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Circumflex artery (LCx)

The circumflex artery (LCx) is one of the two terminal branches of the left coronary artery (LCA), arising at its bifurcation with the left anterior descending artery (LAD). It courses laterally and posteriorly within the atrioventricular (coronary) groove, curving around the left border of the heart toward the posterior surface.

The LCx primarily supplies the lateral and posterior walls of the left ventricle and the left atrium. Its contribution to coronary circulation depends on dominance:

  • In left-dominant hearts (~15%), the LCx gives rise to the posterior descending artery (PDA), supplying most of the inferior wall and posterior septum.

  • In right-dominant hearts (~70%), PDA arises from the RCA, with LCx supplying lateral LV.

  • In co-dominant circulation (~15%), both RCA and LCx contribute to posterior supply.

The LCx gives rise to obtuse marginal (OM) branches (supplying lateral LV wall) and smaller atrial branches. Variation in size and dominance makes LCx evaluation critical in ischemic heart disease, bypass surgery, and stenting.

Synonyms

  • LCx artery

  • Left circumflex artery

  • Ramus circumflexus

Function

  • Supplies blood to the left atrium

  • Perfuses the lateral and posterior walls of the left ventricle

  • In left-dominant circulation, supplies the posterior interventricular septum and inferior LV wall

  • Provides branches that support myocardial conduction system perfusion (via AV nodal artery in left dominance)

Branches

  • Obtuse marginal arteries (OM1, OM2, etc.) → supply lateral wall of LV

  • Atrial branches → supply left atrium

  • Left posterolateral branches → supply posterior LV wall

  • Posterior descending artery (PDA) → in left-dominant circulation

MRI Appearance

T1-weighted images (non-contrast):

  • Flowing blood appears as a signal void (black lumen)

  • Vessel wall is hypointense, epicardial fat provides natural contrast

T2-weighted images:

  • Lumen remains a signal void

  • Perivascular edema, myocarditis, or infarction in LCx territory appears hyperintense

STIR (Short Tau Inversion Recovery):

  • Suppresses fat signal, highlighting myocardial edema in LCx perfusion regions (lateral and posterior LV walls)

  • Infarcted or inflamed myocardium shows bright hyperintensity

T1 Post-Contrast (Gadolinium-enhanced):

  • LCx lumen enhances homogeneously

  • Myocardial late gadolinium enhancement (LGE) demonstrates scar or infarction in LCx territory

MRI Non-Contrast Cardiac-Gated 3D Coronary MRA:

  • ECG-gated, respiratory-navigated 3D acquisitions show the LCx as a bright continuous vascular lumen

  • Delineates origin, atrioventricular groove course, obtuse marginals, and dominance pattern

  • Useful for congenital anomalies, anomalous origin, and pre-surgical mapping without contrast

CT Appearance

Non-contrast CT (Calcium Scoring):

  • Calcified plaques in LCx are hyperdense; quantified for coronary calcium score

  • Provides risk stratification but not lumen visualization

CT Coronary Angiography (CCTA):

  • Gold-standard non-invasive modality for LCx imaging

  • Demonstrates origin, course in AV groove, OM branches, left posterolaterals, and PDA (if left dominant)

  • Identifies stenosis, plaques (calcified and non-calcified), occlusion, aneurysm, and anomalous course

  • Multiplanar and 3D reconstructions guide PCI, CABG planning, and ischemia risk evaluation

CT images

Circumflex artery (LCx) anantomy CT axial image -img-00000-00000

CT images

Circumflex artery (LCx) anantomy CT axial image -img-00000-00000_00001

MRI images

Circumflex artery (LCx) MRI axial image 1

MRI images

Circumflex artery (LCx) MRI axial image