Objective: The fulcrum as a structure that has been described in human and mammalian hearts as ossa cordis; the aim of the present study is to demonstrate its existence in the fetal heart, using ultrasonographic techniques and macro and microscopic anatomy. Methods: Ultrasound images of the fulcrum were obtained in 240 normal fetal hearts between 26 and 37 weeks of gestation, using 2D ultrasound and TM mode in 201 cases. Speckle tracking alone was used in 58 cases to demonstrate the triphasic movements of the fulcrum. Macroscopic anatomical dissection and histological study were performed in eight fetal hearts from spontaneous abortions (20-22 weeks). Results: We demonstrated the presence of the cardiac fulcrum, on which myocardial tissue fibers are inserted as a tendon constituting a unit that serves as a pivot for cardiac contraction, resulting in a three-phase displacement of the fulcrum. Values and displacement curves were obtained as a function of gestational age, adjusted to the cubic regression model and bivariate correlation (p < 0.001). Macroscopic anatomy and histology results are presented. Conclusions: The present study demonstrated the myocardial fulcrum in the fetal heart, a structure composed of myxo-chondroid tissue, being able to be visualized by ultrasound. This structure that acts as a lever has a mixed displacement that can be quantified in terms of vertical, rotational, angular and deformation displacement. Its existence could be proved in macro and histological dissections demonstrating the anchorage of cardiac fibers at the ends of this structure.
