scholarly journals Heterogeneous and anisotropic integrative model of pulmonary veins: computational study of arrhythmogenic substrate for atrial fibrillation

2013 ◽  
Vol 3 (2) ◽  
pp. 20120069 ◽  
Author(s):  
Oleg V. Aslanidi ◽  
Michael A. Colman ◽  
Marta Varela ◽  
Jichao Zhao ◽  
Bruce H. Smaill ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
High Frequency ◽  
Computational Study ◽  
Pulmonary Veins ◽  
Three Dimensional ◽  
Primary Source ◽  
Integrative Model ◽  
Micro Computed Tomography ◽  
Three Dimensional Model ◽  
Arrhythmogenic Substrate

Mechanisms underlying the genesis of re-entrant substrate for the most common cardiac arrhythmia, atrial fibrillation (AF), are not well understood. In this study, we develop a multi-scale three-dimensional computational model that integrates cellular electrophysiology of the left atrium (LA) and pulmonary veins (PVs) with the respective tissue geometry and fibre orientation. The latter is reconstructed in unique detail from high-resolution (approx. 70 μm) contrast micro-computed tomography data. The model is used to explore the mechanisms of re-entry initiation and sustenance in the PV region, regarded as the primary source of high-frequency electrical activity in AF. Simulations of the three-dimensional model demonstrate that an initial break-down of normal electrical excitation wave-fronts can be caused by the electrical heterogeneity between the PVs and LA. High tissue anisotropy is then responsible for the slow conduction and generation of a re-entrant circuit near the PVs. Evidence of such circuits has been seen clinically in AF patients. Our computational study suggests that primarily the combination of electrical heterogeneity and conduction anisotropy between the PVs and LA tissues leads to the generation of a high-frequency (approx. 10 Hz) re-entrant source near the PV sleeves, thus providing new insights into the arrhythmogenic mechanisms of excitation waves underlying AF.

scholarly journals A novel computational sheep atria model for the study of atrial fibrillation

2013 ◽  
Vol 3 (2) ◽  
pp. 20120067 ◽  
Author(s):  
Timothy D. Butters ◽  
Oleg V. Aslanidi ◽  
Jichao Zhao ◽  
Bruce Smaill ◽  
Henggui Zhang
Keyword(s):  
Atrial Fibrillation ◽  
Animal Models ◽  
Pulmonary Veins ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Cell Types ◽  
Underlying Mechanisms ◽  
Detailed Computer ◽  
Atrial Cell ◽  
Atrial Excitation

Sheep are often used as animal models for experimental studies into the underlying mechanisms of cardiac arrhythmias. Previous studies have shown that biophysically detailed computer models of the heart provide a powerful alternative to experimental animal models for underpinning such mechanisms. In this study, we have developed a family of mathematical models for the electrical action potentials of various sheep atrial cell types. The developed cell models were then incorporated into a three-dimensional anatomical model of the sheep atria, which was recently reconstructed and segmented based on anatomical features within different regions. This created a novel biophysically detailed computational model of the three-dimensional sheep atria. Using the model, we then investigated the mechanisms by which paroxysmal rapid focal activity in the pulmonary veins can transit to sustained atrial fibrillation. It was found that the anisotropic property of the atria arising from the fibre structure plays an important role in facilitating the development of fibrillatory atrial excitation waves, and the electrical heterogeneity plays an important role in its initiation.

scholarly journals Forecasting of Surface Currents via Correcting Wind Stress with Assimilation of High-Frequency Radar Data in a Three-Dimensional Model

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Lei Ren ◽  
Stephen Nash ◽  
Michael Hartnett
Keyword(s):  
Data Assimilation ◽  
High Frequency ◽  
Three Dimensional ◽  
Hf Radar ◽  
Surface Velocity ◽  
Shear Stresses ◽  
Surface Currents ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
The Impact

This paper details work in assessing the capability of a hydrodynamic model to forecast surface currents and in applying data assimilation techniques to improve model forecasts. A three-dimensional model Environment Fluid Dynamics Code (EFDC) was forced with tidal boundary data and onshore wind data, and so forth. Surface current data from a high-frequency (HF) radar system in Galway Bay were used for model intercomparisons and as a source for data assimilation. The impact of bottom roughness was also investigated. Having developed a “good” water circulation model the authors sought to improve its forecasting ability through correcting wind shear stress boundary conditions. The differences in surface velocity components between HF radar measurements and model output were calculated and used to correct surface shear stresses. Moreover, data assimilation cycle lengths were examined to extend the improvements of surface current’s patterns during forecasting period, especially for north-south velocity component. The influence of data assimilation in model forecasting was assessed using a Data Assimilation Skill Score (DASS). Positive magnitude of DASS indicated that both velocity components were considerably improved during forecasting period. Additionally, the improvements of RMSE for vector direction over domain were significant compared with the “free run.”

scholarly journals Thermal functioning of a tropical reservoir assessed through three-dimensional modelling and high-frequency monitoring

RBRH ◽  
2021 ◽  
Vol 26 ◽  
Author(s):  
Denis Furstenau Plec ◽  
Talita Fernanda das Graças Silva ◽  
Brigitte Vinçon-Leite ◽  
Nilo Nascimento
Keyword(s):  
Water Temperature ◽  
High Frequency ◽  
Three Dimensional ◽  
Frequency Measurement ◽  
Three Dimensional Model ◽  
Anthropogenic Pressures ◽  
Tropical Reservoir ◽  
River Temperature ◽  
Lake Morphology ◽  
The Impact

ABSTRACT Urban lakes and reservoirs provide important ecosystem services. However, their water quality is being affected by anthropogenic pressures. The thermal regime is a strong driver of the vertical transport of nutrients, phytoplankton and oxygen. Thermal stratification can modify biogeochemical processes. In this paper, a three-dimensional hydrodynamic model was implemented and validated with high-frequency measurement of water temperature. The simulation results were in agreement with the measurements. For all simulation period, the model performance was evaluated based on hourly values, presenting a maximum RMSE of 0.65 ºC and Relative Error of 2.08%. The results show that high-frequency measurement associated with a three-dimensional model could help to understand and identify the reasons for the changes in the thermal condition of a shallow urban lake. The impact of the stream inflow on the temperature was highlighted, showing that during higher discharge events, when the river temperature is colder than the lake water, it flows into the lake deeper layers. The inflow water sank to the deeper layers where the lake morphology changes. The model showed an impact along the entire lake, showing the importance of monitoring the inflow water temperature. This modelling tool could be further used to study specific patterns of reservoir hydrodynamics.

scholarly journals A Computational Study of the Electrophysiological Substrate in Patients Suffering From Atrial Fibrillation

2021 ◽  
Vol 12 ◽  
Author(s):  
S. Pagani ◽  
L. Dede' ◽  
A. Frontera ◽  
M. Salvador ◽  
L. R. Limite ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Cardiac Electrophysiology ◽  
Computational Study ◽  
Pulmonary Veins ◽  
Coupled System ◽  
Density Mapping ◽  
Slow Conduction ◽  
Conduction Velocities ◽  
Ectopic Beats

In the context of cardiac electrophysiology, we propose a novel computational approach to highlight and explain the long-debated mechanisms behind atrial fibrillation (AF) and to reliably numerically predict its induction and sustainment. A key role is played, in this respect, by a new way of setting a parametrization of electrophysiological mathematical models based on conduction velocities; these latter are estimated from high-density mapping data, which provide a detailed characterization of patients' electrophysiological substrate during sinus rhythm. We integrate numerically approximated conduction velocities into a mathematical model consisting of a coupled system of partial and ordinary differential equations, formed by the monodomain equation and the Courtemanche-Ramirez-Nattel model. Our new model parametrization is then adopted to predict the formation and self-sustainment of localized reentries characterizing atrial fibrillation, by numerically simulating the onset of ectopic beats from the pulmonary veins. We investigate the paroxysmal and the persistent form of AF starting from electro-anatomical maps of two patients. The model's response to stimulation shows how substrate characteristics play a key role in inducing and sustaining these arrhythmias. Localized reentries are less frequent and less stable in case of paroxysmal AF, while they tend to anchor themselves in areas affected by severe slow conduction in case of persistent AF.

Hemodynamic Changes in the Left Atrium due to Atrial Fibrillation

2011 ◽  
Author(s):  
Kenichi Funamoto ◽  
Ryo Koizumi ◽  
Toshiyuki Hayase ◽  
Muneichi Shibata ◽  
Tomoyuki Yambe
Keyword(s):  
Atrial Fibrillation ◽  
Left Atrium ◽  
High Frequency ◽  
Left Atrial ◽  
Left Atrial Appendage ◽  
Thrombus Formation ◽  
Pulmonary Veins ◽  
Hemodynamic Changes ◽  
Structure Interaction ◽  
Interaction Simulation

The left atrium (LA), which connects four pulmonary veins (PVs) to the left ventricle (LV), has a characteristic shape called the left atrial appendage (LAA) under the left PV. Atrial fibrillation (AF) is a heart disease, by which irregular electrical signals with high-frequency contraction (> 400 bpm) occur in the LA. Although AF itself is not fatal, it may cause thrombus formation, resulting to cerebral infarction. In this study, hemodynamics in the LA with/without AF was investigated by means of fluid-structure interaction simulation.

scholarly journals Body surface localization of left and right atrial high-frequency rotors in atrial fibrillation patients: A clinical-computational study

Heart Rhythm ◽  
2014 ◽  
Vol 11 (9) ◽  
pp. 1584-1591 ◽  
Author(s):  
Miguel Rodrigo ◽  
María S. Guillem ◽  
Andreu M. Climent ◽  
Jorge Pedrón-Torrecilla ◽  
Alejandro Liberos ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Body Surface ◽  
High Frequency ◽  
Computational Study ◽  
Right Atrial ◽  
Surface Localization ◽  
Left And Right

scholarly journals Coronary Sinus Ablation Is a Key Player Substrate in Recurrence of Persistent Atrial Fibrillation

Cardiology ◽  
2019 ◽  
Vol 143 (3-4) ◽  
pp. 107-113 ◽  
Author(s):  
Naseer Ahmed ◽  
Shahida Perveen ◽  
Adeela Mehmood ◽  
Gulab Fatima Rani ◽  
Giulio Molon
Keyword(s):  
Atrial Fibrillation ◽  
Pulmonary Vein ◽  
Coronary Sinus ◽  
Pulmonary Veins ◽  
Persistent Atrial Fibrillation ◽  
Arrhythmogenic Substrate ◽  
Electrophysiological Procedures ◽  
Very High ◽  
Insight Into

Atrial fibrillation (AF) is the most frequent atrial arrhythmia. During the last few decades, owing to numerous advancements in the field of electrophysiology, we reached satisfactory outcomes for paroxysmal AF with the help of ablation procedures. But the most challenging type is still persistent AF. The recurrence rate of AF in patients with persistent AF is very high, which shows the inadequacy of pulmonary vein isolation (PVI). Over the last few decades, we have been trying to gain insight into AF mechanisms, and have come to the conclusion that there must be some triggers and substrates other than pulmonary veins. According to many studies, PVI alone is not enough to deal with persistent AF. The purpose of our review is to summarize updates and to clarify the role of coronary sinus (CS) in AF induction and propagation. This review will provide updated knowledge on developmental, histological, and macroscopic anatomical aspects of CS with its role as arrhythmogenic substrate. This review will also inform readers about application of CS in other electrophysiological procedures.

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