Congenitally complete heart block with an interrupted Mönckeberg sling.

The conducting tissues are described in a case of congenitally corrected transposition. The patient was known to have suffered from congenital complete atrioventricular block. In the heart, both anterior and posterior nodes and bundles were found to coexist. The two bundles shared a common bifurcation. Neither of the two nodes connected with their respective bundles. The different morphology of the two sites of fibrous interruption may be explained by differences in embryonic development.