What Should You Look For?
Right atrial isomerism (RAI), also known as asplenia syndrome, is a type of heterotaxy characterized by right-sided symmetry.
Unlike left atrial isomerism, which often shows interrupted IVC and parallel abdominal vessels, RAI typically presents with more severe cardiac malformations.
๐ Key Abdominal Clues
In right atrial isomerism:
- The IVC is usually present and not interrupted
- The abdominal vessels do not typically show parallel alignment
- The liver may appear midline
- The stomach position can be abnormal
- Spleen may be absent (difficult to confirm prenatally)
Abnormal situs should always raise suspicion.
โค๏ธ Cardiac Features to Watch
RAI is often associated with:
- Complete atrioventricular septal defect (AVSD)
- Pulmonary outflow obstruction
- Total anomalous pulmonary venous return (TAPVR)
- Abnormal 3VT configuration
- Severe conotruncal anomalies
Compared to left atrial isomerism,
cardiac involvement is often more complex and severe.
๐ง Clinical Insight
If you suspect heterotaxy:
โ Carefully evaluate abdominal situs
โ Assess IVC continuity
โ Examine pulmonary venous return
โ Review 3VT view pattern
โ Look for AV valve morphology
Heterotaxy is a systemic laterality disorder,
not just a heart anomaly.
๐ Left vs Right Atrial Isomerism โ Quick Comparison
| Feature | Left Atrial Isomerism | Right Atrial Isomerism |
| IVC | Interrupted (azygos continuation) | Usually present |
| Abdominal vessels | Parallel pattern common | Usually normal alignment |
| Spleen | Multiple (polysplenia) | Absent (asplenia) |
| Cardiac severity | Variable | Often severe |
| AVSD | Possible | Very common |
