A clinicopathological study on 25 cases of complete left bundle branch block.

A total of 25 cases (12 men, 13 women) of complete left bundle branch block (LBBB) were found among 1,400 consecutive autopsy in the aged. Their ages ranged from 70 to 86 years (average 78.9). ECG was analyzed as for the occurrence of LBBB and myocardial infarction (MI). Pathological examinations included observations of the conduction system by serial sections. They were divided into group A with MI and group B without MI. Duration of LBBB was 1 to 3 days in 4 cases, more than 1 month in 7, and more than 1 year in 14. From the temporal sequence of LBBB and MI in group A, cases were classified into (1) MI preceding LBBB in 5, (2) both coexistent in 5, and (3) LBBB preceding MI in 1. There were 8 cases of normal electrical axis, 17 left axis deviation, 7 first degree A-V block, and 2 atrial fibrillation. Various heart diseases were underlying in 21 cases, including hypertension, MI, mitral and aortic regurgitation, and primary myocardial disease, and there were 4 cases with no cardiac diseases. Cause of death was cardiac in 12; MI, congestive heart failure, and sudden death. Heart weight was 410 Gm on the average (240 to 550 Gm). MI was found in 11, with stenotic index of 12/15, while it was 9/15 in group B. Lesions of the conduction system were slight to moderate (1.5 to 2.4) except left bundle branch, which showed marked changes in posterior (4.9) and anterior (4.8) fascicles. Site of interruption of the left bundle branch was the junction between the branching portion of the A-V bundle and the left bundle branch (Junctional type) in 17, and peripheral portion of the left bundle branch about 10 mm or more below the junction in 8 (Peripheral type). In conclusion, 2/3 of cases of LBBB belonged to the junctional type and most of them were not related to MI, but to the lesions caused by mechanical injuries at the septal summit. One third of the cases were as peripheral type, which was mainly related to the various types of lesions including septal ischemia (necrosis and fibrosis).