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A transmurally heterogeneous model of the ventricular tissue and its application for simulation of Brugada Syndrome
Full text linkLow cardiac frequency associated with higher number of extrasistoles in a computational model of Brugada Syndrome
Full text linkIncremental Pacing Induces Sustained Reentry in a Computational Model of Brugada Syndrome
Full text linkA Computational Model of Brugada Syndrome in 3D Heterogeneous Cardiac Tissue
Full text linkBrugada syndrome is a genetic cardiac disorder associated with ventricular arrhythmias and sudden cardiac death. There are two classical interpretations of the ECG features and pathophysiological mechanism of the BrS: the repolarization disorder theory and the depolarization disorder theory. We employed our previously published phenomenological model of human myocytes to simulate the electrical activity of cardiac tissue in a 3D transmurally heterogeneous slab. Furthermore, we modified the model to reproduce the characteristics commonly associated to BrS action potentials. We assessed the insurgence of sustained reentry as a function of electrophysiological alterations and fibrosis distribution. Additionally, for each simulation, we computed simulated epicardial unipolar electrograms. Our results suggest that both electrophysiological and structural alterations are important factors in the induction of sustained reentry associated to BrS
Electrophysiological Closed Loop Model of the Heart as Supporting Tool for Cardiac Pacing
Full text linkIn this work, we developed a closed loop model of the interaction between the heart and a cardiac pacemaker. The main novelty of our framework is the employment of a reaction-diffusion heart model, which could enhance the assessment of cardiac pacing. Additionally, we provided a specific hardware setup for the deployment of our frame-work. Our results show that the heart model reproduces the healthy activation sequence and is feasible for closed loop simulations. Furthermore, we successfully simulated the interaction between heart and pacemaker models during the insurgence of endless loop tachycardia. Finally, we believe that our closed loop system could be an effective supporting tool to evaluate the safety and efficacy of the therapeutic effect of cardiac pacemakers
In Silico Closed-Loop System for the Assessment of Cardiac Pacing Algorithms
Full text linkIn this work, we report on the application of a closed-loop system, composed of a 2D reaction-diffusion heart model and a pace-maker model, for assessing pacemaker-heart interactions. To demonstrate the potential of our approach, we replicated a clinical case report in which a ventricular pacing-minimizing strategy promoted the onset of Pacemaker-Mediated Tachycardia (PMT). To replicate the clinical case, we simulated an atrioventricular (AV) block condition and set the same pacemaker programming reported in the clinical case study. Our study aims to show the usability and potential of our framework by exploring different pacemaker settings coupled with specific electro-physiological heart conditions, thus allowing the assessment of the safety and efficacy of a particular pacing algorithm. The results from our heart model highlighted that the refractoriness of the AV node, in addition to the pacemaker setting (e.g., AV delay and Post Ventricular Atrial Refractory period), plays a crucial role in the onset of PMTs in patients with pacemakers programmed with an AV delay hysteresis algorithm. We believe that our closed-loop system could represent a valuable auxiliary tool for a preliminary assessment and comparison of various pacing algorithms
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Electrophysiological patterns and structural substrates of Brugada syndrome: Critical appraisal and computational analyses
No full textBrugada syndrome (BrS) is a cardiac electrophysiological disease with unknown etiology, associated with sudden cardiac death. Symptomatic patients are treated with implanted cardiac defibrillator, but no risk stratification strategy is effective in patients that are at low to medium arrhythmic risk. Cardiac computational modeling is an emerging tool that can be used to verify the hypotheses of pathogenesis and inspire new risk stratification strategies. However, to obtain reliable results computational models must be validated with consistent experimental data. We reviewed the main electrophysiological and structural variables from BrS clinical studies to assess which data could be used to validate a computational approach. Activation delay in the epicardial right ventricular outflow tract is a consistent finding, as well as increased fibrosis and subclinical alterations of right ventricular functional and morphological parameters. The comparison between other electrophysiological variables is hindered by methodological differences between studies, which we commented. We conclude by presenting a recent theory unifying electrophysiological and structural substrate in BrS and illustrate how computational modeling could help translation to risk stratification
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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