Left Bundle Block

[Dr Colts]

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Long time lurker here, first time poster because this is driving me crazy!!!!

Can somebody tell me why in a left bundle block on ECG, you see a negative dip (QS) in V1? If V1 is the right ventricle and the right ventricle is stimulated first in a left block, why wouldn't it be a positive peak?

 

[Aeterni]

Possibly due to the repolarization of the septum that would normally get swallowed up by the left ventricle depolarizing? I'm not really sure, we didn't go very in depth to any of the chest leads, so I'm just guessing.

 

[vanbamm]

Long time lurker here, first time poster because this is driving me crazy!!!!

Can somebody tell me why in a left bundle block on ECG, you see a negative dip (QS) in V1? If V1 is the right ventricle and the right ventricle is stimulated first in a left block, why wouldn't it be a positive peak?

If you recall, when a wave is coming towards a lead, it is a positive peak, when it is going away from a lead, it becomes a negative dip...in a LBBB, because of the position of V1, and the wave going away from this lead (heading LEFT), it is a negative dip.

 

[Dr Colts]

If you recall, when a wave is coming towards a lead, it is a positive peak, when it is going away from a lead, it becomes a negative dip...in a LBBB, because of the position of V1, and the wave going away from this lead (heading LEFT), it is a negative dip.

Doesn't the wave go toward the right before going toward the left? Why wouldn't V1 show it going to the right with a positive peak?

 

[vanbamm]

Doesn't the wave go toward the right before going toward the left? Why wouldn't V1 show it going to the right with a positive peak?

you will have a slight positive deflection of "r" (right vent. depol.), but "S"(left vent. depol.) will be negative as the impulse moves away from V1.

you are correct in that the transmission will head to the right initially as the left bundle is blocked, but after the delay, as cell to cell transmission occurs to the left, the negative deflection occurs in "S" in V1...