Analysis of Current Density Distribution during Transesophageal Pacing Using the Finite-Element Model

Abstract

For patients requiring temporary cardiac pacing or in occasions when a rapid and precise control of the heart rate is needed, electrical stimulation of the heart from the esophagus can be used. Determination of the pacing threshold for transesophageal atrial or ventricular pacing remains largely an empirical process. In this paper we present a novel approach in quantifying transesophageal electrostimulation of the heart. The goal of this study is to investigate the capacity of computational models for the analysis of current density distribution during transesophageal pacing. We constructed the finite-element model from segmented images of transversal cross-sections of the thorax. Electrical conductivity of the segmented regions (esophagus, heart, aorta, lungs, etc.) was assumed to be homogenous and isotropic. We obtained solutions for the current density distribution in the thorax for two types of pacing leads: (i) a conventional lead having cylinder shape electrodes and (ii) a selective lead where electrodes comprise only a part of cylinder’s side surface. We estimated stimulation regions and compared numerical results for the current density with previous studies in which these two types of pacing leads were analyzed without taking into account inhomogeneous conductivity of the thorax. Advantages of selective lead over conventional one were demonstrated. Numerical experiments indicate that analysis of current density distribution using the finite-element model is useful for the optimization of the pacing lead geometry, optimization of the insertion depth of the lead, and optimization of the stimulus amplitude.