Ventricular activation process and genesis of QRS complex in the goat

Abstract

The pathways of ventricular excitation in the interventricular septum and the free walls of the ventricles were determined in the goat. During the first 5 msec. of the QRS complex, activity occurs in a cup-shaped zone formed around the apex of the left ventricular cavity, consisting of the left endocardial portions of the septum and the endocardium of the free wall. Within the next 10 msec. of the QRS, the apical third of the septum is excited, simultaneously, from both the left and the right ventricular endocardial surfaces. Also, all of the ventricles, except the bases and a small epicardial apical area of the left ventricle, are excited with almost a single burst of depolarization. During the next 3–5 msec. the ventricular bases and the small apical epicardial area are excited along with the middle third of the interventricular septum. The final 15 msec. of the QRS and approximately 3 msec. of the following isoelectric period are inscribed during activation of the basilar third of the septum.