These ECGs were recorded before and after the development of right bundle branch block and were shown earlier on page 3.1.7. They are shown again here to point out the changes in repolarization that are secondary to the development of the intraventricular conduction disturbance. Note that following the development of right bundle branch block, the upright T waves in leads I, II, V5 and V6 become exaggerated and the T wave in lead V1 becomes inverted. These T wave changes reflect the changes in the sequence of repolarization that are secondary to the changes in sequence of depolarization.