ISOLATED CONGENITALLY COMPLETE HEART-BLOCK ATTRIBUTABLE TO COMBINED NODOVENTRICULAR AND INTRAVENTRICULAR DISCONTINUITY

Intraventricular together with atrial-axis and nodoventricular discont inuity, in which various parts of the conduction system are replaced b y fibrous or fatty tissue, constitute the three major pathological cat egories of isolated congenitally complete heart block. Intraventricula r discontinuity is distinctly rare, with only two previous cases repor ted in the literature, one of which was associated with a familial his tory of heart block. The cardiac conduction systems of two cases of is olated congenitally complete heart block were serially sectioned and a nalyzed histopathologically. The findings were correlated with the cli nical features, in particular, the family histories and maternal serum anti-Re antibodies. Both cases, a 9-day-old neonate and an 8-year-old schoolgirl, showed a combination of nodoventricular and intraventricu lar discontinuity with absence of the atrioventricular penetrating bun dle, the entire right, and the proximal portion of the left bundle bra nch. The branching bundle was absent in the first case and replaced by fatty tissue in the second. In contrast to the commoner atrial-axis d iscontinuity in which the atrioventricular node itself is usually repl aced by fibrous or fatty tissue with variable involvement distally, th e sinus node, and in particular, the atrioventricular node were normal in both of our cases. There was no family history in either case, whe reas tests for the maternal serum anti-Re antibody were positive in th e first but negative in the second case. Intraventricular discontinuit y as a cause of isolated congenitally complete heart block is very rar e. In our cases, it coexisted with nodoventricular discontinuity. It c an be sporadic, familial, or associated with positive maternal serum a nti-Re antibodies. Copyright (C) 1998 by W.B. Saunders Company.