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Topic

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Small cardiac vein

The small cardiac vein is one of the tributaries of the coronary venous system, draining the right atrium and right ventricle. It typically originates from the lower anterior surface of the right atrium and right ventricle, courses along the right margin of the heart within the coronary sulcus, and runs parallel to the right coronary artery (RCA).

It terminates by emptying into the coronary sinus, usually near the entry of the middle cardiac vein. In some individuals, the small cardiac vein may drain directly into the right atrium or be absent altogether.

The vein plays a role in venous return from the right border of the heart, complementing the drainage of the anterior cardiac veins and middle cardiac vein. Despite its small size and variable anatomy, it is clinically important in coronary venous mapping for cardiac resynchronization therapy (CRT), ablation, and venous interventions.

Synonyms

  • Right coronary vein

  • Vena cordis parva

  • Marginal cardiac vein

Function

  • Drains venous blood from the right atrium and right ventricle

  • Returns deoxygenated blood into the coronary sinus

  • Contributes to venous return from the right border of the heart

  • Acts as an anatomical guide in electrophysiology and device implantation

Tributaries

  • Small veins from the right atrium

  • Small veins from the right ventricle

  • Sometimes communicates with the anterior cardiac veins

MRI Appearance

T1-weighted images:

  • Appears as a tubular signal void (black lumen) coursing parallel to the RCA

  • Small size may make visualization difficult without contrast

T2-weighted images:

  • Flowing venous blood remains a signal void

  • Adjacent fat and myocardium provide contrast for localization

T1 Post-Contrast (Gadolinium-enhanced):

  • Enhances brightly and homogeneously with venous opacification

  • Improves visualization of its course and termination into the coronary sinus

  • Useful for MR venography of the coronary veins

MRA (Magnetic Resonance Angiography):

  • Contrast-enhanced MR venography demonstrates the small cardiac vein as a thin venous channel draining into the coronary sinus

  • Best assessed with cardiac-gated, 3D whole-heart sequences

  • Useful in mapping coronary venous anatomy before CRT lead placement

CT Appearance

Non-contrast CT:

  • Typically not visualized due to small caliber

  • Surrounding fat may outline its course faintly along the right coronary artery

CT Coronary Venography (CCTA):

  • With contrast, the small cardiac vein enhances as a thin venous channel paralleling the RCA and entering the coronary sinus

  • Multiplanar reconstructions improve detection of this small vessel

  • Valuable for pre-CRT planning, electrophysiology procedures, and coronary venous interventions

CT image

Small cardiac vein anatomy CT axial image -img-00000-00000

MRI image

Small cardiac vein mri axial image