Comparison of models to estimate the maximal transmembrane electrical potential variation induced by electrical fields in isolated cardiomyocytes of rats of different ages

Author(s)

Hugo Fernando Maia Milan

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Elétrica e de Computação
• Defense date: 2015-01-27

Examining board members

José Wilson Magalhães Bassani; Airton Ramos; Eduardo Tavares Costa

• Advisor: José Wilson Magalhães Bassani; Rosana Almada Bassani

Abstract

Considering that stimulation with external electrical fields (E) is clinically used for arrhythmia treatment, it is important to understand the phenomenon of membrane polarization by E. Action potential and contraction triggering by E in cardiomyocytes depends on the induction of a transmembrane potential variation (?Vm) sufficient for the attainment of the excitation threshold. Due to the limitations of the methods currently available for measurement of ?Vm and its maximum value, ?Vmax, electromagnetic models represent an important tool for this purpose. However, the calculated values depend on how the membrane polarization phenomenon is modeled. The electromagnetic models available in the literature approximate the cardiomyocyte irregular shape to regular geometries. Nevertheless, it has not been ascertained yet which model is the most appropriated to estimate ?Vmax in these cells, of which both dimensions and shape vary markedly during postnatal development, and often present geometric irregularities. Thus, approximation of the cell shape to regular geometries may result in a considerable error in the ?Vm estimation. The aim of this study was to develop a three-dimensional numerical model (MN3D) based on the irregular cell shape and to compare the values of ?Vmax induced by the threshold E (?VL) estimated with this model with those calculated with simplified models, such as the twodimensional numerical model (MN2D) and the analytical models for cylinder (MACil), sphere (MAEsf), prolate spheroid (MAEsPr), and ellipsoid (MAElip). To estimate ?VL, the threshold E and cell dimensions were measured in cardiomyocytes isolated from neonatal (5-7 days), weaning (28-32 days) and adult (4-6 months) rats, for 6 ranges of the angle between the directions of E and the cell major axis. Electromagnetic calibration of the models showed that MN2D and MACil were not suitable for ?Vmax estimation in these cells. While ?VL estimated with MN3D and MAEsPr were angle-independent, but dependent on the animal's age, the opposite was observed regarding the estimates made with MAElip. Under certain conditions, ?VL values estimated with MAEsPr were the closest to those obtained with MN3D. It is concluded that MAEsPr, a less technically complex model, can provide reliable ?VL estimates provided that the angle between the directions of E and the cell major axis is small (up to 30º) (AU)

• FAPESP's process: 13/05441-5 - Interaction of electrical fields with cardiac myocytes: calculation of induced transmembrane potential with electromagnetic model
• Grantee: Hugo Fernando Maia Milan
• Support Opportunities: Scholarships in Brazil - Master