atrial septum, a curved configuration of the ventricular septum, and unusual arterial relationships for the given pathology (see Figs 49.19 and 49.20) The ventricular inlets typically adopt a superoinferior relationship, with the apical components showing the most unusual relationships In extreme forms, the ventricular apices are displaced to the opposite side, and show a reversed sideby-side relationship This can occur with any known combination of connections of the cardiac segments Twisting is usually in such a direction to place the right ventricular inlet anterior and superior to the left ventricular inlet In congenitally corrected transposition with usual atrial arrangement, for example, and as shown in Fig 49.15, the morphologically left ventricle is usually a right-sided structure, while the aortic valve most frequently is located anteriorly and to the left The ventricular mass in the presence of the criss-cross malformation is twisted counterclockwise in such a way that the morphologically right ventricular inlet achieves a rightward and supero-anterior position relative to the left ventricular inlet (see Fig 49.19) The aortic valve is positioned anteriorly and can be rightsided In the presence of usual atrial arrangement, of course, a right-sided and anterior aorta arising from a right-sided morphologically right ventricle is more typically found with the segmental combinations of “simple” transposition (see Chapter 37) Nonetheless, twisting can also occur with the connections of the segments that normally produce the usual variant of transposition The ventricular mass is twisted clockwise, giving the spurious impression of congenitally corrected transposition (see Figs 49.14 and 49.20) Once the investigator is aware of the possibility, both the abnormal relationships and the true segmental connections are readily demonstrated by current techniques for imaging (see Fig 49.18) The key is first to analyze the connections between the cardiac segments, and only then to take note of the relations of the ventricles and arterial trunks The secret is not to be surprised when the relationships observed are not as anticipated for the demonstrated segmental connections FIG 49.18 Magnetic resonance images from a patient with concordant atrioventricular connections, with the atriums (RA, LA) connected to their appropriate ventricles (RV, LV), and showing the crossing of the atrioventricular inlets (arrows) This is the essence of the so-called crisscross heart, the right-sided location of the morphologically left ventricle relative to the right ventricle giving the spurious impression of the discordant atrioventricular connections Compare with the reconstruction shown in Fig 49.14 FIG 49.19 Reconstructions made from computed tomographic datasets compare the arrangement usually found in congenitally corrected transposition, where the aorta and morphologically right ventricle are usually left-sided (upper panels), with the situation produced by twisting of the atrioventricular connections (lower panels) FIG 49.20 Reconstructions prepared from computed tomographic datasets compare the effect of twisting of the atrioventricular connections (lower panels) with the usual arrangement found in transposition with concordant atrioventricular connections (upper panels) In the typical situation of the criss-cross heart, irrespective of the combinations of atrioventricular and ventriculoarterial connections, the ventricular topology is as anticipated for the identified atrioventricular connections Thus, in the illustrated situation with concordant atrioventricular connections (see Fig 49.14), although the morphologically left ventricle is rightsided despite the usual atrial arrangement of the atrial chambers, the morphologically right ventricle will accept only the palmar surface of the right hand of the observer with the thumb, figuratively speaking, in the tricuspid valve In other words, there is retention of right-hand ventricular topology despite the rotation of the ventricular mass along its long axis In some very rare