359 research outputs found

    Noninvasive Assessment of Spatio-Temporal Recurrence in Atrial Fibrillation

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    Propagation of Atrial Activity during atrial fibrillation (AF) is a complex phenomenon characterized by a certain degree of recurrence (periodic repetition). In this study, we investigated the possibility to detect recurrence noninvasively from body surface potential map recordings in patients affected by persistent AF, and localize this recurrence both in time and space. Results showed that clusters of recurrence can be identified from body surface recordings in these patients. Moreover, the number of clusters detected and their location on the top-right of the back of the torso were significantly associated with AF recurrence 4 to 6 weeks after electrical cardioversion. This suggests that noninvasive quantification of recurrence in persistent AF patients is possible, and may contribute to improve patient stratification

    The U.S. Law of Client Confidentiality: Framework for an International Perspective

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    In this Article, I will consider two general areas of the U.S. law of confidentiality. In Part I, I will reflect briefly upon what I call “the U.S. culture of lawyer-client confidentiality.” I say “culture” rather than “cult,” and one must guard against temptations to confuse those concepts. Those reflections will serve as background—by way of both match and contrast—to my sketch of the U.S. law of confidentiality in Part II

    Loss of Side-to-Side Connections Affects the Relative Contributions of the Sodium and Calcium Current to Transverse Propagation Between Strands of Atrial Myocytes

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    Background: Atrial fibrillation (AF) leads to a loss of transverse connections between myocyte strands that is associated with an increased complexity and stability of AF. We have explored the interaction between longitudinal and transverse coupling, and the relative contribution of the sodium (INa) and calcium (ICa) current to propagation, both in healthy tissue and under diseased conditions using computer simulations.Methods: Two parallel strands of atrial myocytes were modeled (Courtemanche et al. ionic model). As a control condition, every single cell was connected both transversely and longitudinally. To simulate a loss of transverse connectivity, this number was reduced to 1 in 4, 8, 12, or 16 transversely. To study the interaction with longitudinal coupling, anisotropy ratios of 3, 9, 16, and 25:1 were used. All simulations were repeated for varying degrees of INa and ICa block and the transverse activation delay (TAD) between the paced and non-paced strands was calculated for all cases.Results: The TAD was highly sensitive to the transverse connectivity, increasing from 1 ms at 1 in 1, to 25 ms at 1 in 4, and 100 ms at 1 in 12 connectivity. The TAD also increased when longitudinal coupling was increased. Both decreasing transverse connectivity and increasing longitudinal coupling enhanced the synchronicity of activation of the non-paced strand and increased the propensity for transverse conduction block. Even after long TADs, the action potential upstroke in the non-paced strand was still mainly dependent on the INa. Nevertheless, ICa in the paced strand was essential to provide depolarizing current to the non-paced strand. Loss of transverse connections increased the sensitivity to both INa and ICa block. However, when longitudinal coupling was relatively high, transverse propagation was more sensitive to ICa block than to INa block.Conclusions: Although transverse propagation depends on both INa and ICa, their relative contribution, and sensitivity to channel blockade, depends on the distribution of transverse connections and the axial conductivity. This simple two-strand model helps to explain the nature of atrial discontinuous conduction during structural remodeling and provides an opportunity for more effective drug development

    Time course and mechanisms of endo-epicardial electrical dissociation during atrial fibrillation in the goat

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    Aims This study aims to determine the degree and mechanisms of endo-epicardial dissociation of electrical activity during atrial fibrillation (AF) and endo-epicardial differences in atrial electrophysiology at different stages of atrial remodelling. Methods and results Simultaneous high-density endo-epicardial mapping of AF was performed on left atrial free walls of goats with acute AF, after 3 weeks, and after 6 months of AF (all n = 7). Endo-epicardial activation time differences and differences in the direction of conduction vectors were calculated, endocardial and epicardial effective refractory periods (ERP) were determined, and fractionation of electrograms was quantified. Histograms of endo-epicardial activation time differences and differences in the direction of conduction vectors revealed two distinct populations, i.e. dissociated and non-dissociated activity. Dyssynchronous activity (dissociated in time) increased from 17 ± 7% during acute AF to 39 ± 17% after 3 weeks, and 68 ± 13% after 6 months of AF. Dissociation was more pronounced in thicker parts of the atrial wall (thick: 49.3 ± 21.4%, thin: 42.2 ± 19.0%, P < 0.05). At baseline, endocardial ERPs were longer when compared with epicardial ERPs (ΔERP, 21.8 ± 18 ms; P < 0.001). This difference was absent after 6 months of AF. The percentage of fractionated electrograms during rapid pacing increased from 9.4 ± 1.9% (baseline) to 18.6 ± 0.6% (6 months). Conclusion During AF, pronounced dissociation of electrical activity occurs between the epicardial layer and the endocardial bundle network. The increase in dissociation is due to owing to progressive uncoupling between the epicardial layer and the endocardial bundles and correlates with increasing stability and complexity of the AF substrat

    Pharmacological inhibition of sodium-proton-exchanger subtype 3-mediated sodium absorption in the gut reduces atrial fibrillation susceptibility in obese spontaneously hypertensive rats

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    Background: Increased sodium uptake has been shown to contribute to hypertension and cardiac endorgan damage. The sodium-proton-exchanger subtype 3 (NHE3) is an important mediator of intestinal sodium absorption. Whether a reduction in intestinal sodium absorption can prevent the development of an atrial arrhythmogenic substrate in hypertension is unknown. Methods: Eight-week-old obese spontaneously hypertensive rats (SHR-ob) were treated for six weeks with the gut-specific NHE3-inhibitor SAR (1-(beta-D-glucopyranosyl)-3-{3-[(4S)-6,8-dichloro-2-methyl-1, 2,3,4-tetrahydroiso-chinolin-4-yl]phenyl}urea, 1 mg/kg/d in chow, SHR-ob SAR, n = 7) and compared to aged-matched placebo-treated SHR-ob (SHR-ob PLAC, n = 8). Cardiac magnetic resonance imaging was performed at the end of the treatment period to assess atrial emptying function. Afterwards, local conduction disturbances and inducible atrial fibrillation (AF) duration were determined and histological analysis to quantify atrial fibrosis amount were performed. Results: Inhibition of intestinal NHE3 by SAR increased fecal sodium excretion, resulted in marked changes in feces electrolyte concentrations and water content, reduced blood pressure and preserved atrial emptying function (active total percent emptying: SHR-ob SAR: 0.47 +/- 0.05% vs. SHR-ob PLAC: 0.38 +/- 0.007, p <0.0001). Atrial fibrosis content was lower (21.4 +/- 2.5% vs. 36.7 +/- 1.2%, p <0.0001) and areas of slow conduction were smaller (2.5 +/- 0.09% vs. 5.3 +/- 0.2%, p <0.0001) in SHR-ob SAR compared to SHR-ob PLAC. Left atrial burst stimulation resulted in shorter inducible AF-durations in SHR-ob SAR compared to SHR-ob PLAC. Conclusions: Reduction of intestinal sodium absorption and subsequent changes in feces milieu by pharmacological NHE3 inhibition in the gut preserved atrial emptying function and reduced AF susceptibility. Whether pharmacological NHE3 inhibition in the gut prevents AF in humans warrants further study. (C) 2020 The Authors. Published by Elsevier B.V

    Адаптивные изменения системы менеджмента качества организации

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    Цель работы – улучшение деятельности организации путем применения новых концепций менеджмента качества. В результате исследования разработано: рекомендации для перехода на новую версию стандарта ISO 9001:2015, формы по разделам стандарта: 4.1 Понимание организации и ее среды, 4.2 Понимание потребностей и ожиданий заинтересованных сторон, 6.1 Действие в отношении рисков и возможностей, 7.5 Документированная информация; методика по оценке знаний в организации. Область применения: организации, у которых внедрена и действует система менеджмента качества. Значимость работы: разработанные рекомендации лягут в основу при переходе на новую версию стандарта ISO 9001.The work purpose – improvement of activity of the organization by application of new concepts of quality management. As a result of research it is developed: recommendations for transition to the new version of the ISO 9001:2015 standard forms according to sections of the standard 4.1 Understanding of the organization and its environment, 4.2 Understanding of requirements and expectations of interested parties, 6.1 Action concerning risks and opportunities, 7.5 Documentary information; technique according to knowledge in the organization. Scope: the organizations at which it is introduced and the quality management system works. Importance of work: the developed recommendations will form the basis upon transition to the new version of the ISO 9001 standard