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Cardiac alternans

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https://www.readbyqxmd.com/read/27916321/exercise-induced-quantitative-microvolt-t-wave-alternans-in-hypertrophic-cardiomyopathy
#1
Murillo de Oliveira Antunes, Nelson Samesima, Horacio Gomes Pereira Filho, Afonso Yoshikiro Matsumoto, Richard L Verrier, Carlos Alberto Pastore, Edmundo Arteaga-Fernández, Charles Mady
BACKGROUND/PURPOSE: Patients with hypertrophic cardiomyopathy (HCM) have elevated risk for sudden cardiac death (SCD). Our study aimed to quantitatively characterize microvolt T-wave alternans (TWA), a potential arrhythmia risk stratification tool, in this HCM patient population. METHODS: TWA was analyzed with the quantitative modified moving average (MMA) in 132 HCM patients undergoing treadmill exercise testing, grouped according to Maron score risk factors as high-risk (H-Risk, n=67,), or low-risk (L-Risk, n=65, without these risk factors)...
October 28, 2016: Journal of Electrocardiology
https://www.readbyqxmd.com/read/27914945/effects-of-zacopride-a-moderate-ik1-channel-agonist-on-triggered-arrhythmia-and-contractility-in-human-ventricular-myocardium
#2
Mohammad T Elnakish, Benjamin D Canan, Ahmet Kilic, Peter J Mohler, Paul M L Janssen
Ventricular tachycardia is the leading cause of sudden arrhythmic death in the U.S. Recently, the moderate IK1 channel activator, zacopride, was shown to suppress triggered ventricular tachycardia in rats. Nonetheless, concerns were raised about the possibility of pro-arrhythmic activity after IK1 channel stimulation based on the promising anti-arrhythmic strategy of IK1 blockade in other animal models. Therefore, the goal of the current study was to investigate the ex-vivo effects of zacopride on triggered arrhythmia and contractility in ventricular human myocardium in order to validate data that was solely obtained from animal models...
November 30, 2016: Pharmacological Research: the Official Journal of the Italian Pharmacological Society
https://www.readbyqxmd.com/read/27902841/dynamical-effects-of-calcium-sensitive-potassium-currents-on-voltage-and-calcium-alternans
#3
Matthew Kennedy, Donald M Bers, Nipavan Chiamvimonvat, Daisuke Sato
Cardiac alternans is a precursor to life-threatening arrhythmias. Alternans can be caused by instability of the membrane voltage (Vm ), instability of the intracellular Ca (Cai ) cycling, or both. Vm dynamics and Cai dynamics are coupled via Ca-sensitive currents. In cardiac myocytes, there are several Ca-sensitive potassium (K) currents such as the slowly activating delayed rectifier current (IKs ) and the small conductance Ca-activated potassium (SK) current (ISK ). However, the role of these currents in the development of arrhythmias is not well understood...
November 30, 2016: Journal of Physiology
https://www.readbyqxmd.com/read/27879279/heart-rate-turbulence-is-a-powerful-predictor-of-cardiac-death-and-ventricular-arrhythmias-in-postmyocardial-infarction-and-heart-failure-patients-a-systematic-review-and-meta-analysis
#4
Marcello Disertori, Michela Masè, Marta Rigoni, Giandomenico Nollo, Flavia Ravelli
BACKGROUND: Heart rate turbulence (HRT) has been proposed as a candidate marker of altered autonomic tone, and some studies showed its prognostic value for both cardiac death (CD) and sudden death. Nevertheless, HRT is not currently used in the clinical practice. METHODS AND RESULTS: We performed a systematic review and meta-analysis of the predictive value of HRT for the end points of total mortality, CD, and fatal and nonfatal ventricular arrhythmias in postacute myocardial infarction and heart failure patients...
December 2016: Circulation. Arrhythmia and Electrophysiology
https://www.readbyqxmd.com/read/27778458/t-wave-alternans-heart-rate-turbulence-and-ventricular-ectopy-in-standard-versus-daily-hemodialysis-results-from-the-fhn-daily-trial
#5
Rachel M Kaplan, Charles A Herzog, Brett Larive, Haris Subacius, Bruce D Nearing, Richard Verrier, Rod S Passman
BACKGROUND: Hemodialysis (HD) patients are at high risk of sudden cardiac death (SCD). HD 6-times/week (6x/wk) may reduce SCD risk compared to usual 3-times/week HD (3x/wk) by mechanisms unknown. T-wave alternans (TWA), heart rate turbulence (HRT), and ventricular ectopy (VE) are elevated in HD patients, but their response to 6x/wk HD has not been assessed. METHODS: Baseline and 1-year Holter recordings were analyzed from enrollees in the Frequent Hemodialysis Network Daily Trial, a randomized trial comparing 3x/wk to 6x/wk in 245 chronic HD patients...
November 2016: Annals of Noninvasive Electrocardiology
https://www.readbyqxmd.com/read/27777148/eleclazine-an-inhibitor-of-the-cardiac-late-sodium-current-is-superior-to-flecainide-in-suppressing-catecholamine-induced-ventricular-tachycardia-and-t-wave-alternans-in-an-intact-porcine-model
#6
Danilo Bacic, Juliana Saran Carneiro, Afonso Alves Bento, Bruce D Nearing, Sridharan Rajamani, Luiz Belardinelli, Richard L Verrier
BACKGROUND: The capacity of catecholamines to induce ventricular tachycardia (VT) is well documented. OBJECTIVE: The effectiveness of the novel cardiac late sodium inhibitor eleclazine in suppressing catecholamine-induced VT in a large animal model was compared with that of flecainide. METHODS: In 13 closed-chest anesthetized Yorkshire pigs, spontaneous VT and surges in T-wave alternans (TWA) level measured using the modified moving average method were induced by epinephrine (2...
October 21, 2016: Heart Rhythm: the Official Journal of the Heart Rhythm Society
https://www.readbyqxmd.com/read/27765387/t-wave-alternans-an-ominous-marker-for-malignant-cardiac-arrhythmias
#7
Gurunath Parale, Chinmay Parale
No abstract text is available yet for this article.
October 17, 2016: European Journal of Internal Medicine
https://www.readbyqxmd.com/read/27761166/cardiac-dynamics-alternans-and-arrhythmogenesis
#8
REVIEW
Gary Tse, Sheung Ting Wong, Vivian Tse, Yee Ting Lee, Hiu Yu Lin, Jie Ming Yeo
Pre-existing heterogeneities present in cardiac tissue are essential for maintaining the normal electrical and mechanical functions of the heart. Exacerbation of such heterogeneities or the emergence of dynamic factors can produce repolarization alternans, which are beat-to-beat alternations in the action potential time course. Traditionally, this was explained by restitution, but additional factors, such as cardiac memory, calcium handling dynamics, refractory period restitution, and mechano-electric feedback, are increasingly recognized as the underlying causes...
October 2016: Journal of Arrhythmia
https://www.readbyqxmd.com/read/27749895/a-parsimonious-model-of-the-rabbit-action-potential-elucidates-the-minimal-physiological-requirements-for-alternans-and-spiral-wave-breakup
#9
Richard A Gray, Pras Pathmanathan
Elucidating the underlying mechanisms of fatal cardiac arrhythmias requires a tight integration of electrophysiological experiments, models, and theory. Existing models of transmembrane action potential (AP) are complex (resulting in over parameterization) and varied (leading to dissimilar predictions). Thus, simpler models are needed to elucidate the "minimal physiological requirements" to reproduce significant observable phenomena using as few parameters as possible. Moreover, models have been derived from experimental studies from a variety of species under a range of environmental conditions (for example, all existing rabbit AP models incorporate a formulation of the rapid sodium current, INa, based on 30 year old data from chick embryo cell aggregates)...
October 2016: PLoS Computational Biology
https://www.readbyqxmd.com/read/27739779/nonlinear-onset-of-calcium-wave-propagation-in-cardiac-cells
#10
Yohannes Shiferaw
Spontaneous calcium (Ca) waves in cardiac myocytes are known to underlie a wide range of cardiac arrhythmias. However, it is not understood which physiological parameters determine the onset of waves. In this study, we explore the relationship between Ca signaling between ion channels and the nucleation of Ca waves. In particular, we apply a master equation approach to analyze the stochastic interaction between neighboring clusters of ryanodine receptor (RyR) channels. Using this analysis, we show that signaling between clusters can be described as a barrier hopping process with exponential sensitivity to system parameters...
September 2016: Physical Review. E
https://www.readbyqxmd.com/read/27727036/an-unusual-case-of-alternating-ventricular-morphology-on-the-12-lead-electrocardiogram
#11
Maura Sammon, Alveena Dawood, Scott Beaudoin, Richard A Harrigan
BACKGROUND: One of the principal tasks of an emergency physician is identifying potentially life-threatening conditions in the undifferentiated patient; cardiac dysrhythmia is an example of such a condition. A systematic approach to a patient with atypical dysrhythmia enables proper identification of such-life threatening conditions. CASE REPORT: We describe a 31-year-old man presenting to the emergency department with an undifferentiated dysrhythmia after naloxone reversal of an opiate overdose...
October 7, 2016: Journal of Emergency Medicine
https://www.readbyqxmd.com/read/27702850/traditional-and-novel-electrocardiographic-conduction-and-repolarization-markers-of-sudden-cardiac-death
#12
Gary Tse, Bryan P Yan
Sudden cardiac death, frequently due to ventricular arrhythmias, is a significant problem globally. Most affected individuals do not arrive at hospital in time for medical treatment. Therefore, there is an urgent need to identify the most-at-risk patients for insertion of prophylactic implantable cardioverter defibrillators. Clinical risk markers derived from electrocardiography are important for this purpose. They can be based on repolarization, including corrected QT (QTc) interval, QT dispersion (QTD), interval from the peak to the end of the T-wave (Tpeak - Tend), (Tpeak - Tend)/QT, T-wave alternans (TWA), and microvolt TWA...
October 4, 2016: Europace: European Pacing, Arrhythmias, and Cardiac Electrophysiology
https://www.readbyqxmd.com/read/27660578/surface-electrocardiogram-predictors-of-sudden-cardiac-arrest
#13
REVIEW
Samy A Abdelghani, Todd M Rosenthal, Daniel P Morin
BACKGROUND: Heart disease is a major cause of death in industrialized nations, with approximately 50% of these deaths attributable to sudden cardiac arrest. If patients at high risk for sudden cardiac arrest can be identified, their odds of surviving fatal arrhythmias can be significantly improved through prophylactic implantable cardioverter defibrillator placement. This review summarizes the current knowledge pertaining to surface electrocardiogram (ECG) predictors of sudden cardiac arrest...
2016: Ochsner Journal
https://www.readbyqxmd.com/read/27616659/involvement-of-mitochondrial-permeability-transition-pore-mptp-in-cardiac-arrhythmias-evidence-from-cyclophilin-d-knockout-mice
#14
Richard Gordan, Nadezhda Fefelova, Judith K Gwathmey, Lai-Hua Xie
In the present study, we have used a genetic mouse model that lacks cyclophilin D (CypD KO) to assess the cardioprotective effect of mitochondrial permeability transition pore (mPTP) inhibition on Ca(2+) waves and Ca(2+) alternans at the single cell level, and cardiac arrhythmias in whole-heart preparations. The protonophore carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP) caused mitochondrial membrane potential depolarization to the same extent in cardiomyocytes from both WT and CypD KO mice, however, cardiomyocytes from CypD KO mice exhibited significantly less mPTP opening than cardiomyocytes from WT mice (p<0...
December 2016: Cell Calcium
https://www.readbyqxmd.com/read/27597389/does-manual-t-wave-window-adjustment-affect-microvolt-t-wave-alternans-results-in-patients-with-structural-heart-disease
#15
Tharmathai Ramanan, Kathir Balakumaran, Sairekha Ravichandran, Stephen J Ganocy, Ganiyu Oshodi, Otto Costantini, Mary Dettmer, Peter J Leo, Elizabeth S Kaufman
INTRODUCTION: Microvolt T-wave alternans (MTWA) analysis can identify patients at low risk of sudden cardiac death who might not benefit from an implantable cardioverter-defibrillator (ICD). Current spectral methodology for performing MTWA analysis may "miss" part of the T-wave in patients with QT prolongation. The value of T-wave window adjustment in patients with structural heart disease has not been studied. METHODS: We assembled MTWA data from 5 prior prospective studies including 170 patients with reduced left ventricular ejection fraction, adjusted the T-wave window to include the entire T-wave, and reanalyzed MTWA...
August 4, 2016: Journal of Electrocardiology
https://www.readbyqxmd.com/read/27590098/hiv-tat-induces-a-decrease-in-ikr-and-iksvia-reduction-in-phosphatidylinositol-4-5-bisphosphate-availability
#16
Zeineb Es-Salah-Lamoureux, Mariam Jouni, Olfat A Malak, Nadjet Belbachir, Zeina Reda Al Sayed, Marine Gandon-Renard, Guillaume Lamirault, Chantal Gauthier, Isabelle Baró, Flavien Charpentier, Kazem Zibara, Patricia Lemarchand, Bruno Beaumelle, Nathalie Gaborit, Gildas Loussouarn
Patients with HIV present with a higher prevalence of QT prolongation, of which molecular bases are still not clear. Among HIV proteins, Tat serves as a transactivator that stimulates viral genes expression and is required for efficient HIV replication. Tat is actively secreted into the blood by infected T-cells and affects organs such as the heart. Tat has been shown to alter cardiac repolarization in animal models but how this is mediated and whether this is also the case in human cells is unknown. In the present study, we show that Tat transfection in heterologous expression systems led to a decrease in hERG (underlying cardiac IKr) and human KCNE1-KCNQ1 (underlying cardiac IKs) currents and to an acceleration of their deactivation...
August 30, 2016: Journal of Molecular and Cellular Cardiology
https://www.readbyqxmd.com/read/27582498/suppression-of-ryanodine-receptor-function-prolongs-ca2-release-refractoriness-and-promotes-cardiac-alternans-in-intact-hearts
#17
Xiaowei Zhong, Bo Sun, Alexander Vallmitjana, Tao Mi, Wenting Guo, Mingke Ni, Ruiwu Wang, Ang Guo, Henry J Duff, Anne M Gillis, Long-Sheng Song, Leif Hove-Madsen, Raul Benitez, S R Wayne Wayne Chen
Beat-to-beat alternations in the amplitude of the cytosolic Ca(2+) transient (Ca(2+) alternans) are thought to be the primary cause of cardiac alternans that can lead to cardiac arrhythmias and sudden death. Despite its important role in arrhythmogenesis, the mechanism underlying Ca(2+) alternans remains poorly understood. Here we investigated the role of cardiac ryanodine receptor (RyR2), the major Ca(2+) release channel responsible for cytosolic Ca(2+) transients, in cardiac alternans. Using a unique mouse model harboring a suppression-of-function (SOF) RyR2 mutation (E4872Q), we assessed the effect of genetically suppressing RyR2 function on Ca(2+) and action potential duration (APD) alternans in intact hearts, and electrocardiogram (ECG) alternans in vivo...
August 31, 2016: Biochemical Journal
https://www.readbyqxmd.com/read/27554424/electrocardiographic-predictors-of-mortality-and-sudden-cardiac-death-in-patients-with-end-stage-renal-disease-on-hemodialysis
#18
Jonathan W Waks, Larisa G Tereshchenko, Rulan S Parekh
Patients with end stage renal disease (ESRD) on hemodialysis experience a high incidence of cardiovascular mortality, and sudden cardiac death (SCD) accounts for approximately 25% of all deaths in this patient population. Despite this high risk of SCD, many non-invasive SCD risk stratification tools that are frequently applied to other patient populations (such as those with prior myocardial infarction and reduced left ventricular systolic function) may be less useful markers of increased SCD risk in ESRD. Improved SCD risk stratification tools for use specifically in patients on hemodialysis are therefore necessary to optimally target use of primary prevention interventions aimed at decreasing SCD incidence...
July 28, 2016: Journal of Electrocardiology
https://www.readbyqxmd.com/read/27517161/nonlinear-physics-of-electrical-wave-propagation-in-the-heart-a-review
#19
Sergio Alonso, Markus Bär, Blas Echebarria
The beating of the heart is a synchronized contraction of muscle cells (myocytes) that is triggered by a periodic sequence of electrical waves (action potentials) originating in the sino-atrial node and propagating over the atria and the ventricles. Cardiac arrhythmias like atrial and ventricular fibrillation (AF,VF) or ventricular tachycardia (VT) are caused by disruptions and instabilities of these electrical excitations, that lead to the emergence of rotating waves (VT) and turbulent wave patterns (AF,VF)...
September 2016: Reports on Progress in Physics
https://www.readbyqxmd.com/read/27489981/beat-to-beat-t-wave-alternans-detection-using-the-ensemble-empirical-mode-decomposition-method
#20
Muhammad A Hasan, Vijay S Chauhan, Sridhar Krishnan
BACKGROUND: T-wave alternans (TWA) is defined as a consistent variation in the repolarization morphology that repeats on every other beat. This study aimed to evaluate beat-to-beat TWA detection using the Ensemble EMD (EEMD) method. METHOD: A total of 108 recordings of standard 12-lead ECGs of 69 healthy subjects (17 females, 42±18 years; 52 males, 40±13 years) and 39 cardiac-condition patients (ischemic cardiomyopathy; ICM and dilated cardiomyopathy; DCM) with left ventricular ejection fractions (LVEF) ≤40% were studied...
October 1, 2016: Computers in Biology and Medicine
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