keyword
MENU ▼
Read by QxMD icon Read
search

APD alternans

keyword
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
#1
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/29073179/restitution-characteristics-of-his-bundle-and-working-myocardium-in-isolated-rabbit-hearts
#2
Shangwei Huang, Liqun Wu, Jian Huang, Nuttanont Panitchob, Nan Hu, Ravi Ranjan, Derek J Dosdall
The Purkinje system (PS) and the His bundle have been recently implicated as an important driver of the rapid activation rate after 1-2 minutes of ventricular fibrillation (VF). It is unknown whether activations during VF propagate through the His-Purkinje system to other portions of the the working myocardium (WM). Little is known about restitution characteristic differences between the His bundle and working myocardium at short cycle lengths. In this study, rabbit hearts (n = 9) were isolated, Langendorff-perfused, and electromechanically uncoupled with blebbistatin (10 μM)...
2017: PloS One
https://www.readbyqxmd.com/read/28989116/complex-restitution-behavior-and-reentry-in-a-cardiac-tissue-model-for-neonatal-mice
#3
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/28964159/distinguishing-mechanisms-for-alternans-in-cardiac-cells-using-constant-diastolic-interval-pacing
#4
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/28964144/constant-di-pacing-suppresses-cardiac-alternans-formation-in-numerical-cable-models
#5
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
#6
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
#7
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/28894423/%C3%AE-adrenergic-inhibition-prevents-action-potential-and-calcium-handling-changes-during-regional-myocardial-ischemia
#8
Shannon R Murphy, Lianguo Wang, Zhen Wang, Philip Domondon, Di Lang, Beth A Habecker, Rachel C Myles, Crystal M Ripplinger
β-adrenergic receptor (β-AR) blockers may be administered during acute myocardial infarction (MI), as they reduce energy demand through negative chronotropic and inotropic effects and prevent ischemia-induced arrhythmogenesis. However, the direct effects of β-AR blockers on ventricular electrophysiology and intracellular Ca(2+) handling during ischemia remain unknown. Using optical mapping of transmembrane potential (with RH237) and sarcoplasmic reticulum (SR) Ca(2+) (with the low-affinity indicator Fluo-5N AM), the effects of 15 min of regional ischemia were assessed in isolated rabbit hearts (n = 19)...
2017: Frontiers in Physiology
https://www.readbyqxmd.com/read/28842915/roles-of-impaired-intracellular-calcium-cycling-in-arrhythmogenicity-of-diabetic-mouse-model
#9
Chung-Chuan Chou, Chien-Te Ho, Hui-Ling Lee, Yen Chu, Tzung-Hai Yen, Ming-Shien Wen, Shien-Fong Lin, Cheng-Hung Lee, Po-Cheng Chang
BACKGROUND: Diabetes mellitus is associated an increased risk of ventricular arrhythmias (VAs), but the underlying electrophysiological mechanisms are not fully explored. This study was aimed to test whether dynamic factors and Cai handling play roles in arrhythmogenesis of a diabetic animal model. METHODS: We used 26 db/db type 2 diabetes mice and 28 control mice in this study. VA inducibility was evaluated in vivo under isoflurane general anesthesia. The intracellular Ca(2+) (Cai ) and membrane voltage (Vm ) signals of the Langendorff-perfused mouse hearts were simultaneously recorded using the optical mapping technique...
August 26, 2017: Pacing and Clinical Electrophysiology: PACE
https://www.readbyqxmd.com/read/28821956/effects-of-ageing-on-pro-arrhythmic-ventricular-phenotypes-in-incrementally-paced-murine-pgc-1%C3%AE-hearts
#10
Shiraz Ahmad, Haseeb Valli, Charlotte E Edling, Andrew A Grace, Kamalan Jeevaratnam, Christopher L-H Huang
A range of chronic clinical conditions accompany cardiomyocyte energetic dysfunction and constitute independent risk factors for cardiac arrhythmia. We investigated pro-arrhythmic and arrhythmic phenotypes in energetically deficient C57BL mice with genetic ablation of the mitochondrial promoter peroxisome proliferator-activated receptor-γ coactivator-1β (Pgc-1β), a known model of ventricular arrhythmia. Pro-arrhythmic and cellular action potential (AP) characteristics were compared in intact Langendorff-perfused hearts from young (12-16 week) and aged (> 52 week), wild-type (WT) and Pgc-1β (-/-) mice...
August 18, 2017: Pflügers Archiv: European Journal of Physiology
https://www.readbyqxmd.com/read/28662005/camkii-activation-promotes-cardiac-electrical-remodeling-and-increases-the-susceptibility-to-arrhythmia-induction-in-high-fat-diet-fed-mice-with-hyperlipidemia-conditions
#11
Peng Zhong, Dajun Quan, Yan Huang, He Huang
BACKGROUND: Obesity/hyperlipidemia is closely related to both atrial and ventricular arrhythmias. CaMKII, a multifunctional serine/threonine kinase, has been involved in cardiac arrhythmias of different etiologies. However, its role in obesity/hyperlipidemia-related cardiac arrhythmia is unexplored. The aim of this was to determine the involvement of CaMKII in the process. METHODS: Adult male APOE mice were fed a high-fat diet (HFD), administrated with KN93 (10 mg·kg·2d), a specific inhibitor of CaMKII...
October 2017: Journal of Cardiovascular Pharmacology
https://www.readbyqxmd.com/read/28290788/-the-myocardial-sleeves-of-the-pulmonary-veins-potential-implications-for-atrial-fibrillation
#12
Y V Egorov, L V Rozenshtrauh
Pulmonary veins (PVs) are thought to play an important role in the initiation of atrial fibrillation. However, systematic microelectrode studies from different regions of the left atria and PV myocardium remain limited. METHODS AND RESULTS: A 2-microelectrode technique was used to characterize electrophysiological properties of rat left atrial and PV myocardium, at baseline and during electrical stimulation. PV myocardium was characterized by prolonged action potential duration (APD) (74+/-2 ms in the PV mouth vs...
February 2017: Kardiologiia
https://www.readbyqxmd.com/read/28268303/effects-and-underlying-mechanisms-of-refractory-period-pacing-on-repolarization-dynamics-in-the-human-heart
#13
Diogo Santos, Michele Orini, Xin Zhou, Alfonso Bueno-Orovio, Ben Hanson, Peter Taggart, Martin Hayward, Blanca Rodriguez, Pier Lambiase
Repolarization alternans is related to the initiation of life threatening cardiac arrhythmias. Experimental and computational studies suggest that the abolishment of alternans using dynamic pacing protocols may prevent abnormal heart rhythms. In a recent animal study, refractory period pacing (RPP) on every other beat has shown promising results in alternans reduction. However, the cellular mechanisms underlying this therapy and its efficiency in human patients remain unclear. In this study, in vivo unipolar electrograms acquired during RPP from 240 epicardial sites from one patient were analysed...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28226462/effects-and-underlying-mechanisms-of-refractory-period-pacing-on-repolarization-dynamics-in-the-human-heart
#14
Diogo Santos, Michele Orini, Xin Zhou, Alfonso Bueno-Orovio, Ben Hanson, Peter Taggart, Martin Hayward, Blanca Rodriguez, Pier Lambiase, Diogo Santos, Michele Orini, Xin Zhou, Alfonso Bueno-Orovio, Ben Hanson, Peter Taggart, Martin Hayward, Blanca Rodriguez, Pier Lambiase, Ben Hanson, Diogo Santos, Martin Hayward, Pier Lambiase, Alfonso Bueno-Orovio, Blanca Rodriguez, Michele Orini, Xin Zhou, Peter Taggart
Repolarization alternans is related to the initiation of life threatening cardiac arrhythmias. Experimental and computational studies suggest that the abolishment of alternans using dynamic pacing protocols may prevent abnormal heart rhythms. In a recent animal study, refractory period pacing (RPP) on every other beat has shown promising results in alternans reduction. However, the cellular mechanisms underlying this therapy and its efficiency in human patients remain unclear. In this study, in vivo unipolar electrograms acquired during RPP from 240 epicardial sites from one patient were analysed...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/27902841/dynamical-effects-of-calcium-sensitive-potassium-currents-on-voltage-and-calcium-alternans
#15
Matthew Kennedy, Donald M Bers, Nipavan Chiamvimonvat, Daisuke Sato
KEY POINTS: A mathematical model of a small conductance Ca(2)(+) -activated potassium (SK) channel was developed and incorporated into a physiologically detailed ventricular myocyte model. Ca(2+) -sensitive K(+) currents promote negative intracellular Ca(2+) to membrane voltage (CAi(2+) → Vm ) coupling. Increase of Ca(2+) -sensitive K(+) currents can be responsible for electromechanically discordant alternans and quasiperiodic oscillations at the cellular level. At the tissue level, Turing-type instability can occur when Ca(2+) -sensitive K(+) currents are increased...
April 1, 2017: Journal of Physiology
https://www.readbyqxmd.com/read/27582498/suppression-of-ryanodine-receptor-function-prolongs-ca2-release-refractoriness-and-promotes-cardiac-alternans-in-intact-hearts
#16
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 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 We found that RyR2-SOF hearts displayed prolonged sarcoplasmic reticulum Ca(2+) release refractoriness and enhanced propensity for Ca(2+) alternans...
November 1, 2016: Biochemical Journal
https://www.readbyqxmd.com/read/27385917/impaired-sarcoplasmic-reticulum-calcium-uptake-and-release-promote-electromechanically-and-spatially-discordant-alternans-a-computational-study
#17
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
https://www.readbyqxmd.com/read/27384223/global-alternans-instability-and-its-effect-on-non-linear-wave-propagation-dynamical-wenckebach-block-and-self-terminating-spiral-waves
#18
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
https://www.readbyqxmd.com/read/27383322/effects-of-local-radiofrequency-denervation-on-ventricular-electrophysiological-properties-in-normal-and-acute-myocardial-ischemia-heart
#19
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
https://www.readbyqxmd.com/read/27336310/electrophysiology-of-heart-failure-using-a-rabbit-model-from-the-failing-myocyte-to-ventricular-fibrillation
#20
Aditya V S Ponnaluri, Luigi E Perotti, Michael Liu, Zhilin Qu, James N Weiss, Daniel B Ennis, William S Klug, Alan Garfinkel
Heart failure is a leading cause of death, yet its underlying electrophysiological (EP) mechanisms are not well understood. In this study, we use a multiscale approach to analyze a model of heart failure and connect its results to features of the electrocardiogram (ECG). The heart failure model is derived by modifying a previously validated electrophysiology model for a healthy rabbit heart. Specifically, in accordance with the heart failure literature, we modified the cell EP by changing both membrane currents and calcium handling...
June 2016: PLoS Computational Biology
keyword
keyword
45073
1
2
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"