Significance of complete left bundle branch block with left axis deviation.

Left axis deviation occurring with complete left bundle branch block may represent divisional left anterior hemiblock in addition to predivisional left bundle branch block. To study this possibility the electrocardiograms of 84 patients with left bundle branch block, in whom previous electrocardiograms were available, were reviewed. There were 49 patients with left bundle branch block and left axis deviation (greater than ? 30 °) (group A) and 35 patients with left bundle branch block and normal frontal axis (group B). The mean age, QRS interval and time Interval between the first and the qualifying electrocardiogram were similar in both groups. The $\text{male}\text{female}$ ratio was significantly different (P < 0.05) and was 26:23 in group A and 9:26 in group B. In group A 24 of 49 patients had a prior electrocardiogram without bundle branch block; in 10 of 24 the pattern indicated hemiblock. Among patients in group B 25 of 35 had a previous electrocardiogram without bundle branch block; a hemiblock pattern was present in only 3 of the 25 (P < 0.05). Seven of 49 patients in group A had a previous electrocardiogram showing left bundle branch block alone whereas 9 of 35 patients in group B had a previous pattern of left bundle branch block. In these seven patients in group A left axis deviation subsequently developed but did not occur in the nine patients In group B. It is concluded that the majority of patients with a left bundle branch block pattern and left axis deviation have left anterior hemiblock separately (either before or after the appearance of left bundle branch block).