Modelisation de la propagation de l'impulsion electrique dans un modele de tissu cardiaque tridimensionnel (French text)

This study describes a computer model of electrical propagation in a cardiac tissue in order to investigate the factors affecting the stability of cardiac reentrant activity.; As a preliminary step leading to study the reentrant activity, we begin studying the propagation of electrical excitation in a two and three-dimensional model of cardiac tissue.; The action potential duration restitution curve relates the action potential duration (APD) at a given point in the tissue with the previous diastolic interval (DI) at the same point.; In our model, the dynamic of the reentry around a functional block was analyzed by the APD-restitution curve and the variations of the slope of these curve as a function of one or more parameters of the membrane model. This approach was tested in an isolated cell in order to identify the role of each parameter. We changed the conductance of the sodium, potassium, and slow inward current up and down from their nominal values. We found that the calcium and potassium channels conductances affect considerably the corresponding restitution curve and its slope.; The identification of the significant parameters will lead us to the question about the utility of this approach to study the dynamic of reentrant activity in a multidimensional preparation model. To do so, we tested this approach in a two-dimensional model. The simulation results allow us to see the different types of reentry when we change the conductance g¯ _si and g¯_k of the calcium and potassium currents, respectively. A stable reentry was observed when: the value of calcium conductance g¯_si is less than 0.03 mS/cm2 and the value of the time dependent potassium conductance g¯_k is greater than 1.974 mS/cm 2. For values g¯_si varying between 0.03 and 0.04 mS/cm2, we observed a breakup of wave front and a small excitable gap. For higher values of g¯_si, this breakup generates multiple wave fronts and a complete disorganization of electrical activity, which looks similar to fibrillation. We noted that the conductance reduction allows us to obtain an action potential and an absolute refractory period of short duration. These conditions facilitate the initiation of sustained reentry in a tissue of small dimensional. (Abstract shortened by UMI.)...