Bundle Branch Blocks
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- term used to indicate both delay or failure of depolarization
- an intraventricular block may occur in one of the branches of the His bundle (BBB) or w/in the myocardium ("non-specific intraventricular block" or "non-specific intraventricular block")
Complete Left/Right BBB
- QRS > 0.12 secs
- depolarization of the affected ventricle is completely dependent on the controlateral branch
- activation must travel thru the septum which has no specific conducting fibers
- slow cell-to-cell septal conduction cause prolongation of the QRS duration to 120 msec. (0.12 secs)
pertaining to, situated on, or affecting the opposite side.
Incomplete Left/Right BBB
- QRS < 120 msec
- affected ventricle is only partially dependent on the controlateral branch and the QRS duration is mildly increased
Criteria for Complete LBBB
- 1. prolonged QRS (> 0.12 secs)
- 2. broad, slurred or notched R in I, V5, and V6
- 3. small, initial R and broad, deep S in V1 and V2
LBBB 0.02 secs
When the electrical impulse thru the left bundle or its fascicles is severely delayed or interrupted (complete LBBB), the ventricular depolarization depends on the right bundle and therefore starts low on the right side of the septum.
a small bundle or cluster, especially of nerve, tendon, or muscle fibers
LBBB 0.04 secs
As the septum is thicker than the right ventricular wall, the right-to-left septal vectors predominate. There is no Q wave on the left
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