Heterotaxy Syndrome: An Embryologic Study

Abstract

Heterotaxy is a clinically and genetically heterogeneous disorder with two main settings - left or right isomerism. Important diagnostic pointers like viscerocardiac heterotaxy, complex cardiac malformations, anomalies of the inferior vena cava may provide the prenatal diagnosis. Special signs of heterotaxy were sonographically detected in 5 human foetuses. Following the termination of the pregnancy a detailed examination according to the guidelines of the sequential segmental approach was performed. The main findings include multiple failures in the formation of the heart resulting from the dysfunctional viscerocardiac arrangement. The discontinuity and malposition of the inferior vena cava as well as the duplication of the superior vena cava are based on disorders of the left-right determination of the paired primitive veins in early embryonic development. The malrotation and malfixation of the bowel seem to be induced by the abnormal process of the embryonic duodenal loop with subsequent malpositioning of the portal vein and the superior mesenteric vessels. We demonstrate the wide variety of cardiac and extracardiac congenital malformations with considerable overlap in left and right isomerism. As a consequence, the differentiation between left or right isomerism may be sometimes difficult. Highly skilled sonographers and radiologists should be familiar with the corresponding embryonic development, which is essential for understanding the complex malformation pattern. Complete evaluation of each individual case is mandatory for adequate parental counselling with regard to further diagnostic steps and the planning of perinatal management.