Criss-Cross Atrioventricular Relationships Producing Paradoxical Atrioventricular Concordance or Discordance

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Abstract
Two cases are described in which the systemic and pulmonary blood streams cross at atrioventricular level. One was examined pathologically, the other was diagnosed at cardiac catheterization by angiography. Both possessed situs solitus, but in one heart the right atrium was connected to a morphologic right ventricle on the left, whereas in the other it was connected to a left-sided morphologic left ventricle. In both cases transposition of the great arteries was present. The cases have been interpreted as representing rotation of embryonic d- and l-bulboventricular loops following septation. In attempting to describe these heart difficulties in terminology were encountered which were partially overcome by combining the concepts of concordant and discordant atrioventricular relationships with those of transposition and malposition. However, to give an accurate interpretation of the hearts, it proved necessary to include a term indicating rotation of the bulboventricular loop following septation. Thus the hearts were described as situs solitus, discordant (d-rotated) loop with d-transposition, and situs solitus, concordant (l-rotated) loop with l-transposition.