scholarly journals Simulation of ectopic activity onset in border zones between normal and damaged myocardium with minimal ionic models

2020 ◽  
Author(s):  
Maxim Ryzhii ◽  
Elena Ryzhii
Keyword(s):  
Ectopic Activity ◽  
Border Zones ◽  
Activity Onset

scholarly journals Atrial Fibrillation and Fibrosis: Beyond the Cardiomyocyte Centric View

2015 ◽  
Vol 2015 ◽  
pp. 1-16 ◽  
Author(s):  
Michele Miragoli ◽  
Alexey V. Glukhov
Keyword(s):  
Atrial Fibrillation ◽  
Conduction Block ◽  
Resting Membrane Potential ◽  
Ectopic Activity ◽  
Impulse Conduction ◽  
Cardiac Impulse ◽  
Border Zones ◽  
Degree Of Coupling

Atrial fibrillation (AF) associated with fibrosis is characterized by the appearance of interstitial myofibroblasts. These cells are responsible for the uncontrolled deposition of the extracellular matrix, which pathologically separate cardiomyocyte bundles. The enhanced fibrosis is thought to contribute to arrhythmias “indirectly” because a collagenous septum is a passive substrate for propagation, resulting in impulse conduction block and/or zigzag conduction. However, the emerging results demonstrate that myofibroblastsin vitroalso promote arrhythmogenesis due to direct implications upon cardiomyocyte electrophysiology. This electrical interference may be considered beneficial as it resolves any conduction blocks; however, the passive properties of myofibroblasts might cause a delay in impulse propagation, thus promoting AF due to discontinuous slow conduction. Moreover, low-polarized myofibroblasts reduce, via cell-density dependence, the fast driving inward current for cardiac impulse conduction, therefore resulting in arrhythmogenic uniformly slow propagation. Critically, the subsequent reduction in cardiomyocytes resting membrane potentialin vitrosignificantly increases the likelihood of ectopic activity. Myofibroblast densities and the degree of coupling at cellular border zones also impact upon this likelihood. By considering futurein vivostudies, which identify myofibroblasts “per se” as a novel targets for cardiac arrhythmias, this review aims to describe the implications of noncardiomyocyte view in the context of AF.

Automated Border Control: Criminalizing the “Hidden Intent” of Migrant Embodiment

2019 ◽  
Vol 6 (2) ◽  
Author(s):  
Felicity Amaya Schaeffer
Keyword(s):  
Homeland Security ◽  
Racial Bias ◽  
Great Part ◽  
The Body ◽  
Industrial Complex ◽  
Border Control ◽  
Computer Engineering ◽  
Novel Technologies ◽  
Surveillance Technology ◽  
Border Zones

I argue that we are entering an automated era of border control that I label a border-biosecurity industrial complex. Funded in great part by the Department of Homeland Security (DHS), scientific research and automated surveillance technologies promise the state innovative and supposedly unbiased solutions to the challenge of border control and security. This article spotlights a border surveillance technology called AVATAR (Automated Virtual Agent for Truth Assessment in Real-Time). Analyzing this technology, which was funded by the DHS and developed by faculty at the University of Arizona’s National Center for Border Security and Immigration (BORDERS), allows me to assess how the emphasis on novel technologies to detect terrorists unleashes the search for ubiquitous surveillance devices programmed to detect deviant behavioral and physiological movements. I offer a wider view of this technology-in-the-making by analyzing how university research in aerial defense, the psychology of deception, the life sciences, and computer engineering influences the development of surveillance devices and techniques. I explore how, during a posthuman era, automated technologies detect and racialize “suspect life” under the guise of scientific neutrality and supposedly free from human interference. Suspect life refers to the racial bias preprogrammed into algorithms that compute danger or risk into certain human movements and regions such as border zones. As these technologies turn the body into matter, they present biological life as a more scientifically verifiable truth than human verbal testimony, moving border control from the adjudication of law through the subjective interview to the automated body that speaks a truth more powerful than a complex story can tell.

Abstract 272: Sex Differences in β-Adrenergic Responsiveness of Excitation-Contraction Coupling in Isolated Rabbit Hearts

2014 ◽  
Vol 115 (suppl_1) ◽  
Author(s):  
Gregory Hoeker ◽  
Ashleigh Hood ◽  
Rodolphe Katra ◽  
Steven Poelzing ◽  
Steven Pogwizd
Keyword(s):  
Sex Differences ◽  
Action Potentials ◽  
Adrenergic Receptor ◽  
Calcium Release ◽  
Dependent Manner ◽  
Ectopic Activity ◽  
Dose Threshold ◽  
Ectopic Beats ◽  
Cardioprotective Effects ◽  
Dose Dependent

Introduction: Sex differences in β-adrenergic receptor (β-AR) responsiveness are associated with female cardioprotection. We hypothesize that female (F) rabbits have reduced responsiveness to β-AR stimulation vs males (M), and that the degree and type of sex differences vary with the β-AR subtypes that are activated. Methods: Ventricular action potentials (AP) and intracellular calcium transients (CaT) were optically mapped from the epicardial surface of rabbit hearts during 3 Hz pacing. Spontaneous calcium release (SCR) and ectopic activity were elicited at 1, 3, and 5.5 Hz. β-responsiveness was assessed with the nonselective β-agonist isoproterenol (Iso, 1-316 nM), or β2-AR selective agonist zinterol (Zin, 10 nM). Results: At baseline, the time constant of CaT decay (τ) was faster in F than M (54.0±1.7 vs 62.1±3.0 ms; n=14, 14; p < 0.05), with no sex difference in CaT duration (CaD80). AP duration (APD90) was shorter in F than M (202.5±5.0 vs 218.2±5.7 ms; p < 0.05). Iso decreased τ, CaD80, and APD90 in a dose-dependent manner in both sexes (n = 5, 5 for F, M). Iso decreased τ to a lesser extent in F than M for 1 and 32-316 nM Iso (F = 11-32 ms, M = 23-48 ms; p < 0.05). The Iso-induced decrease in CaD80 was not significantly different in F than M at any dose. The Iso-induced decrease in APD90 was significantly less in F than M only at 316 nM Iso (75.5±8.7 ms vs 103.9±6.2 ms, p < 0.05). In contrast, there were no sex differences in the response to Zin for τ, CaD80, or APD90 (n = 6, 6 for F, M). Zin decreased τ by 7.2±2.0 ms in F vs 12.7±3.7 ms in M; CaD80 by 18.0±5.3% in F vs 21.1±8.0 ms in M; and APD90 by 24.9±8.5 ms in F vs 21.9±8.9 ms in M. SCR was observed in 50% (6/12) of hearts treated with Zin, whereas Iso elicited SCR in all hearts (10/10) with a dose threshold of 32 nM. No ectopic beats were observed with Zin (0/36 trials in 12 hearts). With Iso, ectopic activity was less frequent in F hearts (16%, 12/75 trials in 5 hearts) than in M hearts (41%, 26/68 trials in 5 hearts, p < 0.05). Conclusions: These results suggest that sex differences in AP and CaT depend on the dose of the agonist used and the β-AR subtypes that are activated. Elucidating nuances of sex differences in β-AR subtype physiology will provide a better understanding of the mechanisms of reduced β-responsiveness in F and its cardioprotective effects.

scholarly journals Stroke in a Young Man Secondary to Paroxysmal Atrial Fibrillation and Thyrotoxicosis: A Case Report

2017 ◽  
Vol 9 (3) ◽  
pp. 228-233
Author(s):  
Rodrigo Bazan ◽  
Thiago Dias Fernandes ◽  
Gláucia Maria Ferreira da Silva Mazeto ◽  
Mariângela Esther Alencar Marques ◽  
Gabriel Pereira Braga ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Causal Link ◽  
Graves Disease ◽  
Pathological Findings ◽  
Thyroid Scintigraphy ◽  
Normal Heart ◽  
Ectopic Activity ◽  
Resonance Imaging ◽  
Significant Clinical Improvement

We report a case of a male patient with stroke caused by atrial fibrillation (AF) due to thyrotoxicosis. At hospital admission, he presented hypertension and AF. Magnetic resonance imaging confirmed a right-side ischemic area. The thyrotoxicosis was confirmed by thyroid function and thyroid scintigraphy that showed goiter with diffuse hypercaptation. The patient was treated with tapazole and total thyroidectomy, and pathological findings suggested Graves’ disease. Hyperthyroidism is associated with increased supraventricular ectopic activity in patients with a normal heart, and may be an important causal link between hyperthyroidism and AF. The patient experienced significant clinical improvement, but presented long-term neuropsychiatric disorders.

scholarly journals Prognosis in severe heart failure: Relation to hemodynamic measurements and ventricular ectopic activity

1983 ◽  
Vol 2 (3) ◽  
pp. 403-410 ◽  
Author(s):  
John R. Wilson ◽  
J. Sanford Schwartz ◽  
Martin St. John Sutton ◽  
Nancy Ferraro ◽  
Leonard N. Horowitz ◽  
...  
Keyword(s):  
Heart Failure ◽  
Severe Heart Failure ◽  
Ectopic Activity ◽  
Ventricular Ectopic Activity ◽  
Hemodynamic Measurements

Radiofrequency Catheter Ablation of Frequent Monomorphic Ventricular Ectopic Activity

1999 ◽  
Vol 10 (7) ◽  
pp. 924-934 ◽  
Author(s):  
KARLHEINZ SEIDL ◽  
BURGHARD SCHUMACHER ◽  
BERND HAUER ◽  
WERNER JUNG ◽  
AXEL DRÖGEMÜLLER ◽  
...  
Keyword(s):  
Catheter Ablation ◽  
Radiofrequency Catheter Ablation ◽  
Ectopic Activity ◽  
Ventricular Ectopic Activity
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