Bundle branch block

Definition

Cessation of appropriate electrical conduction down either the left of right bundle branch.

Pathophysiology

• LBBB: aortic stenosis, dilated cardiomyopathy, MI, CAD.
• RBBB: atrial septal defect, PE, MI

ECG Changes

Classicaly, the mnemonic is WiLLiaM and MaRRoW. However, ViLLhelM and MaRRooN seems to be more accurate. Also, notice the wide QRS complexes. See the text if that doesn't make sense.

If you're not sure about bundle branch block, the classic mnemonic is WiLLiaM and MaRRoW. However, we think ViLLhelM and MaRRooN gives a slightly more accurate picture.

• LBBB: there is a V shape in V1 and an M shape in V6. The "V" wave is also called an rS wave because it has a very slight rise (r) and a big drop (S) in amplitude. The "M" wave, also called R, is just a large rise (R) with a tiny dip and tiny rise.
• RBBB: there is an M shape in V1 and an N shape in V6 (the N can also stand for "normal"). The "M" wave here has a small rise (r), a big drop (S) and an even bigger rise (R) giving an rSR wave. Finally, the N is your normal qRs complex but just wider.

In both cases, there is a wide QRS complex.

Management

Generally, you can just leave it but if the bundle branch block is severe, a pacemaker will need to be fitted.