Dominance of the coronary aerial system depends on which aery gives rise to the posterior interventricular branch (posterior descending aery). This branch supplies adjacent areas of both ventricles and posterior third of the IV septum.Right dominance: In this more conzmon type the posterior interventricular aery is a brute of . coronary aery. Left dominance: The circumflex aery, the continuation of left coronary provides the post. IV branchCodominance/balanced: Branches of both right and left coronary aery run in or near the sulcus.