|  Thus
in summary, the Cx travels in the left atrio-ventricular (AIV) groove
between the left atrium and left ventricle, as it wraps around to the
back or posterior portion of the heart.
The
OM or obtuse marginal coronary arteries are given off in the proximal
or early course of the artery, while the postero-lateral coronary arteries
arise from the distal portion of the Cx.
In
85% of cases, the Cx is non-dominant, while the "dominant" RCA supplies
the PDA branch. In the other 15% of cases, a dominant Cx supplies the
PDA branch. 
|
The
obtuse marginal or OM branch serves as the boundary between the proximal
and distal portion of the Cx. Thus, the portion of the artery prior
to the origin of the OM is known as the proximal Cx, while
the segment just below the OM is the distal Cx. An example
of a dominant circumflex is shown on the left. Note that it supplies
the posterior descending coronary artery or PDA. When supplied by the
Cx, it is known as left PDA while it is called right PDA when it is
supplied by the right coronary artery.