Circumflex artery of heart

The circumflex artery (LCx) of heart is one of the two major branches of the left main coronary artery, the other being the left anterior descending (LAD) artery. It courses along the left atrioventricular groove (coronary sulcus), traveling posteriorly around the left side of the heart.

Anatomy and Course

The circumflex artery originates from the left main coronary artery and runs in the left atrioventricular sulcus, wrapping around the obtuse margin of the heart toward the posterior surface. Along its course, it gives off several important branches:

• Obtuse marginal (OM) branches These are the most clinically significant branches, supplying the lateral wall of the left ventricle. There may be one to three obtuse marginal arteries.

• Left atrial branches Small branches supplying the left atrium.

• Posterolateral branches In some individuals, the circumflex extends further to supply the posterolateral wall.

Dominance and Variability

The extent of the circumflex artery's territory depends on coronary dominance:

• In approximately 85% of individuals, the heart is right-dominant, meaning the posterior descending artery (PDA) arises from the right coronary artery (RCA). In this pattern, the LCx is relatively smaller and supplies primarily the lateral wall of the left ventricle.

• In approximately 8-10% of individuals, the heart is left-dominant, and the circumflex artery gives rise to the PDA, supplying the inferior wall and posterior interventricular septum as well.

• In roughly 5-7%, the circulation is co-dominant, with contributions from both the RCA and LCx.

Clinical Significance

• Occlusion of the circumflex artery typically causes lateral wall myocardial infarction, which may manifest with ST-segment changes in leads I, aVL, V5, and V6 on electrocardiography.

• In left-dominant circulation, LCx occlusion can cause inferior MI as well, mimicking RCA occlusion.

• The circumflex territory is sometimes called an electrocardiographic "silent zone" because lateral wall ischemia may produce subtle or absent ST changes, making diagnosis more challenging.

• The circumflex artery is a common target for percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG), where it is typically grafted with a saphenous vein graft or, less commonly, a radial artery graft.

Relationship to Surrounding Structures

The circumflex artery runs in close proximity to the mitral valve annulus, which is clinically relevant during mitral valve surgery, as the artery can be inadvertently injured or ligated during annuloplasty or valve replacement procedures.