Significance of complete right bundle-branch block with right axis deviation in absence of right ventricular hypertrophy.

Complete right bundle-branch block with right axis deviation was seen in nine patients who did not have right ventricular hypertrophy, pulmonary disease, or extensive lateral myocardial infarction. Four patients had chronic block and five had acute myocardial infarction. This pattern was attributed to a coexisting block in the right branch and in the inferior division of the left branch. It frequently alternated with other significant intraventricular conduction defects, namely, complete left bundle-branch block, complete right bundle-branch block, and complete right bundle-branch block with block in the superior division of the left branch. A type II Mobitz block, evolving from a prolonged, or normal, PR interval, appeared in eight patients. The latter was probably due to a simultaneous conduction disturbance in the right branch and in both divisions of the left branch (trifascicular bloch). All patients required intracardiac pacing. The prognosis was not good due to the extensive involvement of the conducting system.