At 7 weeks of life, a connection develops between the left and right anterior cardinal veins. This forms the left brachiocephalic anastomosis (Ghandour et al. 2017). It leads to regression of the left anterior cardinal veins, thus allowing blood to flow from the left side of the body toward the right anterior cardinal vein (Ghandour et al. 2017). Caudally to this transverse anastomosis, near the proximal portion of the right anterior and right common cardinal veins, the superior vena cava (SVC) is derived. Cranially to the transverse anastomosis, the right brachiocephalic vein forms from the right anterior cardinal vein. During embryonic development, the cardinal veins are responsible for venous return and represent the primary drainage. The anterior cardinal veins drain the cephalic portion of the embryo, and the posterior cardinal veins drain the caudal portion. Merging of the anterior and posterior cardinal veins before the sinus venosus creates the short common cardinal veins.