Read by QxMD icon Read

Cardiac alternans

Gurunath Parale, Chinmay Parale
No abstract text is available yet for this article.
October 17, 2016: European Journal of Internal Medicine
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
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
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
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
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
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
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...
September 2, 2016: Cell Calcium
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
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
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
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
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
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
Richard L Verrier, Bruce D Nearing, Bryan Olin, Paul Boon, Steven C Schachter
OBJECTIVE: Reports of cardiac arrhythmias and cardiac pathology at postmortem examination of patients with epilepsy suggest a possible cardiac component of risk for sudden unexpected death in epilepsy (SUDEP). T-wave alternans (TWA) is an established marker of cardiac electrical instability and risk for sudden death in patients with cardiovascular disease. We determined the TWA level before vagus nerve stimulation (VNS) system implantation and subsequently the effect of VNS on TWA in patients with drug-resistant epilepsy...
September 2016: Epilepsy & Behavior: E&B
Aapo L Aro, Tuomas V Kenttä, Heikki V Huikuri
Microvolt T-wave alternans (TWA), characterised as beat-to-beat fluctuation of T-wave amplitude and morphology, is an electrophysiological phenomenon associated clinically with impending ventricular arrhythmias and is an important marker of arrhythmia risk. Currently, two main methods for the detection of TWA exist, namely, the spectral method and the time-domain modified moving average method; both are discussed in this review. Microvolt TWA has been associated with cardiovascular mortality and sudden cardiac death in several clinical studies involving >14,000 subjects with reduced as well as preserved left ventricular function...
May 2016: Arrhythmia & Electrophysiology Review
Seth H Weinberg
Cardiac electrical dynamics are governed by cellular-level properties, such as action potential duration (APD) restitution and intracellular calcium (Ca) handling, and tissue-level properties, including conduction velocity restitution and cell-cell coupling. Irregular dynamics at the cellular level can lead to instabilities in cardiac tissue, including alternans, a beat-to-beat alternation in the action potential and/or the intracellular Ca transient. In this study, we incorporate a detailed single cell coupled map model of Ca cycling and bidirectional APD-Ca coupling into a spatially extended tissue model to investigate the influence of sarcoplasmic reticulum (SR) Ca uptake and release properties on alternans and conduction block...
2016: Clinical Medicine Insights. Cardiology
Nele Vandersickel, Arne Defauw, Peter Dawyndt, Alexander V Panfilov
The main mechanism of formation of reentrant cardiac arrhythmias is via formation of waveblocks at heterogeneities of cardiac tissue. We report that heterogeneity and the area of waveblock can extend itself in space and can result formation of new additional sources, or termination of existing sources of arrhythmias. This effect is based on a new form of instability, which we coin as global alternans instability (GAI). GAI is closely related to the so-called (discordant) alternans instability, however its onset is determined by the global properties of the APD-restitution curve and not by its slope...
2016: Scientific Reports
Y Huang, D-N Wang, P Liu, Y Song, H-M Cui, J-Y Zhang, J Blackwell, D-N Liao
OBJECTIVE: To observe the effects of local radiofrequency denervation on ventricular effective refractory periods, electrical alternans and ventricular arrhythmia susceptibility post myocardial infarction. MATERIALS AND METHODS: Thirty-four mongrel dogs were randomly divided into the normal heart group (n = 16, 8 in sham and 8 in local sympathetic denervation - LSD) and the acute myocardial ischemia (AMI) group (n = 18, 9 in control and 9 in LSD). The left cardiac sympathetic nerve was denervated with irrigated catheter radiofrequency ablation...
June 2016: European Review for Medical and Pharmacological Sciences
Giedrius Kanaporis, Lothar A Blatter
Cardiac alternans, defined beat-to-beat alternations in contraction, action potential (AP) morphology or cytosolic Ca transient (CaT) amplitude, is a high risk indicator for cardiac arrhythmias. We investigated mechanisms of cardiac alternans in single rabbit ventricular myocytes. CaTs were monitored simultaneously with membrane currents or APs recorded with the patch clamp technique. A strong correlation between beat-to-beat alternations of AP morphology and CaT alternans was observed. During CaT alternans application of voltage clamp protocols in form of pre-recorded APs revealed a prominent Ca(2+)-dependent membrane current consisting of a large outward component coinciding with AP phases 1 and 2, followed by an inward current during AP repolarization...
November 2016: Channels
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"