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Topic

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Left atrial branch (coronary artery)

The left atrial branch is a small but important arterial branch that usually arises from the proximal left circumflex artery (LCx), a major branch of the left coronary artery (LCA). It courses posteriorly and superiorly toward the left atrial wall, providing arterial supply to the left atrium, including the atrial myocardium and, in some cases, the left atrial appendage.

Anatomical variations are common — in some individuals, multiple left atrial branches may arise, and occasionally they may originate directly from the left main coronary artery. These branches play an important role in atrial perfusion, conduction tissue supply, and are clinically relevant in atrial ischemia, atrial fibrillation ablation, and surgical planning.

Synonyms

  • Left atrial artery

  • Atrial branch of left circumflex artery

  • LCx atrial branch

Function

  • Provides oxygenated blood to the left atrial myocardium

  • Contributes to the perfusion of the left atrial appendage

  • Supports the atrial conduction system, including Bachmann’s bundle in some cases

  • Important for atrial viability during ischemia, surgery, or ablation therapy

Branches

  • Typically no major secondary branches — instead forms a network of small atrial arterial twigs that supply atrial myocardium

MRI Appearance

T2 Cine (Cardiac-gated):

  • Shows the left atrial wall perfusion territory as the endocardial border in motion

  • Indirectly demonstrates perfusion defects in the left atrial myocardium if ischemia or fibrosis is present

CT Appearance

CT Coronary Angiography (CCTA):

  • Provides clear visualization of the origin, course, and small branches of the left atrial artery

  • Contrast opacifies the lumen, highlighting its course along the left atrial wall

  • Identifies stenosis, anomalous origin, or small vessel involvement in ischemic disease

  • High-resolution multiplanar and 3D reconstructions are especially useful for atrial fibrillation ablation and surgical planning

CT images

Left atrial branch anatomy CT axial image -img-00000-00000

CT images

Left atrial branch anatomy CT axial image -img-00000-00000_00001