The relationships between the great cardiac vein and the coronary arteries within the LVS region vary between individuals [19,34,35]. There are four main aspects of the GCV course relative to the left coronary branches: (1) side of initial course relative to the left anterior interventricular artery, (2) superficial or deep crossing of the left anterior interventricular artery from a right side initial course, (3) proximal or distal crossing of the circumflex branch of the left coronary artery and (4) superficial or deep crossing of the circumflex branch of the left coronary artery. From these aspects, Bales et al. present 12 theoretical relationship combinations [36]. Studies report that the great cardiac vein is found either on the right or left side of its related artery in the interventricular groove, more often crossing the left anterior interventricular artery superficially. The relationships of the great cardiac vein to the circumflex artery are predominantly proximal (close relative to the apex of the LVS). Approximately 60% of the great cardiac veins crossed superficially to the circumflex artery in most studies [22,37]. It is interesting to note that when the great cardiac vein crossed the left anterior interventricular artery superficially, it more often crossed the circumflex artery superficially and that when the great cardiac vein crossed the left anterior interventricular deeply, it more often crossed the circumflex artery deeply. Figure 2B presents the rarest possible variation with deep crossing to left anterior interventricular and circumflex artery in the distal relation.