Bundle branch block
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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
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 W 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.