Left superior vena cava with atrial displacement.

Two cadavers were dissected showing persistence of left-sided superior vena cava with atrial displacement and inversion of the venous drainage from the body wall (azygos system of veins). The presence of atrial displacement in relation to a persistent left superior vena cava observed in this study lends support to the view that haemodynamic factors influence the morphogenesis and development of the heart. The development of an asymmetrical venous pattern from a symmetrical venous drainage may be influenced by the same factors which influence the arterial end of the primitive heart tube.