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ResumenEn la actividad eléctrica cardiaca, distintos tipos de onda viajan a través del corazón. Presentamos un modelo de la actividad eléctrica del corazón, proponemos que los frentes de onda homogéneos que se propagan en el corazón son, de hecho, ondas solitarias, o “solitones”. Usamos un conjunto general de ecuaciones de reacción-difusión conocido como el modelo de Barrio-Varea-Aragón-Maini (BVAM)[1], el cual presenta una abundancia de bifurcaciones no lineales, siendo capaces de encontrar la ruta al caos usando un mapeo de las ecuaciones de amplitud a la dinámica de la ecuación compleja de Ginzburg-Landau. Estudiamos numéricamente la dinámica de los frentes de onda en el modelo BVAM para describir los mecanismos que conducen a la fibrilación en el corazón y comparamos los resultados con datos experimentales.AbstractIn cardiac electrical activity, different types of waves meander through the heart. We present a model of the electrical activity of the heart that proposes that the homogeneous wave fronts propagating through the heart are in fact solitons. We use a general set of reaction-diffusion equations known as the Barrio-Varea-Aragón-Maini (BVAM) model[1] that presents a wealth of non-linear bifurcations, and we are able to follow the route to chaos, using a mapping of the amplitude equations to the dynamics of the complex Ginzburg-Landau equation. We study the dynamics of wave fronts numerically in the BVAM model to describe the mechanisms leading to heart fibrillation and compare the findings with experimental data.

In this paper, we investigate the possibility to control the spiral waves and spatiotemporal chaos in an excitable media by subthreshold ordered waves, which is by definition in this paper the spatially ordered periodical subthreshold fluctuations of system variables. It is found that both the spiral wave and the spatiotemporal chaos could be driven out of the control domain by perturbation of periodical subthreshold ordered waves. The effective control time declines as the amplitude of subthreshold ordered waves are increased, or their frequencies are decreased. Furthermore, we show that the effectiveness of this method is also dependent on the spatial arrangement of the subthreshold ordered waves. We discuss the possible applications of this method, especially in the control of heart fibrillation.

The protection efficiency of insulating links under different operating conditions is analyzed. Both a steady-state model and a transient model have been developed for simulation of the system. The models simulate the electrical supply, the crane insulator link, the body impedance of the worker, and the grounding resistance. The MICROCAP AC, DC, and transient analysis program was used to calculate the current and voltages which endanger the crane worker. The results show that the insulating link in clean conditions reduces the current under the harmless let-go level. However, polluting and wetting the insulating link may increase the current above the dangerous ventricular fibrillation level. The contact between the power line and crane causes a short-duration high-amplitude transient current which, in adverse conditions, can cause heart fibrillation. Based on the experimental evidence, it is concluded that in spite of the shortcomings, the insulator link increases the safety of crane operation. Furthermore, the model and calculation method can be used for the evaluation of new crane insulator systems. >

Based on the equations of Keener, a novel and simple circuit model capable of generating chaotic activities similar to those that can occur in the heart is presented. The circuit consists of two RC cells, a mono-stable multi-vibrator, and a pulse generator, and is suitable for VLSI design. PSpice simulations are run to verify its performance. This model could be used to examine the possible reasons for the existence of these activities in the heart and will hopefully help to eliminate these causes.

Despite over a century's study, the trigger mechanisms of cardiac arrhythmias are poorly understood. Modern experimental methods do not provide sufficient temporal and spacial resolution to trace the development of fibrillation in samples of cardiac tissue, not to mention the heart in vivo. Computer simulations of electrical activity in cardiac tissue offer increasingly detailed insight into these phenomena, providing a view of cellular-level activity on the scale of whole heart chambers (atria or ventricles). Already, advances in this field have led to developments in our understanding of heart fibrillation and sudden cardiac death and their impact is expected to increase significantly as we approach the ultimate goal of whole-heart modelling. This paper presents a roadmap for the development of Beatbox; a computer simulation environment for computational biology of the heart-an adaptable and extensible framework with which high performance computing may be harnessed by researchers.

We present a three-dimensional (3D) computer model that simulates electrical activity in the heart during fibrillation. A real dog heart is discretized to form 1473 interconnected cubic elements. The model exhibits normal activation and recovery from pacing. Five or more extrastimuli induce a self-sustaining tachyarrhythmia that soon degenerates into a fibrillatory rhythm. The extrastimuli increase the excitability of the myocardial cell population. The result is a rapid re-excitation of cells that allows for only a partial recovery of cell action potential. This suggests that a dispersion of refractory states of the cell population is the cause of fibrillation in this computer model.

Preliminary adaptation to short-term stress was shown to prevent the decrease in the heart fibrillation threshold and an increase in ectopic activity which is usually observed in experimental myocardial infarction. This protective effect involves an enhanced activity of the antioxidant system. Therefore, a synthetic antioxidant ionol was applied to prevent disturbances of the heart electrical stability in infarction. It was established that ionol completely prevents the decrease in the electrical threshold and the increase in ectopic activity of the heart in experimental infarction. Thus, it can be concluded that ionol possesses an antiarrhythmic effect.

Advantageous usage of the parallel computation properties of the classical hybrid computer in the simulation of action potential propagation along myocardial tissue forms the topic of this paper. Considerable reduction of computation time, ease of intervention into the process and live display of time courses facilitates theoretical model research in heart fibrillation.

A new antiarrhythmic drug ethmozin was studied in the experiment and clinics. The drug is effective against atrial and ventricular forms of arrhythmia. According to its electrophysiological properties it may be attributed to the first group of antiarrhythmic drugs. Ethmozin improves heart blood supply, has essentially no effect on the arterial pressure level, conductivity, or myocardial contractility. High efficiency and good tolerance of the drug permit to recommend ethmozin for the treatment of ventricular rhythm disturbances, preciding the development of heart fibrillation.