Cantalapiedra, I.R. (Inma R.)

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    Conductance heterogeneities induced by multistability in the dynamics of coupled cardiac gap junctions
    (2021) Laroze, D. (David); Hawks-Gutiérrez, C. E. (Claudia Elisabeth); Echebarría, B. (Blas); Cantalapiedra, I.R. (Inma R.); Witt, A. (A.); Peñaranda, A. (Angelina); Elorza-Barbajero, J. (Jorge); Bragard, J. (Jean)
    In this paper, we study the propagation of the cardiac action potential in a one-dimensional fiber, where cells are electrically coupled through gap junctions (GJs). We consider gap junctional gate dynamics that depend on the intercellular potential. We find that different GJs in the tissue can end up in two different states: a low conducting state and a high conducting state. We first present evidence of the dynamical multistability that occurs by setting specific parameters of the GJ dynamics. Subsequently, we explain how the multistability is a direct consequence of the GJ stability problem by reducing the dynamical system's dimensions. The conductance dispersion usually occurs on a large time scale, i.e., thousands of heartbeats. The full cardiac model simulations are computationally demanding, and we derive a simplified model that allows for a reduction in the computational cost of four orders of magnitude. This simplified model reproduces nearly quantitatively the results provided by the original full model. We explain the discrepancies between the two models due to the simplified model's lack of spatial correlations. This simplified model provides a valuable tool to explore cardiac dynamics over very long time scales. That is highly relevant in studying diseases that develop on a large time scale compared to the basic heartbeat. As in the brain, plasticity and tissue remodeling are crucial parameters in determining the action potential wave propagation's stability. (C) 2021 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
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    Phase-2 reentry in cardiac tissue: Role of the slow calcium pulse
    (American Physical Society, 2010-07-13) Echebarría, B. (Blas); Cantalapiedra, I.R. (Inma R.); Peñaranda, A. (Angelina); Bragard, J. (Jean)
    Phase-2 re-entry is thought to underlie many causes of idiopathic ventricular arrhythmias as, for instance, those occurring in Brugada syndrome. In this paper, we study under which circumstances a region of depolarized tissue can re-excite adjacent regions that exhibit shorter action potential duration APD , eventually inducing reentry. For this purpose, we use a simplified ionic model that reproduces well the ventricular action potential. With the help of this model, we analyze the conditions that lead to very short action potentials APs , as well as possible mechanisms for re-excitation in a cable. We then study the induction of re-entrant waves spiral waves in simulations of AP propagation in the heart ventricles. We show that re-excitation takes place via a slow pulse produced by calcium current that propagates into the region of short APs until it encounters excitable tissue. We calculate analytically the speed of the slow pulse, and also give an estimate of the minimal tissue size necessary for allowing reexcitation to take place.
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    Huge reduction of defibrillation thresholds four electrode defibrillators. 2014
    (Institute of Electrical and Electronics Engineers (IEEE), 2014) Simic, A. (Ana); Cantalapiedra, I.R. (Inma R.); Elorza-Barbajero, J. (Jorge); Bragard, J. (Jean)
    In the absence of a better solution, ventricular fibrillation is treated by applying one or several large electrical shocks to the patient. The question of how to lower the energy required for a successful shock is still a current issue in both fundamental research and clinical practice. In the study presented here we will compare defibrillation applied through a four electrode device with the standard procedure using two electrodes. The method is tested through intensive numerical simulations. Here we have used a one dimensional geometry. At the level of the cardiac tissue, the bidomain and the modified Beeler-Reuter models were used. Three different shock waveforms are tested: monophasic and two types of biphasic shocks. The results are compared with those obtained with standard two electrode device. A significant reduction in defibrillation thresholds is achieved for all the three tested waveforms when we use a four electrode device.