Four anomalous hearts are described in which the great arteries arise in unusual fashion from their morphologically appropriate ventricles. This malformation, previously termed anatomically corrected transposition, is now termed anatomically corrected malposition. This is because, following the precedent of Van Praagh and his associates, we now reserve the term 'transposition' to describe the situation in which both great arteries arise from separate morphologically inappropriate ventricles. All the hearts examined exhibited atrioventricular concordance, I with viscero-atrial situs inversus, and 3 with situs solitus. However, there were considerable variations in ventricular morphology between the cases. Thus, 2 cases exhibited atresia of the right atrioventricular valve, and in the remaining 2 cases right and levt ventricular sinuses were both identified. Two of the cases also had pulmonary atresia, and coronary artery anomalies were present in all 4. The cases emphasize the fact that the term anatomically corrected malposition describes not a discrete anomaly but only a ventriculo-arterial relation, which is one of ventriculo-arterial concordance. Doubt has previously been cast upon the existence of this as an anatomical entity. It is concluded that the relation does indeed exist, and furthermore can coexist with all varieties of atrioventricular relations. It is suggested that the differing atrioventricular relations can be distinguished by usage of the terms 'concordant' or 'discordant' anatomically corrected malposition. Finally, it is emphasized that it is necessary to distinguish this anomaly, which in most cases presents with left-sided anterior aorta, from the left-sided anterior aorta more frequently encountered in classically corrected transposition'.

Three cases of congenitally complete heart block are described of hearts in which other minor congenital malformations were not in themselves severe enough to disrupt the atrioventricular conduction system. The cases fitted well into the categorization of complete heart block suggested by Lev. Two exhibited lack of communication between the atrial and conducting tissues, the other had discontinuity of the penetrating atrioventricular bundle. In an attempt to explain why this discontinuity between different segments of the conducting tissues occurs, we re-examined several series of graded human embryos. This investigation suggested that the anulus fibrosus in the normal heart is derived from sulcus tissue of the atrioventricular junction, the endocardial atrioventricular cushions playing a minor role in the separation of atria from ventricles. The relationships between the sulcus tissues and the different components of the atrioventricular junctional area are discussed in terms of an explanation both for the existence of different types of congenitally complete heart block and for persistence of Mahaim (nodo-ventricular and nodo-fascicular) fibers.

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