Welch Allyn Cardioperfect Workstation, PEDMEANS ECG Interpretation Module - Physicians - User Manual - Manual (Page 12)

CardioPerfect Workstation
PEDMEANS ECG Interpretation Module Physicians Manual
DIR 80015051 Rev. C 12 / 55
2.3 Left Bundle Branch Block (LBBB)
In LBBB the septal depolarization proceeds leftward from the right ventricle, resulting in a loss of the Q
wave in I and/or V6. The left ventricle is depolarized through the ventricular myocardium at a much
slower rate, producing prolongation of the QRS duration for age. The axis of the QRS complex is
directed to the left and posteriorly, resulting in wide R waves in I, V6, and V7, and wide S waves in V1,
V2, and V3R. The duration criteria should be fulfilled in at least three leads to produce the statement
“LBBB.”
The diagnosis “probable LBBB” will be made if Q waves are found in I and V6.
Because LBBB is rare in very young children, only possible LBBB statements are made below one
month.
Skip tests
if:
QRS duration

ULN + 10 ms
Say: “LBBB”
if: no Q wave in 1 of I, V6
and three or more leads with
R duration > ULN in I, V6, V7
or S duration > ULN in V1, V2, V3R
and age > 30 days
Say:
“probable LBBB”
if: three or more leads with
R duration > ULN in I, V6, V7
or S duration > ULN in V1, V2, V3R
and age > 30 days
Say:
“possible LBBB”
if: three or more leads with
R duration > ULN in I, V6, V7
or S duration > ULN in V1, V2, V3R
and age

30 days