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Ventricular depolarization

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https://www.readbyqxmd.com/read/29029613/right-precordial-directed-electrocardiographical-markers-identify-arrhythmogenic-right-ventricular-cardiomyopathy-in-the-absence-of-conventional-depolarization-or-repolarization-abnormalities
#1
Daniel Cortez, Anneli Svensson, Jonas Carlson, Sharon Graw, Nandita Sharma, Francesca Brun, Anita Spezzacatene, Luisa Mestroni, Pyotr G Platonov
BACKGROUND: Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) carries a risk of sudden death. We aimed to assess whether vectorcardiographic (VCG) parameters directed toward the right heart and a measured angle of the S-wave would help differentiate ARVD/C with otherwise normal electrocardiograms from controls. METHODS: Task Force 2010 definite ARVD/C criteria were met for all patients. Those who did not fulfill Task Force depolarization or repolarization criteria (-ECG) were compared with age and gender-matched control subjects...
October 13, 2017: BMC Cardiovascular Disorders
https://www.readbyqxmd.com/read/29016731/electrical-coupling-between-ventricular-myocytes-and-myofibroblasts-in-the-infarcted-mouse-heart
#2
Michael Rubart, Wen Tao, Xiao-Long Lu, Simon J Conway, Sean P Reuter, Shien-Fong Lin, Mark H Soonpaa
Aims: Recent studies have demonstrated electrotonic coupling between scar tissue and the surrounding myocardium in cryoinjured hearts. However, the electrical dynamics occurring at the myocyte-nonmyocyte interface in the fibrotic heart remain undefined. Here, we sought to develop an assay to interrogate the nonmyocyte cell type contributing to heterocellular coupling and to characterize, on a cellular scale, its voltage response in the infarct border zone of living hearts. Methods and results: We used two-photon laser scanning microscopy in conjunction with a voltage-sensitive dye to record transmembrane voltage changes simultaneously from cardiomyocytes and adjoined nonmyocytes in Langendorff-perfused mouse hearts with healing myocardial infarction...
September 1, 2017: Cardiovascular Research
https://www.readbyqxmd.com/read/28970285/calcium-dependent-arrhythmogenic-foci-created-by-weakly-coupled-myocytes-in-the-failing-heart
#3
Di Lang, Daisuke Sato, Yan Jiang, Kenneth S Ginsburg, Crystal M Ripplinger, Donald M Bers
Rationale: Intercellular uncoupling and Ca mishandling can initiate triggered ventricular arrhythmias. Spontaneous Ca release activates inward current which depolarizes membrane potential (Vm) and can trigger action potentials in isolated myocytes. However, cell-cell coupling in intact hearts limits local depolarization and may protect hearts from this arrhythmogenic mechanism. Traditional optical mapping lacks the spatial resolution to assess coupling of individual myocytes. Objective: We investigate local intercellular coupling in Ca-induced depolarization in intact hearts, using confocal microscopy to measure local Vm and intracellular [Ca(2+)] ([Ca]i) simultaneously...
October 2, 2017: Circulation Research
https://www.readbyqxmd.com/read/28958063/efficacy-of-esmolol-cardioplegia-during-hypothermic-ischaemia
#4
Dai Nishina, David J Chambers
OBJECTIVES: Cardioplegic arrest using a polarizing solution has been shown to have beneficial advantages for cardioprotection compared with depolarizing (potassium-based) arrest; most studies, however, have looked at normothermic ischaemia with short infusion intervals (every 10-15 min). This study examines the protective efficacy of an esmolol-based cardioplegia during hypothermic arrest, together with a prolonged infusion interval (30 min) for increased clinical feasibility. METHODS: Isolated Langendorff-perfused hearts were subjected to arrest with St Thomas' Hospital cardioplegia (STH2), or esmolol cardioplegia (single- or multidose infusion at 32°C) for 60-min, 90-min or 120-min global ischaemia at 32°C, and recovery of function (left ventricular developed pressure) measured...
September 2, 2017: European Journal of Cardio-thoracic Surgery
https://www.readbyqxmd.com/read/28955244/human-in-silico-drug-trials-demonstrate-higher-accuracy-than-animal-models-in-predicting-clinical-pro-arrhythmic-cardiotoxicity
#5
Elisa Passini, Oliver J Britton, Hua Rong Lu, Jutta Rohrbacher, An N Hermans, David J Gallacher, Robert J H Greig, Alfonso Bueno-Orovio, Blanca Rodriguez
Early prediction of cardiotoxicity is critical for drug development. Current animal models raise ethical and translational questions, and have limited accuracy in clinical risk prediction. Human-based computer models constitute a fast, cheap and potentially effective alternative to experimental assays, also facilitating translation to human. Key challenges include consideration of inter-cellular variability in drug responses and integration of computational and experimental methods in safety pharmacology. Our aim is to evaluate the ability of in silico drug trials in populations of human action potential (AP) models to predict clinical risk of drug-induced arrhythmias based on ion channel information, and to compare simulation results against experimental assays commonly used for drug testing...
2017: Frontiers in Physiology
https://www.readbyqxmd.com/read/28948234/mechanisms-underlying-epicardial-radiofrequency-ablation-to-suppress-arrhythmogenesis-in-experimental-models-of-brugada-syndrome
#6
Bence Patocskai, Namsik Yoon, Charles Antzelevitch
OBJECTIVES: This study sought to test the hypothesis that elimination of sites of abnormal repolarization, via epicardial RFA, suppresses the electrocardiographic and arrhythmic manifestations of BrS. BACKGROUND: Brugada syndrome (BrS) is associated with ventricular tachycardia and ventricular fibrillation leading to sudden cardiac death. Nademanee et al. reported that radiofrequency ablation (RFA) of right ventricular outflow tract epicardium significantly reduced the electrocardiogram and arrhythmic manifestations of BrS...
April 2017: JACC. Clinical Electrophysiology
https://www.readbyqxmd.com/read/28939505/impact-of-waterborne-and-trophic-mercury-exposures-on-cardiac-function-of-two-ecologically-distinct-neotropical-freshwater-fish-brycon-amazonicus-and-hoplias-malabaricus
#7
Diana A Monteiro, Edwin W Taylor, Francisco T Rantin, Ana L Kalinin
Metal pollutants have been considered one of the main factors underlying the depletion of biodiversity in natural populations unbalancing aquatic environments. The aim of this study was to evaluate the effects of exposure to inorganic Hg on myocardial contractility and the electrocardiogram (ECG) of two ecologically distinct Neotropical fish species, namely: matrinxã (Brycon amazonicus) and trahira (Hoplias malabaricus). Matrinxãs were exposed to a sublethal concentration of 0.1mgL(-1) of Hg in water for 96h...
September 20, 2017: Comparative Biochemistry and Physiology. Toxicology & Pharmacology: CBP
https://www.readbyqxmd.com/read/28901628/total-cosine-r-to-t-for-predicting-ventricular-arrhythmic-and-mortality-outcomes-a-systematic-review-and-meta-analysis
#8
Gary Tse, Mengqi Gong, Cheuk Wai Wong, Cynthia Chan, Stamatis Georgopoulos, Yat Sun Chan, Bryan P Yan, Guangping Li, Paula Whittaker, Ana Ciobanu, Sadeq Ali-Hasan-Al-Saegh, Sunny H Wong, William K K Wu, George Bazoukis, Konstantinos Lampropoulos, Wing Tak Wong, Lap Ah Tse, Adrian M Baranchuk, Konstantinos P Letsas, Tong Liu
BACKGROUND: The total cosine R-to-T (TCRT), a vectorcardiographic marker reflecting the spatial difference between the depolarization and repolarization wavefronts, has been used to predict ventricular tachycardia/fibrillation (VT/VF) and sudden cardiac death (SCD) in different clinical settings. However, its prognostic value has been controversial. OBJECTIVE: This systematic review and meta-analysis evaluated the significance of TRCT in predicting arrhythmic and/or mortality endpoints...
September 12, 2017: Annals of Noninvasive Electrocardiology
https://www.readbyqxmd.com/read/28877886/pulmonary-right-ventricular-resynchronization-in-congenital-heart-disease-acute-improvement-in-right-ventricular-mechanics-and-contraction-efficiency
#9
Jan Janoušek, Jan Kovanda, Miroslav Ložek, Viktor Tomek, Pavel Vojtovič, Roman Gebauer, Peter Kubuš, Miroslav Krejčíř, Joost Lumens, Tammo Delhaas, Frits Prinzen
BACKGROUND: Electromechanical discoordination may contribute to long-term pulmonary right ventricular (RV) dysfunction in patients after surgery for congenital heart disease. We sought to evaluate changes in RV function after temporary RV cardiac resynchronization therapy. METHODS AND RESULTS: Twenty-five patients aged median 12.0 years after repair of tetralogy of Fallot and similar lesions were studied echocardiographically (n=23) and by cardiac catheterization (n=5) after primary repair (n=4) or after surgical RV revalvulation for significant pulmonary regurgitation (n=21)...
September 2017: Circulation. Cardiovascular Imaging
https://www.readbyqxmd.com/read/28869925/cadmium-stress-assessment-based-on-the-electrocardiogram-characteristics-of-zebra-fish-danio-rerio-qrs-complex-could-play-an-important-role
#10
Na Xing, Lizhen Ji, Jie Song, Jingchun Ma, Shangge Li, Zongming Ren, Fei Xu, Jianping Zhu
The electrocardiogram (ECG) of zebra fish (Danio rerio) expresses cardiac features that are similar to humans. Here we use sharp microelectrode measurements to obtain ECG characteristics in adult zebra fish and analyze the effects of cadmium chloride (CdCl2) on the heart. We observe the overall changes of ECG parameters in different treatments (0.1 TU, 0.5 TU and 1.0 TU CdCl2), including P wave, Q wave, R wave, S wave, T wave, PR interval (atrial contraction), QRS complex (ventricular depolarization), ST segment, and QT interval (ventricular repolarization)...
August 31, 2017: Aquatic Toxicology
https://www.readbyqxmd.com/read/28868038/quantitative-comparison-of-effects-of-dofetilide-sotalol-quinidine-and-verapamil-between-human-ex-vivo-trabeculae-and-in-silico-ventricular-models-incorporating-inter-individual-action-potential-variability
#11
Oliver J Britton, Najah Abi-Gerges, Guy Page, Andre Ghetti, Paul E Miller, Blanca Rodriguez
Background:In silico modeling could soon become a mainstream method of pro-arrhythmic risk assessment in drug development. However, a lack of human-specific data and appropriate modeling techniques has previously prevented quantitative comparison of drug effects between in silico models and recordings from human cardiac preparations. Here, we directly compare changes in repolarization biomarkers caused by dofetilide, dl-sotalol, quinidine, and verapamil, between in silico populations of human ventricular cell models and ex vivo human ventricular trabeculae...
2017: Frontiers in Physiology
https://www.readbyqxmd.com/read/28858645/simulation-study-of-the-ionic-mechanisms-underlying-torsade-de-pointes-in-a-2d-cardiac-tissue
#12
Ponnuraj Kirthi Priya, M Ramasubba Reddy
BACKGROUND: To understand the ionic mechanism behind the genesis of Torsade de Pointes (TdP) occurring with long QT syndrome 2 (LQTS2) in a remodelled transmural tissue. METHODS: The TP06 model is used to simulate the electrical activity of cells in a 2D transmural ventricular model. LQTS2 is realised by reducing the potassium current (IKr) to 0.5 in each cell. Each cell of the tissue is remodelled by increasing the conductance of calcium current (GCaL). The above two factors make the cells prone to early after depolarizations (EADs) development...
August 24, 2017: Computers in Biology and Medicine
https://www.readbyqxmd.com/read/28846146/paroxysmal-atrioventricular-block-electrophysiological-mechanism-of-phase-4-conduction-block-in-the-his-purkinje-system-a-comparison-with-phase-3-block
#13
Mohammad Shenasa, Mark E Josephson, Andrew L Wit
BACKGROUND: Paroxysmal atrioventricular (A-V) block is relatively rare, and due to its transient nature, it is often under recognized. It is often triggered by atrial, junctional, or ventricular premature beats, and occurs in the presence of a diseased His-Purkinje system (HPS). Here, we present a 45-year-old white male who was admitted for observation due to recurrent syncope and near-syncope, who had paroxysmal A-V block. The likely cellular electrophysiological mechanisms(s) of paroxysmal A-V block and its differential diagnosis and management are discussed...
August 28, 2017: Pacing and Clinical Electrophysiology: PACE
https://www.readbyqxmd.com/read/28838552/normal-ventricular-repolarization-and-qt-interval-ionic-background-modifiers-and-measurements
#14
REVIEW
Emanuela T Locati, Giuseppe Bagliani, Luigi Padeletti
The QT interval on surface electrocardiogram represents the sum of depolarization and repolarization process of the ventricles. The ventricular recovery process, reflected by ST segment and T wave, mainly depends on the transmembrane outward transport of potassium ions to reestablish the endocellular electronegativity. Outward potassium channels represent a heterogeneous family of ionic carriers, whose global kinetics is modulated by heart rate and autonomic nervous activity. Several cardiac and noncardiac drugs and disease conditions, and several mutations of genes encoding ionic channels, generating distinct genetic channellopathies, may affect the ventricular repolarization, provoke QT interval prolongation and shortening, and increase the susceptibility to ventricular arrhythmias...
September 2017: Cardiac Electrophysiology Clinics
https://www.readbyqxmd.com/read/28838550/the-qrs-complex-normal-activation-of-the-ventricles
#15
REVIEW
Giuseppe Bagliani, Roberto De Ponti, Carola Gianni, Luigi Padeletti
The ventricular conduction system starts below the His bundle, where it bifurcates into the right and left bundle branches that taper out to the subendocardial Purkinje network, which activates the ventricular myocardium. This system is responsible for the synchronized and almost simultaneous activation of both ventricles. On the surface electrocardiogram, the ventricular conduction system lies in the terminal portion of the PR interval, whereas the QRS complex composed of the electrical currents originating from ventricular depolarization...
September 2017: Cardiac Electrophysiology Clinics
https://www.readbyqxmd.com/read/28830271/the-acute-toxic-effects-of-silver-nanoparticles-on-myocardial-transmembrane-potential-ina-and-ik1-channels-and-heart-rhythm-in-mice
#16
Cai-Xia Lin, Su-Yu Yang, Jing-Li Gu, Jie Meng, Hai-Yan Xu, Ji-Min Cao
This study focused on the potential toxicity of silver nanoparticles (AgNPs) on cardiac electrophysiology which is rarely investigated. We found that AgNPs (10(-9)-10(-6 )g/ml) concentration-dependently depolarized the resting potential, diminished the action potential, and finally led to loss of excitability in mice cardiac papillary muscle cells in vitro. In cultured neonatal mice cardiomyocytes, AgNPs (10(-9)-10(-7 )g/ml) concentration-dependently decreased the Na(+) currents (INa), accelerated the activation, and delayed the inactivation and recovery of Na(+) channels from inactivation within 5 min...
August 23, 2017: Nanotoxicology
https://www.readbyqxmd.com/read/28815597/cardiac-action-potential-repolarization-re-visited-early-repolarization-shows-all-or-none-behaviour
#17
Beatriz Trenor, Karen Cardona, Javier Saiz, Denis Noble, Wayne Giles
In healthy mammalian hearts the action potential (AP) waveform initiates and modulates each contraction, or heartbeat. As a result, action potential height and duration are key physiological variables. In addition, rate-dependent changes in ventricular action potential duration (APD), and variations in APD at a fixed heart rate, are both reliable biomarkers of electrophysiological stability. Present guidelines for the likelihood that candidate drugs will increase arrhythmias rely on small changes in APD and Q-T intervals as criteria for Safety Pharmacology decisions...
August 17, 2017: Journal of Physiology
https://www.readbyqxmd.com/read/28764153/correlation-of-adiposity-indices-with-electrocardiographic-ventricular-variables-and-vascular-stiffness-in-young-adults
#18
Varrshine Ravikumar, Hemamalini Ramasamy VajraVelu, Saravanan Ayyavoo, Balaji Ramraj
INTRODUCTION: Excess adiposity constitute an important public health problem because of the associated increased risk of hypertension, coronary heart disease, type 2 diabetes and other disorders. Not only the contribution of general measures of adiposity but also central measures of adiposity have been observed. AIM: To compare and correlate the central and general adiposity indices with ventricular electrocardiographic variables and vascular stiffness indices in normal, overweight and obese young adults...
June 2017: Journal of Clinical and Diagnostic Research: JCDR
https://www.readbyqxmd.com/read/28743749/sumoylation-determines-the-voltage-required-to-activate-cardiac-iks-channels
#19
Dazhi Xiong, Tian Li, Hui Dai, Anthony F Arena, Leigh D Plant, Steve A N Goldstein
IKs channels open in response to depolarization of the membrane voltage during the cardiac action potential, passing potassium ions outward to repolarize ventricular myocytes and end each beat. Here, we show that the voltage required to activate IKs channels depends on their covalent modification by small ubiquitin-like modifier (SUMO) proteins. IKs channels are comprised of four KCNQ1 pore-forming subunits, two KCNE1 accessory subunits, and up to four SUMOs, one on Lys424 of each KCNQ1 subunit. Each SUMO shifts the half-maximal activation voltage (V1/2) of IKs ∼ +8 mV, producing a maximal +34-mV shift in neonatal mouse cardiac myocytes or Chinese hamster ovary (CHO) cells expressing the mouse or human subunits...
August 8, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28710068/gq-activated-fibroblasts-induce-cardiomyocyte-action-potential-prolongation-and-automaticity-in-a-three-dimensional-microtissue-environment
#20
C M Kofron, T Y Kim, M E King, A Xie, F Feng, E Park, Z Qu, B-R Choi, U Mende
Cardiac fibroblasts (CFs) are known to regulate cardiomyocyte (CM) function in vivo and in two-dimensional in vitro cultures. This study examined the effect of CF activation on the regulation of CM electrical activity in a three-dimensional (3-D) microtissue environment. Using a scaffold-free 3-D platform with interspersed neonatal rat ventricular CMs and CFs, Gq-mediated signaling was selectively enhanced in CFs by Gαq adenoviral infection before coseeding with CMs in nonadhesive hydrogels. After 3 days, the microtissues were analyzed by signaling assay, histological staining, quantitative PCR, Western blots, optical mapping with voltage- or Ca(2+)-sensitive dyes, and microelectrode recordings of CF resting membrane potential (RMPCF)...
October 1, 2017: American Journal of Physiology. Heart and Circulatory Physiology
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