A Clinicopathological Study on 25 Cases of Complete Left Bundle Branch Block

Abstract

Twenty-five cases (12 men, 13 women) of complete left bundle branch block (LBBB) occurred among 1400 autopies of elderly individuals. Their ages ranged from 70-86 yr (average 78.9 yr.). ECG was analyzed for presence of LBBB and myocardial infarction (MI). Microscopic study of the conduction system by serial sections was included. The cases were classified as group A with MI and group B without MI. Duration of LBBB was 1-3 days in 4 cases, more than 1 mo. in 7, and more than 1 yr. in 14. From the temporal sequence of LBBB and MI in group A, cases were classified into MI preceding LBBB in 5, both coexistent in 5, and LBBB preceding MI in 1. There were 8 cases of normal electrical axis on ECG, 17 of left axis deviation, 7 of 1st degree A-V [atrio-ventricular] block, and 2 of atrial fibrillation. Heart diseases underlying in 21 cases included hypertension, MI, mitral and aortic regurgitation, and primary myocardial disease, and 4 had no cardiac diseases. Death was due to cardiac causes in 12: MI, congestive heart failure, and sudden death. Heart weight averaged 410 g (240-550 g). MI occurred 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 those of the left bundle branch, which showed marked changes in posterior (4.9) and anterior (4.8) fasciculi. 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). Of the cases of LBBB, 2/3 were of the junctional type and most were related to lesions caused by mechanical injuries at the septal summit rather than to MI. Of all the cases, 1/3 were peripheral type, which was mainly related to various types of lesions, including septal ischemia (necrosis and fibrosis).