Abstract
Heterotaxy is defined as an abnormality where the internal thoraco-abdominal organs demonstrate an abnormal arrangement across the left-right axis of the body characterized by a wide variety of very complex cardiac and extracardiac malformations. Right isomerism is associated with atrioventricular septal defect, conotruncal anomalies, pulmonary stenosis or atresia, and frequent anomalous systemic and pulmonary venous connections. In contrast, cardiac anomalies in patients with left isomerism include bilateral superior vena cava, interruption of the inferior vena cava with azygos continuation, ventricular septal defect, ostium primum defect, and morphologic left ventricular outflow obstruction. Not all patients with left isomerism have cardiac anomalies, and in many patients the cardiac anomalies are not complex. The cellular and molecular mechanisms of the left-right asymmetry have been extensively investigated in the past decade. Recent studies have revealed that rotational movement of the cilia generated an external liquid flow called nodal flow, which determined left-right asymmetric gene expression. Surgical outcomes in heterotaxy patients are improving in the current era. Significant atrioventricular valve regurgitation and obstructed total anomalous pulmonary venous return remain risk factors for the right atrial isomerism. Children with asplenia syndrome who survived the first month of life are at greater risk of dying from sepsis than from the heart disease. This article reviews the current advances in knowledge of the pathogenesis of heterotaxy, as well as diagnosis, physiologic features, and complications.
