Towards a re-definition of 'cardiac hypertrophy' through a rational characterization of left ventricular phenotypes: a position paper of the Working Group 'Myocardial Function' of the ESC

Mechanisms of myocardial reverse remodelling and its clinical significance: A scientific statement of the ESC Working Group on Myocardial Function

Cardiovascular disease (CVD) is the leading cause of morbimortality in Europe and worldwide. CVD imposes a heterogeneous spectrum of cardiac remodelling, depending on the insult nature, that is, pressure or volume overload, ischaemia, arrhythmias, infection, pathogenic gene variant, or cardiotoxicity. Moreover, the progression of CVD-induced remodelling is influenced by sex, age, genetic background and comorbidities, impacting patients' outcomes and prognosis. Cardiac reverse remodelling (RR) is defined as any normative improvement in cardiac geometry and function, driven by therapeutic interventions and rarely occurring spontaneously. While RR is the outcome desired for most CVD treatments, they often only slow/halt its progression or modify risk factors, calling for novel and more timely RR approaches. Interventions triggering RR depend on the myocardial insult and include drugs (renin-angiotensin-aldosterone system inhibitors, beta-blockers, diuretics and sodium-glucose cotransporter 2 inhibitors), devices (cardiac resynchronization therapy, ventricular assist devices), surgeries (valve replacement, coronary artery bypass graft), or physiological responses (deconditioning, postpartum). Subsequently, cardiac RR is inferred from the degree of normalization of left ventricular mass, ejection fraction and end-diastolic/end-systolic volumes, whose extent often correlates with patients' prognosis. However, strategies aimed at achieving sustained cardiac improvement, predictive models assessing the extent of RR, or even clinical endpoints that allow for distinguishing complete from incomplete RR or adverse remodelling objectively, remain limited and controversial. This scientific statement aims to define RR, clarify its underlying (patho)physiologic mechanisms and address (non)pharmacological options and promising strategies to promote RR, focusing on the left heart. We highlight the predictors of the extent of RR and review the prognostic significance/impact of incomplete RR/adverse remodelling. Lastly, we present an overview of RR animal models and potential future strategies under pre-clinical evaluation.

Injection of Matrix Metalloproteinase-9 Leads to Ventricular Remodeling

OBJECTIVE

Previous studies have found that some ventricular remodeling is accompanied by increased matrix metalloproteinase-9 (MMP-9) in vivo, and MMP-9 inhibitors can reduce ventricular remodeling. However, there is still no direct evidence that MMP-9 causes ventricular remodeling. In this study, MMP-9 was injected into rats to observe whether MMP-9 caused ventricular remodeling, thereby providing direct evidence of MMP-9-induced ventricular remodeling.

METHODS

Forty-eight eight-week-old male Wistar rats were randomly divided, by weight, into control, low-, medium-, and high-dose MMP-9 groups and were administered normal saline or recombinant rat MMP-9 0.7, 1.4, or 2.1 ng/g, respectively, via intraperitoneal injection, twice per week. On the 28th day, six rats were randomly selected from each group (Stage I). The remaining rats continued receiving injections until the 56th day (Stage II). Echocardiography was performed to observe cardiac structure and function, and the left ventricular mass index (LVWI) was calculated. Myocardial pathological changes and the collagen volume fraction (CVF) were observed by HE and VG staining in myocardial tissue. MMP-9 levels in serum were tested using ELISA. Myocardial MMP-9 levels were measured using Western blots, and the myocardial expression levels of MMP-9 mRNA were assessed using RT-PCR.

RESULTS

During Stage I, serum MMP-9 and myocardial MMP-9 mRNA levels are increased; hypertrophic cardiomyocytes, disorderly arrangement of fibers, and endochylema dissolution are observed in the medium- and high-dose groups. The left ventricular weight index (LVWI) and myocardial MMP-9 increased, and the collagen volume fraction (CVF) reduced in the high-dose group. In Stage II, the left ventricular end-diastolic volume (LVEDV) and diameter (LVIDd) are higher, and CVF decreased in the medium- and high-dose groups. Myocardial pathological lesions intensified. Serum MMP-9 in the model groups and myocardial MMP-9 in the medium- and high-dose groups are increased.

CONCLUSIONS

Injection of MMP-9 can lead to ventricular remodeling.

Cholinergic Elicitation Prevents Ventricular Remodeling via Alleviations of Myocardial Mitochondrial Injury Linked to Inflammation in Ischemia-Induced Chronic Heart Failure Rats

Background

Cholinergic anti-inflammatory pathway (CAP) is implicated in cardioprotection in chronic heart failure (CHF) by downregulating inflammation response. Mitochondrial injuries play an important role in ventricular remodeling of the CHF process. Herein, we aim to investigate whether CAP elicitation prevents ventricular remodeling in CHF by protecting myocardial mitochondrial injuries and its underlying mechanisms.

Methods and Results

CHF models were established by ligation of anterior descending artery for 5 weeks. Postoperative survival rats were assigned into 5 groups: the sham group (sham, n = 10), CHF group (CHF, n = 11), Vag group (CHF+vagotomy, n = 10), PNU group (CHF+PNU-282987 for 4 weeks, n = 11), and Vag+PNU group (CHF+vagotomy+PNU-282987 for 4 weeks, n = 10). The antiventricular remodeling effect of cholinergic elicitation was evaluated in vivo, and H9C2 cells were selected for the TNF-α gradient stimulation experiment in vitro. In vivo, CAP agitated by PNU-282987 alleviated the left ventricular dysfunction and inhibited the energy metabolism remodeling. Further, cholinergic elicitation increased myocardium ATP levels and reduced systemic inflammation. CAP induction alleviates macrophage infiltration and cardiac fibrosis, of which the effect is counteracted by vagotomy. Myocardial mitochondrial injuries were ameliorated by CAP activation, including the reserved ultrastructural integrity, declining ROS overload, reduced myocardial apoptosis, and enhanced mitochondrial fusion. In vitro, TNF-α intervention significantly exacerbated the mitochondrial damage in H9C2 cells.

Conclusion

CAP elicitation effectively improves ischemic ventricular remodeling by suppressing systemic and cardiac inflammatory response, attenuating cardiac fibrosis and potentially alleviating the mitochondrial dysfunction linked to hyperinflammation reaction.

Inhibition of aquaporin-1 prevents myocardial remodeling by blocking the transmembrane transport of hydrogen peroxide

Pathological remodeling of the myocardium has long been known to involve oxidant signaling, but strategies using systemic antioxidants have generally failed to prevent it. We sought to identify key regulators of oxidant-mediated cardiac hypertrophy amenable to targeted pharmacological therapy. Specific isoforms of the aquaporin water channels have been implicated in oxidant sensing, but their role in heart muscle is unknown. RNA sequencing from human cardiac myocytes revealed that the archetypal AQP1 is a major isoform. AQP1 expression correlates with the severity of hypertrophic remodeling in patients with aortic stenosis. The AQP1 channel was detected at the plasma membrane of human and mouse cardiac myocytes from hypertrophic hearts, where it colocalized with NADPH oxidase-2 and caveolin-3. We show that hydrogen peroxide (H₂O₂), produced extracellularly, is necessary for the hypertrophic response of isolated cardiac myocytes and that AQP1 facilitates the transmembrane transport of H₂O₂ through its water pore, resulting in activation of oxidant-sensitive kinases in cardiac myocytes. Structural analysis of the amino acid residues lining the water pore of AQP1 supports its permeation by H₂O₂ Deletion of Aqp1 or selective blockade of the AQP1 intrasubunit pore inhibited H₂O₂ transport in mouse and human cells and rescued the myocyte hypertrophy in human induced pluripotent stem cell-derived engineered heart muscle. Treatment of mice with a clinically approved AQP1 inhibitor, Bacopaside, attenuated cardiac hypertrophy. We conclude that cardiac hypertrophy is mediated by the transmembrane transport of H₂O₂ by the water channel AQP1 and that inhibitors of AQP1 represent new possibilities for treating hypertrophic cardiomyopathies.

Challenges and opportunities in improving left ventricular remodelling and clinical outcome following surgical and trans-catheter aortic valve replacement

Over the last half century, surgical aortic valve replacement (SAVR) has evolved to offer a durable and efficient valve haemodynamically, with low procedural complications that allows favourable remodelling of left ventricular (LV) structure and function. The latter has become more challenging among elderly patients, particularly following trans-catheter aortic valve implantation (TAVI). Precise understanding of myocardial adaptation to pressure and volume overloading and its responses to valve surgery requires comprehensive assessments from aortic valve energy loss, valvular-vascular impedance to myocardial activation, force-velocity relationship, and myocardial strain. LV hypertrophy and myocardial fibrosis remains as the structural and morphological focus in this endeavour. Early intervention in asymptomatic aortic stenosis or regurgitation along with individualised management of hypertension and atrial fibrillation is likely to improve patient outcome. Physiological pacing via the His-Purkinje system for conduction abnormalities, further reduction in para-valvular aortic regurgitation along with therapy of angiotensin receptor blockade will improve patient outcome by facilitating hypertrophy regression, LV coordinate contraction, and global vascular function. TAVI leaflet thromboses require anticoagulation while impaired access to coronary ostia risks future TAVI-in-TAVI or coronary interventions. Until comparable long-term durability and the resolution of TAVI related complications become available, SAVR remains the first choice for lower risk younger patients.

Cell shape: effects on gene expression and signaling

The perception of biophysical forces (mechanosensation) and their conversion into chemical signals (mechanotransduction) are fundamental biological processes. They are connected to hypertrophic and atrophic cellular responses, and defects in these processes have been linked to various diseases, especially in the cardiovascular system. Although cardiomyocytes generate, and are exposed to, considerable hemodynamic forces that affect their shapes, until recently, we did not know whether cell shape affects gene expression. However, new single-cell trapping strategies, followed by single-cell RNA sequencing, to profile the transcriptomes of individual cardiomyocytes of defined geometrical morphotypes have been developed that are characteristic for either normal or pathological (afterload or preload) conditions. This paper reviews the recent literature with regard to cell shape and the transcriptome and provides an overview of this newly emerging field, which has far-reaching implications for both biology, disease, and possibly therapy.

Towards standardization of echocardiography for the evaluation of left ventricular function in adult rodents: a position paper of the ESC Working Group on Myocardial Function

Echocardiography is a reliable and reproducible method to assess non-invasively cardiac function in clinical and experimental research. Significant progress in the development of echocardiographic equipment and transducers has led to the successful translation of this methodology from humans to rodents, allowing for the scoring of disease severity and progression, testing of new drugs, and monitoring cardiac function in genetically modified or pharmacologically treated animals. However, as yet, there is no standardization in the procedure to acquire echocardiographic measurements in small animals. This position paper focuses on the appropriate acquisition and analysis of echocardiographic parameters in adult mice and rats, and provides reference values, representative images, and videos for the accurate and reproducible quantification of left ventricular function in healthy and pathological conditions.

MicroRNAs in cardiovascular disease

Cardiovascular disease (CVD) remains the predominant cause of human morbidity and mortality in developed countries. Currently, microRNAs have been investigated in many diseases as well-promising biomarkers for diagnosis, prognosis, and disease monitoring. Plenty studies have been designed so as to elucidate the properties of microRNAs in the classification and risk stratification of patients with CVD and also to evaluate their potentials in individualized management and guide treatment decisions. Therefore, in this review article, we aimed to present the most recent data concerning the role of microRNAs as potential novel biomarkers for cardiovascular disease.

Cell shape determines gene expression: cardiomyocyte morphotypic transcriptomes

Cardiomyocytes undergo considerable changes in cell shape. These can be due to hemodynamic constraints, including changes in preload and afterload conditions, or to mutations in genes important for cardiac function. These changes instigate significant changes in cellular architecture and lead to the addition of sarcomeres, at the same time or at a later stage. However, it is currently unknown whether changes in cell shape on their own affect gene expression and the aim of this study was to fill that gap in our knowledge. We developed a single-cell morphotyping strategy, followed by single-cell RNA sequencing, to determine the effects of altered cell shape in gene expression. This enabled us to profile the transcriptomes of individual cardiomyocytes of defined geometrical morphotypes and characterize them as either normal or pathological conditions. We observed that deviations from normal cell shapes were associated with significant downregulation of gene expression and deactivation of specific pathways, like oxidative phosphorylation, protein kinase A, and cardiac beta-adrenergic signaling pathways. In addition, we observed that genes involved in apoptosis of cardiomyocytes and necrosis were upregulated in square-like pathological shapes. Mechano-sensory pathways, including integrin and Src kinase mediated signaling, appear to be involved in the regulation of shape-dependent gene expression. Our study demonstrates that cell shape per se affects the regulation of the transcriptome in cardiac myocytes, an effect with possible implications for cardiovascular disease.

Prevalence and Clinical Correlates of Left Ventricular Hypertrophy in Black Africans

INTRODUCTION

African-Americans present higher prevalence of left ventricular hypertrophy (LVH) when compared with white populations. However, there is a lack of information about the prevalence and determinants of LVH in black individuals living in Africa.

METHODS

A cross-sectional study was performed with a non-probabilistic sample comprised of 609 University workers from Angola/Africa, describing the prevalence of LVH and the determinants of left ventricular mass. Echocardiographic measurements were performed and left ventricular mass was indexed to body surface area. Systolic and diastolic blood pressures were measured, along with anthropometric and clinical variables.

RESULTS

Chamber diameter and wall thickness were higher in men compared to women. Additionally, LVM was higher in men (114.2 ± 36 vs 98.4 ± 31.9, P < 0.001), and the overall prevalence of LVH in black Angolans was 41.1%, which tended to be higher in women (44.5 vs 37.4%, P = 0.096). In men, systolic blood pressure and BMI were independently associated with LVM, while age, systolic blood pressure and waist circumference were associated with LVM in women.

CONCLUSIONS

In summary, blood pressure levels were the main determinants of LVH in black Africans, although different anthropometric variables showed mild influence in LVM. Our data suggests that LVH prevalence and determinants in black Africans are similar to that reported for African-Americans.

Left ventricular hypertrophy and proteinuria in patients with essential hypertension in Andkhoy, Afghanistan

Left ventricular hypertrophy (LVH) and proteinuria are known as independent predictors of cardiovascular death in hypertension. However, LVH and its association with proteinuria have not been investigated in adult hypertensive patients in Afghanistan. The objective of this research was to determine the prevalence of LVH and the correlation between LVH and proteinuria among the Afghan adult hypertensive population visiting an outpatient clinic in Afghanistan. We retrospectively evaluated 789 hypertensive patients (mean age is 56 years and 46% were men) who visited the clinic between December 2014 and August 2016. Patient characteristics and laboratory and clinical findings were recorded. The rate of LVH among hypertensive patients was 54.4%. Patients with proteinuria had a significantly higher LVH percentage compared to those without proteinuria (73.2% versus 55.8%; P<0.001). There was a significant correlation between LVH and proteinuria among hypertensive patients (r=0.182, P<0.001). Based on a multivariate regression analysis, age (odds ratio [OR], 1.04; 95% confidence interval [CI], 1.02-1.05), proteinuria (OR, 1.69; 95% CI, 1.19-2.41), and female sex (OR, 0.09; 95% CI, 0.06-0.13) were significant factors. In conclusion, the prevalence of LVH was more than 50% in the Afghan adult hypertensive population. This study indicates that there is a significant relationship between LVH detected by ECG and the presence of proteinuria among such subjects.

The influence of heart failure co-morbidity on high-sensitivity troponin T levels in COPD exacerbation in a prospective cohort study: data from the Akershus cardiac examination (ACE) 2 study

CONTEXT

Troponin (hs-TnT) levels predict mortality after acute exacerbation of COPD (AECOPD). Whether this is independent of heart failure (HF) is not established.

MATERIAL AND METHODS

Prospectively included AECOPD patients adjudicated for acute HF categorized into three groups: (A) AECOPD, but acute HF the primary cause for hospitalization; (B) AECOPD the primary cause, but co-existing myocardial dysfunction and (C) AECOPD without myocardial dysfunction.

RESULTS

About 103 AECOPD patients; 18% A, 27% B and 54% C. Hs-TnT level differed between the groups: (ng/l, median) A: 41, B: 25 and C: 15, p = 0.03 for A versus B and p = 0.005 for B versus C. During a median 826 days, 47% died. In Cox analysis, hs-TnT levels remained associated with mortality (hazard ratio per 10 ng/l 1.3, p < 0.0001).

CONCLUSION

hs-TnT levels are influenced by myocardial dysfunction/HF in AECOPD, but provide independent prognostic information. The prognostic merit of hs-TnT cannot be attributed to HF alone.

Precursors of Hypertensive Heart Phenotype Develop in Healthy Adults: A High-Resolution 3D MRI Study

OBJECTIVES

This study used high-resolution 3-dimensional cardiac magnetic resonance to define the anatomical and functional left ventricular (LV) properties associated with increasing systolic blood pressure (SBP) in a drug-naïve cohort.

BACKGROUND

LV hypertrophy and remodeling occur in response to hemodynamic stress but little is known about how these phenotypic changes are initiated in the general population.

METHODS

In this study, 1,258 volunteers (54% women, mean age 40.6 ± 12.8 years) without self-reported cardiovascular disease underwent 3-dimensional cardiac magnetic resonance combined with computational modeling. The relationship between SBP and wall thickness (WT), relative WT, end-systolic wall stress (WS), and fractional wall thickening were analyzed using 3-dimensional regression models adjusted for body surface area, sex, race, age, and multiple testing. Significantly associated points in the LV model (p < 0.05) were identified and the relationship with SBP reported as mean β coefficients.

RESULTS

There was a continuous relationship between SBP and asymmetric concentric hypertrophic adaptation of the septum and anterior wall that was associated with normalization of wall stress. In the lateral wall an increase in wall stress with rising SBP was not balanced by a commensurate hypertrophic relationship. In normotensives, SBP was positively associated with WT (β = 0.09) and relative WT (β = 0.07) in the septal and anterior walls, and this regional hypertrophic relationship was progressively stronger among pre-hypertensives (β = 0.10) and hypertensives (β = 0.30).

CONCLUSIONS

These findings show that the precursors of the hypertensive heart phenotype can be traced to healthy normotensive adults and that an independent and continuous relationship exists between adverse LV remodeling and SBP in a low-risk population. These adaptations show distinct regional variations with concentric hypertrophy of the septum and eccentric hypertrophy of the lateral wall, which challenge conventional classifications of LV remodeling.

ZBTB17 (MIZ1) Is Important for the Cardiac Stress Response and a Novel Candidate Gene for Cardiomyopathy and Heart Failure

BACKGROUND

Mutations in sarcomeric and cytoskeletal proteins are a major cause of hereditary cardiomyopathies, but our knowledge remains incomplete as to how the genetic defects execute their effects.

METHODS AND RESULTS

We used cysteine and glycine-rich protein 3, a known cardiomyopathy gene, in a yeast 2-hybrid screen and identified zinc-finger and BTB domain-containing protein 17 (ZBTB17) as a novel interacting partner. ZBTB17 is a transcription factor that contains the peak association signal (rs10927875) at the replicated 1p36 cardiomyopathy locus. ZBTB17 expression protected cardiac myocytes from apoptosis in vitro and in a mouse model with cardiac myocyte-specific deletion of Zbtb17, which develops cardiomyopathy and fibrosis after biomechanical stress. ZBTB17 also regulated cardiac myocyte hypertrophy in vitro and in vivo in a calcineurin-dependent manner.

CONCLUSIONS

We revealed new functions for ZBTB17 in the heart, a transcription factor that may play a role as a novel cardiomyopathy gene.

Targeting the CaMKII/ERK Interaction in the Heart Prevents Cardiac Hypertrophy

Aims

Activation of Ca²⁺/Calmodulin protein kinase II (CaMKII) is an important step in signaling of cardiac hypertrophy. The molecular mechanisms by which CaMKII integrates with other pathways in the heart are incompletely understood. We hypothesize that CaMKII association with extracellular regulated kinase (ERK), promotes cardiac hypertrophy through ERK nuclear localization.

Methods and Results

In H9C2 cardiomyoblasts, the selective CaMKII peptide inhibitor AntCaNtide, its penetratin conjugated minimal inhibitory sequence analog tat-CN17β, and the MEK/ERK inhibitor UO126 all reduce phenylephrine (PE)-mediated ERK and CaMKII activation and their interaction. Moreover, AntCaNtide or tat-CN17β pretreatment prevented PE induced CaMKII and ERK nuclear accumulation in H9C2s and reduced the hypertrophy responses. To determine the role of CaMKII in cardiac hypertrophy in vivo, spontaneously hypertensive rats were subjected to intramyocardial injections of AntCaNtide or tat-CN17β. Left ventricular hypertrophy was evaluated weekly for 3 weeks by cardiac ultrasounds. We observed that the treatment with CaMKII inhibitors induced similar but significant reduction of cardiac size, left ventricular mass, and thickness of cardiac wall. The treatment with CaMKII inhibitors caused a significant reduction of CaMKII and ERK phosphorylation levels and their nuclear localization in the heart.

Conclusion

These results indicate that CaMKII and ERK interact to promote activation in hypertrophy; the inhibition of CaMKII-ERK interaction offers a novel therapeutic approach to limit cardiac hypertrophy.

Application of microRNAs in diagnosis and treatment of cardiovascular disease

Cardiovascular disease (CVD) is a major cause of morbidity and mortality worldwide. Innovative, more stringent diagnostic and prognostic biomarkers and effective treatment options are needed to lessen its burden. In recent years, microRNAs have emerged as master regulators of gene expression - they bind to complementary sequences within the mRNAs of their target genes and inhibit their expression by either mRNA degradation or translational repression. microRNAs have been implicated in all major cellular processes, including cell cycle, differentiation and metabolism. Their unique mode of action, fine-tuning gene expression rather than turning genes on/off, and their ability to simultaneously regulate multiple elements of relevant pathways makes them enticing potential biomarkers and therapeutic targets. Indeed, cardiovascular patients have specific patterns of circulating microRNA levels, often early in the disease process. This article provides a systematic overview of the role of microRNAs in the pathophysiology, diagnosis and treatment of CVD.

A role for membrane shape and information processing in cardiac physiology

While the heart is a dynamic organ and one of its major functions is to provide the organism with sufficient blood supply, the regulatory feedback systems, which allow adaptation to hemodynamic changes, remain not well understood. Our current description of mechanosensation focuses on stretch-sensitive ion channels, cytoskeletal components, structures such as the sarcomeric Z-disc, costameres, caveolae, or the concept of tensegrity, but these models appear incomplete as the remarkable plasticity of the myocardium in response to biomechanical stress and heart rate variations remains unexplained. Signaling activity at membranes depends on their geometric parameters such as surface area and curvature, which links shape to information processing. In the heart, continuous cycles of contraction and relaxation reshape membrane morphology and hence affect cardio-mechanic signaling. This article provides a brief review on current models of mechanosensation and focuses on how signaling, cardiac myocyte dynamics, and membrane shape interact and potentially give rise to a self-organized system that uses shape to sense the extra- and intracellular environment. This novel concept may help to explain how changes in frequency, and thus membrane shape, affect cardiac plasticity. One of the conclusions is that hypertrophy and associated fibrosis, which have been considered as necessary to cope with increased wall stress, can also be seen as part of complex feedback systems which use local membrane inhomogeneity in different cardiac cell types to influence whole organphysiology and which are predicted to fine-tune and thus regulate membrane-mediated signaling.

Cardiovascular remodelling in coronary artery disease and heart failure

Remodelling is a response of the myocardium and vasculature to a range of potentially noxious haemodynamic, metabolic, and inflammatory stimuli. Remodelling is initially functional, compensatory, and adaptive but, when sustained, progresses to structural changes that become self-perpetuating and pathogenic. Remodelling involves responses not only of the cardiomyocytes, endothelium, and vascular smooth muscle cells, but also of interstitial cells and matrix. In this Review we characterise the remodelling processes in atherosclerosis, vascular and myocardial ischaemia-reperfusion injury, and heart failure, and we draw attention to potential avenues for innovative therapeutic approaches, including conditioning and metabolic strategies.

Mechano-signaling in heart failure

Mechanosensation and mechanotransduction are fundamental aspects of biology, but the link between physical stimuli and biological responses remains not well understood. The perception of mechanical stimuli, their conversion into biochemical signals, and the transmission of these signals are particularly important for dynamic organs such as the heart. Various concepts have been introduced to explain mechanosensation at the molecular level, including effects on signalosomes, tensegrity, or direct activation (or inactivation) of enzymes. Striated muscles, including cardiac myocytes, differ from other cells in that they contain sarcomeres which are essential for the generation of forces and which play additional roles in mechanosensation. The majority of cardiomyopathy causing candidate genes encode structural proteins among which titin probably is the most important one. Due to its elastic elements, titin is a length sensor and also plays a role as a tension sensor (i.e., stress sensation). The recent discovery of titin mutations being a major cause of dilated cardiomyopathy (DCM) also underpins the importance of mechanosensation and mechanotransduction in the pathogenesis of heart failure. Here, we focus on sarcomere-related mechanisms, discuss recent findings, and provide a link to cardiomyopathy and associated heart failure.

Left ventricular hypertrophy among black hypertensive patients: focusing on the efficacy of angiotensin converting enzyme inhibitors

Background

Left ventricular hypertrophy (LVH) is an independent cardiovascular risk factor in patients with essential hypertension. The main objective of this study was to assess the echocardiographic prevalence of left ventricular hypertrophy in patients with hypertension, its risk factors and effect of antihypertensive drugs on its prevalence.

Methods

A hospital based cross sectional study was conducted on 200 hypertensive patients on treatment in southwest Ethiopia. A pretested structured questionnaire was used to collect data from participants and their clinical records. Blood pressure and anthropometric measurements were taken according to recommended standards. Left ventricular mass was measured by transthoracic echocardiography. Associations between categorical variables were assessed using chi-square test and odds ratio with 95% confidence interval. Logistic regression model was done to identify risks factors of LVH. P values of < 0.05 were considered as statistically significant.

Results

The mean age, systolic blood pressure, diastolic blood pressure and body mass index were 55.7 ± 11.3 years, 139.2 ± 7.7 mmHg, 89.2 ± 5.7 mmHg and 24.2 ± 3.4 Kg/m² respectively. The overall prevalence of LVH among these study subjects was 52%. Age ≥50 years (OR: 3.49, 95% CI 1.33-9.14, P = 0.011), female gender (OR: 7.69, 95% CI 3.23-20.0, P < 0.001), systolic blood pressure ≥140 mmHg (OR: 2.85, 95% CI 1.27-6.41, P = 0.011), and duration of hypertension (OR: 3.59, 95% CI 1.47-8.76, P = 0.005) were independent predictors of left ventricular hypertrophy. Angiotensin converting enzyme (ACE) inhibitors were the only antihypertensive drugs associated with lower risk of left ventricular hypertrophy (OR: 0.08, 95% CI 0.03-0.19, p < 0.001).

Conclusions

Left ventricular hypertrophy was found to be highly prevalent in hypertensive patients in Ethiopia. ACE inhibitors were the only antihypertensive drugs associated with reduced risk of LVH. We thus recommend strategies to early detect and treat hypertension and to timely screen for LVH among patients with hypertension. Multicenter prospective studies in Africa settings would be ideal to identify the best antihypertensive agents in black Africans.

An animal model of stress-induced cardiomyopathy utilizing the social defeat paradigm

Stress-induced cardiomyopathy (SIC) is a form of acute heart disease triggered by extreme psychological stress. In patients who develop SIC, the outward symptoms are almost indistinguishable from acute myocardial infarction (AMI). However, some important criteria differentiate patients with SIC from those with AMI. Patients with SIC: (1) experience some form of extreme psychological stress from minutes to hours before developing heart disease, (2) do not suffer from atherosclerosis or coronary artery obstruction, and 3) exhibit abnormal ballooning of the left ventricle. In the present study, the resident-intruder (RI) social defeat test was investigated as a potential rat model for stressed-induced cardiomyopathy. Adult Long-Evans rats were implanted with a biotelemetry transmitter for ECG recordings and habituated for two weeks. An intruder rat was placed in the cage of a resident rat behind a wire-mesh partition for 5 min. The partition was then removed for 5 min to allow direct contact between the intruder and resident rats. After this interval, the wire-mesh partition was replaced and the intruder rat remained behind the partition for an additional 50 min. Behavioral responses were noted and ECG recordings were collected during the entire 60-min testing period. Upon completion of the test, the intruder rat was removed from the cage of the resident rat and sacrificed. The heart was examined and blood was collected. Heart weight/body weight ratio, left ventricle/body weight ratio, heart length, plasma corticosterone levels, and plasma troponin I levels of intruder rats were significantly higher as compared to control rats. Intruder rats significantly increased their heart rate during the first 5 min of the RI test. It is concluded that the RI test to induce social defeat is a novel rodent paradigm for modeling stress-induced cardiomyopathy in the human.

Addressing the relationship between cardiac hypertrophy and ischaemic stroke: an observational study

INTRODUCTION

Research over the last decade has recognized left ventricular hypertrophy as a risk factor for major cardiovascular events including stroke. While cardiac magnetic resonance imaging is the best modality to quantify left ventricular hypertrophy, echocardiographic calculation of left ventricular mass index is a reasonable alternative.

METHODS

We carried out a hospital based prospective study to identify the prevalence of left ventricular hypertrophy, assessed using echocardiography, in patients presenting with ischaemic strokes. This is the first study that attempted to quantify this issue in a cohort of Sri Lankan patients. The study was carried out in the National Hospital of Sri Lanka over a period of 6 months.

RESULTS

A total of 55 patients (44 males, 80%) (mean age: 62.3, range: 48-82 years) with ischaemic strokes were studied. Of them, only 38 could be mobilized to measure the height and weight to calculate the left ventricular mass index. Of the rest, only one person had the electrocardiographic criteria for left ventricular hypertrophy. Of the 38 patients evaluated, 29 (76.3%) had left ventricular hypertrophy while 19 (50%) had severe hypertrophy.

DISCUSSION AND CONCLUSIONS

The rates of left ventricular hypertrophy reported in similar studies in other countries vary between 25-62%. Given the high prevalence of left ventricular hypertrophy reported in this study and its recognition as a risk factor for stroke recently, together with the availability of effective treatment for risk reduction, the cost effectiveness of population screening should be evaluated. Further studies are planned in this regard.

High prevalence of myocarditis in patients with hypertensive heart disease and cardiac deterioration

AIMS

Structural abnormalities causing cardiac deterioration in hypertensive heart disease (HHD) are poorly understood. The aim of the study was to evaluate left ventricular (LV) myocardial changes in patients with HHD and cardiac failure.

METHODS AND RESULTS

Among 1229 patients undergoing an LV or biventricular endomyocardial biopsy because of unexplained LV dysfunction from 2000 to 2010, 45 had HHD. The HHD population had non-invasive assessment of cardiac wall thickness, diameters, and function; endomyocardial samples were processed for histology, immunohistochemistry, and polymerase chain reaction (PCR) for cardiotropic viruses. Mean LV end-diastolic diameter was 63.3 ± 5.9 mm, LV ejection fraction 29.7 ± 7.6%, and maximal wall thickness 12.8 ± 0.9 mm. At histology, hypertrophy with degeneration of cardiomyocytes, increased external/lumen ratio of intramural arterioles, and myocardial fibrosis were observed in 17 patients (38%). In the remaining 28 patients (62%), these histological changes were associated with myocarditis. Myocarditis was present in 40.4% of the cohort without HHD. PCR was negative in HHD without inflammation while it was positive in 10 subjects with myocarditis (enterovirus in 3 cases, adenovirus 4, influenza virus 3). Addition of immunosuppression to supportive therapy in the 18 virus-negative myocarditis subjects was followed at 6 months by significant recovery of LV function in 15 (83%; ejection fraction from 25.3 ± 9.3% to 49.5 ± 9.8%) while LV function improved to a minor extent ( ejection fraction from 25 ± 5.1% to 36 ± 4.4%) in 12 of 27 patients (44%) on supportive treatment alone.

CONCLUSION

Myocarditis is a major cause of cardiac deterioration in patients with HHD; its recognition may improve patient treatment and outcome.

CaMK4 Gene Deletion Induces Hypertension

Background

The expression of calcium/calmodulin-dependent kinase IV (CaMKIV) was hitherto thought to be confined to the nervous system. However, a recent genome-wide analysis indicated an association between hypertension and a single-nucleotide polymorphism (rs10491334) of the human CaMKIV gene (CaMK4), which suggests a role for this kinase in the regulation of vascular tone.

Methods and Results

To directly assess the role of CaMKIV in hypertension, we characterized the cardiovascular phenotype of CaMK4^−/− mice. They displayed a typical hypertensive phenotype, including high blood pressure levels, cardiac hypertrophy, vascular and kidney damage, and reduced tolerance to chronic ischemia and myocardial infarction compared with wild-type littermates. Interestingly, in vitro experiments showed the ability of this kinase to activate endothelial nitric oxide synthase. Eventually, in a population study, we found that the rs10491334 variant associates with a reduction in the expression levels of CaMKIV in lymphocytes from hypertensive patients.

Conclusions

Taken together, our results provide evidence that CaMKIV plays a pivotal role in blood pressure regulation through the control of endothelial nitric oxide synthase activity. (J Am Heart Assoc. 2012;1:e001081 doi: 10.1161/JAHA.112.001081.)

Age-dependent changes in contractile function and passive elastic properties of myocardium from mice lacking muscle LIM protein (MLP)

AIMS

Muscle LIM protein (MLP) null mice are often used as a model for human dilated cardiomyopathy. So far, little is known about the time course and pathomechanisms leading to the development of the adult phenotype.

METHODS AND RESULTS

We systematically analysed the contractile phenotype, myofilament calcium (Ca(2)(+)) responsiveness, passive myocardial mechanics, histology, and mRNA expression in mice aged 4 and 12 weeks. In 4-week-old animals, there was no significant difference in the force-frequency relationship (FFR) and catecholamine response of intact isolated papillary muscles between wild-type (WT) and MLP null myocardium. In 12-week-old animals, WT myocardium exhibited a significantly positive FFR, while that of MLP null mice was significantly negative, and the inotropic response to catecholamines was significantly reduced in MLP null mice. This time course of decline in contractile function was confirmed in vivo by echocardiography. Whereas at 4 weeks of age MLP null mice and WT littermates showed similar levels of SERCA2a (sarcoplasmic reticulum Ca(2+) ATPase) expression, the expression was significantly lower in 12-week-old MLP null mice compared with littermate controls. Myofilament Ca(2)(+) responsiveness was not affected by the lack of MLP, irrespective of age. Whereas in 4-week-old animals MLP null myocardium showed a trend to an increased compliance compared with the WT, myocardium of 12-week-old MLP null mice was significantly less compliant than WT myocardium. Parallel to the decrease in compliance there was an increase in fibrosis in the MLP null animals.

CONCLUSION

Our data suggest that MLP deficiency does not primarily influence myocardial contractility. A lack of MLP leads to an age-dependent impairment of excitation-contraction coupling with resulting contractile dysfunction and secondary fibrosis.

Nitric oxide synthase in post-ischaemic remodelling: new pathways and mechanisms

The three isoforms of nitric oxide synthase (NOS), spatially confined in specific intracellular compartments in cardiac cells, have distinct roles in the regulation of contractility in pathophysiological situations. Recently, evidence has emerged that implicates NOS in modulating myocardial remodelling during cardiac stress, including after ischaemic insults. As long as they remain in a coupled state the NOS mostly attenuate hypertrophic remodelling through both cGMP-dependent and independent mechanisms. We review the evidence provided from the phenotype of genetic mouse models as well as from in vitro cell experiments dissecting the signalling effectors involved in the NOS-mediated regulation that justify new therapeutic interventions on the NOS-cGMP axis to attenuate the development of heart failure.

Myosin binding protein C: implications for signal-transduction

Myosin binding protein C (MYBPC) is a crucial component of the sarcomere and an important regulator of muscle function. While mutations in different myosin binding protein C (MYBPC) genes are well known causes of various human diseases, such as hypertrophic (HCM) and dilated (DCM) forms of cardiomyopathy as well as skeletal muscular disorders, the underlying molecular mechanisms remain not well understood. A variety of MYBPC3 (cardiac isoform) mutations have been studied in great detail and several corresponding genetically altered mouse models have been generated. Most MYBPC3 mutations may cause haploinsufficiency and with it they may cause a primary increase in calcium sensitivity which is potentially able to explain major features observed in HCM patients such as the hypercontractile phenotype and the well known secondary effects such as myofibrillar disarray, fibrosis, myocardial hypertrophy and remodelling including arrhythmogenesis. However the presence of poison peptides in some cases cannot be fully excluded and most probably other mechanisms are also at play. Here we shall discuss MYBPC interacting proteins and possible pathways linked to cardiomyopathy and heart failure.

Left ventricular structural remodeling in health and disease: with special emphasis on volume, mass, and geometry

The changes in left ventricular (LV) structure and geometry that evolve after myocardial injury or overload usually involve chamber dilation and/or hypertrophy. Such architectural remodeling can be classified as eccentric or concentric. Consideration of LV volume, mass, and relative wall thickness (or mass/volume) allows classification of LV remodeling that includes virtually all LV remodeling changes that are seen in health and disease. These various architectural changes generally include the development of LV hypertrophy in a pattern that is closely related to the type of injury or overload, and they are accompanied by differences in cardiac function and hemodynamics. Some patterns of remodeling are associated with adverse outcomes whereas others appear to be adaptive and physiologic without adverse consequences. Considering all patients with LV hypertrophy as a homogenous group is inconsistent with our understanding of the various remodeling patterns that are discussed in this review.

The sarcomeric Z-disc and Z-discopathies

The sarcomeric Z-disc defines the lateral borders of the sarcomere and has primarily been seen as a structure important for mechanical stability. This view has changed dramatically within the last one or two decades. A multitude of novel Z-disc proteins and their interacting partners have been identified, which has led to the identification of additional functions and which have now been assigned to this structure. This includes its importance for intracellular signalling, for mechanosensation and mechanotransduction in particular, an emerging importance for protein turnover and autophagy, as well as its molecular links to the t-tubular system and the sarcoplasmic reticulum. Moreover, the discovery of mutations in a wide variety of Z-disc proteins, which lead to perturbations of several of the above-mentioned systems, gives rise to a diverse group of diseases which can be termed Z-discopathies. This paper provides a brief overview of these novel aspects as well as points to future research directions.