1. The Incomplete Left Bundle Branch Block
R.H. Wasserburger, M.D., D.H. White, M.D., E.R. Lindsay, M.D. 
Diseases of the Chest 
Volume 43, Issue 6, Pages (June 1963)
DOI: /chest
Copyright © 1963 The American College of Chest Physicians Terms and Conditions

2. FIGURE 1
Classic examples of the ILBBB. Note the loss of the normal septal q wave in the left ventricular leads, with replacement by an initial r wave.
Diseases of the Chest  , DOI: ( /chest )
Copyright © 1963 The American College of Chest Physicians Terms and Conditions

3. FIGURE 2
The rR1 configuration of the ILBBB may be seen to best advantage in Leads I and AV1.
Diseases of the Chest  , DOI: ( /chest )
Copyright © 1963 The American College of Chest Physicians Terms and Conditions

4. FIGURE 3
The initial r wave of the ILBBB may appear as only a gross slur at the inception of the left ventricular R wave. The activation time of the left ventricular R wave, recorded from the preceding isoelectric line to the peak of the R wave, measures 0.06 sec.
Diseases of the Chest  , DOI: ( /chest )
Copyright © 1963 The American College of Chest Physicians Terms and Conditions

5. FIGURE 4
ILBBB secondary to previous myocardial infarction. rR' complexes are identified in V5 and V6 of patient G. N., age 40, while grossly slurred left ventricular R waves are present with J. S., age 68 years and J. B., age 62 years.
Diseases of the Chest  , DOI: ( /chest )
Copyright © 1963 The American College of Chest Physicians Terms and Conditions

6. FIGURE 5
The initial septal r wave of the ILBBB is identified in VB, with an apparent initial q wave in V5. Actually, the initial septal r wave is also present in V6, albeit of limited amplitude, and the apparent q wave in V6 is in fact, an s wave.
Diseases of the Chest  , DOI: ( /chest )
Copyright © 1963 The American College of Chest Physicians Terms and Conditions