What is a bundle branch block?

A bundle branch block is a kind of heart block, which is a disorder of the heart’s conduction pathways. 

Heart blocks are sometimes classified as arrhythmias, because they can cause heart rhythm problems, but bundle branch blocks typically don’t, so we have given them their own section.

Atrioventricular block, which is another kind of heart block, does cause an arrhythmia (bradycardia – an abnormally slow heart rate) so we discuss that in our Arrhythmias section.

If you have a bundle branch block, the electrical signals that control your heart’s rate and rhythm are disrupted, or blocked, at some point as they travel from the SA node in the right atrium down into the ventricles.

Your heart will usually compensate and channel the electrical signals around the blockage. In most cases, you may not even be aware that you have a bundle branch block.

Heart block is categorized according to where the conduction block occurs, and there are three main types: Atrioventricular block (discussed in Arrhythmias), and right and left bundle branch block (discussed here).

To learn more about how your heart’s electrical signals work, take a look at Your heart’s electrical system.