Introduction to the 12-lead ECG

TO BE COMPLETED

Bundle Branch Blocks

In BBB, one or the other (or both) of these bundle branches no longer conduct electrical impulses normally. This can occur from disease or damage to one of the bundle branches, or it may occur for no apparent reason in completely healthy people. When the electrical impulse is delayed in reaching its respective ventricle, the delay shows up as a distinctive pattern on the ECG called a BBB. The chief effect of a BBB is to disrupt the normal, coordinated and simultaneous contraction of the two ventricles. The contraction of one ventricle (the one whose bundle branch is blocked) occurs slightly after the contraction of the other.

People with BBB usually will have either right bundle branch block (RBBB) or left bundle branch block (LBBB), depending on which of the two bundle branches is "blocked." Sometimes both bundle branches are affected, and the BBB pattern on the ECG is not clearly identifiable as either right or left BBB - in this case, the BBB is referred to as an intraventricular conduction delay (IVCD).