FIG 49.13 Chest radiograph showing the characteristic appearances of left juxtaposition of the atrial appendages Note the sigmoid configuration of the right border of the cardiac silhouette and the bulge in the upper part of the left border (arrows) RA, Right atrium; SCV, superior caval vein Criss-Cross or Twisted Hearts, Superoinferior Ventricles, and Related Conditions The last group of hearts to be considered are those where the relationships of the cardiac chambers, or great arteries, are not as expected for the given segmental connections The significance of these malformations has diminished markedly since it has been appreciated that segmental connections cannot, and should not, be inferred from abnormal relationships of cardiac structures However, the abnormal relationships in themselves can still be a confusing feature The most commonly encountered is criss-crossing or, more precisely, twisting of the heart around the long axis of the heart, resulting in an unexpected relationship of the ventricles and arterial trunks (Fig 49.14).24,25 However, there are other arrangements that show an abnormal ventricular relationship without crossing or twisting of the ventricular inlets There are three mutually exclusive mechanisms that can produce abnormal ventricular relationships for the given segmental connections, namely, twisting, tilting, and rotation By twisting, we mean a spiral relationship of the atriums and ventricles in which the cardiac chambers and arterial trunks are aligned and arranged as if the heart were twisted clockwise, or anticlockwise, by a hand placed on the cardiac apex with the venous connections of the heart maintained in their normal positions (Fig 49.15) Tilting, in contrast, produces a superoinferior relationship of the ventricles, with the parallel axes of the ventricular inlet and atrioventricular junctions being preserved as if the apex of the heart were simply lifted by a hand placed on the apex (Fig 49.16) Rotation describes the much rarer condition, in which the cardiac chambers, arterial trunks and caval veins are all abnormally oriented within the thorax, as if the entire heart were rotated as a block around its long axis This produces the “topsy-turvy” arrangement (Fig 49.17) FIG 49.14 Reconstruction of the cavities from a computed tomographic dataset showing the unusual relationships produced by twisting of the ventricular mass in a patient having usual atrial arrangement, concordant atrioventricular connections, and discordant ventriculoarterial connections The morphologically right ventricle is positioned superiorly and leftward relative to the morphologically left ventricle, with the aorta in a leftward position The cylinders inserted in the atrioventricular junctions reveal the twisting that is the essence of the lesion