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Cardiac alternans

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https://www.readbyqxmd.com/read/29237515/pulsus-alternans-in-a-child-with-dilated-cardiomyopathy
#1
Hasti Sanandajifar, Sarosh P Batlivala
A previously healthy 21-month-old presented with new-onset dilated cardiomyopathy. Evaluation noted pulsus alternans, with beat-to-beat alternations in aortic pulse wave amplitude, both clinically and on diagnostic studies. Pulsus alternans is an infrequent, complex pathophysiologic sign often associated with severe heart failure. The mechanisms are incompletely understood, but theorised aetiologies include beat-to-beat changes in left ventricular loading conditions, variations in myocardial oxygen supply/demand, and alternations in myocardial contractility...
December 14, 2017: Cardiology in the Young
https://www.readbyqxmd.com/read/29217432/transverse-tubular-network-structures-in-the-genesis-of-intracellular-calcium-alternans-and-triggered-activity-in-cardiac-cells
#2
Zhen Song, Michael B Liu, Zhilin Qu
RATIONALE: The major role of a transverse-tubular (TT) network in a cardiac cell is to facilitate effective excitation-contraction coupling and signaling. The TT network structures are heterogeneous within a single cell, and vary between different types of cells and species. They are also remodeled in cardiac diseases. However, how different TT network structures predispose cardiac cells to arrhythmogenesis remains to be revealed. OBJECTIVE: To systematically investigate the roles of TT network structure and the underlying mechanisms in the genesis of intracellular calcium (Ca2+) alternans and triggered activity (TA)...
December 4, 2017: Journal of Molecular and Cellular Cardiology
https://www.readbyqxmd.com/read/29212008/stochastic-pacing-inhibits-spatially-discordant-cardiac-alternans
#3
Dan Wilson, Bard Ermentrout
Depressed heart rate variability is a well-established risk factor for sudden cardiac death in survivors of acute myocardial infarction and for those with congestive heart failure. Although measurements of heart rate variability provide a valuable prognostic tool, it is unclear whether reduced heart rate variability itself is proarrhythmic or if it simply correlates with the severity of autonomic nervous system dysfunction. In this work, we investigate a possible mechanism by which heart rate variability could protect against cardiac arrhythmia...
December 5, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/29194862/a-case-report-is-mexiletine-usage-effective-in-the-shortening-of-qtc-interval-and-improving-the-t-wave-alternans-in-timothy-syndrome
#4
Gulhan Tunca Sahin, Yakup Ergul
Timothy syndrome (TS) is a multisystemic disease that occurs because of a mutation in CACN1C gene and is characterized by prolonged QT interval. Mexiletine is a Class 1B antiarrhythmic drug that causes the disappearance of T-wave alternans by shortening QTc and peak-to-end of the T wave. It may block the development of torsades de pointes in a prolonged QT. This study presented the case of a patient diagnosed with TS and had a cardiac arrest history, prolonged QT, and T-wave alternans. After mexiletine treatment, the QTc interval shortened and T-wave alternans disappeared...
November 30, 2017: Annals of Noninvasive Electrocardiology
https://www.readbyqxmd.com/read/29170159/reduced-expression-of-cardiac-ryanodine-receptor-protects-against-stress-induced-ventricular-tachyarrhythmia-but-increases-the-susceptibility-to-cardiac-alternans
#5
Xiaowei Zhong, Alexander Vallmitjana, Bo Sun, Zhichao Xiao, Wenting Guo, Jinhong Wei, Mingke Ni, Yongxiang Chen, Edward R O'Brien, Anne M Gillis, Masahiko Hoshijima, Hiroshi Takeshima, Leif Hove-Madsen, Raul Benitez, Darrell Belke, S R Wayne Chen
Reduced protein expression of the cardiac ryanodine receptor (RyR2) is thought to affect the susceptibility to stress-induced ventricular tachyarrhythmia (VT) and cardiac alternans, but direct evidence for the role of RyR2 protein expression in VT and cardiac alternans is lacking. Here we used a mouse model ( crrm1) that expresses a reduced level of the RyR2 protein to determine the impact of reduced RyR2 protein expression on the susceptibility to VT, cardiac alternans, cardiac hypertrophy, and sudden death...
November 23, 2017: Biochemical Journal
https://www.readbyqxmd.com/read/29150491/hypothermia-modulates-arrhythmia-substrates-during-different-phases-of-resuscitation-from-ischemic-cardiac-arrest
#6
Joseph S Piktel, Aurelia Cheng, Matthew McCauley, Zack Dale, Michelle Nassal, Danielle Maleski, Gary Pawlowski, Kenneth R Laurita, Lance D Wilson
BACKGROUND: We designed an innovative porcine model of ischemia-induced arrest to determine dynamic arrhythmia substrates during focal infarct, global ischemia from ventricular tachycardia or fibrillation (VT/VF) and then reperfusion to determine the effect of therapeutic hypothermia (TH) on dynamic arrhythmia substrates and resuscitation outcomes. METHODS AND RESULTS: Anesthetized adult pigs underwent thoracotomy and regional plunge electrode placement in the left ventricle...
November 17, 2017: Journal of the American Heart Association
https://www.readbyqxmd.com/read/29129349/electrical-and-mechanical-alternans-during-ventricular-tachycardia-with-moderate-chronic-heart-failure
#7
Ikeotunye Royal Chinyere, Talal Moukabary, Steven Goldman, Elizabeth Juneman
A chronic heart failure (CHF) rat underwent epicardial programmed electrical stimulation (PES). Ventricular tachycardia (VT) developed during PES. Mechanical alternans was noted despite fixed tachycardia cycle length. Anti-tachycardia pacing attempts initiated a second VT that generated pulse intermittently and then degenerated into pulseless VT with electrical alternans.To our knowledge electrical and mechanical alternans have not been recorded in animal models of CHF during VT. The distinct events of mechanical alternans and electrical alternans may be indicative of progressively worsened calcium handling in the compromised cardiomyocytes...
September 23, 2017: Journal of Electrocardiology
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
#8
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/29037423/unique-ecg-presentations-and-clinical-management-of-a-symptomatic-lqt2-female-carrying-a-novel-de-novo-kcnh2-mutation
#9
Chunlin Yin, Ping Zhang, Jing Yang, Li Zhang
A 26-year-old woman, 12 days in postpartum, developed recurrent syncope and cardiac arrest. Her ECG revealed QT-prolongation associated with LQT2-specific T-U wave patterns, T wave alternans, long QT-dependent torsade de pointes (TdP) and ventricular fibrillation (VF). She also had intermittent LBBB (80bpm) on alternate beats and RBBB at sinus tachycardia (113bpm). Family genotyping revealed a novel de novo missense mutation G604C of KCNH2. Propranolol slowed heart rate and further prolonged QT interval (610ms) that caused TdP recurrence...
August 17, 2017: Journal of Electrocardiology
https://www.readbyqxmd.com/read/29020031/sudden-cardiac-death-and-pump-failure-death-prediction-in-chronic-heart-failure-by-combining-ecg-and-clinical-markers-in-an-integrated-risk-model
#10
Julia Ramírez, Michele Orini, Ana Mincholé, Violeta Monasterio, Iwona Cygankiewicz, Antonio Bayés de Luna, Juan Pablo Martínez, Pablo Laguna, Esther Pueyo
BACKGROUND: Sudden cardiac death (SCD) and pump failure death (PFD) are common endpoints in chronic heart failure (CHF) patients, but prevention strategies are different. Currently used tools to specifically predict these endpoints are limited. We developed risk models to specifically assess SCD and PFD risk in CHF by combining ECG markers and clinical variables. METHODS: The relation of clinical and ECG markers with SCD and PFD risk was assessed in 597 patients enrolled in the MUSIC (MUerte Súbita en Insuficiencia Cardiaca) study...
2017: PloS One
https://www.readbyqxmd.com/read/28989116/complex-restitution-behavior-and-reentry-in-a-cardiac-tissue-model-for-neonatal-mice
#11
Andreas Mayer, Philip Bittihn, Stefan Luther
Spatiotemporal dynamics in cardiac tissue emerging from the coupling of individual cardiomyocytes underlie the heart's normal rhythm as well as undesired and possibly life-threatening arrhythmias. While single cells and their transmembrane currents have been studied extensively, systematically investigating spatiotemporal dynamics is complicated by the nontrivial relationship between single-cell and emergent tissue properties. Mathematical models have been employed to bridge this gap and contribute to a deepened understanding of the onset, development, and termination of arrhythmias...
October 2017: Physiological Reports
https://www.readbyqxmd.com/read/28964198/a-multichannel-decision-level-fusion-method-for-t-wave-alternans-detection
#12
Changrong Ye, Xiaoping Zeng, Guojun Li, Chenyuan Shi, Xin Jian, Xichuan Zhou
Sudden cardiac death (SCD) is one of the most prominent causes of death among patients with cardiac diseases. Since ventricular arrhythmia is the main cause of SCD and it can be predicted by T wave alternans (TWA), the detection of TWA in the body-surface electrocardiograph (ECG) plays an important role in the prevention of SCD. But due to the multi-source nature of TWA, the nonlinear propagation through thorax, and the effects of the strong noises, the information from different channels is uncertain and competitive with each other...
September 2017: Review of Scientific Instruments
https://www.readbyqxmd.com/read/28964162/temperature-geometry-and-bifurcations-in-the-numerical-modeling-of-the-cardiac-mechano-electric-feedback
#13
A Collet, J Bragard, P C Dauby
This article characterizes the cardiac autonomous electrical activity induced by the mechanical deformations in the cardiac tissue through the mechano-electric feedback. A simplified and qualitative model is used to describe the system and we also account for temperature effects. The analysis emphasizes a very rich dynamics for the system, with periodic solutions, alternans, chaotic behaviors, etc. The possibility of self-sustained oscillations is analyzed in detail, particularly in terms of the values of important parameters such as the dimension of the system and the importance of the stretch-activated currents...
September 2017: Chaos
https://www.readbyqxmd.com/read/28964160/effects-of-model-error-on-cardiac-electrical-wave-state-reconstruction-using-data-assimilation
#14
Nicholas S LaVigne, Nathan Holt, Matthew J Hoffman, Elizabeth M Cherry
Reentrant electrical scroll waves have been shown to underlie many cardiac arrhythmias, but the inability to observe locations away from the heart surfaces and the restriction of observations to only one or two state variables have made understanding arrhythmia mechanisms challenging. Recently, we showed that data assimilation from spatiotemporally sparse surrogate observations could be used to reconstruct a reliable time series of state estimates of reentrant cardiac electrical waves including unobserved variables in one and three spatial dimensions...
September 2017: Chaos
https://www.readbyqxmd.com/read/28964159/distinguishing-mechanisms-for-alternans-in-cardiac-cells-using-constant-diastolic-interval-pacing
#15
Elizabeth M Cherry
Alternans, a proarrhythmic dynamical state in which cardiac action potentials alternate between long and short durations despite a constant pacing period, traditionally has been explained at the cellular level using nonlinear dynamics principles under the assumption that the action potential duration (APD) is determined solely by the time elapsed since the end of the previous action potential, called the diastolic interval (DI). In this scenario, APDs at a steady state should be the same provided that the preceding DIs are the same...
September 2017: Chaos
https://www.readbyqxmd.com/read/28964152/minimal-model-for-calcium-alternans-due-to-sr-release-refractoriness
#16
Inma R Cantalapiedra, Enrique Alvarez-Lacalle, Angelina Peñaranda, Blas Echebarria
In the heart, rapid pacing rates may induce alternations in the strength of cardiac contraction, termed pulsus alternans. Often, this is due to an instability in the dynamics of the intracellular calcium concentration, whose transients become larger and smaller at consecutive beats. This alternation has been linked experimentally and theoretically to two different mechanisms: an instability due to (1) a strong dependence of calcium release on sarcoplasmic reticulum (SR) load, together with a slow calcium reuptake into the SR or (2) to SR release refractoriness, due to a slow recovery of the ryanodine receptors (RyR2) from inactivation...
September 2017: Chaos
https://www.readbyqxmd.com/read/28964144/constant-di-pacing-suppresses-cardiac-alternans-formation-in-numerical-cable-models
#17
S Zlochiver, C Johnson, E G Tolkacheva
Cardiac repolarization alternans describe the sequential alternation of the action potential duration (APD) and can develop during rapid pacing. In the ventricles, such alternans may rapidly turn into life risking arrhythmias under conditions of spatial heterogeneity. Thus, suppression of alternans by artificial pacing protocols, or alternans control, has been the subject of numerous theoretical, numerical, and experimental studies. Yet, previous attempts that were inspired by chaos control theories were successful only for a short spatial extent (<2 cm) from the pacing electrode...
September 2017: Chaos
https://www.readbyqxmd.com/read/28964143/memory-in-a-fractional-order-cardiomyocyte-model-alters-properties-of-alternans-and-spontaneous-activity
#18
T Comlekoglu, S H Weinberg
Cardiac memory is the dependence of electrical activity on the prior history of one or more system state variables, including transmembrane potential (Vm), ionic current gating, and ion concentrations. While prior work has represented memory either phenomenologically or with biophysical detail, in this study, we consider an intermediate approach of a minimal three-variable cardiomyocyte model, modified with fractional-order dynamics, i.e., a differential equation of order between 0 and 1, to account for history-dependence...
September 2017: Chaos
https://www.readbyqxmd.com/read/28964128/theory-of-the-development-of-alternans-in-the-heart-during-controlled-diastolic-interval-pacing
#19
Niels F Otani
The beat-to-beat alternation in action potential durations (APDs) in the heart, called APD alternans, has been linked to the development of serious cardiac rhythm disorders, including ventricular tachycardia and fibrillation. The length of the period between action potentials, called the diastolic interval (DI), is a key dynamical variable in the standard theory of alternans development. Thus, methods that control the DI may be useful in preventing dangerous cardiac rhythms. In this study, we examine the dynamics of alternans during controlled-DI pacing using a series of single-cell and one-dimensional (1D) fiber models of alternans dynamics...
September 2017: Chaos
https://www.readbyqxmd.com/read/28964124/alternans-promotion-in-cardiac-electrophysiology-models-by-delay-differential-equations
#20
Johnny M Gomes, Rodrigo Weber Dos Santos, Elizabeth M Cherry
Cardiac electrical alternans is a state of alternation between long and short action potentials and is frequently associated with harmful cardiac conditions. Different dynamic mechanisms can give rise to alternans; however, many cardiac models based on ordinary differential equations are not able to reproduce this phenomenon. A previous study showed that alternans can be induced by the introduction of delay differential equations (DDEs) in the formulations of the ion channel gating variables of a canine myocyte model...
September 2017: Chaos
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