The Anatomy of the Coronary Sinus

A group of veins that collect blood from the heart

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The coronary sinus is a large vein that that returns deoxygenated blood from the heart muscle to the right side of the heart so that it can be replenished with oxygen.

The coronary sinus is located on the heart’s posterior (behind) surface and is positioned between the left ventricle and the left atrium. All mammals, including humans, are known to have a coronary sinus.

Close look at the heart

Rasi Bhadramani / Getty Images


The length of the coronary sinus is from 15 to 65 millimeters (0.59 to 2.5 inches). It is wider than most of the coronary veins of the heart,


The coronary sinus is formed by several smaller veins that feed into it. It is located in the posterior (back) surface of the heart, in the groove between the left atrium and left ventricle.

The coronary veins that feed the coronary sinus are located in the thick layer of muscle in the heart, called the myocardium.

Anatomical Variations

A congenital defect (present at birth) of the coronary sinus, the cardiac total anomalous pulmonary venous return. (TAPVR), is a birth defect that causes a baby’s oxygenated blood to be delivered to the wrong side of the heart.

With this defect, the pulmonary veins (which should deliver oxygenated blood to the left atrium to eventually be pumped throughout the body), mistakenly connect to the right atrium (which normally receives deoxygenated blood from the body). The result is inadequate oxygen supply to the baby’s cells, organs, and tissues. 

Defect Involving the Coronary Sinus

If a baby is born with TAPVR, the coronary sinus mistakenly helps connect the pulmonary veins to the right atrium instead of the left atrium.


The coronary sinus collects what is called cardiac venous blood. This means it collects blood that needs to be reoxygenated from the coronary (heart) veins.

The function of the coronary sinus is to receive deoxygenated blood from the epicardial ventricular veins, which are the veins of the heart muscle. The coronary sinus delivers this blood to the right atrium before it eventually travels back to the lungs to be oxygenated again.

The epicardial ventricular veins include:

  • The great cardiac vein
  • The anterior interventricular veins
  • The left marginal vein
  • The posterior veins of the left ventricle
  • The posterior interventricular veins 

The right and left sides of the heart work together to effectively circulate oxygen-rich blood throughout the body. The oxygenated blood travels from the left ventricle to the aorta to smaller arteries, then to small vessels called capillaries to supply cells, tissues, and organs.

The deoxygenated blood of the body returns to the right atrium of the heart via the superior vena cava and inferior vena cava. The coronary sinus delivers deoxygenated blood from the heart muscle directly into the right atrium.

The heart/lung circulation continuously flows through the heart, lungs, and body.

Clinical Significance

When heart surgery is performed, it is common that the surgeon enacts a procedure called cardioplegia. This involves deliberately stopping the heart (temporarily) during a surgical heart procedure.

The delivery of cardioplegia through the coronary sinus has been proven effective and safe in myocardial protection. It has even been found to be a better method of cardioplegia than the traditional method, particularly for people who are having heart surgery for the treatment of coronary artery disease.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. The University of Minnesota. Atlas of human cardiac anatomy. Comparative anatomy tutorial.

  2. University of Minnesota. Atlas of human cardiac anatomy. Coronary sinus.

  3. Centers for Disease Control and Prevention. Facts about total anomalous pulmonary venous return (TAPVR).

  4. Cleveland Clinic. How does the blood flow through your heart?

  5. Gundry, S., Kirsh, M. A comparison of retrograde cardioplegia verses antegrade cardioplegia in the presence of coronary artery obstruction.

By Sherry Christiansen
Sherry Christiansen is a medical writer with a healthcare background. She has worked in the hospital setting and collaborated on Alzheimer's research.