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1.
Alpha and beta myosin isoforms and human atrial and ventricular contraction.
Walklate, J, Ferrantini, C, Johnson, CA, Tesi, C, Poggesi, C, Geeves, MA
Cellular and molecular life sciences : CMLS. 2021;(23):7309-7337
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Abstract
Human atrial and ventricular contractions have distinct mechanical characteristics including speed of contraction, volume of blood delivered and the range of pressure generated. Notably, the ventricle expresses predominantly β-cardiac myosin while the atrium expresses mostly the α-isoform. In recent years exploration of the properties of pure α- & β-myosin isoforms have been possible in solution, in isolated myocytes and myofibrils. This allows us to consider the extent to which the atrial vs ventricular mechanical characteristics are defined by the myosin isoform expressed, and how the isoform properties are matched to their physiological roles. To do this we Outline the essential feature of atrial and ventricular contraction; Explore the molecular structural and functional characteristics of the two myosin isoforms; Describe the contractile behaviour of myocytes and myofibrils expressing a single myosin isoform; Finally we outline the outstanding problems in defining the differences between the atria and ventricles. This allowed us consider what features of contraction can and cannot be ascribed to the myosin isoforms present in the atria and ventricles.
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2.
The role of long noncoding RNAs in atrial fibrillation.
Babapoor-Farrokhran, S, Gill, D, Rasekhi, RT
Heart rhythm. 2020;(6):1043-1049
Abstract
Atrial fibrillation (AF) is a common arrhythmia with serious clinical sequelae, yet little is known about its genetic origins. Recently, the untranscribed 98% of the human genome has been increasingly implicated in important processes such as cardiac organogenesis, physiology, and pathophysiology. Specifically, long noncoding RNAs (lncRNAs) have been shown to interact with the transcriptome in various ways that alter gene expression. Previously, multiple lncRNAs have been identified in disease processes such as heart failure, coronary artery disease, and diabetes. Multiple studies now show lncRNAs are involved in each fundamental mechanism leading to the development of AF, including structural remodeling, electrical remodeling, renin angiotensin system effects, and calcium handling abnormalities. The altered expression of lncRNAs offers genetic targets for the diagnosis and treatment of AF. This article discusses the role of lncRNAs in AF and its pathogenesis.
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3.
Atrial high-rate episodes: prevalence, stroke risk, implications for management, and clinical gaps in evidence.
Bertaglia, E, Blank, B, Blomström-Lundqvist, C, Brandes, A, Cabanelas, N, Dan, GA, Dichtl, W, Goette, A, de Groot, JR, Lubinski, A, et al
Europace : European pacing, arrhythmias, and cardiac electrophysiology : journal of the working groups on cardiac pacing, arrhythmias, and cardiac cellular electrophysiology of the European Society of Cardiology. 2019;(10):1459-1467
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Abstract
Self-terminating atrial arrhythmias are commonly detected on continuous rhythm monitoring, e.g. by pacemakers or defibrillators. It is unclear whether the presence of these arrhythmias has therapeutic consequences. We sought to summarize evidence on the prevalence of atrial high-rate episodes (AHREs) and their impact on risk of stroke. We performed a comprehensive, tabulated review of published literature on the prevalence of AHRE. In patients with AHRE, but without atrial fibrillation (AF), we reviewed the stroke risk and the potential risk/benefit of oral anticoagulation. Atrial high-rate episodes are found in 10-30% of AF-free patients. Presence of AHRE slightly increases stroke risk (0.8% to 1%/year) compared with patients without AHRE. Atrial high-rate episode of longer duration (e.g. those >24 h) could be associated with a higher stroke risk. Oral anticoagulation has the potential to reduce stroke risk in patients with AHRE but is associated with a rate of major bleeding of 2%/year. Oral anticoagulation is not effective in patients with heart failure or survivors of a stroke without AF. It remains unclear whether anticoagulation is effective and safe in patients with AHRE. Atrial high-rate episodes are common and confer a slight increase in stroke risk. There is true equipoise on the best way to reduce stroke risk in patients with AHRE. Two ongoing trials (NOAH-AFNET 6 and ARTESiA) will provide much-needed information on the effectiveness and safety of oral anticoagulation using non-vitamin K antagonist oral anticoagulants in patients with AHRE.
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4.
Effects of novel oral anticoagulants on left atrial and left atrial appendage thrombi: an appraisal.
Marsico, F, Cecere, M, Parente, A, Paolillo, S, de Martino, F, Dellegrottaglie, S, Trimarco, B, Perrone Filardi, P
Journal of thrombosis and thrombolysis. 2017;(2):139-148
Abstract
Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and predisposes to an increased risk of thromboembolic events. Patients affected by AF exhibit an increased risk of stroke compared with those in sinus rhythm, with the most common location of thrombi in the left atrial appendage. Until 2009, warfarin and other vitamin K antagonists were the only class of oral anticoagulants available. More recently, dabigatran, rivaroxaban, apixaban, and edoxaban have been approved by regulatory authorities for prevention of stroke in patients with non-valvular AF. Few data are available about the efficacy of novel oral anticoagulants for the treatment of left atrial and left atrial appendage thrombosis. Aim of this review is to summarize available evidence regarding the effectiveness of novel oral anticoagulants on left atrial appendage thrombosis.
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5.
EHRA/HRS/APHRS/SOLAECE expert consensus on atrial cardiomyopathies: Definition, characterization, and clinical implication.
Goette, A, Kalman, JM, Aguinaga, L, Akar, J, Cabrera, JA, Chen, SA, Chugh, SS, Corradi, D, D'Avila, A, Dobrev, D, et al
Heart rhythm. 2017;(1):e3-e40
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6.
Human atrial cell models to analyse haemodialysis-related effects on cardiac electrophysiology: work in progress.
Passini, E, Genovesi, S, Severi, S
Computational and mathematical methods in medicine. 2014;:291598
Abstract
During haemodialysis (HD) sessions, patients undergo alterations in the extracellular environment, mostly concerning plasma electrolyte concentrations, pH, and volume, together with a modification of sympathovagal balance. All these changes affect cardiac electrophysiology, possibly leading to an increased arrhythmic risk. Computational modeling may help to investigate the impact of HD-related changes on atrial electrophysiology. However, many different human atrial action potential (AP) models are currently available, all validated only with the standard electrolyte concentrations used in experiments. Therefore, they may respond in different ways to the same environmental changes. After an overview on how the computational approach has been used in the past to investigate the effect of HD therapy on cardiac electrophysiology, the aim of this work has been to assess the current state of the art in human atrial AP models, with respect to the HD context. All the published human atrial AP models have been considered and tested for electrolytes, volume changes, and different acetylcholine concentrations. Most of them proved to be reliable for single modifications, but all of them showed some drawbacks. Therefore, there is room for a new human atrial AP model, hopefully able to physiologically reproduce all the HD-related effects. At the moment, work is still in progress in this specific field.
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7.
Echocardiographic examination of the posterior atrioventricular groove.
Silbiger, JJ
Echocardiography (Mount Kisco, N.Y.). 2014;(2):223-33
Abstract
Abnormalities of the posterior atrioventricular (AV) groove may be mischaracterized or overlooked in the course of routine echocardiographic imaging. Vascular abnormalities in this location include plethora of the coronary sinus and ectasia of the circumflex coronary artery. Excess accumulation of calcium (mitral annular calcification) and of fat (lipomatosis of the posterior AV groove) may also occur in this region. Masses (tumors or thrombus) arising from the floor of the left atrium or extrinsic to it (hiatal hernia, lymph nodes) may occupy the posterior AV groove. Abnormalities of the left ventricle, including aneurysms and pseudoaneurysms may present as masses in the posterior AV groove. This article discusses the echocardiographic features, differential diagnosis, and clinical significance of these abnormalities.
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8.
[Morphological and molecular bases of cardiac development].
Kobylińska, J, Dworzański, W, Cendrowska-Pinkosz, M, Dworzańska, A, Hermanowicz-Dryka, T, Kiszka, J, Starosławska, E, Burdan, F
Postepy higieny i medycyny doswiadczalnej (Online). 2013;:950-7
Abstract
The heart is a mesoderm-derived organ, whose formation is regulated by various genes. Initially, the most important is expression of Nkx2.5, CR1, pitx2, anf and mhc2a, which are responsible for differentiation of cardiomyocytes. In a later phase activation of mhc2b, pitx2c, mesp1, pcmf1, vmhc, xin, mcl2v, mlc2a, mlc2a, mef2, hand1 and hand2 was revealed. Their expression is regulated by various molecules, including transcription (XIN, GATA, MEF, Tbx5, Baf60c, PECAM, tie-2, MEF2) and growth (VEGF, FGF, PDGF) factors, as well as proteins (i.e., dickkopf-1, cerberus, cytotactin, fibrillin, nodal, thrombomodulin, Wnt, bone morphometric ones - BMP2, BMP 4, BMP5, BMP7) and other substances, such as retinoid and folic acid. Crucial steps in cardiac organogenesis are development of the ventricle and atrial formation, as well as septation and valve formation. Any disturbances of such processes may lead to various congenital heart diseases and defects that could be initiated by various genetic, epigenetic or environmental factors. The most common heart malformations are: stenosis (coarctation) of the aorta and pulmonary trunk, bicuspid aortic valve, atrial and/or ventricular septal defect, persistent truncus arteriosus (Botallo duct), transposition of the great vessels, tricuspid atresia, hypoplastic left and right heart, as well as syndrome of Lutembachera, Cantrell, Ebstein, Eisenmenger and Shone and trilogy, tetralogy, pentalogy of Fallot.
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9.
Alterations of atrial Ca(2+) handling as cause and consequence of atrial fibrillation.
Greiser, M, Lederer, WJ, Schotten, U
Cardiovascular research. 2011;(4):722-33
Abstract
Atrial fibrillation (AF) is the most prevalent sustained arrhythmia. As the most important risk factor for embolic stroke, AF is associated with a high morbidity and mortality. Despite decades of research, successful (pharmacological and interventional) 'ablation' of the arrhythmia remains challenging. AF is characterized by a diverse aetiology, including heart failure, hypertension, and valvular disease. Based on this understanding, new treatment strategies that are specifically tailored to the underlying pathophysiology of a certain 'type' of AF are being developed. One important aspect of AF pathophysiology is altered intracellular Ca(2+) handling. Due to the increase in the atrial activation rate and the subsequent initial [Ca(2+)](i) overload, AF induces 'remodelling' of intracellular Ca(2+) handling. Current research focuses on unravelling the contribution of altered intracellular Ca(2+) handling to different types of AF. More specifically, changes in intracellular Ca(2+) homeostasis preceding the onset of AF, in conditions which predispose to AF (e.g. heart failure), appear to be different from changes in Ca(2+) handling developing after the onset of AF. Here we review and critique altered intracellular Ca(2+) handling and its contribution to three specific aspects of AF pathophysiology, (i) excitation-transcription coupling and Ca(2+)-dependent signalling pathways, (ii) atrial contractile dysfunction, and (iii) arrhythmogenicity.
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10.
Atrial remodeling in atrial fibrillation and some related microRNAs.
Sharma, D, Li, G, Xu, G, Liu, Y, Xu, Y
Cardiology. 2011;(2):111-21
Abstract
Atrial fibrillation is the most common sustained arrhythmia associated with substantial cardiovascular morbidity and mortality, with stroke being the most critical complication. The role of atrial remodeling has emerged as the new pathophysiological mechanism of atrial fibrillation. Electrical remodeling and structural remodeling will increase the probability of generating multiple atrial wavelets by enabling rapid atrial activation and dispersion of refractoriness. MicroRNAs (miRNAs) are small non-coding RNAs of 20-25 nucleotides in length that regulate expression of target genes through sequence-specific hybridization to the 3' untranslated region of messenger RNAs and either block translation or direct degradation of their target messenger RNA. They have also been implicated in a variety of pathological conditions, such as arrhythmogenesis and atrial fibrillation. Target genes of miRNAs have the potential to affect atrial fibrillation vulnerability.