Coronary artery "dominance" is defined in terms of which coronary artery supplies the posterior descending artery (PDA, also known as the "inferior interventricular artery"), and the posterior left ventricular branches. The PDA is the artery that extends along the inferior interventricular groove, from the crux of the heart toward the apex.

Most persons (approx 89.1%) have a "right-dominant" system, which means that the right coronary supplies these arteries.  8.4% of persons have a "left-dominant" system, which means that the left circumflex supplies these arteries (as in our case).

Other variations of dominance exist, such as a "co-dominant" circulation (2.5%) in which the right coronary supplies the PDA and the left circumflex supplies the posterior left ventricle through a left posterolateral branch.

Of note, even with right "dominance," the left coronary artery supplies the majority of the left ventricle.