Left Circumflex Artery

ramus circumflexus arteriae coronariae sinistrae

The left circumflex artery arises from the left main coronary artery and runs in the left atrioventricular groove, giving obtuse marginal branches that supply the lateral and posterolateral left ventricular wall. In left-dominant coronary anatomy (10-15% of individuals) the LCx gives rise to the posterior descending artery, supplying the inferior wall and AV node. The LCx is closely related to the mitral valve annulus in the left AV groove.

Region: Chest

Clinical Relevance

Clinical Notes

LCx occlusion causes lateral wall MI, producing ST changes in leads I, aVL, V5, and V6. Because the LCx territory is more posterior, lateral MI may be missed on standard 12-lead ECG and requires posterior leads (V7-V9). The LCx proximity to the mitral valve annulus means it can be injured during mitral valve surgery, causing a circumflex coronary artery injury and inferior lateral wall MI, a rare but catastrophic complication of mitral repair or replacement.

Pathology

Common Injuries & Conditions

Lateral Wall MI from LCx Occlusion

Thrombotic LCx occlusion produces lateral ST elevation MI that may have subtle or absent standard 12-lead changes, requiring posterior lead recording and urgent coronary angiography for diagnosis and primary PCI treatment.

LCx Injury in Mitral Surgery

The LCx runs in the left AV groove immediately posterior to the mitral annulus; sutures placed too deeply during mitral valve repair or replacement can kink or occlude the artery, causing intraoperative inferior lateral wall motion abnormality requiring emergent surgical revision.