Ventricular Topology in Congenital Heart Defects Associated with Heterotaxy: Can We Find Patterns Reflecting the Syndrome-Specific Tendency for Visceral Symmetry?

Heterotaxy syndrome is characterized by a tendency for bilaterally symmetric arrangement (isomerism) of inner organs. It is frequently associated with complex congenital heart defects (CHDs). In "heterotaxic" hearts, the tendency for isomerism is confined to the atria. The ventricular segment always shows asymmetric arrangements (D-hand or L-hand topology). This study aimed to determine the statistical distribution of ventricular topology among patients with CHDs associated with heterotaxy and to identify possible associations between ventricular topology and cardiovascular disorders and survival. It is a retrospective cross-sectional study on 192 patients treated at a single center between 2000 and 2023. Our cohort had 115 patients of left atrial isomerism (LAI) and 77 of right atrial isomerism (RAI). The whole cohort (n = 192) showed a bias towards ventricular D-hand topology (67%), which was statistically significant in LAI (74%). In contrast, RAI showed an almost equal distribution (57% D-hand, 43% L-hand). No significant associations were found between ventricular topology and major CHDs or mortality. Significant associations were observed between ventricular topology and cardiac apex position, direction of p-wave axis, and aortic arch sidedness. We conclude that, in the setting of heterotaxy, especially RAI, ventricular topology and aortic arch sidedness both behave as binary anatomical variables showing a tendency for randomized occurrence. This tendency for statistically symmetric distribution is interpreted as reflecting the syndrome-specific tendency for bilateral symmetry.