Access to the LVS is required when the ventricular arrhythmia source is localized in this particular area. The coronary venous system plays an essential role in the LVS division into the superior and inferior aspects. The superior aspect of the LVS, because of the dense vasculature in which damage may be life-threatening, is defined as an inaccessible area. It is also recognizable as the triangle of Brocq and Mouchet [63–67]. The difference may be found in both the terminology and boundaries of both triangles, where the first dominant septal perforator marks the LVS base.