Interior aspect
Inside the LVS, the presence of the great cardiac vein is almost inevitable. However, LVS may come without a coronary sinus tributary when the short distance between bifurcation to septal perforator excludes vessels from the defined LVS area. In anatomical terminology, great cardiac vein begins at the heart’s apex and ascends along the anterior longitudinal groove to the base of the heart, while in cardiology and radiology, the initial segment from the apex of the left ventricle to the LVS is named the anterior interventricular vein[7]. In definition, the anterior interventricular vein originates at the lower or middle third of the anterior interventricular groove, follows the groove adjacent to the left anterior descending artery, and angulates laterally toward the heart’s base to form the great cardiac vein [2]. The coronary venous system lying in the LVS region is sunken in the epicardial adipose tissue, and distance to the left ventricular surface may be wary (Figure 2c). This distance might impact ventricular potential amplitude recorded from the great cardiac vein if the epicardial adipose tissue is significantly thick. Mostly, the venous system intersects coronary vessels deeply [Figure 4A], while in ¼ of the specimens, it does so superficially. The relationships between the great cardiac vein – anterior interventricular vein and the coronary arteries vary between patients [6]. The point of transition between the anterior interventricular vein and the great cardiac vein lies inside the LVS and arguably a significant source of epicardial idiopathic ventricular arrhythmias [9].The coronary venous system plays an essential role in the LVS division into the superior and inferior aspects. The superior aspect of the LVS is named an inaccessible area; nevertheless, it is recognizable also as the triangle of Brocq and Mouchet [18]. The difference in terminology is that the featured LVS base starts from the first dominant septal perforator while trigon of Brocq and Mouchet when the anterior interventricular vein crosses the anterior interventricular groove. Brocq and Mouchet trigon have five main variations dependent on vessel crossings and relations in heart groves [18]. The inaccessible area is almost triangular, closed at the bottom by the venous system. In some LVS, the superior aspect may dominate in size over the accessible area (figure 1A, B). The inaccessible area contents include the presence of proximal branches from coronary vessels, small veins, and a thick layer of epicardial adipose tissue covered by LAA and pulmonary trunk. Between the anterior interventricular vein / great cardiac vein line and arcuate line, the accessible part of the LVS is present. Mostly irregular in shape with the continuation of coronary vessels originated from the inaccessible area and anterior coronary veins draining into the coronary venous system. The density of coronary branches is significantly lower, as well as epicardial adipose tissue. Often uncovered by the LAA with epicardial approach possibility.