regional_part_of Subdivision of conducting system of heart Conducting system of interventricular septum Conducting system of heart Left branch of atrioventricular bundle Crus sinistrum (fasciculi atrioventricularis) FMA:9487 Left bundle branch Subdivision of conducting system of heart which enters the septal myocardium of left ventricle and is continuous with the anterior, septal and posterior divisions of the left branch of the atrioventricular bundle. fma