The left coronary groove delineates the left boundary of LVS with the circumflex branch of the left coronary artery and the initial section of the great cardiac vein. In some cases, the circumflex branch of the left coronary artery is accompanying the conus vein, which trespasses under the trunk of the left coronary artery (Figure 2A, B) while almost inevitable is presence of left lateral cardiac nerve (Figure 4E) [28]. The length of the mitral margin is equal to the septal margin. This margin neighbors close to the left fibrous trigon, the mitral annulus (anterior mitral leaflet), left atrium, and inlet into the left atrial appendage (LAA) [6]. The LAA overlaps the mitral margin, most commonly covering around 80% of it. In some cases, the mitral margin's superior aspect may be covered by the pulmonary trunk or left main pulmonary artery [4]. The first or sometimes, the second obtuse marginal branch from the left coronary artery's circumflex branch enters into LVS from the mitral margin. The great cardiac vein directing the heart's base enters over a mitral margin of LVS into the left coronary groove. At this point, the great cardiac vein is more often superficial to the coronary arteries (61,2%) than in other parts of LVS [6]. The left phrenic nerve trespassing epicardially over LAA, directing to the left dome of the diaphragm, may cross the mitral margin [8].