearts from each group. We compared LV messenger ribonucleic acid (mRNA) levels of atrial natriuretic factor (ANF), beta-myosin heavy chain, sarcoplasmic reticulum Ca2+-adenosine triphosphatase (ATPase) and Na+-Ca2+ exchanger. Reverse transcriptase polymerase chain reaction was used to identify estrogen receptor transcript in cardiac myocytes and LV tissue.

RESULTS

The magnitude of LV hypertrophy (LVH) and systolic wall stress were similar in male and female animals with LVH. Male LVH hearts demonstrated a depressed contractile reserve; in contrast, contractile reserve was preserved in female LVH hearts. The expression of beta-myosin heavy chain and ANF mRNA was greater in male versus female LVH hearts. Sarcoplasmic reticulum Ca2+-ATPase mRNA levels were depressed in male LVH but not in female LVH compared with control rats, and Na+-Ca2+ exchanger mRNA levels were increased similarly in both male and female LVH hearts. Estrogen receptor transcript was detected in both adult male and female cardiac myocytes and LV tissue.

CONCLUSIONS

There are significant gender differences in the LV adaptation to pressure overload despite a similar degree of LVH and systolic wall stress in male and female rats. There is the potential for estrogen signaling through the adult myocyte estrogen receptor in both male and female rats to contribute to gender differences in gene expression in pathologic hypertrophy.

Chronic high-dose creatine feeding does not attenuate left ventricular remodeling in rat hearts post-myocardial infarction

OBJECTIVE

In heart failure, cardiac energy metabolism is compromised. The failing myocardium is characterized by reduced contents of both phosphorylated (phosphocreatine) and non-phosphorylated (free) creatine content as well as decreased energy reserve via creatine kinase (creatine kinase reaction velocity). These changes may contribute to cardiac dysfunction. The purpose of the present study was to determine whether chronic feeding with high-dose dietary creatine prevents the derangement of energy metabolism and the development of left ventricular remodeling in a rat model of heart failure, i.e. post-myocardial infarction (MI).

METHODS AND RESULTS

Rats were subjected to sham operation or left coronary artery ligation. Surviving rats were fed with 0% (untreated) or 3% creatine (related to weight of diet) for 8 weeks. Creatine feeding increased serum creatine levels significantly approximately 2-fold. Thereafter, hearts were isolated, perfused and left ventricular pressure-volume curves obtained. Steady state and dynamic (CK reaction velocity) high-energy phosphate metabolism was determined with 31P NMR spectroscopy. In both MI groups (treated n = 8, untreated n = 7), pressure-volume curves were shifted right- and downward compared to both sham groups (treated n = 5, untreated n = 7), i.e. creatine had no effect on left ventricular remodeling. Likewise, similar reductions of phosphocreatine, free creatine and creatine kinase reaction velocity (untreated sham 12.0 +/- 0.7 mmol/lxs; untreated MI 7.8 +/- 0.7*; treated sham 13.6 +/- 1.0; treated MI 7.2 +/- 1.1*; *p < 0.025 sham vs. MI) were found in both MI groups.

CONCLUSIONS

Chronic creatine feeding of post-MI rats is ineffective in preventing the functional and energetic derangements occurring post-MI. Inspite of increased serum creatine levels, neither the normal nor the failing heart accumulates additional creatine.

Hypertensive left ventricular remodeling and ACE-gene polymorphism

OBJECTIVE

To evaluate the relationship between ACE-gene polymorphism and left ventricular geometry in never treated hypertensives.

METHODS

We enrolled 200 hypertensive outpatients that underwent clinical and ambulatory blood pressure measurements, echocardiographic evaluation and analysis for insertion (I)/deletion (D) polymorphism by PCR. Patients with normal or increased (> 125 g/m2 in males and > 110 g/m2 in females) left ventricular mass were considered to have concentric remodeling or concentric left ventricular hypertrophy if their relative wall thickness was > or = 0.45.

RESULTS

The left ventricular mass index values (g/m2) were 136 +/- 30 in DD genotype, 124 +/- 26 in ID genotype, and 116 +/- 20 in II genotype (DD vs. ID P < 0.005; DD vs. II P < 0.05), and were unrelated to blood pressure. Ninety-six patients presented left ventricular hypertrophy (48.0%): 51 with concentric and 45 with eccentric hypertrophy. The eccentric left ventricular hypertrophy was detected in 32 (36.8%) DD patients, in ten (10.5%) ID patients (P < 0.05), and in three (16.6%) II patients. The relative septal thickness was 0.43 +/- 0.09 in DD genotype, 0.45 +/- 0.08 in ID genotype, and 0.43 +/- 0.10 in II genotype. In DD and ID genotypes, the relative posterior wall thickness (0.37 +/- 0.07 vs. 0.41 +/- 0.07; P < 0.0001) and the end-diastolic left ventricular internal dimension (52.8 +/- 3.3 mm vs. 48.3 +/- 2.8 mm; P < 0.0001) were statistically different.

CONCLUSIONS

The DD genotype of the ACE-gene is associated with an increased left ventricular mass and with a significantly higher prevalence of eccentric left ventricular hypertrophy, when compared to ID genotype.

Peripheral vascular remodeling in chronic heart failure: clinical relevance and new conceptualization of its mechanisms

Increased peripheral vascular tone is a critical factor in the deterioration of clinical stage and symptoms in chronic congestive heart failure (CHF) because of increased cardiac afterload and decreased nutritive skeletal muscle blood flow. Endothelial function as represented by nitric oxide (NO) production shows significant attenuation with the progression of clinical severity of CHF as determined by New York Heart Association class and exercise capacity parameters. This endothelial dysfunction emerges in the early stages of CHF. In the advanced stage of the condition, both endothelium-dependent and endothelium-independent dilator mechanisms are impaired in limb resistance vessels. This occurs because vascular endothelial function, especially NO production, is an important factor in the regulation of vasodilatory function, as well as making an important contribution to vascular structure. Furthermore, although such vasodilatory circulating factors as natriuretic polypeptides and newly discovered adrenomedullin are increased in heart failure, the vasodilatory potency of these polypeptide hormones in the limb vascular bed is significantly blunted. These observations suggest that peripheral circulatory failure in CHF is caused not only by simple arterial muscle constriction, but also by structural and functional changes, including receptor and postreceptor levels in the vasculature. This vascular remodeling may be an important mechanism underlying vasodilatory failure in both limb conduit and intraskeletal muscle vessels and may contribute significantly to left ventricular dysfunction and exercise intolerance in patients with heart failure.

Effects of ramipril on cardiac gene transcription levels of angiotensin II receptors after myocardial infarction

AIM

To study the early changes of cardiac angiotensin (Ang) II receptor gene transcription after myocardial infarction (MI) in rats chronically treated with the angiotensin-converting enzyme (ACE) inhibitor ramipril.

METHODS

MI was induced by left anterior descending coronary artery ligation in rats and sham-operated rats were used as control. Rats were treated daily with ramipril (1 mg.kg-1) or water, initiated 1 wk before surgery. Quantitative RT-PCR was applied to determine the Ang II receptors AT1, AT2 receptor gene mRNA levels in the non-infarcted myocardium.

RESULTS

AT1 and AT2 mRNA levels increased time point-dependently in the cardiac septum after MI reaching a peak on d 1. There was no significant difference of the myocardial AT1 and AT2 receptor mRNA levels between the ramipril-treated and water-treated rats after MI.

CONCLUSION

The AT1 and AT2 receptor gene transcription in the non-infarcted myocardium was associated with the process of cardiac remodeling after MI but not affected by ACE inhibition.

Can echocardiography identify mildly hypertensive patients at high risk, left untreated based on current guidelines?

OBJECTIVE

To determine whether the decision to treat uncomplicated mild hypertension with drugs, in accordance with the World Health Organization - International Society of Hypertension (WHO/ISH) guidelines based on a series of blood pressure (BP) measurements over 6 months, resulted in the treatment of patients at high risk on the basis of echocardiography.

METHODS

One hundred and eighteen patients with mild hypertension (diastolic blood pressure 90-105 mm Hg and/or systolic blood pressure 140-180 mm Hg) were examined by echocardiography at inclusion and followed up for 6 months by a single physician unaware of the echographic results.

RESULTS

Drug treatment was given to 48 patients, and 70 remained untreated. Treated patients had higher echographic indices than untreated patients (all P<0.05): left ventricular (LV) mass/body surface area (83.0+/-15.6 versus 75.3+/-14.8 g/m2), inter-ventricular septal thickness (9.7+/-1.7 versus 8.5+/-1.3 mm), LV posterior wall thickness (8.4+/-1.1 versus 7.8+/-1.1 mm), relative wall thickness (0.37+/-0.06 versus 0.34+/-0.06). LV geometry was normal in 98 patients, and 20 had LV concentric remodelling. The 10-year coronary disease risk (Framingham equation) was higher in the 20 patients with concentric remodelling than in those with normal LV geometry (10.4 versus 4.2%; P<0.005). Nine of these 20 patients were still untreated at the end of the 6-month follow-up period.

CONCLUSION

Rigorous application of the WHO/ISH clinical guidelines in a group of mild hypertensive patients led to the treatment of patients with slightly higher LV mass and more concentric LV geometry than were found in those not treated. However, a high-risk subgroup, with concentric remodelling, was not identified and left untreated.

Left and right ventricular collagen type I/III ratios and remodeling post-myocardial infarction

BACKGROUND

Types I and III collagen have different physical properties, and an increase of type I/III ratio can have a deleterious impact on myocardial compliance and left and right ventricular diastolic function. Post-myocardial infarction, these changes in collagen types may be relevant to the remodeling process and the development of heart failure.

METHODS AND RESULTS

In the rat coronary ligation heart failure model, we studied the time course of changes in types I and III and total collagen levels over 10 weeks postinfarction. Collagen types were separately quantified in the left (LV) and right ventricles (RV) by computerized morphometry and standard immunohistochemistry techniques, and also by hydroxyproline analysis, and these were correlated with hemodynamic changes. Compared with sham-operated rats, total collagen level increased 2.5- to 2.9-fold and 1.7- to 2.9-fold in the noninfarcted areas (NIAs) of the LV and RV, respectively, over the 10-week period and showed a good relation with changes in hydroxyproline content (r2 = 0.62; P < .0001). In the NIAs of both the LV and RV, type III collagen level showed a transient twofold increase at 2 weeks, which declined to normal at 4 weeks. Type I collagen level increased twofold at 4 weeks in the NIA of the LV and remained elevated at 10 weeks. In the RV, type I collagen level increased 2.7-fold to a peak at 4 weeks and declined gradually to 1.7 times baseline at 10 weeks. The patterns of change in type I collagen level in the RV correlated with the changes in LV end-diastolic pressure (r = 0.73; P < .0001) and RV weight to body weight ratio (r = 0.73; P < .0001).

CONCLUSION

There is a relative greater increase of type I collagen level in the NIA and RV postinfarction, and this may lead to left and right ventricular dysfunction. Separate mechanisms might be involved in the induction of the different types of collagen deposition, with type I collagen levels apparently closely correlating with hemodynamic stress.

ST-segment elevation on Q leads at rest and during exercise: relation with myocardial viability and left ventricular remodeling within the first 6 months after infarction

BACKGROUND

Resting ST-segment elevation on Q leads after an acute myocardial infarction has been related to a greater infarct size. Otherwise, the relation between exercise-induced ST-segment elevation and myocardial viability is controversial. We investigated the relation between ST-segment elevation on Q leads at rest and during exercise and regional dysfunction and its evolution, contractile reserve, left ventricular dilation, and coronary patency.

METHODS AND RESULTS

Exercise testing and cardiac catheterization were performed at the first week after infarction in 51 patients. The study group was divided according to the existence (in 2 or more Q leads; n = 36) or not (n = 15) of resting ST-segment elevation and according to the existence (n = 28) or not (n = 23) of exercise-induced ST-segment elevation. Left ventricular end-diastolic and end-systolic volumes (mL/m2), regional wall motion (SD/chord), contractile reserve (wall motion percentage improvement with low-dose dobutamine), and coronary patency in the culprit artery were analyzed. Cardiac catheterization was repeated at the sixth month in 35 patients; systolic recovery (wall motion percentage improvement), left ventricular volumes, and coronary patency were again evaluated. Patients with resting ST-segment elevation showed poorer wall motion (2.1 +/- 0.8 SD/chord vs 1.2 +/- 1 SD/chord, P =.002), lesser contractile reserve (17% [0% to 39%] vs 41% [4% to 92%], P =.04), greater end-systolic volume (32 +/- 15 mL/m2 vs 23 +/- 11 mL/m2, P =.04), and higher percentage of occlusion (36% vs 7%, P =.04) than did patients without ST-segment elevation. Likewise, patients with exercise-induced ST-segment elevation showed lesser contractile reserve (8% [0% to 40%] vs 35% [12% to 86%], P =.03) than did patients without exercise-induced ST-segment elevation. The only independent predictors of contractile reserve were wall motion <2 SD/chord (odds ratio [OR] 7.1, confidence interval [CI] 6.3 to 7.9, P =.01) and the absence of exercise-induced ST-segment elevation (OR 5.7, CI 4.9 to 6.5, P =. 02). There were no significant differences between patients with and those without ST-segment elevation (at rest or during exercise) in systolic recovery or left ventricular volumes at the sixth month.

CONCLUSIONS

ST-segment elevation on Q leads at rest is related to a poorer systolic function (more severe regional dysfunction, greater end-systolic volume, and less response to dobutamine). ST-segment elevation during exercise is independently related to a lesser contractile reserve. ST-segment elevation (at rest or during exercise) is not related to the evolution of volumes or regional dysfunction during the first 6 months after infarction.

Brain natriuretic peptide as a marker of cardiac involvement in hypertension

Hypertensive patients with heart abnormalities have increased risk of cardiovascular events. Brain natriuretic peptide is a natriuretic peptide mainly of ventricular origin produced in response to pressure and stretch. We hypothesise that brain natriuretic peptide could be a useful marker of cardiac remodelling in hypertensive patients. We studied 36 consecutive community mild-to-moderate hypertensive patients and 11 well-matched normotensive controls with respect to clinical characteristics, brain natriuretic peptide, creatinine and echocardiography parameters (M-mode, 2-D arid transmitral pulsed Doppler). Brain natriuretic peptide levels were significantly higher in hypertensive patients than in controls [36.54 (IQR: 38.61) vs. 10.30 (IQR: 13.20) pg ml(-1), p<0.0001] and it was correlated with left ventricular mass index. Hypertensive patients with impairment of diastolic filling had significantly higher brain natriuretic peptide concentrations than patients with no abnormalities on echocardiography [61.16 (45.38) vs. 31.27 (18.10) pg ml(-1), p=0.001]. Multivariate analysis showed that only diastolic dysfunction and left ventricular mass index were significantly and independently related with brain natriuretic peptide concentrations in this population. In conclusion, impairment of diastolic function and left ventricular mass index are related to brain natriuretic peptide levels, thus giving the insight that this peptide can be a marker of ventricular remodelling in hypertensive patients.

[Serial change of TL/BMIPP dual SPECT myocardial scintigram in patients with acute myocardial infarction; meaning of chronic mismatch phenomenon]

This study was aimed to elucidate the serial changes and clinical significance of accumulation mismatch with TL and BMIPP dual SPECT myocardial scintigraphy during 6 months in patients with acute myocardial infarction (AMI). The dual SPECT scintigraphy was performed at one, three and six months after onset of AMI in 46 patients who underwent reperfusion therapy. Long axis fractional shortening in infarct-related area and left ventricular end-diastolic volume index (LVEDVI) were measured by left ventriculography performed immediately after reperfusion and at one, six months after onset of AMI. The patients were divided into two groups: those with mismatch (Group (+)) and those without (Group (-)) at one month after reperfusion. Group (+) was subdivided into three groups according to duration of persistence of mismatch; one month persistence (1 M), three months (3 M) and six months (6 M). Improvement of wall motion abnormality (WMA) in infarct-related area was seen at one month after reperfusion in group 1 M and group 3 M, while group 6 M showed no apparent change in WMA throughout the study period. LVEDI did not change at six months after reperfusion in group 1 M and 3 M, while significant increase was seen in group 6 M. It is concluded that the case with disappearance of mismatch between TL and BMIPP until three months after reperfusion indicates myocardial stunning while in the case with long-standing mismatch left ventricular remodeling is suggested.

Ionic basis of ventricular arrhythmias in remodeled rat heart during long-term myocardial infarction

OBJECTIVE

Deleterious electrical abnormalities evolve during myocardial infarction. The goal of this study was to analyse current changes during the late decompensated phase of heart disease induced by coronary ligation and to compare them in various heart regions.

METHODS

Young rats were submitted to left coronary ligature. After 4-6 months, cells were enzymatically dissociated and isolated from the upper part basal region of the left ventricle, as well as from the septum, apex and the right ventricle before being studied under whole-cell patch-clamp.

RESULTS

Basal L-type Ca2+ current, ICaL elicited at +10 mV did not exhibit regional dependence neither in control nor after post-myocardial infarction (PMI). ICaL showed both a significantly reduced peak amplitude (17.1 +/- 2.8 pA/pF versus 9.9 +/- 1.4 pA/pF in seven control and seven PMI hearts, n = 32 and 40, respectively) and a slower inactivation, such that the amount of inward charges during a 200 ms-depolarizing pulse was nearly unchanged. beta-Adrenergic stimulation was less effective in increasing ICaL in PMI cells but it slowed inactivation further. Significant differences in the K+ currents were observed. A regional distribution was seen for Ito only, with the largest amplitude in the right ventricle (in pA/pF: 23.1 +/- 2.4, 18.2 +/- 3.9, 14.8 +/- 2.4, 8.3 +/- 1.7 in the right ventricle, apex, septum and left ventricle, respectively n = 8, 7, 8 and 9). This was also true in failing heart cells despite Ito being halved in each of the four regions (in pA/pF: 12.2 +/- 2.5, 11.2 +/- 1.9, 5.1 +/- 1.0 and 4.8 +/- 1.0, respectively n = 12, 12, 11 and 13). IK1 was also significantly reduced by 20% in the PMI cells. Two-way analyses of variance demonstrated the absence of interaction between the topographical origin of the cells and the physiological state of the rats. The alpha 1-adrenergic agonist, methoxamine significantly reduced Ito and IK1 to the same extent in both sham and PMI cells, by about 35% and 20% respectively.

CONCLUSIONS

Long-term left coronary occlusion induces significant alterations in both Ca2+ and K+ currents that occur with similar amplitude in both ventricles. They include a marked reduction in Ito amplitude as well as a slowing of ICaL inactivation. Both factors could contribute to the disturbances in cellular electrical behaviour and the occurrence of arrhythmias in the post-myocardial infarcted heart.

Changes of the insulin-like growth factor I system during acute myocardial infarction: implications on left ventricular remodeling

In vitro and in vivo experiments have shown important biological actions of insulin-like growth factor I (IGF-I) in heart. The aims of this study were to determine the changes in circulating IGF-I and IGF-binding proteins (IGFBPs) during acute myocardial infarction (AMI) and to explore the relationship between IGF-I levels and myocardial remodeling and function after AMI. Thirty-four patients with acute Q-wave AMI and 17 matched controls were investigated in this study. Compared to normal subjects, free IGF-I and IGFBP-3 were significantly elevated, and IGFBP-1 was decreased upon AMI. Myocardial remodeling occurred after AMI in these patients. The day 2, 3, and 7 total IGF-I levels were inversely related to day 7 left ventricular (LV) end-diastolic, end-systolic diameters (r = -0.395 to -0.516) and LV mass (r = -0.487 to -0.661). Moreover, total IGF-I levels were positively related to LV ejection fraction (r = 0.402-0.453). Compared to the healthy survivors, those patients with poor outcomes had lower total IGF-I levels immediately after AMI. Most healthy survivors had total IGF-I levels greater than 137 ng/mL, but all patients with poor outcome had total IGF-I levels less than 137 ng/mL. Thus, AMI is associated with significant alterations in the IGF-I system. A higher total IGF-I level immediately after the onset of AMI is associated with better myocardial remodeling and ventricular function.

Novel approaches to retard ventricular remodeling in heart failure

While the etiologies of congestive heart failure (CHF) are diverse, a common event in the progression of this disease process is LV remodeling, increased wall stress, and subsequent pump dysfunction. Therapeutic approaches for CHF have been focused upon reducing LV afterload through vasodilator therapy, or by blocking/interrupting the effects of neurohormonal stimuli. However, another therapeutic approach would be to directly intervene in the LV remodeling process with CHF. An important determinant in the maintenance of myocyte shape, alignment and transduction of myocyte shortening into an overall ejection is the structural support provided by the fibrillar collagen matrix. As in most tissue remodeling processes, LV myocardial remodeling with CHF is accompanied by changes in the structure and composition of the collagen matrix. Matrix metalloproteinases (MMPs) are an endogenous family of zinc-dependent enzymes which have been identified to be responsible for matrix remodeling and alterations in MMP expression and activity have been identified in clinical and animal models of CHF. Moreover, alterations in the tissue inhibitors of MMPs (TIMPs) have also been identified to occur in the end-stage CHF myocardium. Thus, it is very likely that increased MMP activity and reduced inhibitory control of the TIMPs contribute to the LV remodeling process with CHF. A number of bioactive peptides and cytokines influence MMP and TIMP expression and activity. In addition, pharmacologically active MMP inhibitors have been synthesized and are currently under study. Accordingly, the control of MMP and TIMP expression and activity within the failing myocardium represents a new and potentially significant therapeutic target for CHF.

Myocardial oxygenation during high work states in hearts with postinfarction remodeling

BACKGROUND

Postinfarction left ventricular remodeling (LVR) is associated with reductions in myocardial high-energy phosphate (HEP) levels, which are more severe in animals that develop overt congestive heart failure (CHF). During high work states, further HEP loss occurs, which suggests demand-induced ischemia. This study tested the hypothesis that inadequate myocyte oxygen availability is the basis for these HEP abnormalities.

METHODS AND RESULTS

Myocardial infarction was produced by left circumflex coronary artery ligation in swine. Studies were performed in 20 normal animals, 14 animals with compensated LVR, and 9 animals with CHF. Phosphocreatine (PCr)/ATP was determined with 31P NMR and deoxymyoglobin (Mb-delta) with 1H NMR in myocardium remote from the infarct. Basal PCr/ATP tended to be decreased in postinfarct hearts, and this was significant in animals with CHF. Infusion of dobutamine (20 microg x kg-1 x min-1 IV) caused doubling of the rate-pressure product in both normal and LVR hearts and resulted in comparable significant decreases of PCr/ATP in both groups. This decrease in PCr/ATP was not associated with detectable Mb-delta. In CHF hearts, rate-pressure product increased only 40% in response to dobutamine; this attenuated response also was not associated with detectable Mb-delta.

CONCLUSIONS

Thus, the decrease of PCr/ATP during dobutamine infusion is not the result of insufficient myocardial oxygen availability. Furthermore, in CHF hearts, the low basal PCr/ATP and the attenuated response to dobutamine occurred in the absence of myocardial hypoxia, indicating that the HEP and contractile abnormalities were not the result of insufficient oxygen availability.

Remodeling of chick embryonic ventricular myoarchitecture under experimentally changed loading conditions

Adult myocardium adapts to changing functional demands by hyper- or hypotrophy while the developing heart reacts by hyper- or hypoplasia. How embryonic myocardial architecture adjusts to experimentally altered loading is not known. We subjected the chick embryonic hearts to mechanically altered loading to study its influence upon ventricular myoarchitecture. Chick embryonic hearts were subjected to conotruncal banding (increased afterload model), or left atrial ligation or clipping, creating a combined model of increased preload in right ventricle and decreased preload in left ventricle. Modifications of myocardial architecture were studied by scanning electron microscopy and histology with morphometry. In the conotruncal banded group, there was a mild to moderate ventricular dilatation, thickening of the compact myocardium and trabeculae, and spiraling of trabecular course in the left ventricle. Right atrioventricular valve morphology was altered from normal muscular flap towards a bicuspid structure. Left atrial ligation or clipping resulted in hypoplasia of the left heart structures with compensatory overdevelopment on the right side. Hypoplastic left ventricle had decreased myocardial volume and showed accelerated trabecular compaction. Increased volume load in the right ventricle was compensated primarily by chamber dilatation with altered trabecular pattern, and by trabecular proliferation and thickening of the compact myocardium at the later stages. A ventricular septal defect was noted in all conotruncal banded, and 25% of left atrial ligated hearts. Increasing pressure load is a main stimulus for embryonic myocardial growth, while increased volume load is compensated primarily by dilatation. Adequate loading is important for normal cardiac morphogenesis and the development of typical myocardial patterns.

Decreased left ventricular filling pressure 8 months after corrective surgery in a 55-year-old man with tetralogy of Fallot: adaptation for increased preload

A 55-year-old man with tetralogy of Fallot underwent corrective surgery. Left ventricular filling pressure increased markedly with increased left ventricular volume one month after surgery, then decreased over the next 7 months, presumably due to increased left ventricular compliance.

Sustained elevation of plasma brain natriuretic peptide levels associated with progressive ventricular remodelling after acute myocardial infarction

Previous studies have shown that levels of plasma brain natriuretic peptide (BNP) increase in an early phase of acute myocardial infarction. However, the relations between plasma BNP levels and left ventricular remodelling, which occurs long after acute myocardial infarction, are not fully understood. Venous plasma BNP levels were measured 2, 7, 14, 30, 90 and 180 days after the onset of acute myocardial infarction in 21 patients. Left ventricular end-diastolic volume index (EDVI, ml/m2) in acute (5 days) and chronic (6 months) phases were assessed by electron-beam computed tomography using Simpson's method. The remodelling group (n=9) was defined by an increase in EDVI >/=5 ml/m2 relative to the baseline value. Plasma BNP levels on days 2, 7, 14, 30 and 90 were significantly higher in the remodelling group than in the non-remodelling group (n=12, P<0.05). Sustained elevation of plasma BNP levels was noted from day 2 (61+/-12 pmol/l) to day 90 (55+/-12 pmol/l) and significantly decreased on day 180 (24+/-3 pmol/l) in the remodelling group. In contrast, plasma BNP levels significantly decreased from day 2 (25+/-4 pmol/l) to day 90 (9+/-1 pmol/l) and reached a steady level thereafter in the non-remodelling group. Plasma BNP levels on day 7 correlated positively with an increase in EDVI (r=0.70, P<0.001) from the acute to chronic phase. More importantly, the sustained elevation of plasma BNP (percentage decrease smaller than 25%) from day 30 to day 90 identified patients in the remodelling group with a sensitivity of 100% and a specificity of 83%. In conclusion, not only the high levels of plasma BNP in an acute phase, but also the sustained elevation of plasma BNP in a chronic phase, may be associated with progressive ventricular remodelling occurring long after acute myocardial infarction.

Increased number of cardiomyocytes in cross-sections from tachycardia-induced cardiomyopathic hearts

Based on positive identification of DNA replication and mitotic division in cardiomyocytes isolated from failing hearts, it has been proposed that adult ventricular cardiomyocytes can gain the capacity to proliferate with progression of heart failure. However, due to the lack of a reliable method to distinctly image individual cardiac cells within the myocardial syntitium, such a concept still remains largely controversial. In the present study, we used laser confocal microscopy, to image cross-sections of intact myocardium stained with fluorescein-conjugated wheat germ agglutinin and propidium iodide. This approach allowed to clearly separate the profile of individual myocytes within cardiac tissue sections. We found that in the left ventricles of dogs, subjected to tachycardia-induced cardiomyopathy, the number of cells was significantly increased in both longitudinal and transversal sections. Treatment with the angiotensin-converting enzyme inhibitor, enalapril, reversed these changes to values similar to those found in controls. Therefore, this study provides evidence, at the in situ level, for cellular hyperplasia in heart failure. This supports the more general notion that adult cardiomyocytes may not be terminally differentiated, and that an increase in cell number could contribute to the increase in left ventricular mass observed with progression of disease.

[Observation on left ventricular remodeling in acute myocardial infarction]

OBJECTIVE

After an acute myocardial infarction (AMI), there will be regional dilation and global remodeling of the infarcted left ventricle. This study was aimed to observe the features of the ventricular remodeling after AMI.

METHODS

Based on the time of onset of the symptoms, 37 patients (pts) with AMI were divided into 4 groups. The time of onset of AMI for group 1 (16 pts), group 2 (7 pts), group 3 (11 pts) and group 4 (3 pts) was < or = 3 hours (hrs), > 3 hrs - < or = 6 hrs, > 6 hrs - < or = 12 hrs and > 12 hrs respectively. The size of the left ventricle in all the patients were analysed with resting myocardial gated SPECT (GSPECT). Tc-99m MIBI was infused at admission and data of GSPECT were collected 2 hours later following the infusion. End-diastolic volume (EDV), end-systolic volume (ESV) and LVEF were shown by the system. Stroke volume (SV) was then calculated.

RESULTS

EDV for group 1 to 4 was (98.5 +/- 31.9) ml, (99.4 +/- 55.6) ml, (128.1 +/- 55.1) ml and (140.0 +/- 25.3) ml, respectively. ESV for group 1 to 4 was (57.0 +/- 30.9) ml, (55.1 +/- 40.3) ml, (77.4 +/- 39.8) ml and (81.3 +/- 26.0) ml, respectively. SV for group 1 to 4 was (57.0 +/- 30.9) ml, (55.1 +/- 40.3) ml, (77.4 +/- 39.8) ml and (81.3 +/- 26.0) ml, respectively. LVEF for group 1 to 4 was (44.6 +/- 13.1) ml, (49.7 +/- 13.1) ml, (42.8 +/- 13.5) ml, and (42.7 +/- 8.6) ml, respectively. In pts with anterior infarction, EDV, ESV and SV after 6 hrs of the onset of AMI were greater than those in pts with in 6 hrs of the onset. It was the same in pts with inferior infarction.

CONCLUSION

It is suggested that the left ventricular size increased in 3 hrs after AMI. Following the initial dilation of left ventricle, EDV, ESV and SV did not change significantly with in 6 hrs, but then increased gradually after 6 hrs from the onset of the symptoms. The early and significant dilation of left ventricle after AMI may be one of the risk factors of severe cardiac events.

The extent of regional wall motion abnormalities identifies patients at risk of extensive left ventricular remodeling: implications for the design of post myocardial infarction trials

BACKGROUND

The FAMIS (Fosinopril in Acute Myocardial Infarction Study) was a multicenter, placebo-controlled, double-blind trial designed to evaluate the safety and the efficacy of fosinopril in reducing left ventricular enlargement after acute anterior myocardial infarction. We evaluated the echocardiographic examinations performed during the trial in order to assess the trend of the remodeling process over time and to evaluate the role of infarct size in identifying patients at risk of progressive left ventricular dilation.

METHODS

A complete echocardiographic examination was performed on admission, before discharge and three months later. Patients undergoing coronary bypass surgery or PTCA had a further examination prior to the procedure. The echocardiograms were analyzed at a central laboratory, and the end-diastolic and end-systolic left ventricular volumes were computed by using a modified Simpson's rule technique. Regional wall motion was evaluated using the centerline method, analyzing the left ventricular boundary along 100 chords perpendicular to the centerline constructed midway between the end-diastolic and the end-systolic contours. A quantitative infarct-size index was then computed according to the number of chords with a fractional shortening equal to or less than 5%.

RESULTS

Left ventricular end-diastolic and end-systolic volume index significantly increased over time (p < 0.0001); as a result, the stroke volume increased (p < 0.0001) but the ejection fraction did not change. Patients were then divided according to the three-month infarct-size index. For both end-diastolic and end-systolic volume, not only did larger infarcts had higher volumes, but there was also a greater increase from baseline to 3 months. Moreover, larger infarcts had a lower ejection fraction, with a further reduction over the three months, while smaller infarcts had higher values and an increase over time. An infarct-size index of 25 or larger allowed prospective identification at the baseline examination of patients at risk of subsequent left ventricular dilation.

CONCLUSIONS

In conclusion, patients at greatest risk of left ventricular dilation, namely those with larger infarct size, constitute a group that is worth considering for any therapeutic effort for reducing the remodeling process. These patients could in fact benefit from therapeutic strategies aimed at the reduction of left ventricular remodeling and should be studied in clinical trials.

[Structural and functional changes in the of heart of high-performance (canoeing) athletes]

We studied two groups of healthy subjects: Group I was integrated by 13 high-performance sportsmen (10 men and 3 women), devoted to the discipline of the rowing. Group II was integrated by 16 sedentary healthy subjects. All of them were studied with a two-dimensional echocardiogram, in order to study the anatomical and functional characteristics of the heart. Both groups had similar characteristics in regard of total body area, heart rate and blood pressure, the only difference was in age. The ventricular mass and the diastolic volume were greater in athletes in spite of the fact that the dimensions and transverse thicknesses were similar, this imply a longitudinal increase of the heart size. It is possible that this form of ventricular remodeling has functional advantages. On the other hand, it was demonstrated the existence of physiological hypertrophy without disorders in diastolic function.

Neointimal hyperplasia and late pathologic remodeling in a porcine coronary stent model

BACKGROUND

Although coronary stenting has been demonstrated to significantly reduce restenosis compared to conventional angioplasty, occurrence of in-stent stenosis still remains one of the major limitations. This study investigates the influence of stent strut diameter on injury, inflammatory response, thrombosis and neointimal hyperplasia in a porcine coronary artery.

METHODS

Coil stents made of either a 0.12 mm, 0.15 mm or 0.18 mm wire were randomly implanted in the right coronary arteries of 30 pigs. Quantitative coronary angiography analysis was performed before, immediately after, and 6 weeks following the stenting procedure. At 6 weeks, histopathology for evaluation of injury, thrombosis and inflammation, as well as morphometry for calculation of the neointimal hyperplasia and internal elastic lamina area were performed.

RESULTS

Quantitative coronary analysis showed similar quantitative data before and after stent placement in the three groups. At 6 weeks, however, a significantly bigger MLD was found in the 0.18 mm group. Morphometric analysis at 6 weeks confirmed these results, showing a significantly bigger lumen area in both the 0.18 mm (1.71 +/- 0.66 mm2) and 0.15 mm (1.36 +/- 0.53 mm2) groups compared to the 0.12 mm group (0.71 +/- 0.38 mm2). The calculated neointimal hyperplasia was similar in the three groups (0.12 mm: 1.93 +/- 0.51 mm2; 0.15 mm: 1.68 +/- 0.63 mm2; and 0.18 mm: 2.16 +/- 1.48 mm2). The internal elastic membrane area, however, was significantly bigger in the 0.18 mm (3.87 +/- 1.39 mm2) compared to the 0.12 group (2.65 +/- 0.53 mm2).

CONCLUSION

These results suggest that pathologic remodeling can also play an important role in late lumen loss after stent implantation.

Heterogeneous fate of perfusion and contraction after anterior wall acute myocardial infarction and effects on left ventricular remodeling

After acute myocardial infarction, patency of infarct vessel and extent of left venticular (LV) dysfunction are major determinants of ventricular remodeling. Spontaneous, delayed reperfusion in the infarct zone occurs in a sizeable number of patients well after the subacute phase. The aim of this study was to determine the relation between the occurrence of this spontaneous, delayed reperfusion and LV remodeling. In 84 patients, resting LV volumes, topography, regional function, and perfusion were quantitatively evaluated by 2-dimensional echocardiography and sestamibi tomography 5 weeks (study 1) and 7 months (study 2) after anterior Q-wave infarction. At study 2, LV end-diastolic volume increased by > 15% in 17 patients (20%, LV remodeling); they had already had at study 1 significantly larger LV volumes, more severe hypoperfusion and wall motion abnormalities, and greater regional dilation than patients with stable LV volumes. Delayed reperfusion occurred in 8 of 17 patients with and in 42 of 67 patients without LV remodeling (47% vs 63%; p=NS). At study 2, LV regional dilation and end-diastolic volumes were stable in patients with, but increased in patients without, spontaneous reperfusion (from 25+/-24% to 29+/-26% at study 2 [p<0.05] and from 65+/-14 to 68+/-18 ml/m2 [p <0.05]). At multivariate analysis, however, regional ventricular dilation at study 1 was the sole predictor of further LV remodeling. Thus, after acute myocardial infarction, spontaneous reperfusion occurring after 5 weeks plays only a minor role in influencing LV remodeling. Benefits from delayed reperfusion seem limited to patients with preserved LV volumes; patients with an enlarged left ventricle 5 weeks after acute infarction are prone to further LV remodeling, irrespective of delayed reperfusion.

Residual strain in ischemic ventricular myocardium

Structural remodeling during acute myocardial infarction affects ventricular wall stress and strain. To see whether acute myocardial infarction alters residual stress and strain in the left ventricle (LV), we measured opening angles in rat hearts after 30 minutes of left coronary artery occlusion. The mean opening angle in 18 ischemic hearts (51 +/- 20 deg) was significantly greater than in five sham-operated controls (29 +/- 11 deg, P < 0.05). To determine whether these alterations in residual strain may be associated with strain softening caused by systolic overstretch of the noncontracting ischemic tissue, we also measured opening angles in isolated hearts that had been passively inflated to high LV pressures (120 mmHg). The mean opening angle of the strain-softened hearts was not significantly different from the sham-operated hearts (34 +/- 27 deg, P = 0.74). Mean collagen area fractions in the myocardium were not significantly different between ischemic hearts (0.027 +/- 0.014) and the nonischemic group (0.022 +/- 0.011). Although there were significant differences in opening angles measured with ischemia, they do not appear to be a result of altered extracellular collagen content or softening associated with overstretch. Thus, there is a significant change in residual strain associated with acute ischemia that may be related to changes in collagen fiber structure, myocyte structure, or metabolic state.

[Is the treatment of left ventricular systolic dysfunction different according to the etiology?]

Cardiac failure is the terminal stage of evolution, the finality of many valvular, vascular, myocardial, general, congenital or acquired conditions. The therapeutic decisions should be based on the search for a curable cause of a predisposing factor and the evaluation of the severity of the cardiac failure. At advanced stages of ventricular dysfunction when the myocardial lesions are constituted, when cardiac and vascular remodelling has occurred, the aetiological treatment, which is the constant objective, is unfortunately too late. The treatment is the same, whatever the aetiology, in order to improve functional problems. At early stages, and, if possible, preventively, surgery, revascularisation techniques, the correction of an arrhythmia, the suppression of a cardiotoxic factor, are essential. The different therapeutic classes used could have different efficacies depending on the aetiology, but, finally, this point is negligible: the medications are based on the results of large scale, controlled, therapeutic trials.

Immediate effects of partial left ventriculectomy on left ventricular function

BACKGROUND

Attempts to prolong life or to improve the quality of life by partial left ventriculectomy in patients suffering from dilated cardiomyopathy have yielded strikingly variable results in leading surgical centers.

HYPOTHESIS

The outcome of patients after partial left ventriculectomy depends on intraoperative myocardial protection together with appropriate long-term pharmacotherapy. We further assume that partial removal of the fibrotic ventricular wall may lead to a particularly inhomogeneous pattern of wall stress, giving rise to the potential of a paradoxical increase in wall stress and the creation of arrhythmogenic foci.

METHODS

During surgery in 24 patients, local mesh tension was measured using needle-force probes in up to five sites within the left ventricular wall before and after resection of the interpapillary mural segment. The data were used to calculate regional peak developed force and to identify any differences in the timing of local mechanical activity between the measured regions.

RESULTS

Mean decrease in regional wall stress was 42% (76 sites of measurement). However, we discovered a paradoxical increase of 42% in 18 sites of measurement. The time delay in the onset of force development between the measured regions prior to surgery was 0 msec in 10 patients, up to 30 msec in 7 patients, and beyond 80 msec in 7 patients. After resection, the time delay increased considerably in incidence and duration.

CONCLUSION

Ventriculectomy is an effective means of reducing wall stress. The unexpectedly high incidence of inhomogeneities in wall stress after asymmetrical surgical ventricular remodeling, currently typical for the classical Batista procedure, together with the asynchronous regional ventricular function that we found to increase after partial left ventriculectomy, needs further elucidation by electrophysiological investigations.

[Prevention of heart failure]

Heart failure is a major problem of public health, associated with poor outcome in the advanced stage, thus justifying its prevention. Primary prevention is based on the prevention and treatment of its principal etiologic factors, hypertension and coronary artery disease. Broad use of echocardiography or dosage of neurohormonal markers improve detection of asymptomatic left ventricular dysfunction. In ischemic heart disease, coronary recanalisation prevents or limits left ventricular remodeling and dysfunction, even if the "open artery" theory has not been entirely proved. Understanding the deleterous role of neurohormonal stimulation results in a large use of ACE-inhibitors, which beneficial effect has been demonstrated also in case of asymptomatic left ventricular dysfunction. Betablockers, already largely used after myocardial infarction, seem to have also a beneficial effect in heart failure: the same is probably also true for angiotensin II-antagonists. Double blocking of both the sympathetic nervous system and the angiotensin-aldosterone system seems to be recommended. More precisely understanding the pathways signaling the processes of ventricular remodeling and dysfunction points to new potential targets for a preventive treatment: endothelin receptors, apoptosis, oxidative stress, cytokines or even angiogenesis.

[Diastolic cardiac failure: therapeutic modalities]

The management of cardiac failure due to diastolic dysfunction is not well codified and is often empirical. It has three objectives: improving the physiopathological components of ventricular filling, treating the associated aggravating pathological conditions, and treating the basic cause of the dysfunction. Symptomatic treatment aims to reduce venous congestion (by diuretics or nitrate derivatives), to prolong the diastolic period by slowing the heart rate (by betablockers, bradycardising calcium antagonists or digitalis in cases of irreducible atrial fibrillation), to improve passive ventricular distensibility by an effect on remodelling (by angiotensin converting enzyme inhibitors or anti-aldosterone diuretics). The treatment of associated pathological conditions is particularly important. It is essential to maintain or reestablish an effective atrial systole by cardioversion and anti-arrhythmic drugs in atrial fibrillation, by dual chamber pacing in cases of atrioventricular asynchrony due to atrioventricular block. Treatment of the underlying cause aims to induce regression of ventricular hypertrophy of hypertensive origin by using antihypertensive drugs with this property. In coronary artery disease, the choice is determined by the clinical context because nearly all anti-anginal or interventional treatments may improve ischaemic diastolic dysfunction. The same applies in hypertrophic cardiomyopathy because most types of treatment (betablockers, verapamil, cardiac pacing, surgery) may improve diastolic function. Finally, in valvular aortic stenosis, aortic valve replacement restores normal diastolic function.

Restoring the remodeled enlarged left ventricle: experimental benefits of in vivo porcine cardioreduction in the beating open heart

Conceptual models have been used to assess the efficacy of cardioreduction (i.e., Batista procedure) because in vivo models were not available. This study reproduces an experimental angiographic model of heart failure by placing a large pericardial patch to sphericalize the left ventricle. Patch removal restored an elliptical normal cardiac shape. Cardioreduction was evaluated in 20 mini-pigs on cardiopulmonary bypass. Myocardial protection with a beating open method was used and cardioplegia was not used. Studies were made after an LV incision (i.e., circumflex marginal artery occlusion with the Batista incision). A large pericardial patch sphericalized the left ventricle, and LV closure by patch removal restored normal cardiac shape (ellipse). Ventricular function was evaluated by inscribing Starling curves to fill the heart systolic elastance (Ees, conductance catheter), and surface echocardiogram for fiber shortening. After defining LV function in normal hearts on bypass only, an LV incision to divide the median ramus circumflex artery was made. This ventriculotomy reduced stoke work (SW) 37% +/- 4%, but did not change elastance (Ees) or SW/end-diastolic volume (EDV) significantly. Using the LV incision function as control, patch placement reduced SW 33% +/- 4%, Ees 40% +/- 3%, and SW/EDV 44% +/- 7% and decreased fiber shortening 43% +/- 5% by echocardiogram. Patch removal restored stroke work, SW/EDV, and Ees, and echocardiograms returned to normal values after LV incision. Ventricular function after patch removal was unchanged when the beating open cardioprotective technique was used. We conclude that sphericalization of left ventricular dimensions by pericardial patch placement causes cardiac failure that is relieved by restoring the ellipsoid shape by patch removal. These findings support the value of restoration of an elliptical shape by surgical cardioreduction, when the beating open ventricle is used for myocardial protection.

Stress-induced injury of pulmonary capillaries

The lung is particularly vulnerable to injury because the blood-gas barrier is so extremely thin. Furthermore, the mechanical stresses in the barrier become very high when capillary pressure is raised, or when the lung is inflated to a high volume. The strength of the blood-gas barrier on the thin side can be attributed to the type IV collagen in the basement membranes. Abnormally high stresses in the walls of the pulmonary capillaries result in ultrastructural changes including disruptions of both the alveolar epithelial and capillary endothelial layers. All Thoroughbred racehorses break their pulmonary capillaries when they gallop. Also, elite human athletes develop changes in the permeability of the blood-gas barrier at high levels of exercise. Pathological conditions resulting in stress failure include: 1) high-altitude pulmonary edema; 2) neurogenic pulmonary edema; 3) severe left ventricular failure; 4) mitral stenosis; and 5) overinflation of the lung. There is a spectrum of low permeability to high permeability edema as the capillary pressure is raised. Remodeling of pulmonary capillaries apparently occurs at high capillary pressures. It is likely that the extracellular matrix of the capillaries is continuously regulated in response to capillary wall stress.

[Alternative surgical options to heart transplantation]

Cardiac transplantation is the treatment of reference for refractory cardiac failure but the limited number of donors, the complications inherent to transplantation and the relative and absolute contra-indications has made it necessary to find alternative surgical solutions. The detection of myocardial viability by Thallium scintigraphy, Dobutamine echocardiography and/or position emission tomography in coronary disease, allows identification of zones which are capable of recovering contractile function after revascularisation. The authors report the results of a series of 91 operated patients with a 10 year follow-up having a 72% 5 year actuarial survival and improved ejection fraction. The other alternative which may improve symptoms and prognosis in patients with severe ischaemic heart disease with left ventricular dysfunction is apical remodelling or Dor's procedure. The results of a haemodynamic study at 1 year of 171 patients clearly show a functional improvement and an increase of the ejection fraction. The advantage of this method is that it can be used in patients with dyskinetic and akinetic plaques resulting from antero-septo-apical infarction. Finally, even if mitral regurgitation is relatively uncommon in chronic ischaemic heart disease, a simple procedure (annuloplasty) is often sufficient to correct the mitral regurgitation and reduce the afterload of a failing ventricle. On the other hand, in dilated cardiomyopathy, two new options have been developed; one, suggested by Steven Bolling, proposes simple mitral annuloplasty whatever the underlying cause (primary or ischaemic cardiomyopathy) with symptomatic improvement and better haemodynamics in terms of increased cardiac output and oxygen consumption on exercise and an actuarial survival much higher than that of cardiac transplantation at one and at two years. The most recent innovation is the Batista procedure which is a method of ventricular reduction associated with correction of mitral regurgitation. The authors have assessed 20 patients for this operation at the Foch Hospital by Dobutamine echocardiography and 5 patients underwent the procedure. All 5 patients reported symptomatic improvement but some had an unchanged haemodynamic status. Others improved at rest and some improved on exercise. The Cleveland Clinic series reported results in 57 cases. Whichever alternative method tested, there is a significant functional improvement but the cardiac output does not always increase. There are no comparative prospective randomised studies and strict selection of patients is required, a problem not yet resolved for all indications. The advantages of these procedures are certain as there is no waiting list, the functional results in good indications have been demonstrated and, if necessary, secondary orthotopic cardiac transplantation is always possible.

Medical therapy of chronic heart failure. Role of ACE inhibitors and beta-blockers

Heart failure has long been considered to have a progressive downhill course leading inexorably to an early demise. This course often occurs silently, in the absence of any obvious cardiac insults. The reason for this is a combination of cell loss, myocyte dysfunction, impaired energetics, and pathologic remodeling of the chamber. Improved clinical outcome should result from strategies that reduce the biologic signals responsible for myocyte growth, dysfunction, and loss and chamber remodeling. Clinicians should no longer attempt to treat chronic heart failure with pharmacologic growth and remodeling process. In time, it may be possible for the clinician to view the treatment of heart failure largely as a matter of improving the biologic function of the myocardium.

Nonsurgical infarctectomy in acute experimental myocardial infarction

This study examines whether a catheter mounted left intraventricular balloon may prevent left ventricular (LV) dysfunction following acute experimental myocardial infarction. In 10 anesthetized pigs, multiple coronary arterial ligations were applied around the apex of the heart. LV end-diastolic pressure (LVEDP), aortic flow (AF), and LV long and short axis fractional shortening (FS) were measured before and at 15 min intervals after ligations. At the 60th min after ligation, the LV long axis FS and AF decreased by 7.2 +/- 2.6% (p < 0.05) and 13.25 +/- 2.68% (p < 0.01), respectively, and the LVEDP increased by 4.3 +/- 1.1 mm Hg (p < 0.01) while no change was noted in the LV short axis FS. An intraventricular catheter mounted nonpulsating balloon was positioned over the endocardium of the infarcted area at the LV apex. Inflation of the nonpulsating balloon to an optimal volume, which was found to be equal to 8-10% of the LV end-diastolic volume, resulted in a reduction (by 3.8 +/- 1.2 mm Hg, p < 0.01) of the already increased LVEDP and in an increase (by 6.6 +/- 2.1%, p < 0.05) in the LV short axis FS while no statistically significant change was noted in the AF and LV long axis FS. It is concluded that an intraventricular catheter mounted balloon patch positioned over the endocardium of the infarcted area may ameliorate early LV dysfunction, possibly by interfering with the functional geometry of the LV contraction.