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Topic

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Oblique vein of left atrium

The oblique vein of the left atrium, also known as the vein of Marshall, is a small embryological remnant of the left superior vena cava that persists as a venous channel draining into the coronary sinus. It courses obliquely across the posterior wall of the left atrium, running between the left pulmonary veins and merging with the coronary sinus near its entrance into the right atrium.

Although small or absent in many adults, it has clinical relevance in electrophysiology as it is associated with a myocardial sleeve containing autonomic fibers that can contribute to atrial fibrillation triggers. It also serves as an anatomical landmark during catheter ablation and left atrial interventions.

Synonyms

  • Vein of Marshall

  • Oblique vein of Marshall

  • Left atrial oblique vein

Function

  • Vestigial remnant of the left common cardinal vein

  • Minor tributary of the coronary sinus (when present)

  • Provides an accessory pathway for venous drainage of the posterior left atrium

  • Important in atrial fibrillation pathophysiology due to its neural and venous connections

MRI Appearance

T1-weighted images:

  • Typically appears as a small signal void (black lumen) adjacent to the left atrial wall, when visible

  • Often too small to identify without high-resolution techniques

T2 Cine (Cardiac-gated):

  • Demonstrates the venous channel as a flow void coursing obliquely across the posterior LA wall

  • Provides dynamic visualization relative to atrial contraction and coronary sinus filling

T1 Post-Contrast (Gadolinium-enhanced):

  • Enhances as a small bright vascular channel draining into the coronary sinus

  • Helps confirm venous continuity and differentiate from small lymphatic or vascular variants

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

  • Using whole-heart 3D, respiratory-navigated, ECG-gated imaging, the oblique vein can be visualized as a tiny venous channel crossing the posterior LA

  • Particularly useful in patients where contrast is contraindicated

  • Valuable for pre-ablation anatomical mapping

MRA (Magnetic Resonance Angiography):

  • Contrast-enhanced MRA can depict the oblique vein as a small tributary entering the coronary sinus

  • Most helpful in research and advanced mapping of left atrial venous anatomy

CT Appearance

CT Coronary Angiography (CCTA):

  • Best modality for visualization of the oblique vein

  • Seen as a small enhancing venous channel coursing obliquely along the posterior left atrium into the coronary sinus

  • 3D reconstructions demonstrate relationships with the left atrium, pulmonary veins, and coronary sinus

  • Important for planning atrial fibrillation ablation and coronary sinus interventions

CT image

Oblique vein of left atrium anatomy CT axial image -img-00000-00000

MRI image

Oblique vein of left atrium mri axial image