Relation of pathophysiologic mechanisms to outcome in heart failure

Knockout of Toll-Like Receptors 2 and 4 Prevents Renal Ischemia-Reperfusion-Induced Cardiac Hypertrophy in Mice

We investigated whether the pathways linked to Toll-like receptors 2 and 4 (TLRs) are involved in renal ischemia-reperfusion (I/R)-induced cardiac hypertrophy. Wild type (WT) C57BL/6J, TLR2^-/- and TLR4^-/- mice were subjected to left kidney ischemia for 60 min followed by reperfusion for 5, 8, 12 and 15 days. Proton density magnetic resonance showed alterations in the injured kidney from WT mice, together with signs of parenchymal edema and higher levels of vimentin mRNA, accompanied by: (i) small, but significant, increase in serum urea after 24 h, (ii) 100% increase in serum creatinine at 24 h. A serum peak of inflammatory cytokines occurred after 5 days of reperfusion. Heart weight/body weight and heart weight/tibia length ratios increased after 12 and 15 days of reperfusion, respectively. Cardiac hypertrophy markers, B-type natriuretic peptide (BNP) and α-actin, left ventricle mass, cardiac wall thickness and myocyte width increased after 15 days of reperfusion, together with longer QTc and action potential duration. Cardiac TLRs, MyD88, HSP60 and HSP70 mRNA levels also increased. After 15 days of reperfusion, absence of TLRs prevented cardiac hypertrophy, as reflected by similar values of left ventricular cardiac mass and heart weight/body weight ratio compared to the transgenic Sham. Renal tissular injury also ameliorated in both knockout mice, as revealed by the comparison of their vimentin mRNA levels with those found in the WT on the same day after I/R. The I/R TLR2^-/- group had TNF-α, IFN-γ and IL-1β levels similar to the non-I/R group, whereas the TLR4^-/- group conserved the p-NF-κB/NF- κB ratio contrasting with that found in TLR2^-/-. We conclude: (i) TLRs are involved in renal I/R-induced cardiac hypertrophy; (ii) absence of TLRs prevents I/R-induced cardiac hypertrophy, despite renal lesions seeming to evolve towards those of chronic disease; (iii) TLR2 and TLR4 selectively regulate the systemic inflammatory profile and NF- κB activation.

Changes in the myocardial interstitium and contribution to the progression of heart failure

The myocardial interstitium is highly organized and orchestrated, whereby small disruptions in composition, spatial relationships, or content lead to altered myocardial systolic and/or diastolic performance. These changes in extracellular matrix structure and function are important in the progression to heart failure in pressure overload hypertrophy, dilated cardiomyopathy, and ischemic heart disease. The myocardial interstitium is not a passive entity, but rather a complex and dynamic microenvironment that represents an important structural and signaling system within the myocardium.

Myocardial Matrix Remodeling and the Matrix Metalloproteinases: Influence on Cardiac Form and Function

It is now becoming apparent that dynamic changes occur within the interstitium that directly contribute to adverse myocardial remodeling following myocardial infarction (MI), with hypertensive heart disease and with intrinsic myocardial disease such as cardiomyopathy. Furthermore, a family of matrix proteases, the matrix metalloproteinases (MMPs) and the tissue inhibitors of MMPs (TIMPs), has been recognized to play an important role in matrix remodeling in these cardiac disease states. The purpose of this review is fivefold: 1) to examine and redefine the myocardial matrix as a critical and dynamic entity with respect to the remodeling process encountered with MI, hypertension, or cardiomyopathic disease; 2) present the remarkable progress that has been made with respect to MMP/TIMP biology and how it relates to myocardial matrix remodeling; 3) to evaluate critical translational/clinical studies that have provided a cause-effect relationship between alterations in MMP/TIMP regulation and myocardial matrix remodeling; 4) to provide a critical review and analysis of current diagnostic, prognostic, and pharmacological approaches that utilized our basic understanding of MMP/TIMPs in the context of cardiac disease; and 5) most importantly, to dispel the historical belief that the myocardial matrix is a passive structure and supplant this belief that the regulation of matrix protease pathways such as the MMPs and TIMPs will likely yield a new avenue of diagnostic and therapeutic strategies for myocardial remodeling and the progression to heart failure.

Ultrasound imaging versus morphopathology in cardiovascular diseases: the heart failure

This review article summarizes the results of histopathological studies to assess heart failure in humans. Different histopathological features underlying the clinical manifestations of heart failure are reviewed. In addition, the present role of echocardiographic techniques in assessing the failing heart is briefly summarized.

Comparison of levels of matrix metalloproteinase-2 and -3 in patients with ischemic cardiomyopathy versus nonischemic cardiomyopathy

It has been reported that circulating matrix metalloproteinase (MMP) levels are upregulated in patients with chronic heart failure. However, experimental studies indicate that differences in the profiles of MMPs and tissue inhibitors of metalloproteinase (TIMPs) may exist in ischemic compared with nonischemic cardiomyopathy. This study examined whether circulating levels of MMPs and TIMP-1 are related to the pathogenesis of heart failure. Circulating levels of MMP-2, MMP-3, and TIMP-1 were assessed in 52 patients with compensated end-stage chronic heart failure, including 26 patients (mean 64 +/- 7 years; 10 men) with ischemic cardiomyopathy (IC) and 26 (mean age 66 +/- 6 years; 14 men) with idiopathic dilated cardiomyopathy (IDC). Serum MMP-2 (p <0.001) and MMP-3 (p <0.001) levels were higher in patients with IDC than in those with IC. Serum TIMP-1 levels were lower in patients with IDC (p = 0.011) than in those with IC. This study shows that in patients with compensated end-stage chronic heart failure, circulating levels of MMP-2, MMP-3, and TIMP-1 are associated with the pathogenesis of heart failure.

A systematic study of a myocardial lesion: Colliquative myocytolysis

BACKGROUND

The term "myocytolysis" was first used to define the repair process of contraction band necrosis associated with an acute myocardial infarction. On the other hand, in the latter condition a "myofibrillolysis," presenting edematous myocardial cells not involved by infarct necrosis, and without evidence of repair process was reported. The objective of this study is to establish the frequency, extent and meaning of this myocardial lesion.

MATERIALS AND METHODS

In 12 groups of patients for a total of 432 cases with and without coronary heart disease, "colliquative myocytolysis"--i.e., progressive vacuolization by loss of myofibrils until their total or subtotal disappearance associated with intramyocellular edema in absence of any cellular reaction--was graded in 16 histological slides of the different cardiac regions in each pathological case.

RESULTS

Colliquative myocytolysis (CM) was present in more than 90% with a maximal extent in cases of irreversible congestive heart failure followed by transplanted heart cases (67%) with a survival greater than 1 week. In all other groups, the lesion was absent or minimal.

CONCLUSIONS

No correlation was found between CM and contraction band necrosis, gender, age, heart weight, myocardial fibrosis, coronary artery stenosis, clinical data. Colliquative myocytolysis is a specific histological marker of congestive heart failure, without relation to coronary blood flow, heart weight and myocardial fibrosis. Vacuolization of myocardial cells may be due to other causes (e.g., storage disease, etc.) or may be an artifact. There is no support for the belief that coronary ischemia or myocardial hypoxia is its causes.

Circulating matrix metalloproteinase-2 is elevated in patients with congestive heart failure

BACKGROUND AND AIMS

It has been reported that matrix metalloproteinase (MMP) protein concentration and activity are upregulated in the failing human heart. However, there are few reports describing the role of elevated level of circulating MMPs in congestive heart failure (CHF) patients. This study examined whether circulating matrix metalloproteinases (MMPs) are also related to the pathogenesis of CHF.

METHODS

We measured circulating levels of matrix metalloproteinase-2 (MMP-2) in 52 patients with CHF (left ventricular ejection fraction (LVEF) <50%). The patients were also subdivided into two groups according to NYHA functional class; mild CHF (class II, n=43) and severe CHF (class III, n=9).

RESULTS

The serum level of MMP-2 and MMP-2/TIMP-2 ratio were significantly higher in CHF than in controls (P<0.01). Among patient groups, serum levels of MMP-2 were significantly higher in patients with severe CHF than in patients with mild CHF (P<0.01). Plasma levels of BNP had a significant positive correlation with circulating levels of MMP-2 (r=0.78; P<0.01) and MMP-2/TIMP-2 ratio (r=0.60; P<0.01).

CONCLUSIONS

Our data showed that the circulating MMP-2 concentration was increased in CHF patients and that the levels were related to the plasma levels of BNP in CHF, suggesting that the elevated levels are related to developing heart failure syndrome.

New therapies for the management of acute heart failure

The standard treatment for acute heart failure (synonymous with pulmonary edema) is an upright posture, oxygen, morphine (often accompanied by an antiemetic), and intravenous diuretics. This treatment has remained unchanged for many years, and the precise mechanism by which each of these methods alleviates symptoms in patients is unclear. Nitrates, oral or intravenous, are also used with benefit, and have some hemodynamic advantages over intravenous diuretics. Recently, three new forms of treatment have been investigated. The use of milrinone, a phosphodiesterase inhibitor, for exacerbation of heart failure in patients with a background of chronic heart failure was not advantageous. The trials of levosimendan, a calcium sensitizer, in patients with pulmonary edema hinted at benefit. Nesiritide, a formulation of brain natriuretic peptide, does bring about hemodynamic improvement in acute heart failure, and is at least as effective as nitroglycerin, easier to prescribe, but prone to cause hypotension. These are small but important advances that increase our knowledge of the pathophysiology of acute heart failure, and also provide an indication of which drugs are preferable for the treatment of this distressing condition.

Metabolic modulation and optimization of energy consumption in heart failure

Chronic heart failure (CHF) is a common and disabling syndrome with a poor prognosis. It is a major and increasing public health problem. Angiotensin-converting enzyme inhibitors, diuretics, and digitalis are the standards treatments for CHF. Other drugs, such as beta-blockers, spironolactone, calcium antagonists, vasodilators, and antiarrhythmic agents are used to counteract the progression of the syndrome or to improve the hemodynamic profile. Despite optimum treatment with neurohumoral antagonists, prognosis of CHF remains poor; the patients complain of persistent reductions in their exercise capacity and quality of life. Fatigue and shortness of breath, two common and disabling symptoms in patient with CHF, are relatively independent from hemodynamic and neuroendocrine changes, although they seem to be related to the impairment of peripheral muscle metabolism and energetic phosphate production. Therefore, CHF is a complex metabolic syndrome in which the metabolism of cardiac and peripheral muscles is impaired and novel therapeutic strategies have been aimed at positive modulation with compounds such as carnitine, trimetazidine, and ranolazine.

Predictors of short-term outcome in Chinese patients with ambulatory heart failure for heart transplantation with ejection fraction <25%

Heart transplantation (HT) provides longer survival than that of the natural history in patients with dilated cardiomyopathy (DCM). However, the optimal timing for cardiac transplantation and predictors of mortality in patients with end-stage cardiomyopathy (ESCM) has been poorly defined. The primary purpose of this study focused on the natural history of ambulatory patients with ESCM for HT assessment. Secondly, we tried to determine prognostic factors of individuals with the poorest short-term outcome and the optimal timing for HT in patients with ESCM. Finally, clinical treatment with angiotensin converting-enzyme inhibitors (ACEIs), carvedilol and amiodarone in the prevention of mortality caused by ESCM, were retrospectively evaluated. The short-term outcomes of 119 referral patients with ESCM for four years were observed. The patients had New York Heart Association class III to IV dyspnea at initial assessment for HT. Left ventricular ejection fraction (LVEF) was 17 +/- 6% and cardiac index (CI) was 2.0 +/- 0.6l/min/m2. After optimization of medical treatment, the patients were divided into two major groups according to CI equal to or less than 2.0l/min/m2 and more than 2.0l/min/m2. HTs were accepted in 88 patients and the patients were divided into two groups: medical treatment (group 1, 56 patients) or HT (group 3, 32 patients); HT was not accepted in the other 31 patients (group 2). We studied the probability of the survival curve and prognostic variables of the groups with medical treatment in the follow-up of 12 +/- 9 months. During follow-up, 49 patients were alive without HT. The remaining 38 patients died; 27 patients were in group 1 and 11 patients were in group 2. Eight deaths in group 2 were sudden. The actuarial survival rate among the non-HT population was 73%, 68%, 63 %, and 56 % at 3, 6, 9 and 12 months, respectively. The actuarial survival rate among group 1 was 70 %, 59 %, 55 %, and 52 % at 3, 6, 9 and 12 months, respectively. The actuarial survival rate among group 2 was 87 %, 85 %, 77 %, and 65 % at 3, 6, 9 and 12 months, respectively. A comparison, excluding patients with HT, was performed with those who had survived < 1 year and > or 1 year after assessment, and those who had died. Two parameters were independent predictors of prognosis on univariate and multivariate analysis: total pulmonary vascular resistance (TPR) > or = 14 Wood units (W) and CI < 1.65 l/min/m2 at 6 and 12 months after assessment. Treatment with amiodarone for ventricular tachycardia (VT) showed no convincing role in the prevention of sudden death in our patients. Also, treatment with ACEIs or carvedilol for heart failure was unconvincing to improve the short-term outcome in this study. Our results suggest in properly selected patients that HT should be considered within six months among patients with severe heart failure. Hemodynamic parameters associated with right cardiac function are important determinants of mortality caused by progressive heart failure. Predictors such as CI and TPR may be considered as important markers of mortality in prediction of short-term outcome in patients with ESCM, as other predictors reported in the literature.

Congestive heart failure and the role of two-dimensional Doppler echocardiography: a primer for cardiac sonographers

Congestive heart failure (CHF) has been an increasing cause of hospitalization, particularly among the elderly population, although the clinical presentation may vary in the individual patient. Two-dimensional and pulsed Doppler echocardiography can be valuable diagnostic methods for the assessment of afflicted patients and can have an impact on patient outcome. The unique advantage of echocardiographic techniques is their ability to characterize left ventricular systolic performance and diastolic filling abnormalities that are commonly present in patients with CHF. This review provides current information the cardiac sonographer can recognize in the assessment of patients with CHF.

Chronic dual inhibition of angiotensin-converting enzyme and neutral endopeptidase during the development of left ventricular dysfunction in dogs

Angiotensin-converting enzyme (ACE) inhibition as well as neutral endopeptidase (NEP) inhibition was demonstrated to influence hemodynamics in various cardiac disease states. However, specific effects of chronic combined ACE and NEP inhibition on left ventricular (LV) and myocyte geometry and function remain unclear. In this study, a dual-acting metalloprotease inhibitor (DMPI), which possesses both ACE and NEP inhibitory activity, was used in a rapid-pacing model of LV dysfunction. LV and myocyte geometry and function were examined in control dogs (n = 6), in dogs with pacing-induced LV dysfunction (216 +/- 2 beats/min, 28 days, n = 7), and in dogs with DMPI treatment during rapid pacing (10 mg/kg p.o., b.i.d., n = 6). With chronic rapid pacing, LV end-diastolic volume increased (84 +/- 4 vs. 49 +/- 3 ml), and LV ejection fraction decreased (38 +/- 3% vs. 68 +/- 3%) compared with control (p < 0.05). DMPI concomitantly administered during long-term rapid pacing did not change LV ejection fraction (35 +/- 3%), but LV end-diastolic volume was reduced (70 +/- 5 vs. 84 +/- 4 ml; p < 0.05) when compared with rapid pacing only. With long-term rapid pacing, myocyte cross-sectional area was decreased (278 +/- 5 vs. 325 +/- 5 microm2), and resting length increased (178 +/- 2 vs. 152 +/- 1 microm) when compared with control (p < 0.05). With DMPI concomitantly administered during rapid pacing, myocyte cross-sectional area (251 +/- 5 microm2) and resting length (159 +/- 4 microm) were reduced when compared with rapid pacing only (p < 0.05). Myocyte velocity of shortening decreased from control values with long-term rapid pacing (39.3 +/- 3.9 vs. 73.2 +/- 5.9 microm/s; p < 0.05) but improved with DMPI treatment during rapid pacing when compared with rapid pacing only (58.9 +/- 6.7 microm/s; p < 0.05). Myocyte velocity of shortening with beta-adrenergic-receptor stimulation (25 nM isoproterenol) was reduced from controls with rapid pacing (125 +/- 12 vs. 214 +/- 30 microm/s; p < 0.05) but was improved with DMPI treatment during rapid pacing when compared with rapid pacing only (178 +/- 12 microm/s; p < 0.05). In a model of rapid pacing-induced LV failure, concomitant DMPI treatment significantly reduced the degree of LV dilation with no apparent effect on LV pump function. At the level of the LV myocyte, long-term DMPI treatment with rapid pacing improved myocyte performance and beta-adrenergic response. Thus the improvement in isolated myocyte contractile function was not translated into improved global LV-pump performance. The mechanisms by which improved myocyte contractility was not translated into a beneficial effect on LV-pump function with DMPI treatment during rapid pacing remain speculative, but likely include significant changes in LV remodeling and loading conditions.

The effects of endothelin-A receptor blockade during the progression of pacing-induced congestive heart failure

OBJECTIVES

We sought to identify the effects of endothelin (ET) subtype-A (ET(A))) receptor blockade during the development of congestive heart failure (CHF) on left ventricle (LV) function and contractility.

BACKGROUND

Congested heart failure causes increased plasma levels of ET and ET(A) receptor activation.

METHODS

Yorkshire pigs were assigned to four groups: 1) CHF: 240 beats/min for 3 weeks; n=7; 2) CHF/ET(A)-High Dose: paced for 2 weeks then ET(A) receptor blockade (BMS 193884, 50 mg/kg, b.i.d.) for the last week of pacing; n=6; 3) CHF/ET(A)-Low Dose: pacing for 2 weeks then ET(A) receptor blockade (BMS 193884, 12.5 mg/kg, b.i.d.) for the last week, n=6; and 4) CONTROL: n=8.

RESULTS

Left ventricle fractional shortening decreased with CHF compared with control (12+/-1 vs. 39+/-1%, p < 0.05) and increased in the CHF/ET(A) High and Low Dose groups (23+/-3 and 25+/-1%, p < 0.05). The LV peak wall stress and wall force increased approximately twofold with CHF and remained increased with ET(A) receptor blockade. With CHF, systemic vascular resistance increased by 120%, was normalized in the CHF/ET(A) High Dose group, and fell by 43% from CHF values in the Low Dose group (p < 0.05). Plasma catecholamines increased fourfold in the CHF group and were reduced by 48% in both CHF/ET(A) blockade groups. The LV myocyte velocity of shortening was reduced with CHF (32+/-3 vs. 54+/-3 microm/s, p < 0.05), was higher in the CHF/ET(A) High Dose group (39+/-1 microm/s, p < 0.05), and was similar to CHF values in the Low Dose group.

CONCLUSIONS

ET(A) receptor activation may contribute to the progression of LV dysfunction with CHF.

Resting and dobutamine stress echocardiographic factors associated with the development of occult dilated cardiomyopathy in healthy Doberman pinscher dogs

In 29 healthy Doberman Pinschers, echocardiographic parameters evaluating systolic and diastolic function were examined prospectively at rest and during dobutamine constant rate infusion (5 micrograms/kg/minute) to determine if any parameters were associated with the development of occult dilated cardiomyopathy (DCM). A resting echocardiogram was repeated 1 year later to determine which dogs had met our criteria for occult DCM. Six dogs developed occult DCM during the follow-up period. Univariate logistic regression analysis showed that at rest, an increased left ventricular internal dimension in systole (LVID-S) (P = .02), preejection period (PEP) (P = .03), ratio of PEP to left ventricular ejection time (P = .02), and isovolumic relaxation time (P = .02) were significantly associated with the development of occult DCM. During dobutamine stress echocardiography (DSE), high LVID-S (P = .02) and systolic wall stress index (P = .04) and reduced fractional shortening (P = .02) and ratio of peak early to late diastolic mitral filling velocity (E/A) (P = .05) were associated with the development of occult DCM. Multiple logistic regression showed that LVID-S (P = .002) and E/A (P = .002) measured during dobutamine infusion also were associated with the development of occult DCM. Reclassification based on the DSE data was not significantly different than reclassification based on the resting echocardiographic data. Resting echocardiography and DSE have the potential to be clinically applicable screening tests for very early systolic and diastolic dysfunction in Doberman Pinschers, heralding the onset of occult DCM as it is currently defined.

Increased matrix metalloproteinase activity and selective upregulation in LV myocardium from patients with end-stage dilated cardiomyopathy

BACKGROUND

One of the hallmarks of dilated cardiomyopathy (DCM) is left ventricular (LV) remodeling. The matrix metalloproteinases (MMPs) are a family of enzymes that contribute to extracellular remodeling in several disease states. Additionally, a family of inhibitors called tissue inhibitors of MMPs (TIMPs) has been shown to exist and to tightly regulate MMP activity. However, the types of MMPs and TIMPs expressed within the normal and DCM LV myocardium and the relation to MMP activity remain unexplored.

METHODS AND RESULTS

Relative LV myocardial MMP activity was determined in the normal (n=8) and idiopathic DCM (n=7) human LV myocardium by substrate zymography. Relative LV myocardial abundance of interstitial collagenase (MMP-1), stromelysin (MMP-3), 72 kD gelatinase (MMP-2), 92 kD gelatinase (MMP-9), TIMP-1, and TIMP-2 were measured with quantitative immunoblotting. LV myocardial MMP zymographic activity increased with DCM compared with normal (984+/-149 versus 413+/-64 pixels, P<.05). With DCM, LV myocardial abundance of MMP-1 decreased to 16+/-6% (P<.05), MMP-3 increased to 563+/-212% (P<.05), MMP-9 increased to 422+/-64% (P<.05), and MMP-2 was unchanged when compared with normal. LV myocardial abundance of TIMP-1 and TIMP-2 increased by >500% with DCM. A high-molecular-weight immunoreactive band for both TIMP-1 and TIMP-2, suggesting a TIMP/MMP complex, was increased >600% with DCM.

CONCLUSIONS

This study demonstrated increased LV myocardial MMP activity and evidence for independent regulatory mechanisms of MMP and TIMP expression with DCM. These findings suggest that selective inhibition of MMP species within the LV myocardium may provide a novel therapeutic target in patients with DCM.

Myocardial extracellular matrix remodeling with the development of pacing induced congestive heart failure contributory mechanisms

The myocardial fibrillar collagens ensure structural integrity of adjoining myocytes, provide the means by which myocyte shortening is translated into overall left ventricular (LV) pump function, and have been postulated to be essential for maintaining alignment of myofibrils within the myocyte through a collagen-integrin-cytoskeletal-myofibril relation. This laboratory has performed a series of studies in order to examine the relationship between changes in myocardial collagen matrix components to LV function and geometry which occurred in a model of congestive heart failure (CHF) induced by chronic rapid pacing. In this model of CHF, indices of LV pump function are reduced and accompanied by significant dilation. LV fibrillar collagen concentration was reduced and salt extractable collagen, which reflects collagen cross-linking, was increased with the development of CHF. LV myocyte adhesion capacity to basement membrane substrates was reduced with pacing CHF. Results from a recently completed series of studies have demonstrated alterations in the expression and activity of the collagenases, or matrix metalloproteinases (MMPs) occur during the progression of CHF. Increased LV myocardial MMP abundance and activity occurred with pacing CHF and were associated with the development of LV dilation, wall thinning, and pump dysfunction. These results suggest that changes within the myocardial extracellular space are a dynamic process and accompany the LV remodeling and dysfunction which occurs with the development of a CHF process. Future studies which define the contributory role of MMP synthesis and activation in the LV remodeling process which occurs in the setting of CHF will likely identify unique therapeutic modalities to slow the progression of this disease process.

Time-dependent changes in matrix metalloproteinase activity and expression during the progression of congestive heart failure: relation to ventricular and myocyte function

The development of congestive heart failure (CHF) is associated with left ventricular (LV) dilation and myocardial remodeling. However, fundamental mechanisms that contribute to this remodeling process with the progression of CHF remain unclear. The matrix metalloproteinases (MMPs) have been demonstrated to play a significant role in tissue remodeling in a number of pathological processes. The present project tested the hypothesis that the LV dilation and remodeling during the progression of CHF is associated with early changes in MMP expression and zymographic activity. LV and myocyte function, collagen content, and MMP expression and zymographic activity were serially measured during the progression of CHF caused by pacing-induced supraventricular tachycardia (SVT) in pigs. After 7 days of SVT, LV end-diastolic dimension and myocyte length both increased by 15% from control values, and LV fractional shortening fell by 20%. At the level of the myocyte, percent shortening fell by 16% after 7 days of SVT, with no change in the steady-state velocity of shortening. Longer durations of SVT caused progressive LV dilation, LV pump failure, and myocyte contractile dysfunction. Specifically, 21 days of SVT resulted in a >50% increase in LV dimension, a 56% fall in LV fractional shortening, and a 33% decline in myocyte velocity of shortening. The decline in LV and myocyte function with 21 days of SVT was accompanied by signs and symptoms of CHF. Thus, SVT causes time-dependent changes in LV geometry and function and the subsequent development of CHF. LV myocardial collagen content and confluence fell by >25% after 7 days of SVT and were accompanied by an 80% increase in LV myocardial MMP zymographic activity against the substrate gelatin. After 14 days of SVT, total LV myocardial collagen content was reduced by 24%, and LV myocardial MMP zymographic activity increased by >100% from control values. Interstitial collagenase (MMP-1), stromelysin (MMP-3), and 72-kD gelatinase (MMP-2) were increased by approximately 2-fold after 7 days of SVT. LV MMP zymographic activity and abundance remained elevated with longer durations of SVT. The results of the present study demonstrated that in this model of CHF, early changes in LV myocardial MMP zymographic activity and protein levels occurred with the initiation and progression of LV dilation and dysfunction. These findings suggest that an early contributory mechanism for the initiation of LV remodeling that occurred in this model of developing CHF is enhanced expression and potentially increased activity of LV myocardial MMPs.

Synergistic exacerbation of diastolic stiffness from short-term tachycardia-induced cardiodepression and angiotensin II

Synergistic interaction between angiotensin II (Ang II) and evolving cardiodepression may play an important role in worsening chamber function, particularly in diastole. To test this hypothesis, Ang II was infused at 10 or 17 ng.kg(-1).min(-1) in 18 conscious dogs 4 days before and during induction of subacute cardiodepression by 48-hour tachypacing. The lower dose yielded negligible systemic pressure changes. Twelve additional animals served as paced-only controls. Pressure-dimension relations were recorded, and serial endocardial biopsies were obtained to assess histological and metalloproteinase (MMP) changes. Forty-eight-hour pacing alone depressed systolic function but had little effect on diastolic stiffness. Ang II alone only modestly raised diastolic stiffness at both doses and enhanced contractility at the higher dose. These changes recovered toward baseline after a 7-day infusion. However, Ang II (at either dose) combined with 48-hour pacing markedly increased ventricular stiffness (110+/-26% over baseline) and end-diastolic pressure (22+/-1.7 mm Hg). In contrast, pacing-induced inotropic and relaxation abnormalities were not exacerbated by Ang II. Zymography revealed MMP activation (72- and 92-kD gelatinases and 52-kDa caseinase) after a 4-day Ang II infusion (at both doses), which persisted during pacing. Tachypacing initiated 24 hours after cessation of a 7-day Ang II infusion also resulted in diastolic stiffening and corresponded with MMP reactivation. Ang II also induced myocyte necrosis, inflammation, and subsequent interstitial fibrosis, but these changes correlated less with chamber mechanics. Thus, Ang II amplifies and accelerates diastolic dysfunction when combined with evolving cardiodepression. This phenomenon may also underlie Ang II influences in late-stage cardiomyopathy, when chamber distensibility declines.

The propionyl-L-carnitine hypothesis: an alternative approach to treating heart failure

Propionyl-L-carnitine (PLC) is a naturally occurring compound that has been considered for the treatment of congestive heart failure (CHF). The rationale for its use in this pathology is related to its effects on cardiac and skeletal muscle. Chronic treatment with PLC improves the contraction of isolated and aerobic perfused rabbit hearts. The compound improves energy metabolism and myocardial contractility in different experimental models of heart failure, such as pressure-overloaded rats, infarct model of heart failure, and rabbit with streptozotocin-induced diabetes. In general, the effect of PLC is apparent in situations of high energy demand such as those induced by increased workload. It therefore seems likely that PLC is able to correct some metabolic steps of the process that leads to heart failure. In addition, PLC may be helpful in heart failure because of its specific action on peripheral skeletal muscle. Administration of PLC in patients with CHF improves skeletal muscle metabolism by increasing pyruvate flux into the Krebs cycle and by decreasing lactate production. These effects occur in the absence of major hemodynamic and neuroendocrinologic changes and may underlie the ability of PLC to increase exercise performance in patients with heart failure. In a randomized study of 50 patients with mild CHF, PLC increased the maximal exercise time, reduced lactate production, and improved left ventricular ejection fraction. There have been two large-scale trials on the effects of PLC on both cardiac and peripheral muscle function in CHF. One is ongoing; the other one, which just ended, failed to show an improvement in exercise capacity in the population studied. A benefit was evident only in a subgroup of patients with preserved ejection fraction and impaired baseline exercise duration.

Angiotensin-converting enzyme inhibition and the progression of congestive cardiomyopathy. Effects on left ventricular and myocyte structure and function

BACKGROUND

Clinical trials have demonstrated that angiotensin-converting enzyme inhibition (ACEI) improves survival in patients with long-term left ventricular (LV) dysfunction. However, it remained unclear from these clinical reports whether the beneficial effects of ACEI were due to direct improvements in LV myocardial structure and function. Accordingly, the overall objective of the present study was to examine the direct effects of ACEI on both LV and myocyte structure and function in the setting of cardiomyopathic disease.

METHODS AND RESULTS

LV and isolated myocyte function and structure were examined in control dogs (n = 6), in dogs after the development of dilated cardiomyopathy caused by rapid ventricular pacing (RVP, 216 beats per minute, 4 weeks, n = 6), and in dogs with RVP and concomitant ACEI (RVP/ACEI, fosinopril 30 mg/kg BID, n = 6). LV ejection fraction fell with RVP compared with control values (35 +/- 3 versus 73 +/- 2%, P < .05) and was higher with RVP/ACEI compared with RVP values (41 +/- 4%, P = .048). LV end-diastolic volume increased with RVP compared with control values (78 +/- 7 versus 101 +/- 7 cm3, P < .05) and was lower with RVP/ACEI (82 +/- 3 cm3, P < .05). Isolated myocyte length increased with RVP (182 +- 1 versus 149 +/- 1 micron), and the velocity of shortening decreased (36 +/- 1 versus 57 +/- 1 micron/s) compared with control values (P < .05). With RVP/ACEI, myocyte length was reduced (169 +/- 1 micron) and velocity of shortening was increased (45 +/- 1 micron/s) compared with RVP values (P < .05). Myocyte velocity of shortening after beta-adrenergic receptor stimulation with 25 nmol/L isoproterenol was reduced with RVP compared with control values (142 +/- 5 versus 193 +/- 8 micron/s, P < .05) and significantly improved with RVP/ACEI (166 +/- 6 micron/s, P < .05). In the RVP group, beta-adrenergic receptor density fell 26%, and cAMP production with beta-adrenergic receptor stimulation was reduced 48% from control values. RVP/ACEI resulted in a normalization of beta-adrenergic receptor density and cAMP production. LV myosin heavy-chain content when normalized to dry weight of myocardium was unchanged with RVP (149 +/- 11 mg per gram dry weight of myocardium [gdwt]) and RVP/ACEI (150 +/- 4 mg/gdwt) compared with control values (165 +/- 4 mg/gdwt). LV collagen content decreased with RVP compared with control values (7.6 +/- 0.4 versus 9.6 +/- 0.8 mg per gram wet weight of myocardium [gwwt], P < .05) but was increased with RVP/ACEI (14.4 +/- 1.3 mg/gwwt, P < .05).

CONCLUSIONS

Concomitant ACEI with chronic tachycardia reduced LV chamber dilation and improved myocyte contractile function and beta-adrenergic responsiveness. Contributory cellular and extracellular mechanisms for the beneficial effects of ACEI in this model of dilated cardiomyopathy included a normalization of beta-adrenergic receptor function and enhanced myocardial collagen support. The results from this study provide evidence that ACEI during the development of cardiomyopathic disease provided beneficial effects on LV myocyte contractile processes and myocardial structure.

Angiotensin-converting enzyme inhibitors and calcium antagonists after acute myocardial infarction

This article examines trials of the use of two types of drugs in the treatment of myocardial infarction: angiotensin-converting enzyme (ACE) inhibitors and calcium antagonists. ACE inhibitors are an established treatment for hypertension and heart failure and have been shown to reduce mortality from heart failure and after myocardial infarction. Six large studies have been carried out. In 1 in which an ACE inhibitor was given 3-16 days after infarction in patients with an ejection fraction < 40%, mortality was reduced by 17%. In a second study of patients who had evidence of heart failure and were followed up for 15 months, treatment with ACE inhibitors was given 3-10 days after myocardial infarction and mortality was reduced by 27%. Two other studies of 11,000 and 50,000 unselected patients with myocardial infarction showed only marginal clinical benefit. Calcium antagonists were introduced to treat hypertension and angina pectoris. In trials with patients with heart failure, the results have not been encouraging, and in some patients these agents seem to be harmful. Recently, long-acting calcium antagonists have become available, and these may avoid the deleterious effects of short-acting drugs. Since calcium antagonists act on smooth muscle, they may increase myocardial blood flow to improve function after "stunning" or "hibernation." This idea was investigated with a long-acting dihydroyridine calcium, antagonist in a randomized double-blind, placebo-controlled study (Doppler Flow, Echocardiography, and Functional Improvement Assessment of Nisoldipine Therapy-I--DEFIANT I), and a further study is being carried out. At present the widespread use of calcium antagonists after infarction is not recommended.

Changes in myocardial and vascular receptors in heart failure

Heart failure results in dramatic changes in certain neurotransmitter and hormone receptors. The majority of the changes occur in the heart and generally can be classified as regulatory phenomena that withdraw the failing heart from adrenergic stimulation. Of these, the most prominent is beta 1-receptor downregulation. Changes in vascular receptors are much less prominent and there is no direct evidence that any vascular receptor changes in heart failure. The changes that occur in myocardial receptors suggest that antiadrenergic therapy would be effective in the treatment of heart failure by removing adrenergic signaling transduced by the remaining components of the receptor pathways. Taken together, the receptor desensitization changes present in the failing heart provide a rationale for beta 1- plus beta 2-adrenergic blockade or even combined beta 1-, beta 2-alpha 1-adrenergic receptor blockade in heart failure.