Tags: Anatomical Structure.
The left margin of heart (or obtuse margin) is shorter than the right border of heart full and rounded: it is formed mainly by the left ventricle but to a slight extent above by the left atrium. It extends from a point in the second left intercostal space about 2.5 mm. from the sternal margin obliquely downward with a convexity to the left to the apex of the heart.
