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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/28764153/correlation-of-adiposity-indices-with-electrocardiographic-ventricular-variables-and-vascular-stiffness-in-young-adults
#2
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
#3
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...
July 25, 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-3d-microtissue-environment
#4
Celinda M Kofron, Tae Yun Kim, Michelle E King, An Xie, Feng Feng, Elizabeth Park, Zhilin Qu, Bum-Rak Choi, Ulrike Mende
Cardiac fibroblasts (CFs) are known to regulate cardiomyocyte (CM) function in vivo and in 2D in vitro cultures. This study examined the effect of CF activation on the regulation of CM electrical activity in a 3D microtissue environment. Using a scaffold-free 3D platform with interspersed neonatal rat ventricular CMs and CFs, Gq-mediated signaling was selectively enhanced in CFs by Gαq adenoviral infection prior to co-seeding with CMs in non-adhesive hydrogels. After 3 days, the microtissues were analyzed by signaling assay, histological staining, quantitative PCR, Western blots, optical mapping with voltage- or calcium-sensitive dyes, and microelectrode recordings of CF resting membrane potential (RMPCF)...
July 14, 2017: American Journal of Physiology. Heart and Circulatory Physiology
https://www.readbyqxmd.com/read/28695377/ventricular-dyssynchrony-assessment-using-ultra-high-frequency-ecg-technique
#5
Pavel Jurak, Josef Halamek, Jaroslav Meluzin, Filip Plesinger, Tereza Postranecka, Jolana Lipoldova, Miroslav Novak, Vlastimil Vondra, Ivo Viscor, Ladislav Soukup, Petr Klimes, Petr Vesely, Josef Sumbera, Karel Zeman, Roshini S Asirvatham, Jason Tri, Samuel J Asirvatham, Pavel Leinveber
PURPOSE: The aim of this proof-of-concept study is to introduce new high-dynamic ECG technique with potential to detect temporal-spatial distribution of ventricular electrical depolarization and to assess the level of ventricular dyssynchrony. METHODS: 5-kHz 12-lead ECG data was collected. The amplitude envelopes of the QRS were computed in an ultra-high frequency band of 500-1000 Hz and were averaged (UHFQRS). UHFQRS V lead maps were compiled, and numerical descriptor identifying ventricular dyssynchrony (UHFDYS) was detected...
September 2017: Journal of Interventional Cardiac Electrophysiology: An International Journal of Arrhythmias and Pacing
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/28689918/the-effects-of-deoxyelephantopin-on-the-cardiac-delayed-rectifier-potassium-channel-current-ikr-and-human-ether-a-go-go-related-gene-herg-expression
#7
Yi Fan Teah, Muhammad Asyraf Abduraman, Azimah Amanah, Mohd Ilham Adenan, Shaida Fariza Sulaiman, Mei Lan Tan
Elephantopus scaber Linn and its major bioactive component, deoxyelephantopin are known for their medicinal properties and are often reported to have various cytotoxic and antitumor activities. This plant is widely used as folk medicine for a plethora of indications although its safety profile remains unknown. Human ether-a-go-go-related gene (hERG) encodes the cardiac IKr current which is a determinant of the duration of ventricular action potentials and QT interval. The hERG potassium channel is an important antitarget in cardiotoxicity evaluation...
September 2017: Food and Chemical Toxicology
https://www.readbyqxmd.com/read/28675579/interlead-heterogeneity-of-r-and-t-wave-morphology-in-standard-12-lead-ecgs-predicts-sustained-ventricular-tachycardia-fibrillation-and-arrhythmic-death-in-patients-with-cardiomyopathy
#8
Alex Y Tan, Bruce D Nearing, Michael Rosenberg, Reza Nezafat, Mark E Josephson, Richard L Verrier
INTRODUCTION: Nonuniformities in depolarization and repolarization morphology are critical factors in ventricular arrhythmogenesis. METHODS AND RESULTS: We assessed interlead R-wave and T-wave heterogeneity (RWH, TWH) in standard 12-lead electrocardiograms using second central moment analysis. This technique quantifies variance about the mean morphology of beats in adjoining precordial leads, V4 , V5 , and V6 . The study was conducted in 120 consecutive patients without an apparent reversible trigger for VT, recent myocardial infarction, or active ischemia, who presented for electrophysiologic study, implantable cardioverter defibrillator (ICD) placement, or generator change at our institution from 2008 to 2011...
July 4, 2017: Journal of Cardiovascular Electrophysiology
https://www.readbyqxmd.com/read/28660734/the-association-of-qt-interval-components-with-atrial-fibrillation
#9
Nikhil Patel, Wesley T O'Neal, S Patrick Whalen, Elsayed Z Soliman
BACKGROUND: Although abnormalities of the QT interval are associated with atrial fibrillation (AF), it is unclear whether ventricular depolarization (QRS duration) or repolarization (JT interval) is a more important marker of AF risk. METHODS: This analysis included 4,181 (95% white; 59% women) participants from the Cardiovascular Health Study (CHS) who were free of baseline AF and major intraventricular delay. A linear scale was used to compute heart rate adjusted QT (QTa), QRS (QRSa ), and JT (JTa ) intervals...
June 29, 2017: Annals of Noninvasive Electrocardiology
https://www.readbyqxmd.com/read/28651797/left-ventricular-hypertrophy-by-the-surface-ecg
#10
REVIEW
Ljuba Bacharova, E Harvey Estes
Left ventricular hypertrophy (LVH) is defined as an increase in left ventricular mass (LVM) associated with structural changes of myocardium. The increase in LVM and associated changes are associated with changes in depolarization and repolarization, manifested as a variety of altered QRS and T patterns. Increased QRS voltage has been considered to be a specific ECG finding in LVH, and ECG criteria based on this increased QRS voltage are generally recommended. These ECG changes are also predictive of adverse cardiovascular outcomes...
June 7, 2017: Journal of Electrocardiology
https://www.readbyqxmd.com/read/28630170/characterization-of-aortic-valve-closure-artifact-during-outflow-tract-mapping-correlation-with-hemodynamics-and-mechanical-valves
#11
Jorge Romero, Olujimi Ajijola, Kalyanam Shivkumar, Roderick Tung
BACKGROUND: Premature ventricular contractions originating in the left ventricle outflow tract represent a significant subgroup of patients referred for catheter ablation. Mechanical artifacts from aortic valve leaflet motion may be observed during mapping, although the incidence and characteristics have not been reported. METHODS AND RESULTS: Twenty-eight consecutive patients with left ventricle outflow tract premature ventricular contraction were included. Electric signals recorded on the ablation catheter not coincident with atrial or ventricular depolarization were analyzed on the recording system...
June 2017: Circulation. Arrhythmia and Electrophysiology
https://www.readbyqxmd.com/read/28623610/a-singular-role-of-ik1-promoting-the-development-of-cardiac-automaticity-during-cardiomyocyte-differentiation-by-ik1-induced-activation-of-pacemaker-current
#12
Yu Sun, Valeriy Timofeyev, Adrienne Dennis, Emre Bektik, Xiaoping Wan, Kenneth R Laurita, Isabelle Deschênes, Ronald A Li, Ji-Dong Fu
The inward rectifier potassium current (IK1) is generally thought to suppress cardiac automaticity by hyperpolarizing membrane potential (MP). We recently observed that IK1 could promote the spontaneously-firing automaticity induced by upregulation of pacemaker funny current (If) in adult ventricular cardiomyocytes (CMs). However, the intriguing ability of IK1 to activate If and thereby promote automaticity has not been explored. In this study, we combined mathematical and experimental assays and found that only IK1 and If, at a proper-ratio of densities, were sufficient to generate rhythmic MP-oscillations even in unexcitable cells (i...
June 16, 2017: Stem Cell Reviews
https://www.readbyqxmd.com/read/28620067/allele-specific-silencing-of-mutant-mrna-rescues-ultrastructural-and-arrhythmic-phenotype-in-mice-carriers-of-the-r4496c-mutation-in-the-ryanodine-receptor-gene-ryr2
#13
Rossana Bongianino, Marco Denegri, Andrea Mazzanti, Francesco Lodola, Alessandra Vollero, Simona Boncompagni, Silvia Fasciano, Giulia Rizzo, Damiano Mangione, Serena Barbaro, Alessia Di Fonso, Carlo Napolitano, Alberto Auricchio, Feliciano Protasi, Silvia G Priori
Rationale: Mutations in the cardiac Ryanodine Receptor gene (RYR2) cause dominant Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT), a leading cause of sudden death in apparently healthy individuals exposed to emotions or physical exercise. Objective: We investigated the efficacy of allele specific silencing by RNA interference to prevent CPVT phenotypical manifestations in our dominant CPVT mice model carriers of the heterozygous mutation R4496C in RYR2Methods and Results: We developed an in vitro mRNA and protein-based assays to screen multiple siRNAs for their ability to selectively silence mutant RYR2-R4496C mRNA over the corresponding wild-type (WT) allele...
June 15, 2017: Circulation Research
https://www.readbyqxmd.com/read/28610987/tracking-interlead-heterogeneity-of-r-and-t-wave-morphology-to-disclose-latent-risk-for-sudden-cardiac-death
#14
Richard L Verrier, Heikki Huikuri
Sudden cardiac death (SCD) due primarily to ventricular fibrillation claims 1.5 million lives worldwide each year. In 45%-50% of cases, it is the first manifestation of underlying heart disease. Traditional risk factors including smoking, hypertension, age, sex, as well as depressed left ventricular ejection fraction lack sufficient sensitivity and specificity to forewarn of impending life-threatening arrhythmias. There has been a decades-long search for electrocardiographic (ECG) markers of SCD risk. Several interval-based indices such as QT dispersion and Tpeak-Tend interval held initial promise but ultimately yielded mixed results...
June 10, 2017: Heart Rhythm: the Official Journal of the Heart Rhythm Society
https://www.readbyqxmd.com/read/28557338/coronary-sinus-lead-delay-index-for-optimization-of-coronary-sinus-lead-placement
#15
Mevlüt Koç, Onur Kaypakli, Gökhan Gözübüyük, Durmus Yıldıray Şahin
AIM: Optimization of coronary sinus (CS) lead position to the latest activated left ventricular (LV) area is important to increase cardiac resynchronization therapy (CRT) response. We aimed to detect the relationship between coronary sinus lead delay index (CSDI) and echocardiographic, electrocardiographic response to CRT treatment. METHODS: We prospectively included 137 consecutive patients with heart failure (HF) diagnosis, QRS ≥ 120 ms, left bundle branch block (LBBB), New York Heart Association score (NYHA) II-IV, LV ejection fraction (LVEF) <35% and scheduled for CRT (84 male, 53 female; mean age 65...
May 30, 2017: Annals of Noninvasive Electrocardiology
https://www.readbyqxmd.com/read/28549786/action-potential-based-mea-platform-for-in-vitro-screening-of-drug-induced-cardiotoxicity-using-human-ipscs-and-rat-neonatal-myocytes
#16
Danny Jans, Geert Callewaert, Olga Krylychkina, Luis Hoffman, Francesco Gullo, Dimiter Prodanov, Dries Braeken
Drug-induced cardiotoxicity poses a negative impact on public health and drug development. Cardiac safety pharmacology issues urged for the preclinical assessment of drug-induced ventricular arrhythmia leading to the design of several in vitro electrophysiological screening assays. In general, patch clamp systems allow for intracellular recordings, while multi-electrode array (MEA) technology detect extracellular activity. Here, we demonstrate a complementary metal oxide semiconductor (CMOS)-based MEA system as a reliable platform for non-invasive, long-term intracellular recording of cardiac action potentials at high resolution...
May 23, 2017: Journal of Pharmacological and Toxicological Methods
https://www.readbyqxmd.com/read/28543106/the-concept-of-triple-wavefront-fusion-during-biventricular-pacing-using-the-egm-to-produce-the-best-acute-hemodynamic-improvement-in-crt
#17
Iris A H Ter Horst, Margot D Bogaard, Anton E Tuinenburg, Thomas P Mast, Teun P de Boer, Pieter A F M Doevendans, Mathias Meine
BACKGROUND: Previous reports suggest that biventricular pacing (BiVp) fused with intrinsic conduction (BiVp-fusion, triple wavefront fusion) is associated with improved resynchronization compared to pure-BiVp in cardiac resynchronization therapy (CRT). This study aimed to assess the association between acute hemodynamic benefit of CRT and signs of BiVp-fusion by using a novel electrogram (EGM)-based method. METHODS: In 17 patients undergoing CRT implantation, 28 combinations of atrioventricular (AV) and interventricular (VV) delays were applied while invasively measuring acute hemodynamic response based on maximum rate of left ventricular (LV) pressure rise (LV dP/dtmax ) to assess optimal BiVp settings...
May 23, 2017: Pacing and Clinical Electrophysiology: PACE
https://www.readbyqxmd.com/read/28542320/the-ik1-kir2-1-channel-agonist-zacopride-prevents-and-cures-acute-ischemic-arrhythmias-in-the-rat
#18
Xu-Wen Zhai, Li Zhang, Yun-Fei Guo, Ying Yang, Dong-Ming Wang, Yan Zhang, Pan Li, Yi-Fan Niu, Qi-Long Feng, Bo-Wei Wu, Ji-Min Cao, Qing-Hua Liu
Arrhythmogenesis in acute myocardial infarction (MI) is associated with depolarization of resting membraine potential (RMP) and decrease of inward rectifier potassium current (IK1) in cardiomyocytes. However, clinical anti-arrhythmic agents that primarily act on RMP by enhancing the IK1 channel are not currently available. We hypothesized that zacopride, a selective and moderate agonist of the IK1/Kir2.1 channels, prevents and cures acute ischemic arrhythmias. To test this viewpoint, adult Sprague-Dawley (SD) rats were subjected to MI by ligating the left main coronary artery...
2017: PloS One
https://www.readbyqxmd.com/read/28541596/effects-of-ivabradine-and-beta-blocker-therapy-on-dobutamine-induced-ventricular-arrhythmias
#19
Kadir Uğur Mert, Gurbet Özge Mert, Bektas Morrad, Senan Tahmazov, Fezan Mutlu, Yüksel Cavusoglu
BACKGROUND: Indirect evidences suggest that the If blocker (ivabradine) may exert an antiarrhythmic effect in ventricular myocardium in heart failure patients by inhibiting spontaneous depolarizations but the clinical relevance of this mechanism is not known. Dobutamine (DOB) has been known to increase heart rate and the incidence of cardiac arrhythmias. In this study, we evaluated the effects of ivabradine on DOB-induced ventricular arrhythmias and compared it with that of β blocker therapy...
May 25, 2017: Kardiologia Polska
https://www.readbyqxmd.com/read/28509708/pvcs-pvc-induced-cardiomyopathy-and-the-role-of-catheter-ablation
#20
Esseim Sharma, Karuppiah Arunachalam, Mengyang Di, Antony Chu, Abhishek Maan
Premature ventricular contractions (PVCs) are common arrhythmias noticed in the clinical setting because of premature depolarization of the ventricular myocytes. Although often thought to be reflective of underlying disease rather than intrinsically harmful, PVCs have recently been linked with worse outcomes in patients without significant cardiac disease. Long-term exposure to a high PVC burden can lead to the development of PVC-induced cardiomyopathy. The pathogenesis of this condition is poorly understood at the current time...
June 2017: Critical Pathways in Cardiology
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