Lack of connection between the atria and the peripheral conduction system in a case of corrected transposition with congenital atrioventricular block.

This is the first documented histologic study of the heart of a patient with corrected transposition of the great vessels and congenital atrioventricular (A-V) block with no connection between the atria and an anterior type of peripheral conduction system. Musculature in the superior (anterior) walls of both atria was absent, as was the anterior A-V node. The peripheral conduction system began with the bundle of His. In place of the absent atrial musculature, fibrosis and calcification were present. The relation of laboratory evidence of connective tissue dyscrasia in the mother to the congenital A-V block in the child is discussed.