Safety of Retrograde Flow of Internal Mammary Vein: Cadaveric Study and Anatomical Evidence.

 The IMV valve was present in 55% of our subjects and located concentrically above the second ICS level. It is highly unlikely that the retrograde flow was disturbed because the retrograde anastomosis level was below the second ICS. Furthermore, the bifurcation, intercostal, and crossing veins across the xiphoid process enabled valve-less detour flow. Thus, retrograde IMV flow is considered safe.