Embryological and morphological insights into diagnosing cardiac anatomy in heterotaxy syndrome

The aim of this study was to highlight the hypothesis that embryological development and morphological aspects necessitate a comprehensive analysis of all situses and a detailed description of each anomaly, rather than attempting to force the malformation into the rigid categories of heterotaxy syndrome (HS) - left or right isomerism. This hypothesis is supported by describing the anatomy of a complex patient with multiple laterality defects resulting in multiple cardiac and organ malformations.

The unique aspect of the presented patient's morphological diagnosis lies in the presence of a leftward heart loop with an unusual shape and direction, with the right ventricle (RV) positioned posterosuperior to the left ventricle (LV). This configuration suggests congenitally corrected transposition of the great arteries, although it deviates from the typical presentation. Additionally, there is an arrest in the development of other embryonic structures, including an atrioventricular septal defect (AVSD) with asymmetric ventricles, hypoplasia of the left-sided morphological RV, and malposition of the great arteries, with the aorta positioned anteriorly and to the right of the stenotic pulmonary artery. There is also another important inconsistency: the atrial situs is solitus within the context of HS, accompanied by left bronchial isomerism, polysplenia, interrupted inferior vena cava, and bilateral superior vena cavae.

In our patient's case, the segmental analysis revealed a rare morphological cardiac anatomy. Understanding both normal and pathological embryological cardiac development, and correlating it with the current morphological anatomy, was crucial in ensuring the correct diagnosis and treatment for our patient.