Clarifying anatomical complexity: Diagnosing heterotaxy syndrome in the fetus

Heterotaxy syndrome, a disorder that involves abnormal lateralization of the abdominal viscera, thoracic organs and cardiac atria, remains one of the most challenging lesions in the field of pediatric cardiology both from a diagnostic and surgical strategy standpoint. Despite improved techniques, heterotaxy syndrome continues to be associated with high morbidity and mortality. Generally, heterotaxy syndrome can be categorized into two subtypes. Right atrial isomerism is associated with single ventricle, atrioventricular canal defect, pulmonary outflow obstruction, conotruncal abnormalities, bilateral superior vena cavae and total anomalous pulmonary venous connection. Left atrial isomerism can have similar intracardiac findings but also includes interruption of the inferior vena cava, ipsilateral pulmonary venous connection and complete heart block. Non-cardiac abnormalities such as splenic dysfunction, intestinal malrotation, and biliary atresia can be seen in both subtypes. Prenatal diagnosis of heterotaxy syndrome requires thorough knowledge of the typical findings as well as a systematic approach to the segmental anatomy. Accurate prenatal diagnosis is helpful to appropriately counsel families and for the perioperative management of these patients. However, the impact of prenatal diagnosis on long-term outcome remains to be seen.