In some cases, the mitral margin’s superior aspect may be covered by the pulmonary trunk or left main pulmonary artery [15]. The first (or sometimes the second) obtuse marginal branch originates from the left circumflex coronary artery entering into the LVS from the mitral margin aspect. The great cardiac vein enters over a mitral margin of the LVS. It crosses the left circumflex coronary artery and then runs into the posterior aspect of the atrioventricular groove. Several spatial relationships between the great cardiac vein and the left circumflex coronary artery may be found, with the vein located over the artery being the most common [19]. The left phrenic nerve trespassing epicardially over the left atrial appendage and then directing to the left dome of the diaphragm may cross the mitral margin [27–30].