When conduction through the right bundle is partially blocked or slowed, some of the right ventricle will be activated after the left ventricle has been depolarized. This is referred to as incomplete RBBB.
When the magnitude of block in the right bundle is greater or complete. i, it is freferred to as complete RBBB. When this occurs, the right ventricle is activated by impulses reaching the right ventricular myocardium after activation of the interventricular septum and cardiac apex rather than via the right bundle and right ventricular Purkinje network. Because impulse transmission through the ventricular myocardium is significantly slower than transmission through the His-Purkinje system, much of the right ventricle will be activated after the left ventricle has been depolarized, as depicted in this graphic