[Vectorcardiography of variations in localization of specific conduction systems in the left ventricle]

A realistic computer model of propagation of ventricular activation was used to study the effects of varying the position of specific conduction system terminations in the left ventricle and the septum, representing the sites of initial activation, on the resulting simulated spatial heart vectors. Three differently localized foci of initial activation, each of them represented by one model element, were considered: in the central part of the left septal surface, posteriorly at about one third of the distance from the apex to the base, and in the upper part of the anterior free wall. During the model experiments, the positions of the initial activation were shifted +/- 5 model units (ca 5 mm) in the vertical and lateral direction either separately or in different mutual combinations. Small variations of the initial activation site in the basal parts of the left ventricle led to significantly smaller changes of the vectorcardiographic loop than variations of the same extent with the initial activation site located more apically.