Small size ionic heterogeneities in the human heart can attract rotors

2014 ◽  
Vol 307 (10) ◽  
pp. H1456-H1468 ◽  
Author(s):  
Arne Defauw ◽  
Nele Vandersickel ◽  
Peter Dawyndt ◽  
Alexander V. Panfilov
Keyword(s):  
Cardiac Arrhythmias ◽  
In Silico ◽  
Human Heart ◽  
Cardiac Tissue ◽  
Two Dimensional ◽  
Anatomical Model ◽  
Practical Applications ◽  
Ventricular Cells ◽  
Local Properties ◽  
Substantial Distance

Rotors occurring in the heart underlie the mechanisms of cardiac arrhythmias. Answering the question whether or not the location of rotors is related to local properties of cardiac tissue has important practical applications. This is because ablation of rotors has been shown to be an effective way to fight cardiac arrhythmias. In this study, we investigate, in silico, the dynamics of rotors in two-dimensional and in an anatomical model of human ventricles using a Ten Tusscher-Noble-Noble-Panfilov (TNNP) model for ventricular cells. We study the effect of small size ionic heterogeneities, similar to those measured experimentally. It is shown that such heterogeneities cannot only anchor, but can also attract, rotors rotating at a substantial distance from the heterogeneity. This attraction distance depends on the extent of the heterogeneities and can be as large as 5–6 cm in realistic conditions. We conclude that small size ionic heterogeneities can be preferred localization points for rotors and discuss their possible mechanism and value for applications.

scholarly journals Drift of Scroll Wave Filaments in an Anisotropic Model of the Left Ventricle of the Human Heart

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Sergei Pravdin ◽  
Hans Dierckx ◽  
Vladimir S. Markhasin ◽  
Alexander V. Panfilov
Keyword(s):  
Left Ventricle ◽  
Cardiac Arrhythmias ◽  
Human Heart ◽  
Cardiac Tissue ◽  
Three Dimensional ◽  
Excitable Media ◽  
Filament Dynamics ◽  
Myocardial Wall ◽  
Scroll Wave ◽  
Generic Description

Scroll waves are three-dimensional vortices which occur in excitable media. Their formation in the heart results in the onset of cardiac arrhythmias, and the dynamics of their filaments determine the arrhythmia type. Most studies of filament dynamics were performed in domains with simple geometries and generic description of the anisotropy of cardiac tissue. Recently, we developed an analytical model of fibre structure and anatomy of the left ventricle (LV) of the human heart. Here, we perform a systematic study of the dynamics of scroll wave filaments for the cases of positive and negative tension in this anatomical model. We study the various possible shapes of LV and different degree of anisotropy of cardiac tissue. We show that, for positive filament tension, the final position of scroll wave filament is mainly determined by the thickness of the myocardial wall but, however, anisotropy attracts the filament to the LV apex. For negative filament tension, the filament buckles, and for most cases, tends to the apex of the heart with no or slight dependency on the thickness of the LV. We discuss the mechanisms of the observed phenomena and their implications for cardiac arrhythmias.

scholarly journals Period of Arrhythmia Anchored around an Infarction Scar in an Anatomical Model of the Human Ventricles

Mathematics ◽  
2021 ◽  
Vol 9 (22) ◽  
pp. 2911
Author(s):  
Daria Mangileva ◽  
Pavel Konovalov ◽  
Arsenii Dokuchaev ◽  
Olga Solovyova ◽  
Alexander V. Panfilov
Keyword(s):  
Cardiac Tissue ◽  
Rotation Period ◽  
In Silico Analysis ◽  
Generic Model ◽  
Gray Zone ◽  
Ionic Model ◽  
Anatomical Model ◽  
Ventricular Cells ◽  
Realistic Description ◽  
The Waves

Rotating nonlinear waves of excitation in the heart cause dangerous cardiac arrhythmias. Frequently, ventricular arrhythmias occur as a result of myocardial infarction and are associated with rotation of the waves around a post-infarction scar. In this paper, we perform a detailed in silico analysis of scroll waves in an anatomical model of the human ventricles with a generic model of the infarction scar surrounded by the gray zone with modified properties of the myocardial tissue. Our model includes a realistic description of the heart shape, anisotropy of cardiac tissue and a detailed description of the electrical activity in human ventricular cells by a TP06 ionic model. We vary the size of the scar and gray zone and analyze the dependence of the rotation period on the injury dimensions. Two main regimes of wave scrolling are observed: the scar rotation, when the wave rotates around the scar, and the gray zone rotation, when the wave rotates around the boundary of the gray zone and normal tissue. The transition from the gray zone to the scar rotation occurs for the width of gray zone above 10–20 mm, depending on the perimeter of the scar. We compare our results with simulations in 2D and show that 3D anisotropy reduces the period of rotation. We finally use a model with a realistic shape of the scar and show that our approach predicts correctly the period of the arrhythmia.

Entrainment and Annihilation of Reentrant Excitation in a Periodically Stimulated Ring of Excitable Media

1997 ◽  
Vol 36 (04/05) ◽  
pp. 290-293
Author(s):  
L. Glass ◽  
T. Nomura
Keyword(s):  
Cardiac Arrhythmias ◽  
Initial Phase ◽  
Human Heart ◽  
Periodic Wave ◽  
Excitable Media ◽  
One Dimensional ◽  
Clinical Observations ◽  
Periodic Stimulation ◽  
Reentrant Excitation ◽  
Stimulation Of

Abstract:Excitable media, such as nerve, heart and the Belousov-Zhabo- tinsky reaction, exhibit a large excursion from equilibrium in response to a small but finite perturbation. Assuming a one-dimensional ring geometry of sufficient length, excitable media support a periodic wave of circulation. As in the periodic stimulation of oscillations in ordinary differential equations, the effects of periodic stimuli of the periodically circulating wave can be described by a one-dimensional Poincaré map. Depending on the period and intensity of the stimulus as well as its initial phase, either entrainment or termination of the original circulating wave is observed. These phenomena are directly related to clinical observations concerning periodic stimulation of a class of cardiac arrhythmias caused by reentrant wave propagation in the human heart.

Two-dimensional metal carbides and nitrides (MXenes): preparation, property, and applications in cancer therapy

Nanophotonics ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 2125-2145 ◽  
Author(s):  
Lu Ming Dong ◽  
Cui Ye ◽  
Lin Lin Zheng ◽  
Zhong Feng Gao ◽  
Fan Xia
Keyword(s):  
Cancer Therapy ◽  
Scientific Community ◽  
Critical Role ◽  
High Specific Surface Area ◽  
Future Perspective ◽  
Two Dimensional ◽  
Metal Carbides ◽  
Practical Applications ◽  
Two Dimensional Materials ◽  
Size And Morphology

AbstractTransition metal carbides and nitrides (MXenes), which comprise a rapidly growing family of two-dimensional materials, have attracted extensive attention of the scientific community, owing to its unique characteristics of high specific surface area, remarkable biocompatibility, and versatile applications. Exploring different methods to tune the size and morphology of MXenes plays a critical role in their practical applications. In recent years, MXenes have been demonstrated as promising nanomaterials for cancer therapy with substantial performances, which not only are helpful to clarify the mechanism between properties and morphologies but also bridge the gap between MXene nanotechnology and forward-looking applications. In this review, recent progress on the preparation and properties of MXenes are summarized. Further applications in cancer therapy are also discussed. Finally, the current opportunities and future perspective of MXenes are described.

A New Troughlike Nonimaging Solar Concentrator

2001 ◽  
Vol 124 (1) ◽  
pp. 51-54 ◽  
Author(s):  
Eduardo A. Rinco´n ◽  
Fidel A. Osorio
Keyword(s):  
Concentration Ratio ◽  
Glass Tube ◽  
Two Dimensional ◽  
Solar Concentrator ◽  
Steam Generation ◽  
Acceptance Angle ◽  
Practical Applications ◽  
Optimal Shapes ◽  
Heating Steam ◽  
East West

A new two-dimensional concentrator for solar energy collection has been developed. The concentrator has the following advantages, when compared with the classic Compound Parabolic Concentrators invented by Roland Winston, W. T. Welford, A. Rabl, Baranov, and other researchers: 1) It allows the use of parabolic mirrors, which have a reflecting area much smaller for a given concentration ratio and acceptance angle. 2) Between the mirror and the absorber, there is a large gap so that conduction losses are reduced. Convection losses can be reduced, too, if the absorber is enclosed within a glass tube. 3) It can be easily manufactured. Instead of seeking the shape of the mirrors for a given shape of the absorber, we have made the inverse statement of the problem, and we have obtained the optimal shapes of the absorbers with a prescribed acceptance angle, for parabolic mirrors, assuming that the intercept factor is unity, the mirrors are perfect, and the absorber surfaces are convex. The concentrator should be east-west oriented, and could be seasonal or monthly tilt adjusted. This concentrator could have many practical applications, such as fluid heating, steam generation, etc.

scholarly journals CFD Analysis of Urban Canopy Flows Employing the V2F Model: Impact of Different Aspect Ratios and Relative Heights

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Fabio Nardecchia ◽  
Annalisa Di Bernardino ◽  
Francesca Pagliaro ◽  
Paolo Monti ◽  
Giovanni Leuzzi ◽  
...  
Keyword(s):  
Flow Field ◽  
Water Channel ◽  
Flow Regimes ◽  
Two Dimensional ◽  
Mean Flow ◽  
Ansys Fluent ◽  
Practical Applications ◽  
Aspect Ratios ◽  
Starting Point ◽  
Step Down

Computational fluid dynamics (CFD) is currently used in the environmental field to simulate flow and dispersion of pollutants around buildings. However, the closure assumptions of the turbulence usually employed in CFD codes are not always physically based and adequate for all the flow regimes relating to practical applications. The starting point of this work is the performance assessment of the V2F (i.e., v2¯ − f) model implemented in Ansys Fluent for simulating the flow field in an idealized array of two-dimensional canyons. The V2F model has been used in the past to predict low-speed and wall-bounded flows, but it has never been used to simulate airflows in urban street canyons. The numerical results are validated against experimental data collected in the water channel and compared with other turbulence models incorporated in Ansys Fluent (i.e., variations of both k-ε and k-ω models and the Reynolds stress model). The results show that the V2F model provides the best prediction of the flow field for two flow regimes commonly found in urban canopies. The V2F model is also employed to quantify the air-exchange rate (ACH) for a series of two-dimensional building arrangements, such as step-up and step-down configurations, having different aspect ratios and relative heights of the buildings. The results show a clear dependence of the ACH on the latter two parameters and highlight the role played by the turbulence in the exchange of air mass, particularly important for the step-down configurations, when the ventilation associated with the mean flow is generally poor.

Abstract 469: Targeting Beta Adrenergic Receptor Resensitization Aids in Preservation of Receptor Function

2017 ◽  
Vol 121 (suppl_1) ◽  
Author(s):  
Elizabeth E Martellli ◽  
Yu Sun ◽  
John George ◽  
Maradumane L Mohan ◽  
Randall Starling ◽  
...  
Keyword(s):  
Heart Failure ◽  
Small Molecule ◽  
In Silico ◽  
Adrenergic Receptor ◽  
Human Heart ◽  
Receptor Function ◽  
Human Heart Failure ◽  
Pp2a Activity ◽  
Pi3k Activity ◽  
Underlying Mechanisms

Beta adrenergic receptor (βAR) down-regulation and desensitization are hallmarks of heart failure. Traditionally, it has been considered that increased desensitization mechanisms underlie βAR dysfunction in heart failure but it is not known whether resensitization of βARs is altered and is an integral contributor to heart failure. We have previously shown that resensitization is regulated by inhibition of PP2A by I2PP2A via PI3Kγ (Vasudevan et. al., 2011), the underlying mechanisms of I2PP2A binding to PP2A are not well understood. We used PyMOL software to find the binding interaction between PP2A and I2PP2A. Based on in silico predictions, we generated a mutant PP2A that when expressed would compete out I2PP2A and inhibit I2PP2A from binding to endogenous PP2A. Expression of PP2A mutant in β2AR expressing cells showed preservation of β2AR function following stimulation as measured by reduced β2AR phosphorylation, increased cAMP generation and increased phosphatase function. We also generated a small molecule from our in silico predictions that could target the interface of I2PP2A and PP2A binding to find that disruption of the PP2A/I2PP2A interaction underlies receptor function. We will use this small molecule to look at preservation of βAR function and amelioration of cardiac function. To test whether resensitization is altered in heart failure we used plasma membrane and endosomal fractions from non-failing and paired pre- and post-LVAD samples to show PI3K activity, PP2A activity, β2AR phosphorylation and adenylyl cyclase activity as a measure of recovery in βAR function. Our studies showed that endosomal fractions from human heart failure samples had elevated PI3K activity associated with reduced PP2A activity supporting the idea that βAR resensitization is inhibited in human heart failure samples. Since human heart failure samples have inhibited resensitization we tested the underlying mechanisms regulating βAR resensitization. Thus ongoing studies suggest that targeting the resensitization of βAR could provide beneficial cardiac remodeling in conditions of chronic mechanical overload and will be further discussed.

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