FIG 26.10 Heart with isomerism of the left atrial appendages and quasimirror image venous relationships (A–B) Bilateral tubular appendages have a narrow junction (red arrows) with the atrial vestibule (A) The superior caval vein is left-sided (B) A persistent right superior caval vein drained to the coronary sinus (not seen) The red star indicates the right pulmonary artery (C) Posteroinferior aspect demonstrating the left-sided superior and inferior caval veins and the right-sided persistent right superior caval vein (yellow arrow) draining to the left-sided coronary sinus (yellow dots) (D) The right ventricle is opened in clamshell fashion to show the common atrioventricular (AV) valve The apex of this heart was to the right, and there is right-hand topology FIG 26.11 Isomerism of the right atrial appendages with quasi-mirror image venous relationships The opened atriums exhibit pectinate muscles to the crux (A) The right and left pulmonary veins drain to the right-sided atrium in this heart with an atrioventricular septal defect and an atrial septal defect (B) The superior and inferior caval veins drain to the left-sided atrium Note the terminal crest (star) FIG 26.12 Bilateral appendages of right morphology (note the pectinate muscles extending to the crux on both sides), with the pulmonary veins draining through a central fibrous confluence This is anatomically anomalous FIG 26.13 Heart with all the pulmonary veins returning to the right-sided atrium, which has an appendage of right morphology In anatomic terms, this is totally anomalous pulmonary venous connection Note the absence of the coronary sinus Totally anomalous pulmonary venous connection, along with absence of the coronary sinus, is therefore the distinguishing atrial feature of hearts with isomeric right atrial appendages In contrast, an anomalous connection of the inferior caval vein usually draws attention to the potential presence of isomeric left atrial appendages In this setting, there is absence of the suprarenal segment of the inferior caval vein, with the abdominal segment of the caval vein continuing through the azygos venous system (Fig 26.14) to drain to either the right- or left-sided superior caval vein In patients with left isomerism, both accessory venous systems are strictly “hemiazygos,” since the hemiazygos vein is a morphologically left structure It is simpler, nonetheless, to describe communication via the azygos venous system to account for the right-sided or left-sided location of the anomalous venous channel Azygos continuation can be found in the setting of right isomerism but is very rare Although the suprarenal segment of the inferior caval vein is absent, a confluent suprahepatic venous channel can be found in up to one-third of the patients with isomeric left atrial appendages