RESUMO
Anatomical structure of right ventricular septomarginal trabecula (SMT) was studied at micro-macroscopical level in 99 preparations of human fetal heart formed without malformations and minor abnormalities, obtained at 1728 weeks of development. SMT was found to be a constant cardiac structure consisting of the body and two branches: anterior and posterior. Body of SMT is a myocardial vallum, unseparable from the interventricular septum, the long axis of which is always located along the conventional line connecting septal insertion of supraventricular crest and right ventricular apex. Posterior margin of SMT body was distinct in 75% of cases and smoothened in 21.9%. Base of the SMT was solid in 46.3% and split into secondary trabeculae in 52.6% of cases. Narrow and wide forms of SMT body were considered as its extreme anatomical variants. It is suggested to distinguish two anatomical types of SMT: a complete type, in which SMT was represented by a complex consisting of body in the form of muscular vallum and both branches, and an incomplete one, in which one of the branches was absent. Human fetal heart SMT is characterized by a variability, which is manifested by certain combinations of anatomic variants of SMT base form, its posterior margin, and the presence, shape and mutual location of its branches.
