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It is becoming increasingly apparent that congenital heart block is not so rare as has been thought. As with many other supposedly rare conditions, increasing knowledge and more definite criteria of diagnosis have made physicians more alert to its occurrence. The case to be reported is the third case of complete heart block of congenital origin to be studied by serial sections through the conduction system. The two cases previously studied were reported by Yater 1 and by Yater, Lyon and McNabb. 2 The only other case of congenital heart block studied in a similar manner was one of partial (2:1) block reported by Wilson and Grant. 3 The criteria which have been adopted for the diagnosis of congenital heart block are that (1) the auriculoventricular dissociation must be proved by graphic methods in a relatively young individual, (2) the bradycardiahave been noted at a fairly early age, aage,
Yater et al. (Sat,) studied this question.