Implementation of a near-zero fluoroscopy approach in interventional electrophysiology: impact of operator experience.

PURPOSE: Catheter ablation is performed under fluoroscopic guidance. Reduction of radiation dose for patients and staff is emphasized by current recommendations. Previous studies have shown that lower operator experience leads to increased radiation dose. On the other hand, less experienced operators may depend even more on fluoroscopic guidance. Our study aimed to evaluate feasibility and efficacy of a non-fluoroscopic approach in different training levels. METHODS: From January 2017, a near-zero fluoroscopy approach was established in two centers. Four operators (beginner, 1st year fellow, 2nd year fellow, expert) were instructed to perform the complete procedure with the use of a 3-D mapping system without fluoroscopy. A historical cohort that underwent procedures with fluoroscopy use served as control group. Dose area product (DPA), procedure duration, acute procedural success, and complications were compared between the groups and for each operator. RESULTS: Procedures were performed in 157 patients. The first 100 patients underwent procedures with fluoroscopic guidance, the following 57 procedures were performed with the near-zero fluoroscopy approach. The results show a significant reduction in DPA for all operators immediately after implementation of the near-zero fluoroscopy protocol (control 637 ± 611 µGy/m2; beginner 44.1 ± 79.5 µGy/m2, p = 0.002; 1st year fellow 24.3 ± 46.4.5 µGy/m2, p = 0.001; 2nd year fellow 130.3 ± 233.3 µGy/m2, p = 0.003; expert 9.3 ± 37.4 µGy/m2, P < 0.001). Procedure duration, acute success, and complications were not significantly different between the groups. CONCLUSION: Our results show a 90% reduction of DPA shortly after implementation of a near-zero fluoroscopy approach in interventional electrophysiology even in operators in training.

Adverse left ventricular remodeling by glycoprotein nonmetastatic melanoma protein B in myocardial infarction.

Cardiac diseases are the leading cause of death. Available treatment approaches are not sufficient to reverse persistent cardiac damage after injury; thus, the search for new therapeutic targets is essential. Our microarray-based screening in rat hearts 24 h after myocardial infarction (MI) yielded glycoprotein nonmetastatic melanoma protein B (GPNMB), which is known to be involved in inflammation and fibrosis after tissue injury. However, its role in the heart was elusive. We found increased cardiac expression levels of GPNMB in rats and mice after MI. Analysis of DBA/2J mice, which lack functional GPNMB due to a spontaneous point mutation, showed that systemic GPNMB deficiency was associated with preserved cardiac function and less left ventricular dilation after MI compared with DBA/2J mice with reconstituted GPNMB expression. These improvements were associated with decreased expression of matrix metalloproteinase 9, the cardiac stress genes for natriuretic peptides (atrial natriuretic peptide and brain natriuretic peptide), and ß-myosin heavy chain after MI. Moreover, GPNMB deficiency attenuated the dilated cardiomyopathy in muscle lim protein knockout mice but could not prevent cardiac hypertrophy induced by isoprenaline infusion. This is the first experimental study to show that GPNMB adversely influences myocardial remodeling.-Järve, A., Mühlstedt, S., Qadri, F., Nickl, B., Schulz, H., Hübner, N., Özcelik, C., Bader, M. Adverse left ventricular remodeling by glycoprotein nonmetastatic melanoma protein B in myocardial infarction.

Cardiomyocyte-derived CXCL12 is not involved in cardiogenesis but plays a crucial role in myocardial infarction.

UNLABELLED: The chemokine CXCL12/SDF-1 is crucial for heart development and affects cardiac repair processes due to its ability to attract leukocytes and stem cells to injured myocardium. However, there is a great controversy whether CXCL12 is beneficial or detrimental after myocardial infarction (MI). The divergence in the reported CXCL12 actions may be due to the cellular source and time of release of the chemokine after MI. This study was designed to evaluate the role of cardiomyocyte-derived CXCL12 for cardiogenesis and heart repair after MI. We generated two rodent models each targeting CXCL12 in only one cardiac cell type: cardiomyocyte-specific CXCL12-overexpressing transgenic (Tg) rats and CXCL12 conditional knockout (cKO) mice. Animals of both models did not show any signs of cardiac abnormalities under baseline conditions. After induction of MI, cKO mice displayed preserved cardiac function and remodeling. Moreover, fibrosis was less pronounced in the hearts of cKO mice after MI. Accordingly, CXCL12 Tg rats revealed impaired cardiac function post-MI accompanied by enhanced fibrosis. Furthermore, we observed decreased numbers of infiltrating Th1 cells in the hearts of cKO mice. Collectively, our findings demonstrate that cardiomyocyte-derived CXCL12 is not involved in cardiac development but has adverse effects on the heart after injury via promotion of inflammation and fibrosis. KEY MESSAGES: • CXCL12 in cardiomyocytes is not involved in cardiac development. • CXCL12 deficiency in cardiomyocytes improves outcome of myocardial infarction. • CXCL12 overexpression in cardiomyocytes worsens outcome of myocardial infarction. • CXCL12 increases fibrosis and invasion of Th1 cells in the heart after infarction.

CCN1 mutation is associated with atrial septal defect.

The genetic basis of congenital heart disease remains unknown in most of the cases. Recently, a novel mouse model shed new light on the role of CCN1/CYR61, a matricellular regulatory factor, in cardiac morphogenesis. In a candidate gene approach, we analyzed a cohort of 143 patients with atrial septal defects (ASD) by sequencing the coding exons of CCN1. In addition to three frequent polymorphisms, we identified an extremely rare novel heterozygous missense mutation (c.139C > T; p.R47W) in one patient with severe ASD. The mutation leads to an exchange of residues with quite different properties in a highly conserved position of the N-terminal insulin-like growth factor binding protein module. Further bioinformatic analysis, exclusion of known ASD disease genes as well as the exclusion of the mutation in a very high number of ethnically matched controls (more than 1,000 individuals) and in public genetic databases, indicates that the p.R47W variant is a probable disease-associated mutation. The report about ASD in mice in heterozygous Ccn 1 +/- animals strongly supports this notion. Our study is the first to suggest a relationship between a probable CCN1 mutation and ASD. Our purpose here was to draw attention to CCN1, a gene that we believe may be important for genetic analysis in patients with congenital heart disease.

SDF-1α as a therapeutic stem cell homing factor in myocardial infarction.

Myocardial infarction is associated with persistent muscle damage, scar formation and depressed cardiac performance. Recent studies have demonstrated the clinical significance of stem cell-based therapies after myocardial infarction with the aim to improve cardiac remodeling and function by inducing the reconstitution of functional myocardium and formation of new blood vessels. Stem cell homing signals play an important role in stem cell mobilization from the bone marrow to the ischemic cardiac environment and are therefore crucial for myocardial repair. To date, the most prominent stem cell homing factor is the chemokine SDF-1α/CXCL12. This protein was shown to be significantly upregulated in many experimental models of myocardial infarction and in patients suffering from ischemic cardiac diseases, suggesting the involvement in the pathophysiology of these disorders. A number of studies focused on manipulating SDF-1α and its receptor CXCR4 as central regulators of the stem cell mobilization process. Targeted expression of SDF-1α after myocardial infarction was shown to result in increased engraftment of bone marrow-derived stem cells into infarcted myocardium. This was accompanied by beneficial effects on cardiomyocyte survival, neovascularization and cardiac function. Thus, the SDF-1/CXCR4 axis seems to be a promising novel therapeutic approach to improve post-infarction therapy by attracting circulating stem cells to remain, survive and possibly differentiate in the infarct area. This review will summarize clinical trials of stem cell therapy in patients with myocardial infarction. We further discuss the basic findings about SDF-1α in stem cell recruitment and its therapeutic implications in experimental myocardial infarction.

Plasma HER2 levels are not associated with cardiac function or hypertrophy in control subjects and heart failure patients.

A proper interaction between the endocardial-derived ligand Neuregulin-1 and the myocardial "Human Epidermal growth factor Receptor 2" (HER2) is essential for maintaining heart function. The shed extracellular domain (ECD) of HER2 circulates in blood and serves as a surrogate marker for breast cancer. Altered cardiac loading conditions are accompanied by dysregulation of the myocardial HER2 gene expression. We studied 193 controls with preserved ejection fraction (EF>55%) and 572 patients with different degrees of systolic heart failure: 98 had EF 45-55%, 138 patients EF 35-44%, and 336 patients, EF <35%, respectively. The corresponding mean HER2 levels were 6.44 ± 0.46 ng/mL, 6.07 ± 0.76 ng/mL and 6.57 ± 0.87 ng/mL, and 6.17 ± 0.71 ng/mL, respectively. Furthermore, there was no significant association between plasma HER2 levels and left ventricular filling pressures or the left ventricular wall thickness. The HER2 plasma levels do not reflect the cardiac function and are therefore not useful as a biomarker for heart failure.

Connective tissue growth factor overexpression in cardiomyocytes promotes cardiac hypertrophy and protection against pressure overload.

Connective tissue growth factor (CTGF) is a secreted protein that is strongly induced in human and experimental heart failure. CTGF is said to be profibrotic; however, the precise function of CTGF is unclear. We generated transgenic mice and rats with cardiomyocyte-specific CTGF overexpression (CTGF-TG). To investigate CTGF as a fibrosis inducer, we performed morphological and gene expression analyses of CTGF-TG mice and rat hearts under basal conditions and after stimulation with angiotensin II (Ang II) or isoproterenol, respectively. Surprisingly, cardiac tissues of both models did not show increased fibrosis or enhanced gene expression of fibrotic markers. In contrast to controls, Ang II treated CTGF-TG mice displayed preserved cardiac function. However, CTGF-TG mice developed age-dependent cardiac dysfunction at the age of 7 months. CTGF related heart failure was associated with Akt and JNK activation, but not with the induction of natriuretic peptides. Furthermore, cardiomyocytes from CTGF-TG mice showed unaffected cellular contractility and an increased Ca(2+) reuptake from sarcoplasmatic reticulum. In an ischemia/reperfusion model CTGF-TG hearts did not differ from controls.Our data suggest that CTGF itself does not induce cardiac fibrosis. Moreover, it is involved in hypertrophy induction and cellular remodeling depending on the cardiac stress stimulus. Our new transgenic animals are valuable models for reconsideration of CTGF's profibrotic function in the heart.

Beyond the sarcomere: CSRP3 mutations cause hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is a frequent genetic cardiac disease and the most common cause of sudden cardiac death in young individuals. Most of the currently known HCM disease genes encode sarcomeric proteins. Previous studies have shown an association between CSRP3 missense mutations and either dilated cardiomyopathy (DCM) or HCM, but all these studies were unable to provide comprehensive genetic evidence for a causative role of CSRP3 mutations. We used linkage analysis and identified a CSRP3 missense mutation in a large German family affected by HCM. We confirmed CSRP3 as an HCM disease gene. Furthermore, CSRP3 missense mutations segregating with HCM were identified in four other families. We used a newly designed monoclonal antibody to show that muscle LIM protein (MLP), the protein encoded by CSRP3, is mainly a cytosolic component of cardiomyocytes and not tightly anchored to sarcomeric structures. Our functional data from both in vitro and in vivo analyses suggest that at least one of MLP's mutated forms seems to be destabilized in the heart of HCM patients harbouring a CSRP3 missense mutation. We also present evidence for mild skeletal muscle disease in affected persons. Our results support the view that HCM is not exclusively a sarcomeric disease and also suggest that impaired mechano-sensory stress signalling might be involved in the pathogenesis of HCM.

Expression of the protein phosphatase 1 inhibitor KEPI is downregulated in breast cancer cell lines and tissues and involved in the regulation of the tumor suppressor EGR1 via the MEK-ERK pathway.

KEPI is a protein kinase C-potentiated inhibitory protein for type 1 Ser/Thr protein phosphatases. We found no or reduced expression of KEPI in breast cancer cell lines, breast tumors and metastases in comparison to normal breast cell lines and tissues, respectively. KEPI protein expression and ubiquitous localization was detected with a newly generated antibody. Ectopic KEPI expression in MCF7 breast cancer cells induced differential expression of 95 genes, including the up-regulation of the tumor suppressors EGR1 (early growth response 1) and PTEN (phosphatase and tensin homolog), which is regulated by EGR1. We further show that the up-regulation of EGR1 in MCF7/KEPI cells is mediated by MEK-ERK signaling. The inhibition of this pathway by the MEK inhibitor UO126 led to a strong decrease in EGR1 expression in MCF7/KEPI cells. These results reveal a novel role for KEPI in the regulation of the tumor suppressor gene EGR1 via activation of the MEK-ERK MAPK pathway.

Mutations in the human muscle LIM protein gene in families with hypertrophic cardiomyopathy.

BACKGROUND: Muscle LIM protein (MLP) is an essential nuclear regulator of myogenic differentiation. Additionally, it may act as an integrator of protein assembly of the actin-based cytoskeleton. MLP-knockout mice develop a marked cardiac hypertrophy reaction and dilated cardiomyopathy (DCM). MLP is therefore a candidate gene for heritable forms of hypertrophic cardiomyopathy (HCM) and DCM in humans. METHODS AND RESULTS: We analyzed 1100 unrelated individuals (400 patients with DCM, 200 patients with HCM, and 500 controls) for mutations in the human CRP3 gene that encodes MLP. We found 3 different missense mutations in 3 unrelated patients with familial HCM but detected no mutation in the DCM group or the controls. All mutations predicted an amino acid exchange at highly conserved residues in the functionally important LIM1 domain, which is responsible for interaction with alpha-actinin and with certain muscle-specific transcription factors. Protein-binding studies indicate that mutations in the CRP3 gene lead to a decreased binding activity of MLP to alpha-actinin. All 3 index patients were characterized by typical asymmetrical septal hypertrophy. Family studies revealed cosegregation of clinically affected individuals with the respective mutations in MLP. CONCLUSION: Here, we present evidence that mutations in the CRP3/MLP gene can cause HCM.

ErbB2 pathways in heart and neural diseases.

The proto-oncogene ErbB2 (also known as c-neu or HER2 in humans) encodes a receptor tyrosine kinase that is frequently overexpressed in human tumors. It is the target of a novel and effective antibody-based therapy for malignant mammary tumors (trastuzumab/Herceptin). Biochemical and genetic experiments have shown that ErbB2 acts as a coreceptor for other members of the ErbB family of receptor tyrosine kinases. In particular, signals are transduced by ErbB2/ErbB4, ErbB2/ErbB3, and ErbB2/EGF receptor heteromers. ErbB2/4 and ErbB2/ErbB3 heteromers transmit neuregulin-1 signals in the developing and adult heart, and in the peripheral nervous system, respectively. Of particular medical relevance are recent findings that relied on tissue-specific mutation of ErbB2 in cardiomyocytes, which revealed an essential function of ErbB2 in normal heart physiology and demonstrated that loss of cardiac ErbB2 can cause dilated cardiomyopathy in adult mice. Thus, ErbB2 is important not only in development, but also for the correct functioning of the differentiated myocardium. The conditional ErbB2 mutant mice provide a model for the principal side effects--cardiomyopathy and heart failure--that can be observed in patients undergoing chemotherapy with Trastuzumab.

Conditional mutation of the ErbB2 (HER2) receptor in cardiomyocytes leads to dilated cardiomyopathy.

The ErbB2 (Her2) proto-oncogene encodes a receptor tyrosine kinase, which is frequently amplified and overexpressed in human tumors. ErbB2 provides the target for a novel and effective antibody-based therapy (Trastuzumab/Herceptin) used for the treatment of mammary carcinomas. However, cardiomyopathies develop in a proportion of patients treated with Trastuzumab, and the incidence of such complications is increased by combination with standard chemotherapy. Gene ablation studies have previously demonstrated that the ErbB2 receptor, together with its coreceptor ErbB4 and the ligand Neuregulin-1, are essential for normal development of the heart ventricle. We use here Cre-loxP technology to mutate ErbB2 specifically in ventricular cardiomyocytes. Conditional mutant mice develop a severe dilated cardiomyopathy, with signs of cardiac dysfunction generally appearing by the second postnatal month. We infer that signaling from the ErbB2 receptor, which is enriched in T-tubules in cardiomyocytes, is crucial for adult heart function. Conditional ErbB2 mutant mice provide a model of dilated cardiomyopathy. In particular, they will allow a rigorous assessment of the role of ErbB2 in the heart and provide insight into the molecular mechanisms that underlie the adverse effects of anti-ErbB2 antibodies.