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https://www.readbyqxmd.com/read/28815597/cardiac-action-potential-repolarization-re-visited-early-repolarization-shows-all-or-none-behaviour
#1
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/28797161/masked-inherited-primary-arrhythmia-syndromes-in-sudden-cardiac-death-patients-accompanied-by-coronary-vasospasm
#2
Ki Hong Lee, Hyung Wook Park, Jeong Nam Eun, Jeong Gwan Cho, Nam Sik Yoon, Mi Ran Kim, Yo Han Ku, Hyukjin Park, Seung Hun Lee, Jeong Han Kim, Min Chul Kim, Woo Jin Kim, Hyun Kuk Kim, Jae Yeong Cho, Keun-Ho Park, Doo Sun Sim, Hyun Ju Yoon, Kye Hun Kim, Young Joon Hong, Ju Han Kim, Youngkeun Ahn, Myung Ho Jeong, Jong Chun Park
Background/Aims: Coronary vasospasms are one of the important causes of sudden cardiac death (SCD). Provocation of coronary vasospasms can be useful, though some results may lead to false positives, with patients potentially experiencing recurrent SCD despite appropriate medical treatments. We hypothesized that it is not coronary vasospasms but inherited primary arrhythmia syndromes (IPAS) that underlie the development of SCD. Methods: We analyzed 74 consecutive patients (3...
August 11, 2017: Korean Journal of Internal Medicine
https://www.readbyqxmd.com/read/28756335/computational-approaches-to-understand-the-adverse-drug-effect-on-potassium-sodium-and-calcium-channels-for-predicting-tdp-cardiac-arrhythmias
#3
Mohsen Sharifi
Ion channels play a crucial role in the cardiovascular system. Our understanding of cardiac ion channel function has improved since their first discoveries. The flow of potassium, sodium and calcium ions across cardiomyocytes is vital for regular cardiac rhythm. Blockage of these channels, delays cardiac repolarization or tend to shorten repolarization and may induce arrhythmia. Detection of drug risk by channel blockade is considered essential for drug regulators. Advanced computational models can be used as an early screen for torsadogenic potential in drug candidates...
July 8, 2017: Journal of Molecular Graphics & Modelling
https://www.readbyqxmd.com/read/28746852/photo-cross-linking-of-iks-demonstrates-state-dependent-interactions-between-kcne1-and-kcnq1
#4
Maartje Westhoff, Christopher I Murray, Jodene Eldstrom, David Fedida
The slow delayed rectifier potassium current (IKs) is a key repolarizing current during the cardiac action potential. It consists of four KCNQ1 α-subunits and up to four KCNE1 β-subunits, which are thought to reside within external clefts of the channel. The interaction of KCNE1 with KCNQ1 dramatically delays opening of the channel but the mechanisms by which this occur are not yet fully understood. Here, we have used unnatural amino acid photo-cross-linking to investigate the dynamic interactions that occur between KCNQ1 and KCNE1 during activation gating...
July 25, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28705875/electrical-and-structural-substrate-of-arrhythmogenic-right-ventricular-cardiomyopathy-determined-using-noninvasive-electrocardiographic-imaging-and-late-gadolinium-magnetic-resonance-imaging
#5
Christopher M Andrews, Neil T Srinivasan, Stefania Rosmini, Heerajnarain Bulluck, Michele Orini, Sharon Jenkins, Antonis Pantazis, William J McKenna, James C Moon, Pier D Lambiase, Yoram Rudy
BACKGROUND: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a significant cause of sudden cardiac death in the young. Improved noninvasive assessment of ARVC and better understanding of the disease substrate are important for improving patient outcomes. METHODS AND RESULTS: We studied 20 genotyped ARVC patients with a broad spectrum of disease using electrocardiographic imaging (a method for noninvasive cardiac electrophysiology mapping) and advanced late gadolinium enhancement cardiac magnetic resonance scar imaging...
July 2017: Circulation. Arrhythmia and Electrophysiology
https://www.readbyqxmd.com/read/28689986/quaternion-based-study-of-angular-velocity-of-the-cardiac-vector-during-myocardial-ischaemia
#6
Pablo Daniel Cruces, Pedro David Arini
BACKGROUND: Early detection of acute ischaemia through non-invasive methods remains a challenge in health research. Ischaemic condition caused by a decrease in the blood supply in a cardiac region induces hypoxia and metabolic abnormalities that contribute to the electrical instability of the heart and to the development of slow conduction in damaged tissue. METHODS: Herein, a percutaneous transluminal coronary angiography (PTCA) is considered as a model of supply ischaemia...
June 30, 2017: International Journal of Cardiology
https://www.readbyqxmd.com/read/28687671/tachycardia-induced-j-wave-changes-in-patients-with-and-without-idiopathic-ventricular-fibrillation
#7
Yoshiyasu Aizawa, Seiji Takatsuki, Takahiko Nishiyama, Takehiro Kimura, Shun Kohsaka, Yoshiaki Kaneko, Yasuya Inden, Naohiko Takahashi, Satoshi Nagase, Yoshifusa Aizawa, Keichi Fukuda
BACKGROUND: To know the underlying mechanisms of J waves, the response to atrial pacing was studied in patients with idiopathic ventricular fibrillation (IVF) and patients with non-IVF. METHODS AND RESULTS: In 8 patients with IVF, the J-wave amplitude was measured before, during, and after atrial pacing. All patients had episodes of ventricular fibrillation without structural heart disease. The responses of J waves were compared with those of the 17 non-IVF control subjects who revealed J waves but no history of cardiac arrest and underwent electrophysiological study...
July 2017: Circulation. Arrhythmia and Electrophysiology
https://www.readbyqxmd.com/read/28685701/the-role-of-quinidine-in-the-pharmacological-therapy-of-ventricular-arrhythmias-quinidine
#8
Bojana Bozic, Teodora Vidonja Uzelac, Aleksandra Kezic, Milica Bajcetic
BACKGROUND: Historically, quinidine was the first medicine used in the therapy of heart arrhythmias. Studies in the early 20th century identified quinidine, a diastereomer of the antimalarial quinine, as the most potent of the antiarrhythmic substances extracted from the cinchona plant. Quinidine is used by the 1920s, as an antiarrhythmic agent to maintain sinus rhythm after conversion from atrial flutter or atrial fibrillation and to prevent recurrence of ventricular tachycardia or ventricular fibrillation...
July 7, 2017: Mini Reviews in Medicinal Chemistry
https://www.readbyqxmd.com/read/28685698/medical-therapy-for-long-qt-syndrome
#9
George Adamos, Nicoletta Iacovidou, Theodoros Xanthos
Long QT syndrome (LQTS) is an arrhythmogenic disorder characterized by repolarization abnormalities with a propensity to cause life threatening cardiac events. The first manifestation of the syndrome may be sudden death, therefore, early diagnosis and therapy is of great importance. LQTS can be both congenital and acquired. The latter is most commonly seen in hospitalized patients and such individuals have an easily recognizable and reversible precipitating factor (electrolyte disturbances, certain drugs etc...
July 7, 2017: Mini Reviews in Medicinal Chemistry
https://www.readbyqxmd.com/read/28668303/ca-2-activated-cl-current-is-antiarrhythmic-by-reducing-both-spatial-and-temporal-heterogeneity-of-cardiac-repolarization
#10
Bence Hegyi, Balázs Horváth, Krisztina Váczi, Mónika Gönczi, Kornél Kistamás, Ferenc Ruzsnavszky, Roland Veress, Leighton T Izu, Ye Chen-Izu, Tamás Bányász, János Magyar, László Csernoch, Péter P Nánási, Norbert Szentandrássy
The role of Ca(2+)-activated Cl(-) current (ICl(Ca)) in cardiac arrhythmias is still controversial. It can generate delayed afterdepolarizations in Ca(2+)-overloaded cells while in other studies incidence of early afterdepolarization (EAD) was reduced by ICl(Ca). Therefore our goal was to examine the role of ICl(Ca) in spatial and temporal heterogeneity of cardiac repolarization and EAD formation. Experiments were performed on isolated canine cardiomyocytes originating from various regions of the left ventricle; subepicardial, midmyocardial and subendocardial cells, as well as apical and basal cells of the midmyocardium...
August 2017: Journal of Molecular and Cellular Cardiology
https://www.readbyqxmd.com/read/28659867/increased-short-term-beat-to-beat-qt-interval-variability-in-patients-with-impaired-glucose-tolerance
#11
Andrea Orosz, István Baczkó, Szabolcs Nyiraty, Anna E Körei, Zsuzsanna Putz, Róbert Takács, Attila Nemes, Tamás T Várkonyi, László Balogh, György Ábrahám, Péter Kempler, Julius Gy Papp, András Varró, Csaba Lengyel
Prediabetic states and diabetes are important risk factors for cardiovascular morbidity and mortality. Determination of short-term QT interval variability (STVQT) is a non-invasive method for assessment of proarrhythmic risk. The aim of the study was to evaluate the STVQT in patients with impaired glucose tolerance (IGT). 18 IGT patients [age: 63 ± 11 years, body mass index (BMI): 31 ± 6 kg/m(2), fasting glucose: 6.0 ± 0.4 mmol/l, 120 min postload glucose: 9.0 ± 1.0 mmol/l, hemoglobin A1c (HbA1c): 5...
2017: Frontiers in Endocrinology
https://www.readbyqxmd.com/read/28651660/sudden-improvement-in-ventricular-repolarization-abnormality-after-a-short-detraining-period-in-an-athlete
#12
Noriko Motoki, Yohei Akazawa, Akira Hachiya, Yuji Inaba
We describe the case of a 17-year-old male soccer player with T-wave inversion in precordial leads in resting electrocardiography, which also disclosed sinus bradycardia, early repolarization, and increased QRS voltage. These findings strongly suggested cardiomyopathy. The patient's T-wave inversion disappeared during only 2 weeks of detraining, and it re-appeared 2 weeks after resumption of intensive training. This sudden change in electrocardiographic parameters over a short period helped in identifying the adolescent as having athlete's heart...
June 27, 2017: Cardiology in the Young
https://www.readbyqxmd.com/read/28648627/myofilament-protein-dynamics-modulate-ead-formation-in-human-hypertrophic-cardiomyopathy
#13
REVIEW
Melanie A Zile, Natalia A Trayanova
Patients with hypertrophic cardiomyopathy (HCM), a disease associated with sarcomeric protein mutations, often suffer from sudden cardiac death (SCD) resulting from arrhythmia. In order to advance SCD prevention strategies, our understanding of how sarcomeric mutations in HCM patients contribute to enhanced arrhythmogenesis needs to be improved. Early afterdepolarizations (EADs) are an important mechanism underlying arrhythmias associated with HCM-SCD. Although the ionic mechanisms underlying EADs have been studied in general, whether myofilament protein dynamics mechanisms also underlie EADs remains unknown...
June 22, 2017: Progress in Biophysics and Molecular Biology
https://www.readbyqxmd.com/read/28624975/deleterious-acute-and-chronic-effects-of-bradycardic-right-ventricular-apex-pacing-consequences-for-arrhythmic-outcome
#14
T R G Stams, A Dunnink, W M van Everdingen, H D M Beekman, R van der Nagel, B Kok, M F A Bierhuizen, M J Cramer, M Meine, M A Vos
In the chronic complete atrioventricular (AV) block dog (CAVB) model, both bradycardia and altered ventricular activation due to the uncontrolled idioventricular rhythm contribute to ventricular remodeling and the enhanced susceptibility to Torsade de Pointes (TdP) arrhythmias. We investigated the effect of permanent bradycardic right ventricular apex (RVA) pacing on mechanical and electrical remodeling and TdP. In 23 anesthetized dogs, serial experiments were performed at sinus rhythm (SR), acutely after AV block (AAVB) and 3 weeks of remodeling CAVB at a fixed pacing rate of 60/min...
July 2017: Basic Research in Cardiology
https://www.readbyqxmd.com/read/28619993/low-extracellular-potassium-prolongs-repolarization-and-evokes-early-afterdepolarization-in-human-induced-pluripotent-stem-cell-derived-cardiomyocytes
#15
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/28612303/additive-proarrhythmic-effect-of-combined-treatment-with-qt-prolonging-agents
#16
Gerrit Frommeyer, Christina Fischer, Christian Ellermann, Dirk G Dechering, Simon Kochhäuser, Philipp S Lange, Kristina Wasmer, Michael Fehr, Lars Eckardt
Drug combinations may elevate the risk of proarrhythmia. The aim of the present study was to investigate whether combinations of non-cardiovascular agents induce an additive increase in the proarrhythmic risk. In 12 female rabbit hearts, a drug combination of cotrimoxazole (300 µM), ondansetron (5 µM) and domperidone (1 µM) was infused after obtaining baseline data. In another 13 hearts, a combination of cotrimoxazole (300 µM), ondansetron (5 µM) and erythromycin (300 µM) was infused. Monophasic action potentials and ECG displayed a significant QT prolongation in all groups...
June 13, 2017: Cardiovascular Toxicology
https://www.readbyqxmd.com/read/28611679/icariin-a-novel-blocker-of-sodium-and-calcium-channels-eliminates-early-and-delayed-afterdepolarizations-as-well-as-triggered-activity-in-rabbit-cardiomyocytes
#17
Wanzhen Jiang, Mengliu Zeng, Zhenzhen Cao, Zhipei Liu, Jie Hao, Peipei Zhang, Youjia Tian, Peihua Zhang, Jihua Ma
Icariin, a flavonoid monomer from Herba Epimedii, has confirmed pharmacological and biological effects. However, its effects on arrhythmias and cardiac electrophysiology remain unclear. Here we investigate the effects of icariin on ion currents and action potentials (APs) in the rabbit myocardium. Furthermore, the effects of icariin on aconitine-induced arrhythmias were assessed in whole rabbits. Ion currents and APs were recorded in voltage-clamp and current-clamp mode in rabbit left ventricular myocytes (LVMs) and left atrial myocytes (LAMs), respectively...
2017: Frontiers in Physiology
https://www.readbyqxmd.com/read/28606656/divergent-antiarrhythmic-effects-of-resveratrol-and-piceatannol-in-a-whole-heart-model-of-long-qt-syndrome
#18
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...
September 15, 2017: International Journal of Cardiology
https://www.readbyqxmd.com/read/28591770/inferolateral-early-repolarization-among-non-ischaemic-sudden-cardiac-death-victims
#19
Lauri T A Holmström, Mira A Haukilahti, Jani T Tikkanen, Aapo L Aro, Tuomas V Kenttä, Marja-Leena Kortelainen, Heikki V Huikuri, Matti J Junttila
Aim: Inferolateral early repolarization (ER) has been associated with an increased risk of sudden cardiac death (SCD). However, this association is thought to be mainly due to ischaemic SCD. The association of ER and non-ischaemic SCD has not been studied. The aim was to evaluate whether inferolateral ER is associated with non-ischaemic SCD. Methods and results: Study population consists of 275 consecutive victims of non-ischaemic SCD with 12-lead ECG and control group of general population cohort with 10 864 subjects...
June 7, 2017: Europace: European Pacing, Arrhythmias, and Cardiac Electrophysiology
https://www.readbyqxmd.com/read/28569435/the-new-kids-on-the-block-of-arrhythmogenic-disorders-short-qt-syndrome-and-early-repolarization
#20
REVIEW
Andrea Mazzanti, Katherine Underwood, Dmitriy Nevelev, Shanna Kofman, Silvia G Priori
Short QT syndrome (SQTS) is one of the rarest inheritable cardiac channelopathies, characterized by an accelerated cardiac repolarization, which is also the substrate for the development of life-threatening ventricular arrhythmias. Up to this date, fewer than 200 SQTS cases have been reported in the literature worldwide. Patients with SQTS may experience a cardiac arrest as early as in the neonatal period or as late as 80 years old. The cumulative probability of experiencing a cardiac arrest by the fifth decade of life approaches 40%, highlighting the importance of early recognition and management...
June 1, 2017: Journal of Cardiovascular Electrophysiology
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