2:1 left bundle branch block in acute bacterial endocarditis with septal abscess.

This report presents an unusual type of conduction disturbance of the left bundle branch which appeared in a patient with acute bacterial endocarditis of the aortic valve in which the septum was also invaded. This is the first case found in which the partial left bundle branch block (LBBB) was of acute inflammatory origin. Other previously reported cases of this functional delay of the left branch were secondary to arteriosclerotic heart disease.