A bundle branch block is a disorder with the heart’s rhythm. Normally, the electrical impulse travels down both the right and left branches of the heart at the same speed so that both ventricles contract at the same time. A bundle branch block is when there’s a block in one of the branches, so one ventricle contracts a fraction of a second slower than the other. A bundle branch block shows up as an abnormality in an electrocardiogram, but usually no treatment is required unless other symptoms are present. Your healthcare provider will want to see you regularly to be sure no other changes occur.