Cardiac Near-Field Morphology During Conduction Around a Microscopic Obstacle—A Computer Simulation Study

Abstract

In a recent paper, we described the behavior of the cardiac electric near-field, E, parallel to the tissue surface during continuous conduction. We found that the tip of E describes a vector-loop during depolarization with the peak field, $\hat E$, pointing opposite to the direction of propagation, $\varphi _{I_m }$. Experimentally recorded loop morphologies of E, however, frequently showed significant deviations from the theoretically predicted behavior. We hypothesized that this variety of morphologies might be caused by conduction obstacles at a microscopic size scale. This study examines the influence of obstacles on the morphology of vector loops of E and whether the peak of distorted loops remains a reliable indicator for the direction of propagation. We used a computer model of a sheet of cardiac tissue with a central conduction obstacle immersed in an unbounded volume conductor. We studied the loop morphologies of E and the differences between the intracellularly determined direction of propagation, $\varphi _{I_m }$, and the direction of $\hat E$, ϕ _{E}. Distortions of the vector loop were morphologically similar to those observed experimentally. Differences between $\varphi _{I_m }$ and ϕ _{E} were less than 18° at all observation sites. The obstacle led to deformations of the loop morphology, particularly during the initial and terminal phases, and to a lesser degree near the instant of $\hat E$. We concluded that $\hat E$ is a reliable indicator of $\varphi _{I_m }$. © 2003 Biomedical Engineering Society.

PAC2003: 8719Hh, 8710+e, 8719Nn