Anatomy of the coronary circulation

Chapters:

Watch video only

Introduction0:00–0:35

Our hearts are responsible for sending blood throughout our body and bringing it back to our lungs in a constant exchange of oxygenated and deoxygenated blood.
Here at Osmosis, we also think your hearts are responsible for ‘starting with the heart’ and showing us love every time you watch one of our videos!
But remember, the heart itself also needs its own blood supply, called the coronary circulation, which it gets from the right and left coronary arteries.
The coronary arteries are embedded in fat, and course across the surface of the heart just deep to the epicardium. Let’s begin with the right coronary artery or RCA, which has its origin in the right aortic sinus and passes to the right side of the pulmonary trunk.

Right coronary artery0:35–1:39

Close to its origin, the RCA gives a sinoatrial nodal branch, which supplies the sinoatrial node. The RCA then descends in the coronary sulcus.
Along the way, it gives off the right marginal branch, which gets close to the apex, but doesn’t reach it and supplies the right border of the heart.
After giving this branch, the RCA turns to the left and continues its journey in the coronary sulcus posteriorly. Here, the RCA gives yet another branch, the atrioventricular nodal branch, which supplies the AV node.
The RCA usually gives the posterior interventricular branch which descends in the posterior interventricular groove. This branch supplies areas of both ventricles and sends perforating interventricular septal branches into the IV septum.
Finally, the terminal branch of the RCA continues for a short distance in the coronary sulcus. The left coronary artery or LCA originates from the left aortic sinus and passes between the left auricle and the left side of the pulmonary trunk and gets in the coronary sulcus.

Left coronary artery1:39–3:32

At the superior end of the anterior interventricular or IV groove, the LCA divides into two branches: the anterior interventricular or IV branch, sometimes called the left anterior descending or LAD and the circumflex branch.
The anterior IV branch passes through the anterior IV groove to the apex, where it turns around the inferior border of the heart and typically anastomoses with the posterior IV branch of the RCA.
The anterior IV branch supplies parts of both ventricles and the anterior two thirds of the interventricular septum through septal branches.
In many people, this branch gives rise to the lateral branch or diagonal artery which descends to the anterior surface of the heart.
Now, the circumflex artery runs in the coronary sulcus around the left border of the heart towards the posterior surface of the heart.
On its way, it gives the left marginal branch which also has many tiny branches that supply the left ventricle. Most commonly, the circumflex branch of the LCA terminates in the coronary sulcus on the posterior aspect of the heart prior to the crux of the heart.
Okay, to wrap things up, RCA supplies the diaphragmatic surface of the heart, the right atrium, most of the right ventricle, the diaphragmatic part of the left ventricle, and it usually also supplies the posterior third of the interventricular septum, the sinoatrial node and the AV node.
The LCA typically supplies: the left atrium, most of the left ventricle, part of the right ventricle, the anterior two thirds of the IVS, including the AV bundle, through perforating IV septal branches and the sinu-atrial node in some people.
And the reason for all the “somes” and “usuallys” is because there is something called dominance of the coronary arterial system, which refers to whether the right or left coronary artery gives off the posterior interventricular branch.

Dominance of the coronary arterial system3:32–5:09

In 67-85% of people, the right coronary artery gives rise to the posterior interventricular branch, so the most common distribution is the right dominant pattern.
In this case, the RCA and LCA are each in charge of about 50% of the heart supply. In about 8-15% of cases, LCA is dominant and the posterior IV branch comes from the circumflex artery.
In 7-18% of people, there is codominance and both RCA and LCA give rise to branches that run in or near the posterior IV groove.
And if you thought that all on its own made each of us special, think that some people might have just one coronary artery.
In others, the circumflex artery might have its origin in the right aortic sinus. 4% of people have an accessory coronary artery.
Finally, the RCA gives the sinu-atrial nodal branch 60% of the time and the AV branch 80% of the time, while LCA is responsible for the other scenarios.
That’s quite some variation! Even though the branches of the coronary arteries are considered to be functional end arteries, the heart does have the potential to develop collateral circulation.
This typically occurs between the termination of the right and left coronary arteries in the coronary sulcus between the IV branches near the apex in 10% of normal hearts, and can potentially develop for all hearts.

Venous drainage5:09–6:56

Alright, now, where there are arteries, there are veins. So there are heart veins that empty into the coronary sinus which drains into the right atrium, and some small veins that empty directly into the right atrium.
On a posterior view, you can see the main vein of the heart is the coronary sinus, which is a wide vein that runs from left to right in the posterior part of the coronary sulcus.
On its left side on the anterior surface, it receives the great cardiac vein, which is the main tributary of the coronary sinus and drains the areas supplied by the LCA.
The great cardiac vein begins as the anterior interventricular vein, near the apex of the heart, which accompanies the anterior IV branch of the LCA towards the coronary sulcus, then it turns left and this second part of the great cardiac vein runs around the left side of the heart with the circumflex branch of LCA to reach the coronary sinus.
Then there’s the oblique vein of the left atrium, also called the vein of Marshall, sadly not named after the loveable character from How I met your mother, which is a small vein that descends over the posterior wall of the left atrium and merges with the great cardiac vein to form the coronary sinus.
Let’s switch gears and look at some more veins on a posterior view of the heart. Here, the coronary sinus receives the middle cardiac vein which accompanies the posterior interventricular branch and the small cardiac vein, which accompanies the right marginal artery of RCA.
These two veins drain most of the areas supplied by RCA. The left posterior ventricular vein and the left marginal vein also open in the coronary sinus.
Some other veins begin over the anterior surface of the right ventricle, cross over the coronary sulcus and end directly in the right atrium or sometimes enter the small cardiac vein.
All right, as a quick recap, The heart receives arterial blood supply from the right and left coronary arteries and their branches, and venous blood is drained by the middle cardiac vein, the left marginal vein, as well as the left posterior ventricular vein, part of the small cardiac vein and the oblique vein of the left atrium.

Review6:56–8:12

Dominance of the heart refers to whether the right or left coronary artery gives off the posterior interventricular branch,where 67-85% of people are right coronary artery dominant.
On an anterior view, you can see some of the vessels that supply the heart, such as the RCA and its right marginal branch, a bit of the LCA and the whole anterior interventricular branch of LCA, as well as part of the circumflex artery.
You can also see the small cardiac vein following the right marginal branch, the anterior part of the great cardiac vein following the anterior interventricular branch and finally, a small part of the middle cardiac vein.
On a posterior view, you can see the left posterior ventricular vein, the posterior interventricular artery, the middle cardiac vein and the coronary sinus which collect