This is an angiogram of a left coronary artery (LCA).  The circumflex artery, labelled CX, is dominant, meaning that it connects to the posterior descending artery and perfuses the posterior and inferior walls of the left ventricle.  Approximately 15-18% of the population has a dominant circumflex artery.  In about 80-85% of people, the right coronary artery (RCA), perfuses the inferior wall.