Double superior venae cavae associated with aberrant subclavian artery--the atavistic and transitional nature of "proximal loss" aortic arch.

A case of double superior venae cavae (Bvc) associated with bilateral azygos veins (Baz), aberrant subclavian artery (Sa) and other rare variations is recorded in a two-year-old Chinese girl with an unknown cause of death. A review of the literature since 1844 indicates that there has been no reported case of a right Sa associated with Bvc + Baz. The primitive arrangement of the thoracic large vessels in this case (Bvc + Baz and CHim type of aortic branches) substantiates the atavistic nature of Sa. The proximal loss pattern (PLdp) of the aortic arch with its associated Bvc + Baz was a primitive transitional link between the vascular arrangement of the Mesozoic reptilian and that of mammals or avians. According to this concept, there should be an occurrence of the PLdp variation (i.e. Sa) in all the mammals and avians and an occurrence of the 1-, 2- or 6-branch type of PLdp in human beings or in other animals.