In patients without myocardial infarction, acute left anterior hemiblock produces specific changes in the initial and maximal QRS vectors. The orientation of the initial 10 to 20 msec vectors in left anterior hemiblock (inferiorly and to the right) is different from that of left posterior hemiblock (superiorly and to the left) and that of left bundle branch block (inferiorly and to the left). Early left ventricular depolarization appears to be a function of conduction through the "main" left bundle as well as of the anterior and posterior divisions. The study of postsurgical hemiblock corroborated previous assumptions made from deductive clinical electrocardiography. Surgically induced left anterior hemiblock obscured the signs of right ventricular hypertrophy when associated with complete right bundle branch block in cases of congenital heart disease. However, the diagnosis of right ventricular hypertrophy could still be made when isolated left anterior hemiblock (that is, without complete right bundle branch block) appeared after mitral valve replacement.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine