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Electrical Function (electrical + function)
Selected AbstractsThe Role of Cardiac Tissue Alignment in Modulating Electrical FunctionJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2007CHIUNG-YIN CHUNG M.S. Introduction:,Most cardiac arrhythmias are associated with pathology-triggered ion channel remodeling. However, multicellular effects, for example, exaggerated anisotropy and altered cell-to-cell coupling, can also indirectly affect action potential morphology and electrical stability via changed electrotonus. These changes are particularly relevant in structural heart disease, including hypertrophy and infarction. Recent computational studies showed that electrotonus factors into stability by altering dynamic properties (restitution). We experimentally address the question of how cell alignment and connectivity alter tissue function and whether these effects depend on the direction of wave propagation. Methods and Results:,We show that cardiac cell arrangement can alter electrical stability in an in vitro cardiac tissue model by mechanisms both dependent and independent of the direction of wave propagation, and local structural remodeling can be felt beyond a space constant. Notably, restitution of action potential duration (APD) and conduction velocity was significantly steepened in the direction of cell alignment. Furthermore, prolongation of APD and calcium transient duration was found in highly anisotropic cell networks, both for longitudinal and transverse propagation. This is in contrast to expected correlation between wave propagation direction and APD based on electrotonic effects only, but is consistent with our findings of increased cell size and secretion of atrial natriuretic factor, a hypertrophy marker, in the aligned structures. Conclusion:,Our results show that anisotropic structure is a potent modulator of electrical stability via electrotonus and molecular signaling. Tissue alignment must be taken into account in experimental and computational models of arrhythmia generation and in designing effective treatment therapies. [source] Proceedings of the Third International Workshop on Computer Simulation and Experimental Assessment of Cardiac Electrical FunctionJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 2003ANDRÉ KLÉBER M.D., Ph.D. No abstract is available for this article. [source] Towards predictive modelling of the electrophysiology of the heartEXPERIMENTAL PHYSIOLOGY, Issue 5 2009Edward Vigmond The simulation of cardiac electrical function is an example of a successful integrative multiscale modelling approach that is directly relevant to human disease. Today we stand at the threshold of a new era, in which anatomically detailed, tomographically reconstructed models are being developed that integrate from the ion channel to the electromechanical interactions in the intact heart. Such models hold high promise for interpretation of clinical and physiological measurements, for improving the basic understanding of the mechanisms of dysfunction in disease, such as arrhythmias, myocardial ischaemia and heart failure, and for the development and performance optimization of medical devices. The goal of this article is to present an overview of current state-of-art advances towards predictive computational modelling of the heart as developed recently by the authors of this article. We first outline the methodology for constructing electrophysiological models of the heart. We then provide three examples that demonstrate the use of these models, focusing specifically on the mechanisms for arrhythmogenesis and defibrillation in the heart. These include: (1) uncovering the role of ventricular structure in defibrillation; (2) examining the contribution of Purkinje fibres to the failure of the shock; and (3) using magnetic resonance imaging reconstructed heart models to investigate the re-entrant circuits formed in the presence of an infarct scar. [source] Improving the ON/OFF Ratio and Reversibility of Recording by Rational Structural Arrangement of Donor,Acceptor MoleculesADVANCED FUNCTIONAL MATERIALS, Issue 5 2010Ying Ma Abstract Organic molecules with donor,acceptor (D,A) structure are an important type of material for nanoelectronics and molecular electronics. The influence of the electron donor and acceptor units on the electrical function of materials is a worthy topic for the development of high-performance data storage. In this work, the effect of different D,A structures (namely D,,,A,,,D and A,,,D,,,A) on the electronic switching properties of triphenylamine-based molecules is investigated. Devices based on D,,,A,,,D molecules exhibit excellent write,read,erase characteristics with a high ON/OFF ratio of up to 106, while that based on A,,,D,,,A molecules exhibit irreversible switching behavior with an ON/OFF ratio of about (3.2,×,101),(1,×,103). Moreover, long retention time of the high conductance state and low threshold voltage are observed for the D,A switching materials. Accordingly, stable and reliable nanoscale data storage is achieved on the thin films of the D,A molecules by scanning tunneling microscopy. The influence of the arrangement of the D and A within the molecular backbone disclosed in this study will be of significance for improving the electronic switching properties (ON/OFF current ratio and reversibility) of new molecular systems, so as to achieve more efficient data storage through appropriate design strategies. [source] Electrocardiographic Alterations during Hyperinsulinemic Hypoglycemia in Healthy SubjectsANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2008Tomi Laitinen M.D. Background: We evaluated the arrhythmogenic potential of hypoglycemia by studying electrocardiographic (ECG) changes in response to hyperinsulinemic hypoglycemia and associated sympathoadrenal counterregulatory responses in healthy subjects. Methods: The study population consisted of 18 subjects, aged 30,40 years. Five-minute ECG recordings and blood samplings were performed at baseline and during the euglycemic and hypoglycemic hyperinsulinemic clamp studies. PR, QT, and QTc intervals of electrocardiogram and ECG morphology were assessed from signal-averaged ECG. Results: Although cardiac beat interval remained unchanged, PR interval decreased (P < 0.01) and QTc interval (P < 0.001) increased in response to hyperinsulinemic hypoglycemia. Concomitant morphological alterations consisted of slight increases in R-wave amplitude and area (P < 0.01 for both), significant decreases in T-wave amplitude and area (P < 0.001 for both), and moderate ST depression (P < 0.001). Counterregulatory norepinephrine response correlated with amplification of the R wave (r =,0.620, P < 0.05) and epinephrine response correlated with flattening of the T wave (r =,0.508, P < 0.05). Conclusions: Hyperinsulinemic hypoglycemia with consequent sympathetic humoral activation is associated with several ECG alterations in atrioventricular conduction, ventricular depolarization, and ventricular repolarization. Such alterations in cardiac electrical function may be of importance in provoking severe arrhythmias and "dead-in-bed" syndrome in diabetic patients with unrecognized hypoglycemic episodes. [source] | ||||||||||