Venous Blood Supply to the Heart

The venous blood supply to the heart is a complex topic. Let’s try to simplify and learn the major points that can be asked in competitive exams like NEET-PG/FMGE. The following cardiac veins drain into the coronary sinus, which is at the posterior wall of the right atrium;

• Small cardiac vein (SCV)
• Great cardiac vein (GCV)
• Middle cardiac vein (MCV)

The Great Cardiac Vein(GCV) runs in the anterior interventricular groove (AIVG) with the anterior interventricular atrium (AIVA). The GCV goes circumferentially behind the heart to drain into the left end of the coronary sinus at the posterior in the coronary sulcus. The SCV drains the blood into the coronary sinus on the posterior to the heart. The SCV is the continuation of the right-sided marginal vein.

The MCV runs in the posterior interventricular groove (PIVG) with the posterior interventricular atrium (PIVA). The Middle cardiac vein (MCV) drains into the coronary sinus, which drains at the posterior wall of the right atrium.

Some veins that don't drain into the cardiac sinus are Anterior cardiac veins, which Drain directly into the anterior wall of the right atrium. The coronary sinus receives the drainage from

• From the right side through SCV
• From the left side through GCV. GCV runs anteriorly and comes posterior later.

The GCV runs in the anterior interventricular groove (AIVG) with the anterior interventricular atrium (AIVA) and goes circumferentially behind the heart to drain into the left end of the coronary sinus at the posterior in the coronary sulcus. From P-IVG/ P-IVA through MCV

Coronary sinus in the posterior part of the coronary sulcus. Opens into the posterior wall of the right atrium

In the posterior view of the heart, The coronary sulcus, also known as the AV Groove, separates the atria from the ventricles.

• The left side has the Left coronary sulcus or the left AV groove, which separates the left atrium and ventricle.
• The right side has the Right coronary sulcus or the right AV groove, which Separates the right atrium and ventricle.

Atria are superior, and ventricles are inferior. The Interatrial septum divides the left and right atrium.

• 4 pulmonary veins open to the left atrium.
• 3 openings are seen in the right atrium. They are the superior vena cava, Inferior vena cava, and Coronary sinus.

The coronary sinus at the coronary sulcus posteriorly receives the heart's venous blood and drains to the posterior wall of the right atrium. Both the atria form the base of the heart or the posterior surface of the heart. The Major contribution is from the Left atrium, and the Minor contribution is from the right atrium. The interventricular septum separates the right ventricle from the left ventricle. Left and right ventricles form the inferior diaphragmatic surface, as they're related to the diaphragm. 

The posterior interventricular groove with the posterior interventricular artery (P-IVG with P—IVA) is present on the interventricular septum. The artery supplies the posterior ⅓rd of IVS, which means P—IVA at P-IVG supplies the posterior ⅓rd of IVS.

• GCV: Comes from the left side into the left coronary sulcus and enters the left end of the coronary sinus.
• SCV: Comes from the right side and drains into the right end of the coronary sulcus.
• MCV: Draining in the posterior view of the heart in the posterior interventricular groove (P-IVG) with posterior interventricular atrium (P-IVA) and drains into the coronary sinus.

The coronary sinus receives all the blood and drains into the posterior wall of the right atrium.

Frequently Asked Questions

Q. The Great cardiac vein lies in which groove

1. The anterior part of the right coronary sulcus
2. Posterior part of the right coronary sulcus
3. Anterior interventricular groove
4. Posterior interventricular groove

Answer:  Anterior interventricular groove

Explanation

• GCV is seen on both the anterior and posterior sides of the heart.
  • Posterior side - Runs at the left part of the coronary sulcus.
  • Anterior side - Runs in the anterior interventricular groove (AIVG) along with the anterior interventricular atrium (AIVA).
  • After that, GCV enters the left coronary sulcus and goes behind the heart to drain into the coronary sinus.
• MCV - Accompanying P-IVA in P-IVG and drains into the coronary sinus.

Q. Bleeding comes from the vein that is accompanied by the posterior interventricular artery. Which of the following veins is most likely to be ruptured

1. Great cardiac vein
2. Middle cardiac vein
3. Small cardiac vein
4. Oblique veins of the left atrium

Answer: Middle cardiac vein

Explanation

• MCV - Accompanying P-IVA in P-IVG and drains into the coronary sinus.

Q: How many pulmonary veins open to the left atrium?

Answer: 4 pulmonary veins open in the left atrium. 

Q: The following cardiac veins drain into the coronary sinus except:

1. Small cardiac vein
2. Great cardiac vein
3. Middle cardiac vein
4. Oblique veins of the atrium

Answer: Oblique veins of the atrium

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