Version May 2024
| Right atrial isomerism | Left atrial isomerism | |
| Situs | ||
| Bilateral right-sidedness | Bilateral left-sidedness | |
| Abdomen | ||
| Spleen | No spleen (asplenia) | More than one spleen (polysplenia) |
| Liver | Symmetrical and horizontal | Bilobed, may be symmetrical, but more often to one side |
| Stomach | Near midline (right or left) | Usually right-sided |
| Heart and vessels | ||
| Cardiac position | Mesocardia common; can be on either side | Mesocardia rare; generally on either side |
| Systemic venous vessels | ||
| Superior vena cava | Bilateral: One to each atrium | May be bilateral: One to each atrium (can be via coronary sinus) |
| Coronary sinus | Absent | Generally present |
| Inferior vena cava | Present; can connect to either atria but is always on the same side as DAo | Usually interrupted with azygos continuation |
| Atria | ||
| General | Bilateral right atria | Bilateral left atria |
| Sinoatrial node | Bilateral with one dominant (usually inferior P wave axis) | Absent coronary sinus rhythm |
| Septum | Usually large primum and secundum ASD | Highly variable, from intact septum to common atrium |
| Atrioventricular valves | Single (AVSD type) or atresia of one | Two valves or AVSD type |
| Pulmonary veins | Generally extracardiac TAPVR | Directly to atria |
| Ventricles | ||
| Position | Inverted | D-looping |
| Ventricular septal defect type | Canal type (inlet) | Membranous or canal type |
| Great arteries | ||
| Position | Malposed (approximately 95%); DORV (approximately 5%) | Generally normal, occasional DORV and rare malposition |
| Pulmonary outflow obstruction | Severe pulmonary stenosis or atresia in >90% | Pulmonic stenosis is unusual |
| Left-sided obstruction | Rare | Common (MS, AS, CoA) |
| Other thoracic organs | ||
| Bronchi | Both are eparterial | Both are hyparterial |
| Lungs | Bilateral trilobed | Bilateral bilobed |
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