Abstract

BACKGROUND
Identification of atrial situs is the initial step in any segmental analysis and classification of congenital heart malformations. To elucidate the differences for both atria of the normal and congenitally malformed heart, we performed morphological studies on the human heart with or without abnormal laterality syndrome.
METHODS
Five normally formed human hearts, five hearts with right isomerism and five hearts with left isomerism were used in this study. The postero-superior walls of the atrial chambers were examined.
RESULTS
Although the division line of the ventral and dorsal compartments was not as conspicuous as was seen in the right atrium of rat embryo previously studied, this division line existed as a well-developed terminal crest and vestigial structure of the antero-lateral extension of the terminal crest. These structures were noted in the right atrial chambers of normal human hearts and in the bilateral atrial chambers of right isomerism. However, they were totally absent in the bilateral atrial chambers in hearts with left isomerism.
CONCLUSIONS
Our study showed that the right atrial chamber in the normally developed human heart has vestigial components of division between the ventral and dorsal compartment, and hearts with right isomerism and left isomerism have differential development of the ventral and the dorsal compartment.

• Keywords: Morphogenesis;Heart Atrium;Congenital Heart Defect;lsomerism