Bundle Branch Blocks (Part 1 – Left and Right Bundle Branch Blocks)
A bundle branch block is a disorder in which there is an obstruction in the heart’s electrical conduction system. These can be broadly divided into two different types of block:
Left bundle branch block (LBBB) – where the obstruction is in the left bundle branch
Right bundle branch block (RBBB) – where the obstruction is in the right bundle branc
Left bundle branch blocks
In left bundle branch block (LBBB) the left ventricle is not directly activated by impulses travelling through the left bundle branch. The right ventricle, however, is still activated as normal by the right bundle branch.
The left ventricle is activated by impulses travelling through th
e myocardium across the septum. As this occurs more slowly than conduction through the bundle of His the QRS complex becomes widened.
