New therapeutic options in congestive heart failure: Part I

The Structural and the Functional Aspects of Intercellular Communication in iPSC-Cardiomyocytes

Recent advances in the technology of producing novel cardiomyocytes from induced pluripotent stem cells (iPSC-cardiomyocytes) fuel new hope for future clinical applications. The use of iPSC-cardiomyocytes is particularly promising for the therapy of cardiac diseases such as myocardial infarction, where these cells could replace scar tissue and restore the functionality of the heart. Despite successful cardiogenic differentiation, medical applications of iPSC-cardiomyocytes are currently limited by their pronounced immature structural and functional phenotype. This review focuses on gap junction function in iPSC-cardiomyocytes and portrays our current understanding around the structural and the functional limitations of intercellular coupling and viable cardiac graft formation involving these novel cardiac muscle cells. We further highlight the role of the gap junction protein connexin 43 as a potential target for improving cell–cell communication and electrical signal propagation across cardiac tissue engineered from iPSC-cardiomyocytes. Better insight into the mechanisms that promote functional intercellular coupling is the foundation that will allow the development of novel strategies to combat the immaturity of iPSC-cardiomyocytes and pave the way toward cardiac tissue regeneration.

Role of biomarkers in the heart failure clinic

Heart failure (HF) is a common cardiovascular disease that has a complex pathophysiology. Because it is the final stage of many cardiovascular diseases, proper diagnosis and treatment are crucial for prolonging patients’ survival and improving their well-being. Several biomarkers have been identified in HF, and their roles in diagnosis and prognostication have been widely investigated. Among them, natriuretic peptides are key for diagnosing HF, predicting its prognosis, and monitoring the effectiveness of HF treatment. Moreover, natriuretic peptides can also be used to treat HF. In addition to natriuretic peptides, several other biomarkers were included in the most recent HF management guidelines. Thus, we reviewed the role of the biomarkers included in these guidelines and discussed future perspectives.

Clinical determinants and prognostic implications of renin and aldosterone in patients with symptomatic heart failure

Aims

Activation of the renin–angiotensin–aldosterone system plays an important role in the pathophysiology of heart failure (HF) and has been associated with poor prognosis. There are limited data on the associations of renin and aldosterone levels with clinical profiles, treatment response, and study outcomes in patients with HF.

Methods and results

We analysed 2,039 patients with available baseline renin and aldosterone levels in BIOSTAT‐CHF (a systems BIOlogy study to Tailored Treatment in Chronic Heart Failure). The primary outcome was the composite of all‐cause mortality or HF hospitalization. We also investigated changes in renin and aldosterone levels after administration of mineralocorticoid receptor antagonists (MRAs) in a subset of the EPHESUS trial and in an acute HF cohort (PORTO). In BIOSTAT‐CHF study, median renin and aldosterone levels were 85.3 (percentile_25–75 = 28–247) μIU/mL and 9.4 (percentile_25–75 = 4.4–19.8) ng/dL, respectively. Prior HF admission, lower blood pressure, sodium, poorer renal function, and MRA treatment were associated with higher renin and aldosterone. Higher renin was associated with an increased rate of the primary outcome [highest vs. lowest renin tertile: adjusted‐HR (95% CI) = 1.47 (1.16–1.86), P = 0.002], whereas higher aldosterone was not [highest vs. lowest aldosterone tertile: adjusted‐HR (95% CI) = 1.16 (0.93–1.44), P = 0.19]. Renin and/or aldosterone did not improve the BIOSTAT‐CHF prognostic models. The rise in aldosterone with the use of MRAs was observed in EPHESUS and PORTO studies.

Conclusions

Circulating levels of renin and aldosterone were associated with both the disease severity and use of MRAs. By reflecting both the disease and its treatments, the prognostic discrimination of these biomarkers was poor. Our data suggest that the “point” measurement of renin and aldosterone in HF is of limited clinical utility.

Phenotyping progression of secondary mitral regurgitation in chronic systolic heart failure

BACKGROUND

Secondary mitral regurgitation (sMR) drives adverse cardiac remodelling in patients with heart failure with reduced ejection fraction (HFrEF). Progression in severity over time contributes to a transition towards more advanced HF stages. Early identification of patients at risk for sMR progression remains challenging. We therefore sought to assess a broad spectrum of neurohumoral biomarkers in patients with HFrEF to explore their ability to predict progression of sMR.

METHODS

A total of 249 HFrEF patients were enrolled. Biomarkers encompassing key neurohumoral pathways in heart failure were sampled at baseline, and sMR progression was assessed over 3 years of follow-up.

RESULTS

Of 191 patients with nonsevere sMR at baseline, 18% showed progressive sMR within three years after study enrolment. Progression of sMR was associated with higher levels of MR-proADM (adj.OR 2.25, 95% CI 1.29-3.93; P = .004), MR-proANP (adj.OR 1.84, 95% CI 1.14-3.00; P = .012), copeptin (adj.OR 1.66, 95% CI 1.04-2.67; P = .035) and CT-pro-ET1 (adj.OR 1.68, 95% CI 1.06-2.68; P = .027) but not with NT-proBNP (P = .54).

CONCLUSION

Increased plasma levels of neurohumoral cardiac biomarkers are predictors of sMR progression in patients with HFrEF and add easily available incremental prognostic information for risk stratification. Importantly, NT-proBNP was not useful to predict progressive sMR in the present analysis. On the contrary, MR-proANP, primarily produced in the atria, copeptin partly triggered by intra-cardiac and intra-arterial pressures and MR-proADM, a marker of forward failure and peripheral released vasoactive CT-proET1, increase based on a progressive loading burden by sMR and may thus serve as better predictors of sMR progression.

Telmisartan and captopril ameliorate pregabalin-induced heart failure in rats

Pregabalin (PRG) is highly effective in the treatment of epilepsy, neuropathic pain and anxiety disorders. Despite its potential benefits, PRG administration has been reported to induce or exacerbate heart failure (HF). It has been previously documented that overactivation of the renin angiotensin system (RAS) is involved in HF pathophysiological mechanism. The target of the current study was to examine the possible cardioprotective effect of telmisartan (Tel), an angiotensin II type 1 receptor (AT1R) blocker, compared with that of captopril (Cap), an angiotensin converting enzyme (ACE) inhibitor, in ameliorating PRG-induced HF in rats by assessing morphometric, echocardiographic and histopathological parameters. Furthermore, to investigate the role of RAS blockade by the two drugs in guarding against PRG-induced changes in cardiac angiotensin 1-7 (Ang 1-7) and angiotensin II (Ang II) levels, in addition to myocardial expression of ACE2, ACE, Mas receptor (MasR) and AT1R. Results showed that PRG administration induced morphometric, echocardiographic and histopathological deleterious alterations and significantly elevated cardiac Ang II, ACE and AT1R levels, while reduced Ang 1-7, ACE2 and MasR cardiac levels. Concurrent treatment with either Tel or Cap reversed PRG-induced morphometric, echocardiographic and histopathological abnormalities and revealed prominent protection against PRG-induced HF via downregulation of ACE/Ang II/AT1R and upregulation of ACE2/Ang 1-7/MasR axes. These are the first findings to demonstrate that the potential benefits of Tel and Cap are mediated by counteracting the altered balance between the RAS axes induced by PRG. Hence; Tel and Cap may attenuate PRG-induced HF partially through stimulation of ACE2/Ang 1-7/MasR pathway.

Mid-regional pro-atrial natriuretic peptide for the early detection of non-acute heart failure

BACKGROUND

Diagnosing non-acute heart failure (HF) remains challenging, notably in the early stages of the syndrome. The diagnostic value of mid-regional pro-atrial natriuretic peptide (MR-proANP) has been proven in acute onset HF, but its role in early non-acute HF is unknown. We aimed to determine the diagnostic value of MR-proANP in suspected non-acute HF.

METHODS AND RESULTS

In total, 721 people suspected of non-acute HF in primary care underwent standardised diagnostic work-up including chest X-ray, electrocardiogram, N-terminal pro-B-type natriuretic peptide (NT-proBNP) measurement and echocardiography. Of these, 245 people underwent additional MR-proANP measurements. The outcome of HF was assessed by an expert panel comprised of two cardiologists and one expert physician, who used all available diagnostic information including echocardiography, but were blinded to biomarker results. Of the 245 people (mean age 71.0 years, 62.9% female), 72 (29.4%) were diagnosed with HF. The c-statistics of MR-proANP and NT-proBNP as single diagnostic test were 0.77 [95% confidence interval (CI) 0.70-0.84] and 0.79 (95% CI 0.73-0.86), respectively. The cut-point with the highest accuracy for MR-proANP was 120 pmol/L [sensitivity/specificity/positive predictive value (PPV)/negative predictive value (NPV) 0.72, 0.69, 0.46, and 0.86, respectively], and the best exclusionary cut-point was 40 pmol/L (sensitivity/specificity/PPV/NPV 0.99, 0.06, 0.30, and 0.92, respectively). After addition of MR-proANP on top of a previously validated clinical model, the c-statistic rose from 0.82 (95% CI 0.76-0.88) to 0.86 (95% CI 0.80-0.92), and with the addition of NT-proBNP to 0.87 (95% CI 0.81-0.92). No sex interactions between the biomarkers and HF were found in the multivariable models.

CONCLUSION

MR-proANP provides added diagnostic value in suspected non-acute HF, similar to NT-proBNP.

Endoplasmic Reticulum Protein TXNDC5 Augments Myocardial Fibrosis by Facilitating Extracellular Matrix Protein Folding and Redox-Sensitive Cardiac Fibroblast Activation

RATIONALE

Cardiac fibrosis plays a critical role in the pathogenesis of heart failure. Excessive accumulation of extracellular matrix (ECM) resulting from cardiac fibrosis impairs cardiac contractile function and increases arrhythmogenicity. Current treatment options for cardiac fibrosis, however, are limited, and there is a clear need to identify novel mediators of cardiac fibrosis to facilitate the development of better therapeutics. Exploiting coexpression gene network analysis on RNA sequencing data from failing human heart, we identified TXNDC5 (thioredoxin domain containing 5), a cardiac fibroblast (CF)-enriched endoplasmic reticulum protein, as a potential novel mediator of cardiac fibrosis, and we completed experiments to test this hypothesis directly.

OBJECTIVE

The objective of this study was to determine the functional role of TXNDC5 in the pathogenesis of cardiac fibrosis.

METHODS AND RESULTS

RNA sequencing and Western blot analyses revealed that TXNDC5 mRNA and protein were highly upregulated in failing human left ventricles and in hypertrophied/failing mouse left ventricle. In addition, cardiac TXNDC5 mRNA expression levels were positively correlated with those of transcripts encoding transforming growth factor β1 and ECM proteins in vivo. TXNDC5 mRNA and protein were increased in human CF (hCF) under transforming growth factor β1 stimulation in vitro. Knockdown of TXNDC5 attenuated transforming growth factor β1-induced hCF activation and ECM protein upregulation independent of SMAD3 (SMAD family member 3), whereas increasing expression of TXNDC5 triggered hCF activation and proliferation and increased ECM protein production. Further experiments showed that TXNDC5, a protein disulfide isomerase, facilitated ECM protein folding and that depletion of TXNDC5 led to ECM protein misfolding and degradation in CF. In addition, TXNDC5 promotes hCF activation and proliferation by enhancing c-Jun N-terminal kinase activity via increased reactive oxygen species, derived from NAD(P)H oxidase 4. Transforming growth factor β1-induced TXNDC5 upregulation in hCF was dependent on endoplasmic reticulum stress and activating transcription factor 6-mediated transcriptional control. Targeted disruption of Txndc5 in mice (Txndc5^-/-) revealed protective effects against isoproterenol-induced cardiac hypertrophy, reduced fibrosis (by ≈70%), and markedly improved left ventricle function; post-isoproterenol left ventricular ejection fraction was 59.1±1.5 versus 40.1±2.5 (P<0.001) in Txndc5^-/- versus wild-type mice, respectively.

CONCLUSIONS

The endoplasmic reticulum protein TXNDC5 promotes cardiac fibrosis by facilitating ECM protein folding and CF activation via redox-sensitive c-Jun N-terminal kinase signaling. Loss of TXNDC5 protects against β agonist-induced cardiac fibrosis and contractile dysfunction. Targeting TXNDC5, therefore, could be a powerful new therapeutic approach to mitigate excessive cardiac fibrosis, thereby improving cardiac function and outcomes in patients with heart failure.

Palliation of heart failure

Heart failure is the major cause of morbidity and mortality in the United States. Stage D heart failure has a greater mortality rate than many cancers and has equivalent symptom burden and severity. There has been a paradigm shift in our understanding of the pathophysiology of heart failure. Progressive heart failure is associated with ventricular remodeling and a maladaptive neurohumoral response. Drug classes have evolved that curtail ventricular remodeling, and blunt neurohumoral responses reduce morbidity and mortality. Despite combination drug and device therapies, the management of Stage D heart failure includes palliation. Both cardiology and palliative specialists need to learn from one another in order to palliate these highly symptomatic patients. Such collaboration will enhance care and are the basis for well-conceived research trials.

Pigment Epithelium-Derived Factor (PEDF) Improves Ischemic Cardiac Functional Reserve Through Decreasing Hypoxic Cardiomyocyte Contractility Through PEDF Receptor (PEDF-R)

BACKGROUND

Pigment epithelium-derived factor (PEDF), which belongs to the noninhibitory serpin family, has shown the ability to stimulate several physiological processes, such as antiangiogenesis, anti-inflammation, and antioxidation. In the present study, the effects of PEDF on contractility and calcium handling of rat ventricular myocytes were investigated.

METHODS AND RESULTS

Adult Sprague-Dawley rat models of acute myocardial infarction (AMI) were surgically established. PEDF-lentivirus was delivered into the myocardium along and away from the infarction border to overexpress PEDF. Video edge detection was used to measure myocyte shortening in vitro. Intracellular Ca(2+) was measured in cells loaded with the Ca(2+) sensitive fluorescent indicator, Fura-2-acetoxymethyl ester. PEDF local overexpression enhanced cardiac functional reserve in AMI rats and reduced myocardial contracture bordering the infracted area. Exogenous PEDF treatment (10 nmol/L) caused a significant decrease in amplitudes of isoproterenol-stimulated myocyte shortening, Ca(2+) transients, and caffeine-evoked Ca(2+) transients in vitro. We then tested a potential role for PEDF receptor-mediated effects on upregulation of protein kinase C (PKC) and found evidence of signaling through the diacylglycerol/PKCα pathway. We also confirmed that pretreatment of cardiomyocytes with PEDF exhibited dephosphorylation of phospholamban at Ser(16), which could be attenuated with PKC inhibition.

CONCLUSIONS

The results suggest that PEDF depresses myocyte contractility by suppressing phosphorylation of phospholamban and Ca(2+) transients in a PKCα-dependent manner through its receptor, PEDF receptor, therefore improving cardiac functional reserve during AMI.

Rodent models of heart failure: an updated review

Heart failure (HF) is one of the major health and economic burdens worldwide, and its prevalence is continuously increasing. The study of HF requires reliable animal models to study the chronic changes and pharmacologic interventions in myocardial structure and function and to follow its progression toward HF. Indeed, during the past 40 years, basic and translational scientists have used small animal models to understand the pathophysiology of HF and find more efficient ways of preventing and managing patients suffering from congestive HF (CHF). Each species and each animal model has advantages and disadvantages, and the choice of one model over another should take them into account for a good experimental design. The aim of this review is to describe and highlight the advantages and drawbacks of some commonly used HF rodents models, including both non-genetically and genetically engineered models, with a specific subchapter concerning diastolic HF models.

Prevention of renal ischemia-reperfusion injury by short hairpin RNA of endothelin A receptor in a rat model

Endothelin A receptor (ETaR) is a key molecule involved in a variety of biological events such as vessel contraction and inflammatory response in ischemia-reperfusion (I/R) injury. RNA interference using short hairpin RNA (shRNA) is a powerful tool to silence gene expression. Here, the effect of ETaR shRNA on I/R injury in rats was studied. A more effective shRNA sequence out of two constructed into plasmid vectors was selected using the A-10 cell line, and was then applied to a rat model. Twenty-eight male Sprague-Dawley rats were randomized into four groups: Sham, shRNA, vector and phosphate-buffered saline (PBS). Renal I/R injury was induced by clamping the left renal pedicle for one hour followed by reperfusion for 24 h. ETaR shRNA (100 μg) plasmid was administered by renal vein injection 48 h before clamping. The expression of both ETaR mRNA and protein was lowered by ETaR shRNA treatment compared with that in the vector and PBS groups; serum creatinine and blood urea nitrogen were significantly decreased; the semi-quantitative score of renal structural damage was improved; the mRNA level of endothelin 1 (ET-1), tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), macrophage inflammatory protein 2 (MIP-2) and monocyte chemoattractant protein 1 (MCP-1) was reduced, but nitric oxide (NO) production in kidney tissues was increased (P < 0.05). In conclusion, ETaR shRNA partially silenced ETaR expression in I/R injury kidneys, reduced the mRNA level of ET-1, inflammatory mediators including TNF-α, IL-6, MIP-2 and MCP-1, increased NO production, and ultimately improved renal function and structure.

Intermedin elicits a negative inotropic effect in rat papillary muscles mediated by endothelial-derived nitric oxide

Intermedin (IMD) is a novel vasoactive peptide from the calcitonin gene-related peptide (CGRP) implicated in cardiac regulation, yet the contractile effects of IMD remain controversial, since previous studies in vivo and isolated cardiomyocytes documented contradictory results. We hypothesized cardiac endothelial cells involvement in IMD modulation of cardiac function as an explanation for these opposing observations. With this in mind, we investigated the direct action of increasing concentrations of IMD (10(-8) to 10(-6)M) on myocardial performance parameters in rat left ventricular (LV) papillary muscles with and without endocardial endothelium (EE) and in presence of receptor antagonists and intracellular pathways inhibitors. In LV papillary muscles with intact EE, IMD induced a concentration-dependent negative inotropic action (%decrease relative to baseline, at IMD concentration of 10(-6)M, active tension of 14 ± 4%, and maximum velocity of tension rise of 10 ± 4%). These effects were blunted by EE removal, AM receptor antagonist (AM(22-52)), and CGRP receptor antagonist (CGRP(8-37)). Additionally, nitric oxide (NO) synthase inhibition with N(G)-nitro-l-arginine (l-NAME) in muscles with and without EE and guanylyl cyclase inhibition with {1H-[1,2,4]oxadiazole-[4,4-a]-quinoxalin-1-one} not only blunted the negative inotropic action of IMD but also unmasked IMD-positive inotropic effect dependent on CGRP receptor PKA activation. Western blot quantification of phosphorylated cardiac troponin I (P-cTnI) in IMD-treated papillary muscles revealed a significant increase in P-cTnI when compared with untreated muscles, while in l-NAME-pretreated papillary muscles IMD failed to increase P-cTnI. Finally, we found that stimulation of both EE and microvascular endothelial cells with IMD significantly increased NO production by 40 ± 3 and 38 ± 3%, respectively, suggesting the role of cardiac endothelial cells in NO production upon IMD stimulation. Our findings establish IMD negative inotropic effect in isolated myocardium due to NO/cGMP pathway activation with concomitant thin myofilament desensitization by increase in cTnI phosphorylation and provide a coherent explanation for the previously reported contradictory results.

Inhibiting matrix metalloproteinase by cell-based timp-3 gene transfer effectively treats acute and chronic ischemic cardiomyopathy

After a myocardial infarction (MI), an increase in the cardiac ratio of matrix metalloproteinases (MMPs) relative to their inhibitors (TIMPs) causes extracellular matrix modulation that leads to ventricular dilatation and congestive heart failure. Cell therapy can mitigate these effects. In this study, we tested whether increasing MMP inhibition via cell-based gene transfer of Timp-3 further preserved ventricular morphometry and cardiac function in a rat model of MI. We also measured the effect of treatment timing. We generated MI (coronary artery ligation) in adult rats. Three or 14 days later, we implanted medium (control) or vascular smooth muscle cells transfected with empty vector (VSMCs) or Timp-3 (C-TIMP-3) into the peri-infarct region (n = 15-24/group). We assessed MMP-2 and -9 expression and activity, TIMP-3, and TNF-α expression, cell apoptosis, infarct size and thickness, ventricular morphometry, and cardiac function (by echocardiography). Relative to medium, VSMCs delivered at either time point significantly reduced cardiac expression and activity of MMP-2 and -9, reduced expression of TNF-α, and increased expression of TIMP-3. Cell therapy also reduced apoptosis and scar area, increased infarct thickness, preserved ventricular structure, and reduced functional loss. All these effects were augmented by C-TIMP-3 treatment. Survival and cardiac function were significantly greater when VSMCs or C-TIMP-3 were delivered at 3 (vs. 14) days after MI. Upregulating post-MI cardiac TIMP-3 expression via cell-based gene therapy contributed additional regulation of MMP, TIMP, and TNF-α levels, thereby boosting the structural and functional effects of VSMCs transplanted at 3 or 14 days after an MI in rats. Early treatment may be superior to late, though both are effective.

Pharmacological treatment of chronic systolic heart failure: are we scraping the bottom of the barrel?

Heart failure is a major health problem and its prevalence is growing, primarily as a consequence of the aging of the population. Recently, we have witnessed significant progress in reducing the mortality associated with chronic heart failure due to the introduction of renin-angiotensin-aldosterone system inhibitors, beta-blocking agents and the use of electrical devices. However, the prognosis of heart failure is still so disappointing that it remains the leading cause of death in developed countries. This grim record impels the search for new therapeutic strategies. The objective of this paper is to briefly review the results of some recent trials that have been put in place to test the effects of drugs that are deemed to be potentially capable of improving the prognosis of chronic systolic heart failure patients. Despite compelling theoretical premises, the results to date appear to be weak or even disappointing.

Cardiac resynchronization therapy: assessment of dyssynchrony and effects on metabolism

In recent years cardiac resynchronization therapy has emerged as a promising new treatment strategy in a subgroup of patients with congestive heart failure and an asynchronous contraction pattern. By simultaneously pacing both right ventricular apex and lateral side of the left ventricle, ventricular synchrony can be partially restored and beneficial effects on cardiac performance can be observed. This review discusses the principles of ventricular dyssynchrony, and the acute and chronic effects of cardiac resynchronization therapy on systolic function, cardiac metabolism, and clinical parameters. Furthermore, the issue of identifying patients who do not respond to this therapy is addressed.

Stem cells for cardiac regeneration by cell therapy and myocardial tissue engineering

Congestive heart failure, which often occurs progressively following a myocardial infarction, is characterized by impaired myocardial perfusion, ventricular dilatation, and cardiac dysfunction. Novel treatments are required to reverse these effects - especially in older patients whose endogenous regenerative responses to currently available therapies are limited by age. This review explores the current state of research for two related approaches to cardiac regeneration: cell therapy and tissue engineering. First, to evaluate cell therapy, we review the effectiveness of various cell types for their ability to limit ventricular dilatation and promote functional recovery following implantation into a damaged heart. Next, to assess tissue engineering, we discuss the characteristics of several biomaterials for their potential to physically support the infarcted myocardium and promote implanted cell survival following cardiac injury. Finally, looking ahead, we present recent findings suggesting that hybrid constructs combining a biomaterial with stem and supporting cells may be the most effective approaches to cardiac regeneration.

Nonselective ETA/ETB-receptor blockade increases systemic blood pressure of Bio 14.6 cardiomyopathic hamstersThis article is one of a selection of papers published in the special issue (part 1 of 2) on Forefronts in Endothelin

To examine the role of endothelin ETA and ETB receptors in congestive heart failure due to cardiomyopathy, the effect of chronic treatment with selective ETA- and ETB-receptor antagonists (atrasentan and A-192621, respectively), alone and in combination, was assessed on functional and biochemical parameters of 52-week-old Bio 14.6 cardiomyopathic hamsters. Compared with control animals, cardiomyopathic hamsters treated for 9 weeks with atrasentan showed no variation in MAP; however, selective ETB- and combined nonselective ETA- and ETB-receptor antagonists increased systemic blood pressure. After selective ETB-receptor blockade, plasma endothelin levels were augmented. Importantly, this increase was highly enhanced (more than 8-fold) by concomitant ETA-receptor antagonism. Furthermore, the left ventricle : body weight ratio of cardiomyopathic hamsters treated with A-192621, alone or in combination with atrasentan, was significantly increased. On the other hand, decreased left ventricular end-diastolic pressure was observed in cardiomyopathic hamsters after selective ETA- or combined nonselective ETA/ETB-receptor antagonism, while only selective ETA-receptor blockade reduced left ventricular endothelin levels. Our results suggest that, in congestive heart failure, ETB receptors are essential to limit circulating endothelin levels, which may argue for improved cardiac benefits after long-term treatment with highly selective ETA-receptor antagonists.

Cardiopulmonary exercise testing and its application

Cardiopulmonary exercise testing (CPET) has become an important clinical tool to evaluate exercise capacity and predict outcome in patients with heart failure and other cardiac conditions. It provides assessment of the integrative exercise responses involving the pulmonary, cardiovascular and skeletal muscle systems, which are not adequately reflected through the measurement of individual organ system function. CPET is being used increasingly in a wide spectrum of clinical applications for evaluation of undiagnosed exercise intolerance and for objective determination of functional capacity and impairment. This review focuses on the exercise physiology and physiological basis for functional exercise testing and discusses the methodology, indications, contraindications and interpretation of CPET in normal people and in patients with heart failure.

Effects of age on plasma matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs)

BACKGROUND

The mechanisms causing age-dependent changes in left ventricular (LV) structure and function are not completely understood. Matrix metalloproteinase (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) constitute one important proteolytic pathway affecting LV remodeling. However, whether these determinants of extracellular matrix (ECM) composition change as a function of age has not been examined in an aging population free of clinically significant cardiovascular disease.

METHODS AND RESULTS

Subjects (n = 77, age 20-90 years) with no evidence of cardiovascular disease underwent echocardiography and measurement of plasma MMP-2, 7, 8, and 9 and TIMP-1, 2, and 4 (enzyme-linked immunosorbent assay). As subject age increased, volume/mass ratio decreased and mitral E/A ratio decreased. As subject age increased, MMP-2 increased (from 1188 +/- 99 ng/mL to 1507 +/- 76 ng/mL), MMP-7 increased (from 1.2 +/- 0.1 ng/mL to 3.1 +/- 0.6 ng/mL), MMP-9 decreased (from 29 +/- 7 ng/mL to 8 +/- 2 ng/mL), and TIMP-1, 2, and 4 increased (from 728 +/- 46 ng/mL to 1093 +/- 73 ng/mL, from 34 +/- 5 ng/mL to 53 +/- 6 ng/mL, and from 1.26 +/- 0.22 ng/mL to 2.34 +/- 0.30 ng/mL, respectively) (all P < .05). There were significant correlations between decreased LV volume/mass and E/A ratio and increased MMP-7 and TIMP-1 and 4.

CONCLUSIONS

MMPs and TIMPs changed as a function of age in the absence of clinically significant cardiovascular disease. These age-dependent alterations in MMP and TIMP profiles favor ECM accumulation and were associated with concentric remodeling and decreased LV diastolic function. Because of these age-dependent changes in this proteolytic system, the superimposition of disease processes such as myocardial infarction or hypertensive heart disease in the older subject may result in different myocardial ECM remodeling than that seen in a younger subject.

Role of inflammation in the progression of heart failure

Chronic heart failure (HF) is a disorder characterized in part by immune activation and inflammation. Thus, patients with HF have elevated levels of a number of inflammatory cytokines, both in the circulation and in the failing heart itself. Several mechanisms for this immune activation, which are not mutually exclusive, have been suggested, including neurohormonal activation, hemodynamic overload, and activation of the innate immune system secondary to cardiac stress. Importantly, experimental studies have shown that inflammatory cytokines such as tumor necrosis factor-alpha, interleukin-1b, and monocyte chemoattractant peptide-1 may contribute to the development and progression of HF by promoting myocardial hypertrophy, activating matrix metalloproteinases, provoking contractile dysfunction, and inducing apoptosis. However, inflammatory cytokines may also have adaptive and cardioprotective effects. This important aspect of cytokine biology must be kept in mind when designing new immunomodulatory treatment modalities in HF.

Keys to successful cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) improves functional status in selected groups of patients with heart failure and has achieved widespread use. However, approximately one-third of patients fail to benefit from CRT. Many of these failures can be attributed to improper patient selection, suboptimal left ventricular lead placement and device programming and inadequate medical therapy. This article addresses these issues and proposes an approach to improving the results of CRT.

Targeting SERCA2a as an innovative approach to the therapy of congestive heart failure

CHF prevalence is continuously increasing worldwide and maintains one of the poorest prognoses of any major disease. Abundant evidence points to derangement of Ca(2+) cycling as the primary biochemical mark of the failing myocyte. Istaroxime is a novel compound with a dual mechanism of action: inhibition of Na(+), K(+)-ATPase and stimulation of SERCA2a. The increase in cytoplasmic Ca(2+) due to Na(+), K(+)-ATPase inhibition together with greater sarcoplasmic reticulum reloading result in both increased inotropy and lusitropy. This effect is seen in normal and failing in vitro and in vivo models. Istaroxime improvement of the contraction-relaxation cycle constitutes a novel therapeutic approach to the treatment of heart failure.

[Primary prophylaxis with the implantable cardioverter-defibrillator in heart failure: a clinical point of view]

The implantable cardioverter-defibrillator (ICD) is one of the great inventions of modern cardiology. Its use for the prevention of sudden death in patients with left ventricular dysfunction has meant that clinical cardiologists are now fully involved in decision-making on the implantation of these devices. The majority of clinical trials, which have used low ejection fraction as the only or main criterion for patient recruitment, have shown that ICD use leads to a significant improvement in survival. Three trials, two of which were carried out soon after myocardial infarction and one of which was performed at the same time as surgical revascularization, were exceptions. However, it is important to be aware that the improvements observed in the most recent trials have not been as large as those seen in the initial studies. Reduced efficacy has meant that in the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT), for instance, 25 ICDs had to be implanted to save one life over a 2-year period. The most likely explanation for this observation is that the better prognosis achieved by present-day pharmacologic treatment of heart failure has reduced the margin of benefit associated with ICD use. Another consequence is that depressed left ventricular ejection fraction has lost some of its specificity in predicting sudden death. New predictive variables are needed to improve risk stratification in this population. Without these variables, the use of ICDs in the primary prevention of sudden death in patients with left ventricular dysfunction will not seem a very attractive option from the point of view of good clinical practice.

Beneficial effects of combined benazepril-amlodipine on cardiac nitric oxide, cGMP, and TNF-alpha production after cardiac ischemia

The aim of this study was to determine if myocardial inflammation is increased after myocardial ischemia and whether angiotensin-converting enzyme inhibitors, calcium channel blockers, or diuretics decrease mediators of inflammation in rats with induced myocardial ischemia. Changes in cardiac interstitial fluid (CIF) levels of nitric oxide metabolites (NOX), cyclic guanosine 3',5'-monophosphate (cGMP), angiotensin II (Ang II), and tumor necrosis factor-alpha (TNF-alpha) were monitored with/without oral administration of benazepril, amlodipine, combined benazepril-amlodipine, or hydrochlorothiazide. Using a microdialysis technique, levels of several mediators of inflammation were measured after sham operation or 30-minute occlusion of the left anterior descending coronary artery. Compared with sham animals, levels of CIF NOX and cGMP were decreased in animals with ischemia (P < 0.001). Benazepril or amlodipine significantly increased NOX levels (P < 0.05 vs. untreated ischemia), but only benazepril significantly increased cGMP (P < 0.05). Combined benazepril-amlodipine further increased CIF NOX and cGMP (P < 0.001), compared with either drug alone. CIF Ang II and TNF-alpha in sham animals did not change significantly. In animals with ischemia, CIF Ang II and TNF-alpha increased progressively. Amlodipine alone, benazepril alone, or combined benazepril-amlodipine significantly reduced TNF-alpha (P < 0.01 for monotherapies and P < 0.001 for combination therapy). Hydrochlorothiazide did not cause significant changes in NOX, cGMP, or TNF-alpha. Combination benazepril-amlodipine may be beneficial for managing cardiac ischemia.

Imaging stem cells implanted in infarcted myocardium

Stem cell-based cellular cardiomyoplasty represents a promising therapy for myocardial infarction. Noninvasive imaging techniques would allow the evaluation of survival, migration, and differentiation status of implanted stem cells in the same subject over time. This review describes methods for cell visualization using several corresponding noninvasive imaging modalities, including magnetic resonance imaging, positron emission tomography, single-photon emission computed tomography, and bioluminescent imaging. Reporter-based cell visualization is compared with direct cell labeling for short- and long-term cell tracking.

Gene therapy: role in myocardial protection

Heart failure associated with coronary artery disease is a major cause of morbidity and mortality. Recent developments in the understanding of the molecular mechanisms of heart failure have led to the identification of novel therapeutic targets which, combined with the availability of efficient gene delivery vectors, offer the opportunity for the design of gene therapies for protection of the myocardium. Viral-based therapies have been developed to treat polygenic and complex diseases such as myocardial ischaemia, hypertension, atherosclerosis and restenosis. Some of these experimental therapies are now undergoing clinical evaluation in patients with cardiovascular diseases. In this review we will focus on the latest advances in the field of gene therapy for treatment of heart failure and their clinical application.

Valvular heart disease and heart failure: dental management considerations

Approximately 5 million people are diagnosed with valvular heart disease in the United States each year. Many of these will present to the general dentist for routine dental care. The dentist must then understand the implications of this disease process to treat these patients safely and effectively. Of course patients with pathologic valve disease are managed in close consultation with their physicians. Even so, a dentist with knowledge of the disease process, as well as its diagnosis and treatment, has greater confidence when treating these patients. This article summarizes issues related to valvular heart disease and heart failure and provides guidance to dentists treating patients with such conditions.

Cardiomyopathy, familial dilated

Dilated cardiomyopathy (DCM) is a heart muscle disease characterized by ventricular dilatation and impaired systolic function. Patients with DCM suffer from heart failure, arrhythmia, and are at risk of premature death. DCM has a prevalence of one case out of 2500 individuals with an incidence of 7/100,000/year (but may be under diagnosed). In many cases the disease is inherited and is termed familial DCM (FDC). FDC may account for 20–48% of DCM. FDC is principally caused by genetic mutations in FDC genes that encode for cytoskeletal and sarcomeric proteins in the cardiac myocyte. Family history analysis is an important tool for identifying families affected by FDC. Standard criteria for evaluating FDC families have been published and the use of such criteria is increasing. Clinical genetic testing has been developed for some FDC genes and will be increasingly utilized for evaluating FDC families. Through the use of family screening by pedigree analysis and/or genetic testing, it is possible to identify patients at earlier, or even presymptomatic stages of their disease. This presents an opportunity to invoke lifestyle changes and to provide pharmacological therapy earlier in the course of disease. Genetic counseling is used to identify additional asymptomatic family members who are at risk of developing symptoms, allowing for regular screening of these individuals. The management of FDC focuses on limiting the progression of heart failure and controlling arrhythmia, and is based on currently accepted treatment guidelines for DCM. It includes general measures (salt and fluid restriction, treatment of hypertension, limitation of alcohol intake, control of body weight, moderate exercise) and pharmacotherapy. Cardiac resynchronization, implantable cardioverter defibrillators and left ventricular assist devices have progressively expanding usage. Patients with severe heart failure, severe reduction of the functional capacity and depressed left ventricular ejection fraction have a low survival rate and may require heart transplant.

Effects of the ??2-Adrenergic/DA2-Dopaminergic Agonist CHF-1024 in Preventing Ventricular Arrhythmogenesis and Myocyte Electrical Remodeling, in a Rat Model of Pressure-Overload Cardiac Hypertrophy

Cardiac hypertrophy induces morpho-functional myocardial alterations favoring arrhythmogenesis, especially under specific conditions such as sympathetic stimulation. We analyzed whether the dopaminergic agent CHF-1024, given its effect in decreasing adrenergic drive and collagen deposition in hypertrophied hearts, can also reduce arrhythmia vulnerability. Eighty-one male Wistar rats with intrarenal aortic coarctation and 18 control animals were studied. Fifty-eight banded animals were treated with CHF-1024 at four different doses (6, 2, 0.67, or 0.067 mg/Kg/die). One month after aortic ligature, spontaneous and sympathetic-induced ventricular arrhythmic events (VAEs) were telemetrically recorded in conscious animals. After sacrifice, membrane capacitance (Cm) and action potential duration (APD) were measured in isolated left ventricular myocytes (patch-clamp). In all groups, spontaneous VAEs were negligible whereas they significantly increased during sympathetic activation (stress exposure). Banded untreated animals showed a higher number of stress-induced VAEs, longer action potentials, and larger values of Cm and cell width as compared with control group. The treatment with CHF-1024 exhibited an antiarrhythmic effect, abolished APD prolongation, and reduced cell width at all doses. The lowest dose also prevented Cm increase. In conclusion, we demonstrated that in this model of pressure-overload hypertrophy CHF-1024 reduces arrhythmogenesis and causes a recovery of cell excitable properties toward a normal phenotype.

Levosimendan for the treatment of acute heart failure syndromes

Levosimendan is a novel calcium-sensitising agent that has been shown to have beneficial inotropic, metabolic and vasodilatory effects in the treatment of acute and advanced chronic heart failure. Levosimendan binds to troponin-C in cardiomyocytes and, thereby, improves cardiac contractility without disturbing the metabolic status of the heart and increasing myocardial oxygen demand or provoking fatal cardiac arrhythmias. Levosimendan also opens ATP-sensitive potassium channels, causing peripheral arterial and venous dilatation, and increasing coronary flow reserve. When it is given as a short-term therapy, levosimendan enhances cardiac output, reduces systemic vascular resistance and lowers pulmonary capillary wedge pressure. Clinical outcomes were significantly reduced in decompensated or postmyocardial infarction heart failure patients who received levosimendan, compared with those on dobutamine or placebo. Recent investigations focusing on the anti-inflammatory and antiapoptotic actions of levosimendan in the failing heart indicate that improvement of cardiac contractile performance is closely related with the drug-induced reduction of circulating pro-inflammatory cytokines and apoptosis inducers. The most common adverse effects of levosimendan treatment are hypotension and headache. Overall, levosimendan represents an effective and safe option for the treatment of decompensated heart failure patients.

The potential of endothelin antagonism as a therapeutic approach

Endothelin (ET) is a pivotal physiological regulator of blood pressure through its effects on blood vessels, heart, lung and kidneys, and the ET system can be overactive in disorders such as pulmonary hypertension, heart failure and renal disease. Such observations stimulated interest among scientists and pharmaceutical companies that have set up high-throughput screens to search for antagonists of ET receptors. The emerging compounds have been tested in animals with exciting results, leading to great hope that such inhibitors could be translated into human drugs with desirable therapeutic activities and few side effects. This review will describe the most relevant results obtained in experimental animals in a wide variety of disease conditions and focus on the data of selected compounds that have been employed in clinical trials.

Effects of bisoprolol treatment for chronic heart failure initiated and followed up by primary care physicians

Primary care physicians prescribe beta-blockers for chronic heart failure infrequently. The aims of the study were to assess the effects of beta-blocker treatment in out-clinic patients with regard to NYHA class and frequency of adverse events. Beta-blocker treatment was initiated and followed up by primary care physicians.

METHODS

Chronic heart failure patients already treated with ACE-inhibitors and diuretics were included. The 24-week follow-up consisted of a titration phase followed by a maintenance phase. The patients received the beta-blocker bisoprolol with an initial dose of 1.25 mg and a maximal dose of 10 mg.

RESULTS

NYHA class II, III and IV had 174, 146, and one patient, respectively. Treatment duration lasted 189+/-73 days with a maximal bisoprolol dose of 7.2+/-3.2 mg. Sixty-one percent of the patients tolerated at least 7.5 mg bisoprolol. The NYHA class improved from 2.4+/-0.5 at baseline to 1.8+/-0.6 at week 24 (P<0.001). At final assessment, 74% of the patients showed an improvement. The number of permanent treatment withdrawals was 57 (17%). Death occurred in six patients and hospitalisation in 38 patients.

CONCLUSIONS

Bisoprolol treatment in patients with chronic heart failure was effectively and safely carried out by primary care physicians.

Neurohormonal activation in congestive heart failure and the role of vasopressin

Vasoactive neurohormonal systems (eg, sympathetic nervous system [SNS], renin-angiotensin-aldosterone system, and arginine vasopressin [AVP]) are defense mechanisms designed to preserve arterial volume and circulatory homeostasis during periods of low cardiac output. Neurohormonal systems, which are normally stimulated under conditions of acute volume depletion, are activated by the low cardiac output and arterial pressure. However, sustained and chronic activation of these systems, as occurs in congestive heart failure (CHF), can cause progressive ventricular remodeling and worsening heart failure. Vasoconstriction, water retention, and increased blood volume are results of the activation of the SNS, the renin-angiotensin pathway, and AVP secretion. These effects can accelerate progression of CHF, contributing to increased morbidity and mortality. AVP regulates vascular tone and free-water reabsorption, respectively, through the vasopressin V(1a) and V(2) receptor subtypes and therefore is a potential neurohormonal target in the treatment of CHF.

Hyponatremia in congestive heart failure

Hyponatremia has been identified as a risk factor for increased morbidity and mortality in patients with congestive heart failure (CHF) and other edematous disorders and can lead to severe neurologic derangements. Low cardiac output and blood pressure associated with CHF triggers a compensatory response by the body that activates several neurohormonal systems designed to preserve arterial blood volume and pressure. Hyponatremia in patients with CHF is primarily caused by increased activity of arginine vasopressin (AVP). AVP increases free-water reabsorption in the renal collecting ducts, increasing blood volume and diluting plasma sodium concentrations. Hyponatremia may also be triggered by diuretic therapy used in the management of symptoms of CHF. Hyponatremic disorders occur when the normal ratio of solutes to body water content is altered by parallel changes in serum sodium and osmolality. Hyponatremia is generally defined as a serum sodium ion concentration <135 to 136 mmol/L and can be broadly categorized into 2 types, dilutional or depletional. Dilutional hyponatremia is the most common form of hyponatremia and is caused by excess water retention. Depletional hyponatremia is usually hypovolemic, with an absolute deficiency of water but a relative excess of body water compared with sodium concentration.

Diastolic Heart Failure: Definitions and Terminology

Patients with chronic heart failure can be divided into 2 broad categories: systolic heart failure and diastolic heart failure. There are significant differences in demographics, prognosis, left ventricular structure, as well as systolic and diastolic function between these 2 groups of patients. The purpose of this presentation is to define the terminology used to describe these 2 broad categories of heart failure and to characterize the functional measurements that constitute their pathophysiological mechanisms.

Echocardiographic and electrocardiographic findings of cardiomyopathy in Duchenne and Becker-Kiener muscular dystrophies

We assessed the cardiac findings in Duchenne muscular dystrophy (DMD) and Becker-Kiener muscular dystrophy (BMD) patients in the large outpatient group of our single-center institution. The analysis included the revision of patient records (retrospectively) and current echocardiography, electrocardiogram (ECG), and Holter ECG data (prospectively). Reduced left ventricular fraction shortening (FS) < 25% was found in 24% of all patients (50 DMD, 12.1 +/- 4.7 years: 20 BMD, 17.1 +/- 8.5 years). Median age of onset of FS < 25% was 16.8 +/- 1.0 in DMD and 30.4 +/- 3.4 in BMD; (p < 0.05). Holter ECG in DMD demonstrated sinus tachycardia in 26% deprivation of circadian rhythm in 31%, and reduced heart rate variability in 51%. For these reasons, we recommend carrying out echocardiography annually in DMD and BMD > 10 years. Because the rate of disturbances in the cardiac autonomic nervous system is high in DMD, we also recommend Holter ECG annually. Further investigation should be conducted to determine if treatment with ss-blockers and ACE inhibitors in combination reduces cardiac autonomic nervous imbalance, thus improving patient outcome in DMD.

Candesartan Cilexetil

Candesartan cilexetil is the orally administered pro-drug of candesartan, a highly selective antagonist of the angiotensin II subtype 1 receptor that mediates the pressor activities of angiotensin II. Candesartan cilexetil is widely used for the treatment of hypertension and has recently been approved in Europe for the treatment of chronic heart failure (CHF) in patients with impaired left ventricular (LV) systolic function. Results of the CHARM (Candesartan in Heart failure: Assessment of Reduction in Mortality and morbidity) programme suggest that oral candesartan cilexetil reduces morbidity and mortality in patients with CHF and LV ejection fraction (LVEF) < or =40%. There are cardiovascular benefits when candesartan cilexetil is administered as an alternative to an ACE inhibitor, or as an add-on to current treatment regimens that include an ACE inhibitor, in symptomatic CHF. While tolerability is generally good, renal monitoring is required. The recent approval of candesartan cilexetil as both add-on and alternative therapy to ACE inhibitors in patients with CHF and impaired LV systolic function recognises the cardiovascular benefits of candesartan cilexetil in both types of treatment regimens.

Murine models for the study of congestive heart failure: Implications for understanding molecular mechanisms and for drug discovery

Congestive heart failure (CHF) is a complex illness of diverse aetiology. Despite the current multiple therapies, the prognosis for CHF patients remains poor, and new therapeutic targets need to be identified. With the advent of the genetic era, the mouse has become an increasingly valuable animal species in experimental CHF research. A large number of murine models of cardiac hypertrophy and CHF have been created by genetic engineering. Meanwhile, traditional CHF models created by coronary artery ligation, cardiac pressure, or volume overload have been adapted to mice. The present review categorizes and highlights the value of these murine models of cardiac hypertrophy and CHF. These models, combined with sophisticated physiological measurements of cardiac haemodynamics, are expected to yield more and valuable information regarding the molecular mechanisms of CHF and aid in the discovery of novel therapeutic targets.

The procyanidin-induced pseudo laminar shear stress response: a new concept for the reversal of endothelial dysfunction

Reduced endothelium-dependent vasodilator responses with increased synthesis of ET-1 (endothelin-1) are characteristics of endothelial dysfunction in heart failure and are predictive of mortality. Identification of treatments that correct these abnormalities may have particular benefit for patients who become refractory to current regimens. Hawthorn preparations have a long history in the treatment of heart failure. Therefore we tested their inhibitory effects on ET-1 synthesis by cultured endothelial cells. These actions were compared with that of GSE (grape seed extract), as the vasoactive components of both these herbal remedies are mainly oligomeric flavan-3-ols called procyanidins. This showed extracts of hawthorn and grape seed were equipotent as inhibitors of ET-1 synthesis. GSE also produced a potent endothelium-dependent vasodilator response on preparations of isolated aorta. Suppression of ET-1 synthesis at the same time as induction of endothelium-dependent vasodilation is a similar response to that triggered by laminar shear stress. Based on these results and previous findings, we hypothesize that through their pharmacological properties procyanidins stimulate a pseudo laminar shear stress response in endothelial cells, which helps restore endothelial function and underlies the benefit from treatment with hawthorn extract in heart failure.