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https://www.readbyqxmd.com/read/28619993/low-extracellular-potassium-prolongs-repolarization-and-evokes-early-afterdepolarization-in-human-induced-pluripotent-stem-cell-derived-cardiomyocytes
#1
Jukka Kuusela, Kim Larsson, Disheet Shah, Chandra Prajapati, Katriina Aalto-Setälä
Long QT syndrome (LQTS) is characterized by a prolonged QT-interval on electrocardiogram and by increased risk of sudden death. One of the most common and potentially life-threatening electrolyte disturbances is hypokalemia, characterized by low concentrations of K(+) Using a multielectrode array platform and current clamp technique, we investigated the effect of low extracellular K(+) concentration ([K(+)]Ex) on the electrophysiological properties of hiPSC-derived cardiomyocytes (CMs) generated from a healthy control subject (WT) and from two symptomatic patients with type 1 of LQTS carrying G589D (LQT1A) or IVS7-2A>G mutation (LQT1B) in KCNQ1 The baseline prolongations of field potential durations (FPDs) and action potential durations (APDs) were longer in LQT1-CMs than in WT-CMs...
June 15, 2017: Biology Open
https://www.readbyqxmd.com/read/28607621/epicardially-placed-implantable-cardioverter-defibrillator-for-a-child-with-congenital-long-qt-syndrome
#2
Hirotaro Sugiyama, Motomi Tachibana, Hiroshi Morita, Nobuhiro Nishii, Akihito Miyoshi, Hiroyasu Sugiyama, Koji Nakagawa, Atsuyuki Watanabe, Kazufumi Nakamura, Hiroshi Ito
A 7-year-old boy presented at our hospital with syncope. At birth, electrocardiography had shown a long QT interval with torsade de pointes (TdP). Congenital long QT syndrome (LQTS) had been diagnosed by genetic testing, and was successfully controlled with oral propranolol. At age 7, TdP had recurred with syncope. Electrocardiography revealed a prominent long QT interval with T-wave alternans. The propranolol dose was increased, but TdP remained uncontrolled. A cardioverter-defibrillator (ICD) was implanted epicardially, and TdP completely resolved with atrial pacing...
June 2017: Journal of Arrhythmia
https://www.readbyqxmd.com/read/28606656/divergent-antiarrhythmic-effects-of-resveratrol-and-piceatannol-in-a-whole-heart-model-of-long-qt-syndrome
#3
Christian Ellermann, Julian Wolfes, Simon Kochhäuser, Dirk G Dechering, Florian Reinke, Kristina Wasmer, Lars Eckardt, Gerrit Frommeyer
BACKGROUND: The polyphenol resveratrol and its metabolite piceatannol have beneficial health effects including antiarrhythmic properties in ischemia/reperfusion. The objective of this study was to determine potential antiarrhythmic effects in acquired long-QT-syndrome (LQTS). METHODS AND RESULTS: 26 rabbit hearts were isolated and Langendorff-perfused. The IKr-blocker sotalol (100μM) was infused to mimic LQTS-2. Hearts were assigned to two groups. Sotalol significantly prolonged action potential duration (APD90) and QT-interval in both groups (group 1:APD90: +18ms, p<0...
June 3, 2017: International Journal of Cardiology
https://www.readbyqxmd.com/read/28595573/a-novel-kcnq1-nonsense-variant-in-the-isoform-specific-first-exon-causes-both-jervell-and-lange-nielsen-syndrome-1-and-long-qt-syndrome-1-a-case-report
#4
Motoi Nishimura, Marehiko Ueda, Ryota Ebata, Emi Utsuno, Takuma Ishii, Kazuyuki Matsushita, Osamu Ohara, Naoki Shimojo, Yoshio Kobayashi, Fumio Nomura
BACKGROUND: According to previous KCNQ1 (potassium channel, voltage gated, KQT-like subfamily, member 1) gene screening studies, missense variants, but not nonsense or frame-shift variants, cause the majority of long QT syndrome (LQTS; Romano-Ward syndrome [RWS]) 1 cases. Several missense variants are reported to cause RWS by a dominant-negative mechanism, and some KCNQ1 variants can cause both Jervell and Lange-Nielsen Syndrome (JLNS; in an autosomal recessive manner) and LQTS1 (in an autosomal dominant manner), while other KCNQ1 variants cause only JLNS...
June 8, 2017: BMC Medical Genetics
https://www.readbyqxmd.com/read/28575668/cryo-em-structure-of-a-kcnq1-cam-complex-reveals-insights-into-congenital-long-qt-syndrome
#5
Ji Sun, Roderick MacKinnon
KCNQ1 is the pore-forming subunit of cardiac slow-delayed rectifier potassium (IKs) channels. Mutations in the kcnq1 gene are the leading cause of congenital long QT syndrome (LQTS). Here, we present the cryoelectron microscopy (cryo-EM) structure of a KCNQ1/calmodulin (CaM) complex. The conformation corresponds to an "uncoupled," PIP2-free state of KCNQ1, with activated voltage sensors and a closed pore. Unique structural features within the S4-S5 linker permit uncoupling of the voltage sensor from the pore in the absence of PIP2...
June 1, 2017: Cell
https://www.readbyqxmd.com/read/28559636/treating-an-adolescent-with-long-qt-syndrome-for-bipolar-disorder-a-case-presentation
#6
Özlem Önen, Ayşe Kutlu, Handan Özek Erkuran
OBJECTIVES: Long QT syndrome (LQTS) is described as the development of sudden syncope attacks or death as a result of ventricular tachycardia (VT) episodes that might be observed as elongated QT interval in electrocardiography (ECG). Implantable Cardioverter Defibrillator (ICD) is recommended as first-line treatment for the condition in guidelines. We aimed to present an adolescent recently diagnosed with Bipolar Disorder (BD) who had LQTS that was treated with ICD, discussing her follow up and treatment along with relevant literature...
January 26, 2017: Psychopharmacology Bulletin
https://www.readbyqxmd.com/read/28532774/genotype-positive-long-qt-syndrome-in-patients-with-coexisting-congenital-heart-disease
#7
Mohammed A Ebrahim, Matthew R Williams, Suzanne Shepard, James C Perry
Congenital long QT syndrome (LQTS) is characterized by QT prolongation with predisposition to life-threatening arrhythmia. There have been sporadic reports of LQTS coexisting with more common forms of congenital heart disease (CHD). However, the diagnosis of LQTS when CHD is present may be confounded by several common variables including postoperative electromechanical factors predisposing to ventricular arrhythmia, intrinsic, and postoperative QRS abnormalities. This report documents a single-center experience with patients who have both genetically confirmed LQTS and CHD to examine their modes of presentation and factors associated with making the diagnosis of LQTS in this patient population, as well as potential confounding variables that may mask or delay both LQTS diagnosis and initiation of therapy...
July 15, 2017: American Journal of Cardiology
https://www.readbyqxmd.com/read/28521025/mechanism-of-as2o3-induced-action-potential-prolongation-and-using-hips-cms-to-evaluate-the-rescue-efficacy-of-drugs-with-different-rescue-mechanism
#8
Meng Yan, Lifang Feng, Yanhui Shi, Junnan Wang, Yan Liu, Fengmei Li, Baoxin Li
Arsenic trioxide (As2O3) has been verified as a breakthrough in the management of acute promyelocytic leukemia in recent decades. However, cardiotoxicity, especially long QT syndrome (LQTS) has become the most important issue during As2O3 treatment. The characterized mechanisms behind this adverse effect are inhibition of cardiac hERG channel trafficking and increase of cardiac calcium currents. In our study, we found a new pathway underlying As2O3-induced cardiotoxicity that As2O3 accelerates lysosomal degradation of hERG on plasma membrane after using brefeldin A (BFA) to block protein trafficking...
May 17, 2017: Toxicological Sciences: An Official Journal of the Society of Toxicology
https://www.readbyqxmd.com/read/28499268/first-universal-pharmacophore-model-for-herg1-k-channel-activators-acther
#9
Serdar Durdagi, Ismail Erol, Ramin Ekhteiari Salmas, Matthew Patterson, Sergei Y Noskov
The intra-cavitary drug blockade of hERG1 channel has been extensively studied, both experimentally and theoretically. Structurally diverse ligands inadvertently block the hERG1 K(+) channel currents lead to drug induced Long QT Syndrome (LQTS). Accordingly, designing either hERG1 channel openers or current activators, with the potential to target other binding pockets of the channel, has been introduced as a viable approach in modern anti-arrhythmia drug development. However, reports and investigations on the molecular mechanisms underlying activators binding to the hERG1 channel remain sparse and the overall molecular design principles are largely unknown...
April 5, 2017: Journal of Molecular Graphics & Modelling
https://www.readbyqxmd.com/read/28495999/%C3%AE-arrestin-mediated-regulation-of-the-human-ether-a-go-go-related-gene-herg-potassium-channel
#10
Matthew G Sangoi, Shawn M Lamothe, Jun Guo, Tonghua Yang, Wentao Li, Ellen G Avery, John T Fisher, Shetuan Zhang
The rapidly activating delayed rectifier K(+) channel (IKr) is encoded by the human ether-a-go-go-related gene (hERG), which is important for the repolarization of the cardiac action potential. Mutations in hERG or drugs can impair the function or decrease the expression level of hERG channels, leading to long QT syndrome (LQTS). Thus, it is important to understand hERG channel trafficking and its regulation. For this purpose, G protein-coupled receptors (GPCRs), which regulate a vast array of cellular processes, represent a useful route...
May 11, 2017: Molecular Pharmacology
https://www.readbyqxmd.com/read/28492533/gene-patents-still-alive-and-kicking-their-impact-on-provision-of-genetic-testing-for-long-qt-syndrome-in-the-canadian-public-health-care-system
#11
Sarah E Ali-Khan, E Richard Gold
PurposeAlthough the Supreme Court of the United States limited their availability in Association for Molecular Pathology v. Myriad Genetics, gene patents remain important around the world. We examine the situation in Canada, where gene patents continue to exist, in light of recent litigation relating to familial long QT syndrome (LQTS).MethodsWe conducted in-depth semistructured interviews with 25 stakeholders across five Canadian provinces and supplemented this with a case analysis of the litigation.ResultsThe majority of LQTS testing was carried out outside Canada...
May 11, 2017: Genetics in Medicine: Official Journal of the American College of Medical Genetics
https://www.readbyqxmd.com/read/28490617/systemic-inflammation-as-a-novel-qt-prolonging-risk-factor-in-patients-with-torsades-de-pointes
#12
Pietro Enea Lazzerini, Franco Laghi-Pasini, Iacopo Bertolozzi, Gabriella Morozzi, Sauro Lorenzini, Antonella Simpatico, Enrico Selvi, Maria Romana Bacarelli, Francesco Finizola, Francesca Vanni, Deana Lazaro, Ademuyiwa Aromolaran, Nabil El Sherif, Mohamed Boutjdir, Pier Leopoldo Capecchi
OBJECTIVE: Increasing evidence indicates systemic inflammation as a new potential cause of acquired long QT syndrome (LQTS), via cytokine-mediated changes in cardiomyocyte ion channels. Torsade de pointes (TdP) is a life-threatening polymorphic ventricular tachycardia occurring in patients with LQTS, usually when multiple QT-prolonging factors are simultaneously present. Since classical risk factors cannot fully explain TdP events in a number of patients, we hypothesised that systemic inflammation may represent a currently overlooked risk factor contributing to TdP development in the general population...
May 10, 2017: Heart: Official Journal of the British Cardiac Society
https://www.readbyqxmd.com/read/28479515/phase-contrast-magnet-resonance-imaging-reveals-regional-transmural-and-base-to-apex-dispersion-of-mechanical-dysfunction-in-patients-with-long-qt-syndrome
#13
Johannes Brado, Markus J Dechant, Marius Menza, Adriana Komancsek, Corinna N Lang, Heiko Bugger, Daniela Foell, Bernd A Jung, Brigitte Stiller, Christoph Bode, Katja E Odening
BACKGROUND: Regional dispersion of prolonged repolarization is a hallmark of long QT syndrome (LQTS). We have also revealed regional heterogeneities in mechanical dysfunction in transgenic rabbit models of LQTS. OBJECTIVE: In this clinical pilot study, we investigated whether patients with LQTS exhibit dispersion of mechanical/diastolic dysfunction. METHODS: Nine pediatric patients with genotyped LQTS (12.2 ± 3.3 years) and 9 age- and sex-matched healthy controls (10...
May 4, 2017: Heart Rhythm: the Official Journal of the Heart Rhythm Society
https://www.readbyqxmd.com/read/28477086/effects-of-salvianolic-acid-b-on-l-type-calcium-channels-and-myocardial-contractility-in-isolated-rat-ventricular-myocytes-and-herg-k-channels-expressed-in-hek293-cells
#14
Qiongtao Song, Xue Han, Yuchong Xue, Tao Song, Xi Chu, Xuan Zhang, Yuanyuan Zhang, Ying Zhang, Jianping Zhang, Li Chu
Salvianolic acid B (Sal B), one of the chief water-soluble constituents in Radix Salviae Milthiorrhizae, has often been reported to possess considerable cardiovascular regulatory effects. However, the underlying biochemical and cellular mechanisms of its cardioprotection remain unclear. This study was designed to evaluate the role of Sal B regulation in L-type Ca(2+) channel currents (ICa,L) and cell contractility in rat cardiomyocytes and hERG K(+) channels expressed in HEK293 cells with the patch-clamp and Ca(2+) imaging techniques to clarify its underlying cardioprotective mechanisms...
May 5, 2017: Naunyn-Schmiedeberg's Archives of Pharmacology
https://www.readbyqxmd.com/read/28438721/clinical-profile-and-mutation-spectrum-of-long-qt-syndrome-in-saudi-arabia-the-impact-of-consanguinity
#15
Zuhair N Al-Hassnan, Majid Al-Fayyadh, Bander Al-Ghamdi, Azam Shafquat, Yaseen Mallawi, Faten Al-Hadeq, Sahar Tulbah, Zarghuna M A Shinwari, Abdulrahman Almesned, Ali Alakhfash, Fadel Al Fadly, Ahmed S Hersi, Abdullah Alhayani, Amal Al-Hashem, Dia Arafah, Nduna Dzimiri, Brian Meyer, Monther Rababh, Waleed Al-Manea
BACKGROUND: Congenital long QT syndrome (LQTS) is an inherited, potentially fatal arrhythmogenic disorder. At least 16 genes have been implicated in LQTS; the yield of genetic analysis of 3 genes (KCNQ1, KCNH2, and SCN5A) is about 70%, with KCNQ1 mutations accounting for ∼50% of positive cases. LQTS is mostly inherited in an autosomal dominant pattern. Systemic analysis of LQTS has not been previously conducted in a population with a high degree of consanguinity. OBJECTIVES: To describe the clinical and molecular profiles of LQTS in the highly consanguineous Saudi population...
April 22, 2017: Heart Rhythm: the Official Journal of the Heart Rhythm Society
https://www.readbyqxmd.com/read/28429460/automated-t-wave-analysis-can-differentiate-acquired-qt-prolongation-from-congenital-long-qt-syndrome
#16
Alan Sugrue, Peter A Noseworthy, Vaclav Kremen, J Martijn Bos, Bo Qiang, Ram K Rohatgi, Yehu Sapir, Zachi I Attia, Peter Brady, Pedro J Caraballo, Samuel J Asirvatham, Paul A Friedman, Michael J Ackerman
BACKGROUND: Prolongation of the QT on the surface electrocardiogram can be due to either genetic or acquired causes. Distinguishing congenital long QT syndrome (LQTS) from acquired QT prolongation has important prognostic and management implications. We aimed to investigate if quantitative T-wave analysis could provide a tool for the physician to differentiate between congenital and acquired QT prolongation. METHODS: Patients were identified through an institution-wide computer-based QT screening system which alerts the physician if the QTc ≥ 500 ms...
April 21, 2017: Annals of Noninvasive Electrocardiology
https://www.readbyqxmd.com/read/28416468/cardiac-transplantation-in-children-and-adolescents-with-long-qt-syndrome
#17
Angela M Kelle, J Martijn Bos, Susan P Etheridge, Bryan C Cannon, Randall M Bryant, Jonathan N Johnson, Michael J Ackerman
BACKGROUND: Long QT syndrome (LQTS) is a potentially lethal, yet highly treatable, cardiac channelopathy. Cardiac transplantation has been reported anecdotally for patients with severe LQTS refractory to standard therapies. OBJECTIVE: The purpose of this study was to evaluate the incidence of and risk factors for cardiac transplantation in children evaluated and treated in an LQTS specialty center. METHODS: This was a retrospective review of 349 children with LQTS (mean age at diagnosis, 8...
April 14, 2017: Heart Rhythm: the Official Journal of the Heart Rhythm Society
https://www.readbyqxmd.com/read/28413954/computational-models-for-understanding-of-structure-function-and-pharmacology-of-the-cardiac-potassium-channel-kv11-1-herg
#18
Sören Wacker, Sergei Yu Noskov, Laura L Perissinotti
The rapid delayed rectifier current IKr is one of the major K+ currents involved into repolarization of the human cardiac action potential. Various inherited or drug-induced forms of the long QT syndrome (LQTS) in humans are linked to functional and structural modifications in the IKr conducting channels. IKr is carried by the potassium channel Kv11.1 encoded by the gene KCNH2 (commonly referred to as human ether-a-go-go-related gene or hERG) [1][2]. The first necessary step for predicting emergent drug effects on the heart is determining and modeling the binding thermodynamics and kinetics of primary and major off-target drug interactions with subcellular targets...
April 14, 2017: Current Topics in Medicinal Chemistry
https://www.readbyqxmd.com/read/28412158/lidocaine-attenuation-testing-an-in%C3%A2-vivo-investigation-of-putative-lqt3-associated-variants-in-the-scn5a-encoded-sodium-channel
#19
Heather N Anderson, J Martijn Bos, Jamie D Kapplinger, Jana M Meskill, Dan Ye, Michael J Ackerman
BACKGROUND: Long QT syndrome type 3 (LQT3) accounts for 5%-10% of long QT syndrome and results from gain-of-function mutations in the SCN5A-encoded sodium channel. Approximately 2% of healthy individuals host rare SCN5A variants of uncertain significance (VUS). Distinction of true LQT3-causative mutations from background genetic noise is essential. OBJECTIVE: The purpose of this study was to assess the use of the lidocaine attenuation test (LAT) in evaluating patients with possible LQT3...
April 13, 2017: Heart Rhythm: the Official Journal of the Heart Rhythm Society
https://www.readbyqxmd.com/read/28405995/recurrent-ventricular-tachycardia-due-to-long-qt-syndrome
#20
Rambabu Singh, Kshitiz Nath, Archana
Long QT syndrome (LQTS) is a rare inherited heart condition in which delayed repolarization of the heart following a heartbeat, increases the risk of episodes of Torsades de pointes (TdP, a form of irregular heartbeat that originates from the ventricles). These episodes may lead to palpitations, fainting, and sudden death due to ventricular fibrillation. Episodes may be provoked by various stimuli, depending on the subtype of the condition. We are reporting a case of 37 years old male whom we diagnosed to have long QT syndrome on the basis of clinical and ECG findings...
December 2016: Journal of the Association of Physicians of India
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