ABSTRACT
The propagation of the cardiac impulse is a multifactorial process that depends on the electrical properties associated with cell excitability, the degree of cell-to-cell communication, the geometrical arrangements of intercellular connections and the gross three-dimensional anatomical structure of the atria and ventricles, as well as the heart rate. This chapter is concerned with the way in which electrical activity is transmitted throughout the heart. The discussion starts with a general description of how the ionic currents that move across a given patch of membrane lead to propagation along the membrane, so that the electrical signal originated at one site can spread within a cell and from cell to cell to induce the electrical activation of the entire heart. Subsequently, the contributions of each of the above factors to the phenomenon of propagation are discussed, particularly in regards to their individual roles in normal and abnormal propagation in one-, two-and three-dimensional cardiac muscle. However, it is necessary to emphasize that in this chapter the reader will not find a comprehensive quantitative analysis of the biophysical, biochemical or electrophysiologic process involved in cardiac impulse propagation. The goal, in fact, is to introduce the uninitiated to basic concepts on the electrophysiology of continuous and discontinuous cardiac impulse propagation, as well as to the mechanisms of rate-dependency of propagation, and to the lesser known ideas of nonlinear dynamics and chaos, as applied to the understanding of cardiac conduction abnormalities.
