As discussed in the first chapter, normal depolarization of the left and right ventricles is initiated by the left-to-right activation of the interventricular septum from the left bundle branch of the conducting system and then occurs virtually simultaneously. However, because of the greater mass of the left ventricle, the electrical forces associated with depolarization of the right ventricle are largely obscured and the uncancelled forces are those associated with left ventricular depolarization.