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Cardiac alternans

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https://www.readbyqxmd.com/read/29129349/electrical-and-mechanical-alternans-during-ventricular-tachycardia-with-moderate-chronic-heart-failure
#1
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
#2
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
#3
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
#4
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
#5
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
#6
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
#7
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
#8
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
#9
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
#10
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
#11
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
#12
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
#13
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
#14
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
https://www.readbyqxmd.com/read/28964122/a-computational-framework-for-testing-arrhythmia-marker-sensitivities-to-model-parameters-in-functionally-calibrated-populations-of-atrial-cells
#15
Márcia R Vagos, Hermenegild Arevalo, Bernardo Lino de Oliveira, Joakim Sundnes, Mary M Maleckar
Models of cardiac cell electrophysiology are complex non-linear systems which can be used to gain insight into mechanisms of cardiac dynamics in both healthy and pathological conditions. However, the complexity of cardiac models can make mechanistic insight difficult. Moreover, these are typically fitted to averaged experimental data which do not incorporate the variability in observations. Recently, building populations of models to incorporate inter- and intra-subject variability in simulations has been combined with sensitivity analysis (SA) to uncover novel ionic mechanisms and potentially clarify arrhythmogenic behaviors...
September 2017: Chaos
https://www.readbyqxmd.com/read/28964113/memory-effects-transient-growth-and-wave-breakup-in-a-model-of-paced-atrium
#16
Alejandro Garzón, Roman O Grigoriev
The mechanisms underlying cardiac fibrillation have been investigated for over a century, but we are still finding surprising results that change our view of this phenomenon. The present study focuses on the transition from normal rhythm to spiral wave chaos associated with a gradual increase in the pacing rate. While some of our findings are consistent with existing experimental, numerical, and theoretical studies of this problem, one result appears to contradict the accepted picture. Specifically we show that, in a two-dimensional model of paced homogeneous atrial tissue, transition from discordant alternans to conduction block, wave breakup, reentry, and spiral wave chaos is associated with the transient growth of finite amplitude disturbances rather than a conventional instability...
September 2017: Chaos
https://www.readbyqxmd.com/read/28962867/ginsenoside-re-prevents-angiotensin-ii-induced-gap-junction-remodeling-by-activation-of-ppar%C3%AE-in-isolated-beating-rat-atria
#17
Bo Zhang, Xun Cui, Hong-Hua Jin, Lan Hong, Xia Liu, Xiang Li, Qing-Gao Zhang, Li-Ping Liu
AIMS: Ginsenoside Re (G-Re), a major ginsenoside in ginseng, has many beneficial pharmacological effects on negative cardiac contractility, electromechanical alternans, antiarrhythmia, angiogenic regeneration and cardiac electrophysiological function. However, effects of G-Re on gap-junction remodeling are unclear. Therefore, this study aimed to investigate the effect of G-Re on angiotensin II (Ang II)-induced downregulation of connexin-40 (CX40) and -43 (CX43) in beating rat left atria...
December 1, 2017: Life Sciences
https://www.readbyqxmd.com/read/28916174/evaluation-of-beat-to-beat-ventricular-repolarization-lability-from-standard-12-lead-ecg-during-acute-myocardial-ischemia
#18
Salah S Al-Zaiti, Mohammad Alrawashdeh, Christian Martin-Gill, Clifton Callaway, David Mortara, Jan Nemec
BACKGROUND: Acute myocardial ischemia is a common cause of ventricular arrhythmias, yet recent ECG methods predicting susceptibility to ventricular tachyarrhythmia have not been fully evaluated during spontaneous ischemia. We sought to evaluate the clinical utility of alternans and non-alternans components of repolarization variability from the standard 10-second 12-lead ECG signals to risk stratify patients with acute chest pain. METHODS: We enrolled consecutive, non-traumatic, chest pain patients transported through Emergency Medical Services (EMS) to three tertiary care hospitals with cardiac catheterization lab capabilities in Pittsburgh, PA...
August 10, 2017: Journal of Electrocardiology
https://www.readbyqxmd.com/read/28903013/spatiotemporally-non-uniform-ca-2-dynamics-of-cardiac-purkinje-fibers-in-mouse-myocardial-infarct
#19
Taka-Aki Matsuyama, Hideo Tanaka, Hatsue Ishibashi-Ueda, Tetsuro Takamatsu
Surviving Purkinje fibers in myocardial infarct are regarded as an important substrate in arrhythmogenesis. However, poorly understood are functional properties of Purkinje fibers in the infarcted heart. We sought to visualize intracellular Ca(2+) ([Ca(2+)]i) dynamics of Purkinje fiber networks in the mouse myocardial infarct. Using 3- to 4-day-old or 7- to 9-day-old infarcted hearts after the left coronary-artery ligation corresponding, respectively, to acute or healing phase, we conducted rapid fluo4-fluorescence imaging on the endocardial surface of the left ventricular septum by macro-zoom fluorescence microscopy and rapid-scanning confocal microscopy...
November 2017: Journal of Histochemistry and Cytochemistry: Official Journal of the Histochemistry Society
https://www.readbyqxmd.com/read/28859079/a-computational-model-of-spatio-temporal-cardiac-intracellular-calcium-handling-with-realistic-structure-and-spatial-flux-distribution-from-sarcoplasmic-reticulum-and-t-tubule-reconstructions
#20
Michael A Colman, Christian Pinali, Andrew W Trafford, Henggui Zhang, Ashraf Kitmitto
Intracellular calcium cycling is a vital component of cardiac excitation-contraction coupling. The key structures responsible for controlling calcium dynamics are the cell membrane (comprising the surface sarcolemma and transverse-tubules), the intracellular calcium store (the sarcoplasmic reticulum), and the co-localisation of these two structures to form dyads within which calcium-induced-calcium-release occurs. The organisation of these structures tightly controls intracellular calcium dynamics. In this study, we present a computational model of intracellular calcium cycling in three-dimensions (3-D), which incorporates high resolution reconstructions of these key regulatory structures, attained through imaging of tissue taken from the sheep left ventricle using serial block face scanning electron microscopy...
August 2017: PLoS Computational Biology
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