Abstract
The conduction system was histologically examined in 14 cases of right bundle branch block associated with left axis deviation. Twelve cases showed marked degeneration of the central fibrous body, degeneration and interruption (fibrosis, calcification and fatty changes) of terminal portion of the bundle of His, proximal portions of the both bundle branches and intermediary portions of the right bundle branch and the anterior radiation of the left bundle branch. Some increase of acid mucopolysaccharide was frequently found in the blocked lesions, which suggested an accumulation of mechanical strain as a pathogenesis of the injuries in the conduction system. Two cases showed extensive myocardial infarction which gave total necrosis on the peripheral part of bilateral bundle branches. Histological basis of RBBB with LAD was concluded as a kind of bilateral bundle branch block.
