Familial congenital bundle branch system disease

The occurrence of congenital conduction disturbances in three siblings is presented. The first child had complete heart block at age 2 years and died at age 10 with ventricular fibrillation. The second sibling at age 15 years had right bundle branch block with left axis deviation and complete heart block at age 17. The third sibling at age 17 years had normal atrioventricular (A-V) conduction but prolonged intraventricular conduction time with incomplete right bundle branch block. Serial section study of the conduction system of the first sibling showed atrophy of the branching portion of the A-V bundle with almost complete absence of the left bundle branch and absence of the beginning of the right bundle branch. The second and third parts of the right bundle branch were intact. The anatomic data in the first case and the electrocardiographic data in all three cases suggest a familial congenital disease of the bundle branches.