Simulation of the influence of voltage level and pulse spacing on the efficiency, aggressiveness and uniformity of the electroporation process in tissues using meshless techniques.

Electroporation is a widely used method consisting of application of high-voltage, short-duration electric pulses to increase cell membrane permeability, allowing cellular internalization of medications. In this work, the influence of two primary parameters, voltage level (V) and pulse spacing (N), on electroporation efficiency, uniformity and aggressiveness, as quantified by the total mass transport to viable cells, intracellular concentration gradients and an aggressiveness factor introduced here, is studied by means of numerical simulations of drug transport in electroporated tissues. The global method of approximate particular solutions (Global MAPS) is used to solve the governing equations, together with domain scaling, singular value decomposition and smoothing algorithms, to address the ill-conditioning of the final system and suppress small scale oscillations. The accuracy of Global MAPS is evaluated by comparing the initial extracellular concentration, Ce , and final intracellular concentration, Ci , with previous finite volume method results, obtaining similar behavior of Ce and Ci along the tissue domain, with some differences for Ci in high-gradient zones. According to the Global MAPS results, the influence of V and N on Ci is only significant over a certain range, within which the largest drug transport to viable cells occurs. In general, both electroporation efficiency and aggressiveness change in nonuniform manner with V and decrease with N, whereas the electroporation uniformity decreases as V increases and N decreases. The contour plots obtained here can be considered useful tools to compare electroporation-based treatments in terms of their efficiency, aggressiveness and uniformity, assisting in the selection of a suitable treatment plan for cancer.

Remodelado estrcctural y de gap junctions en un modelo 3d de aurícula humana / Strctural remodeeling and of gap junctions in a 3d model of human atrial

Introducción: la fibrilación auricular (AF), es la más común de la arritmia cardiaca sostenida y un factor de riesgo para el accidente cerebro vascular y otras morbilidades, si no es tratada. Estudios epidemiológicos muestran que la AF tiende a perpetuarse con el tiempo, generando cambios electrofisiológicos y anatómicos denominados: remodelados auriculares. Se ha demostrado que estos cambios provocan variaciones de la velocidad de conducción (CV), en el tejido auricular. Objetivo: estudiar el efecto del remodelado de gap junctions en la propagación del potencial de acción, implementando un modelo 3D de aurícula humana altamente realista. Materiales y Métodos: se incorporaron los cambios generados por el remodelado eléctrico a un modelo de potencial de acción (AP) de miocito auricular, acoplado con un modelo tridimensional anatómicamente realista de aurícula humana dilatada. Mediante simulaciones de la propagación del AP en condiciones de remodelado eléctrico y anatómico, y de remodelado de gap junctions, se midieron las ventanas vulnerables de generación de reentradas en la base de las venas pulmonares izquierdas de la aurícula. Resultados: los resultados obtenidos indican que la ventana vulnerable en el remodelado de gap junctions, se desplazó 38 ms con relación al modelo dilatado, lo que nos muestra el impacto de la dilatación con remodelado de gap junction. Conclusiones: el remodelado eléctrico generó una disminución del 70 % en la duración del potencial de acción y una disminución de las velocidades de conducción entre un 14.6 y un 26 %, que fueron medidas en diferentes regiones de la aurícula dilatada. El foco disparado en la base de las venas pulmonares izquierdas, generó un frente de onda que mantiene una actividad reentrante debido a la anatomía subyacente de las venas pulmonares.

Introduction: Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and a significant risk factor for cerebrovascular accident and other morbidities if left untreated. Epidemiological studies show that AF tends to persist over time, creating electrophysiological and anatomical changes called atrial remodeling. It has been shown that these changes result in variations in conduction velocity (CV) in the atrial tissue. Objective: to study the effect of remodeling of gap junctions in the propagation of the action potential by implementing a highly realistic 3D human atrial model. Materials and methods: the changes caused by electrical remodeling were incorporated in an atrial myocyte action potential (AP) model coupled with an anatomically realistic three-dimensional model of dilated human atria. Through simulations of the AP spread in variations of anatomical and electrical remodeling and of gap junctions remodeling, vulnerable windows of reentry generation were measured at the base of the atrium left pulmonary veins. Results: the results obtained indicate that vulnerable window in the gap junctions remodeling moved 38 ms in relation with the expanded model which shows the impact of the dilatation gap junction remodeling. Conclusions: the electrical remodeling produced 70% decrease in action potential duration and decreased conduction velocities between 14.6 and 26 %, which were measured in different regions of the dilated atrium. The focus shot at the base of the left pulmonary veins created a wave which maintains a reentering activity due to the underlying anatomy of the pulmonary veins.