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https://www.readbyqxmd.com/read/29127493/late-sodium-current-associated-cardiac-electrophysiological-and-mechanical-dysfunction
#1
REVIEW
Shandong Yu, Gang Li, Christopher L-H Huang, Ming Lei, Lin Wu
Late sodium current (INaL) is a small sustained inward current observed during the cardiac action potential plateau phase following decay of the early peak INa. The endogenous INaL is relatively small in normal hearts but exerts functionally significant effects on cardiomyocyte repolarization with potentially pro-arrhythmic effects in hearts with reduced repolarization reserve. Enhanced INa,L occurs in long QT syndrome 3 (LQTS 3) patients, and under a number of pathological and pharmacological cardiovascular conditions, including bradycardia, myocardial ischemia, reperfusion injury, and heart failure...
November 10, 2017: Pflügers Archiv: European Journal of Physiology
https://www.readbyqxmd.com/read/29121487/risk-of-cardiac-events-in-long-qt-syndrome-patients-when-taking-antiseizure-medications
#2
David S Auerbach, Yitschak Biton, Bronislava Polonsky, Scott McNitt, Robert A Gross, Robert T Dirksen, Arthur J Moss
Many antiseizure medications (ASMs) affect ion channel function. We investigated whether ASMs alter the risk of cardiac events in patients with corrected QT (QTc) prolongation. The study included people from the Rochester-based Long QT syndrome (LQTS) Registry with baseline QTc prolongation and history of ASM therapy (n = 296). Using multivariate Anderson-Gill models, we assessed the risk of recurrent cardiac events associated with ASM therapy. We stratified by LQTS genotype and predominant mechanism of ASM action (Na(+) channel blocker and gamma-aminobutyric acid modifier...
October 20, 2017: Translational Research: the Journal of Laboratory and Clinical Medicine
https://www.readbyqxmd.com/read/29104543/simultaneous-quantification-of-spatially-discordant-alternans-in-voltage-and-intracellular-calcium-in-langendorff-perfused-rabbit-hearts-and-inconsistencies-with-models-of-cardiac-action-potentials-and-ca-transients
#3
Ilija Uzelac, Yanyan C Ji, Daniel Hornung, Johannes Schröder-Scheteling, Stefan Luther, Richard A Gray, Elizabeth M Cherry, Flavio H Fenton
Rationale: Discordant alternans, a phenomenon in which the action potential duration (APDs) and/or intracellular calcium transient durations (CaDs) in different spatial regions of cardiac tissue are out of phase, present a dynamical instability for complex spatial dispersion that can be associated with long-QT syndrome (LQTS) and the initiation of reentrant arrhythmias. Because the use of numerical simulations to investigate arrhythmic effects, such as acquired LQTS by drugs is beginning to be studied by the FDA, it is crucial to validate mathematical models that may be used during this process...
2017: Frontiers in Physiology
https://www.readbyqxmd.com/read/29101013/the-congenital-long-qt-syndrome-type-3-an-update
#4
REVIEW
Andrés Ricardo Pérez-Riera, Raimundo Barbosa-Barros, Rodrigo Daminello Raimundo, Marianne Penachini da Costa de Rezende Barbosa, Isabel Cristina Esposito Sorpreso, Luiz Carlos de Abreu
Congenital long QT syndrome type 3 (LQT3) is the third in frequency compared to the 15 forms known currently of congenital long QT syndrome (LQTS). Cardiac events are less frequent in LQT3 when compared with LQT1 and LQT2, but more likely to be lethal; the likelihood of dying during a cardiac event is 20% in families with an LQT3 mutation and 4% with either an LQT1 or an LQT2 mutation. LQT3 is consequence of mutation of gene SCN5A which codes for the Nav1.5 Na(+) channel α-subunit and electrocardiographically characterized by a tendency to bradycardia related to age, prolonged QT/QTc interval (mean QTc value 478 ± 52 ms), accentuated QT dispersion consequence of prolonged ST segment, late onset of T wave and frequent prominent U wave because of longer repolarization of the M cell across left ventricular wall...
October 31, 2017: Indian Pacing and Electrophysiology Journal
https://www.readbyqxmd.com/read/29083088/clinical-applications-of-qt-rr-hysteresis-assessment-a%C3%A2-systematic-review
#5
REVIEW
Hugo Gravel, Vincent Jacquemet, Nagib Dahdah, Daniel Curnier
BACKGROUND: QT/RR hysteresis (QT-hys) is an index of the time accommodation of ventricular repolarization to heart rate changes. This report comprehensively reviews studies addressing QT-hys as a biomarker of medical conditions. METHODS: This is a secondary analysis of data from a recent systematic review pertaining to methods of assessment of QT-hys. Articles included in the former review were filtered in order to select original articles investigating the association of QT-hys with medical conditions in humans...
October 30, 2017: Annals of Noninvasive Electrocardiology
https://www.readbyqxmd.com/read/29071820/application-of-multigene-panel-sequencing-in-patients-with-prolonged-rate-corrected-qt-interval-and-no-pathogenic-variants-detected-in-kcnq1-kcnh2-and-scn5a
#6
Soo Hyun Seo, So Yeon Kim, Sung Im Cho, Hyunwoong Park, Seungjun Lee, Jong Moon Choi, Man Jin Kim, Jee Soo Lee, Kyung Jin Ahn, Mi Kyoung Song, Eun Jung Bae, Sung Sup Park, Moon Woo Seong
Long QT syndrome (LQTS) is an inherited cardiac disease characterized by a prolonged heart rate-corrected QT (QTc) interval. We investigated the genetic causes in patients with prolonged QTc intervals who were negative for pathogenic variants in three major LQTS-related genes (KCNQ1, KCNH2, and SCN5A). Molecular genetic testing was performed using a panel including 13 LQTS-related genes and 67 additional genes implicated in other cardiac diseases. Overall, putative genetic causes of prolonged QTc interval were identified in three of the 30 patients (10%)...
January 2018: Annals of Laboratory Medicine
https://www.readbyqxmd.com/read/29059199/effectiveness-of-beta-blockers-depending-on-the-genotype-of-congenital-long-qt-syndrome-a-meta-analysis
#7
Jinhee Ahn, Hyun Jung Kim, Jong-Il Choi, Kwang No Lee, Jaemin Shim, Hyeong Sik Ahn, Young-Hoon Kim
BACKGROUND: Beta-blockers are first-line therapy in patients with congenital long-QT syndrome (LQTS). OBJECTIVE: This study sought to determine the differences in effectiveness of beta-blockers on risk reduction according to LQTS genotype. METHODS: We searched MEDLINE, EMBASE, and CENTRAL databases to investigate the use of beta-blockers (atenolol, nadolol, propranolol, and metoprolol) in patients with LQTS. Hazard ratio (HR) and relative risk (RR) were extracted or calculated from studies reporting cardiac events (syncope, aborted cardiac arrest (ACA), or sudden cardiac death (SCD))...
2017: PloS One
https://www.readbyqxmd.com/read/29057193/long-qt-syndrome-unveiled-by-a-fatal-combination-of-medications-and-electrolyte-abnormalities
#8
Pooja Sethi, Jennifer Treece, Vandana Pai, Chidinma Onweni
Long QT syndrome (LQTS) can present with syncope and seizure-like activity in the setting of torsades de pointes (TdP) with hemodynamic instability. Electrolyte abnormalities and medications can predispose to TdP in the setting of latent LQTS. An implantable cardioverter defibrillator (ICD) is needed if patients with TdP continue to be symptomatic despite medical treatment. We report a case of a patient who presented with seizures and was found to have prolonged corrected QT interval (QTc). During her admission, she was treated with ondansetron...
August 18, 2017: Curēus
https://www.readbyqxmd.com/read/29036559/the-brisk-standing-test-for-long-qt-syndrome-in-prepubertal-school-children-defining-normal
#9
L H P M Filippini, P G Postema, K Zoubin, B J M Hermans, N A Blom, T Delhaas, A A M Wilde
Aims: Long QT syndrome (LQTS) is associated with malignant arrhythmias and sudden death from birth to advanced age. Prolongation of the QT-interval, may however be concealed on standard electrocardiograms (ECG). The brisk-standing-test (BST) was developed to guide LQTS-diagnosis and treatment in adults. We hypothesized that the BST may be used in prepubertal children to identify LQTS subjects. Accordingly, reference values for the BST should be available to prevent incorrect diagnosis and treatment of LQTS...
October 3, 2017: Europace: European Pacing, Arrhythmias, and Cardiac Electrophysiology
https://www.readbyqxmd.com/read/29033053/identification-and-characterization-of-a-novel-recessive-kcnq1-mutation-associated-with-romano-ward-long-qt-syndrome-in-two-iranian-families
#10
Zahra Zafari, Mohammad Dalili, Sirus Zeinali, Siamak Saber, Amir Farjam Fazeli Far, Mohammad Taghi Akbari
BACKGROUND: One of the foremost causes of sudden cardiac death in the young is an inherent cardiac arrhythmia known as Long-QT syndrome (LQTS). Whereas heterozygous mutations typically lead to the Romano-Ward type of LQTS, We have provided a further evidence for the recessive transmission of a novel KCNQ1 gene mutation in two consanguineous families for the first time in Iran. METHODS: Next generation sequencing, DNA Sanger sequencing and haplotype analysis were performed for genotype determination...
July 12, 2017: Journal of Electrocardiology
https://www.readbyqxmd.com/read/29016765/broad-antiarrhythmic-effect-of-mexiletine-in-different-arrhythmia-models
#11
Gerrit Frommeyer, Jonas Garthmann, Christian Ellermann, Dirk G Dechering, Simon Kochhäuser, Florian Reinke, Julia Köbe, Kristina Wasmer, Lars Eckardt
Aims: Experimental studies and clinical reports suggest antiarrhythmic properties of mexiletine in different arrhythmias. We aimed at investigating mexiletine in experimental models of atrial fibrillation (AF) as well as in long-QT- (LQTS) and short-QT-syndrome (SQTS). Methods and results: In 15 isolated rabbit hearts, erythromycin (300 µM) was infused for simulation of long-QT-2-syndrome. In further 13 hearts, veratridine was administered to simulate long-QT-3-syndrome...
August 1, 2017: Europace: European Pacing, Arrhythmias, and Cardiac Electrophysiology
https://www.readbyqxmd.com/read/28992755/drug-mediated-shortening-of-action-potentials-in-lqts2-human-induced-pluripotent-stem-cell-cardiomyocytes
#12
Gary Duncan, Karl Firth, Vinoj George, Minh Duc Hoang, Andrew Staniforth, Godfrey Smith, Chris Denning
Cardiomyocytes (CMs) derived from human induced pluripotent stem cells (hiPSCs) are now a well-established modality for modeling genetic disorders of the heart. This is especially so for long QT syndrome (LQTS), which is caused by perturbation of ion channel function, and can lead to fainting, malignant arrhythmias and sudden cardiac death. LQTS2 is caused by mutations in KCNH2, a gene whose protein product contributes to IKr (also known as HERG), which is the predominant repolarizing potassium current in CMs...
October 9, 2017: Stem Cells and Development
https://www.readbyqxmd.com/read/28988457/re-evaluating-pathogenicity-of-variants-associated-with-the-long-qt-syndrome
#13
Jonathan R Kaltman, Frank Evans, Yi-Ping Fu
INTRODUCTION: Genetic testing for congenital long-QT syndrome (LQTS) has become common. Recent studies have shown that some variants labelled as pathogenic might be misclassified due to sparse case reports and relatively common allele frequencies in the general population. This study aims to evaluate the presence of LQTS-associated variants in the Genome Aggregation Database (gnomAD) population, and assess the functional impact of these variants. METHODS AND RESULTS: Variants associated with LQTS from the Human Gene Mutation Database were extracted and matched to the gnomAD to evaluate population-based allele frequencies (AF)...
October 8, 2017: Journal of Cardiovascular Electrophysiology
https://www.readbyqxmd.com/read/28964110/a-model-of-cardiac-ryanodine-receptor-gating-predicts-experimental-ca-2-dynamics-and-ca-2-triggered-arrhythmia-in-the-long-qt-syndrome
#14
Dan Wilson, Bard Ermentrout, Jan Němec, Guy Salama
Abnormal Ca(2+) handling is well-established as the trigger of cardiac arrhythmia in catecholaminergic polymorphic ventricular tachycardia and digoxin toxicity, but its role remains controversial in Torsade de Pointes (TdP), the arrhythmia associated with the long QT syndrome (LQTS). Recent experimental results show that early afterdepolarizations (EADs) that initiate TdP are caused by spontaneous (non-voltage-triggered) Ca(2+) release from Ca(2+)-overloaded sarcoplasmic reticulum (SR) rather than the activation of the L-type Ca(2+)-channel window current...
September 2017: Chaos
https://www.readbyqxmd.com/read/28963955/structural-investigation-of-vesnarinone-at-the-pore-domains-of-open-and-open-inactivated-states-of-herg1-k-channel
#15
Gülru Kayık, Nurcan Ş Tüzün, Serdar Durdagi
In this study, the dynamics of vesnarinone bounded hERG1 K(+) channels are investigated using in silico approaches such as molecular docking, molecular dynamics (MD) simulations, MM/PBSA (Molecular Mechanics/Poisson Boltzmann Surface Area) calculations and Principal Component Analysis (PCA). Vesnarinone (a cardiotonic agent) falls into a category of drugs that inhibit phosphodiesterase 3-type (PDE3) enzymes. PDE3 enzymes have specific roles in the dehydyrolysis of intracellular second messengers 3',5'-cyclic adenosine monophosphate (cAMP) and 3',5'-cyclic guanosine monophosphate (cGMP)...
September 6, 2017: Journal of Molecular Graphics & Modelling
https://www.readbyqxmd.com/read/28942950/jt-interval-what-does-this-interval-mean
#16
Wojciech Zareba, Scott McNitt, Slava Polonsky, Jean-Philippe Couderc
The JTp interval gained interest as a marker differentiating effects of drugs on cardiac ion channels. For JTp interval, both the beginning - identification of J point and identification of T wave end remains the subject of substantial variability. We aimed to analyze diagnostic and prognostic performance of JTp interval in the International LQTS Registry data. ECGs from 804 gene carriers and 1139 non-carriers from LQT1 families, 735 carriers and 1145 non-carriers from LQT2 families, and 238 carriers and 554 non-carriers from LQT3 families were evaluated...
August 3, 2017: Journal of Electrocardiology
https://www.readbyqxmd.com/read/28917558/cardiac-sympathectomy-for-the-management-of-ventricular-arrhythmias-refractory-to-catheter-ablation
#17
Travis Richardson, Ricardo Lugo, Pablo Saavedra, George Crossley, Walter Clair, Sharon Shen, Juan Carlos Estrada, Jay Montgomery, M Benjamin Shoemaker, Christopher Ellis, Gregory F Michaud, Eric Lambright, Arvindh N Kanagasundram
BACKGROUND: Catheter ablation is now a mainstay of therapy for ventricular arrhythmias (VAs). However, there are scenarios where either physiological or anatomical factors make ablation less likely to be successful. OBJECTIVE: The purpose of this study was to demonstrate that cardiac sympathetic denervation (CSD) may be an alternate therapy for patients with difficult-to-ablate VAs. METHODS: We identified all patients referred for CSD at a single center for indications other than long QT syndrome and catecholaminergic polymorphic ventricular tachycardia who had failed catheter ablation...
September 14, 2017: Heart Rhythm: the Official Journal of the Heart Rhythm Society
https://www.readbyqxmd.com/read/28894151/the-effects-of-ageing-and-adrenergic-challenge-on-electrocardiographic-phenotypes-in-a-murine-model-of-long-qt-syndrome-type-3
#18
Karan R Chadda, Shiraz Ahmad, Haseeb Valli, Ingrid den Uijl, Ali Bak Al-Hadithi, Samantha C Salvage, Andrew A Grace, Christopher L-H Huang, Kamalan Jeevaratnam
Long QT Syndrome 3 (LQTS3) arises from gain-of-function Nav1.5 mutations, prolonging action potential repolarisation and electrocardiographic (ECG) QT interval, associated with increased age-dependent risk for major arrhythmic events, and paradoxical responses to β-adrenergic agents. We investigated for independent and interacting effects of age and Scn5a+/ΔKPQ genotype in anaesthetised mice modelling LQTS3 on ECG phenotypes before and following β-agonist challenge, and upon fibrotic change. Prolonged ventricular recovery was independently associated with Scn5a+/ΔKPQ and age...
September 11, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28869094/effect-of-age-and-gender-on-the-qtc-interval-in-healthy-individuals-and-patients-with-long-qt-syndrome
#19
REVIEW
Arja Suzanne Vink, Sally-Ann B Clur, Arthur A M Wilde, Nico A Blom
Age- and gender-related differences in QTc-interval are most likely the result of changes in sex-specific hormones. Although the exact mechanisms and pathophysiology of sex hormones on the QTc-interval are not known, testosterone appears to shorten the QTc-interval. In females, however, there is a more complex interaction between progesterone and estrogen. In patients with an impaired repolarization, such as long-QT syndrome (LQTS), the effect of these sex hormones on the QTc-interval is more pronounced with a differing sensitivity between the LQTS genotypes...
August 3, 2017: Trends in Cardiovascular Medicine
https://www.readbyqxmd.com/read/28864717/impact-of-presynaptic-sympathetic-imbalance-in-long-qt-syndrome-by-positron-emission-tomography
#20
Sven Zumhagen, Alexis Vrachimis, Lars Stegger, Peter Kies, Christian Wenning, Marko Ernsting, Jovanca Müller, Guiscard Seebohm, Matthias Paul, Klaus Schäfers, Birgit Stallmeyer, Michael Schäfers, Eric Schulze-Bahr
OBJECTIVE: We investigated the impact of cardiac presynaptic norepinephrine recycling in patients with long-QT syndrome (LQTS) using positron emission tomography (PET) with (11)C-meta-hydroxyephedrine ([(11)C]mHED-PET). METHODS: [(11)C]mHED-PET was performed in 25 patients with LQTS (LQT1: n=14; LQT2: n=11) and 20 healthy controls and correlated with clinical parameters. [(11)C]mHED-PET images were analysed for global and regional retention indices (RI) and washout rates (WO) reflecting dynamic parameters of the tracer activity...
September 1, 2017: Heart: Official Journal of the British Cardiac Society
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