Myocardial interstitial remodelling in non-ischaemic dilated cardiomyopathy: insights from cardiovascular magnetic resonance

Septal Midwall Late Gadolinium Enhancement in Ischemic Cardiomyopathy and Nonischemic Dilated Cardiomyopathy-Characteristics and Prognosis

Septal midwall late gadolinium enhancement (LGE) is a characteristic finding on cardiac magnetic resonance imaging (CMR) in nonischemic dilated cardiomyopathy (DCM) and is associated with adverse events. Its significance in ischemic cardiomyopathy (ICM) is unknown. With this multicenter observational study, we aimed to study the characteristics of septal midwall LGE and evaluate its prognostic value in ICM. A total of 1,084 patients with an impaired left ventricular (LV) ejection fraction (<50%) on LGE-CMR, either because of ICM (53%) or DCM, were included retrospectively. Septal midwall LGE was defined as midmyocardial stripe-like or patchy LGE in septal segments and was present in 10% of patients with ICM compared with 34% of patients with DCM (p <0.001). It was significantly associated with larger LV volumes and lower LV ejection fraction, irrespective of etiology. The primary endpoint was all-cause mortality and secondary endpoint was ventricular arrhythmias (VAs), including resuscitated cardiac arrest, sustained VA, and appropriate implantable cardioverter-defibrillator (ICD) therapy. During a median follow-up of 2.7 years, we found a significant association between septal midwall LGE and mortality in patients with DCM (hazard ratio [HR] 1.92, p = 0.03), but not in patients with ICM (HR 1.35, p = 0.39). Risk of VAs was significantly higher in patients with septal midwall LGE on CMR, both in DCM (HR 2.80, p <0.01) and in ICM (HR 2.70, p <0.01). In conclusion, septal midwall LGE, typically seen in DCM, was also present in 10% of patients with ICM and was associated with increased LV dilation and worse function, irrespective of etiology. When present, septal midwall LGE was associated with adverse outcome.

Role of Imaging in Cardiomyopathies

Imaging has a central role in the diagnosis, classification, and clinical management of cardiomyopathies. While echocardiography is the first-line technique, given its wide availability and safety, advanced imaging, including cardiovascular magnetic resonance (CMR), nuclear medicine and CT, is increasingly needed to refine the diagnosis or guide therapeutic decision-making. In selected cases, such as in transthyretin-related cardiac amyloidosis or in arrhythmogenic cardiomyopathy, the demonstration of histological features of the disease can be avoided when typical findings are observed at bone-tracer scintigraphy or CMR, respectively. Findings from imaging techniques should always be integrated with data from the clinical, electrocardiographic, biomarker, genetic and functional evaluation to pursue an individualised approach to patients with cardiomyopathy.

Histopathological insights into mitral valve prolapse-induced fibrosis

Mitral valve prolapse (MVP) is a cardiac valve disease that not only affects the mitral valve (MV), provoking mitral regurgitation, but also leads to maladaptive structural changes in the heart. Such structural changes include the formation of left ventricular (LV) regionalized fibrosis, especially affecting the papillary muscles and inferobasal LV wall. The occurrence of regional fibrosis in MVP patients is hypothesized to be a consequence of increased mechanical stress on the papillary muscles and surrounding myocardium during systole and altered mitral annular motion. These mechanisms appear to induce fibrosis in valve-linked regions, independent of volume-overload remodeling effects of mitral regurgitation. In clinical practice, quantification of myocardial fibrosis is performed with cardiovascular magnetic resonance (CMR) imaging, even though CMR has sensitivity limitations in detecting myocardial fibrosis, especially in detecting interstitial fibrosis. Regional LV fibrosis is clinically relevant because even in the absence of mitral regurgitation, it has been associated with ventricular arrhythmias and sudden cardiac death in MVP patients. Myocardial fibrosis may also be associated with LV dysfunction following MV surgery. The current article provides an overview of current histopathological studies investigating LV fibrosis and remodeling in MVP patients. In addition, we elucidate the ability of histopathological studies to quantify fibrotic remodeling in MVP and gain deeper understanding of the pathophysiological processes. Furthermore, molecular changes such as alterations in collagen expression in MVP patients are reviewed.

Heart failure with recovered ejection fraction: Current understanding and future prospects

Heart failure with reduced ejection fraction (HFrEF) is a prevalent kind of heart failure in which a significant amount of the ejection fraction can be repaired, and left ventricular remodeling and dysfunction can be reversed or even restored completely. However, a considerable number of patients still present clinical signs and biochemical features of incomplete recovery from the pathophysiology of heart failure and are at risk for adverse outcomes such as re-deterioration of systolic function and recurrence of HFrEF. Furthermore, it is revealed from a microscopic perspective that even if partial or complete reverse remodeling occurs, the morphological changes of cardiomyocytes, extracellular matrix deposition, and abnormal transcription and expression of pathological genes still exist. Patients with "recovered ejection fraction" have milder clinical symptoms and better outcomes than those with continued reduction of ejection fraction. Based on the unique characteristics of this subgroup and the existence of many unknowns, the academic community defines it as a new category-heart failure with recovered ejection fraction (HFrecEF). Because there is a shortage of natural history data for this population as well as high-quality clinical and basic research data, it is difficult to accurately evaluate clinical risk and manage this population. This review will present the current understanding of HFrecEF from the limited literature.

Acute clinical presentation of nonischemic cardiomyopathies: early detection by cardiovascular magnetic resonance

Nonischemic cardiomyopathies include a wide range of dilated, hypertrophic and arrhythmogenic heart muscle disorders, not explained by coronary artery disease, hypertension, valvular or congenital heart disease. Advances in medical treatments and the availability of implantable cardioverter defibrillators to prevent sudden cardiac death have allowed a substantial increase in the survival of affected individuals, thus making early diagnosis and tailored treatment mandatory. The characterization of cardiomyopathies has received a great boost from the recent advances in cardiovascular magnetic resonance (CMR) imaging, which, to date, represents the gold standard for noninvasive assessment of cardiac morphology, function and myocardial tissue changes. An acute clinical presentation has been reported in a nonnegligible proportion of patients with nonischemic cardiomyopathies, usually complaining of acute chest pain, worsening dyspnoea or palpitations; 'hot phases' of cardiomyopathies are characterized by a dynamic rise in high-sensitivity troponin, myocardial oedema on CMR, arrhythmic instability, and by an increased long-term risk of adverse remodelling, progression of myocardial fibrosis, heart failure and malignant ventricular arrhythmias. Prompt recognition of 'hot phases' of nonischemic cardiomyopathies is of utmost importance to start an early, individualized treatment in these high-risk patients. On the one hand, CMR represents the gold standard imaging technique to detect early and typical signs of ongoing myocardial remodelling in patients presenting with a 'hot phase' nonischemic cardiomyopathy, including myocardial oedema, perfusion abnormalities and pathological mapping values. On the other hand, CMR allows the differential diagnosis of other acute heart conditions, such as acute coronary syndromes, takotsubo syndrome, myocarditis, pericarditis and sarcoidosis. This review provides a deep overview of standard and novel CMR techniques to detect 'hot phases' of cardiomyopathies, as well as their clinical and prognostic utility.

Elevated α-hydroxybutyrate dehydrogenase is associated with in-hospital mortality in non-ischemic dilated cardiomyopathy

Background

Previous Study Found That Implantation of a Cardioverter-Defibrillator Likely Caused a Worse Prognosis in Older Patients With non-Ischemic Systolic Heart Failure. This Suggests That More Precise Risk Stratification Is Needed in Elderly Patients. We Conducted a Retrospective Study to Evaluate the Association of α-Hydroxybutyrate Dehydrogenase (α-HBDH) With Mortality During Hospitalization in Elderly Patients With non-Ischemic Dilated Cardiomyopathy (NIDCM).

Methods

1,019 Elderly Patients (age ≥60 Years) Diagnosed With NIDCM Were Retrospectively Enrolled From January 2010 to December 2019. Univariate and Multivariate Analyses Were Showed to Explore the Relationship Between α-HBDH and in- Hospital Death.

Results

Patients in elevated α-HBDH group (>182 U/L) had a longer hospital stays and higher in-hospital mortality. Univariate logistics regression analysis showed that elevated α-HBDH was significantly related to mortality (OR: 7.004, 95% CI: 3.583–13.693, p < 0.001). Receiver operator characteristic (ROC) curve analysis reflected that α-HBDH levels had excellent predictive power for in-hospital death (AUC = 0.810, 95% CI: 0.745–0.876, p < 0.001). After adjustment of age, serum creatine, albumin and LVEF, multivariate regression analysis validated the association of elevated α-HBDH with increased risk of in-hospital death (p < 0.05).

Conclusions

Elevated α-HBDH level is significantly related to in-hospital mortality in older patients with NIDCM.

Pharmacological Anti-Remodelling Effects of Disease-Modifying Drugs in Heart Failure with Reduced Ejection Fraction

Cardiac remodelling is an adverse phenomenon linked to heart failure progression and an important contributor to heart failure severity. Cardiac remodelling could represent the real therapeutic goal in the treatment of patients with heart failure with reduced ejection fraction, being potentially reversed through different pharmacotherapies. Currently, there are well-established drugs such as angiotensin-converting enzyme inhibitors/angiotensin II receptor blockers and β-blockers with anti-remodelling effects; recently, angiotensin receptor neprilysin inhibitor effects on inhibiting cardiac remodelling (improving N-terminal pro-B-type natriuretic peptide levels, echocardiographic parameters of reverse cardiac remodelling and right ventricular function in patients with heart failure with reduced ejection fraction) were demonstrated. More recently, hemodynamic consequences of gliflozins, reduced cardiac hydrostatic pressure as a possible cause of ventricular remodelling and hypertrophy were proposed to explain potential anti-remodelling effects of gliflozins. Gliflozins exert their cardioprotective effects by attenuating myofibroblast activity and collagen-mediated remodelling. Another postulated mechanism is represented by the reduction in sympathetic activity, through the reduction in renal afferent nervous activity and the suppression of central reflex mechanisms. Benefits of gliflozins on left ventricular hypertrophy, dilation, and systolic and diastolic function were also described. In this review, we aimed to provide a wide overview on cardiac remodelling with a particular focus on possible anti-remodelling effects of angiotensin receptor neprilysin inhibitors and gliflozins.

Cardiac remodelling - Part 2: Clinical, imaging and laboratory findings. A review from the Study Group on Biomarkers of the Heart Failure Association of the European Society of Cardiology

In patients with heart failure, the beneficial effects of drug and device therapies counteract to some extent ongoing cardiac damage. According to the net balance between these two factors, cardiac geometry and function may improve (reverse remodelling, RR) and even completely normalize (remission), or vice versa progressively deteriorate (adverse remodelling, AR). RR or remission predict a better prognosis, while AR has been associated with worsening clinical status and outcomes. The remodelling process ultimately involves all cardiac chambers, but has been traditionally evaluated in terms of left ventricular volumes and ejection fraction. This is the second part of a review paper by the Study Group on Biomarkers of the Heart Failure Association of the European Society of Cardiology dedicated to ventricular remodelling. This document examines the proposed criteria to diagnose RR and AR, their prevalence and prognostic value, and the variables predicting remodelling in patients managed according to current guidelines. Much attention will be devoted to RR in patients with heart failure with reduced ejection fraction because most studies on cardiac remodelling focused on this setting.

Cardiac Remodeling in Hypertension: Clinical Impact on Brain, Heart, and Kidney Function

Hypertension is the most common causative factor of cardiac remodeling, which, in turn, has been associated with changes in brain and kidney function. Currently, the role of blood biomarkers as indices of cardiac remodeling remains unclear. In contrast, cardiac imaging, including echocardiography and cardiovascular magnetic resonance (CMR), has been a valuable noninvasive tool to assess cardiac remodeling. Cardiac remodeling during the course of systemic hypertension is not the sole effect of the latter. "Remodeling" of other vital organs, such as brain and kidney, also takes place. Therefore, it will be more accurate if we discuss about "hypertensive remodeling" involving the heart, the brain, and the kidneys, rather than isolated cardiac remodeling. This supports the idea of their simultaneous assessment to identify the early, silent lesions of total "hypertensive remodeling". In this context, magnetic resonance imaging is the ideal modality to provide useful information about these organs in a noninvasive fashion and without radiation. For this purpose, we propose a combined protocol to employ MRI in the simultaneous assessment of the heart, brain and kidneys. This protocol should include all necessary indices for the evaluation of "hypertensive remodeling" in these 3 organs, and could be performed within a reasonable time, not exceeding one hour, so that it remains patient-friendly. Furthermore, a combined protocol may offer "all in one examination" and save time. Finally, the amount of contrast agent used will be limited granted that post-contrast evaluations of the three organs will be performed after 1 injection.

Roles of transient receptor potential channel 6 in glucose-induced cardiomyocyte injury

BACKGROUND

Diabetic cardiomyopathy (DCM) is a serious complication of end-stage diabetes that presents symptoms such as cardiac hypertrophy and heart failure. The transient receptor potential channel 6 (TRPC6) protein is a very important selective calcium channel that is closely related to the development of various cardiomyopathies.

AIM

To explore whether TRPC6 affects cardiomyocyte apoptosis and proliferation inhibition in DCM.

METHODS

We compared cardiac function and myocardial pathological changes in wild-type mice and mice injected with streptozotocin (STZ), in addition to comparing the expression of TRPC6 and P-calmodulin-dependent protein kinase II (P-CaMKII) in them. At the same time, we treated H9C2 cardiomyocytes with high glucose and then evaluated the effects of addition of SAR, a TRPC6 inhibitor, and KN-93, a CaMKII inhibitor, to such H9C2 cells in a high-glucose environment.

RESULTS

We found that STZ-treated mice had DCM, decreased cardiac function, necrotic cardiomyocytes, and limited proliferation. Western blot and immunofluorescence were used to detect the expression levels of various appropriate proteins in the myocardial tissue of mice and H9C2 cells. Compared to those in the control group, the expression levels of the apoptosis-related proteins cleaved caspase 3 and Bax were significantly higher in the experimental group, while the expression of the proliferation-related proteins proliferating cell nuclear antigen (PCNA) and CyclinD1 was significantly lower. In vivo and in vitro, the expression of TRPC6 and P-CaMKII increased in a high-glucose environment. However, addition of inhibitors to H9C2 cells in a high-glucose environment resulted in alleviation of both apoptosis and proliferation inhibition.

CONCLUSION

The inhibition of apoptosis and proliferation of cardiomyocytes in a high-glucose environment may be closely related to activation of the TRPC6/P-CaMKII pathway.

Apigenin inhibits isoproterenol‐induced myocardial fibrosis and Smad pathway in mice by regulating oxidative stress and miR‐122‐5p/155‐5p expressions

Apigenin, a flavonoid isolated from Apium graveolens, is an effective natural active ingredient that inhibits transforming growth factor-β1 (TGF-β1)-induced cardiac fibroblasts (CFs) differentiation and collagen synthesis. However, its effects on isoproterenol-induced myocardial fibrosis in mice remain unknown. This study aimed to examine the effect of apigenin in the prevention of myocardial fibrosis. A mouse model of myocardial fibrosis induced by isoproterenol was established, and the mice were given apigenin 75-300 mg/kg orally for 40 days. The results showed that the heart weight coefficient, myocardial hydroxyproline, collagen accumulation, and malondialdehyde levels in the apigenin-treated groups were significantly reduced. In contrast, the activity of myocardial superoxide dismutase and glutathione peroxidase were significantly enhanced. The results of real-time quantitative polymerase chain reaction and western blot assays showed that apigenin could significantly upregulate the expressions of myocardial microRNA-122-5p (miR-122-5p), c-Ski, and Smad7 and downregulate the expressions of myocardial miR-155-5p, α-smooth muscle actin, collagen I/III, NF-κB, TGF-β1, hypoxia-inducible factor-1α (HIF-1α), Smad2/3, and p-Smad2/3. In vitro, the differentiation and extracellular matrix production, as well as TGF-β1/Smads axis, were further reduced after treatment of miR-122-5p mimic or miR-155-5p inhibitor-transfected and TGF-β1-stimulated CFs with apigenin. These results suggested that apigenin increased the expression of miR-122-5p and decreased the expression of miR-155-5p, which subsequently downregulated and upregulated the target genes HIF-1α and c-Ski, respectively. Furthermore, apigenin administration downregulated TGF-β1-induced Smad2/3 and upregulated Smad7. In addition, it reduced the NF-κB/TGF-β1 signaling pathway axis by increasing antioxidant ability to exert the antifibrotic effects.

Effect of n-3 PUFA on left ventricular remodelling in chronic heart failure: a systematic review and meta-analysis

Accumulating evidence suggests that supplementation of n-3 PUFA was associated with reduction in risk of major cardiovascular events. This meta-analysis was to systematically evaluate whether daily supplementation and accumulated intake of n-3 PUFA are associated with improved left ventricular (LV) remodelling in patients with chronic heart failure (CHF). Articles were obtained from Pubmed, Clinical key and Web of Science from inception to January 1 in 2021, and a total of twelve trials involving 2162 participants were eligible for inclusion. The sources of study heterogeneity were explained by I2 statistic and subgroup analysis. Compared with placebo groups, n-3 PUFA supplementation improved LV ejection fraction (LVEF) (eleven trials, 2112 participants, weighted mean difference (WMD) = 2·52, 95 % CI 1·25, 3·80, I2 = 87·8 %) and decreased LV end systolic volume (five studies, 905 participants, WMD = -3·22, 95 % CI 3·67, -2·77, I2 = 0·0 %) using the continuous variables analysis. Notably, the high accumulated n-3 PUFA dosage groups (≥ 600 g) presented a prominent improvement in LVEF, while the low and middle accumulated dosage (≤ 300 and 300-600 g) showed no effects on LVEF. In addition, n-3 PUFA supplementation decreased the levels of pro-inflammatory mediators including TNF-α, IL-6 (IL-6) and hypersensitive c-reactive protein. Therefore, the present meta-analysis demonstrated that n-3 PUFA consumption was associated with a substantial improvement of LV function and remodelling in patients subjected to CHF. The accumulated dosage of n-3 PUFA intake is vital for its cardiac protective role.

Integrative bioinformatics analysis of potential therapeutic targets and immune infiltration characteristics in dilated cardiomyopathy

Background

Dilated cardiomyopathy (DCM) is currently the major cause of systolic heart failure. This study explored potential therapeutic targets and investigated the role of immune cell infiltration in DCM.

Methods

Three DCM datasets (GSE3585, GSE9800, and GSE84796) from the Gene Expression Omnibus (GEO) database were merged into an integrated dataset, and batch effects were removed. Differentially expressed genes (DEGs) were screened and the associations between gene co-expression modules and clinical traits were assessed by weighted gene co-expression network analysis (WGCNA) in R software. Any DEGs from the integrated dataset overlapped with the significant module genes were defined as common genes (CGs). Enrichment analysis of the CGs was performed. The protein-protein interaction (PPI) network of the CGs was visualized and the hub gene was identified by using Cytoscape 3.8.2 software. The miRNA-transcription factor-mRNA (miRNA-TF-mRNA) network was constructed using Cytoscape to unveil the regulatory relationships in DCM. Finally, the CIBERSORT method (https://cibersort.stanford.edu/) was used to investigate immune cell infiltration in DCM.

Results

A total of 53 DEGs were identified, and 5 gene co-expression modules were detected by WGCNA of the DCM and control group samples of cardiac tissue. Genes such as FRZB, ASPN, and PHLDA1 were significantly upregulated, whereas IDH2 and ENDOG were significantly downregulated. Functional enrichment analysis showed that CGs were mainly enriched in the extracellular matrix (ECM) signaling pathway. ASPN was the hub gene in the PPI network. The miRNA-TF-mRNA network revealed that FRZB and ASPN were targeted by paired related homeobox 2 (Prrx2). We also found that miR-129-5p could regulate ASPN, PHLDA1, and IDH2 simultaneously. The immune infiltration analysis revealed higher levels of M1 macrophages in DCM samples than in the control samples.

Conclusions

In conclusion, we speculate that miR-129-5p might target ASPN in regulating DCM via the ECM signaling pathway. Macrophage infiltration may be involved in ECM remodeling and eventually lead to DCM.

ADAM17, A Key Player of Cardiac Inflammation and Fibrosis in Heart Failure Development During Chronic Catecholamine Stress

Heart failure development is characterized by persistent inflammation and progressive fibrosis owing to chronic catecholamine stress. In a chronic stress state, elevated catecholamines result in the overstimulation of beta-adrenergic receptors (βARs), specifically β2-AR coupling with Gαi protein. Gαi signaling increases the activation of receptor-stimulated p38 mitogen-activated-protein-kinases (p38 MAPKs) and extracellular signal-regulated kinases (ERKs). Phosphorylation by these kinases is a common way to positively regulate the catalytic activity of A Disintegrin and Metalloprotease 17 (ADAM17), a metalloprotease that has grown much attention in recent years and has emerged as a chief regulatory hub in inflammation, fibrosis, and immunity due to its vital proteolytic activity. ADAM17 cleaves and activates proinflammatory cytokines and fibrotic factors that enhance cardiac dysfunction via inflammation and fibrosis. However, there is limited information on the cardiovascular aspect of ADAM17, especially in heart failure. Hence, this concise review provides a comprehensive insight into the structure of ADAM17, how it is activated and regulated during chronic catecholamine stress in heart failure development. This review highlights the inflammatory and fibrotic roles of ADAM17’s substrates; Tumor Necrosis Factor α (TNFα), soluble interleukin-6 receptor (sIL-6R), and amphiregulin (AREG). Finally, how ADAM17-induced chronic inflammation and progressive fibrosis aggravate cardiac dysfunction is discussed.

The Effect of Obesity, Hypertension, Diabetes Mellitus, Alcohol, and Sleep Apnea on the Risk of Atrial Fibrillation

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia associated with a two-fold increase in mortality caused by a higher risk of stroke and heart failure. Currently, AF is present in ~ 2 % of the general population, and its incidence and prevalence are increasing. Obesity, hypertension, diabetes mellitus, obstructive sleep apnea, and alcohol consumption increase the risk of AF. Each unit of increase in BMI increases the risk of AF by 3 %, and intensive weight loss is also associated with reduced AF recurrence. Hypertension increases the risk of AF by 50 % in men and by 40 % in women, and explains ≈ 20 % of new AF cases. Patients with obstructive sleep apnea are at four times higher risk of developing AF than subjects without sleep apnea. Higher concentrations of pro-inflammatory cytokines, higher amounts of epicardial adipose tissue, and a higher degree of ventricular diffuse myocardial fibrosis are present in AF patients and patients with the aforementioned metabolic disorders. Several prospective cohort studies and randomized trials have been initiated to show whether weight loss and treatment of other risk factors will be associated with a reduction in AF recurrences.

Different Patterns of Kidney Fibrosis Are Indicative of Injury to Distinct Renal Compartments

Kidney fibrosis is a common manifestation and hallmark of a wide variety of chronic kidney disease (CKD) that appears in different morphological patterns, suggesting distinct pathogenic causes. Broad macroscopically visible scars are the sequelae of severe focal injury and complete parenchymal destruction, reflecting a wound healing response as a consequence of infarction. In the kidney, chronic glomerular injury leads to atrophy of the corresponding tubule, degeneration of this specific nephron, and finally interstitial fibrosis/tubular atrophy (IF/TA). Compared to this glomerulus-induced focal replacement scar, diffuse fibrosis independent of tubular atrophy appears to be a different pathogenic process. Kidney fibrosis appears to develop in a compartment-specific manner, but whether focal and diffuse fibrosis has distinct characteristics associated with other glomerular or tubulointerstitial lesions remains elusive. In the present study, we aimed to analyze renal fibrotic patterns related to renal lesions, which directly contribute to renal fibrogenesis, to unravel fibrotic patterns and manifestations upon damage to distinct renal compartments. Patterns of kidney fibrosis were analyzed in experimental models of CKD and various renal pathologies in correlation with histopathological and ultrastructural findings. After the induction of isolated crescentic glomerulonephritis (GN) in nephrotoxic serum-nephritis (NTN), chronic glomerular damage resulted in predominantly focal fibrosis adjacent to atrophic tubules. By contrast, using unilateral ureteral obstruction (UUO) as a model of primary injury to the tubulointerstitial compartment revealed diffuse fibrosis as the predominant pattern of chronic lesions. Finally, folic acid-induced nephropathy (FAN) as a model of primary tubular injury with consecutive tubular atrophy independent of chronic glomerular damage equally induced predominant focal IF/TA. By analyzing several renal pathologies, our data also suggest that focal and diffuse fibrosis appear to contribute as chronic lesions in the majority of human renal disease, mainly being present in antineutrophil cytoplasmic antibody (ANCA)-associated GN, lupus nephritis, and IgA nephropathy (IgAN). Focal IF/TA correlated with glomerular damage and irreversible injury to nephrons, whereas diffuse fibrosis in ANCA GN was associated explicitly with interstitial inflammation independent of glomerular damage and nephron loss. Ultrastructural analysis of focal IF/TA versus diffuse fibrosis revealed distinct matrix compositions, further supported by different collagen signatures in transcriptome datasets. With regard to long-term renal outcome, only the extent of focal IF/TA correlated with the development of end-stage kidney disease (ESKD) in ANCA GN. In contrast, diffuse kidney fibrosis did not associate with the long-term renal outcome. In conclusion, we here provide evidence that a focal pattern of kidney fibrosis seems to be associated with nephron loss and replacement scarring. In contrast, a diffuse pattern of kidney fibrosis appears to result from primary interstitial inflammation and injury.

3D Myocardial Mechanical Wave Measurements: Toward In Vivo 3D Myocardial Elasticity Mapping

OBJECTIVES

This study aimed to investigate the potential of a novel 3-dimensional (3D) mechanical wave velocity mapping technique, based on the natural mechanical waves produced by the heart itself, to approach a noninvasive 3D stiffness mapping of the left ventricle.

BACKGROUND

Myocardial fibrosis is recognized as a pathophysiological substrate of major cardiovascular disorders such as cardiomyopathies and valvular heart disease. As fibrosis leads to increased myocardial stiffness, ultrasound elastography measurements could provide important clinical information.

METHODS

A 3D high frame rate imaging sequence was implemented on a high-end clinical ultrasound scanner to achieve 820 volumes/s when gating over 4 consecutive cardiac cycles. Five healthy volunteers and 10 patients with various degrees of aortic stenosis were included to evaluate feasibility and reproducibility. Mechanical waves were detected using the novel Clutter Filter Wave Imaging approach, shown to be highly sensitive to the weak tissue displacements caused by natural mechanical waves.

RESULTS

3D spatiotemporal maps of mechanical wave velocities were produced for all subjects. Only the specific mechanical wave at atrial contraction provided a full 3D coverage of the left ventricle (LV). The average atrial kick propagation velocity was 1.6 ± 0.2 m/s in healthy volunteers and 2.8 ± 0.8 m/s in patients (p = 0.0016). A high correlation was found between mechanical wave velocity and age (R² = 0.88, healthy group), septal wall thickness (R² = 0.73, entire group), and peak jet velocity across the aortic valve (R² = 0.70). For 3 of the patients, the higher mechanical wave velocity coexisted with the presence of late gadolinium enhancement on cardiac magnetic resonance.

CONCLUSIONS

In this study, 3D LV mechanical wave velocities were visualized and measured in healthy volunteers and patients with aortic stenosis. The proposed imaging sequence and measurement technique allowed, for the first time, the measurement of full spatiotemporal 3D elasticity maps of the LV using ultrasound. (Ultrasonic markers for myocardial fibrosis and prognosis in aortic stenosis; NCT03422770).

Molecular remodeling of Cx43, but not structural remodeling, promotes arrhythmias in an arrhythmogenic canine model of nonischemic heart failure

BACKGROUND

Both gap junctional remodeling and interstitial fibrosis have been linked to impaired electrical conduction velocity (CV) and fatal ventricular arrhythmias in nonischemic heart failure (HF). However, the arrhythmogenic role of the ventricular gap junctional Cx43 in nonischemic HF remains in debate. Here, we assessed this in a newly developed arrhythmogenic canine model of nonischemic HF.

METHODS AND RESULTS

Nonischemic HF was induced in canines by combined aortic valve insufficiency and aortic constriction. Left ventricular (LV) myocardium from HF dogs showed similar pathological changes to that of humans. HF dogs had reduced LV function, widened QRS complexes, and spontaneous nonsustained ventricular tachycardia. CV was measured in intact LV epicardium with high-density grid mapping. Total (Cx43-T) and nonphosphorylated Cx43 (Cx43-NP) and histological interstitial fibrosis were assessed from these mapped LV tissues. Longitudinal CV, which was slowed in HF (49 ± 1 vs. 65 ± 2 cm/s in Ctl), was positively correlated with reduced total junctional Cx43 and negatively correlated with markedly increased junctional Cx43-NP (2-fold) in HF. Cx43 dephosphorylation in HF was associated with enhanced colocalization of PP2A at the level of Cx43. Unchanged action potential upstroke and transverse CV were associated with unaltered Cx43 lateralization and interstitial fibrosis in the nonischemic HF canine LV.

CONCLUSION

Our unique arrhythmogenic canine model of HF resembles human nonischemic HF (prior to the end stage). Cx43 remodeling occurs prior to the structural remodeling (with lack of fibrosis) in HF and it is crucial in slowed CV and ventricular arrhythmia development. Our findings suggest that altered Cx43 alone is arrhythmogenic and modulation of Cx43 has the anti-arrhythmic therapeutic potential for HF patients.

Epigenetics-based therapeutics for myocardial fibrosis

Myocardial fibrosis (MF) is a reactive remodeling process in response to myocardial injury. It is mainly manifested by the proliferation of cardiac muscle fibroblasts and secreting extracellular matrix (ECM) proteins to replace damaged tissue. However, the excessive production and deposition of extracellular matrix, and the rising proportion of type I and type III collagen lead to pathological fibrotic remodeling, thereby facilitating the development of cardiac dysfunction and eventually causing heart failure with heightened mortality. Currently, the molecular mechanisms of MF are still not fully understood. With the development of epigenetics, it is found that epigenetics controls the transcription of pro-fibrotic genes in MF by DNA methylation, histone modification and noncoding RNAs. In this review, we summarize and discuss the research progress of the mechanisms underlying MF from the perspective of epigenetics, including the newest m6A modification and crosstalk between different epigenetics in MF. We also offer a succinct overview of promising molecules targeting epigenetic regulators, which may provide novel therapeutic strategies against MF.

Arrhythmic risk stratification by cardiac magnetic resonance tissue characterization: disclosing the arrhythmic substrate within the heart muscle

Sudden cardiac death (SCD) is a pivotal health problem worldwide. The identification of subjects at increased risk of SCD is crucial for the accurate selection of candidates for implantable cardioverter defibrillator (ICD) therapy. Current strategies for arrhythmic stratification largely rely on left ventricular (LV) ejection fraction (EF), mostly measured by echocardiography, and New York Heart Association functional status for heart failure with reduced EF. For specific diseases, such as hypertrophic and arrhythmogenic cardiomyopathy, some risk scores have been proposed; however, these scores take into account some parameters that are a partial reflection of the global arrhythmic risk and show a suboptimal accuracy. Thanks to a more comprehensive evaluation, cardiac magnetic resonance (CMR) provides insights into the heart muscle (the so-called tissue characterization) identifying cardiac fibrosis as an arrhythmic substrate. Combining sequences before and after administration of contrast media and mapping techniques, CMR is able to characterize the myocardial tissue composition, shedding light on both intracellular and extracellular alterations. Over time, late gadolinium enhancement (LGE) emerged as solid prognostic marker, strongly associated with major arrhythmic events regardless of LVEF, adding incremental value over current strategy in ischemic heart disease and non-ischemic cardiomyopathies. The evidence on a potential prognostic role of mapping imaging is promising. However, mapping techniques require further investigation and standardization. Disclosing the arrhythmic substrate within the myocardium, CMR should be considered as part of a multiparametric approach to personalized arrhythmic stratification.

Machine Learning-Based Segmentation of Left Ventricular Myocardial Fibrosis from Magnetic Resonance Imaging

PURPOSE OF REVIEW

Myocardial fibrosis (MF) arises due to myocardial infarction and numerous cardiac diseases. MF may lead to several heart disorders, such as heart failure, arrhythmias, and ischemia. Cardiac magnetic resonance (CMR) imaging techniques, such as late gadolinium enhancement (LGE) CMR, enable non-invasive assessment of MF in the left ventricle (LV). Manual assessment of MF on CMR is a tedious and time-consuming task that is subject to high observer variability. Automated segmentation and quantification of MF is important for risk stratification and treatment planning in patients with heart disorders. This article aims to review the machine learning (ML)-based methodologies developed for MF quantification in the LV using CMR images.

RECENT FINDINGS

With the availability of relatively large labeled datasets supervised learning methods based on both conventional ML and state-of-the-art deep learning (DL) methods have been successfully applied for automated segmentation of MF. The incorporation of ML algorithms into imaging techniques such as 3D LGE CMR permits fast characterization of MF on CMR imaging and may enhance the diagnosis and prognosis of patients with heart disorders. Concurrently, the studies using cine CMR images have revealed that accurate segmentation of MF on non-contrast CMR imaging might be possible. The application of ML/DL tools in CMR image interpretation is likely to result in accurate and efficient quantification of MF.

Diagnostic and prognostic role of cardiac magnetic resonance in acute myocarditis

Acute myocarditis (AM) is commonly found in everyday clinical practice. Differential diagnosis between various causes of myocardial damage with non-obstructive coronary arteries can be cumbersome for clinician. Moreover, AM may be provoked by a number of different causes and clinical presentation can be heterogeneous with potential overlap going from asymptomatic or subclinical to severe heart failure, arrhythmias, and death. Cardiac magnetic resonance (CMR) over the last decades has proven to be the diagnostic technique of choice since it allows identifying AM with excellent diagnostic accuracy. Latest technological advancement with parametric imaging such as T1 and T2 mapping further increases sensitivity and provides additional help towards a correct diagnosis. CMR however is no longer to be considered as a mere diagnostic tool but also as a powerful source of prognostic information. Scientific evidence has corroborated CMR's role beyond diagnosis demonstrating how late gadolinium enhancement (LGE) presence is a powerful predictor of cardiac events and how the presence of septal LGE is to be considered of worst prognosis regardless of LGE extension even in patients with preserved global systolic function. CMR should be routinely performed in all patients with AM suspicion since its diagnostic and prognostic role is of paramount important and could modify therapeutic strategy and subsequent clinical decisions.

Correlation between septal midwall late gadolinium enhancement on CMR and conduction delay on ECG in patients with nonischemic dilated cardiomyopathy

Background

Septal midwall late gadolinium enhancement (LGE) on cardiac magnetic resonance imaging (CMR) is a characteristic finding in nonischemic dilated cardiomyopathy (DCM) and is associated with adverse cardiac events. QRS-prolongation in DCM is also frequently present and a predictor of arrhythmic events and mortality. Since the His-Purkinje fibres are located in the interventricular septum, QRS-prolongation may directly result from septal fibrosis, visualized by LGE. Our aim was to study the correlation of the presence and extent of septal midwall LGE and QRS-duration.

Methods

DCM-patients with left ventricular (LV) dysfunction (LVEF < 50%) were included. LV volumes, systolic function and nonischemic septal midwall LGE, defined as patchy or stripe-like LGE in the septal segments, were quantified. QRS-duration on standard 12-lead ECG was measured.

Results

165 DCM-patients were included (62% male, mean age 59 ± 15 years) with a median LVEF of 36% [24–44]. Fifty-one patients (31%) demonstrated septal midwall LGE with a median extent of 8.1 gram [4.3–16.8]. Patients with midwall LGE had increased LV end-diastolic volumes (EDV) 248 mL [193–301] vs. 193 mL [160–239], p < 0.001) and lower LVEF (26% [18–35] vs. 40% [32–45], p < 0.001). Median QRS-duration was 110 ms [95–146] without a correlation to the presence nor extent of midwall LGE. QRS-duration was moderately correlated with LV-dilation and mass (respectively r = 0.35, p < 0.001 and r = 0.30, p < 0.001).

Conclusion

In DCM-patients, QRS-prolongation and septal midwall LGE are frequently present and often co-exist. However, they are not correlated. This suggests that the assessment of LGE-CMR has complementary value to ECG evaluation in the clinical assessment and risk stratification of DCM-patients.

Diffuse myocardial fibrosis and the prognosis of heart failure with reduced ejection fraction in Chinese patients: a cohort study

Evidence regarding the relationship between diffuse myocardial fibrosis and the prognosis of heart failure with reduced ejection fraction (HFrEF) was limited. Therefore, this study set out to investigate whether diffuse myocardial fibrosis was independently related to the prognosis of failure with reduced ejection fraction in Chinese patients after adjusting for other covariates. The present study was a cohort study. A total of 45 consecutive HFrEF patients were involved in Zhongshan Hospital of Fudan University in China from 1/9/2015 to 31/12/2016. The target-independent variable was extracellular volume (ECV) quantified by cardiac magnetic resonance T1 mapping using the modified Look-Locker inversion recovery (MOLLI) sequence at baseline. To assess the prognostic impact of MOLLI-ECV, its association with hospitalization for heart failure/cardiac death was tested by multivariable Cox regression analysis. Covariates involved in this study included age, gender, body mass index, heart rate, systolic blood pressure diastolic blood pressure, smoking, hypertension, diabetes mellitus, etiology, NYHA functional class, blood urea nitrogen, creatinine, serum uric acid, total bilirubin, and growth stimulation-expressed gene 2. Ten age- and sex-matched healthy participants with no history of cardiovascular disease served as a control group. Mean MOLLI-ECV was significantly higher in HFrEF patients versus healthy controls (29.55 ± 1.46% vs. 23.17 ± 1.93%, P < 0.001). Patients were followed for 9 months, during which the primary outcome (cardiac death or first heart failure hospitalization) occurred in 15 patients. By Kaplan-Meier analysis, patients with high MOLLI-ECV ≥ 30.10% had shorter event-free survival than the middle (MOLLI-ECV between 30.10 and 28.60) and low (MOLLI-ECV < 28.60) MOLLI-ECV patients (log-rank, P = 0.0035). Result of fully-adjusted multivariable Cox regression analysis showed MOLLI-ECV was positively associated with the composite outcome of HFrEF patients after adjusting confounders hazard ratio (HR) 2.57, 95% CI (1.09, 6.04). By subgroup analysis, a stronger association was seen in patients who with NYHA functional class III-IV, hematocrit < 39.8%, left atrial diameter ≥ 53.5 mm, or without the medical history of MRA or diuretics other than MRA. The P for interaction was < 0.05. In HFrEF patients, the relationship between MOLLI-ECV determined by CMR and the composite outcome is linear. High MOLLI-ECV was associated with a higher rate of cardiac mortality and first HF hospitalization in the short term follow up.

Dilated cardiomyopathy: from epidemiologic to genetic phenotypes: A translational review of current literature

Dilated cardiomyopathy (DCM) is characterized by left ventricular dilatation and, consecutively, contractile dysfunction. The causes of DCM are heterogeneous. DCM often results from myocarditis, exposure to alcohol, drugs or other toxins and metabolic or endocrine disturbances. In about 35% of patients, genetic mutations can be identified that usually involve genes responsible for cytoskeletal, sarcomere and nuclear envelope proteins. Due to its heterogeneity, a detailed diagnostic work-up is necessary to identify the specific underlying cause and exclude other conditions with phenotype overlap. Patients with DCM show typical systolic heart failure symptoms, but, with progress of the disease, diastolic dysfunction is present as well. Depending on the underlying pathology, DCM patients also become apparent through arrhythmias, thromboembolic events or cardiogenic shock. Disease progression and prognosis are mostly driven by disease severity and reverse remodelling within the heart. The worst prognosis is seen in patients with lowest ejection fractions or severe diastolic dysfunction, leading to terminal heart failure with subsequent need for left ventricular assist device implantation or heart transplantation. Guideline-based heart failure medication and device therapy reduces the frequency of heart failure hospitalizations and improves survival.

Imaging, Biomarker, and Clinical Predictors of Cardiac Remodeling in Heart Failure With Reduced Ejection Fraction

In response to injury, hemodynamic changes, or neurohormonal activation, the heart undergoes a series of structural and functional changes that have been termed cardiac remodeling. Remodeling is defined as changes in cardiac geometry and/or function over time and can be measured in terms of changes in cardiac chamber dimensions, wall thickness, volumes, mass, and ejection fraction at serial imaging examinations. As to cardiac chambers, left ventricular (LV) remodeling has been best studied in patients with heart failure with reduced ejection fraction. Although LV remodeling may compensate for abnormal hemodynamic parameters and function in the short term, left unchecked, it is associated with worsening cardiac function and poor prognosis. On the other hand, reversing LV geometry and/or function closer to that of a normal heart (also known as reverse remodeling) is associated with improved cardiac function and better prognosis. Because of its close relationship with clinical outcomes, remodeling may potentially be targeted in clinical management and used in trials as a surrogate endpoint. Standardized definition of remodeling and reliable tools to predict and monitor the presence, direction, and magnitude of cardiac remodeling are needed. Together with clinical and imaging findings, circulating biomarkers (most notably N-terminal pro-B-type natriuretic peptide, high-sensitivity troponin, and soluble suppression of tumorigenesis-2) may be helpful in this respect.

Variability of cardiovascular magnetic resonance (CMR) T1 mapping parameters in healthy volunteers during long-term follow-up

Background

Myocardial T1 and extracellular volume (ECV) derived from cardiovascular MRIs are more and more widely accepted as important markers for diagnosis, risk prediction and monitoring of cardiac disease. Yet data regarding long-term stability of myocardial T1 mapping are lacking. The aim of this study was to investigate the long-term stability of native and postcontrast T1 mapping values in healthy volunteers.

Methods

18 strictly selected healthy volunteers (52±10 years, 12 men) were studied on a Philips Achieva 1.5 Tesla scanner. T1 relaxation times were measured before and 15 min after a bolus contrast injection of gadolinium diethylenetriamine penta-acetic acid (DTPA) (0.2 mmol/kg) using a single-breath-hold modified Look-Locker inversion recovery 3(3)3(3)5 sequence. ECV was calculated using native and postcontrast T1 times of myocardium and blood correcting for blood haematocrit. Exams were repeated 3.6±0.5 years later under the same conditions and using the same scan protocols.

Results

Cardiac biomarkers (high-sensitivity troponin T and N terminal pro-brain natriuretic peptide) remained unchanged, as well as left ventricular mass, and global and longitudinal function. No significant change occurred regarding native T1 times (1017±24 ms vs 1015±21 ms; P=0.6), postcontrast T1 times (426±38 ms vs 413±20 ms; P=0.13) or ECV (22%±2% vs 23%±2%; P=0.3). Native T1 time and ECV appeared to be better reproducible than postcontrast T1, resulting in lower coefficients of variation (ECV: 3.5%, native T1: 1.3%, postcontrast T1: 6.4%) and smaller limits of agreement (ECV: 2%/−2%, native T1: 39 ms/−35 ms, postcontrast T1: 85 ms/−59 ms).

Conclusions

During long-term follow-up, native T1 and ECV values are very robust markers, whereas postcontrast T1 results appear less stable.

Formation of a TBX20-CASZ1 protein complex is protective against dilated cardiomyopathy and critical for cardiac homeostasis

By the age of 40, one in five adults without symptoms of cardiovascular disease are at risk for developing congestive heart failure. Within this population, dilated cardiomyopathy (DCM) remains one of the leading causes of disease and death, with nearly half of cases genetically determined. Though genetic and high throughput sequencing-based approaches have identified sporadic and inherited mutations in a multitude of genes implicated in cardiomyopathy, how combinations of asymptomatic mutations lead to cardiac failure remains a mystery. Since a number of studies have implicated mutations of the transcription factor TBX20 in congenital heart diseases, we investigated the underlying mechanisms, using an unbiased systems-based screen to identify novel, cardiac-specific binding partners. We demonstrated that TBX20 physically and genetically interacts with the essential transcription factor CASZ1. This interaction is required for survival, as mice heterozygous for both Tbx20 and Casz1 die post-natally as a result of DCM. A Tbx20 mutation associated with human familial DCM sterically interferes with the TBX20-CASZ1 interaction and provides a physical basis for how this human mutation disrupts normal cardiac function. Finally, we employed quantitative proteomic analyses to define the molecular pathways mis-regulated upon disruption of this novel complex. Collectively, our proteomic, biochemical, genetic, and structural studies suggest that the physical interaction between TBX20 and CASZ1 is required for cardiac homeostasis, and further, that reduction or loss of this critical interaction leads to DCM. This work provides strong evidence that DCM can be inherited through a digenic mechanism.

A molecular understanding of cardiomyocyte development is an essential goal for improving clinical approaches to CHD. While TBX20 is an essential transcription factor for heart development and its disease relevance is well established, many fundamental questions remain about the mechanism of TBX20 function. Principle among these is how TBX20 mutations associated with adult dilated cardiomyopathy circumvent (DCM) the essential embryonic requirement for TBX20 in heart development. Here we report using an integrated approach that TBX20 complexes with the cardiac transcription factor CASZ1 in vivo. We confirmed TBX20 and CASZ1 interact biochemically and genetically, and show mice heterozygous for both Tbx20 and Casz1 die, beginning at 4 to 8 weeks post birth, exhibiting hallmarks of DCM. Interestingly, the human mutant TBX20^F256I bypasses the early essential requirement for TBX20 but leads to DCM. We report here that TBX20^F256I disrupts the TBX20-CASZ1 interaction, ascribing clinical relevance to this protein complex. Further, by using quantitative proteomics we have identified the molecular pathways altered in TBX20-CASZ1-mediated DCM. Together, these results identify a novel interaction between TBX20 and CASZ1 that is essential for maintaining cardiac homeostasis and imply that DCM can be inherited through a digenic mechanism.

Myocardial T1 and T2 Mapping: Techniques and Clinical Applications

Cardiac magnetic resonance (CMR) imaging is widely used in various medical fields related to cardiovascular diseases. Rapid technological innovations in magnetic resonance imaging in recent times have resulted in the development of new techniques for CMR imaging. T1 and T2 image mapping sequences enable the direct quantification of T1, T2, and extracellular volume fraction (ECV) values of the myocardium, leading to the progressive integration of these sequences into routine CMR settings. Currently, T1, T2, and ECV values are being recognized as not only robust biomarkers for diagnosis of cardiomyopathies, but also predictive factors for treatment monitoring and prognosis. In this study, we have reviewed various T1 and T2 mapping sequence techniques and their clinical applications.

Neprilysin inhibition: A brief review of past pharmacological strategies for heart failure treatment and future directions

Heart failure (HF) is a manifestation of aberrant vascular responses and remains a public health concern with a worldwide prevalence of around 23 million and a 5-year mortality numerically equivalent to many cancers. Over the last two decades, mortality from HF reached a plateau with current pharmaceutical agents and mechanical cardiac support. In the last several years, various "novel" pharmaceutical agents have been tested in clinical trials and ultimately met with disappointment, showing only incremental benefit in the treatment of HF. Designing a HF drug with enhanced efficacy over existing agents seemed like a Sisyphean task. Yet again, pharmaceutical chemists have demonstrated their prowess in lateral thinking by developing a vasoactive agent which is a co-crystallized compound of valsartan and sacubitril in a one-to-one molar ratio; the former molecule belongs to a family of agents that are the current standard of care for HF and the latter molecule is a novel agent which inhibits neprilysin - a neutral endopeptidase found in human plasma which alters neurohumoral responses. In July of 2015, a drug which is a combination of valsartan and sacubitril was formally licensed by the United States Food and Drug Administration for the treatment of HF. This review describes the evolution of HF medications focusing on rational drug design with the first HF medication, the beta-adrenergic receptor antagonist. We then discuss the biochemical and physiological properties of sacubitril/valsartan which likely lead to its dramatic ability to ameliorate HF mortality.

External Magnetic Field-Induced Targeted Delivery of Highly Sensitive Iron Oxide Nanocubes for MRI of Myocardial Infarction

Magnetic field responsive nanocubes (MFRFs) are synthesized as nanoplatforms for external magnetic field-induced selective targeting of macrophages in the infarcted tissue and magnetic resonance imaging (MRI) monitoring. MFRFs have uniform size, favorable colloidal stability, and high magnetic properties. Under the influence of external magnetic field, MFRFs perform qualitative and quantitative MRI of myocardial infarction.