Circumflex artery !

The circumflex artery is a branch of the left coronary artery that curves around the left side of the heart to feed its side and back walls.

Official name: Circumflex artery of heart

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What it is

The branch of the left coronary artery that curves around the left side of the heart in the groove between atrium and ventricle.

What it does

Feeds the side and back of the left ventricle through its marginal branches.

Key facts

Origin: Left main coronary artery; runs in left coronary (atrioventricular) groove
Branches: Obtuse marginal (left marginal) branches; atrial branches; SA nodal artery in ~40%; PDA in left-dominant hearts (~10%)
Supplies: Lateral and posterior LV wall; left atrium

Relations

Course: From the left main coronary artery it turns left under the left auricle and runs in the left coronary (atrioventricular) groove round the obtuse margin toward the crux
Above: Left atrium and left auricle
Below: Base of the left ventricle, onto which its obtuse marginal branches descend
Superficial: Great cardiac vein, and then the coronary sinus, which run with it in the groove
Deep: Mitral valve annulus, which lies close to it inside the atrioventricular groove

How to find it

Hard to see at surgery: it runs in the left part of the coronary (atrioventricular) groove, under the left auricle and then around the back of the heart, covered by fat and by the great cardiac vein. Its obtuse marginal branches are reached on the lateral wall by lifting the heart up and to the right.

On imaging

On coronary angiography it is best seen in the right and left anterior oblique caudal views, with the obtuse marginal branches spreading over the lateral wall. CT coronary angiography shows its relation to the mitral annulus and the coronary sinus.

Common problems

Coronary artery disease: fatty plaque narrows them, causing chest pain on exertion (angina).
Heart attack: a plaque breaks open and a clot suddenly blocks the artery.

How it is diagnosed

ECG and troponin for a heart attack; stress test, CT coronary angiography or a catheter angiogram to see narrowings.

Treatment

Medicines (aspirin, statins, blood-pressure control) and stopping smoking.
Angioplasty and stent through a catheter.
Bypass surgery (CABG) for several or complex blockages.

Clinical notes

Mitral valve surgery and ablation near the mitral annulus can injure it, because it runs in the groove right next to the annulus
Obtuse marginal branches are frequent targets for bypass grafts and stents

Anatomical variants

Anomalous origin from the right aortic sinus or the right coronary artery, passing behind the aorta: the commonest coronary anomaly and usually harmless
In left-dominant hearts it is large and reaches the crux; in right-dominant hearts it may end short, at the obtuse margin

Test yourself

Think of the answer, then tap the question to see it.

Why is circumflex artery occlusion called an «electrically silent» infarct?

The standard 12 leads see the posterolateral wall it supplies poorly.

How does a posterior myocardial infarction show on the standard ECG?

As a mirror image in V1–V3: ST depression with tall R waves; posterior leads V7–V9 confirm it.

In a left-dominant heart, why can circumflex occlusion cause an inferior infarct with AV block?

The circumflex then gives the posterior descending artery and the AV nodal artery.

Why can mitral valve surgery injure the circumflex artery?

It runs in the left atrioventricular groove right next to the mitral annulus.

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Educational information, not medical advice. For any symptom, see a health professional.

Its names

Official Latin (TA2): arteria circumflexa cordis TA2 4148
Official Spanish (DeCS): Arteria circunfleja del corazón DeCS D003331
English (TA2): Circumflex artery of heart
Also called: circumflex branch of left coronary artery · LCx

Sources: Terminologia Anatomica (TA2); DeCS; Anatomy, Thorax, Heart; Anatomy, Thorax, Sinoatrial Nodal Artery; 19.1 Heart Anatomy (OpenStax (Rice University), 2022) · adapted, CC BY 4.0.

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Representative model, for educational purposes only.

Circumflex artery highlighted on the Durgical 3D model